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CSA Z432-04 Machine Safeguarding

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Z432-04
Safeguarding of machinery
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CSA Standards Update Service
Z432-04
March 2004
Title: Safeguarding of machinery
Pagination: 147 pages (x preliminary and 137 text), each dated March 2004
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Z432-04
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ASSOCIATION CANADIENNE DE
NORMALISATION
BUREAU CENTRAL DE L’INFORMATION
5060, SPECTRUM WAY, BUREAU 100
MISSISSAUGA ON L4W 5N6
CANADA
CANADIAN STANDARDS
ASSOCIATION
CONSOLIDATED MAILING LIST
5060 SPECTRUM WAY, SUITE 100
MISSISSAUGA ON L4W 5N6
CANADA
CSA Standard
Z432-04
Safeguarding of machinery
Published in March 2004 by Canadian Standards Association
A not-for-profit private sector organization
5060 Spectrum Way, Suite 100, Mississauga, Ontario, Canada L4W 5N6
1-800-463-6727 • 416-747-4044
Visit our Online Store at www.csa.ca
ISBN 1-55397-481-6
Technical Editor: Dave Shanahan
© Canadian Standards Association — 2004
All rights reserved. No part of this publication may be reproduced in any form whatsoever
without the prior permission of the publisher.
© Canadian Standards Association
Safeguarding of machinery
Contents
Technical Committee on Safeguarding of Machinery viii
Preface x
0 Introduction 1
1 Scope 2
1.1
General 2
1.2
Exclusions 2
1.3
Purpose 2
1.4
Interaction with other standards 2
1.5
Terminology 2
1.6
Measurements 2
2 Reference publications 2
3 Definitions 5
4 Application 8
4.1
General 8
4.1.1
New machinery 8
4.1.2
Rebuilt or redeployed machinery 9
4.2
Strategy for selecting safety measures 9
4.2.1
General 9
4.2.2
Selection of safety measures 10
4.2.3
Phases of machine life 10
5 Risk
5.1
5.2
5.2.1
5.2.2
5.2.3
5.2.4
5.3
5.3.1
5.3.2
5.4
5.4.1
5.4.2
5.4.3
5.4.4
5.4.5
5.5
5.5.1
5.5.2
5.5.3
5.5.4
5.6
5.6.1
5.6.2
assessment and reduction 10
Risk assessment 10
Responsibilities for risk assessment and risk reduction 11
General approach 11
Manufacturer and user responsibilities 11
Design techniques hierarchy 11
User’s designs 12
Risk assessment methodology 12
Determining the limits of the machine or system 12
Affected personnel when identifying tasks and hazards 13
Identifying the hazards 15
General 15
Task identification 15
Associated hazards 15
Tasks 15
Similar risk assessment 15
Estimating the risk from the hazard 15
General 15
Severity of injury 16
Probability of injury 16
Overall risk estimation 17
Risk reduction 17
General 17
Eliminate the hazard or reduce the risk by design 17
March 2004
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Z432-04
5.6.3
5.6.4
5.6.5
5.6.6
5.6.7
5.6.8
5.6.9
5.7
5.7.1
5.7.2
5.7.3
5.7.4
© Canadian Standards Association
Apply safeguards 17
Implement administrative controls or other protective measures 18
Example 18
Disabling safeguards 19
New tasks 19
Modifications 19
Achievement of adequate risk reduction 19
Documentation 19
General 19
Manufacturer documentation 20
User documentation 20
Co-operation between manufacturer and user 20
6 Basic concepts and general safety considerations for design 20
6.1
Hazards to be considered when designing machinery 20
6.1.1
General 20
6.1.2
Using standardized measurement methods 20
6.1.3
Mechanical hazards 21
6.1.4
Other hazards 22
6.1.5
Linking mechanical and non-mechanical hazards 23
6.1.6
Strategies for reducing risk 24
6.2
Technical principles 24
6.2.1
Intrinsic design measures 24
6.2.2
Safeguarding and complementary protective measures 34
6.2.3
Requirements for design and construction of guards and protective devices 38
6.2.4
Information for use 42
6.2.5
Complementary protective measures 46
7 Mechanical design and controls 49
7.1
General 49
7.2
Mechanical restraint device 49
7.3
Down-stroking platens 49
7.4
Particular measures for repetitive-cycle hand-fed machines 49
7.4.1
General 49
7.4.2
Random stop machines 49
7.5
Rotating shafts, spindles, and couplings 50
7.6
Hydraulic and pneumatic systems 50
7.7
Electrical systems 50
7.8
Workholding devices 50
7.8.1
Energy loss during operation 50
7.8.2
Clamping for automatic machinery 50
7.8.3
Prevention of inadvertent unclamping of the workpiece 50
7.9
Lifting, handling, and transport 50
7.10
Lubrication 51
7.11
Hygiene 51
7.12
Safety colours and symbols 51
7.13
Operating stations 51
7.14
Platforms and steps 52
7.15
Access for adjustment, lubrication, and maintenance 52
7.16
Interlocking of pneumatic and hydraulic systems 53
7.17
Emergency stop 53
7.17.1 General 53
7.17.2 Emergency stop device design 53
7.17.3 Emergency stop pull-cords 53
7.18
Cables and pipes 54
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March 2004
© Canadian Standards Association
7.19
7.20
7.21
7.22
7.23
7.23.1
7.23.2
7.23.3
7.23.4
7.24
7.25
7.26
7.27
7.27.1
7.27.2
7.27.3
7.28
7.29
7.30
Safeguarding of machinery
Lighting 54
Interaction with other machinery 54
Coolant and swarf 54
Electromagnetic interference 54
Controls for machinery setting or adjustment and for feeding material where safeguards are
displaced or removed 55
General 55
Hold-to-run control 55
Enabling devices 55
Limited movement devices 56
Safeguard-operator interface principles 56
Warning signals 56
Indicators 57
Braking systems 57
General 57
Mechanical (friction) braking systems 57
Electrodynamic braking systems 58
Clutches 59
Safety catches, overrun, runback, and fall-back protection devices 59
Counterweights and similar devices 59
8 Performance requirements for safety control systems 59
8.1
General 59
8.2
Safety control system performance criteria 60
8.2.1
General 60
8.2.2
Simple 60
8.2.3
Single channel 60
8.2.4
Single channel with monitoring 60
8.2.5
Control reliable 60
8.3
Safety-related software- and firmware-based controllers 61
8.4
Control comparison (ANSI vs CEN) 61
9 Performance requirements for safeguarding devices 61
9.1
General 61
9.2
Barrier guards, fixed and interlocked 62
9.3
Interlocking safeguarding devices 62
9.3.1
General 62
9.3.2
Mechanical devices 62
9.3.3
Electrical devices 62
9.4
Requirements for other safeguarding devices that signal a stop 63
9.4.1
General 63
9.4.2
Safety light curtains/screens 63
9.4.3
Area scanning safeguarding devices 63
9.4.4
Radio frequency (RF)/capacitance safeguarding devices 63
9.4.5
Safety mat systems 64
9.4.6
Single and multiple beam safety systems 64
9.4.7
Two-hand control systems 64
10 Application requirements for safeguarding devices 65
10.1
General 65
10.2
Barrier guards, fixed and interlocked 65
10.2.1 General 65
10.2.2 Barrier guards, interlocked 65
10.2.3 Guard (barrier) portion 65
10.2.4 Interlocking portion 65
March 2004
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Z432-04
10.3
10.4
10.5
10.6
10.7
10.8
10.9
10.10
10.10.1
10.10.2
10.10.3
10.11
© Canadian Standards Association
Requirements for other safeguarding devices that signal a stop 66
Safety light curtains/screens 66
Area scanning safeguarding devices 67
Radio Frequency (RF)/capacitance safeguarding devices 67
Safety mat systems 67
Single and multiple beam safety systems 68
Two-hand control systems 68
Operator restraint devices 69
General 69
Pull-back device (or pull-out device) 69
Hold-back (hold-out or fixed restraining) device 70
Safeguarding device safety distance 70
11 Lasers 73
12 Ergonomics 73
12.1
General 73
12.2
Body sizes and shapes 74
12.3
Adjustable features 74
12.4
Working postures 74
12.5
Visual considerations 74
12.6
Physical effort 74
12.6.1 Exerted muscle force 74
12.6.2 Maximum force and/or speed 74
12.7
Machine pace 74
12.8
Displays 75
12.8.1 Indicators, dials, and displays 75
12.8.2 Analog displays 75
12.9
Controls 75
12.10 Foot-operated controls 76
13 Environmental considerations 77
13.1
Hygiene and guard design 77
13.2
Electromagnetic interference 77
13.3
Moving parts of machinery 77
14 Maintenance 77
14.1
Access to machinery for maintenance 77
14.2
Operational maintenance of safeguards 78
14.3
Waste and spillage removal 78
14.4
User responsibility 78
15 Safe work practices 79
15.1
General 79
15.2
Work practices 79
15.2.1 General 79
15.2.2 Practices for working machinery 79
16 Supervisory control 81
16.1
General 81
16.2
Permit-to-work systems 81
17 Information and communication 82
17.1
General 82
17.2
Instruction placards and warning labels 82
vi
March 2004
© Canadian Standards Association
17.3
Safeguarding of machinery
Installation, operation, and maintenance instructions 82
18 Training 83
18.1
General 83
18.2
Training procedures 83
18.2.1 Machinery operators 83
18.2.2 Plant engineers and maintenance staff 83
18.3
Personal protection 83
Annexes
A (informative)
B (informative)
C (informative)
D (informative)
—
—
—
—
Hazards, controls, and interlocks 84
Illustrations of other hazard controls 103
Ergonomic data 128
Selection of interlocking systems 136
Tables
1 — Hierarchy of safeguarding controls 12
2 — Safeguarding selection matrix 19
3 — Minimum distance from hazard as a function of barrier opening size* 71
4 — Recommended ergonomics control parameters 76
Figures
1 — Flow of responsibilities 1
2 — Schematic representation of the risk assessment/reduction process model 14
3 — Guidelines to help make the choice of safeguards against hazards generated by moving parts 35
4 — Optical PSSD: Minimum object sensitivity 68
5 — Graphical illustration of Table 3 72
March 2004
vii
Z432-04
© Canadian Standards Association
Technical Committee on
Safeguarding of Machinery
T. Eastwood
NCC Electronics,
Cambridge, Ontario
Chair
C. Newton
Dominion Power Press Equipment Limited,
Burlington, Ontario
Vice-Chair
B. Arger
Banner Engineering Corp.,
Orangeville, Ontario
D. Boone
Canadian Auto Workers,
Toronto, Ontario
B. Bouckley
General Motors Corporation,
Warren, Michigan, USA
Associate
R. Bourbonnière
Institut de recherche en santé et en
sécurité du travail du Québec,
Montréal, Québec
Associate
W. Brigger
Dominion Power Press Equipment Limited,
Burlington, Ontario
Associate
B. Byrne
Cross Huller-North America,
Sterling Heights, Michigan, USA
A. Chim
Takson Engineering Inc.,
Toronto, Ontario
R. Estok
Stelco Inc.,
Hamilton, Ontario
J. Hansen
Canadian Auto Workers,
Windsor, Ontario
G. Hildebrand
Manitoba Department of Labour
and Immigration,
Winnipeg, Manitoba
N. Hutchison
USWA National Office,
Toronto, Ontario
J. Locicero
Co-Ex-Tec Industries,
Concord, Ontario
G.F. Mansour
Ontario Ministry of Labour,
Toronto, Ontario
A. Martin
Dofasco Inc.,
Hamilton, Ontario
viii
March 2004
© Canadian Standards Association
Safeguarding of machinery
S. Massé
Institut de recherche en santé et en sécurité
du travail du Québec,
Montréal, Québec
G. McCaughey
University of Manitoba,
Winnipeg, Manitoba
B. McGillion
General Motors of Canada Limited,
St. Catharines, Ontario
W. McMahon
Auscan Consultants,
Burlington, Ontario
J.W. Mitchell
Stantec Consulting Ltd.,
Windsor, Ontario
J. Murphy
Vickers Warnick Limited,
Stoney Creek, Ontario
T. Norton
Absolute Engineering Solutions Inc.,
Kitchener, Ontario
R.F. Pfeiffer
Karmax Heavy Stamping,
Milton, Ontario
Associate
A. Pietrzyk
Rockwell Automation Inc./Allen-Bradley,
Mayfield Heights, Ohio, USA
Associate
M. Ruelle
Workers’ Compensation Board of BC,
Surrey, British Columbia
W. Schilke
Ontario Ministry of Labour,
Ottawa, Ontario
Associate
T. Schimek
Dofasco Inc.,
Hamilton, Ontario
Associate
R.J. Sitarz
Daimler Chrysler Canada Inc.,
Windsor, Ontario
Associate
J. Van Kessel
JVK Industrial Automation,
Cambridge, Ontario
M.P. Whitson
Industrial Accident Prevention Association,
Toronto, Ontario
R.A. Zobolotny
Industrial Accident Prevention Association,
Toronto, Ontario
D. Shanahan
CSA,
Mississauga, Ontario
March 2004
Associate
Associate
Project Manager
ix
Z432-04
© Canadian Standards Association
Preface
This is the second edition of CSA Z432, Safeguarding of machinery. It supersedes the previous edition
published in 1994.
This Standard specifies requirements for the design, manufacture (including remanufacture and
rebuilding), installation, maintenance, operation, and safeguarding of industrial equipment to
prevent injuries and accidents and enhance the safety of personnel who operate, assemble, and
maintain machinery.
The scope of this new edition has been expanded to incorporate new international Standards on
machinery design and performance and to provide additional information for the identification of hazards,
including non-mechanical hazard(s). It contains the methodology for performing a comprehensive risk
assessment. As indicated in Clause 4, this Standard is intended to be applied to newly manufactured,
rebuilt, and redeployed machinery. However, it could also be used to set upgrade targets for existing
machinery. This Standard provides advice on the basic principles of safeguarding and safety control
performance to the extent that a manufacturing engineer, plant engineer, manager, or safety personnel
may be able to interpret the advice and apply it to any particular machinery. Additional illustrations are
used to demonstrate the general application of these principles, although alternative safeguarding
solutions may be equally effective.
The need for a new edition was prompted by the changing technology related to these machines
and the wish of stakeholders, including regulators, employers, manufacturers, and labour, for a
document that would reflect the latest thinking concerning operator and equipment safety. It was
the intent of the Technical Committee to harmonize, where possible and where appropriate, with
international Standards. For that reason, parts of this Standard are based on the following international
Standards: ISO 12100 Parts 1 and 2, ISO 14121, ANSI B11 TR3, and BSI PD 5304.
This Standard was prepared by the Technical Committee on Safeguarding of Machinery, under the
jurisdiction of the Strategic Steering Committee on Occupational Health and Safety, and has been
formally approved by the Technical Committee. It will be submitted to the Standards Council of
Canada for approval as a National Standard of Canada.
March 2004
Notes:
(1) Use of the singular does not exclude the plural (and vice versa) when the sense allows.
(2) Although the intended primary application of this Standard is stated in its Scope, it is important to note that it remains
the responsibility of the users of the Standard to judge its suitability for their particular purpose.
(3) This publication was developed by consensus, which is defined by CSA Policy governing standardization — Code of
good practice for standardization as “substantial agreement. Consensus implies much more than a simple majority,
but not necessarily unanimity”. It is consistent with this definition that a member may be included in the Technical
Committee list and yet not be in full agreement with all clauses of this publication.
(4) CSA Standards are subject to periodic review, and suggestions for their improvement will be referred to the appropriate
committee.
(5) All enquiries regarding this Standard, including requests for interpretation, should be addressed to Canadian Standards
Association, 5060 Spectrum Way, Suite 100, Mississauga, Ontario, Canada L4W 5N6.
Requests for interpretation should
(a) define the problem, making reference to the specific clause, and, where appropriate, include an illustrative sketch;
(b) provide an explanation of circumstances surrounding the actual field condition; and
(c) be phrased where possible to permit a specific “yes” or “no” answer.
Committee interpretations are processed in accordance with the CSA Directives and guidelines governing
standardization and are published in CSA’s periodical Info Update, which is available on the CSA Web site at
www.csa.ca.
x
March 2004
© Canadian Standards Association
Safeguarding of machinery
Z432-04
Safeguarding of machinery
0 Introduction
This Standard assigns responsibilities for machinery safety to manufacturers, integrators, installers, and the
user. Proper safeguarding of personnel is determined utilizing the methodology in Clause 5, Risk
assessment and reduction. The Standard is best read in its entirety for full comprehension of requirements.
Figure 1 gives a graphic presentation of the flow of responsibilities as outlined in the Standard.
Clause 1 — Scope, exclusions, purpose, interaction
Clause 2 — Reference publications
Clause 3 — Definitions
Clause 4
Application, selecting safety measures,
phases of machine life
Clause 5
Identification of hazards:
Risk assessment and reduction
Clauses 8 and 9
Performance requirements for safety control
systems and safeguarding devices
Clause 6
Basic concepts and general safety
considerations for design
Clause 7
Mechanical design
application
Clause 10
Application requirements
for safeguarding devices
Clause 11
Special consideration
for lasers
Clauses 12 and 13
Ergonomic and environmental
considerations
Clause 14
Maintenance
Clauses 15, 16, 17, 18
Safe work practices, supervision, information, and training
Figure 1
Flow of responsibilities
(See Clause 0.)
March 2004
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Z432-04
© Canadian Standards Association
1 Scope
1.1 General
This Standard applies to the protection of persons from the hazards arising from the use of mobile or
stationary machinery. It provides the criteria to be observed and the description, selection, and application
of guards and safety devices. Where a current CSA Standard exists for a specific type of machinery
(e.g., CAN/CSA-B167, CAN/CSA-B354.2, CAN/CSA-M424.1, Z142, Z248, and CAN/CSA-Z434), it is to be
used in conjunction with this Standard to provide the most effective protection to the particular situation.
1.2 Exclusions
This Standard does not apply to portable hand tools.
1.3 Purpose
This Standard is intended for those who design, build, modify, install, use, operate, or maintain machinery,
machinery guarding, or safety devices. It is also intended to be used by those concerned with information,
instruction, and training in safe working practices.
1.4 Interaction with other standards
Machinery safeguarding is not performed in isolation from other protective measures. Typically, industrial
machinery is installed in workplaces where other associated activities take place (e.g., movement of
materials, cables, pipes, and hoses supplying power, gases, and liquids, and workers on foot and operating
vehicles). Other machinery and work environment standards applicable to any place where this Standard
is being implemented should therefore be reviewed.
1.5 Terminology
In CSA Standards, “shall” is used to express a requirement, i.e., a provision that the user is obliged to
satisfy in order to comply with the standard; “should” is used to express a recommendation or that which
is advised but not required; and “may” is used to express an option or that which is permissible within the
limits of the standard. Notes accompanying clauses do not include requirements or alternative
requirements; the purpose of a note accompanying a clause is to separate from the text explanatory or
informative material. Notes to tables and figures are considered part of the table or figure and may be
written as requirements. Legends to equations and figures are considered requirements.
1.6 Measurements
The values given in SI (metric) units are the standard. The values given in parentheses are for
information only.
2 Reference publications
This Standard refers to the following publications, and where such reference is made, it shall be to the
edition listed below.
CSA (Canadian Standards Association)
CAN/CSA-B167-96 (R2002)
Safety Standard for Maintenance and Inspection of Overhead Cranes, Gantry Cranes, Monorails, Hoists, and
Trolleys
CAN/CSA-B354.2-01
Self-Propelled Elevating Work Platforms
C22.1-02
Canadian Electrical Code, Part I
2
March 2004
© Canadian Standards Association
Safeguarding of machinery
CAN/CSA-C22.2 No. 0-M91 (R2001)
General Requirements — Canadian Electrical Code, Part II
CAN/CSA-C108.6-M91 (R2003)
Limits and Methods of Measurement of Electromagnetic Disturbance Characteristics of Industrial, Scientific
and Medical (ISM) Radio-Frequency Equipment
CAN/CSA-M424.1-88 (R2000)
Flameproof Non-rail-bound Diesel-Powered Machines for Use in Gassy Underground Coal Mines
CAN/CSA-Z94.1-92 (R2003)
Industrial Protective Headwear
Z94.2-02
Hearing Protective Devices — Performance, Selection, Care, and Use
CAN/CSA-Z94.3-02
Eye and Face Protectors
Z94.4-02
Selection, Use, and Care of Respirators
Z107.56-94 (R1999)
Procedures for the Measurement of Occupational Noise Exposure
CAN/CSA-Z107.58-02
Noise Emission Declarations for Machinery
Z142-02
Code for Power Press Operation: Health, Safety, and Guarding Requirements
CAN/CSA-Z195-02
Protective Footwear
Z248-04
Code for Tower Cranes
Z259 series of Standards
CSA Standards on Fall Protection Equipment
CAN/CSA-Z321-96 (R2001)
Signs and Symbols for the Workplace
CAN/CSA-Z431-02
Basic and safety principles for man-machine interface, marking and identification — Coding principles for
indication devices and actuators
CAN/CSA-Z434-03
Industrial Robots and Robot Systems — General Safety Requirements
ANSI (American National Standards Institute)
B11 TR3-2000
Risk Assessment and Risk Reduction — A Guide to Estimate, Evaluate and Reduce Risks Associated with
Machine Tools
March 2004
3
Z432-04
© Canadian Standards Association
Z136.1-2000
Safe Use of Lasers
BSI (British Standards Institute)
PD 5304:2000
Safe Use of Machinery
Government of Canada
Nuclear Safety and Control Act, S.C. 1997, c. 9
IEC (International Electrotechnical Commission)
60825-1:2001
Safety of laser products — Part 1: Equipment classification, requirements and users’ guide
61496-1:2004
Safety of machinery — Electrosensitive protective equipment — Part 1: General requirements and tests
61496-2:1997
Safety of machinery — Electrosensitive protective equipment — Part 2: Particular requirements for equipment
using active opto-electronic devices (AOPDs)
61496-3:2001
Safety of machinery — Electrosensitive protective equipment — Part 3: Particular requirements for active
opto-electronic protective devices responsive to diffuse reflection (AOPDDR)
ISO (International Organization for Standardization)
12100-1:2003
Safety of machinery — Basic concepts, general principles for design — Part 1: Basic terminology, methodology
12100-2:2003
Safety of machinery — Basic concepts, general principles for design — Part 2: Technical principles
13849-1:1999
Safety of machinery — Safety-related parts of control systems — Part 1: General principles for design
13850:1996
Safety of machinery — Emergency stop equipment — Principles for design
13852-1:1996
Safety of machinery — Safety distances to prevent danger zones being reached by the upper limbs
13856-1:2001
Safety of machinery — Pressure-sensitive protective devices — Part 1: General principles for design and testing
of pressure-sensitive mats and pressure-sensitive floors
14121:1999
Safety of machinery — Principles of risk assessment
NFPA (National Fire Protection Association)
79-2002
Electrical Standard for Industrial Machinery
4
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Safeguarding of machinery
3 Definitions
The following definitions apply in this Standard:
Active opto-electronic protective device (AOPD) — a device that senses the presence of objects
in a specified detection zone through the function of opto-electronic emitting and receiving elements
detecting the interruption of optical radiations generated within the device (e.g., beams of light
traversing the detection zone).
Adequate risk reduction — the achievement of a risk level unlikely to give rise to a situation that
could result in harm to any person.
Assembly of machines — a group of machines working together in a coordinated manner.
At height — access positions located 2.5 m above the surrounding surface or landing.
Blanking — bypassing a portion of the sensing field of a presence-sensing safeguarding device.
Common cause failures — failures of different items, resulting from a single event, where these failures
are not consequences of each other.
Common mode failures — failures of items characterized by the same fault mode.
Critical safety function — a safety function of a machine whose failure can result in an immediate
increase of risk.
Danger zone — the zone around the machine (front, back, sides, top, and bottom) where a hazard
is created by the motion of the machine components.
Electro-sensitive protective device (ESPD) — a device or assembly of devices that provide protection
through the function of electronic sensors, controls/monitors, and output signal switching components.
An AOPD is one such device.
Emergency situation — an immediately hazardous situation that needs to be ended or averted quickly
in order to prevent injury or damage.
Emergency stop — a function that is intended to avert harm or to reduce existing hazards to persons,
machinery, or work in progress.
Emergency stop button — a red mushroom-headed button that, when activated, will immediately
start the emergency stop sequence.
Emission value — a numerical value quantifying an emission generated by a machine (e.g., noise,
vibration, hazardous substances, radiation).
Note: Emission values are basic data, measured in accordance with standardized methods, for the assessment of the risk
associated with emissions.
Enabling device — a device that is designed to initiate a machine action or allow the flow of energy
to a machine.
Failure to danger — any failure of the machinery or its associated safeguards, control circuits, or energy
source power that generates a hazardous situation.
Guard — a part of machinery specifically used to provide protection by means of a physical barrier.
Depending on its construction, a guard may be called a casing, screen, door, enclosing guard, etc.
Adjustable barrier guard — a fixed guard that is adjustable as a whole or that incorporates
adjustable parts. The adjustment to the guard remains fixed during operation.
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Barrier (fixed distance) guard — a fixed guard that does not completely enclose the hazard
but that reduces access by virtue of its physical dimensions and its distance from the hazard.
Fixed guard — a guard kept in place (i.e., closed or attached to a fixed surface) either permanently
(e.g., by welding) or by means of fasteners (screws, nuts, etc.), making removal or opening
impossible without using tools.
Interlocked barrier guard — a fixed or movable guard attached and interlocked in such a manner
that the machine tool will not cycle or will not continue to cycle unless the guard itself or its hinged
or movable section encloses the hazardous area.
Movable guard — a guard generally connected by mechanical means (e.g., hinges or slides)
to the machine frame or an adjacent fixed element and that can be opened without the use of
tools. The opening and closing of this type of guard may be powered.
Guard locking device — a device that is designed to hold the guard closed and locked until the
hazard has ceased.
Harm — physical injury or damage to health.
Hazard — a potential source of harm to a person.
Relevant hazard — a hazard that is identified as being present at or associated with the machine.
Significant hazard — a hazard that has been identified as relevant and that requires specific action
by the designer to eliminate or to reduce the risk according to the risk assessment.
Hazardous situation — a set of circumstances that may give rise to harm to a person.
Hold-back (out) or restraint device — a device, including attachments for each of the operator’s
hands or wrists or for his/her body, that prevents the operator from reaching into the danger zone during
each cycle of the machine.
Hold-to-run control device — a control device that is designed to permit movement of machinery as
long as the control is held in a set position. Once released, this device automatically returns the machine
to the stop position.
Information for use — a protective measure consisting of communication links (e.g., texts, words,
signs, signals, symbols, diagrams) used separately or in combination to convey information to the user.
Inherently safe design — a machine design that incorporates protective measures that either eliminate
hazards or reduce the risks associated with hazards by changing the design or operating characteristics of
the machine without the use of guards or protective devices.
Integrity — the ability of a machine, components, devices, systems, and procedures to perform a
required function under specified conditions and for a given period of time reliably and without defeat.
Intended use (of a machine) — use of a machine in accordance with the information provided in the
instructions for use.
Interlocking device (interlock) — a mechanical, electrical, or other type of device, the purpose of
which is to prevent the operation of machine elements under specified conditions (usually when the guard
is not closed).
Limited movement control device — a device that restricts the direction, distance, rotation,
or orientation of movement of machinery components.
Limiting device — a device that restricts the power, movement, or speed of machinery components.
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Lockout — a procedure that disconnects, blocks, or bleeds of all sources of energy (electrical, pneumatic,
steam, hydraulics, mechanical, stored, or any other source of energy) that may create a motion or action
by any part of the machinery and/or its auxiliary equipment and places a lock on the disconnect device or
at the point of disconnect.
Machinery — an assembly of linked parts or components, at least one of which moves, with the
appropriate machine actuators, control and energy circuits, etc. joined together for a specific
application, in particular for the processing, treatment, moving, or packaging of a material.
Maintainability (of a machine) — the ability of a machine to be maintained in a state, or restored
to such a state, that enables it to fulfill its intended use, the necessary actions (maintenance) being carried
out according to specified means.
Manufacturer — an entity that designs, assembles, reconstructs, or modifies machines or systems.
Note: Under certain circumstances (i.e., acting as a builder, modifier, or integrator), the user may also be considered
as a manufacturer.
Mechanical restraint device — a device that is designed to hold back or pull back an individual
and/or machine component in order to ensure that the individual’s body cannot enter the danger zone
during the machine actuating sequence.
Operator — the person responsible for the operation (including operation during maintenance activities)
of a machine or component or a machine.
Presence-sensing device (PSD) — a safeguarding device designed and constructed to create a sensing
field that, when penetrated, produces a signal intended to stop hazardous machine motion within the
area protected by the field.
Protective device — any machine device that is designed to prevent or limit possible harm to a person.
Protective measure — a measure intended and implemented to achieve risk reduction.
Pull-back (pull-out) device — a device that is attached to the hands and wrists of the operator and
includes attachments for each of the operator’s hands to be used in place of the operator’s hands within
the danger zone.
Rebuilt machinery — machines that have been overhauled or restored.
Redeployed machinery — machines that have been relocated (i.e., moved to a different work site or
building).
Reliability (of a machine) — the ability of a machine or its components or equipment to perform
a required function under specified conditions and for a given period of time without failing.
Residual risk — risk remaining after protective measures have been taken.
Risk (of harm to an individual) — a combination of the probability and the degree of the possible injury
or damage to health in a hazardous situation.
Risk analysis — a combination of the determination of the limits of the machine, hazard
identification, and risk estimation.
Risk assessment — the overall process of risk analysis and risk evaluation.
Risk estimation — a judgment, on the basis of risk analysis, of whether adequate risk reduction has
been achieved.
Safe distance — a method of workpiece positioning and operator location that eliminates the need for
the operator to be in or near the hazardous area during the hazardous portion of the machine cycle.
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Safe opening — a method of safeguarding that limits the access to the hazardous area by the size of
the openings or by closing off access when the workpiece is in place in the machine tool.
Safe working practice — a safe system of work, i.e., a method of working that eliminates or reduces
the risk of injury.
Safeguard — a guard or safety device designed to protect persons from danger.
Safeguarding — safety measures consisting of the use of specific technical means, called safeguards
(guards, safety devices), to protect persons from hazards that cannot be reasonably removed or sufficiently
limited by design.
Safety device — a device other than a guard that eliminates or reduces risk, alone or associated with
a guard.
Safety function — a function of a machine whose failure can increase the risk of injury.
Scotch — a mechanical restraint device placed manually or automatically between two parts of
machinery and capable of preventing them from closing under gravity or energy.
Stopping time — the total time elapsed between the introduction of a stop command and the end
of hazardous motion.
Trip device — a mechanism that causes hazardous machine elements to stop (or ensures an otherwise
safe condition) when a person or a part of his/her body goes beyond a predetermined limit.
Trip devices can be
(a) mechanically actuated, e.g., trip wires, telescopic probes, pressure-sensitive devices; or
(b) non-mechanically actuated, e.g., opto-electronic devices, devices using capacitive or ultrasonic
means to achieve detection.
Two-hand control device — a device that requires the concurrent use of both of the operator’s hands
to both initiate and continue the machine cycle during the hazardous portion of the machine cycle.
Unintended/unexpected start-up — any start-up that, because of its unexpected nature, generates a
hazard (e.g., a start command resulting directly from a system failure, an external influence, or restoration
of power).
Use — any activity involving machinery, including starting, stopping, programming, setting, transporting,
repairing, modifying, maintaining, servicing, and cleaning.
User — an individual or company that purchases or uses the machine, system, or related equipment.
Note: Under certain circumstances (i.e., acting as a builder, modifier, or integrator), the user may also be considered as
a manufacturer.
Workpiece — any piece of material placed into the machine tool for the purpose of having work
performed upon it.
4 Application
4.1 General
4.1.1 New machinery
This Standard is intended to be applied to newly manufactured and newly installed machinery. The aim
of this Standard is to promote a high standard of machinery safety during use. The Standard describes
and illustrates a variety of safety measures and explains methods by which it is possible to assess which
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measure(s) it is reasonable to adopt in particular circumstances. As a minimum it will, however, be
necessary to consult specific legislation in applying the principles set down. Although reference is made to
specific types of machine, specific recommendations are not given for every type of machine.
4.1.2 Rebuilt or redeployed machinery
This Standard also applies to rebuilt or redeployed machinery. This does not preclude the addition of
safety enhancements to this Standard.
