INSTITUTION OF GAS ENGINEERS AND MANAGERS
IGEM/UP/19 Edition 1
Communication XXXX
IGEM/TSP/12/153
Founded 1863
Royal Charter 1929
Patron
Her Majesty the Queen
THE DESIGN, SPECIFICATION AND APPLICATION OF INTERLOCK
DEVICES USED WITHIN COMMERCIAL AND INDUSTRIAL
APPLICATIONS INCLUDING CATERING
DRAFT FOR COMMENT
1
This draft Standard IGEM/UP/19 Edition 1 has been prepared by IGEM Secretariat.
2
This Draft for Comment is presented to Industry for comments which are required by 31st
August 2012, and in accordance with the attached Reply Form.
3
This is a draft document and should not be regarded or used as a fully approved and
published Standard. It is anticipated that amendments will be made prior to publication.
It should be noted that this draft Standard contains intellectual property belonging
to IGEM. Unauthorised copying or use by any unauthorised person or party is not
permitted.
4
This is a copyright document of the Institution of Gas Engineers and Managers. Enquiries
should be addressed in the first instance to:
Peter Hurst
IGEM
IGEM House
High Street
Kegworth
Derbyshire, DE74 2DA
Tel: 0844 375 4436
Fax: 01509 678198
Email: peter@igem.org.uk
IGEM/UP/19
Communication XXXX
The design, specification and application
of
interlock
devices
used
within
commercial and industrial applications
including catering
Draft for comment
Founded 1863
Royal Charter 1929
Patron: Her Majesty the Queen
IGEM/UP/19
Communication XXXX
The design, specification and application
of
interlock
devices
used
within
commercial and industrial applications
including catering
Draft for comment
Price Code: C35
© The Institution of Gas Engineers and Managers
IGEM House
26-28 High Street
Kegworth
Derbyshire, DE74 2DA
Tel: 0844 375 4436
Fax: 01509 678198
Email: general@igem.org.uk
Copyright © 2012, IGEM. All rights reserved
Registered charity number 214001
All content in this publication is, unless stated otherwise, the property of IGEM. Copyright laws
protect this publication. Reproduction or retransmission in whole or in part, in any manner,
without the prior written consent of the copyright holder, is a violation of copyright law.
ISBN 978 1 905903 XX X
ISSN 0367 7850
Published by the Institution of Gas Engineers and Managers.
For information on other IGEM Standards go to, www.igem.org.uk
IGEM/UP/19 – Draft for comment
CONTENTS
SECTION
PAGE
1
Introduction
1
2
Scope
3
3
Legal and Allied Considerations
4
4
Design and Construction
9
5
Application of Interlocks
10
6
Maintenance and inspection
14
7
User instructions
14
8
Records
14
9
Catering installations
15
9.1
Ventilation system design – general aspects
15
9.2
Mechanical ventilation system interlock requirements
16
9.3
Cooker canopies
17
9.4
Assessing the effectiveness of existing ventilation provision or systems
17
9.5
Testing equipment for measuring CO2
18
9.6
Testing
18
9.7
Existing systems
18
APPENDICES
1
Glossary, Acronyms, Abbreviations, Symbols and Units
20
2
References
22
3
Specification and testing of control systems
25
1
Example of a weep by-pass proving system
13
2
Example of a weep by-pass proving system
13
3
Flowchart dealing with assessment protocol when dealing with gas-fired
commercial catering appliances
19
Open circuit test voltage  0% for AC mains systems
28
FIGURES
TABLES
1
©IGEM, IGEM House, 26-28 High St, Kegworth, Derbyshire, DE74 2DA. Website: www.igem.org.uk.
IGEM/UP/19 – Draft for comment
2
Open circuit output test voltages  10% and repetition rate of the
impulses  20%
29
3
Test voltages for conducted immunity on mains and I/O lines
30
4
Test levels for radiated immunity
31
5
Test voltages for direct and indirect electrostatic discharges
31
©IGEM, IGEM House, 26-28 High St, Kegworth, Derbyshire, DE74 2DA. Website: www.igem.org.uk.
IGEM/UP/19 – Draft for comment
SECTION 1 : INTRODUCTION
1.1
Interlocks are provided to ensure the safety of a system should a component fail
that might then lead to a risk to persons. This publication concerns the design,
specification and application of interlock systems used in non-process
applications and within catering installations. For process applications reference
should also be made to IGE/UP/12 (see Appendix 2).
1.2
This Standard has been drafted by a Panel appointed by the Institution of Gas
Engineers and Managers’ (IGEM’s) Gas Utilization Committee, subsequently
approved by that Committee and published by the authority of the Council of
IGEM.
1.3
This Standard is not intended to deal with mechanical ventilation systems in
domestic applications although the principles of safety may be similar. In such
cases reference should be made to the appropriate Standard.
1.4
Interlocks are used for a wide range of systems, generally in association with
mechanical fanned ventilation or flue systems. They can also be applied in
association with fire and gas detection systems.
1.5
The requirements for catering installations are in line with Gas Safe Technical
Bulletin TB 140 issued in 2012. This describes two types of appliance as follows:

Type ‘A’ appliance. ‘An appliance not intended to be connected to a
flue or a device for evacuating the product of combustion to the outside of the
room in which the appliance is installed’

Type ‘B’ appliance. ‘An appliance intended to be connected to a flue
that evacuates the product of combustion to the outside of the room containing
the appliance. The combustion air is drawn direct from the room’.
1.5
Interlocks are required by IGEM standards on industrial and commercial
pipework IGEM/UP/2, for gas engines IGE/UP/3, during commissioning
IGEM/UP/4, for compressors IGEM/UP/6, in plant rooms IGE/UP/10, for
educational establishments IGEM/UP/11 and for process plant IGE/UP/12.
1.6
Appendix x of this Standard contains performance requirements for use by the
designer and manufacturer during the selection of suitable components and
system design. They are not intended to require third party certification.
1.7
This Standard makes use of
notwithstanding Sub-Section 1.9,
the
terms
“must”,
“shall”
and
“should”

the term “must” identifies a requirement by law in (GB) at the time of
publication

the term “shall” prescribes a requirement which, it is intended, will be
complied with in full and without deviation

the term “should” prescribes a requirement which, it is intended, will be
complied with unless, after prior consideration, deviation is considered to be
acceptable.
Such terms may have different meanings when used in legislation, or HSE
ACoPs or guidance, and reference needs to be made to such statutory legislation
or official guidance for information on legal obligations.
1.8
The primary responsibility for compliance with legal duties rests with the
employer. The fact that certain employees, for example “responsible engineers”
1
IGEM/UP/19 – Draft for comment
are allowed to exercise their professional judgement does not allow employers
to abrogate their primary responsibilities. Employers must:

have done everything to ensure, so far as is reasonably practicable, that
there are no better protective measures that can be taken other than relying
on the exercise of professional judgement by “responsible engineers”

have done everything to ensure, so far as is reasonably practicable that
“responsible engineers” have the skills, training, experience and personal
qualities necessary for the proper exercise of professional judgement


have systems and procedures in place to ensure that the exercise of
professional judgement by “responsible engineers” is subject to appropriate
monitoring and review
not require “responsible engineers” to undertake tasks which would
necessitate the exercise of professional judgement that is not within their
competence. There should be written procedures defining the extent to
which “responsible engineers” can exercise their professional judgement.
When “responsible engineers” are asked to undertake tasks which deviate
from this they should refer the matter for higher review.
1.9
Notwithstanding Sub-Section 1.7, this Standard does not make obligatory the
use of any method or specification against the judgement of the “responsible
engineer”. New and improved practices may be adopted prior to this Standard
being updated. Amendments to this Standard will be issued when necessary and
their publication will be announced in the Journal of IGEM and elsewhere as
appropriate.
1.10
It is now widely accepted that the majority of accidents in industry are in some
measure attributable to human as well as technical factors in the sense that
people’s actions initiated or contributed to the accidents or people might have
acted better to avert them.
It is therefore necessary to give proper consideration to the management of
these human factors and to the control of risk. To assist in this, it is
recommended that due cognisance be taken of HSG65 and HSG48.
1.11
Requests for interpretation of this Standard in relation to matters within its
scope, but not precisely covered by the current text, should be addressed in
writing to Technical Services, IGEM, IGEM House, High Street, Kegworth,
Derbyshire, DE74 2DA and will be submitted to the relevant Committee for
consideration and advice, but in the context that the final responsibility is that of
the engineer concerned. If any advice is given by or on behalf of IGEM, this
does not relieve the responsible engineer of any of his or her obligations.
1.12
This Standard was published in xxxxx 2012.
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IGEM/UP/19 – Draft for comment
SECTION 2 : SCOPE
2.1
This Standard describes and classifies the various interlock systems used in
association with gas appliance installations in commercial and industrial
premises. It also provides the essential design and specification requirements
for interlock systems.
Note:
2.2
It is accepted that in some existing and very small installations that engineering judgement
may be needed to determine a cost effective option whilst ensuring the safety of persons.
This Standard describes the use and application of interlock systems. Such
systems may be required by relevant Standards to be applied in conjunction
with:





mechanical air supplies and extracts
fan extract systems
fire and gas detection systems
induced draught flue systems
fan diluted flue systems.
Note:
Relevant standards include BS 6173, BS 6644, IGEM/UP/2, IGE/UP/3, IGEM/UP/4,
IGEM/UP/6, IGE/UP/10, IGEM/UP/11 and IGE/UP/12.
2.3
In this Standard gas includes heavier and lighter than air flammable gases such
as Towns (manufactured) gas, NG, LPG, LPG/air and biogases.
2.4
This standard is not intended to be retrospectively applied to existing systems.
Note:
Rarely do standards cover the retrospective issue of existing installations. They can,
however, set a basis for consideration of performance upon which a risk assessment can be
developed. Where appropriate, ventilation checks for CO2 levels may need to be performed.
It can be argued that any improvements in safety are better than none at all. It may be
unreasonable to expect that an old installation should be brought right up-to-date in all
respects. Where a major refurbishment of the installation takes place, it would be
reasonable to consider the installation as a New Installation as far as is reasonably
practicable.
2.5
Pressures quoted are gauge pressures unless otherwise stated.
2.6
Italicised text is informative and does not represent formal requirements.
2.7
Appendices are informative and do not represent formal requirements unless
specifically referenced in the main sections via the prescriptive terms “must”,
“shall” or “should”.
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SECTION 3 : LEGAL AND ALLIED CONSIDERATIONS
3.1
GENERAL
3.1.1
This Standard is set out against a background of legislation in force in GB at the
time of publication. The devolution of power to the Scottish, Welsh and Northern
Ireland Assemblies means that there may be variations to the legislation
described below for each of them and consideration of their particular
requirements must be made. Similar considerations are likely to apply in other
countries where reference to appropriate national legislation is necessary.
All relevant legislation must be applied and relevant Approved Codes of Practice
(ACoPs), official Guidance and referenced codes, standards, etc. shall be taken
into account.
Note:
Appendix 2 is relevant in this respect.
Health and safety legislation must be observed, especially those requirements
which are concerned with the duties of employers, not only to their own
employees, but also to members of the public who may be affected.
3.1.2
Unless otherwise stated, the current editions of legislation and standards apply.
3.1.3
In the absence of specific legislation, it is essential that installations are
designed, constructed, installed, operated and maintained so as to be safe.
3.1.4
The legislation appropriate to any installation will depend largely upon its
location. Advice will need to be sought from the relevant Authorities.
3.1.5
Where British Standards, etc. are quoted, equivalent national or international
standards, etc. equally may be appropriate.
3.2
PRIMARY LEGISLATION
3.2.1
Health and Safety at Work etc. Act (HSWA)
HSWA applies to all persons involved with work activities, including employers,
the self-employed, employees, designers, manufacturers, suppliers, etc. as well
as the owners of premises. It places general duties on such people to ensure, so
far as is reasonably practicable, the health, safety and welfare of employees and
the health and safety of members of the public who may be affected by the
work activity.
3.3
SECONDARY LEGISLATION
3.3.1
Dangerous
(DSEAR)
Substances
and
Explosive
Atmospheres
Regulations
These Regulations are concerned with protection against risks from fire,
explosion and similar events arising from dangerous substances used or present
in the workplace. The regulations require that risks from dangerous substances
are assessed, eliminated or