4.2 Strategy for selecting safety measures
4.2.1 General
4.2.1.1
The strategies for reducing risk of injury that shall be applied to hazards are as follows:
(a) identify the hazard(s) (see Clause 5.4);
(b) use risk assessment techniques to assess and document hazards (see Clause 5.5);
(c) eliminate the hazards by an inherently safe design (see Clauses 6 and 7); and
(d) limit the risk through
(i)
the use and selection of safeguards (see Clauses 8, 9, and 10);
(ii) consideration of interlock(s) and control methods (see Clause 9.3 and Annex A);
(iii) consideration of environmental, installation, and maintenance factors (see Clauses 12 to 14);
and
(iv) the use of safe working practices (see Clause 15).
4.2.1.2
Designers and manufacturers should assess all hazards associated with the normal operation and
maintenance of their machinery and take steps to eliminate risk of injury or reduce the scale of injury
that can be caused, e.g., by reducing speeds or forces.
4.2.1.3
Where machinery has been designed or modified without taking these hazards into consideration,
the identification and elimination of such hazards should be considered by the user. Modifications may
be possible which, although not capable of eliminating injury, reduce its scale. (Clause 6 refers to
identification of hazards and Clause 8 to measures to reduce and eliminate injury.)
4.2.1.4
When a hazard cannot be eliminated or avoided, other measures for reducing the risk of injury should
be sought. These measures may include reducing the scale of injury and providing safeguards and safe
working practices. The avoidance of injury depends on the reliability of these measures.
4.2.1.5
Unless a danger point or area is safe by virtue of its position, the machinery shall be provided with
safeguarding that eliminates or, where this is not practicable, reduces the risk.
4.2.1.6
It may be difficult to ensure that machinery is safe by virtue of its position and, where access and
consequent injury are reasonably foreseeable, safeguards shall be provided.
4.2.1.7
In considering the various measures to reduce risk, it is important to have a realistic assessment of all
the risks involved. See Clause 7.
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4.2.1.8
Certain safety measures are more reliable than others. The order of priority is determined by reliability
and therefore safeguards shall be considered before safe working practices. Safeguards are examined in
Clauses 10 to 13 and safe working practices in Clause 15.
4.2.1.9
In addition to measures undertaken explicitly for safety reasons, many other factors that may or may not
have been considered at the design stage influence the safe use of machinery. For the benefit of the user,
these are examined in Clauses 9, 14, and 16 to 18.
4.2.2 Selection of safety measures
When applying the strategy for the selection of safety measures, it may not be possible to use the more
effective types of safety measures because they are either not technically feasible or are unsuitable for their
particular application.
4.2.3 Phases of machine life
As far as possible, the user should consider hazards associated with all phases of machine life
(see Clause 5.4.4).
These hazards may give rise to conflicting requirements, and priority should be given to those phases
that give rise to the greatest risk. For example, for manually operated machines involving repetitious work
this is likely to be the operation phase, while for fully automated and/or remote-controlled machinery,
where there is no access during operation, the maintenance, toolsetting, and adjustment phases may
require greater emphasis. The aim is to minimize the total risk.
5 Risk assessment and reduction
5.1 Risk assessment
5.1.1
In this Standard, the purpose of a risk assessment is to evaluate the potential for injury or damage to health
under hazardous situations presented by machinery in order to select appropriate risk reduction methods
and monitor their effectiveness.
5.1.2
Risk assessments shall be carried out
(a) at the design stage on new, refurbished, rebuilt, or redeployed equipment; and
(b) whenever safety measures and/or configuration changes or modification to existing work
procedures, equipment, or materials would impact the safety of the user.
Risk assessments should be carried out jointly by the user, designer, manufacturer, integrators,
the workers and their representative and, whenever necessary, with the assistance of technical
specialists and occupational health professionals.
5.1.3
There are no fixed rules about how a risk assessment should be carried out; it will depend on the nature
of the work or business and the types of hazards and risks. However, whatever approach is taken, it is
important that it be practical, look at what actually happens in the workplace, and be undertaken
while the work activity is being performed (see Clause 5.3).
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5.2 Responsibilities for risk assessment and risk reduction
5.2.1 General approach
5.2.1.1
The co-operative efforts of manufacturers and users in risk assessment are necessary to attain the goal
of adequate risk reduction. Where the manufacturer cannot achieve adequate risk reduction, the user
shall apply additional protective measures. Effective communication between manufacturers and users is
recommended where possible, but the success of a risk assessment is not dependent on this relationship.
5.2.1.2
Risk assessment relies on the reasoned judgment and expertise of individuals familiar with the tasks
and hazards associated with machinery. Individuals or “professional discipline” biases can affect the
results; for example, an individual attuned to noise hazards may give considerable attention to noise issues
and not enough attention to other hazards. To minimize these biases, a team approach is recommended.
Although an individual may be responsible for drafting the analysis, a team of involved personnel —
operators, maintenance and engineering personnel — should participate in the risk assessment and
reduction effort.
5.2.2 Manufacturer and user responsibilities
The manufacturer and the user of the machine have risk assessment and risk reduction responsibilities.
When the manufacturer (or the manufacturer’s representative) is not available to participate in the risk
assessment for the machine, the user shall assume this responsibility.
5.2.3 Design techniques hierarchy
The manufacturer shall reduce risk through design techniques, safeguards, and information for use
following the order of precedent/hierarchy (see Table 1).
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Table 1
Hierarchy of safeguarding controls
(See Clause 5.2.3.)
Most effective
1. Elimination or substitution
•
•
•
eliminate human interaction in the process
eliminate pinch points (increase clearance)
automated material handling
2. Engineering controls
(safeguarding technology)
•
•
•
•
•
mechanical hard stops
barriers
interlocks
presence-sensing devices
two-hand controls
3. Awareness means
•
•
•
•
•
•
•
lights, beacons, and strobes
computer warnings
signs
restricted space painted on floor
beepers
horns
labels
4. Training and procedures
(administrative controls)
•
•
•
•
safe job procedures
safety equipment inspections
training
lockout
5. Personal protective equipment
•
•
•
•
safety glasses
ear plugs
face shields
gloves
Least effective
5.2.4 User’s designs
When the user designs, constructs, modifies, or reconstructs the machine, the user is considered to be
the manufacturer.
5.3 Risk assessment methodology
Note: A number of methodologies are available to do risk assessment. As stated in Clause 5.1.3, any method is acceptable
that is equivalent or more stringent than the method described in this clause.
5.3.1 Determining the limits of the machine or system
The risk assessment process begins with determining the limits of the machine or system as follows:
(a) use limits: determined, for example, by the production rates, cycle times, and intended use of
the machine, as well as the speed, forces, material to be used, and number of persons involved;
(b) space limits: for example, range of movement, space requirements for machine installation,
maintenance, and operator-machine interfaces;
(c) time limits: for example, maintenance and wear of tools, mechanical and electrical components,
fluids;
(d) environmental limits: for example, temperature, humidity, noise, location; and
(e) interface limits: for example, other machines or auxiliary equipment, energy sources.
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5.3.2 Affected personnel when identifying tasks and hazards
5.3.2.1 Information for risk assessment
The information for risk assessment should include, but may not be limited to, the following individuals:
(a) operators and helpers;
(b) maintenance individuals;
(c) engineers;
(d) technicians;
(e) sales personnel;
(f) installation and removal personnel;
(g) administrative personnel;
(h) trainees;
(i) passers-by;
(j) designers;
(k) managers;
(l) supervisors;
(m) safety personnel;
(n) safety committees;
(o) safety consultants; and
(p) loss control administrators.
5.3.2.2 Level of training, experience, or ability
The risk assessment shall take into account the
(a) level of training, experience, or ability of
(i)
operators;
(ii) helpers;
(iii) maintenance personnel;
(iv) technicians;
(v) trainees; and
(b) exposure of other persons to the hazards associated with the machine where it can be reasonably
foreseen.
5.3.2.3 Comparing similar hazardous situations
Comparisons between similar hazardous situations associated with different types of machines are often
possible, provided that sufficient information about hazards and accident circumstances in those situations
is available and pertinent.
5.3.2.4 Absence of an accident
The absence of an accident history, a small number of accidents, or the low severity of accidents shall not
be taken as an automatic presumption of a low risk.
5.3.2.5 Quantitative analysis
For quantitative analysis, information from sources such as databases, handbooks, laboratories, and
manufacturers’ specifications may be used, provided that there is confidence in the suitability of the data.
Uncertainty associated with this data shall be indicated in the documentation.
5.3.2.6 Expert opinion
Expert opinion can be used to supplement other data.
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Re-evaluate
machine limits
Start
Determination of the limits of the machinery
(Clause 5.3.1)
Risk assessment
Task and hazards identification
(Clause 5.4)
Risk estimation
(Clause 5.5)
Yes
Has
the risk been
adequately reduced?
(Clause 5.6.9)
Yes
Do other
task/hazard
combinations
exist?
No
Can
the hazard be
eliminated or
the risk be
reduced by
design?
Risk reduction
(Clause 5)
Yes
No
Risk reduction by
design
(Clause 5.6.2)
Documentation
(Clause 5.7)
No
Can
the risk be
reduced by
safeguarding,
protective
devices?
Yes
Risk reduction by
safeguarding,
protective device
(Clause 5.6.3)
END
No
Can the risk
be reduced by
administrative
controls or other
measures?
Yes
Risk reduction by
administrative
controls and other
protective measures
(Clause 5.6.4)
No
Figure 2
Schematic representation of the
risk assessment/reduction process model
(See Clause 5.6.1.)
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5.4 Identifying the hazards
5.4.1 General
Besides drawing on their own knowledge and experience, users should identify those aspects of their work
that have the potential to cause harm by looking at appropriate sources of information such as guidance
published by the regulator and manufacturer’s instructions. The knowledge and experience of the workforce
should also be considered.
5.4.2 Task identification
All tasks associated with the machine should be identified. Examples of task categories include, but are
not limited to,
(a) packing and transportation;
(b) unloading/unpacking;
(c) systems installation;
(d) start up/commissioning;
(e) assembly and trial run;
(f) operation (all modes);
(g) tool change;
(h) planned maintenance;
(i) unplanned maintenance;
(j) unjamming;
(k) major repair;
(l) recovery from crash;
(m) troubleshooting;
(n) housekeeping;
(o) decommissioning; and
(p) disposal.
5.4.3 Associated hazards
All hazards associated with the tasks shall be identified. Table A.1 gives examples to assist in this process.
5.4.4 Tasks
All tasks associated with the intended use and reasonably foreseeable misuse of the machine should be
identified. This shall include all phases in the lifecycle of the machine. Intended use includes consideration
of the manufacturer’s instructions for use. The intended use may be determined by the user.
5.4.5 Similar risk assessment
Information from risk assessments on similar machines may be used as a starting point when tasks and
hazards are comparable. Using this information does not eliminate the need to follow the risk assessment
process as described in this Standard for the specific conditions of use (e.g., when a shear used for cutting
plastic is compared with a shear used for cutting metal, the risks associated with the different material
should be assessed).
5.5 Estimating the risk from the hazard
5.5.1 General
5.5.1.1
Risk estimation shall account for all modes of operation.
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5.5.1.2
Risk estimation should include all work methods and situations (maintenance, assembly, diagnostics, etc.)
when it is necessary to suspend or modify one or more protective measures.
5.5.1.3
The estimation of risk determines to a large extent the safety to be undertaken. Two factors shall be taken
into account in such an estimation:
(a) the severity of foreseeable injuries; and
(b) the probability of their occurrence.
5.5.1.4
The extent and complexity of the assessment required can only be determined after an initial appraisal
of the risks and safety measures. Clauses 5.5.2 to 5.5.4 describe the underlying principles involved.
Note: Many of the formal methods as yet have limited application because of the lack of reliable data.
5.5.2 Severity of injury
5.5.2.1
The severity of possible injury has an important influence on the level of safety measures. Where two
machines present the same probability of injury, but in one case the injury is death and in the other
a bruised or broken finger, clearly the former carries the higher risk and requires a higher level of safety
precautions. Some types of injury, particularly those involving injury to health, are not immediately
apparent and may be manifested some time after exposure to a hazard has ceased. Other injuries build up
over a long period of exposure to a hazard.
5.5.2.2
Access to the hazard area may occur during all phases of machine life and for a variety of reasons,
either deliberate or accidental. The following questions should be asked to determine the possible
severity of injury:
(a) What type of mechanical or other hazard is involved?
(b) What type(s) of injury can be foreseen?
5.5.3 Probability of injury
5.5.3.1
When examining a machine either from the first principles or by making comparisons, account should
be taken of the frequency of access to or beyond a danger point during each phase of machine life,
e.g., machine operation and breakdown, commissioning, maintenance, setting, and process changeover.
By considering foreseeable human behaviour at each phase, the designer can assess the probable total
frequency of access to the danger points.
An estimate should then be made of the proportion of each type of access likely to be injurious.
This may require a reliability assessment of safety or other features as the potential severity of injury
may vary depending on the position of access.
5.5.3.2
It is emphasized that the absence of injury from machinery used without safeguards over a period of time
does not in itself mean that the machine is completely safe.
5.5.3.3
Limited accident statistics are available from various sources, e.g., large employers, employer
organizations, and trade unions. More extensive studies generally indicate accident frequency
only in terms of a rate for an industry as a whole over a period, without giving specific data on
machines or hours of exposure to risk.
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5.5.3.4
The available data have to be interpreted with extreme care. In individual cases, particularly with new
types of machinery, judgment of the level of probability of injury should still be based on individual
and collective experience of other machinery with similar modes of operation, maintenance, and so on.
5.5.4 Overall risk estimation
Risk is a combination of the potential severity of injury and the probability of the injury. For each hazard,
the total risk is the sum of the risks under all the different circumstances given in Clauses 5.5.1 to 5.5.3.
The overall risk from the use of a given machine is the sum of the risks from the various hazards. It is
often helpful for users to make an initial assessment (assuming that no safeguards are installed), to
eliminate from consideration those risks on which sufficient action has occurred and no further action is
needed. This procedure should also indicate where a fuller assessment is required, using more
sophisticated techniques with technical specialists and occupational health professionals (such as
environmental monitoring for chemicals, noise level measurements, and ergonomics).
5.6 Risk reduction
Note: A number of methodologies are available to do risk assessment. As stated in Clause 5.1.3, any method is acceptable
that is equivalent or more stringent than the method described in Clause 5.3.
5.6.1 General
The risk estimation process yields a level of risk (i.e., the severity of harm and probability of occurrence
of that harm). Unless the risk has already been adequately reduced, that risk shall be diminished by
implementing one or more protective measures.
The risk shall be considered to be adequately reduced when the risk level is unlikely to give rise to
a situation that could result in harm to any person (see Figure 2).
The type of protective measure shall be determined by the nature of the task and associated hazard(s)
for the machine under consideration. Protective measures shall be selected to provide the desired degree
of risk reduction (see Table 2).
Protective measures shall be considered in the hierarchical order of highest to lowest reduction of risk
as indicated in Clauses 5.6.2 to 5.6.4.
5.6.2 Eliminate the hazard or reduce the risk by design
Elimination of the hazard or reduction of the risk by design provides the highest degree of risk reduction.
Examples of such include
(a) substituting less hazardous materials and substances (e.g., toxicity);
(b) modifying physical features (e.g., sharp edges, shear points);
(c) reducing energy; or
(d) reducing the occurrence of the task or hazard.
5.6.3 Apply safeguards
Where the hazard cannot be eliminated as per Clause 5.6.2, the following safeguards shall apply:
(a) Safeguards providing the highest degree of risk reduction are
(i)
barrier (fixed) guards or protective devices preventing exposure of any part of the body to
the hazard, and secured with fastener(s) that require a tool to remove. If movable, such barriers
shall be interlocked using system control criteria as defined; and
(ii) control reliable systems (see Clause 8.2.5) to ensure the continuance of performance.
(b) Safeguards providing high/intermediate risk reduction are
(i)
barrier (fixed) guards or protective devices preventing exposure of any part of the body to the
hazard, and not removable or adjustable by unauthorized persons. If movable, such barriers
should be interlocked using system control criteria as defined;
(ii) physical devices that do not require adjustment for use or other operator intervention; and
(iii) control systems having redundancy with self-checking upon start-up to ensure the continuance
of performance.
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Where high risks are involved, a more formal and systematic method of assessment should be
used as described for the selection of interlocking methods specified throughout this Standard
(see Clauses 6.2.2.2, 6.2.2.4, 6.2.3.2.5, 7.16, 9.3, and 11.3, Tables A.3 to A.6, and Annex D).
(c) Safeguards providing low/intermediate risk reduction are
(i)
barrier (fixed) guards or protective devices providing simple guarding against exposure to
the hazard. Examples of such are a fixed screen, chuck guard, or movable barrier with simple
interlocking using system control criteria as defined;
(ii) physical devices that require adjustment for use; and
(iii) control systems (including associated protective devices, actuators, and interfaces) having
redundancy that may be manually checked to ensure the continuance of performance.
(d) Safeguards providing the lowest degree of risk reduction are
(i)
physical barriers providing tactile or visual awareness of the hazard, or minimal protection
against inadvertent exposure. Examples are post and rope, swing-away shield, or movable
screen; and
(ii) electrical, electronic, hydraulic, or pneumatic devices and associated control systems using
a single-channel configuration.
Where protective measures depend on programmable devices, the reliability of these devices and
the system should be appropriate for the level of risk.
5.6.4 Implement administrative controls or other protective measures
Eliminating the hazard or reducing the risk by design or applying safeguards should be pursued to the
fullest extent practicable before using other protective measures as described below. Implementation
of administrative controls or other protective measures (which rely upon human response) includes
a combination of
(a) warnings (e.g., signs, lights, alarms, awareness barriers);
(b) information for use (e.g., instruction manual(s), signage);
(c) safe work practices and other administrative controls;
(d) training (e.g., periodic, hands-on, certification);
(e) application of personal protective equipment; and
(f) supervision (e.g., close, qualified).
5.6.5 Example
As an example of the concepts described in Clauses 5.6.2 to 5.6.4, a fixed barrier guard at the point
of operation on a power press is a preferable safeguard and may be sufficient to reduce high risk to an
adequately reduced level. A pullout or holdout device cannot achieve a similar degree of risk reduction
unless it is properly selected for the application and used in conjunction with administrative control
measures, including proper adjustment, maintenance, and enforcement of use. In like manner, a light
curtain cannot achieve a similar degree of risk reduction unless used in conjunction with a control
system having a high degree of reliability.
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Table 2
Safeguarding selection matrix
(See Clause 5.6.1.)
Severity of
injury
Exposure
Avoidance
Serious
Frequent
Not likely
Likely
Infrequent
Not likely
Likely
Slight
Frequent
Not likely
Likely
Infrequent
Not likely
Likely
Safeguard
performance*
Circuit
performance
European
category
Hazard elimination or
hazard substitution.
Control reliable
Category 3 and 4
Control reliable
Category 3 and 4
Control reliable
Category 3 and 4
Single channel
with monitoring
Category 2
Single channel
Category 1
Single channel
Category 1
Simple
Category B
Simple
Category B
Engineering controls
preventing access to the
hazard, or stopping the
hazard, e.g., fixed guards,
interlocked barrier guards,
light curtains, safety mats,
or other presence-sensing
devices.
Non-interlocked barriers,
clearance, procedures,
and equipment.
Awareness means.
*All safeguarding methods should be considered at all risk levels, starting with “hazard elimination or hazard
substitution”.
Note: There is no intent to imply that circuit performance classifications are equivalent to ISO 13849-1 machinery
categories. See Table A.2 for example descriptions of risk factor categories.
5.6.6 Disabling safeguards
Tasks that require removal or disabling of one or more safeguards shall have administrative controls
to ensure that the safeguards are always restored to full operational status.
5.6.7 New tasks
New task/hazard combinations introduced during the risk reduction process shall be identified by
repeating the risk assessment process for the task/hazard combinations being evaluated.
5.6.8 Modifications
Where modifications are made to the machine or system (e.g., intended use, tasks, hardware,
and software), a risk assessment or risk reduction process shall be repeated for those parts of the
machine or system being modified or affected.
5.6.9 Achievement of adequate risk reduction
The risk reduction process is complete when protective measures consistent with Clause 5.6.1 are applied
and adequate risk reduction has been achieved for the identified task or hazard combinations and the
machine as a whole.
5.7 Documentation
5.7.1 General
A record of the results of risk assessments shall be kept and made available, with the objective of making
it a useful tool that provides both a management record and a source of information for managers
and workers.
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5.7.2 Manufacturer documentation
Manufacturer documentation of the risk assessment and the risk reduction process should detail the
procedure that has been followed and the results that have been achieved. The manufacturer should
provide documentation of the protective measures taken and recommendations for additional protective
measures to be implemented by the user, system integrator, or other entity involved in machine
utilization.
5.7.3 User documentation
User documentation of the risk assessment and the risk reduction process shall detail the procedure that
has been followed and the results that have been achieved. The user documentation should include the
protective measures taken and the resulting residual risks.
5.7.4 Co-operation between manufacturer and user
Co-operation between the manufacturer and user is encouraged for the risk assessment and risk reduction
process and in the documentation of the process.
Manufacturer and user risk assessment and risk reduction documentation should include
(a) the machine for which the assessment has been made (e.g., specifications, limits, intended use);
(b) any relevant assumptions that have been made (e.g., loads, strengths, safety [design] factors);
(c) the hazardous situations (task/hazard combinations) identified;
(d) the information on which risk assessment was based (see Clause 5.1) including
(i)
the data used and the sources (e.g., accident histories, experiences gained from risk
reduction applied to similar machines); and
(ii) the uncertainty associated with the data used and its impact on the risk assessment;
(e) the objectives to be achieved by protective measures;
(f) the protective measures implemented to eliminate identified hazards or to reduce risk
(e.g., from standards or other specifications);
(g) the residual risks associated with the machine;
(h) the names and professional background/responsibilities of the individuals performing the
assessment; and
(i) the date of the assessment.
6 Basic concepts and general safety considerations for design
6.1 Hazards to be considered when designing machinery
Note: This Clause is adapted from ISO 12100-1.
6.1.1 General
The purpose of Clause 6.1 is to provide a description of basic hazards with a view to assisting the designer
in identifying the relevant and significant hazards that the machine under consideration can generate
and the hazards associated with the environment in which the machine is used. Annex B provides
examples of other hazards and possible design solutions.
6.1.2 Using standardized measurement methods
If standardized measurement methods exist for a hazard, those measurement methods (e.g., an emission)
shall be used.
For example: measurement of emission values make it possible to
(a) assess the efficiency of the technical measures implemented at the design stage in order to reduce
emissions;
(b) assess the risk associated with the emissions;
(c) provide potential purchasers with quantitative information on emissions by their insertion in the
technical documentation; and
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(d) provide quantitative information on emissions by their insertion in the instructions for use.
Other measurable hazards can be dealt with in a similar manner.
6.1.3 Mechanical hazards
6.1.3.1 General
Mechanical hazard is a general designation for all physical factors that can give rise to injury deriving from
the mechanical action of a machine, machine parts, tools, workplaces, and loads, or from projected solid
or fluid materials.
6.1.3.2 Elementary forms of mechanical hazards
The elementary forms of mechanical hazard are notably (see descriptions in Table A.7):
(a) entanglement:
Entanglement occurs as a result of bodily contact with one of the following features:
(i)
a single rotating surface;
(ii) projections or gaps;
(iii) counter-rotating parts;
(iv) rotating and tangentially moving parts;
(v) rotating and moving parts;
(vi) rotating and fixed parts; and
(vii) material in motion.
(b) friction and abrasion:
Friction and abrasion occur as the result of bodily contact with relatively smooth parts operating at
high speeds (e.g., the rim of a centrifuge) or abrasive hazards (e.g., abrasive wheels or belt sanders).
(c) cutting or severing:
Cutting occurs as a result of bodily contact with such items as cutting tools, saws, routers, knives, or
moving sheet metal.
(d) shearing:
Parts of the body may be sheared between two machine parts or between a machine part and a
workpiece.
(e) stabbing or puncturing:
The body may be penetrated by flying objects or by rapidly moving parts.
(f) impact:
Impact occurs as the result of bodily contact with objects acting against the inertia of the body but
not penetrating it.
(g) crushing:
Crushing occurs as the result of bodily contact between one part of machinery moving against
another part.
(h) drawing-in or trapping:
Drawing-in occurs as the result of bodily contact with one of the following mechanisms:
(i)
in-running nips between two counter-rotating parts; and
(ii) in-running nips between a rotating surface and a tangentially moving surface; and
(i) pressurized liquids or gases injection or ejection:
Compressed air or high-pressure fluid injection occurs as the result of skin exposure to high-pressure
streams such as compressed air jets, paint sprayers, or hydraulic systems.
6.1.3.3 Factors in the generation of mechanical hazards
The mechanical hazard that can be generated by a machine, machine parts (including work material
holding mechanisms), workpieces, or loads is conditioned, among other factors, by
(a) shape (cutting elements, sharp edges, angular parts, even if they are motionless);
(b) relative location, which can create crushing, shearing, and entanglement zones when they are
moving;
(c) stability against overturning (considering kinetic energy);
(d) mass and stability (potential energy of elements that can move under the effect of gravity);
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(f)
(g)
(h)
(i)
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mass and velocity (kinetic energy of elements in controlled or uncontrolled motion);
acceleration/deceleration;
inadequate mechanical strength, which can generate hazardous breakages or bursts;
potential energy of elastic elements (springs), or high pressure injection or rejection hazard; and
conditions of use (e.g., environment varying operational fields).
6.1.3.4 Slipping, tripping, and falling
Because of their mechanical nature, hazards resulting from slipping, tripping, and falling in relationship
with machinery should also be considered, as well as access, egress, and working surfaces (e.g., stairs,
ladders, etc.).
6.1.4 Other hazards
6.1.4.1 Electrical hazards
Electrical hazards can cause injury or death from explosion, electric shock, or burn. These can be caused by
(a) contact of persons with
(i)
live parts, i.e., parts that normally carry a voltage (direct contact); or
(ii) parts that have become live under fault conditions, especially as a result of an insulation failure
(indirect contact);
(b) approach of persons to live parts, especially in the range of high voltage;
(c) insulation not suitable for reasonably foreseeable conditions of use;
(d) electrostatic phenomena, such as contact of persons with charged parts; or
(e) thermal radiation or phenomena, such as projection of molten particles and chemical effects from
short-circuits and overloads.
Such hazards can also cause falls of persons (or of objects dropped by persons) as a result of the
surprise induced by electric shock.
6.1.4.2 Thermal hazards
Thermal hazard can result in
(a) burns and scalds from contact with objects or materials with an extreme temperature, flames,
or explosions and radiation from heat sources; or
(b) health-damaging effects generated by hot or cold work environment.
6.1.4.3 Hazards generated by noise
Noise can result in
(a) permanent hearing loss;
(b) tinnitus;
(c) tiredness and stress;
(d) other effects such as loss of balance or loss of awareness; or
(e) interference with speech communication or acoustic signals.
6.1.4.4 Hazards generated by vibration
Vibration can be transmitted to the whole body (use of mobile equipment) and particularly to hands
and arms (use of hand-held and hand-guided machines).
The most severe vibration (or a less severe vibration over a long time) may generate
(a) serious disorders (low-back morbidity and trauma of the spine);
(b) severe discomfort resulting from whole-body vibration; and
(c) vascular disorders, e.g., white-finger, neurological, osteo-articular disorders, resulting from
hand/arm vibration.
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6.1.4.5 Hazards generated by radiation
Hazards generated by radiation can have immediate effects (e.g., burns) or long-term effects (e.g., genetic
mutations). They are produced by a variety of sources and can be generated by non-ionizing or ionizing
radiation as, for example, in
(a) low frequency, radio frequency, and micro-waves;
(b) infrared, visible light, and ultraviolet light;
(c) X and γ rays;
(d) α, β rays;
(e) electron or ion beams; or
(f) release of neutrons.
6.1.4.6 Hazards generated by lasers
Hazards generated by lasers can have immediate biological effects. A laser beam of sufficient power can
produce injuries to the eyes and/or skin. The hazards associated with skin exposure are of less importance
than eye hazards; however, with the expanding use of higher-power laser systems, particularly ultraviolet
lasers, the unprotected skin of personnel may be exposed to extremely hazardous levels of the beam
power if used in an unenclosed system design.
6.1.4.7 Hazards generated by materials and substances
Materials and substances processed, used, produced, or exhausted by machinery and materials used
to construct machinery can generate several different hazards. For example,
(a) hazards resulting from ingestion, contact with the skin, eyes, and mucous membranes, or inhalation
of fluids, gases, mists, fumes, fibres, and dusts having, for example, a harmful, toxic, corrosive,
teratogenic, carcinogenic, mutagenic, or irritant effect;
(b) fire and explosion hazards; or
(c) biological (e.g., mould) and micro-biological (viral or bacterial) hazards.
6.1.4.8 Hazards generated by neglecting ergonomic principles in
machine design
Mismatch of machinery with human characteristics and abilities can show itself by
(a) physiological effects (e.g., musculo-skeletal disorders) resulting, for example, from unhealthy postures
or excessive or repetitive efforts;
(b) psycho-physiological effects generated, for example, by mental overload or underload, or stress,
arising from the operation, supervision, or maintenance of a machine within the limits of its
intended use (see Clause 6.2.1.7); or
(c) human errors.
6.1.4.9 Hazards combinations
Some individual hazards that seem to be minor can, when combined with each other, be equivalent to a
significant hazard.
6.1.4.10 Hazards associated with the environment in which the
machine is used
Where a machine is designed to operate under environmental conditions that can result in hazards
(e.g., temperature, wind, snow, lightning), these hazards shall be taken into account. Some individual
hazards that seem minor, when combined, can present a significant hazard.
6.1.5 Linking mechanical and non-mechanical hazards
Many of the safeguards that are adopted in order to eliminate or mitigate personal harm from
non-mechanical hazards identified in Clause 6.1.4 will need to be considered in conjunction with
the safeguards against the mechanical hazards identified in Clause 6.1.3 in order to minimize the
total risk level, e.g., acoustic guards to prevent access and contain or absorb noise, welding curtains
to protect against radiation, spatter, and burns.
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6.1.6 Strategies for reducing risk
The strategies for reducing risk of injury that shall be applied to hazards are as follows:
(a) identify the hazard or hazards (see Clause 5.4);
(b) use risk assessment techniques to assess and document hazards (see Clause 5.5);
(c) eliminate the hazards by inherently safe design (see Clauses 6 and 7); and
(d) limit the risk through
(i)
the use and selection of safeguards (see Clauses 8, to 10);
(ii) consideration of interlock(s) and control methods (see Clause 9.3 and Annex A);
(iii) consideration of environmental, installation, and maintenance factors (see Clauses 12 to 14);
and
(iv) the use of safe working practices (see Clause 15).
6.2 Technical principles
Note: This Clause is adapted from ISO 12100-2.
6.2.1 Intrinsic design measures
6.2.1.1 General
Intrinsic design consists in the following actions, used separately or combined:
(a) avoiding or reducing as many of the hazards as possible by suitable choice of design features; and
(b) limiting the exposure of persons to hazards by reducing the need for operator intervention in
danger zones.
6.2.1.2 Avoiding sharp edges, corners, and protruding parts
Insofar as their purpose allows, accessible parts of the machinery shall have no sharp edges, sharp angles,
rough surfaces, or protruding parts likely to cause injury, and no openings that may “trap” parts of the
body or clothing. In particular, sheet metal edges shall be deburred, flanged, or trimmed, and open ends
of tubes, which may cause a “trap”, shall be capped.
6.2.1.3 Consideration of geometrical and physical factors
Geometrical and physical factors should be considered at the machine’s design stage. Examples of such
factors include
(a) the shape and the relative location of their mechanical component parts. For instance, crushing and
shearing hazards are avoided by increasing the minimum gap between the moving parts, such that
the part of the body under consideration can enter the gap safely, or by reducing the gap so that no
part of the body can enter it;
(b) designing the shape of machinery to maximize direct visibility of the working area and hazard zones
from the control position, or reducing blind spots, particularly when safe operation requires
permanent direct control by the operator, for example,
(i)
the travelling and working area of mobile machines;
(ii) the zone of movement of lifted loads or of the carrier of machinery for lifting persons; or
(iii) the area of contact of the tool of a hand-held or hand-guided machine with the material being
worked;
(c) the limitation of the actuating force to a sufficiently low value so that the element does not generate
a mechanical hazard;
(d) the limitation of the mass and/or velocity of the movable elements, and therefore of their kinetic
energy; and
(e) the limitation of noise and vibration by acting on the physical characteristics of the source.
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6.2.1.4 Considering technical knowledge of machine design and
construction
Technical knowledge of machine design and construction includes design codes and calculation rules
and should at least cover
(a) mechanical stresses, e.g.,
(i)
stress limitation by implementation of correct calculation, construction, and fastening methods
in, for example, bolted assemblies, welded assemblies;
(ii) stress limitation by overload prevention (e.g., “fusible” plugs, pressure-limiting valves, breakage
points, torque-limiting devices);
(iii) avoiding fatigue in elements under variable stresses (notably cyclic stresses); and
(iv) static and dynamic balancing of rotating elements;
(b) materials, e.g., consideration of
(i)
material properties;
(ii) corrosion, aging, abrasion, and wear;
(iii) brittleness;
(iv) material homogeneity; and
(v) toxicity of materials; and
(c) collection and comparison of emission values, e.g.,
(i)
noise;
(ii) vibration;
(iii) hazardous substances; and
(iv) radiation.
When the reliability of particular components or assemblies is critical for safety (e.g., ropes, chains, lifting
accessories for lifting loads or persons), stress limits shall be multiplied by the appropriate safety factor.
Increased safety factors shall be used for the lifting of persons.
6.2.1.5 Using intrinsically safe technologies, processes, energy sources
Intrinsically safe technologies should be used in the design of some machinery. For example,
(a) on machines intended for use in explosive atmospheres:
(i)
fully pneumatic or hydraulic control systems and machine actuators; or
(ii) “intrinsically safe” electrical equipment (see Canadian Electrical Code, Part 1);
(b) electrical supply that uses PELV (protective extra-low voltage — Canadian Electrical Code, Part 1; and
(c) use of fire-resistant and non-toxic fluids in hydraulic equipment of machines.
6.2.1.6 Applying principles of positive mechanical action of
components
If a moving mechanical component inevitably moves another component along with it, either by direct
contact or via rigid elements, these components shall be connected in the positive mode. An example of
this is the positive opening operation of switching devices in an electrical circuit.
6.2.1.7 Observing ergonomic principles
6.2.1.7.1
The observance of ergonomic principles in designing machinery contributes to increasing safety by
reducing stress in and physical effort of the operator. It also improves the performance and reliability of
the operation and therefore it reduces the probability of errors at all stages of machine use.
6.2.1.7.2
Note shall be taken of these principles when allocating functions to the operator and the machine
(degree of automation) in the basic design.
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6.2.1.7.3
Account shall be taken of body sizes, strengths and postures, movement amplitudes, and frequency
of cyclic actions to avoid hindrance, strain, and physical or psychological damage.
6.2.1.7.4
All elements of the “operator-machine” interface, such as controls, signalling, or data display elements,
shall be designed in such a way that clear and unambiguous interaction between the operator and the
machine is possible.
6.2.1.7.5
Designers’ attention shall be especially drawn to the following ergonomic aspects of machine design:
(a) avoiding stressful postures and movements during use of the machine (e.g., by providing facilities
to adjust the machine to suit the various operators);
(b) adapting machines, and more especially hand-held and mobile machines, to human effort and
displacement characteristics and to hand, arm, and leg anatomy;
(c) avoiding as far as possible noise, vibration, thermal effects (e.g., extreme temperatures);
(d) avoiding linking the operator’s working rhythm to an automatic succession of cycles;
(e) providing local lighting on the machine to illuminate the working area and for adjusting, setting-up,
and frequent maintenance zones when the design features of the machine and/or its guards render
inadequate the ambient lighting of normal intensity. Flicker, dazzling, shadows, and stroboscopic
effects shall be avoided if they can cause a risk; if the position or the lighting source has to be
adjusted, its location shall be such that it does not cause any hazard to persons making the
adjustment;
(f) designing, locating, and identifying manual controls (actuators) so that
(i)
they are clearly visible and identifiable and appropriately marked where necessary;
(ii) they can be safely operated without hesitation or loss of time and without ambiguity
(e.g., a standard layout of controls reduces the possibility of error when an operator
changes from a machine to another one of similar type having the same pattern
of operation);
(iii) their location (for push-buttons) and their movement (for levers and handwheels) are
consistent with their effect; and
(iv) their operation cannot cause additional risk.
6.2.1.7.6
Where a control is designed and constructed to perform several different actions, namely, where there
is no one-to-one correspondence (e.g., keyboards), the action to be performed shall be clearly displayed
and subject to confirmation where necessary.
6.2.1.7.7
Controls shall be so arranged that their layout, travel, and resistance to operation are compatible with
the action to be performed, taking account of ergonomic principles. Constraints due to the necessary
or foreseeable use of personal protective equipment (such as footwear and gloves) shall be taken into
account.
6.2.1.7.8
Indicators, dials, and visual display units shall be designed and located so that
(a) they fit within the parameters and characteristics of human perception;
(b) information displayed can be detected, identified, and interpreted conveniently, i.e., long lasting,
distinct, unambiguous, and understandable with respect to the operator’s requirements and the
intended use; and
(c) the operator is able to perceive them from the control position.
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6.2.1.7.9
Machinery shall be designed to maximize the direct visibility of working areas or hazard zones, and means
of indirect vision shall be chosen and located, where necessary, to take into account the characteristics of
human vision.
The design of the machine shall be such that from the main control position, the operator is able
to ensure that there are no exposed persons in the danger zones. Where direct vision is not possible,
it may be necessary to use additional means (e.g., mirrors and cameras). If this is impossible for very
large machines, the control system shall be designed and constructed so that an acoustic and/or visual
warning signal is given whenever the machine is about to start.
6.2.1.8 Applying intrinsic design measures to control systems
6.2.1.8.1
6.2.1.8.1.1
Insufficient attention to the design of machine control systems can lead to unforeseen and potentially
hazardous machine behaviour.
6.2.1.8.1.2
Typical causes of hazardous machine behaviour are
(a) an unsuitable design or a modification (accidental or deliberate) of the control system logic;
(b) a temporary or permanent defect or failure of one or several components of the control system;
(c) a variation or a failure in the energy source of the control system; and
(d) a wrong design or location of controls.
6.2.1.8.1.3
Typical examples of hazardous machine behaviour are
(a) unintended/unexpected start-up;
(b) uncontrolled speed change;
(c) failure to stop moving parts;
(d) dropping or ejection of a mobile part of the machine or of a workpiece clamped by the machine; and
(e) inhibition of protective devices.
6.2.1.8.2
Control systems shall be provided with the means to enable operator interventions to be carried out safely
and easily. Such systems require
(a) systematic analysis of start and stop conditions;
(b) provision for specific operating modes (e.g., start-up after normal stop, restart after cycle interruption
or after emergency stop, removal of the workpieces contained in the machine, operation of a part
of the machine in case of a failure of a machine element);
(c) clear display of the faults when using an electronic control system and a visual display unit;
(d) measures to prevent accidental generation of unexpected commands (e.g., start-up) likely to
cause dangerous machine behaviour; and
(e) measures of an “architectural nature” designed to prevent unexpected commands (e.g., start-up)
that result in dangerous machine behaviour.
6.2.1.8.3
Since safety is not obtained by the simple juxtaposition of different parts said to be safe, the following
shall be considered in the case of assemblies of machines:
(a) the interfaces between the different parts;
(b) the interactions between the different parts; and
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(c) the fact that each part can have its own production rate, which can require operating several parts
in parallel for certain stages of the process. This assumes
(i)
that a stopped part does not signify that the other parts are in a safe condition; and
(ii) that access to the part that is stopped while the rest of the machine carries on working has
to be taken into account.
6.2.1.8.4
When zones can be determined, their delimitations shall be evident (including the effect of the associated
emergency stop device). This shall also apply to the effect of isolation and energy dissipation.
6.2.1.8.5
Control systems shall be designed to limit the movements of parts of the machinery, of the machine itself,
or of elements held by the machinery to safe limits (range, speed, acceleration). Allowance shall be made
for dynamic effects (e.g., the swinging of loads). For example:
(a) the travelling speed of mobile machinery controlled by direct contact of a pedestrian shall be
compatible with walking speed;
(b) the range, speed, acceleration, and deceleration of movements of the earner and carrying vehicle
for lifting persons shall be limited to non-hazardous values, taking into account the total reaction time
of the operator and the machine; and
(c) the range of movements of parts of machinery for lifting loads shall be kept within specified limits.
6.2.1.8.6
When machinery is designed to use synchronously different elements that can also be used independently,
the control system shall be designed to prevent risks due to lack of synchronization.
6.2.1.8.7
In order to prevent hazardous machine behaviour and achieve safety functions, the design of control
systems shall be in accordance with the principles and/or methods found in Clause 6.2.1.9, applied singly
or combined as appropriate to the circumstances.
6.2.1.9 Starting of internal energy sources/switching on external
energy sources
6.2.1.9.1 General
Starting an internal energy source or switching on an external energy source shall not result in the starting
of working parts (e.g., starting the internal combustion engine shall not lead to movement of a mobile
machine; connection to mains electricity supply shall not result in starting of working parts of an electrical
machine).
6.2.1.9.2 Starting/stopping of a mechanism
6.2.1.9.2.1
The primary action for starting or accelerating the movement of a mechanism should be performed by
application or increase of voltage or fluid pressure, or, if binary logic elements are considered, by passage
from state 0 to state 1 (if state 1 represents the highest energy state).
6.2.1.9.2.2
The primary action for stopping or slowing down the movement of a mechanism shall be performed by
removal or reduction of voltage or fluid pressure, or, if binary logic elements are considered, by passage
from state 1 to state 0 (if state 1 represents the highest energy state).
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6.2.1.9.2.3
When, in order for the operator to maintain permanent control of deceleration, this principle is not
observed (e.g., a hydraulic braking device of a self-propelled mobile machine), the machine shall be
equipped with a means of slowing and stopping in case of failure of the main braking system.
6.2.1.9.3 Restart after energy interruption
If it may generate a hazard, the spontaneous restart of a machine when it is re-energized after energy
interruption shall be prevented (e.g., by use of a self-maintained relay, contactor, or valve).
6.2.1.9.4 Interruption of energy supply
Machinery shall be designed to prevent hazardous situations resulting from interruption or excessive
fluctuation of the energy supply as follows:
(a) the stopping function of the machinery shall remain;
(b) all devices whose permanent operation is required for safety shall continue to operate (e.g., locking,
clamping devices, cooling or heating devices, power-assisted steering of self-propelled mobile
machinery); and
(c) parts of machinery or elements held by machinery that are liable to move as a result of potential
energy shall be retained for the time necessary to allow them to be safely lowered.
6.2.1.9.5 Use of reliable components
The use of reliable components involves those components that are able to withstand all disturbances
and stresses associated with the usage of the equipment in the conditions of intended use, for the
period of time fixed for the use, without failures generating a hazardous malfunctioning of the machine.
Note: Environmental stresses that should be taken into consideration are: impact, vibration, cold, heat, moisture, dust,
aggressive substances, static electricity, and magnetic and electric fields (see Clauses 13.1 and 13.2). Examples of
disturbances that may be generated by these stresses include insulation failures and temporary or permanent failures in
the function of control system components (see Clause 6.2.1.11.2).
6.2.1.9.6 Use of “oriented failure mode” components
“Oriented failure mode” components or systems are those in which the predominant failure mode is
known in advance.
6.2.1.9.7 Duplication (or redundancy) of “critical” components
Components other than control reliable may be used to perform a safety function, provided that,
in case of failure of one component, another one (or others) can continue to perform this function,
thus maintaining the safety function. It is then essential to provide for automatic monitoring in
combination with diversity of design and/or technology to avoid common cause or common mode
failures (e.g., from electromagnetic disturbance).
6.2.1.9.8 Use of automatic monitoring
6.2.1.9.8.1
Automatic monitoring ensures that a protective measure is initiated if the ability of a component or an
element to perform its function is diminished, or if the process conditions are changed in such a way that
hazards are generated.
There are two categories of automatic monitoring:
(a) “continuous” automatic monitoring, whereby the protective measure is immediately initiated when
a failure occurs; and
(b) “discontinuous” automatic monitoring, whereby the protective measure is delayed until a specific
event occurs (e.g., the beginning of the next machine cycle) following a failure.
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6.2.1.9.8.2
The protective measures may be
(a) the stopping of the hazardous process;
(b) preventing the re-start of this process after the first stop following the occurrence of the failure in
the component or element; or
(c) the triggering of an alarm.
6.2.1.9.9 Maintaining safety functions in re-programmable control
systems
6.2.1.9.9.1
Systems intended to be capable of re-programming present additional safety problems include
(a) selector switches or valves affecting otherwise “hardware-based logic”; and
(b) electronic or optical storage.
6.2.1.9.9.2
When such arrangements are used in a safety critical control system, care shall be taken to provide
a means of preventing inadvertent or deliberate alteration of the stored program. Such means may include
(a) embedded software, e.g., read-only memory (ROM);
(b) locks restricting access; and
(c) password access to software.
Note: Fault-detection and diagnosis systems should be used to check errors resulting from reprogramming whenever
possible.
6.2.1.9.10 Principles relating to manual control
6.2.1.9.10.1
Manual control devices shall be designed and located according to the relevant ergonomic principles.
6.2.1.9.10.2
A stop control device shall be placed near each start control device. Where the start/stop function is
performed by means of a hold-to-run control, a separate stop control device shall be provided if a risk
can result from the hold-to-run control device failing to deliver a stop command when released.
6.2.1.9.10.3
Controls shall be located outside the danger zones, except for certain controls, such as emergency stop
or teach pendant, where, of necessity, they are located within a danger zone.
6.2.1.9.10.4
Whenever possible, control devices and control stations shall be located so that the operator has direct
visibility of the working area or hazard zone, in particular, when safe operation depends on direct
permanent control by the operator. For example,
(a) the driver of a ride-on mobile machine shall be able to actuate all control devices required to operate
the machine from the driving position, except for functions that can be controlled more safely from
other positions; or
(b) on machinery intended for lifting persons, controls for lifting and lowering and, if appropriate,
for moving the carrier shall generally be located in the carrier. If safe operation requires controls
to be situated outside the carrier, the operator in the carrier shall be provided with the means of
preventing hazardous movements.
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6.2.1.9.10.5
If it is possible to start the same hazardous element by means of several controls, the control circuit
shall be so arranged that only one control is effective at a given time. This applies especially to machines
that can be manually controlled by means, among others, of a portable control unit (teach pendant,
for instance) with which the operator may enter danger zones. This does not apply to two-hand control
devices where more than one worker is protected by these devices.
6.2.1.9.10.6
Control actuators shall be designed or guarded so that their effect, where a risk is involved, cannot occur
without intentional operation.
6.2.1.9.10.7
For machine functions whose safe operation depends on permanent, direct control by the operator,
measures shall be taken to ensure the presence of the operator at the control station. This may be
achieved by the design and location of control devices (e.g., a ride-on self-propelled mobile machine
may have hold-to-run control devices that are inaccessible from outside the driving position), otherwise
it may require the use of sensor devices preventing operation of hazardous functions if the operator is not
at the control station.
6.2.1.9.10.8
Movement of cableless remote-controlled machinery shall stop automatically in case of loss of control.
6.2.1.9.11 Selection of control and operating modes
If machinery has been designed and built to allow for its use in several control or operating modes
presenting different safety levels (e.g., to allow for adjustment, maintenance, inspection), it shall either
be fitted with a mode selector that can be locked in each position or incorporate another selection means
that restricts the use of certain functions of the machinery to certain categories of operator (e.g., access
codes for certain numerically controlled functions). If a mode selector is used, each position of the selector
shall correspond to a single operating or control mode.
6.2.1.9.12 Control mode for setting, teaching, process changeover,
fault-finding, cleaning, or maintenance
6.2.1.9.12.1
Where, for setting, teaching, process changeover, fault-finding, cleaning, or maintenance of machinery,
a guard has to be displaced or removed and/or a protective device has to be neutralized, and where it is
necessary for the purpose of these operations for the machinery to be put in operation, safety of the
operator shall be achieved, where practicable, using a manual control mode that simultaneously
(a) disables the automatic control mode (this implies, among others, that no hazardous operation
may result from any sensor changing its state);
(b) permits operation of the hazardous elements only by triggering an enabling device, a hold-to-run
control device, or a two-hand control device; and
(c) permits operation of the hazardous elements only in enhanced safety conditions (e.g., reduced
speed, reduced energy/force, step-by-step — e.g., with a limited movement control device).
6.2.1.9.12.2
The manual control mode shall be associated with one or more of the following measures:
(a) restriction of access to the danger zone as far as possible;
(b) emergency stop control within immediate reach of the operator; or
(c) portable control unit (teach pendant) and/or local control (allowing sight of the controlled elements).
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6.2.1.9.13 Applying measures to control the effects of electromagnetic
radiation (EMC)
For electromagnetic compatibility of electrical equipment, see Clause 13.2.
6.2.1.9.14 Provision of diagnostic systems to aid fault-finding and
rectification
Whenever possible, diagnostic systems to aid fault-finding should be included at the design stage.
Such systems not only improve availability and maintainability of machinery, they also reduce the
exposure of maintenance staff to hazards.
6.2.1.10 Preventing hazards from pneumatic and hydraulic equipment
Pneumatic and hydraulic equipment of machinery shall be so designed that
(a) the maximum allowed pressure cannot be exceeded in the circuits (e.g., by means of pressurelimiting devices);
(b) no hazard may result from pressure losses, pressure drops, or losses of vacuum;
(c) no hazardous fluid jet or sudden hazardous movement of the hose (whiplash) may result from
leakages or component failures;
(d) air receivers, air reservoirs, or similar vessels (such as in hydro-pneumatic accumulators) comply
with the design rules for these elements;
(e) all elements of the equipment, and especially pipes and hoses, be protected against harmful
external effects;
(f) as far as possible, reservoirs and similar vessels (e.g., hydro-pneumatic accumulators) be
automatically depressurized when isolating the machine from its energy source and, if it is
not possible, means be provided for their isolation and/or local depressurizing and pressure
indication; and
(g) all elements that may remain under pressure after isolation of the machine from its energy
supply be provided with clearly identified exhaust devices and a warning label drawing
attention to the necessity of depressurizing those elements before any setting or maintenance
activity on the machine.
6.2.1.11 Preventing electrical hazard
6.2.1.11.1 General
For the design of the electrical equipment of machines, the Canadian Electrical Code, Part I, indicates
general provisions dealing with protection against electric shock.
Transportable tools should comply with the Canadian Electrical Code, Part I.
6.2.1.11.2 Limiting exposure to hazards through reliability of
equipment
Increased reliability of all component parts of machinery reduces the frequency of incidents requiring
rectification, thereby reducing exposure to hazards.
This applies to both energy systems (operating part) and control systems, as well as to safety
functions and other functions of machinery.
Safety-critical components (e.g., certain sensors) with a known reliability shall be used.
The elements of guards and of protective devices shall be particularly reliable, as their failure can
expose persons to hazards, and also as poor reliability would encourage attempts to defeat them.
6.2.1.12 Limiting exposure to hazards through mechanization or
automation of loading (feeding)/unloading (removal) operations
Mechanization and automation of machine loading/unloading operations and more generally of handling
operations (of workplaces, materials, and substances) limit the risk generated by these operations by
reducing personal exposure to hazards at the operating points.
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Automation can be achieved, for example, by robots, handling devices, transfer mechanisms, push rods,
and air-blast. Mechanization can be achieved, for example, by feeding slides and hand-operated
indexing tables.
While automatic feeding and removal devices have much to offer in preventing accidents to
machine operators, they can create danger when any faults are being rectified. Care shall be taken to
ensure that the use of these devices does not introduce further trapping hazards between the devices
and parts of the machine or materials being processed. If this cannot be ensured, safeguards shall be
provided to prevent access to these hazard points (see examples of false tables in Figures B.8 and B.9).
Automatic feeding and removal devices with their own control systems and the control system of
the associated machine shall be interconnected after thoroughly studying how all safety functions are
performed in all control and operation modes of these machines.
6.2.1.13 Limiting exposure to hazards through location of setting and
maintenance points outside of danger zones
The need to access danger zones shall be minimized by locating maintenance, lubrication, and setting
points outside these zones, thereby limiting exposure to hazards.
6.2.1.14 Provisions for machine maintainability
When designing a machine, the following maintainability factors shall be taken into account:
(a) accessibility of internal parts;
(b) ease of handling and human capabilities;
(c) suitable choice of workplaces;
(d) limitation of the number of special tools and equipment; and
(e) ease of supervision.
6.2.1.15 Provisions for machine stability and their elements
6.2.1.15.1
Machines and their elements shall be designed to be stable, i.e., so that they cannot tip over or roll over.
Factors that should be taken into account include
(a) geometry of the base;
(b) weight distribution;
(c) dynamic forces due to movements of parts of the machine, of the machine itself, or of elements
held by the machine that may result in an overturning moment;
(d) vibration;
(e) oscillations of the centre of gravity;
(f) characteristics of the supporting surface due to travelling or installation on different sites
(e.g., ground conditions, slope); and
(g) external forces (e.g., wind pressure, manual forces).
6.2.1.15.2
Stability should be considered in all phases of the life of the machine, including handling, travelling,
installation, use, out-of-use, and dismantling.
6.2.1.15.3
Both static and dynamic stability shall be considered.
6.2.1.15.4
If special protective measures are required, a warning shall be provided on the machine and/or in the
instruction handbook.
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6.2.2 Safeguarding and complementary protective measures
6.2.2.1 General
6.2.2.1.1
Safeguards (guards, protective devices) shall be used to protect persons from the hazards that cannot
reasonably be avoided or sufficiently limited by inherently safe design. Complementary protective
measures involving additional equipment (e.g., emergency stop equipment) may have to be taken.
6.2.2.1.2
The different kinds of guards and protective devices are defined in Clause 3.
6.2.2.1.3
Certain safeguards may be used to avoid exposure to more than one hazard (e.g., a fixed guard
preventing access to a zone where a mechanical hazard is present being used to reduce noise level
and collect toxic emissions).
6.2.2.2 Selection and implementation of guards and protective devices
6.2.2.2.1 General
6.2.2.2.1.1
Clause 6.2.2.2 provides guidelines for the selection and the implementation of guards and protective
devices, the primary purpose of which is to protect persons against hazards generated by moving
parts according to
(a) the nature of those parts; and
(b) the need for access to the danger zone(s). (See Figure 3.)
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Hazards generated by moving parts
contributing to the work (directly
involved in the process, e.g., tools)
Hazards generated by
moving transmission parts
Can these elements be
made completely
inaccessible while
working?
Yes
Fixed guards (see
Clauses 5.6.3, 6.2.3.2.2,
and 10.2.1)
Fixed guards (see Clauses 5.6.3
and 10.2.1)
or
or
interlocking fixed or
movable guards with or
without guard locking
(see Clauses 5.6.3(a),
6.2.3.2, and 10.2.2)
interlocking guards with or
without guard locking. With
automatic monitoring (see
Clauses 5.6.3(b) and 10.2.2)
or
protective devices (see
Clause 6.2.2.3)
Fixed guards, interlocking
guards, and protective
devices are selected as a
function of the need for
access to the danger zone
and of the characteristics of
the hazard (see Clauses 5.5.2.2,
6.2.3.2, 10.2, and 10.3).
No
Fixed guards (see Clauses 5.6.3
and 10.2.1) or movable guards
(see Clauses 5.6.3(b) and 10.2.2)
preventing access to the
moving parts within the zones
where they are not used
in the work
and
adjustable guards (see
Clauses 6.2.3.2.4 and
10.2.4) restricting access
to the moving parts in
those zones where access
is necessary for the
process
Figure 3
Guidelines to help make the choice of safeguards
against hazards generated by moving parts
(See Clauses 6.2.2.2.1.1 and 6.2.2.2.3.)
6.2.2.2.1.2
The exact choice of a safeguard for a particular machine shall be made on the basis of the risk
assessment for that machine.
6.2.2.2.1.3
In selecting an appropriate safeguard for a particular type of machinery or hazard zone, it shall be
borne in mind that a fixed guard is simple and shall be used where access of an operator to the danger
zone is not required during normal operation (operation without any malfunction) of the machinery.
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6.2.2.2.1.4
As the need for frequency of access increases, this inevitably leads to the fixed guard not being
replaced. This and the need to exercise close control over the approach to some hazards requires
the use of an alternative protective measure (e.g., movable interlocking guard, trip device).
6.2.2.2.1.5
A combination of safeguards may sometimes be required. For example, where, in conjunction with
a fixed guard, a mechanical loading (feeding) device is used to feed a workpiece into a machine,
thereby removing the need for access to the primary hazard zone, a trip device may be required
to protect against the secondary drawing-in or shearing hazard between the mechanical loading
(feeding) device, when reachable, and the fixed guard.
6.2.2.2.1.6
Consideration should be given to the enclosure of control stations or intervention zones to provide
combined protection against several hazards, which may include
(a) hazards from falling or ejected objects (e.g., falling object protection structure);
(b) emission hazards (e.g., protection against noise, vibration, radiation, harmful substances);
(c) hazards due to the environment (e.g., protection against heat, cold, foul weather); and
(d) hazards due to tipping over or rolling over of machinery (e.g., roll-over or tip-over protection
structure).
The design of such enclosed workstations shall take into account ergonomic principles concerning
visibility, lighting, atmospheric conditions, access, and posture.
6.2.2.2.2 Where access to hazard zone is not required during normal
operation
Where access to the hazard zone is not required during normal operation of the machinery, safeguards
should be selected from the following:
(a) fixed guard (openings in guard(s) shall be in accordance with Table 3);
(b) interlocking guard; or
(c) trip device, including electro-sensitive protective equipment and pressure-sensitive mats.
6.2.2.2.3 Where access to hazard zone is required during normal
operation
Where access to the hazard zone is required during normal operation of the machinery, safeguards should
be selected from the following:
(a) interlocking guard;
(b) trip device;
(c) adjustable guard;
(d) two-hand control device; or
(e) interlocking guard with a start function (control guard).
Note: For hazard zones generated by moving parts, Figure 3 provides specific guidelines.
6.2.2.2.4 Where access to hazard zone is required for machine setting,
teaching, process changeover, fault-finding, cleaning, or maintenance
As far as possible, machines shall be designed so that the safeguards provided for the protection of
the production operator may also ensure safety of personnel in charge of setting, teaching, process
changeover, fault-finding, cleaning, or maintenance without hindering them in performing their task.
When this is not possible (e.g., when it is necessary to remove fixed guards or to make protective
devices ineffective, with operation of the machine still possible), the machine shall be provided with
appropriate means of reducing the risk as much as possible and through the use of manual control
as mentioned in Clauses 6.2.1.9.12 and 7.23.
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Note: Isolation and energy dissipation for machine shut-down ensure the highest level of safety when carrying out tasks
(especially maintenance and repair tasks) that do not require the machine to remain connected to its energy source.
6.2.2.3 Application of protective equipment for presence sensing
6.2.2.3.1 Types
Types of protective equipment for presence sensing include
(a) infrared light curtains;
(b) infrared scanning devices;
(c) pressure-sensitive mats;
(d) passive infrared sensors; and
(e) capacitive loops.
6.2.2.3.2 Application modes
Application modes can be used
(a) as trip devices;
(b) as presence-sensing devices; or
(c) to initiate machine operation that is subject to stringent conditions.
6.2.2.3.3 Factors precluding use of protective equipment for presence
sensing
Presence-sensing devices shall not be used as trip devices if the following conditions exist:
(a) inconsistent or inadequate machine stopping performance (see Figure B.15);
(b) inability of a machine to stop part-way through a cycle; or
(c) tendency for the machinery to eject materials or component parts that create a hazard.
6.2.2.3.4 Basic considerations
Consideration should be given to
(a) size and positioning of the sensing zone;
(b) reaction of the device to fault conditions;
(c) possibility of circumvention; and
(d) sensing capability and its variation over the course of time.
6.2.2.4 Protective measures for stability
If stability cannot be obtained adequately by intrinsic design measures (e.g., by stable weight distribution),
then stability shall be obtained by special protective measures. For example,
(a) movements of parts of the machine may be restricted;
(b) instability indicators or alarms to warn if stability is endangered or interlocks to prevent tipping
may be provided; or
(c) the machine may be securely anchored to a foundation.
6.2.2.5 Other protective devices
6.2.2.5.1
Machinery whose safe operation requires permanent direct control by the operator shall be equipped
with the necessary devices to enable the operation to remain within specified limits, in particular, when
(a) the operator has insufficient visibility of the hazard zone;
(b) the operator may ignore the real value of a safety-related parameter (e.g., a distance, a speed,
the mass of a load, the angle of a slope); and
(c) hazards may result from operations other than those controlled by the operator.
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6.2.2.5.2
Such devices may include
(a) devices for limiting parameters of movement;
(b) overloading and moment control devices;
(c) devices to prevent collisions or interference with other machines;
(d) devices for preventing hazards to pedestrian operators of mobile machinery or other pedestrians;
(e) torque limiting devices, as well as breakage points to prevent excessive stress of components
and assemblies;
(f) devices for limiting pressure and temperature;
(g) devices to prevent operation in the absence of the operator at the control station;
(h) devices to prevent lifting operations unless stabilizers are in place;
(i) devices to limit inclination or slope; or
(j) devices to ensure that components are in a safe position before travelling.
6.2.2.5.3
Automatic protective measures triggered by such devices that take operation of the machinery out of the
control of the operator (e.g., automatic stop of hazardous movement) should be preceded by a warning
signal to enable the operator to retain control.
6.2.3 Requirements for design and construction of guards and
protective devices
6.2.3.1 General
6.2.3.1.1
In designing safeguards, the types of guard and of protective device and their methods of construction
shall be selected to take account of the mechanical and other hazards involved. Guards and protective
devices shall be compatible with the working environment of the machine and designed so that they
cannot be easily defeated. They shall provide the minimum possible interference with activities during
operation and other phases of machine life in order to reduce any incentive to defeat them.
6.2.3.1.2
Guards and protective devices shall
(a) be of robust construction;
(b) not give rise to any additional hazard;
(c) not be easy to by-pass or render non-operational;
(d) be located at an adequate distance from the danger zone (see Table 3);
(e) cause minimum obstruction to viewing the production process; and
(f) enable essential work to be carried out on installation and/or replacement of tools and also for
maintenance by restricting access only to the area where the work has to be done, if possible,
without the guard or protective device having to be moved.
6.2.3.2 Requirements for guards
6.2.3.2.1 Functions of guards
Guards may have to perform the following functions:
(a) prevent access to the space enclosed by the guard; and/or
(b) contain/capture materials, workplaces, chips, liquids, radiation, hazardous substances (e.g., dust,
fumes, gases), and noise that may be ejected, dropped, or emitted by the machine.
Additionally, they may need to have particular properties relating to electricity, temperature, fire,
explosion, vibration, and visibility.
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6.2.3.2.2 Requirements for fixed guards
Fixed guards shall be securely held in place
(a) permanently (e.g., by welding); or
(b) by means of fasteners (screws, nuts) making removal/opening impossible without using tools;
where possible, they should not remain closed without their fasteners.
Note: A guard that satisfies this requirement may be hinged to assist in its opening.
6.2.3.2.3 Requirements for movable guards
6.2.3.2.3.1
Movable guards that provide protection against hazards generated by moving transmission parts shall
(a) remain fixed to the machinery or other structure (generally by means of hinges or guides) when
open; and
(b) be interlocking guards with or without guard locking in order to prevent moving parts starting up as
long as these parts can be reached and to give a stop command whenever they are no longer closed.
6.2.3.2.3.2
Movable guards that provide protection against hazards generated by non-transmission moving parts shall
be designed and associated with the machine control system so that
(a) moving parts cannot start up while they are within the operator’s reach and the operator cannot
reach moving parts once they have started up; this can be achieved by interlocking guards without
guard locking;
(b) they can be adjusted only by means of an intentional action, such as the use of a tool, key, etc.;
(c) the absence or failure of one of their components prevents starting or stops the moving parts; this
can be achieved by automatic monitoring; and
(d) protection against ejection hazard is ensured by appropriate means.
6.2.3.2.3.3
Movable guards that provide protection against other hazards shall comply with Clauses 6.2.3.2.3.1 and
6.2.3.2.3.2 in accordance with the result of the risk assessment.
6.2.3.2.4 Requirements for adjustable guards
Adjustable guards can be used in situations where the hazard zone cannot be completely enclosed. They
shall
(a) be adjustable in a manner that ensures that the adjustment remains fixed during a particular
operation;
(b) be readily adjustable without the use of tools; and
(c) reduce as far as possible the risk from ejection.
6.2.3.2.5 Requirements for interlocking guards with a start function
(control guards)
An interlocking guard with a start function shall be used sparingly and only if
(a) the risk assessment process yields a level of adequate risk reduction;
(b) all requirements for interlocking guards are satisfied;
(c) the cycle time of the machine is short (e.g., preset time of no more than 1 min if not specified in
the appropriate type-C standard) so that when this time is exceeded, the hazardous movements
cannot be initiated by the closing of the control guard;
(d) the dimensions or shape of the machine (as specified in the appropriate type-C standard) do not
allow an operator or another person or a part of his or her body to stay in the hazard zone or between
the hazard zone and the guard while the guard is closed;
(e) opening the interlocking guard with a start function or another interlocking guard is the only way
to enter the hazard zone;
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(f)
the interlocking device associated with the interlocking guard with a start function is designed in such
a way that its failure cannot lead to an unintended/unexpected start-up and it is control reliable; and
(g) the guard is securely held open (e.g., by a spring or counterweight) such that it cannot initiate a
start while falling by its own weight.
6.2.3.2.6 Hazards from guards
Care shall be taken to prevent hazards that might be generated by the
(a) guard construction (sharp edges or corners, material, etc.); and
(b) movements of the guard (shearing or crushing zones generated by energy-driven guards and by
heavy guards that are liable to fall).
6.2.3.3 Technical characteristics of protective devices
A protective device intended to perform a critical safety function (see the definition in Clause 3) shall be
designed according to the following principles:
(a) Protective devices shall be operated and connected with the control system so that they cannot
be easily defeated.
(b) The characteristics of protective devices shall be consistent with the control system into which
they are integrated (see Clause 8.2 for control selection).
6.2.3.4 Provisions for alternative types of safeguards
Provisions should be made to facilitate the fitting of alternative types of safeguards on machinery where
it is known that this fitting will be necessary because the work to be done on it will vary.
6.2.3.5 Use of active opto-electronic protective devices
6.2.3.5.1 Basic requirements
An active opto-electronic protective device (AOPD) shall meet the following conditions:
(a) while the sensing field of the AOPD is interrupted, the machine cannot operate;
(b) the machine is stopped whenever the sensing field of the AOPD is interrupted during any part of
the hazardous motion;
(c) wherever the sensing field of the AOPD is broken, the part of the body in question is detected; and
(d) failure of the AOPD does not lead to the possibility of a person entering the space between the
sensing field of the AOPD and the hazard zone or to a reduction in the safety distance.
6.2.3.5.2 Additional requirements for AOPDs when used for cycle
initiation
An AOPD shall be used sparingly for cycle initiation and only if
(a) the risk assessment process yields a level of adequate risk reduction;
(b) the requirements for an AOPD used as a presence-sensing device are satisfied (in particular, location,
safety distance detection capability, reliability and monitoring of the control and braking system);
(c) the cycle time of the machine is short so that the opportunity to initiate the machine upon clearing
of the sensing field is limited to a period commensurate with a single normal cycle;
(d) the pre-set time (e.g., 1 min if not specified in the appropriate type-C standard) has been exceeded,
so that the AOPD is not capable of cycle initiation without using a reset procedure;
(e) the dimensions or shape of the hazard zone delimited by light curtains and guards does not allow
an operator or another person(s) to enter this zone;
(f) the AOPD and interlocking guards are the only way to enter the hazard zone;
(g) only one AOPD is capable of cycle if there is more than one AOPD safeguarding the machine; and
(h) the AOPD meets the requirements of a Type 4, as specified in IEC 61496 Parts 1 and 2, and the
interface of the AOPD to the control system is control reliable.
Note: The hazard zone considered in this clause is any zone where the operation of hazardous elements (including
transmission elements) is initiated by clearing the sensing field.
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6.2.3.5.3 Complementary protective measures
Following the risk assessment, the measures in this clause either shall be applied to the machine or shall be
dealt with in the information for use.
Protective measures that are neither inherently safe design measures, nor safeguarding (implementation
of guards and/or protective devices), nor information for use may have to be implemented as required
by the intended use and the reasonably foreseeable misuse of the machine. Such measures shall include,
but not be limited to,
(a) emergency stop;
(b) means of rescue of trapped persons; and
(c) means of energy isolation and dissipation.
6.2.3.5.4 Protective measures reducing emission
6.2.3.5.4.1 General
If the reduction of emission at its sources is not sufficiently achieved, the machine should be provided
with additional protective measures.
6.2.3.5.4.2 Noise
Examples of additional protective measures include
(a) enclosures;
(b) screens fitted to the machinery; and
(c) silencers.
For assessing noise emissions, the sound power level and the emission sound pressure level should be
determined. See CSA Z107.56 for industrial noise survey methods and CAN/CSA-Z107.58 for machinery
noise declaration requirements.
Note: Many jurisdictions have regulations governing noise levels, both indoors and outdoors.
6.2.3.5.4.3 Vibration
Examples of protective measures for vibration caused by machinery include
(a) vibration isolators;
(b) additional mass;
(c) vibration absorbers;
(d) resilient mounting; and
(e) suspended seat.
6.2.3.5.4.4 Hazardous substances
Measures for the reduction of emissions during the operation of machines include
(a) use of dust-reducing procedures (granules instead of powders, milling instead of grinding);
(b) encapsulation of the machine (enclosure with negative pressure);
(c) local ventilation with filtration;
(d) wetting with liquids; and
(e) special ventilation in the area of the machine (air curtains, cabins for operators).
6.2.3.5.4.5 Radiation devices
Measures for controlling ionizing and non-ionizing radiation from machinery include
(a) the use of minimum source strength to perform the intended job, taking into consideration
the half-life of the source and the service life of the gauge;
(b) construct devices with sufficient shielding to allow for personnel occupancy, taking into
consideration the intended use;
(c) construct devices with a shutter design that fails to a safe state when a fault occurs (i.e., air pressure
used to overcome the spring pressure to open the shutter; “lead” link that melts in the event of a fire
to close the shutter, etc.);
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(d) additional protective measures;
(e) use of the concepts of time, distance, and shielding to minimize exposures for anyone working in
the vicinity of a radiation device (limit time, increase distance); and
(f) installation of shielding (lead, leaded glass/Plexiglas®, steel).
Radiation devices shall comply with and be certified by the Canadian Nuclear Safety Commission in
accordance with the Canadian Nuclear Safety and Control Act.
6.2.3.5.4.6 Lasers
6.2.3.5.4.6.1
Where laser equipment is used, the following provisions shall be considered:
(a) Laser equipment on machinery shall be designed and constructed to prevent any accidental
radiation.
(b) Laser equipment on machinery shall be protected so that effective radiation — radiation produced
by reflection or diffusion — and secondary radiation do not damage health.
(c) Optical equipment for the observation or adjustment of laser equipment on machinery shall be
such that no health risk is created by the laser rays.
6.2.3.5.4.6.2
Measures for the reduction of laser radiation emissions below MPE levels include
(a) non-collapsible housing(s), beam tubes (laser-rated conduit media);
(b) non-reflecting surfaces;
(c) interlocked beam switches, beam stops, and beam shutters;
(d) laser attenuating viewing windows;
(e) laser-rated goggles; and
(f) sunscreen creams.
The choice of measures depends on the size, severity, frequency, and duration of exposure per laser
type and class.
6.2.3.5.5 Preventative measures for thermal hazards
6.2.3.5.5.1
Measures shall be taken to achieve adequate reduction of risk from contact with or proximity to
machinery parts or materials at high or very low temperatures. For example,
(a) engineering controls (e.g., insulative guards, water sprays);
(b) administrative controls;
(c) personal protective equipment; and
(d) procedural and awareness training.
6.2.3.5.5.2
The risk of hot or very cold materials being ejected shall be assessed. Where this risk exists, the necessary
steps shall be taken to achieve adequate reduction of risk or, if this is not technically possible, to render it
non-dangerous.
6.2.4 Information for use
6.2.4.1 General requirements
6.2.4.1.1
Information for use consists of communication links, such as texts, words, signs, signals, symbols,
or diagrams, used separately or in combination to convey information to the user. It is directed to
professional and/or non-professional users.
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The information for use is an integral part of the supply of a machine, as indicated in the definition
of the design of a machine.
6.2.4.1.2
Information shall be provided to the user on the intended use of the machine, in particular, on all of
its operating modes.
This information shall include all directions required to ensure safe and correct use of the machine.
It shall also explain and warn the user about residual risks following the application of safety measures
by the designer.
The information shall indicate
(a) if training is needed;
(b) if personal protective equipment is needed; and
(c) the possible need for additional safeguards.
This information shall also include uses of the machine that can reasonably be expected from its
designation and description and shall also provide adequate warning of inherent risk if the machine
is used in ways other than described in the information, especially with regard to its reasonably
foreseeable misuse.
6.2.4.1.3
Information for use shall not compensate for design deficiencies.
6.2.4.1.4
Information for use shall cover, separately or in combination, transport, commissioning (assembly,
installation, and adjustment), use (setting, teaching or process changeover, operation, cleaning,
fault finding, and maintenance of the machine), and, if necessary, decommissioning, dismantling,
and disposal.
6.2.4.2 Location and nature of information for use
Depending on the risk, time when the information is needed by the user, and machine design,
manufacturers shall determine whether the information — or parts thereof — should be given in/on
the machine itself and/or in accompanying documents (in particular an instruction handbook), and/or
what other means, such as signals and warnings, should be chosen.
Standardized phrases shall be considered where important messages such as warnings need to
be given.
6.2.4.3 Signals and warning devices
Visual signals, such as flashing lights, and audible signals, such as sirens, may be used to warn of
an impending hazardous event such as machine start-up or overspeed.
Such signals may also be used to warn the operator before the triggering of automatic protective
measures.
It is essential that these signals be
(a) emitted before the occurrence of the hazardous event;
(b) unambiguous;
(c) clearly perceived and differentiated from all other signals used; and
(d) clearly recognized by the users.
The warning devices shall be designed and located in such a manner that checking is easy. The
instruction handbook shall prescribe regular checking of warning devices.
The attention of designers is drawn to the risks of “sensorial saturation”, which results from too
many visual and/or acoustic signals and which may also lead to defeating the warning devices.
Note: Consultation of the user is often necessary in the determination of appropriate signals and warnings.
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6.2.4.4 Markings, signs (pictograms), and written warnings
6.2.4.4.1
Machinery shall bear all markings that are necessary
(a) for its unambiguous identification, including at the least
(i)
the name and address of the manufacturer;
(ii) the designation of the series or type; and
(iii) the serial number, if any;
(b) to indicate its compliance with mandatory requirements, namely
(i)
markings; and
(ii) written warnings (e.g., for machines that are usable in potentially explosive atmospheres); and
(c) for its safe use; for example,
(i)
the maximum speed of rotating parts;
(ii) the maximum diameter of tools;
(iii) mass (of removable parts, etc.);
(iv) the necessity of wearing personal protective equipment;
(v) guard adjustment data; and
(vi) the frequency of inspection.
6.2.4.4.2
Information printed directly on the machine should be permanent and remain legible throughout
the expected life of the machine.
6.2.4.4.3
Signs or written warnings that only say “danger” shall not be used.
6.2.4.4.4
Markings, signs, and written warnings shall be readily understandable and unambiguous, especially
as regards that part of the function(s) of the machine to which they are related. Readily understandable
signs (pictograms) should be used in preference to written warnings.
6.2.4.4.5
Signs and pictograms should only be used if they are understood in the culture in which the machinery
is to be used.
6.2.4.4.6
Written warnings shall be drawn up in English or French, or both, and, upon request, in the language(s)
understood by operators.
6.2.4.4.7
Refer to NFPA 79 as regards the marking of electrical equipment.
6.2.4.5 Accompanying documents (instruction handbook)
6.2.4.5.1 Contents
The instruction handbook or other written instructions (e.g., on the packaging) should contain,
among others,
(a) information relating to transport, handling, and storage of the machine, e.g.,
(i)
storage conditions for the machine;
(ii) dimensions, mass value(s), position of the centre(s) of gravity; and
(iii) indications for handling (e.g., drawings indicating application points for lifting equipment);
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(b) information relating to commissioning of the machine, e.g.,
(i)
fixing/anchoring and vibration dampening requirements;
(ii) assembly and mounting conditions;
(iii) space needed for use and maintenance;
(iv) permissible environmental conditions (e.g., temperature, moisture, vibration, electromagnetic
radiation);
(v) instructions for connecting the machine to an energy source (particularly with regard to
protection against electrical overloading);
(vi) advice about waste removal/disposal; and
(vii) if necessary, recommendations about protective measures that have to be taken by the user
(special protective devices, safety distances, safety signs and signals, etc.);
(c) information relating to the machine itself, e.g.,
(i)
a detailed description of the machine, its fittings, its guards and/or protective devices;
(ii) a comprehensive range of applications for which the machine is intended, including prohibited
usages, if any, taking into account variations of the original machine, if appropriate;
(iii) diagrams (especially schematic representation of safety functions);
(iv) data about noise and vibration generated by the machine, and about radiation, gases,
vapours, and dust emitted by it, with reference to the measuring method where this relates
to potential harm;
(v) technical documentation about electrical equipment; and
(vi) documents attesting that the machine complies with this Standard;
(d) information relating to the use of the machine, e.g.,
(i)
intended use;
(ii) description of manually operated controls (actuators);
(iii) instructions for setting and adjustment;
(iv) modes and means for stopping (especially emergency stop);
(v) information about the risks that could not be eliminated by the protective measures taken by
the designer;
(vi) information about particular risks that may be generated by certain applications or by the use
of certain fittings, and about specific safeguards that are necessary for such applications;
(vii) information about reasonably foreseeable misuse and prohibited applications;
(viii) instructions for fault identification and location, for repair, and for re-starting after an
intervention; and
(ix) if necessary, instructions relating to personal protective equipment that is to be used and to
training that is required;
(e) information for maintenance, e.g.,
(i)
the nature and frequency of inspections for safety critical functions;
(ii) instructions relating to maintenance operations that require a definite technical knowledge or
particular skills and that should be carried out exclusively by skilled persons (e.g., maintenance
staff, specialists);
(iii) instructions relating to maintenance actions (e.g., replacement of parts), the execution of
which does not require specific skills and may be carried out by users, e.g., operators;
(iv) drawings and diagrams enabling maintenance personnel to carry out their task (especially
fault-finding tasks); and
(v) maintenance instructions provided for skilled persons (see Item (e)(ii)) and for unskilled
persons (see Item (e)(iii)), which should appear clearly separated from each other;
(f) information relating to decommissioning, dismantling, and, as far as safety is concerned,
disposal; and
(g) information for emergency situations, e.g.,
(i)
the type of firefighting equipment to be used; and
(ii) a warning about possible emission/leakage of harmful substance(s) and, if possible, an
indication of the means to fight their effects.
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6.2.4.5.2 Production of the instruction handbook
The following aspects shall be considered in the production of the instruction handbook:
(a) Type and size of print shall ensure the best possible legibility. Safety warnings and/or cautions
should be emphasized by the use of colours, symbols, and/or large print.
(b) Information for use shall be given in English or French, or both. If more than one language is to
be used, each language should be readily distinguished from the other(s), and efforts should be
made to keep the translated text and the relevant illustration together.
(c) Whenever possible, text should be supported by illustrations. Illustrations should be supplemented
with written details enabling, for instance, manually operated controls (actuators) to be located and
identified: they should not be separated from the accompanying text and should follow sequential
operations.
(d) Consideration should be given to presenting information in tabular form where this will aid
understanding. Tables should be adjacent to the relevant text.
(e) The use of colours should be considered, particularly in relation to components requiring quick
identification.
(f) When information for use is lengthy, a table of contents and/or an index should be given.
6.2.4.5.3 Advice for drafting and editing information for use
The following factors shall be considered in drafting and editing information for use:
(a) Relationship to model: the information shall clearly relate to the specific machine model.
(b) Communication principles: when information for use is being prepared, the communication
process “see — think — use” should be followed in order to achieve the maximum effect and
should follow sequential operations. The questions “how” and “why” should be anticipated and
the answers provided.
(c) Information for use shall be as simple and as brief as possible, and should be expressed in
consistent terms and units with a clear explanation of unusual technical terms.
(d) When it is foreseen that a machine will be put to non-professional use, the instructions should
be written in a form that is readily understood by the non-professional user. If personal protective
equipment is required for the safe use of the machine, clear advice should be given, and this
information shall be prominently displayed at the point of sale, e.g., on the packaging as well as
on the machine.
(e) Durability and availability of the documents: Documents giving instructions for use should be
produced in durable form (i.e., they should be able to survive frequent handling by the user).
It may be useful to mark them “keep for future reference”.
6.2.5 Complementary protective measures
6.2.5.1 General
Following the risk assessment, the measures in Clause 6.2.5 shall either be applied to the machine or
be specifically addressed in the information for use (see Clause 6.2.4).
6.2.5.2 Precautions intended for emergency situations
6.2.5.2.1 Components and elements to achieve the emergency stop
function
If, following a risk assessment, it is determined that in order to achieve adequate risk reduction
under emergency circumstances a machine must be fitted with components and elements necessary
to achieve an emergency stop function so that actual or impending emergency situations can be
controlled, the following requirements shall apply:
(a) The actuators shall be clearly identifiable, clearly visible, and readily accessible.
(b) The hazardous process shall be stopped as quickly as possible without creating additional hazards.
If this is not possible or the risk cannot be adequately reduced, this may indicate that an emergency
stop function may not be the best solution (i.e., other solutions should be sought).
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(c) The emergency stop control shall trigger or permit the triggering of certain safeguard movements
where necessary.
Note: For more detailed provisions, see NFPA 79.
6.2.5.2.2 Effects of emergency stop and reset commands
Once active operation of the emergency stop device has ceased following an emergency stop command,
the effect of this command shall be sustained until the device is reset. This reset shall be possible only at
that location where the emergency stop command has been initiated. The reset of the command shall not
restart the machinery but shall only permit restarting.
More details for the design and selection of electrical components and elements to achieve the
emergency stop function are provided in NFPA 79.
6.2.5.2.3 Precautions for the escape and rescue of trapped persons
Examples of precautions for the escape and rescue of trapped persons include
(a) escape routes and shelters in installations generating operator-trapping hazards;
(b) arrangements for moving some elements by hand, after an emergency stop;
(c) arrangements for reversing the movement of some elements;
(d) anchorage points for descender devices; and
(e) means of communication to enable trapped operators to call for help.
6.2.5.3 Other equipment, systems, and arrangements contributing
to safety
6.2.5.3.1 Provisions for machine maintainability
See Clauses 6.2.1.14 and 14.1 for provisions for machine maintainability.
6.2.5.3.2 Provisions for isolation and energy dissipation
Especially with regard to their maintenance and repair, machines shall be equipped with the technical
means to achieve isolation from energy source(s) and dissipation of stored energy as a result of the
following actions:
(a) isolating (disconnecting, separating) the machine (or defined parts of the machine) from all
energy sources;
(b) if necessary (e.g., in large machines or in assemblies of machines), locking (or otherwise securing)
all the isolating units in the isolating position;
(c) dissipating or restraining (containing) any stored energy that may give rise to a hazard; and
(d) verifying, by means of a safe working procedure, that the actions taken according to Items (a) to (c)
have produced the desired effect.
6.2.5.3.3 Provisions for easy and safe handling of machines and heavy
component parts
Machines and their component parts that cannot be moved or transported by hand shall be provided or
be capable of being provided with suitable attachment devices for transport by means of lifting gear.
Examples of these attachments or provisions include
(a) standardized lifting appliances with slings, hooks, eyebolts, or tapped holes for appliance fixing;
(b) appliances for automatic grabbing with a lifting hook when attachment is not possible from
the ground;
(c) guiding grooves for machines to be transported by a fork truck;
(d) indication on the machine itself and on some of its removable parts of the value of their mass
expressed in kilograms (kg); and
(e) lifting gear and appliances integrated into the machine.
Parts of machinery that can be removed manually in operation shall be provided with means for
their safe removal and replacement and should be marked with weight details.
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6.2.5.3.4 Provision for safe access to machinery
6.2.5.3.4.1
Machinery shall be so designed as to enable operation and all routine tasks relating to setting and/or
maintenance to be carried out, as far as possible, by a person remaining at ground level. Where this is
not practicable, machines shall have built-in platforms, stairs, or other facilities to provide safe access
for those tasks. Care should be taken to ensure that such platforms or stairs do not give access to danger
zones of machinery. Where less frequent access is required, fixed ladders with handrails can be used.
6.2.5.3.4.2
The walking areas shall be made from materials that remain as slip-resistant as practicable under
working conditions and, depending on the height from the ground, suitable handrails, posts and
toe boards, and handholds shall be provided.
6.2.5.3.4.3
In large automated installations, particular attention shall be given to safe means of access such as
walkways, conveyor bridges, or crossover points.
6.2.5.3.4.4
Means of access to parts of machinery located at a height shall be provided with a collective means
of protection against falls. As necessary, anchorage points for personal protective equipment against
falls from a height shall also be provided (e.g., in carriers of machinery for lifting persons or with elevating
control stations).
6.2.5.3.4.5
Openings shall, whenever possible, open towards a safe position. They shall be designed to prevent
hazards due to unintended opening.
6.2.5.3.4.6
The necessary aids for access shall be provided (e.g., steps, handholds), and control devices shall be
designed and located to prevent their use for this purpose.
6.2.5.3.4.7
When machinery for lifting goods and/or persons includes landings at fixed levels, such machinery shall
be equipped with interlocking guards to prevent falls when the platform is not present at the level.
Movement of the lifting platform shall be prevented while the guards are open.
6.2.5.3.5 Provisions for stability of machines and their elements
For provisions for stability of machines and their elements, see Clauses 6.2.1.15 and 6.2.2.4.
6.2.5.3.6 Provision of diagnostic systems to aid fault-finding and
rectification
For provisions of diagnostic systems to aid fault-finding and rectification, see Clause 6.2.1.9.14.
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7 Mechanical design and controls
7.1 General
7.1.1
Designers shall have followed the general principles laid down in Clause 5 of this Standard and shall
have taken into account the relevant standards for specific type(s) of machinery. When appropriate,
the end user shall ensure provisions are made to facilitate the fitting of alternative types of safeguarding
where variations in the tasks reduce the effectiveness of the existing safeguarding. The risk assessment
documentation shall be changed to reflect the change in safeguarding methodology.
7.1.2
Where specific applications require guards or safety devices not provided by the manufacturer, the user
shall ensure that appropriate safeguarding is installed. The user shall ensure written instruction is provided
for the inspection of these additional safeguards.
7.2 Mechanical restraint device
A mechanical restraint device is a device that applies mechanical restraint to a hazardous part of machinery
that has been set in motion due to failure of the machinery controls or of other parts of the machinery so
as to prevent a hazardous situation.
7.3 Down-stroking platens
7.3.1
Sudden loss of pressure at certain critical points in the hydraulic system of a down-stroking machine
can cause a machine member to fall under gravity. On small machines, the weight of the platen and speed
of descent may be insufficient to cause a hazardous situation, but on large machines protection against
such a failure should be provided by means of either of the following:
(a) one or more scotches, capable of supporting the weight of the machine member, shall be inserted
automatically when the member has returned to the top of its cycle (stroke); or
(b) a pilot operated check valve and counterbalance valve assembly shall be installed into the lower end
of the hydraulic cylinder.
7.3.2
Where a scotch operates in conjunction with an interlocking guard, the scotch should remain in position
until the guard is closed. The guard should then remain locked closed until the machine member has
returned to the top of its cycle (stroke) and the scotch is in place.
7.4 Particular measures for repetitive-cycle hand-fed machines
7.4.1 General
Piece-by-piece hand-fed machines shall be equipped with an anti-repeat system that forces the complete
stopping of the function at the end of the cycle before another start command may be accepted and
executed.
7.4.2 Random stop machines
Machines that can stop at any point of their cycles (friction brake, for example, without a precise stopping
point) shall be equipped with a brake monitor that immediately stops the function, inhibits all restart
commands, and signals when the stopping time or distance is exceeded.
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7.5 Rotating shafts, spindles, and couplings
Setscrews, bolts, or keys on any exposed revolving part of machinery shall be sunk, shrouded, or otherwise
guarded.
Guarding of the rotating shafts may be accomplished by means of
(a) fixed guards of solid construction;
(b) bellow-type guards; or
(c) telescopic-type guards.
7.6 Hydraulic and pneumatic systems
All components within the system shall operate within their manufacturer’s specification. All parts of the
system shall be protected against overpressure. The system shall be designed and constructed so that
components are located where they are accessible and can be safely adjusted and serviced. Adjustments
that cause a change within the machine shall be tamper-resistant to prevent unauthorized or accidental
use. Circuits shall be designed, constructed, and adjusted to minimize surge pressures. Surge pressure or
loss of pressure shall not cause hazards.
7.7 Electrical systems
Electrical equipment shall comply with the requirements of the Canadian Electrical Code, Part I and Part II,
as applicable, as well as pertinent regulations of the authority having jurisdiction.
7.8 Workholding devices
7.8.1 Energy loss during operation
Where energy-operated workholding devices are supplied, they shall be designed so that a hazardous
situation is prevented in the event of a failure of the energy source to the system, i.e., the workpiece
remains clamped.
7.8.2 Clamping for automatic machinery
The control system shall be interlocked to prevent the machinery from being operated until energy is
supplied to the workholding device and the workpiece is clamped. Where energy-operated workholding
devices are supplied, it shall have a means provided to check either a visual or audible indicator that
energy has been supplied and the clamp is on.
The clamping movement, if accessible, should not expose a gap of more than 6 mm or should be
guarded in such a manner that it is not possible to trap a hand, finger, or other body part.
7.8.3 Prevention of inadvertent unclamping of the workpiece
The design of the control system shall be such that the energy operating system for the workholding
device cannot be operated to unclamp the workpiece while it is hazardous to do so. In certain situations
there should also be an indication that the workpiece is actually clamped.
7.9 Lifting, handling, and transport
7.9.1
Machinery that cannot be moved or transported by hand shall be equipped or be capable of being
equipped with suitable attachment devices for transport by means of lifting gear. Transport personnel
shall be able to reach the attachment devices safely, or provision for automatic attachment should be
fitted. Taking into account the centre of gravity, the attachments shall be arranged so that the machinery
cannot be tipped during correct lifting. Weight details shall be given on the machine, on its packaging,
or on transport documentation.
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7.9.2
All machinery elements, including added fixtures, shall be provided with means for their safe removal
and replacement, unless their shape, size, and weight permit these operations to be carried out safely
by hand. Parts of machinery that can be removed in operation, e.g., tools and devices that on account
of their weight cannot be lifted manually, should be marked with weight details. These markings should
be affixed so that they are clearly legible and visible, whether the details refer to the removable part or
to the complete machine.
7.10 Lubrication
7.10.1
Excess lubricants shall be prevented from reaching the surrounding area and thereby creating a hazard.
7.10.2
On machines in which the failure of an automatic lubrication system could cause a hazard for the operator,
such a lubrication system shall incorporate an indication of its correct functioning and/or warning of a
malfunction. In addition, a means shall be provided to stop the machine as soon as practicable should the
automatic lubrication system fail.
7.11 Hygiene
Machinery used in certain industries, notably for the processing of food and pharmaceuticals, shall be so
designed that health hazards can be controlled during operation and that it can be readily cleaned
without risk of injury.
7.12 Safety colours and symbols
7.12.1
Where practicable, colours should be used to draw attention to a hazard. For example, certain parts of
machines should be painted a distinguishing colour that will only be visible when a hazardous situation is
present. Such finishes are required to be non-toxic when used in the food processing and pharmaceutical
industries.
7.12.2
If it is not practicable to apply a distinguishing colour to an element of the machine structure, then the
hazardous items themselves should be coloured; for example, where the machine structure adjacent to
the hazardous element is completely hidden by it. It is not necessary that the whole of the hazardous part
be coloured; it is sufficient to colour the ends of shafts, rims of pulleys, edges of blades, or other relevant
machine members.
7.12.3
Where safety colours and symbols are used, they shall adopt a bold, recognizable, consistent pattern
or symbol using standardized colours and should comply, where applicable, with CAN/CSA-Z321 and
CAN/CSA-Z431.
7.13 Operating stations
7.13.1
The controls shall be positioned relative to the machinery so that the operator has adequate vision for
control of the process being undertaken. The operator shall be provided with adequate room in his/her
working position and have all controls placed within comfortable range. Where it is necessary for an
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operator to stand or sit on machinery when it is being operated, a platform or seat shall have been
provided and so designed and situated as to protect an operator from any fixed or moving part that
may cause injury.
7.13.2
Seats shall be so designed as to provide adequate support and shall be fitted with back rests or so shaped
as to protect an operator against slipping from the seat. Footrests shall be provided, where necessary.
7.13.3
Access to hazardous parts of transfer mechanisms, conveyors, etc., will also require consideration, usually
on a larger scale than in the case of single operation processes. In large automated processes, particular
attention shall be given to safe means of access such as walkways, conveyor bridges, or crossover points.
7.14 Platforms and steps
7.14.1
Where work platforms are used, they shall have been so designed as to prevent hazards and provide a level
standing space of adequate size (and strength) with a firm foothold. The stepping areas shall be made
from materials that remain as slip-resistant as practicable under working conditions, and guard rails, posts,
and toe boards shall be provided as required by the authority having jurisdiction.
7.14.2
An access ladder with handholds and, where necessary, with a safety cage, or a stairway with handrails or
some other means shall be provided to give safe and convenient access.
7.15 Access for adjustment, lubrication, and maintenance
7.15.1
Machinery shall be designed to enable all routine adjustments, lubrication, and maintenance to be carried
out without removing safeguards and without extensive dismantling of machinery components. Ideally,
lubrication and routine maintenance facilities shall be incorporated outside the hazardous area, wherever
practicable.
7.15.2
All action points, i.e., those points where generally an external action is required to ensure the correct
operation of a lubrication system — e.g., filling with lubricant or actuation of a lever — shall be easily
accessible and situated so as not to cause a hazard. Where access for lubrication is difficult, facilities
for lubrication from a remote point or self-lubricated bearings shall have been provided.
7.15.3
Wherever frequent access to machinery elevated above or below floor level is required, machines shall
have built-in platforms, ladders, stairs, or other facilities to provide safe access for any adjustment,
lubrication, or maintenance, but users shall check that such platforms or ladders do not give access to
exposed hazardous parts of machinery.
7.15.4
During maintenance, if it is necessary to reach into the danger zone around moving parts, which would
otherwise be out of reach, either the machine shall be powered down and locked out or all the moving
parts shall be guarded against possible contact.
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7.16 Interlocking of pneumatic and hydraulic systems
Controls shall be adequately interlocked to prevent entry into a moving part/machine during its
operation, with the exception of machine entry for maintenance, where lockout procedures shall be
adhered to. Machine failures shall not create a hazard or injury to personnel upon either a loss or restored
condition of machine control. This may include, but not be limited to, any uncontrolled machine motion.
When pneumatic or hydraulic interlocking methods are used, they are to achieve the same level of safety
provided by electromechanical interlocking devices in accordance with Clause 9.
7.17 Emergency stop
7.17.1 General
7.17.1.1
The emergency stop shall be fully in accordance with NFPA 79 and ISO 13850, override all other machine
controls, cause all moving parts to stop, and remove drive power from the machine actuators.
Note: The emergency stop may be a category 0 or category 1 type stop as required by NFPA 79.
7.17.1.2
Each operator control station, including pendants, capable of initiating machine motion shall have a
manually initiated emergency stop device.
7.17.2 Emergency stop device design
Push-buttons that activate an emergency stop circuit shall be
(a) red in colour with a yellow background;
(b) unguarded;
(c) palm or mushroom head type;
(d) the type requiring manual resetting; and
(e) installed such that resetting the button shall not initiate a restart.
7.17.3 Emergency stop pull-cords
7.17.3.1
Emergency stop pull-cords shall be located in such a manner as to be clearly visible, readily accessible, and
so positioned that they can be used, not only near the operator’s normal control station, but at other
appropriate points.
7.17.3.2
The pull-cord system shall be designed and arranged so that it operates the associated switching device
and generates the emergency stop signal when
(a) the pull-cord is pulled in any direction, a perpendicular pulling force of less than 200 N is applied to
the pull-cord, and a perpendicular deflection of the pull-cord of less than 400 mm occurs;
(b) the pull-cord breaks; or
(c) the failure of a single spring occurs (see Figure B.1).
7.17.3.3
In addition, the pull-cord shall be able to withstand without breaking a tension force 10 times higher
than that necessary for generating the emergency stop signal.
7.17.3.4
Where, in the case of long pull-cords, more than one switching device is necessary, a visual indicator shall
be incorporated to show which device has been operated.
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7.17.3.5
Pressure-sensitive cables shall be used only in conjunction with control systems designed to switch off the
machinery when malfunctions are detected which lead to open or short circuits.
7.18 Cables and pipes
Service pipes and cables shall be placed either below ground clear of the machinery foundations and
provided with covers of adequate strength, or at such a height as to have clear headroom; the traversing
of gangways shall be avoided, if possible.
7.19 Lighting
7.19.1
Task lighting on the machine for the illumination of the work area shall be provided when the construction
of the machine and/or its guards renders the normal lighting inadequate for the safe and efficient
operation of the machine. Task lighting shall also be provided in areas of regular maintenance that are
likely to be poorly lit (e.g., the inside of certain electrical compartments where electrical isolation is
necessary for access). Electrical wiring, etc., for such lighting shall comply with the requirements of the
Canadian Electrical Code, Part I.
7.19.2
Fluorescent-type lighting may be used, provided that any stroboscopic effects do not create a hazard.
If the position of the lighting has to be adjusted, its location shall be such that it does not present a
hazard to the machine operator while making the adjustment.
7.20 Interaction with other machinery
7.20.1
A machine shall be installed with due regard to its interaction with other machines and the requirements
of the process.
7.20.2
Space shall be provided around each machine to allow clear separation from passing traffic and for the
storage of tools and work in progress. All phases of machine life shall be considered, including cleaning,
maintenance, etc., as well as normal operation (see Clause 4.2.3). Where workpieces such as stock bars
overhang the machine, they shall be included when determining the floor space occupied. If work is to be
carried out on live electrical equipment, the width of passageways shall conform to relevant occupational
health and safety legislation.
7.21 Coolant and swarf
Machinery shall be designed, as far as is reasonably practicable, to contain coolant and/or swarf so as not
to expose persons to additional hazards.
7.22 Electromagnetic interference
Designers and manufacturers shall ensure that the electrical equipment of the machine does not generate
electromagnetic disturbances above levels that are appropriate for its intended places of use. In addition,
the electrical equipment shall have an adequate level of immunity to electromagnetic disturbances (see
Clause 13.2) so that it can operate in its intended environment.
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7.23 Controls for machinery setting or adjustment and for feeding
material where safeguards are displaced or removed
7.23.1 General
Controls for starting or stopping a machine shall be clearly marked (see also CAN/CSA-Z431).
Where a safeguard has to be displaced or removed for setting or adjusting machinery, or feeding
material, and it is necessary for the purpose of these operations for the machinery to be in motion,
the individual(s) shall be protected by one of the following types of controls:
(a) hold-to-run control(s):
(i)
two-hand controls;
(ii) enabling devices; and
(iii) pendant controls;
(b) limited movement device(s):
(i)
timed impulse device(s); and
(ii) controlled movement device(s); or
(c) handles and handwheels.
7.23.2 Hold-to-run control
A hold-to-run control shall only permit movement of the machinery as long as the control is held in a set
position. The control shall return automatically to the stop position when released. Where the machinery
runs at crawl speed, this speed shall be kept as low as practicable.
A two-hand control may be used as a hold-to-run control.
A hold-to-run control for remote operation of machinery shall be used only where it is not practicable to
provide effective guarding and where there is no risk of injury from overrun of the hazardous parts when
the control has been released.
7.23.3 Enabling devices
7.23.3.1
An enabling device is an additional manually operated 2- or 3-position control device used in conjunction
with a start control and which, when continuously actuated in one position only, allows a machine to
function. In any other position, motion is stopped or a start is prevented.
7.23.3.2
Enabling devices shall have the following features:
(a) They shall be connected to a Category 0 or a Category 1 stop (see NFPA 79).
(b) They shall be designed in accordance with ergonomic principles:
(i)
position 1 is the off function of the switch (actuator is not operated);
(ii) position 2 is the enabling function (actuator is operated); and
(iii) position 3 (if used) is the off function of the switch (actuator is not operated past its
mid position).
(c) Three-position enabling devices shall be designed to require manual operation in order to reach
position 3.
(d) When returning from position 3 to position 2, the function shall not be enabled.
(e) An enabling device shall automatically return to its off function when its actuator is not manually
held in the enabling position.
Note: Tests have shown that human reaction to an emergency may be to release an object or to hold on tighter,
thus compressing an enabling device. The ergonomic issues of sustained activation should be considered during design
and installation of the enabling device.
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7.23.4 Limited movement devices
7.23.4.1 General
A limited movement device is a control system that physically constrains a moving machine part to a
limited amount of travel on each occasion that the machinery control is operated. Further movement
of the machinery is precluded until there is a subsequent and separate operation of the control.
The fitting of a limited movement device will inevitably result in a greater number of start/stop
operations. Therefore, care shall be taken to ensure that the machine shall
(a) be mechanically robust enough to withstand the possible extra duty;
(b) have drive motors of adequate capacity such that they will not overheat;
(c) have rated contactors and relays adequate for this type of application;
(d) be fitted with a brake; if the load on the machinery varies during the process cycle, a brake will
almost certainly be necessary if effective limited movement control is to be attained;
(e) have control operations readily distinguishable where reversal of motion is possible; and
(f) be installed such that the controls are not easily defeatable by the operator.
7.23.4.2 Types of limited movement devices
Installation should be such that the operator cannot readily tamper with the controls. There are two types
of limited movement devices that may be used:
(a) Time impulse device. The method adopted is to close a contactor or relay supplying the drive motor
or clutch for a predetermined time.
(b) Controlled movement device. Controlled movement devices are designed to give a reasonably
accurate predetermined movement in which stopping is effected as soon as the required movement
has taken place. Once properly set, such devices are affected only to a very limited, and probably
negligible, extent by ambient temperature, varying load on the machine.
7.23.4.3 Handles and hand-wheels
Where hand-wheels have not been designed not to rotate when the energy drive is operating, they shall
be either of the solid type without spokes or projections and/or provided with handholds of restricted size.
7.24 Safeguard-operator interface principles
All guards shall
(a) prevent the entry of hands, fingers, or other parts of the body into a point of hazard;
(b) not create additional hazards between the guard and the moving parts;
(c) not cause undue obstruction to the view of the production process;
(d) be installed such that they do not cause undue interference with the activities of the worker during
operation, maintenance, etc. A proper installation would reduce any incentive to circumvent or
override the safeguard;
(e) be permanently affixed to the machine, or, when this is not possible, to the same surface to which
the machine is fixed. The removal of a fixed guard should require the use of tools. Fasteners should be
of the captive type and stay with the guard;
(f) be provided where openings intended to permit lubrication, adjustment, inspection, etc., cause an
additional hazard; and
(g) protect an operator and others in the vicinity from materials, workpieces, chips, liquids, dust, fumes,
gases, etc., that may be ejected, dropped, or emitted from a machine and that may present a hazard.
7.25 Warning signals
On installations where the main operating station or start control is in a position from which the hazardous
parts of the machinery or people in the vicinity cannot be seen clearly, audible and visual warnings shall be
provided. Such warnings shall be integrated through a suitable interlock for a predetermined time before
the machinery starts to operate. Adjacent machines shall be provided with distinguishable audible signals.
These devices are not to be used in substitution for physical safeguards.
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On installations where malfunction of the machinery creates a hazardous situation, suitable warning
signals shall be provided. These signals shall be given automatically and shall be both audible and visual.
Where the machine does not have the capability of detection of a hazardous malfunction due to a
hazardous situation, a manual signal that is both audible and visual shall be provided.
Note: This provision is only applicable where a malfunction of the machinery creates a hazardous situation to any person.
7.26 Indicators
Where necessary, a qualitative, quantitative, or check reading indicator shall have been provided to
warn of a hazardous situation. Such indicators shall be designed to minimize the risk of failing to danger.
Explanations of these indicators are as follows:
(a) qualitative: shows a satisfactory or unsatisfactory state, e.g., a temperature gauge that indicates
cold-normal-hot;
(b) quantitative: provides numerical data and as such requires precision in reading, e.g., a pressure
gauge. A quantitative indicator shall not be used if a qualitative one would suffice; and
(c) check reading: gives information automatically or when demanded as to the state of the equipment,
e.g., an indicator light and/or audible alarm. See CAN/CSA-Z431 for use of colours of indicator
lamps.
Note: Audible and visual warnings are not a substitution for physical safeguards.
7.27 Braking systems
7.27.1 General
Clause 7.27 applies whenever the braking system is integral for the protection of any person. Braking
systems shall be so designed as to bring hazardous moving parts to rest within a consistent time interval.
As the braking capacity required is related to the momentum of the moving parts, their momentum shall
be kept as low as the application permits, and, in particular, the possibility of inserting a clutch mechanism
shall be considered as a means of limiting the momentum to be dealt with by the brake. Rotating parts
and equipment fastened to rotating parts shall be so secured as to prevent dislodgement in consequence
of the brake action. Precautions shall be taken to prevent disengagement of screwed components due to
reversed torque following brake application.
Braking systems shall be designed to minimize the risk of failure to danger.
7.27.2 Mechanical (friction) braking systems
7.27.2.1
Clause 7.27.2 applies whenever the braking system is integral for the protection of any person. Application
of mechanical (friction) braking systems shall be independent of the energy source.
7.27.2.2
Brakes shall be of such capacity as to perform satisfactorily under conditions of maximum sustained use.
The design shall provide for adequate dispersal of heat to prevent excessive temperature rise of
the working parts.
7.27.2.3
The arrangements for guiding shall be such as to minimize the risk of binding.
7.27.2.4
Where the effectiveness of braking may be adversely affected by contamination and by the ingress
of moisture or oil, consideration shall be given to
(a) selecting an appropriate friction material;
(b) providing an effective housing to prevent ingress; and
(c) monitoring braking efficiency and supplying control systems that prevent motion when efficiency
is below the acceptable level (as specified by the brake manufacturer).
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7.27.2.5
When springs are used, they shall be of the compression type, safety rated, and of sufficient strength
to secure prompt and effective brake application. Any set of springs used on a brake shall be closely
uniform in dimension, quality, and rating. A single spring shall not be relied upon unless equivalent safety
is ensured by other means. The means for loading the springs shall be such that, when correctly adjusted,
the spring anchorages can be locked to prevent risk of slackening back.
7.27.2.6
Adequate instructions concerning the setting of the brake shall be available. These shall include the
(a) length to which the spring(s) shall be compressed; and
(b) setting of the operating mechanism.
7.27.2.7
When hydraulic or pneumatic means are used to apply mechanical brakes, an accumulator/reservoir,
connected as close as possible to the brake, shall be provided to ensure a sufficient supply of fluid in
the event of failure of the main supply. The accumulator/reservoir shall have a low-pressure device to
switch off the machinery if the pressure in the accumulator/reservoir falls below a safe limit, and the
feed shall be fitted with a non-return valve.
7.27.3 Electrodynamic braking systems
7.27.3.1 General
Clause 7.27.3 applies whenever the braking system is integral to the safety of any person. Electrodynamic
braking systems shall be connected in such a way that their energy source is maintained when emergency
stop controls are used.
One of the following methods shall be used for electrodynamic braking systems:
(a) reverse plugging;
(b) direct current injection;
(c) regenerative braking for alternating current motors; or
(d) regenerative braking for d.c. motors.
7.27.3.2 Reverse plugging
This clause applies whenever the braking system is integral to the safety of any person. Reverse
plugging is a method of braking whereby the electrical connections to a motor are changed so that
a reverse torque is applied and the machine is brought rapidly to rest. The change over contactor
shall have been so controlled that it will open when the machinery stops, otherwise the machinery
will restart in the reverse direction.
7.27.3.3 Direct current injection
This clause applies whenever the braking system is integral to the safety of any person. Direct current
injection consists of disconnecting the motor stator windings from the a.c. supply and reconnecting
them to a d.c. supply. This has a powerful braking effect and is better than reverse plugging because there
is no tendency to restart in the reverse direction.
7.27.3.4 Regenerative braking for alternating current motors
(capacitor braking)
This clause applies whenever the braking system is integral to the safety of any person. Regenerative
braking for a.c. motors consists of the following:
(a) Disconnecting the motor from the a.c. supply and reconnecting it to a capacitor bank. The capacitors
help to maintain the self excitation of the motor and there is an induced braking effect.
(b) Improving the braking effect during the final stages of decelerating by short-circuiting the motor
terminals.
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7.27.3.5 Regenerative braking for direct current motors
This clause applies whenever the braking system is integral to the safety of any person. Regenerative
braking for d.c. motors consists of reconnecting the motor so that it acts as a generator to supply a load.
The load may be a resistor or the main power supply.
7.27.3.6 Emergency braking
Emergency braking shall be designed to fail in the safe mode and be suitably rated for the application
(e.g., multiple spring-sets).
7.28 Clutches
This clause applies whenever the operation of the clutch is integral to the safety of any person.
Where actuated by mechanical or other means, disengagement of the clutch should not depend
on the maintenance of the energy source. This is commonly achieved by using compression-type
springs. The springs shall be safety rated and of sufficient strength to secure prompt and effective
clutch disengagement. Any set of springs used on a clutch shall be closely uniform in dimension,
quality, and rating. A single spring shall not be relied upon unless equivalent safety is provided by
other means. The means for loading the springs shall be such that, when correctly adjusted, the
spring anchorages can be locked to prevent risk of slackening back.
7.29 Safety catches, overrun, runback, and fall-back protection devices
Safety catches, overrun, runback, and fall-back protective devices shall be applied where there is a risk of
personnel injury due to potential travel of machine components beyond their normal stopping position.
7.30 Counterweights and similar devices
Counterweights that may fall upon or trap persons shall be suitably safeguarded. The movement of
the counterweights should be safeguarded as far as necessary to provide complete protection against
injury, in particular, in the event of an energy system failure.
Duplication of the flexible connections (chain or cable) between the mass and its balance weight(s)
is good practice, provided that each connection is sufficiently strong to take the full load.
Similar precautions are necessary on other weights, e.g., those provided for tensioning ropes and belt
conveyors, where such weights move when the machinery is operated. In these cases, provision shall be
made to maintain safety in the event of rope or belt failure.
8 Performance requirements for safety control systems
8.1 General
8.1.1
Based on the risk assessment (see Clauses 5.1 to 5.5) of the machine, the designer shall determine the
contribution to the reduction of risk (see Clause 5.6), which needs to be provided by each safety-related
part of the control system (see Clauses 6.2.1.8 and 8.2). This contribution does not cover the overall risk of
the machinery under control, e.g., the overall risk of a mechanical press or washing machine, but that part
of risk reduced by the application of particular safety functions. Examples of such functions are the stop
function initiated by using an electro-sensitive protective device on a press, or the door-locking function of
a washing machine.
8.1.2
The greater the dependence of risk reduction upon the safety-related parts of control systems, the higher
the required ability of those parts to resist faults. This ability — in the understanding that the required
function is performed — can be partly quantified by reliability values and by a fault-resistant structure.
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Both reliability and structure contribute to this ability of safety-related parts to resist faults. Specified
resistance to faults can be achieved by specifying levels of reliability of components and/or with improved
structures for the safety-related parts. The contributions of reliability and of structure can vary with the
technology used.
8.2 Safety control system performance criteria
8.2.1 General
Safety control systems (electric, hydraulic, pneumatic) shall meet one of the performance criteria listed in
Clauses 8.2.2 to 8.2.5.
8.2.2 Simple
Simple safety control systems shall be designed and constructed using accepted single channel circuitry
and may be programmable.
Note: This type system should be used for signaling and annunciation purposes only.
8.2.3 Single channel
Single channel safety control systems shall
(a) be hardware based or comply with Clause 8.3;
(b) include components, which should be safety rated; and
(c) be used in compliance with manufacturer’s recommendations and proven circuit designs
(e.g., a single channel electro-mechanical positive break device that signals a stop in a
de-energized state).
Note: In this type of system, a single component failure can lead to the loss of the safety function.
8.2.4 Single channel with monitoring
8.2.4.1
Single channel safety control systems with monitoring shall
(a) include the requirements for single channel;
(b) be safety rated; and
(c) be checked (preferably automatically) at suitable intervals.
8.2.4.2
The check of the safety function(s) shall be performed
(a) at machine start-up; and
(b) periodically during operation (preferably at each change in state).
The check shall either allow operation if no faults have been detected or generate a stop if a fault
is detected. A warning shall be provided if a hazard remains after cessation of motion.
The check itself shall not cause a hazardous situation. Following detection of a fault, a safe state shall
be maintained until the fault is cleared.
Note: In this type of system, a single component failure may also lead to the loss of the safety function.
8.2.5 Control reliable
Control reliable safety control systems shall be dual channel with monitoring. Such systems shall be
designed, constructed, and applied such that any single component failure (including monitoring)
shall not prevent the stopping action of the equipment.
These safety control systems shall be hardware based or comply with Clause 8.3 and include automatic
monitoring at the system level conforming to the following:
(a) The monitoring shall generate a stop if a fault is detected. A warning shall be provided if a hazard
remains after cessation of motion.
(b) Following detection of a fault, a safe state shall be maintained until the fault is cleared.
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(c) Common mode failures shall be taken into account when the probability of such a failure occurring is
significant.
(d) The single fault should be detected at time of failure. If not practicable, the failure shall be detected
at the next demand upon the safety function.
(e) These safety control systems shall be independent of the normal program control (function) and shall
be designed to be not easily defeated nor easily bypassed without detection.
8.3 Safety-related software- and firmware-based controllers
Software- and firmware-based controllers used in place of hardware-based components with safety-related
devices shall
(a) be designed such that any single safety-related component or firmware failure shall
(i)
lead to the shutdown of the system in a safe state; and
(ii) prevent subsequent automatic operation until the component failure has been corrected;
Note: Firmware is that executive control program code provided by the manufacturer of the component in a
non-volatile internal storage mode and is not changeable by the user.
(b) supply the same degree of safety achieved by using hardwired/hardware components in accordance
with Clause 8.2.5. For example, this degree of safety may be achieved by using microprocessor
redundancy, microprocessor diversity, and self-checking; and
(c) be certified by a Nationally Recognized Testing Laboratory (NRTL) or Standards Council of Canada
(SCC)-accredited testing laboratory to an approved standard applicable for safety devices.
8.4 Control comparison (ANSI vs CEN)
ANSI/CSA*
index
Safeguard performance
Circuit
performance
CEN/ISO†
category
R1
Hazard elimination or hazard
substitution
Control reliable
Category 3 and 4
R2A
Engineering controls preventing access
to the hazard, or stopping the hazard,
e.g., interlocked barrier guards, light
curtains, safety mats, or either
presence-sensing device
Control reliable
Category 3 and 4
Single channel;
with monitoring
Category 2
Single channel
Category 1
Single channel
Category 1
Simple
Category B
Simple
Category B
R2B
R2C
R3A
R3B
R4
Non-interlocked barriers, clearance,
procedures, and equipment
Awareness means
*Based on ANSI B11 TR3.
†Based on ISO 13849-1.
Note: There is no intent to imply that circuit performance classifications are equivalent to CEN/ISO machinery
categories.
9 Performance requirements for safeguarding devices
9.1 General
Safeguarding devices shall be designed and constructed with the goal of preventing any part of the
body from reaching a danger point or area. Machine guards should take into account the physical
characteristics of the people involved and, in particular, their abilities to reach through openings
and over or around barriers or guards. The performance requirements of these devices are described in
Clauses 9.2 to 9.4. See Clause 10 for their application requirements.
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9.2 Barrier guards, fixed and interlocked
Barriers shall
(a) be constructed to withstand operational forces and environmental conditions;
(b) be free of sharp edges and projections and not themselves create a hazard; and
(c) provide a means for secure attachment.
9.3 Interlocking safeguarding devices
9.3.1 General
Safeguarding devices that are used for interlocking shall
(a) have a key, plug, or actuating device that is not easily duplicated;
(b) be tamper-resistant and not be defeated intentionally without tools;
(c) provide a means for secure attachment; and
(d) be provided with documentation stating:
(i)
the standards with which the device is compliant;
(ii) the standards against which the device is independently certified; and
(iii) that the control system performance complies with the criteria for one of the four control
systems types listed in Clause 8.2.
9.3.2 Mechanical devices
Mechanical devices (typically including, but not limited to, transfer or captive/trapped key interlocking)
shall
(a) have a physical link between the energy source of a hazard and the locking mechanism to allow the
removal of the key or actuating device only when the hazard has been controlled. The removal of the
key or actuating device shall prevent reinstatement of the hazard; and
(b) provide a mechanical lock for the guard at the point of access, which can only be unlocked by the key
or actuating device described in Item (a). This lock shall trap or retain the key or actuating device
when the guard is opened, and only release the key or actuating device when the guard is closed and
locked.
9.3.3 Electrical devices
Electrical devices, with or without guard locking (including, but not limited to, safety switches, captive key
systems, and magnetically actuated switches), shall
(a) be provided with detailed information about the point in the travel of the actuating device where
the switching action of the contacts occurs;
Note: Depending on the switch and the installation, the amount of travel before switching may differ significantly.
For example, without the information, a hinge-mounted switch may be improperly installed such that the door could
open and a person could enter before switching occurs.
(b) either be in compliance with Clause 8.2.5, and upon failure detection, successive automatic
operation shall be prevented until the component failure has been corrected or shall be designed for
positive opening (positive break) operation such that opening the contacts signals a stop; and
Note: Positive opening (positive break) operation is the full separation (opening) of a closed contact through
a non-resilient linkage (e.g., not dependent on springs) due to movement from the home (engaged) position. (See
Figure 13.)
(c) in the case of guard-locking devices, hold the guard closed and locked until the hazard has ceased.
These devices, when provided, shall provide a method to
(i)
manually unlock the device in the event of power failure; and
(ii) monitor the state of the locking mechanism. The manufacturer shall separately state the
safety controls performance, in accordance with Clause 8.2, of the locking portion of the
guard-locking device.
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9.4 Requirements for other safeguarding devices that signal a stop
9.4.1 General
Safeguarding devices that initiate a stop signal shall
(a) be accompanied with documentation stating
(i)
the standards that the product meets;
(ii) any standards that the product is independently certified to meet; and
(iii) the safety control system performance of the product in accordance with Clause 8.2;
Note: The IEC 61496 (formerly EN 50100) series of Standards were developed to cover some of these devices. They
should be used as appropriate compliance references.
(b) provide a means for a readily observable indication that the device is operating;
Note: Indicators are not necessarily required on sensing component(s) (for example, switches) that may be used
to signal a stop or as inputs to a muting control.
(c) not be adversely affected by the environmental conditions for which the system is intended;
(d) have a maximum response time that shall not be affected by the object sensitivity adjustments
or environmental changes;
(e) provide a means for secure attachment; and
(f) provide a means to restrict unauthorized adjustments or settings (hardware/software).
Note: These requirements may be accomplished by, but are not limited to, the use of key-operated controls, controls located
under lockable covers, passwords, etc.
9.4.2 Safety light curtains/screens
Safety light curtains/screens shall comply with the requirements of Clause 9.4.1. In addition, they shall
(a) comply with IEC 61496, Parts 1 and 2;
(b) be marked/labelled with
(i)
maximum response time;
(ii) maximum angle of divergence/acceptance at maximum gain;
(iii) minimum object sensitivity; and
(iv) protected height;
(c) indicate if blanking is being used; and
(d) provide for a method to prevent or detect unwanted reflections (e.g., optical short circuits).
Note: Methods can include the overall effective beam pattern, the overall angle of divergence/acceptance at
maximum gain, or a test procedure to detect the occurrence.
9.4.3 Area scanning safeguarding devices
Area scanning safeguarding systems shall comply with the requirements of Clause 9.4.1. In addition,
such systems shall
(a) be marked/labelled with
(i)
maximum response time;
(ii) maximum safeguarding range;
(iii) maximum field of view in degrees; and
(iv) range (linear and angular) and response time for an object sensitivity of 70 mm (2.75 in);
(b) not present a hazard (e.g., comply with IEC 60825 for eye safety in the case of lasers);
(c) have an identified total tolerance in the range measurement;
(d) provide an operating mode or method to allow the user to comply with Clause 10.5(d) for verified
detection area; and
(e) provide information on the detection capabilities of the device with respect to the reflectivity of an
object versus the distance to the object.
9.4.4 Radio frequency (RF)/capacitance safeguarding devices
RF/capacitance safeguarding devices shall comply with the requirements of Clause 9.4.1. In addition,
such devices shall
(a) have a sensitivity adjustment to allow for authorized adjustment of the field by qualified personnel;
(b) not allow the adjusted field to decrease in sensitivity below the established level;
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(c) be marked/labelled with
(i)
maximum response time, including output devices; and
(ii) minimum object sensitivity at maximum range;
(d) have an identifiable minimum object sensitivity and range that is not affected by ambient and
environmental conditions;
(e) provide an operating mode or method to allow the user to comply with Clause 10.5(b) for verified
sensitivity setting;
(f) not be adversely affected by external fields (e.g., weld busses, portable hand-held VHF/UHF radios, or
cellular telephones); and
(g) comply with sources of electromagnetic or radio frequency interference (EMI/RFI).
9.4.5 Safety mat systems
9.4.5.1
Safety mat systems consist of safety mat(s), wiring from the mat to the mat control, and a mat control.
Such systems shall
(a) be in accordance with ISO 13856, Part 1;
(b) use system controls and wiring between the control and the mat complying with Clause 9.4.1; and
(c) have the safety mat controls marked/labelled with maximum response time.
9.4.5.2
Safety mats shall
(a) be accompanied with documentation stating the standards that the product meets and any
standards that the product is independently certified to meet;
(b) be in accordance with Clause 9.4.1, Items (c) to (f);
(c) have an identifiable sensing field;
(d) have a minimum object sensitivity that detects 30 kg (66 lb) weight on an 80 mm (3.125 in) diameter
circular disk anywhere on the mat sensing surface;
(e) provide a means to retain minimum object sensitivity at the area where two mats are intended to be
joined together to form a single sensing surface, as measured above; and
(f) be manufactured to prevent any reasonably foreseeable failures (i.e., oxidation of the contact
elements) if such failure could cause a loss in sensitivity within the sensing field.
9.4.6 Single and multiple beam safety systems
Single and multiple beam safety systems shall be in accordance with Clause 9.4.1. In addition, such
systems shall
(a) be in accordance with IEC 61496, Part 2;
(b) be marked/labelled with
(i)
maximum response time;
(ii) maximum angle of divergence/acceptance at maximum gain; and
(iii) protected height and number/location of beams (fixed multiple systems only);
(c) only respond to their intended source of transmitted light or signal; and
(d) provide for a method to prevent or detect unwanted reflections (e.g., optical short circuits).
Note: Methods can include the overall effective beam pattern, the overall angle of divergence/acceptance at
maximum gain, or a test procedure to detect the occurrence.
9.4.7 Two-hand control systems
Two-hand control systems, when used for safeguarding, shall be in accordance with Clause 9.4.1.
In addition, such systems shall
(a) be designed to prevent accidental or unintentional operation;
(b) ensure that the individual operator’s hand controls are arranged by design, construction, or
separation so as to require the use of both hands within 500 ms to initiate/cycle the machine/system;
(c) be designed to require the release of all operator’s hand controls and the re-activation of all operator’s
hand controls before a machine/system cycle can be initiated; and
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(d) ensure that a stop signal is issued if one or both hands are removed from the controls during the
hazardous portion of a cycle.
10 Application requirements for safeguarding devices
10.1 General
Safeguarding devices shall be designed, constructed, installed, and maintained to ensure that personnel
cannot reach over, under, around, or through the device undetected to reach the hazard.
10.2 Barrier guards, fixed and interlocked
10.2.1 General
Barriers shall
(a) prevent access to a hazard;
(b) be constructed to withstand operational and environmental forces;
(c) be free of sharp edges and projections and not themselves create a hazard;
(d) be in accordance with Table 3 (see also Annex C) for opening size and distance from a hazard;
(e) require the use of tools to remove any fixed portion;
(f) be positioned so that the
(i)
bottom of the barrier is no more than 0.15 m (6 in) above adjacent walking surfaces; and
(ii) top of the barrier is no lower than 1.8 m (72 in) above adjacent walking surfaces unless
additional safeguarding devices are installed to prevent or detect access to the hazard.
The area between top and bottom shall be completely filled or shall be in accordance with Table 3
(see also Annex C); and
(g) contain parts and tooling (e.g., loose objects, flying projectiles) where this possibility exists.
Note: Barriers installed around material handling machinery need to be high enough to prevent any part from being thrown
over the barrier. This precaution may not be necessary if the equipment is equipped with effective part retention hardware
such as locking or over centre closing clamps.
10.2.2 Barrier guards, interlocked
Interlocked guards (barriers) consist of a barrier and an interlocking means that allow the barrier to
be opened.
10.2.3 Guard (barrier) portion
The guard (barrier) portion of the interlocked barrier shall be designed, installed, applied, and maintained
so that when used, it
(a) is in accordance with Clause 10.2.1;
(b) is installed at a safe distance (see Annex C), but no closer than the distances listed in Table 3;
(c) opens laterally or away from the hazard, and not into the safeguarded space, and cannot close by
itself and activate the interlocking circuitry;
(d) is not adversely affected by the environmental conditions; and
(e) is tamper-resistant and cannot be defeated intentionally without tools.
10.2.4 Interlocking portion
Each interlocking portion of the interlocked barrier shall be selected such that
(a) it provides two sets of contacts for circuit integration in accordance with Clause 9.4.6, unless a risk
assessment is performed such that the use of a device with one set of contacts is determined to be
acceptable;
(b) magnetic switches shall be magnetically coded to reduce the possibility of defeat or interference
and allow automatic monitoring to detect faults with the sensor;
(c) it is not adversely affected by the environmental conditions of the application; and
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(d) the interlocking portion of the interlocked barrier shall be installed, applied, and maintained so that
(i)
switches designed with a positive opening operation (see Clause 9.3.3(b)) shall be mounted in
a positive mode, such that when the actuator is disengaged or moved, the motion forces a
non-resilient linkage to open the normally closed (break) contact, which is used for the safety
stop circuit (see Figure B.13);
(ii) switches that are not positive opening/direct drive type shall be automatically monitored to
detect faults with the switches or its installation (e.g., magnetic switches, limit switches, etc.);
(iii) the safeguarding device (e.g., safety switch) shall not be used as an end of travel stop;
(iv) the safeguarding device is tamper-resistant and cannot be defeated without tools;
(v) the hazard being guarded cannot be placed in automatic operation until the interlocked barrier
is closed, and will issue a stop if the interlocked barrier is opened while the hazard is present;
(vi) closing the interlocked barrier shall not, by itself, restart automatic operation;
(vii) resuming automatic operation shall require a deliberate action outside the safeguarded space;
(viii) it is capable of being easily unlocked from the inside of the safeguarded space, with or without
power available, when the possibility of full body access exists; and
(ix) spare keys and actuating devices shall be supervisory controlled and not readily available.
Note: If spare keys and actuating devices are in demand for the purpose of defeating the safeguard, the design of the
overall safety scheme should be reviewed for deficiencies.
10.3 Requirements for other safeguarding devices that signal a stop
Safeguarding devices that initiate a stop signal shall
(a) be interfaced with the machine control system such that the detection of an intrusion shall cause
stopping of the hazardous motion;
Note: This refers to installations that signal the hazard to cease.
(b) be installed and arranged in accordance with Clause 9.2 so that persons cannot enter the hazardous
area without the intrusion being detected, and cannot reach a hazard before the hazardous
conditions have ceased (see also Annex C);
Note: Consideration of safety distance may not be required per Clause 10.11 when PSSD(s) are solely used to prevent
start/restart or solely used for clearance safeguarding.
(c) not allow the restart of automatic operation by the removal of the intrusion without a deliberate
action outside the safeguarded space;
(d) provide for control over adjustments or settings being made by other than authorized personnel; and
(e) have a readily observable indication that the device is functioning.
Note: Indicator lamps should be provided for all presence-sensing devices to indicate that the device is functioning.
The lights may be integral to the device or part of the interface to the machine control.
Where colour blindness is a consideration, unambiguous positioning, patterning, labelling, or flashing of the indicator
may be an effective method of providing indication.
10.4 Safety light curtains/screens
Safety light curtains/screens shall
(a) meet the requirements of Clause 10.3;
(b) be installed at a safety distance that accounts for the increased object sensitivity when blanking
(fixed or floating) is used unless the opening is completely obstructed;
(c) visibly indicate the fixed blanked area, or the user shall verify that blanking is being used (or not used)
as intended, including the number, size, and location of the blanked beams;
(d) visibly indicate the number of floating beams or object sensitivity, otherwise the user shall verify that
floating blanking is being used as intended; and
Note: Fixed and floating blanking creates holes in the light curtain’s coverage, which are needed in some applications.
If an obstruction does not fill the “holes”, then the light curtain is installed at a greater safety distance due to the
increased object sensitivity. Without visible indication of the blanked area or the number of floating beams enabled,
the configuration may be changed with indication. If only one floating beam is allowed, a single specific floating beam
indicator would indicate the number of floating beams. Although the changes would require access, it is desirable to
verify that the installation integrity is as expected (see Figure 4).
(e) be installed so reflective surfaces shall not cause the device to fail to respond to the presence
of personnel.
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10.5 Area scanning safeguarding devices
Area scanning safeguard devices shall
(a) meet the requirements of Clause 10.3;
(b) be installed for a safety distance and detecting plane height that accounts for the detection zone’s
maximum object sensitivity and also includes the device’s total range measurement tolerance in
the safety distance calculation (see Clause 10.11);
Note: Object sensitivities greater than 70 mm may not detect ankles, so the height above floor is an important
installation consideration.
(c) have a visibly identifiable detection area;
Note: Some installations should have the detection area visibly marked on the floor.
(d) be tested to ensure that the device is able to detect all objects and personnel entering the detection
area; and
Note: For example, dark clothing may be detected only with devices having specific diffused reflectance detection
capabilities. These devices operate on a principle of transmitting beams(s) of light to form a detection zone. When an
object enters the detection zone, it reflects the transmitted light back to the device, which then evaluates the object’s
position. The amount of reflected light (degree of reflectance in per cent) that can be reliably detected typically ranges
from 1.8% to over 90%.
(e) have the detection area verified upon installation, replacement, or changes within the detection area
for proper size and coverage before the device will allow the hazardous motion to start or restart.
Note: This verification can be accomplished manually by
(a) using a programming device;
(b) verifying the marked or intended detection area; or
(c) using an operation mode commonly called “test-on-startup”, which may require an intrusion into the detection
area before the device can be reset.
This verification can also be accomplished automatically if the control system can identify that the device has not
been moved, relocated, or replaced.
10.6 Radio Frequency (RF)/capacitance safeguarding devices
RF/capacitance safeguarding devices shall
(a) meet the requirements of Clause 10.3;
(b) have their sensitivity properly set; and
(c) be verified, by the user, for proper sensitivity adjustment setting on a routine basis.
10.7 Safety mat systems
Safety mat systems shall
(a) meet the requirements of Clause 10.3;
(b) be of sufficient size and geometry to detect intrusion from all places of access;
Note: See Annex C for examples.
(c) be securely mounted such that the system cannot be inadvertently moved or removed;
Note: Means to prevent inadvertent movement may include, but are not limited to, secured edging, secured trim,
fasteners, recessed, size and weight of large mats.
(d) be installed to minimize tripping hazards;
Note: Ramped edging is often used to securely mount a safety mat and also helps to minimize tripping hazards.
When installing a safety mat with a unidirectional surface pattern, consideration should be given to ensuring that
the safety mat is installed such that the surface pattern would reduce slipping towards the hazard.
(e) not exceed minimum object sensitivity per Clause 9.4.5.2(d) where multiple mats are installed
together to form a single sensing surface;
(f) have a maximum response time that is less than 100 ms over the system operating temperature
range;
Note: A total mat system response time of greater than 100 ms may allow a person to step lightly and quickly over
the mat’s sensing surface without being detected.
(g) have a construction suitable for the application and environment;
(h) be routinely inspected and function tested in accordance with the manufacturer’s recommendations;
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(i)
be installed and arranged such that reset of the safety function requires removal of the obstruction
from the sensing surface followed by a separate and deliberate action outside of the sensing surface,
when used as the sole means of safeguarding;
(j) be installed at a safety distance such that the edge of the safety mat sensing surface that is farthest
from the hazard is at or beyond the safety distance from the hazard, unless the safety mat is being
used solely to prevent start/restart of automatic operation or for pinch point protection where
clearance requirements in accordance with Clause 10.11 and Table 3 are not met; and
(k) the system (mat, controller, wiring between mat and controller) shall comply with Clause 9.4.1.
10.8 Single and multiple beam safety systems
Single and multiple beam safety systems shall
(a) meet the requirements of Clause 10.3;
(b) be installed so that reflective surfaces do not cause the device to fail to respond to the presence
of personnel; and
(c) not be used for finger or hand detection in a point-of-operation installation.
Note: See illustrations in Figure 4.
Beam diameter
Min
Os
Portion of
transmitter
Beam centres
Portion of
receiver
Same object;
different location
Min Os describes the size obstruction that will always be
detected, regardless of where it is in the field of the optical
presence-sensing device (1 beam is always blocked)
Notes:
(1) For PSSDs with blanking capability used, the “as used” min Os is calculated according to the following formula:
Os = (size of the largest blanked area) + (min Os without blanking)
When the entire (from transmitter to receiver) blanked area is physically filled (obstructions and guarding),
the unblanked object sensitivity is the “as used” min Os.
(2) Os determines the depth penetration factor (Dpf) of PSSDs that are installed with a vertical detection field.
Figure 4
Optical PSSD: Minimum object sensitivity
(See Clauses 10.4 and 10.8.)
10.9 Two-hand control systems
Two-hand control systems, when used as the primary means of personnel safeguarding, shall
(a) be designed to prevent accidental or unintentional operation;
(b) ensure that the individual operator’s hand controls are arranged by design, construction, or
separation so as to require the use of both hands within 500 ms to initiate/cycle the machine/system;
(c) require individual hand controls for each operator when multiple operators are safeguarded by
two-hand controls;
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(d) require each operator two-hand control station to
(i)
be concurrently operated before initiation to cycle the machine;
(ii) be maintained during the hazardous portion of the cycle; and
(iii) signal a stop if one or both hands are removed from the controls when the two-hand control
system is the only means of safeguarding;
(e) require supervisory personnel to deselect operator two-hand controls when more than one operator
control is provided;
(f) prevent cycling of the machine if all operator stations are deselected;
(g) be designed to require the release of all selected operator’s hand controls and the re-activation
of all operator’s hand controls before a machine cycle can be initiated;
(h) have all operator’s hand controls located in clear view of the hazard for which the operator hand
control is being used;
(i) have all operator’s hand controls located such that the person operating the controls is located
at a safe distance in accordance with Table 3; and
(j) provide other safeguarding means for personnel other than those using the two-hand controls.
Note: Two-hand controls only provide protection for the personnel using them.
10.10 Operator restraint devices
10.10.1 General
These devices protect only the operator from injury and therefore access to the vicinity of the machine
should be restricted only to the operator during the operation of the machine.
10.10.2 Pull-back device (or pull-out device)
This type of device is commonly used as a method of guarding in punch and brake press operations.
It works through a direct mechanical linkage, where downward motion (working stroke) of the ram will
remove the operator’s hand from the danger zone.
The linear motion of the ram is multiplied by a geared rotating cam so that the hands are pulled away
from the danger zone faster than the speed at which the ram descends. For this reason, pull-back devices
are not to be used on presses utilizing short (less than 40 mm) strokes. Operators should not feel any
motion under proper set-up. The only time the operator’s hands would feel a jerking motion is when they
are within the danger zone.
The following requirements shall apply to these devices:
(a) A pull-back device, if used, shall protect the operator such that it is able to withstand the expected
operational stresses and other relevant external influences.
(b) The pull-back device shall be connected to and operated only by the downward stroking machine
slide.
(c) The hand attachments, including wristlets, snaps, and cables, shall be used in accordance with the
manufacturer’s instructions.
(d) Each device in use shall be visually inspected and checked for proper adjustment at the start of each
operator shift, following a new set-up, when operators are changed, and after any repair or
maintenance that can affect the performance of the pull-back (see Clause 14).
(e) Necessary maintenance or repair, or both, shall be performed and completed before the machine
production system is operated.
(f) Fasteners, pins, and other components used to secure and maintain the setting of the device shall
be applied in such a manner as to prevent loosening, slipping, or failure during use.
(g) The pulling or holding members or cables and the hand and wrist attachments of the device shall
be of a substantial material that will resist deterioration from environmental conditions.
(h) Machine set-ups that have bolts, nuts, studs, stops, blow-off tubes, or other objects that protrude
from the point-of-operation shall be protected so that they shall not interfere with the normal pulling
action of the hand attachments.
(i) If work gloves are worn by the operator, the user shall ensure that the gloves are worn over the hand
attachments and worn when the adjustment is checked.
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All set-up, adjustments, and maintenance shall be performed and documented in accordance with
the manufacturer’s instructions.
10.10.3 Hold-back (hold-out or fixed restraining) device
Hold-back devices consist of wristlets similar to those used in a pull-back device, but attached to cables
that are anchored firmly and adjusted so that the operator’s fingers cannot reach the danger zone.
These devices are useful on feeding parts in a machine that is of such size that entry to the point of
operation is not required. A separate hold-back or restraining device shall be provided for each operator
if there is more than one operator.
The following requirements apply to these devices:
(a) A restraint device, if used, shall protect the operator such that it is able to withstand the expected
operational stresses and other relevant external influences.
(b) Hand and wrist attachments shall be anchored and adjusted in such a way that the operator is
restrained from reaching into the point-of-operation at all times.
(c) Each device in use shall be visually inspected and checked for proper adjustment at the start of each
operator shift, following a new set-up, when operators are changed, and after any repair or
maintenance that can affect the performance of the hold-back (see Clause 14).
(d) Fasteners, pins, and other components used to secure and maintain the setting and adjustment of the
restraint device (holdout) shall be applied in such a manner as to prevent loosening, slipping, or
failure during use.
(e) Holding members or cables and the hand and wrist attachments of the device shall be of a substantial
material that will resist deterioration from environmental conditions.
(f) All set-up, adjustments, and maintenance shall be performed and documented in accordance with
the manufacturer’s instructions.
10.11 Safeguarding device safety distance
The calculation for minimum safe distance between a safeguarding device and the danger zone of a
machine shall be as follows:
Ds = [K × (Ts + Tc + Tr + Tbm)] + Dpf
where
Ds =
minimum safe distance between the safeguarding device and the hazard
K
speed constant: 1.6 m/s (63 in/s) minimum, based on the movement being the hand/arm only
and the body being stationary
=
Note: A greater value may be required in specific applications and when body motion must also be considered.
Ts
=
worst stopping time of the machine/equipment
Tc
=
worst stopping time of the control system
Tr
=
response time of the safeguarding device, including its interface
Note: Tr for interlocked barrier may include a delay due to actuation. This delay may result in Tr being a deduct
(negative value).
Note: Ts + Tc + Tr are usually measured by a stop-time measuring device if unknown.
Tbm =
additional stopping time allowed by the brake monitor before it detects stop-time deterioration
beyond the end users’ predetermined limits. (For part revolution presses only.)
Dpf =
maximum travel towards the hazard within the presence-sensing safeguarding device’s (PSSD)
field that may occur before a stop is signaled. Depth penetration factors will change depending
on the type of device and application. See Figure 5 for specific values. (If applicable, based on the
style of safety device.)
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10.12
Table 3 and Figure 5 show the distances that guards shall be positioned from the nearest point-ofoperation hazard. The various openings are such that for average-size hands, an operator’s fingers will
not reach the point of operation. After installation of point-of-operation guards, and before a job is
released for operation, a check should be made to verify that the guard will prevent the operator’s
hands or other body parts from reaching the point of operation.
Table 3
Minimum distance from hazard as a
function of barrier opening size*
(See Clauses 6.2.2.2.2, 6.2.3.1.2, 10.2.1, 10.2.3, 10.7, 10.9, 10.12, and 13.1.3 and Figure 5.)
Barrier opening size
(smallest dimension)
mm
Minimum distance
from hazard
in
Slotted opening
Square opening
0.0– 6.0
0.000–0.250
≥ 13.0 mm†
0.5 in
≥ 13.0 mm†
0.5 in
6.1– 11.0
0.251–0.375
≥ 64.0 mm
2.5 in
≥ 48 mm
1.9 in
11.1– 16.0
0.376–0.625
≥ 89.0 mm
3.5 in
≥ 66 mm
2.6 in
16.1– 32.0
0.626–1.250
≥ 166.0 mm
6.5 in
≥ 166.0 mm
6.5 in
32.1– 49.0
1.251–1.875
≥ 445.0 mm
17.5 in
≥ 445.0 mm
17.5 in
49.1–132.0‡
1.876–5.000‡
≥ 915.0 mm
36.0 in
≥ 915.0 mm
36.0 in
* Based on data presented in Donald R. Vaillancourt and Stover H. Snook, “A Review of Machine-Guarding
Recommendations,” Applied Ergonomics, Vol. 26, No. 22, pp. 141–145, The Liberty Mutual Research Center
for Safety and Health; and Standard Drawing 2063-2, ©1998 Liberty Mutual Group. Used with permission.
† Barriers shall not be located less than 13.0 mm (0.5 in) from the hazard.
‡ Barrier openings shall not be greater than 132.0 mm (5.0 in) unless a risk assessment is performed.
Note: These criteria are for new installations only.
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132
(5.0)
Barrier opening size —
smallest dimension
mm (in)
32
(1.25)
16
(0.625)
11 (0.375)
6 (0.250)
64
(2.5)
13
(0.5)
49
(1.875)
445
(17.5)
166
89
(6.5)
(3.5)
Opening
915
(36.0)
Distance from hazard, mm (in)
Hazard
Slotted opening
132
(5.0)
Barrier opening size —
smallest dimension
mm (in)
32
(1.25)
16
(0.625)
11 (0.375)
6 (0.250)
48
(1.9)
166
66
13
(6.5)
(2.6)
(0.5)
Hazard
49
(1.875)
445
(17.5)
Opening
915
(36.0)
Distance from hazard, mm (in)
Square opening
Figure 5
Graphical illustration of Table 3
(See Clause 10.11.)
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11 Lasers
11.1
Manufacturers are required by regulations in Canada to classify the laser products and then to identify this
classification to users by means of a label on each product (see Government of Canada Nuclear Safety and
Control Act, Radiation Emitting Devices Regulations).
11.2
Laser devices are classified into four hazard categories based on the potential severity of injury to persons
exposed to the beam or its specular reflections:
(a) Class I — incapable of producing damaging levels of radiation;
(b) Class II — visible light-emitting lasers not likely to cause injury to the eye due to brief, incidental
contact with the open eye;
(c) Class III — visible light and UV radiation-emitting lasers that may cause injury to the eye. Class III
lasers are further separated into two subclasses:
(i)
Class IIIA lasers are those considered to present a slight injury potential to eyes; and
(ii) Class IIIB lasers present a risk of significant injury to eyes; and
(d) Class IV — lasers that present a significant danger to skin and internal organs.
For classification of laser products, see IEC 60825 and ANSI Z136.1.
11.3
For Class III and IV lasers, safeguards shall be selected from the following:
(a) totally enclosed housings, limiting access;
(b) laser barriers and protective curtains;
(c) limiting open beam path, which completely surrounds the laser-focusing optics and the immediate
area of the workstation;
(d) under conditions where the beam path is totally unenclosed, used in specific application, e.g., open
industrial processing systems (often incorporating robotic delivery), controls shall be selected to
prevent exposure to an accessible beam;
(e) under conditions where the entire beam path is not completely enclosed, access to laser-controlled
areas shall be limited to persons wearing proper laser protection;
(f) individuals operating, maintaining, or servicing lasers shall be qualified and authorized; training these
individuals in aspects of laser safety is required for Class IIIB and Class IV laser installations; or
(g) where engineering controls are inadequate to eliminate the possibility of potentially hazardous
exposure, additional administrative and procedural controls shall be implemented; for example,
(i)
use of laser protective eyewear and clothing; and
(ii) following standard operating procedures.
11.4
A laser warning sign shall be posted both inside and outside the laser-controlled area.
12 Ergonomics
12.1 General
Machines shall be designed with consideration for ergonomics, including the movement and
posture of the worker required to operate and maintain the machine, and the location and design of
controls and displays. Machine design should also take into consideration the physiological and the
cognitive/perceptive abilities of the user.
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12.2 Body sizes and shapes
The body sizes and shapes of the probable machine operators shall be taken into account, as well as the
efforts and postures, reach envelopes, and frequency of cyclic actions required to avoid cumulative strain
or fatigue. When reaches are required, the smaller user should be considered; when clearance is required,
the larger user should be considered.
12.3 Adjustable features
Adjustability to accommodate users of different sizes is a desired feature in machine design
(i.e., height adjustability).
12.4 Working postures
During regular or frequent work actions, awkward postures should be avoided through considering the
following principles:
(a) the worker should maintain an upright, forward-facing posture;
(b) work should not be performed consistently at or above the level of the heart. Where light handwork
above this level is required, supports for the arms shall be provided;
(c) the wrists should be maintained close to the neutral position, with the hand in-line with the axis of
the forearm;
(d) when work is performed while standing for prolonged periods in one place, the operator should
be provided with a cushioned surface to stand on or a foot rail or rest to relieve the effects of the
sustained stationary position;
(e) when work is performed while seated, the operator should be provided with a padded,
height-adjustable seating device that supports the back without restricting free movement of the
arms; and
(f) for a seated operator, the machine shall be designed with adequate leg and foot room.
12.5 Visual considerations
Where vision is a critical component in the task,
(a) the worker should be able to view the areas of primary importance without adopting awkward
postures;
(b) controls or guards shall be designed and located so as not to interfere with the operator viewing
the task during work;
(c) adequate general or task lighting shall be provided to minimize eye-strain; and
(d) glare, shadows, contrast, and reflections shall be kept to a minimum.
12.6 Physical effort
12.6.1 Exerted muscle force
Where muscular force is exerted, it should be applied by the largest appropriate muscle group available,
and should not be applied with the body joint at the extreme of its range of motion.
12.6.2 Maximum force and/or speed
The maximum force, speed, or accuracy required to operate a machine should not exceed the limits of
the least capable operator, and normal requirements for operators should be considerably less than the
maximal capabilities of most operators.
12.7 Machine pace
The operator’s work actions should not be machine paced.
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12.8 Displays
12.8.1 Indicators, dials, and displays
Indicators, dials, and visual display units shall be designed and located so that
(a) they fit within the parameters and characteristics of human perception and cognition;
(b) the information displayed can be detected, identified, and interpreted conveniently;
(c) the operator can read displays of primary importance from the control position;
(d) as far as possible, they are located close to the controls that affect them; and
(e) critical information is presented through auditory or other forms of annunciation when
predetermined limits have been exceeded.
Note: Materials temperature in an injection machine may be considered to be critical information. However, it needs
to be fitted with alarms and signals only when it deviates from a set norm.
12.8.2 Analog displays
12.8.2.1
Analog displays are preferable to digital displays unless highly accurate, quantitative information is
required.
12.8.2.2
Analog displays shall be used unless the output will change rapidly or when the direction of change is key
information.
12.9 Controls
12.9.1
Position controls shall be positioned and spaced so as to provide safe and easy operation. There shall be
adequate clearance between each control and other parts of the machinery. Controls should be so placed
that the operator can reach them easily without stretching or moving from the normal working position.
(See Table 4 for recommended ergonomic control parameters.) The controls most frequently used should
be placed in the most accessible positions. To reduce the possibility of error when an operator changes
from one unit of machinery to another of similar type, a standard layout should, where practicable, be
adopted for machinery and work situations having the same pattern of operation.
12.9.2
Start controls shall be shrouded, gated, or so positioned that they cannot be operated inadvertently.
12.9.3
A stop control shall be positioned near each start control.
12.9.4
Where more than one control station is provided, these shall be arranged to take account of any increased
risk to people who may be affected by the operation of one of the controls. This should be achieved
by providing positive control circuit selection at the master control station overriding all other controls,
so that the start control can be transferred from one position to another. Handles, hand-wheels, and levers
shall be so positioned that when the operator is operating them other controls cannot inadvertently be
operated. Two-hand controls shall be so placed, separated, and protected as to prevent them from being
operated by any means other than two hands.
12.9.5
Controls shall be designed so that they follow the ergonomic principles (see Table 4) and take into
consideration the use of personal protective equipment.
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12.9.6
When controls are hand activated and used, they shall be located so as not to require awkward working
postures (see Clause 12.4).
12.9.7
Controls that are used to initiate operations shall be of appropriate size and shape and be free of sharp
edges to prevent injury to the operator’s hand. Controls should not be right- or left-handed biased.
12.9.8
The efforts required to activate controls shall be sufficient to avoid accidental activation and kept low
enough to prevent operator fatigue.
Table 4
Recommended ergonomics control parameters
(See Clauses 12.9.1, 12.9.5, and 12.10.2.)
Dimension
Dual palm buttons
Foot control
Surface
Mushroom/dome-shaped
Slip-resistant tread
Diameter
50–60 mm (1.976–2.36 in)
50–80 mm (1.97–3.15 in)
Horizontal location
< 250 mm (10 in) in front of operator
Directly in front
Vertical location
0.90–1.15 mm (35–45 in) above standing surface
Pedal height of 12–65 mm
(0.5–2.5 in)
Control separation
300–400 mm (12–18.7 in) symmetrical in front of the body
Operable by either foot
Force
4–16 N (0.90–5.60 lbf)
15–80 N (3.37–17.87 lbf)
12.10 Foot-operated controls
12.10.1
Foot-operated controls, other than for an emergency stop, shall be adequately shrouded or otherwise
arranged to prevent, as far as possible, accidental operation from any cause. Pedals should not be of
greater width than that required for foot operation. Movable pedals should be shrouded to permit access
from one direction only. Mechanical foot-operated controls that require additional forces, and would not
create a hazard when accidentally applied, do not require shrouding.
12.10.2
Foot controls shall be operable by either leg and shall not require ankle movement greater than
25 degrees from the neutral position in either direction. The vertical height and travel distance of
the foot control shall be kept to a minimum to reduce leg movement and allow a balanced posture
(see Table 4 for recommended ergonomic control parameters).
12.10.3
A foot pedal shall be of sufficient size and texture to prevent slippage.
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13 Environmental considerations
13.1 Hygiene and guard design
13.1.1
Machinery used in certain industries, notably for the processing of food and pharmaceuticals, shall be so
designed that it is not only safe to use but can be readily cleaned. Where guarding is added at a later
stage, it shall allow adequate facilities for the cleaning of both the machine and the guard.
13.1.2
Where practicable, guards that are required to open for cleaning shall be completely detachable in order
to eliminate the need for inaccessible hinge pins that are difficult to clean. Where it is necessary to provide
a safeguard that is not detachable, e.g., a trip device, hinges shall be kept to a minimum in number and be
located as far as possible from the material being processed.
13.1.3
A fixed guard shall be so arranged as to have the minimum surface contact with the machine by mounting
it on spacers. This allows residues to be washed away through the gaps between the guard and the
machine. The gaps shall not, however, permit access of the fingers to the hazardous parts while they are in
motion. (See Table 3.)
13.1.4
Materials used for safeguards shall be non-toxic, non-absorbent, shatterproof, readily cleanable, and
unaffected by the material being processed or by any cleaning or sterilizing agent. Welds used in the
fabrication of guards shall not form surfaces that cannot easily be cleaned. All tubes used in the
construction shall have their ends sealed.
13.2 Electromagnetic interference
Designers and manufacturers shall ensure that the electrical equipment of the machine does not generate
electromagnetic disturbances above levels that are appropriate for its intended places of use. In addition,
the electrical equipment shall have an adequate level of immunity to electromagnetic disturbances so
that it can operate in its intended environment. Clause 7.22 addresses installation considerations.
See CAN/CSA-C108.6 for EMI measurement methods.
13.3 Moving parts of machinery
A traversing part or material carried by it shall not approach within 500 mm of any fixed structure,
whether or not it is part of the machine, if anyone is liable to pass through the space between the
moving and fixed parts. In particular, extra space may be required for large tools and components
and/or for any handling equipment needed.
14 Maintenance
14.1 Access to machinery for maintenance
Machinery should be designed to enable all routine adjustments, lubrication, and maintenance to be
carried out without removing the guard or disabling a safety device, and without extensive dismantling of
machinery components. Lubrication and routine maintenance facilities should be incorporated outside the
danger zone or such activities shall be subject to lockout procedures.
To facilitate cleaning and maintenance work without causing interference to adjacent machinery, any
platforms, means of access, or lifting suspension points should be “built-in.”
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14.2 Operational maintenance of safeguards
14.2.1
The maintenance of safeguards, once they are taken into use, is essential to their continued effectiveness.
14.2.2
There shall be regular inspection of safeguards to ensure that the requisite standard of safety is
maintained. Reference shall be made to the manufacturer’s specifications concerning the vital
components of a safeguard, e.g., switches, relays, and valves, when deciding their useful life.
A routine inspection of all safeguards shall be made as part of a planned maintenance program.
In addition, some safeguards shall be tested as part of the production procedure, the frequency of
testing depending on the type of safeguard and its operational characteristics.
14.2.3
Inspection and testing programs shall be carried out by trained and experienced personnel. The degree
and extent of training will depend on the complexity of the machinery and the risks arising from its use.
14.2.4
Sometimes when toolsetting or repair and maintenance of machinery is carried out, the safeguarding
arrangements effective during the normal operation of the process need to be disturbed. When the work
has been completed, a check shall be made to ensure that all the safeguarding arrangements are restored
to their proper working condition.
14.2.5
Care shall be taken in the maintenance of the normal machinery control and operational functions, some
of which have a considerable effect on safety, e.g., work-holding devices and programmable systems.
14.2.6
Safe systems of work shall be implemented where access is required to a danger zone.
14.3 Waste and spillage removal
Attention shall be paid to safety in the area surrounding the machine, e.g., protecting persons from
hazards caused by leaking oil, coolant, etc. Safe means shall be provided for the removal of swarf,
trade waste, or spilled materials.
14.4 User responsibility
14.4.1
The user shall ensure that guards and safety devices comply with the requirements of the regulatory
authority having jurisdiction.
14.4.2
Where specific applications require guards or safety devices not provided by the manufacturer, the
user shall ensure that appropriate safeguarding is installed. The user shall ensure written instruction
is provided for the inspection of these additional safeguards.
14.4.3
When toolsetting, repairing, or maintaining machinery, the safeguarding arrangements effective
during the normal operation of the process may need to be disturbed. When the work has been
completed, a check should be made to ensure that all the safeguarding arrangements are restored
to their proper working condition.
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14.4.4
Lockout and safety procedures shall be implemented where access is required to a danger zone.
14.4.5
In considering measures for all the hazards during each relevant phase of machine life, risk assessment
techniques will assist in choosing the best possible combination of safety measures (see Clause 5).
15 Safe work practices
15.1 General
15.1.1
It is not possible for designers and manufacturers to eliminate all hazards or to design completely
adequate safeguards to protect people against all risks, particularly during such phases of machine life
as commissioning, setting, process changeover, programming, adjustment, cleaning, and maintenance,
where often direct access to danger zones of the machine may be necessary. There are also a number
of types of machinery where, at present, it is recognized that complete safeguarding cannot be provided
even for operational activities. For some of these types of machinery (e.g., band saws, radial arm saws,
etc.), safe working practices are specified, e.g., in statutory regulations.
15.1.2
Users and operators shall be aware that safety of machinery depends on the designers and manufacturers
employing a combination of hazard reduction by design, safeguards, and providing information to enable
the user to develop and apply safe working practices.
15.1.3
Safe working practices should have been taken into account at the design stage, since the provision of jigs,
fixtures, fittings, controls, and isolation arrangements will frequently be involved.
15.2 Work practices
15.2.1 General
Mechanical hazards are sometimes unavoidably present without full safeguarding. In these circumstances,
special precautions shall be taken as outlined in Clause 15.2.2. However, this situation can often be
avoided, provided that a machine can be guarded in the operational phase, if during other phases work
is carried out with energy source, services, and process lines isolated (i.e., lockout and energy isolation).
Where isolation of all these is not possible because of the activity being carried out, frequently the
machine’s operation can be limited in some way (i.e., restricted operation), though the precautions
given in Clause 15.2.2 should still be applied.
15.2.2 Practices for working machinery
15.2.2.1
Situations involving unguarded machinery under power in any phase of life should have been avoided by
appropriate design measures wherever technically feasible. Alternatives may have included the use of
completely different types of machines to achieve the same end product.
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15.2.2.2
In accordance with the risk assessment, the following general precautions should be observed by properly
trained and supervised personnel (see Clauses 16 and 17):
(a) Safe access, with firm footholds (and handholds where necessary), shall be provided around and in
the vicinity of the machine. Such access should be free of obstruction and any material likely to cause
slipping.
(b) Where the hazards include entanglement and drawing-in, materials likely to be caught up, such as
loose clothing, neckties, gloves, rings and other jewellery, long hair (unless tied back and/or covered),
and fabric first aid dressings and bandages, should be avoided. For any close approach, close-fitting
overalls with close-fitting cuffs and no external pockets should be provided. It should be borne in
mind that even when guarded against contact, entanglement hazards may be within reach of
adjacent loose or stray material, etc.
(c) Material in the machine, e.g., material being processed or by-products such as swarf, may also
present an entanglement hazard. Work should be conducted in a manner that avoids contact or
entanglement with these materials.
(d) Where the hazards include impact or penetration due to flying objects, including small particles
and dust, appropriate eye protection shall be worn.
(e) Precautions against impact injuries due to kickback are necessary on certain types of cutting and
abrasive machinery, particularly where workpieces are manipulated by hand. These include the
following:
(i)
provision of backstops on vertical spindle moulding work;
(ii) ensuring that circular saw blades are adjusted to protrude through the material being cut,
and that riving knives are of the correct thickness;
(iii) ensuring that work rests are adjusted close to abrasive wheels or that tool rests are correctly
adjusted; and
(iv) ensuring that cutter speeds, or wheel speeds, are correct for the task in question; this includes
ensuring that circular saw blades are of a large enough diameter to have the correct tooth
speed. Machines should have been labelled with the minimum blade diameter.
(f) Precautions against impact injuries due to bursting generally involve ensuring that relevant rotating
equipment, and the abrasive wheels, etc., used with it have been marked clearly with their speeds.
(g) There are also practices relating to approach to mechanical hazards that are relevant to most of the
types listed in Table A.1. These include the following:
(i)
limiting closeness of approach, e.g., in work near overhead travelling cranes, or in taking off
work from the rear of a saw table, and in avoiding presence in certain areas of a machine’s
traverse;
(ii) provision and use of manual handling devices, e.g., tongs for forging work, push sticks for
circular saws and spindle moulders, or push blocks for planing machines; and
(iii) provision of jigs and holders for workpieces, e.g., for vertical spindle moulding, or for cutting
irregular material on circular saws.
15.2.2.3
In the development of work practices, users should take into consideration the logical progression in
safeguarding technology from tongs, push sticks, etc., through jigs and holders, through more
sophisticated clamping devices and manually operated travelling tables to energy-driven feeds and
automatic feeding arrangements that may be employed with a given machine.
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16 Supervisory control
16.1 General
16.1.1
Where safety from mechanical (and other) hazards is dependent on people carrying out safe working
practices, managerial and/or supervisory control shall be exercised. Where risk is minimal, verbal
instructions may be adequate. However, as risk increases, defined procedures in writing should be used so
that they can be supervised more rigorously.
16.1.2
Where the risk level is high (e.g., there is a possibility of serious injury or death if the procedure is not
followed correctly), a permit-to-work system should be used. This will normally involve specification of
the controls, etc., for isolation and for internal hazard dissipation, as well as supervisory checks to ensure
that they have been operated and secured and that the plant is free of hazard (or that additional
protective measures, such as the availability and use of protective equipment, are followed).
16.1.3
An equivalent check on the procedures should be performed prior to putting the equipment back into
operation. On occasion, checks may need to be made during the authorized work.
16.1.4
The task to be carried out, and the individual responsibilities of those involved, should be specified in
detail. Trained and qualified supervision should be provided to ensure that the user systems operate
correctly.
16.2 Permit-to-work systems
16.2.1
The most common use of a permit-to-work system is during maintenance operations. In circumstances
where a procedure, in the form of a safe system of work, is used, users shall identify the hazards that are
present and develop a safe system of work to either eliminate them or, where this is not practicable, ensure
that individuals are made aware so that personal precautions against possible injury can be taken.
16.2.2
Effective control should be achieved by means of a written system, though even this relies on the human
element, for no documentation system can by itself prevent accidents. The system, which is known as a
permit-to-work system, requires formal action on the part of those doing the work, those responsible for it,
and those authorized by the user to sign such permits. The person responsible for supervising the work
should ensure that the person(s) undertaking the work are identified and properly trained and understand
the task involved and the precautions to be taken.
16.2.3
The user shall develop a safe procedure that contains a clear record of all the foreseeable hazards that have
been considered in advance, together with the appropriate precautions taken in their correct sequence
and the starting and finishing times for the task. The formal handbook procedures should be documented
as appropriate.
16.2.4
Work in potentially hazardous circumstances can be done in safety through the use of the work permit
method. The specific design of a permit-to-work system will depend on the nature and degree of risk, the
complexity of the task, and the industry to which it relates.
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17 Information and communication
17.1 General
There are various ways in which information will have been provided by designers and manufacturers for
users of machinery or for persons who may be in the vicinity of machinery. These include training manuals,
instruction manuals, instruction placards, and warning labels. All information shall
(a) have been presented clearly in English (and other languages where necessary);
(b) be in a logical sequence with good illustrations; and
(c) use standard symbols.
17.2 Instruction placards and warning labels
Designers and manufacturers shall have provided warning labels on the machinery that may be
appropriate for
(a) commissioning and installation, e.g., to indicate lifting procedures or the exposure of hazardous
parts prior to the fixing of safeguards during the commissioning phase; or
(b) operation of the machine, e.g., to indicate hazardous parts of machinery behind a guard, such
as drive systems or electrical control equipment, or to inform about safe working procedures,
e.g., the need to wear eye or ear protection.
Warning labels should be clear and concise and use, where practicable, standard symbols and colours
as specified in CAN/CSA-Z321.
Instruction placards may be used in the area adjacent to the machinery to explain the legal
requirements, e.g., statutory notice, outlining the dangers associated with abrasive wheels, or to carry
reference information on machinery operation.
17.3 Installation, operation, and maintenance instructions
17.3.1
The manufacturer shall provide sufficient information with each machine, including drawings, to enable
the correct installation, safe operation, and maintenance for
(a) transport;
(b) unloading and lifting, including the weight of the machine and its attachments, with indication
where it should be lifted;
(c) commissioning and installation, i.e., the limits of travel of all moving elements should be shown
(see Clause 13.3 for spacing);
(d) start-up, including preparation before start-up;
(e) operation, including description of controls and function;
(f) close-down;
(g) setting/process changeover/programming (particularly robots);
(h) adjustment;
(i) cleaning;
(j) lubrication, refuelling, and recharging; and
(k) repair, including information on foreseeable failures, and fault finding.
17.3.2
Designers and manufacturers shall identify the potential hazards for all the phases of machine life and
the safeguards to protect against the hazards. The safe working and operational procedures required
(including emergency procedures) and the emergency equipment that may be needed should have
been described.
17.3.3
For machinery supplied without tooling, the manufacturer shall indicate that the user may need to provide
additional safeguards to the existing guarding in certain circumstances.
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17.3.4
For machinery supplied with tooling for a specific workpiece or a range of workpieces, the user shall review
the original safeguards if tooling and/or workpiece considerations are changed.
18 Training
18.1 General
Where training documentation is not provided by the manufacturer, the user shall ensure that
appropriate training documentation is developed. The user shall ensure that formal training based
on this documentation is provided to affected personnel (e.g., operators, set-up persons, maintenance
personnel, supervisors, etc.). This is particularly applicable to young or inexperienced workers. It is also
particularly important to cover those phases of machine life where risk is higher, e.g., due to the removal
of safeguards. Safety training shall, where possible, form part of an integral program covering all aspects
of the work to be undertaken.
Users shall make themselves aware of any training courses offered on the operation and maintenance
of the machinery by the manufacturer.
18.2 Training procedures
18.2.1 Machinery operators
Machinery operators shall be trained in the following:
(a) machinery safety procedures, including emergency procedures;
(b) the correct and safe way of doing the job;
(c) knowledge and understanding of the hazards they face;
(d) understanding the purpose and function of the safeguards that protect them, in particular,
where adjustable guards are used, which may not afford completely effective safeguarding,
e.g., on some woodworking and milling machines, it is essential that the operator be instructed
in safe working practices;
(e) reporting faults immediately, including guard defects;
(f) wearing and care of protective clothing and equipment; and
(g) the need for good housekeeping.
18.2.2 Plant engineers and maintenance staff
Plant engineers and maintenance staff shall be trained in the following:
(a) principles of safeguarding machinery;
(b) electrical and mechanical safety;
(c) precautions during maintenance work, including safe systems of work and, where necessary,
permit-to-work and lock-out systems, e.g., padlock, captive key or interlock key exchange,
and emergency procedures; and
(d) wearing and care of protective clothing and equipment.
18.3 Personal protection
In considering methods of safeguarding machinery, designers and manufacturers may also have believed it
necessary to consider the provision of personal protective equipment to minimize the risk of injury and
should have provided information. This may include the need for special clothing, including protective
head and footwear, hearing defenders, eye protection, or breathing apparatus. All those required to wear
personal protective equipment shall be given training in its proper use, care, and maintenance.
Users should be aware of the requirements of the following CSA Standards when providing personal
protective equipment: CAN/CSA-Z94.1, CSA Z94.2, CAN/CSA-Z94.3, CSA Z94.4, CAN/CSA-Z195, and the
CSA Z259 Standards.
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Annex A (informative)
Hazards, controls, and interlocks
Note: This Annex is not a mandatory part of this Standard but is written in mandatory language to accomodate its
adoption by anyone wishing to do so.
Table A.1
Examples of hazards and hazardous situations
(See Clauses 5.4.3 and 15.2.2.2.)
Hazards and hazardous situations
Clause
references
Mechanical hazards due to machine parts or workpieces, e.g.,
6.1.3
(a) shape;
6.1.3.3
(b) relative location;
(c) mass and stability (potential energy of elements that may move under the effect of gravity);
(d) mass and velocity (kinetic energy of elements in controlled or uncontrolled motion);
(e) inadequacy of mechanical strength; and
(f) accumulation of energy inside the machine, e.g.;
(i) elastic elements (springs);
(ii) liquids and gases under pressure; and
(iii) the effect of vacuum.
Entanglement hazard
6.1.3.2
Friction or abrasion hazard
Cutting or severing hazard
Shearing hazard
Stabbing or puncture hazard
Impact hazard
Crushing hazard
Drawing-in or trapping hazard
High-pressure fluid injection or ejection hazard
Electrical hazards due to
6.1.4.1
Contact of persons with live parts (direct contact)
Contact of persons with parts that have become live under faulty conditions (indirect contact)
Approach to live parts under high voltage
Electrostatic phenomena
Thermal radiation or other phenomena, such as the projection of molten particles and chemical
effects from short circuits, overloads, etc.
Thermal hazards, resulting in
6.1.4.2
Burns, scalds, and other injuries by a possible contact of persons with objects or materials with an
extreme high or low temperature, by flames or explosions, and also by heat source radiation
Damage to health by hot or cold working environment
(Continued)
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Table A.1 (Continued)
Hazards and hazardous situations
Clause
references
Hazards generated by noise, resulting in:
6.1.4.3
Hearing loss (deafness), other physiological disorders (e.g., loss of balance, loss of awareness)
Hazards generated by vibration
6.1.4.4
Use of hand-held machines resulting in a variety of neurological and vascular disorders
Whole body vibration, particularly when combined with poor postures
Hazards generated by radiation
6.1.4.5
Low frequency, radio frequency radiation, microwaves
Infrared, visible, and ultraviolet light
X- and gamma rays
Alpha, beta rays, electron or ion beams, neutrons
Lasers
6.1.4.6, 11
Hazards generated by materials and substances (and their constituent elements) processed
or used by the machine
6.1.4.7
Hazards from contact with or inhalation of harmful fluids, gases, mists, fumes, and dusts
Fire or explosion hazard
Biological or microbiological (viral or bacterial) hazards
Hazards generated by neglecting ergonomic principles in machine design as, e.g.,
hazards from
6.1.4.8, 12
Unhealthy postures or excessive effort
Inadequate consideration of hand–arm or foot–leg anthropometry
Neglected use of personal protective equipment
Inadequate local lighting
Mental overload and underload, stress
Human error, human behaviour
Inadequate design, location, or identification of manual controls
Inadequate design or location of visual display units
Inadequate design, visibility of working and/or hazard zone
Combination of hazards
6.1.4.9
Unexpected start-up, unexpected overrun/overspeed (or any similar malfunction) from
Failure/disorder of the control system
6.2.1.8.1.3
Restoration of energy supply after an interruption
6.2.1.8.2
External influences on electrical equipment (e.g., EMF)
6.2.1.9.4
Other external influences (gravity, wind, etc.)
6.2.1.9.1
Errors in the software
6.2.1.1.5
Errors made by the operator (due to mismatch of the machine with human characteristics and
abilities, see Clause 12)
—
6.2.1.9.9
—
(Continued)
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Table A.1 (Concluded)
Hazards and hazardous situations
Clause
references
Impossibility of stopping the machine in the best possible conditions
6.1.3.3
Variations in the rotational speed of tools
—
Failure of the energy source
7.8.1
Failure of the control circuit
6.2.1.9.10.5
Errors of fitting
—
Break-up during operation
—
Falling or ejected objects or fluids
6.2.3.2.1
Loss of stability/overturning of the machine
6.1.3.3
Slip, trip, and fall of persons (related to the machine)
6.1.3.4
Pace of work
12.7
Excessive overtime and fatigue
—
Operator trapping hazard
—
Note: This list has been taken from Annex A of ISO 14121 and is used with permission.
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Table A.2
Example descriptions of risk factor categories
(See Table 2.)
Factor
Category
Severity
S2
Serious injury
Fatality, irreversible injury, loss of consciousness,
loss of sight, limb amputation, severe laceration,
or broken bone.
S1
Slight injury
Normally reversible, or requires only first-aid
treatment.
E2
Frequent exposure
Typically, exposure to the hazard more than once
per hour.
E1
Infrequent exposure
Typically, exposure to the hazard less than once
per day or shift.
A2
Not likely
Cannot move out of way; or inadequate reaction
time; or machine speed greater than 250 mm/s.
A1
Likely
Can move out of way; or sufficient warning/reaction
time; or machine speed less than 250 mm/s.
Exposure
Avoidance
March 2004
Criteria
87
(See Clause 5.6.3.)
Main considerations
Methods
Electrical
(a) Interlocking devices used for interfacing with guard
movement
(b) Signal operated devices, e.g., relays or contactors
(c) Interconnections within the system, e.g., wiring
(d) Overall system design
Interlocking methods in general are described in Table A.6.
Methods of electrical interlocking include
(a) single-control system interlocking;
(b) dual-control system interlocking with or without cross-monitoring; and
(c) power interlocking.
Mechanical
(a) Interlocking devices used for interfacing with guard
movement
(b) Clutches and brakes
(c) Interconnections, e.g., shafts, links, etc.
(d) Overall system design
Unlike electrical, hydraulic, or pneumatic systems, it is unusual for
mechanical systems to be anything other than single-control systems.
However, consideration should be given to other systems design possibilities,
e.g., additional clutches, brakes, or linkages. An approximation to energy
interlocking methods may be achieved when the link between the guard
and the energy interruption device is direct.
The basic elements of single-channel control system interlocking are
(a) the actuating device operated by the guard;
(b) interposed mechanical linkages, if any; and
(c) the clutch or brake controlling the drive. Reducing the number
of interposed linkages reduces the probability of the system failing
to danger.
Hydraulic
(a) Interlocking valves used for interfacing with guard
movement
(b) Signal operated devices, e.g., pilot or solenoid
operated valves
(c) Interconnections within the system, e.g., piping, hose,
tubing, etc.
(d) Overall system design, in particular, problems of
intensification and stored energy
Interlocking methods in general are described in Table A.6.
Methods of hydraulic interlocking include
(a) single-channel control system interlocking;
(b) dual-channel control system interlocking with or without
cross-monitoring; and
(c) power interlocking.
Pneumatic
(a) Interlocking valves used for interfacing with guard
movement
(b) Signal operated valves, e.g., pilot or solenoid
operated valves
(c) Interconnections within the system, e.g., piping,
hose, tubing, etc.
(d) Overall system design, in particular, problems of
stored energy from residual pressure in components
and piping
Interlocking methods in general are described in Table A.6.
Methods of pneumatic interlocking include
(a) single-control system interlocking;
(b) dual-control system interlocking with or without cross-monitoring; and
(c) power interlocking.
* Based on BSI PD 5304.
© Canadian Standards Association
March 2004
Interlocking
Z432-04
88
Table A.3
Interlocking considerations and methods*
© Canadian Standards Association
Safeguarding of machinery
Table A.4
Interlocking switches/devices*
(See Clause 5.6.3.)
Electrical
Devices used for interfacing guard movement include
(a) cam-operated position switches;
(b) tongue-operated switches;
(c) captive key switches;
(d) trapped key interlocking of electrical switches;
(e) inductive proximity switches;
(f) magnetic switches;
(g) plug and socket systems;
(h) manually operated delay bolts; and
(i) solenoid operated shotbolts.
(See also Table A.6.)
Devices should be selected only from those where the performance, as stated by the
manufacturer, is suitable for the specific safety application.
Mechanical
Devices used for interfacing guard movement include clutches and brakes.
Hydraulic
Devices used for interfacing guard movement include
(a) cam-operated valves; and
(b) hydraulically operated shotbolts.
When valves are selected for machinery-safeguarding applications, their operating parameters
(temperature, pressure, fluid properties) and reliability should be suitable for the environment,
duty, and potential use.
Pneumatic
Devices used for interfacing guard movement include
(a) cam-operated valves;
(b) captive-key valves;
(c) trapped-key control of pneumatic valves;
(d) jet detection valves; and
(e) pneumatically operated shotbolts.
(See also Table A.6.)
When valves are selected for machinery-safeguarding applications, the valve operating
parameters (pressure, temperature, etc.) and reliability should be suitable for the environment
and its potential use.
* Based on BSI PD 5304.
March 2004
89
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© Canadian Standards Association
Table A.5
Interlocking levels*
(See Clause 5.6.3.)
Interlocking
Single channel
Dual channel
Electrical
The basic elements of single-channel
control system interlocking are
(a) the interlocking switch operated by
the guard;
(b) interposed electromechanical relays
and/or solid-state switching devices,
if any. Reducing the number of these
components lessens the probability
of failure to danger; and
(c) the electromechanical contactor
(or solid-state equivalent),
e.g., semiconductor motor controller
or starter and/or a pneumatic or
hydraulic solenoid valve controlling
energy to the drive.
The basic elements are similar to those
employed in single-channel control system
interlocking. To minimize the possibility
of common cause failures, two channels are
used and kept separate except for necessary
interconnections for cross-monitoring, where
provided, and connection to the supply.
Such systems can be hybrid, e.g., one channel
electrical and one channel hydraulic or entirely
electrical. In both channels, the output of the
energy-controlling devices shall have been
connected so that either can stop hazardous
movement of the machinery irrespective of
the condition of the other. The integrity of
dual-channel control system interlocking can
be improved by monitoring (see Clause 8.2.5).
Mechanical
—
—
Hydraulic
(a) the interlocking valve or position switch
operated by the guard;
(b) interposed control valves,
electromechanical relays, and/or
solid-state switching devices, if any;
(c) a hydraulic, air, or solenoid-operated
valve, or a solenoid-controlled
hydraulically operated valve
controlling energy to the drive.
Any of these elements, or the piping or
wiring interconnecting them, can fail to
danger; therefore, they shall provide the
maximum degree of reliability. The greater
the number of devices incorporated in the
system, the lower its inherent reliability;
therefore, interposing devices should be
avoided, where possible.
The basic elements are similar to those
employed in single-control system
interlocking. To minimize the possibility
of common cause failures, two channels are
used and kept separate except for necessary
interconnections for cross-monitoring, where
provided, and connections from the pump.
Such systems can be hybrid, e.g., one
channel hydraulic, one electro-hydraulic, or
both electro-hydraulic, or entirely hydraulic. In
both channels, the output of the
energy-controlling devices should be
connected so that either can stop hazardous
movement of the machinery, irrespective of
the condition of the other. Where the circuit is
such that a single failure is not self-revealing,
e.g., by failure of the actuator to operate, the
integrity of dual-channel control system
interlocking can be improved by
cross-monitoring.
* Based on BSI PD 5304.
(Continued)
90
March 2004
© Canadian Standards Association
Safeguarding of machinery
Table A.5 (Concluded)
Interlocking
Single channel
Dual channel
Pneumatic
(a) the interlocking valve or position
switch operated by the guard;
(b) interposed control valves,
electromechanical relays, and/or
solid-state switching devices, if any;
(c) an air-operated, solenoid-operated,
or solenoid actuated air-operated valve
controlling energy to the drive.
Any of these elements, or the piping or
wiring interconnecting them, can fail to
danger; therefore, they shall be selected to
provide the maximum degree of reliability.
The greater the number of devices
incorporated in the system, the lower its
inherent reliability; therefore, interposing
devices shall be avoided, if possible.
To minimize the possibility of common cause
failures, two channels are used and kept
separate except for necessary interconnections
for cross-monitoring (where provided), and
connection to the supply.
Such systems can be entirely pneumatic or
hybrid, e.g., one channel pneumatic and one
channel electrical. In both channels the output
of the energy-controlling devices shall be
connected so that either can stop hazardous
movement of the machinery, irrespective of
the condition of the other. Where the circuit is
such that a single failure is not self-revealing,
e.g., by failure of the actuator to operate, the
integrity of dual-channel control system
interlocking can be improved
(see Clause 8.2.5) by cross-monitoring.
Table A.6
Principles of interlocking
(See Clause 5.6.3 and Tables A.3 and A.4.)
Pneumatic overall system design
Hydraulic overall system design
Because the energy source is compressible and
normally exhausted to atmosphere, the safety circuit
design is not as straightforward as for other power
media. However, the basic aims for interlocking
remain the same and, where possible, the energy
source shall be interrupted by the guard operated
interlocking device and any residual system pressure
exhausted to atmosphere. In this condition any
cylinders will be pre-exhausted and alternative
arrangements in the system design will be necessary
where any cylinders are required to be under constant
load. In addition, particular precautions may be
necessary when reinstating the supply to
pre-exhausted cylinders if rapid acceleration is
undesirable. This latter condition can be safeguarded
against by introducing a “safe start” arrangement in
the supply line to the machine that initially restricts
the flow rate until a certain predetermined pressure
has been attained.
Two conditions that require particular attention are
intensification and stored energy. Protection against
intensification in any part of the system shall be
provided.
Problems with stored energy can be listed as
(a) energy transmitted from a supporting mass;
(b) energy stored in an accumulator;
(c) energy contained in a hydraulic cylinder under
pressure; and
(d) energy stored in large volume pipework.
Any interlocking system shall be designed to protect
against the risk of injury from such stored energy
sources. For example, where, on a down stroking
hydraulic press, safety blocks/pins are used to
support the platen at the top of its stroke and the safety
blocks/pins operate in conjunction with an interlocking
guard, the safety blocks/pins shall remain in position
until the guard is closed. The guard shall then remain
locked closed until the platen has returned to the top
of its stroke and the safety blocks/pins are in place.
(Continued)
March 2004
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© Canadian Standards Association
Table A.6 (Continued)
Pneumatic overall system design
Hydraulic overall system design
Cylinders under constant load could include clamps,
elevators, or supports. To avoid the need to maintain
supply pressure, alternative features should
be considered such as single-acting cylinders or spring
applied mechanical blocking. Where, for safety
reasons, it is required to arrest and hold the piston
in the position occupied when the guard is opened,
two poppet valves can be used. However, a hazard
could arise if connections to the cylinder are broken
so overriding the locked position. Air exhausting
through the broken connection could allow air under
pressure on the opposite side of the piston to expand
thereby causing movement that could lead to
injury. Where it is found necessary to override the
locked condition while the guard is open, a stop valve
can be added to the circuit. This would normally be
closed, but by opening the stop valve during the
locked condition the two ends of the cylinder are
connected, balancing out the pressures and enabling
the piston to be moved manually.
Where it is necessary just to arrest the movement of a
piston when a guard is open, this can be achieved by
using either two three-port two-position valves or an
equalizing valve. Both these techniques allow manual
repositioning of the cylinder with the guard open
without disconnecting pipes but are unsuitable for
clamping or supporting applications.
Further information on protection against unintended
gravity fall is given in Clause 7.3 but, particularly on
down stroking hydraulic presses, controlled gravity
descent is frequently a deliberate design feature to
facilitate rapid closing of the platen to the workpiece. In
these circumstances, all the oil in the cylinders
supporting the platen should be passed through the
main control valve or, if this is not possible, through an
auxiliary valve, the operation of which is totally
dependent upon the supply of pilot oil from the main
control valve.
On upstroking presses, the platen has to be raised
against the action of gravity and various methods can
be used to obtain rapid closing of the platen to the
workpiece. On large presses, all methods require large
volumes of oil to be supplied to the press cylinders. If
these are fed directly into the cylinders, e.g., by
non-return valves, there is a danger that, due to back
pressures in the system, the platen may make an
unintended stroke. It is therefore essential that,
whichever method is used for rapid approach, all the oil
capable of causing the platen to make an unintended
stroke shall be passed through the main control valve or
through an auxiliary valve, the operation of which
is totally dependent upon the supply of pilot oil
from the main control valve.
It may be necessary to ensure that cylinders adopt a
predetermined safe position in the event of the
energy source failing. Again, the use of single-acting
cylinders may be possible, but an alternative is to
employ a reservoir and non-return valve arrangement.
It is important to ensure that where reservoirs are
used, they are of sufficient capacity to ensure
that the cylinder does not stall in an unsafe position.
When considering interlocking systems for presses with
arrangements for fast approach, care shall be taken to
ensure that the valves interrupting the fluid flow are
effective in bringing the platen to a halt whether the
platen is closing under energy or gravity. Special
interlocking considerations may apply when a control
guard is used to safeguard a hydraulic press.
Where a machine is controlled by means of a
manually operated lever, the lever can be used to lock
the guard closed while the dangerous parts are in
motion.
The machine designer will have considered carefully
the overall system design to ensure that the
interlocking arrangements are effective against the
problems highlighted above. Users shall be equally
aware of these problems when carrying out
modifications or designing their own machines.
Although in many cases interlocking the pilot signals
rather than the energy source may be the only
practical solution, this shall be as a last resort unless
monitoring of the main energy control devices is
incorporated.
(Continued)
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March 2004
© Canadian Standards Association
Safeguarding of machinery
Table A.6 (Continued)
Pneumatic overall system design
Hydraulic overall system design
In order that a system incorporating pneumatic valve
components achieves the basic concepts, the
following points should also be observed:
(a) When the circuit incorporates devices which
could be adversely affected by excessive pressure,
e.g., diaphragm valves, suitable protection should
be provided by fitting pressure relief valves.
(b) Where practicable, signal lines should be kept
to a minimum length to facilitate rapid decay
of pressure. Where this is not practicable and
pilot signals exhausting to atmosphere retain
sufficient pressure levels to operate main
control valves, even after a guard has been
opened, additional interlocking devices shall be
provided that prevent opening of the guard until it
is safe to do so.
(c) When three-position valves are used in safety
circuits, the centre position shall provide a
supply-sealed-only condition (outlets vented)
because an all-ports-sealed centre position can
result in stored energy in the actuator, resulting
in unintended movement when piping is
disconnected.
(Continued)
March 2004
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© Canadian Standards Association
Table A.6 (Continued)
Interlocking
Power interlocking
Electrical
Energy interlocking is achieved by direct actuation of a switch in series with the energy
source to the prime mover. The actuation may be by means of a cam or linkage (guard
operated), captive-key, trapped-key, or similar mechanical arrangement to prevent the
release of the guard until the energy is isolated (guard locking).
Energy interlocking is superior to single-channel control system interlocking provided
that the switch and the mechanical interface arrangement between the guard and the
switch are of high integrity.
Mechanical
Not Applicable
Hydraulic
Power interlocking (hydraulic)
In hydraulic systems used on machinery that is designed with its own integral electric
motor driven pump, power interlocking can be achieved in two different ways. Either
(a) the pump can be left running and the guard interlocking device directly interrupts
the flow of hydraulic fluid to the actuator and releases system pressure back to the
tank; or
(b) the guard interlocking device can be an electrical position switch that directly
interrupts the electrical supply to the electric motor driving the pump.
Of the two systems, option (a) is preferred, but on large machines the effort required
to operate the interlocking device may be too high. Where option (b) is the practical
answer, any accumulators forming part of the machine system shall be automatically
dumped by the interlock. Where both systems are impracticable but selection following
the guidance given in Clause D.2 indicates that the interlock integrity shall be at least
to the level of performance of power interlocking, dual-channel control system
interlocking with cross-monitoring shall be used instead.
Pneumatic
Power interlocking (pneumatic)
Power interlocking is achieved by direct mechanical action of a valve in the main air
supply in series with the actuator. The mechanical action may be direct from guard
movement via a linkage or by a captive key or trapped key.
Interlocking by means of air isolation and exhaust may give rise to difficulties on
machinery that relies on the air supply to keep heavy articles suspended or components
clamped in position. Similarly, where machinery is designed to perform automatically a
series of functions in sequence, air isolation and exhaust interlocking could lead to the
need for extensive manual resetting of actuators and sequencing valves before the
automatic cycle can be restored. For these reasons, power interlocking methods are not
normally practicable for complex air-operated machinery and therefore control system
interlocking of the pilot signals has to be used.
However, where power interlocking is practicable, it is preferred to single-channel
control system interlocking, provided that the valve and the arrangement between the
guard and the valve are of high integrity. The arrangement shall ensure, as far as
practicable, that the guard cannot be opened until the valve connections interrupt the
air supply. Where machinery parts could fall under gravity, some form of mechanical
restraint shall be incorporated (see Clause 7.3).
(Continued)
94
March 2004
© Canadian Standards Association
Safeguarding of machinery
Table A.6 (Concluded)
Electrical Cam Operated Switches
Hydraulic/Pneumatic Cam Operated Switches
A cam-operated position switch can be actuated in
either of two modes, positive (direct) or non-positive.
(see Figure B.10)
A cam-operated valve can be actuated in either the
positive or non-positive mode. When actuated
positively, the valve is held in the shut-off position by a
cam attached to the guard, when the guard is in any
position other than fully closed. The final closing
movement of the guard releases the valve allowing the
supply to connect to the output by the action of the
return spring. When the guard is opened (hydraulic),
the supply is cut off and the output returned to tank by
action of the cam. When the guard is opened
(pneumatic), the supply is cut off and the output
exhausted by the action of the cam. When actuated
non-positively, the final closing movement of the guard
positively operates the valve, connecting the supply to
the output and allowing the machine to be set in
motion. When the guard is opened, the valve is reversed
by the action of a spring when the operating
mechanism is released, the valve cutting off the supply.
When actuated positively (directly), the switch stem is
held depressed when the guard is in any position
other than closed. This is normally achieved by a cam
or track attached to the guard. The final closing
movement of the guard releases the switch stem,
allowing the contacts to close by the action of the
return spring, i.e., the contacts are normally closed,
and when the guard is opened, the contacts are
positively (directly) opened by the cam.
When actuated non-positively, the final closing
movement of the guard depresses the stem of the
position switch, closing its contacts and allowing
the machine to be set in motion. When the guard is
opened, the switch contacts are opened by action of
the switch return spring. (see Figure B.11)
In single-control system interlocking methods, the
switch shall always have been installed in the positive
(or direct) mode, except where two switches are used
to improve the mechanical integrity to ensure that
the switch contacts are opened by the operation of
the cam, and to prevent the switch from being
deliberately defeated. In addition, switches actuated
in the positive (or direct) mode should be position
switches incorporating positive (or direct) opening
operation. Care shall have been taken when installing
such switches to ensure that the contacts are fully
open when operated. Additionally, an adequate
degree of over-travel shall have been utilized to allow
for the foreseeable loss of movement due to cam or
track wear and to prevent damage to the switch or its
mounting. Certain types of proprietary unit that
combine the switch and cam in a single enclosure
are available. This can reduce the problem of
misalignment. Internal and external mounting
arrangements should, as far as practicable, be proof
against vibration, mechanical shock, or
maladjustment. Certain types of proprietary unit are
available which incorporate early break, snap-action
contacts. These units offset the disadvantages caused
by a slow break of the electrical circuit on opening a
guard. However, great care should have been taken
by designers and manufacturers to ensure when
installing such units that the positive (or direct)
opening operation contacts are fully opened when
the unit is operated.
March 2004
In single-channel control system interlocking methods,
the valve shall always be installed in the positive mode,
except where two valves are used to improve the
mechanical integrity to ensure that the valve flow paths
are opened by the operation of the cam and to prevent
the valve from being deliberately defeated. In addition,
valves actuated in the positive mode shall have sufficient
pre-travel and overtravel to avoid being damaged by
the action of the cam. Care shall be taken when
installing such valves to ensure that the flow paths are
fully open when operated. Additionally, an adequate
degree of overtravel should be utilized to allow for the
foreseeable loss of movement due to cam or track wear.
Internal and external mounting arrangements should,
as far as practicable, be proof against vibration or
maladjustment.
Hydraulic When a guard or cover can be completely
removed from the machinery, i.e., it is not restrained
by hinges or a track, positive mode actuation by means
of a guard operated cam is not possible. Therefore, the
interlocking system should include other devices,
which may not be hydraulic, e.g., captive-key control
or trapped-key control.
Pneumatic When the guard or cover can be
completely removed from the machinery, i.e., it is
not restrained by hinges or a track, positive mode
actuation by means of a guard operated cam is not
possible. Either captive key valves or trapped key
should be used.
95
(See Clause 6.1.3.2.)
Description
Control
(a) Entanglement
Bodily contact with the following features may lead to
entanglement.
(a) Contact with a single rotating surface, e.g., couplings,
spindles, chucks, leadscrews, mandrels, bars, or
rotating workpieces. These, even when rotating
slowly, are a source of danger.
(b) Catching on projections or in gaps, e.g., fan blades,
spoked pulleys, chain wheels, gear wheels and
flywheels, mixer and beater arms, spiked cylinders,
belt fasteners, projecting keys, set screws, cotter pins
on shafts or slat conveyors.
(c) By catching between two parts (see Clause 6.1.3.2).
(i) Between counter-rotating parts, e.g., gear
wheels, rolling mills, mixing rolls and calenders,
or material being drawn between two rolls.
(ii) Between rotating and tangentially moving
parts, e.g., a power transmission belt and its
pulley, a chain and chain wheel, a rack and
pinion, metal, paper, rope, etc. and a reeling
drum or shaft, batch-up, reel-up, etc., or a
conveyor belt and its driving pulley or any
bend pulley.
Some mechanisms contain a combination of
sliding and turning movement such as those
used in certain cam gear designs, e.g., the
mechanism on the side of some flatbed printing
machines, or baling machines.
(iii) Between rotating and fixed parts, e.g., spoked
hand-wheels or flywheels and the machinery
bed, screw or worm conveyors and their easing,
revolving mixer and mincing mechanisms in
casings having unprotected openings, Z-blade
and ribbon-blade mixers, extruder scroll and
barrel, or the periphery of an abrasive wheel
and an incorrectly adjusted work rest.
Entanglement hazards may be
reduced by reducing speed or
distance of movement, by avoiding
projections and recesses, by restricting
force, torque and inertia, and by
aiming for smooth polished surfaces.
These measures apply both to
machinery and process material.
It helps also if the process material
and any by-product is discrete rather
than continuous. Every projection
such as a setscrew, bolt or key on
any exposed revolving part of
machinery should be sunk, shrouded,
or otherwise effectively guarded.
Guards for rotating shafts should
preferably be fixed guards of solid
construction. However, guards of
the loose tube type or of bellows
construction may also be used
satisfactorily in some applications
(see also Clause 6.2.2).
The ergonomic criteria given in
Clause 12.4 and Annex C should not
be regarded as giving complete
protection against entanglement.
Note: For additional illustration of
controls, see Annex B.
96
(Continued)
Safeguarding of machinery
Name
© Canadian Standards Association
March 2004
Table A.7
Mechanical hazards and controls
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Table A.7 (Continued)
Name
Description
(a) Entanglement (Continued)
(d) Catching in materials in motion, e.g., in centrifuges,
tumble driers, dough mixers, or swarf from machining
operations. The risk of entanglement is increased by
loose clothing, gloves, neck-ties, jewellery, hair,
cleaning brushes or rags, medical dressings, or
materials being handled.
(b) Friction and abrasion
The distinction between abrasion and cutting by a saw,
for example, is one of degree. Friction burns can be
caused by relatively smooth parts operating at high
speed, e.g., the rim of a centrifuge basket at the edge
of the easing opening. Other examples of friction or
abrasion hazards include the periphery of an abrasive
wheel, belt sanding machines, material running on to
a reel or shaft, a conveyor belt, and its drums or pulleys
(see Clause 6.1.3.2), and fast moving ropes or belts.
Control
Friction and abrasion hazards are
reduced by reducing speed or
distance of movement, force, torque,
and inertia, and by use of surfaces
that are as smooth as possible.
Damage due to any particular moving
surface can be aggravated by abutting
surfaces preventing removal of the
hand, etc. from the danger zone,
e.g., a badly adjusted work rest on
an abrasive wheel.
© Canadian Standards Association
March 2004
(Continued)
Description
Control
(c) Shear
Parts of the body may be sheared in the
following ways:
(a) between two machine parts, e.g., the
table of a metal planing machine and its
bed, the blade of a guillotine, nip points
between connecting rods or links and
rotating wheels, or oscillating
pendulum movements;
(b) rapidly moving parts of machinery or
pieces of material, e.g., sewing
machines, drilling machines.
The principal measures, which may be adopted
to eliminate shear traps, are as follows:
(a) filling the gaps, such that the shear trap is
minimized;
(b) reducing the maximum clearance between
the relatively moving parts so that parts of
the body cannot enter the gap, e.g., by
reducing the stroke of the machine; and
(c) increasing the minimum clearance between
the shearing parts, such that parts of the
body can enter the gap safely.
When the technique of separating the
shearing parts is used, consideration should
be given to the body parts, which it is possible
to insert in the trap. Since it relies on pushing
body parts out of the way, it is not appropriate
except on low-speed machinery, and detailed
consideration of other hazards will often rule
it out. It should be noted that the technique
is not effective against double shear traps.
Guidance on safety distances is given
in Annex C.
When it is not possible to avoid the creation
of a shear trap, it may still be possible to
restrict reach past the trap, so that injury is
reduced. It may also be possible to adjust
speed and force of movement of parts
creating the shear action.
Note: These techniques are not generally
applicable to tools whose prime purpose is to
shear, e.g., guillotines or press tools.
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(Continued)
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Name
© Canadian Standards Association
March 2004
Table A.7 (Continued)
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Table A.7 (Continued)
Name
Description
Control
(d) Stabbing or puncture
The body may be penetrated by the
following:
(a) flying objects:
(i) ejection of parts of machinery,
e.g., the flying shuttle of a loom,
a loose cutter on a vertical spindle
moulding machine, broken tooling
on a press, or the bursting of an
abrasive wheel; and
(ii) ejection of material, e.g., flying
swarf, ejection of a workpiece,
molten metal ejection from a
die-casting machine, sparks
generated in a welding process,
cartridge tools, or debris from
rotary mowers and hedge-cutters;
and
(b) rapidly moving parts of machinery
or pieces of material, e.g., sewing
machines, drilling machines.
Stabbing or penetration injuries are
affected by sharpness, speed, force or
torque, and inertia of machine parts,
process material, by-products, etc., in
their normal places or on ejection from
the machinery. The presence of a
surface preventing the body or body
part moving away may aggravate
the effect.
Where there is a risk of small or sharp
ejected objects that may penetrate
the skin, sheet material should be
considered in lieu of mesh for guards.
© Canadian Standards Association
March 2004
(Continued)
Name
Description
Control
(e) Impact
Impact hazards are caused by objects that
act against the inertia of the body but do
not penetrate it, e.g., the traversing
motion of a machinery part, oscillating
pendulum movements, striking by
projections or moving counterweights.
The considerations for impact
injuries are much the same as for
stabbing or penetration injuries.
100
Safeguarding of machinery
(Continued)
© Canadian Standards Association
March 2004
Table A.7 (Continued)
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101
Table A.7 (Continued)
Name
Description
Control
(f) Crushing
Crushing occurs when one part of
machinery moves against another with a
part of the body in between, e.g., the ram
of a forging hammer, the tools of power
presses, the calipers of spot welding
machines, garment press closure, the
closing nip between two platen motions,
hand-fed platen machines, foundry
moulding machines, counterweights.
The traversing motion of a machinery
part, e.g., the table of a machine tool,
and a fixed structure not being part of
the machinery may also create this type
of hazard.
Crushing injuries, like shear injuries,
are due to the relative motion of two
objects with a body part in between,
and are affected by similar
considerations.
Counterweight
March 2004
© Canadian Standards Association
(Continued)
Name
Description
Control
(g) Drawing–in
Shearing or crushing injuries can be
caused when a part of the body is drawn
into a running or in-running nip formed
in the following ways:
(a) in-running nips between two
counter-rotating parts, e.g., meshing
gears, rolling mills, mixing rolls, press
rolls, reel and carriage rolls, dough
brakes and moulders or calenders;
(b) in-running nips between a rotating
surface and a tangentially moving
surface, e.g., power transmission
belt and pulley, chain and chain
wheel, rack and pinion; and
(c) running nips between a rotating
surface and a tangentially moving
surface where material, e.g., metal,
paper, cable and rope, runs on to
a reel, drum or shaft.
Drawing-in, leading to entanglement,
shear or crushing, is aggravated by
speed or distance of movement, force,
torque, inertia, weight, or tension, e.g.,
in a belt or in material being reeled up.
Surface roughness and any tendency
to adhesion will have a similar effect.
Adjacent parts of structures may
increase injuries.
Ejection—
disintegration of wheel
Contact with
abrasive surface
In-running trap with
incorrectly positioned
work rest
Ejection—
sparks and debris
Entanglement
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Table A.7 (Concluded)
© Canadian Standards Association
March 2004
© Canadian Standards Association
Safeguarding of machinery
Annex B (informative)
Illustrations of other hazard controls
Note: This Annex is not a mandatory part of this Standard.
INCORRECT
1 position switch and one
end firmly anchored
Switch 1
(a) Emergency stop pull-cord installed incorrectly
(Continued)
Notes:
(1) Internal detail of a typical switch is shown in Figure B.1(c).
(2) This shows an incorrect installation with a switch at one end and the pull cord firmly anchored at the other. The device
will be inoperative if the pull-cord is pulled in the direction shown.
Figure B.1
Emergency stopping of conveyors
(See Clause 7.17.3.2.)
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CORRECT
2 position switches
Switch 2
Tension
spring
anchor
Switch 1
CORRECT
1 position switch and
1 tension spring anchor
Switch 1
(b) Two methods of installing an emergency stop pull-cord correctly
(Continued)
Notes:
(1) Internal detail of a typical switch is shown in Figure B.1(c).
(2) This illustration shows two methods of installing an emergency stop pull-cord correctly. Either a switch is provided at
each end or a single switch is used at one end and a tension spring anchors the other end so that a pull on the cord in
any direction will stop the conveyor. It should be emphasized that an emergency stop pull-cord is not an alternative to
guarding.
Figure B.1 (Continued)
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C
Safeguarding of machinery
A
B
D
(c) Electrical switch for emergency stopping conveyors
Note: A switch operated by an emergency stop pull-cord should cut off the power supply not only when the cord is pulled
but also if the pull-cord breaks or becomes slack. (See also Figure B.1(b).) The switch illustrated has a central spindle to
which a pull-cord is connected at D. Tension in the pull-cord is so adjusted that the switch contacts are closed (positive A) to
allow the conveyor to run. A pull on the cord will open the contacts (position B) while breakage or slackness of the pull-cord
will cause them to open in the opposite direction (position C) under the action of the compression spring.
At a long conveyor, instead of a number of separate emergency stopping devices, it is sometimes more effective to install
an emergency stop pull-cord (wire or rope) along the whole length of the conveyor. A pull on the cord in any direction, or
breakage of the pull-cord, will bring the conveyor to rest. The arrangement should be such that after manual operation
resetting is necessary.
Figure B.1 (Concluded)
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Flat plate
© Canadian Standards Association
Angle section
Angle section
Note: Access to a running nip can be prevented by means of a flat plate or angle section as shown.
Figure B.2
Use of flat plate or angle section to
prevent access to in-running nips
(See Figure B.5.)
Gap “B”
A
C
Danger
point
Note: When material such as cardboard has to be fed to a pair of rollers, and a gap is necessary to permit the free flow
of the material, the relationship of distance A to gap B should be in accordance with this Standard, so that a person
cannot reach the intake. The dimensions C will vary with the size of the rollers. As the roller diameter increases, C will
need to be increased.
Figure B.3
Feeding material to a pair of rollers
(See Figure B.5.)
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Safeguarding of machinery
Angle bar
Narrow slot
Table
Note: The angle bar above the table forms the guard, which should be set at the smallest distance above the table
consistent with feeding the material through the narrow slot and keeping the in-running nip inaccessible.
Figure B.4
Small horizontal table, stiffened to prevent deflection,
spanning the full width of a calender
B
A
C
Note: A guard consisting of two fixed curved metal plates provides a narrow gap A for feeding materials while effectively
preventing access to a nip between the rolls. The clearance at A, B, and C, and at similar gaps shown in Figures B.2
and B.3, should be small enough to prevent access.
Figure B.5
Use of fixed curved metal plates to
prevent access to in-running nips
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Signal to
Spring release guard
applied bolt
E
Guard closed
Positively
operated valve
Press ram
cylinder
Negatively operated
interlock valve
(a) This shows the more common type of control guard arrangement in the closed position. The bolt is engaged
preventing the guard from being opened and enabling the positively operated valve. The negatively operated
interlock valve is actuated by the guard allowing the press to downstroke. When the operation is completed,
a delay valve or pressure switch can be used to signal the bolt to withdraw, thus allowing the guard to spring open.
Spring
applied bolt
Signal to
release guard
Guard open
E
Positively
operated valve
Press ram
cylinder
Negatively operated
interlock valve
(b) This shows a vertical sliding guard in an open position. The spring applied bolt is prevented from moving by
the guard, and the press ram cylinder is prevented from operating by the negatively operated interlock valve
and the positively operated valve.
Figure B.6
Control guard for a pneumatic or hydraulic press
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Safeguarding of machinery
Note: The guard is telescopic to provide ready adjustment to the surface of the workpiece and is attached to a vertical
hinge to permit access to the spindle for drill changing.
Figure B.7
Adjustable guard for a radial or pedestal drilling machine
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Fixed guard
Transparent panel
False table
Note: The false table is supported on the traversing table and is shaped so that the components can be readily
clamped in the vise well away from the cutter, access to which is prevented by a fixed guard. A transparent panel
in the guard permits observation of the milling operation and the gaps beneath the false table permit clearance
of swarf.
Figure B.8
False table and fixed guard applied to milling machine
(See Clause 6.2.1.12.)
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Safeguarding of machinery
Moving die
Hinged guard
Mould
False table
Note: The false table fills the gap between the moulds, thus preventing access to the trap between the die and mould
from beneath the hinged interlocking guard. This guard should also be designed to act as a trip device. This prevents
injury by stopping the machine if the operator gets caught between the mould and the guard.
Figure B.9
False table and interlocking guard applied to
a rotating table pie and tart machine
(See Clause 6.2.1.12.)
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Position switch
Cam
Note: Position switch operates in the positive (or direct) mode, with a cam mounted on the door hinge, profiled so
as to operate swiftly as the door is opened. The switch contacts are opened positively (directly) by the action of the
cam profile and closed by spring action when the door is closed.
Figure B.10
Position switches or valves actuated by rotary cams
(See Table A.6.)
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Safeguarding of machinery
INCORRECT
position switch fails to danger
Note: This provides an example of incorrect application of a position switch as there is nothing to prevent wilful
interference with its working. It would, moreover, fail to danger in the event of the switch stem failing to extend
under the action of its return spring.
Figure B.11
Plunger operated position switch A, operating in the non-positive
mode, fitted to a door protecting a machinery hazard
(See Table A.6.)
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Key free
Key trapped
Access lock
Guarding
The access lock is a two-part mechanical device
and can be opened using only the key from the
lock on the circuit breaker.
ON
Mechanical bolt lock
OFF
Main
breaker
The mechanical bolt lock is mechanically linked
with the main circuit breaker, such that the key
cannot be released while the breaker is “ON”.
Gate locked closed — power on
(Continued)
Figure B.12
Example of trapped key interlocking system
(See Clauses 9.3.2, 9.3.3, and 10.2.4.)
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Safeguarding of machinery
Safety or personnel key
Key free
Key trapped
Side
bolt
Guarding
ON
Access lock
The key from the mechanical bolt lock is inserted into the
bottom portion of the access lock. This allows the top key to
be turned and removed (trapping the bottom key). When the
top key has been removed, the side bolt can be removed and
the gate opened. The top key is taken into the safeguarding
space, ensuring power cannot be restored.
OFF
Main
breaker
Mechanical bolt lock
When the key is turned and removed, the bolt extends and
locks the cam in place (the “OFF” position). The breaker
cannot be turned “ON” without the key in place.
Gate open — power off
Figure B.12 (Concluded)
March 2004
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Switching knob
Cam
Switching element
Switching element
Switching knob
Actuator — top view
Dual action actuator
Actuator — side view
Safety interlock switches
The positively opening switching element is directly driven by a cam. The cam and the switching element are
structurally connected, forming one functional unit in the switching process. An actuator (key) operates the
switch through a positive interlocking switching mechanism at the switching knob. Dual action design is
preferred for tamper-resistance purposes and required for operation.
Figure B.13
Safety interlock switches
(See Clauses 9.3.3 and 10.2.4.)
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Safeguarding of machinery
Area of focus
Utilizing the direct drive characteristics of the switch, the contacts
will be forced open even in the event of a welded contact. Safety is
not dependent on the spring return.
(a) Preferred method
Notes:
(1) The movable portion of the barrier guard should be guided to ensure that contact with the switch actuator
is maintained.
(2) The switch should be permanently mounted or monitored so that a loose or detached switch will not cause
an unsafe operation. A keyed actuator or redundant switches should be considered if not achievable.
(See Figures B.12 and B.13.)
(Continued)
Figure B.14
Switch illustrations
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Area of focus
The system relies on a spring return to apply the stopping action; in
the case of a failed spring or welded contact, this design could result
in a failure to stop hazardous motion when required.
(b) Not recommended
(Continued)
Figure B.14 (Continued)
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Safeguarding of machinery
See Notes to Figure B.14(a).
(c) Roller type limit shown utilizing direct drive or positive opening for machine stop
(Continued)
Figure B.14 (Continued)
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Door shown fully closed
Limit 1
Door shown open
Limit 2
Limit 1
Limit 2
(d) Redundant limit switches used in a complementary fashion
Figure B.14 (Concluded)
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Safeguarding of machinery
Although light curtains are shown, the dimensions illustrated are
applicable to all optical PSSDs (single beams and scanners).
Dpf determined by Os and installation
(Assumes there are no other safeguards and no
physical obstructions limiting access to the hazard)
“Reach through”
“Reach over”
First beam at 0.3 m (12 in) max First beam at 0.3 m (12 in) max
Top beam at 1.2 m (48 in) min Top beam at 0.9 m (36 in) min
Object sensitivity (Os) is less than 64 mm (2.5 in)
Dpf = 3.4 × (Os – 6.875 mm)
Dpf = 3.4 × (Os – 0.275 in)
but not less than 0
1.2 m
(48 in)
min
Dpf = 1.2 m (48 in)
0.9 m
(36 in)
min
0.3 m (12 in) max
Os is equal to or greater than 64 mm (2.5 in)
AND does not exceed 0.6 m (24 in)
Dpf = 1.2 m (48 in)
Dpf = 0.9 m (36 in)
1.2 m
(48 in)
min
0.9 m
(36 in)
min
0.3 m (12 in) max
(a) Optical PSSDs — Vertical field
(Continued)
Figure B.15
Anthropomorphic safety distances
(See Clauses 6.2.2.3.3 and 10.12.)
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Horizontal detection field
when PSSD is used to signal a stop
Dpf = 1.2 m (48 in)
(Assumes there are no other safeguards and no physical
obstructions limiting access to the hazard)
Depth of field
Depth of detection
(depth of mat,
length of light curtain,
scanner coverage)
=
Dpf
(but depth of field is not
to be less than 0.9 m [36 in])
If physical obstructions exist, depth of field may be reduced
to 0.9 m (36 in), even though the Dpf remains 1.2 m (48 in).
H
Safety mat
on a platform
(See Note 1)
H
Light curtain or scanner
Notes:
(1) With optical PSSDs mounted horizontally, supplemental safeguarding may be
needed if H –> 0.3 m (12 in) and there are no physical obstructions limiting
access to the hazard. See Figure B.15(g), about Os and H.
(2) H is the height above the adjacent walking surface.
(3) Horizontal-sensing PSSDs are installed such that personnel cannot lean
or leverage themselves such that their presence is not sensed by the PSSD.
(b) PSSD depth penetration factor (Dpf)
(Continued)
Figure B.15 (Continued)
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Safeguarding of machinery
Instead of
a light curtain,
a safety mat or
area scanner
may be used
for walk-through
detection
0.3 m (12 in) max
Dpf
Ds
(safety distance)
Dpf
30º shown
Ds
If angle is equal to or greater than 30º, Dpf is the same as the
vertical PSSD field. If angle is less than 30º, horizontal field
requirements apply.
Operator interface/point of operation safeguarding
For operator interface/point of operation safeguarding,
a) complete coverage is required: NO gaps in coverage and NO undetected walk-through;
b) safeguarding should be installed so that the hazard ceases before it can be accessed by personnel; and
c) if PSSDs are used to signal the hazard to cease, presence is continuously sensed to prevent restart.
Note: Due to space constraints, Ds and Dpf are not like-sized for these graphics.
(c) Complete coverage safeguarding
(Continued)
Figure B.15 (Continued)
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H
Ds
Ds = 1.6 m/s × (Ts +Tc + Tr)
= 63 in/s × (Ts + Tc + Tr)
(safety distance)
Notes:
(1) Tr may include a deduct for the delay in accessing the hazard, including the delay caused when a person’s access
is slowed due to the mechanics of opening the barrier. This deduct should be objectively measured if it is to be used.
(2) H is the height above the adjacent walking surface.
(3) Not all safeguards are shown, in order to illustrate better the interlocked barrier’s installation.
Interlocked barriers
For operator interface/point of operation safeguarding, access is by opening the interlocked barrier without
full body access. (Typically full body access is an “entry” door or gate that is not an operator interface/point
of operation.)
The barrier is sized such that a person cannot reach over, under, around, or through (guard, opening, table)
and access the hazard.
The barrier is located such that the hazard ceases before a person would access the hazard. The interlocking
device’s switching action is a factor in the installation. For example, the switch actuation on a hinged door
may be angular, which would limit the door opening size or require greater installed distance if an arm
could reach inside the barrier before the switch actuates.
(d) Interlocked barrier safety distance (Ds)
(Continued)
Figure B.15 (Continued)
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Safeguarding of machinery
closest
hazard
H
Depth of field
Dpf
When used to signal a stop
Ds = 1.6 m/s × (Ts + Tc + Tr) + Dpf
= 63 in/s × (Ts + Tc + Tr) + Dpf
Ds (safety distance)
where
Dpf = 1.2 m (48 in)
Depth of field/depth of detection = Dpf typically
Depth of field may be reduced due to physical obstructions preventing access.
The minimum depth of field is 0.9 m (36 in).
Operator interface/point of operation safeguarding
For operator interface/point of operation safeguarding,
(a) complete coverage is required: NO gaps in coverage and NO undetected walk-through (may be
accomplished with one or more safeguards);
(b) a minimum depth of field may result in the sensing field starting at greater than the safety distance
formula; and
(c) safeguarding should be installed so that the hazard ceases before it can be accessed by personnel and
so that presence is continuously sensed with PSSDs to prevent restart.
Notes:
(1) H is the height above the adjacent walking surface. H has limitations, depending on Os and supplemental
safeguarding. If H is greater than 0.3 m (12 in), supplemental safeguarding may be required.
(2) Not all safeguards are shown, in order to illustrate better the scanner’s installation.
(e) Area scanner safety distance (Ds)
(Continued)
Figure B.15 (Continued)
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Depth of field
Dpf
When used to signal a stop
Ds = 1.6 m/s × (Ts + Tc + Tr) + Dpf
= 63 in/s × (Ts + Tc + Tr) + Dpf
H
Ds
(safety distance)
where
Dpf = 1.2 m (48 in)
Notes:
(1) Although a safety mat is shown, this illustration is applicable to other horizontal PSSDs.
(2) Not all safeguards are shown, in order to better illustrate the safety mat’s installation.
Depth of field/depth of detection = Dpf typically
Depth of field may be reduced due to physical obstructions preventing access.
The minimum depth of field is 0.9 m (36 in).
closest hazard
Operator interface/point of operation
safeguarding
safety distance
Dpf
no gaps;
complete
coverage
0.9 m (36 in)
Min. depth
of field
For operator interface/point of operation safeguarding,
a) complete coverage is required: NO gaps in
coverage and NO undetected walk-through;
b) minimum depth of field may install edge of sensing
at greater than the safety distance formula; and
c) safeguarding should be installed so that the hazard
ceases before it can be accessed by personnel and
so that presence is continuously sensed with PSSDs
to prevent restart.
(f) Safety mats safety distance (Ds)
(Continued)
Figure B.15 (Continued)
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Safeguarding of machinery
Allowable field heights (H)
H (mm) = 15 x (Os – 50 mm)
H (in) = 15 x (Os – 2 in)
Object sensitivity
(Os), mm (in)
_
<
_
<
_
<
_
<
64
76
89
102
≤ 50 (2.0)
(2.5) < 76
(3.0) < 89
(3.5) < 102
(4.0) < 117
_ 117 (4.6)
<
Mounting height, mm (in)
Min.
Max.
(3.0)
(3.5)
(4.0)
(4.6)
0 ( 0.0) – 990 (39)
178 ( 7.0) – 990 (39)
381 (15.0) – 990 (39)
572 (22.5) – 990 (39)
762 (30.0) – 990 (39)
990 (39.0) – 990 (39)
Depth of field
Note: Mounting heights above 0.3 m (12 in) may require
supplemental safeguarding to prevent crawling or ducking
under the horizontal PSSD.
Dpf
= 1.2 m (48 in)
Ds
(safety distance)
Notes:
(1) For operator interface/point of operation safeguarding, complete coverage is required such that the hazard
ceases before any access by personnel.
(2) Not all safeguards are shown, in order to better illustrate the application issue. A light curtain is shown;
however, it may be a safety scanning device.
Depth of field (depth of detection) is not less than 0.9 m (36 in)
If H is greater than 0.3 m (12 in), supplemental safeguarding may be required to detect crawling underneath.
If H is less than or equal to 0.3 m (12 in), then Os is less than 70 mm (2.7 in).
If H is installed at 0.6 m (24 in), then Os is less than 110 mm (4.3 in).
light curtain shown
(may also be a safety scanner)
light curtain shown
(may also be a safety scanner)
Depth of field
Depth of field
H
Dpf
Dpf
Ds
(safety distance)
Ds
(safety distance)
(g) Horizontal optical PSSDs: Os and H
Figure B.15 (Concluded)
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Annex C (informative)
Ergonomic data
Notes:
(1) This Annex is not a mandatory part of this Standard but is written in mandatory language to accommodate
its adoption by anyone wishing to do so.
(2) The information given in this Annex is based on that given in ISO 13852.
(3) This data does not apply to situations in which children have access to machinery.
C.1 Reaching upwards (See Figure C.1)
If there is a low risk from the danger zone, then the height of the danger zone h shall be 2500 mm or
more.
If there is a high risk from the danger zone, then
(a) either the height of the danger zone h shall be 2700 mm or more; or
(b) other safety measures shall be used.
Danger zone
h
Reference plane
Figure C.1
Safety distance for reaching upwards
(See Clause C.1.)
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C.2 Reaching over protective structures
C.2.1 General
Distance guards used as perimeter fences should be at least 1800 mm high. The data given in
Clause C.2.2 for barriers less than 1800 mm high should only be used where the 1800 mm height is
not reasonably practicable.
Note: Barriers are not foolproof and they cannot prevent access to persons intent on gaining access. Therefore, as a person's
intent on reaching a hazardous part increases, e.g., by climbing on chairs, ladders, or the barrier itself, the protection
provided by a barrier erected in accordance with Table C.1 will decrease.
C.2.2 Reaching over
When reaching over an edge, e.g., on machine frames or barriers, the safety distance is found in
Figure C.2 and Tables C.1 and C.2.
If there is a low risk from a danger zone, the values given in Table C.1 shall at least be used. There shall
be no interpolation of the values in this table (see examples). Consequently, when the known values of a,
b, or c are between two values in the tables, the values to be used shall be those that provide the highest
level of safety.
If there is a high risk from the danger zone, then either the values in Table C.2 or other safety measures
should be used.
There should be no interpolation of the values in Table C.1 or Table C.2.
See the following examples where values of Table C.1 have been used:
EXAMPLE 1:
The height of the danger zone, a, is 1500 mm and its horizontal distance, c, from the proposed protective
structure is 700 mm.
Using Table C.1, the height of the protective structure, b, should be at least 1800 mm.
EXAMPLE 2:
The height of the protective structure, b, is 1300 mm and the height of the danger zone, a, is 2300 mm.
Using Table C.1, the horizontal distance, c, of the protective structure from the danger zone shall be at
least 600 mm.
EXAMPLE 3:
The height of the protective structure, b, is 1700 mm and the horizontal distance, c, from the danger zone
is 550 mm.
Using Table C.1, the danger zone should not be between 1200 mm and 2200 mm high.
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Table C.1
Low risk values of a, b, and c for Figure C.2
(See Clause C.2 and Figure C.2.)
Height of fixed barrier or protective structure†
Height of
danger zone*
1000
1120
1400
1600
1800
2000
2200
2400
2500
Horizontal distance to danger zone
2500
—
—
—
—
—
—
—
—
—
2400
100
100
100
100
100
100
100
100
—
2200
600
600
500
500
400
350
250
—
—
2000
1100
900
700
600
500
350
—
—
—
1800
1100
1000
900
900
600
—
—
—
—
1600
1300
1000
900
900
500
—
—
—
—
1400
1300
1000
900
800
100
—
—
—
—
1200
1400
1000
900
500
—
—
—
—
—
1000
1400
1000
900
300
—
—
—
—
—
800
1300
900
600
—
—
—
—
—
—
600
1200
500
—
—
—
—
—
—
—
400
1200
300
—
—
—
—
—
—
—
200
1100
200
—
—
—
—
—
—
—
0
1100
200
—
—
—
—
—
—
—
* Protective structures less than 1000 mm in height are not included because they do not sufficiently restrict movement
of the body.
† For danger zones above 2500 mm, see Clause C.1.
Note: Dimensions are in millimetres.
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Safeguarding of machinery
Table C.2
High risk values of a, b, and c for Figure C.2
(See Clause C.2.2 and Figure C.2.)
Height of protective structure†
Height of
danger zone*
1000
1200
1400
1600
1800
2000
2200
2400
2500
2700
Horizontal distance to danger zone‡
2700
—
—
—
—
—
—
—
—
—
—
2600
900
800
700
600
600
500
400
300
100
—
2400
1100
1000
900
800
700
600
400
300
100
—
2200
1300
1200
1000
900
800
600
400
300
—
—
2000
1400
1300
1100
900
800
600
400
—
—
—
1800
1500
1400
1100
900
800
600
—
—
—
—
1600
1500
1400
1100
900
800
500
—
—
—
—
1400
1500
1400
1100
900
800
—
—
—
—
—
1200
1500
1400
1100
900
700
—
—
—
—
—
1000
1500
1400
1000
800
—
—
—
—
—
—
800
1500
1300
900
600
—
—
—
—
—
—
600
1400
1300
800
—
—
—
—
—
—
—
400
1400
1200
400
—
—
—
—
—
—
—
200
1200
900
—
—
—
—
—
—
—
—
0
1100
500
—
—
—
—
—
—
—
—
* Protective structures less than 1000 mm in height are not included because they do not sufficiently restrict movement
of the body.
† For danger zones above 2500 mm, see Clause C.1.
‡ Protective structures lower than 1400 mm should not be used without additional safety measures.
Note: Dimensions are in millimetres.
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Danger zone
b
Reference plane
a
c
Protective structure
Figure C.2
Dimensions a, b, and c used in Table C.1 and Table C.2
(See Clause C.2.2 and Tables C.1 and C.2.)
C.3 Reaching round
When reaching round edges in any position the safety distance of freely articulating body parts of persons
over the age of 14 is given in Table C.3.
The radius of the movement about a fixed edge is determined by the reach of given body parts.
The safety distances assigned should be respected as a minimum if the body part concerned is not to
be allowed to reach a danger zone.
Of special importance is the danger zone which can be reached when these body parts are introduced
through slots.
When applying safety distances, it is to be assumed that the basic joint component of the relevant body
part is in fixed contact with the edge. The safety distances apply only if it is ensured that further advance
or penetration of the body part towards the hazard is excluded.
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Safeguarding of machinery
Table C.3
Safety distances
(See Clause C.3.)
Limitation of movement
Safety distance sr, mm
Limitation of movement only
at shoulder and armpit
≥ 915
Illustration
#132*
A
sr
Arm supported up to elbow
≥ 550
#120*
A
$300
Arm supported up to wrist
sr
≥ 230
#120*
A
$620
Arm and hand supported up to
knuckle joint
sr
≥ 130
#120*
A
$720
sr
A = range of movement of the arm
* Either the diameter of the round opening, or the side of a square opening, or the width of a slot opening.
C.4 Reaching through regular openings
Safety distances, sr, for persons aged 14 and above are given in Table C.4.
The dimensions of openings, e, correspond to the side of a square, the diameter of a round opening,
and the narrowest dimension of a slot opening.
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Table C.4
Safety distances, sr, through regular openings of size e
(See Clauses C.4 and C.5.)
Safety distance, sr
Part of body
Illustration
Fingertip
Opening
e≤4
sr
Slot,
mm
Square,
mm
Round,
mm
≥2
≥2
≥2
4<e≤6
≥ 10
≥5
≥5
6<e≤8
≥ 20
≥ 15
≥ 20
8 < e ≤ 10
≥ 80
≥ 25
≥ 80
10 < e ≤ 12
≥ 100
≥ 80
≥ 120
12 < e ≤ 20
≥ 120
≥ 120
≥ 120
20 < e ≤ 30
≥ 850*
≥ 120
≥ 120
30 < e ≤ 40
≥ 850
≥ 200
≥ 120
40 < e ≤ 132
≥ 915
≥ 915
≥ 915
e
Finger up to knuckle joint
or hand
sr
e
sr
e
Arm up to junction
with shoulder
sr
e
* If the length of the slot opening ≤ 65 mm, the thumb sill acts as a stop and the safety distance can be reduced
to 200 mm.
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Safeguarding of machinery
C.5 Openings of irregular shape
To choose a safety distance for an opening of irregular shape, refer to Table C.4 using either the
smallest circular aperture, d, that describes the opening, or the narrowest slot with parallel sides, e, that
will contain the opening (see Figure C.3). The smallest safety distance arrived at using this method may be
employed.
d
e
Figure C.3
Safety distances for openings of irregular shape
(See Clause C.5.)
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Annex D (informative)
Selection of interlocking systems
Notes:
(1) This Annex in not a mandatory part of this Standard.
(2) This Annex is based on ISO 13849-1.
D.1
This Annex is intended to provide a graphical method of carrying out the selection process outlined in
Clause 6.2.2.2. While it provides a more formal approach it should be recognized that it has limitations
due to the lack of data available.
D.2
Having assessed the severity and probability of injury if the interlocking system fails (see Clause 6),
select the equivalent points on scales A and C of Figure D.1.
This assessment will be influenced by
(a) the method of working the machinery;
(b) the nature of the hazard; and
(c) the need to approach it.
Any operating histories and accident records for the machinery should also be taken into account.
D.3
Using a straightedge, connect these points to obtain an intersection point, y, on scale B.
D.4
Select a point, x, on scale D equivalent to the expected frequency of approach.
D.5
Project a horizontal line from the point y and a vertical line from the point x. The area in which these
lines intersect gives an initial indication of the outlay in time, money, and effort that should be spent
on the interlocking system to reduce the risk of injury to an acceptable level.
If the intersection falls in area P, the indication is that the outlay will be sufficient to provide for a single
channel control system of interlocking. Intersections falling above area P will indicate that a greater outlay
is warranted, allowing provision for higher integrity interlocking systems as follows:
(a) Area Q: dual channel control system interlocking without cross-monitoring.
(b) Area R: interlocking guard power interlocking.
(c) Area S: either dual channel control system interlocking with cross-monitoring or interlocking
guard with guard locking power interlocking.
The intersection may fall into one of the shaded portions of areas P, Q, R, or S. Where this occurs,
the merits and cost of using higher quality components, to improve the reliability of the interlocking
system provided for below the shaded portion, should be compared with the merits and cost of
providing a system of interlocking provided for above the shaded portion.
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Safeguarding of machinery
Before the final selection is made, the merits of an interlocking system requiring an initially higher
capital outlay but with lower inspection and maintenance costs should be compared with an initially
cheaper system requiring higher inspection and maintenance costs.
Scale A
Scale C
Fatal
Inevitable
S
Amputation of
a limb
Probable
R
Amputation of a
hand or foot
Scale B
Q
Amputation of a
finger or toe
Possible
P
Remotely
possible
Bruise
5
2
days days
Potential severity
of injury
1
day
1 30 10
hr. min. min.
Frequency of approach
(once in every ...)
Scale D
1
min.
or less
Probability of
injury if interlock fails
Figure D.1
Graphical method for selecting interlocking systems
(See Clause D.2.)
March 2004
137
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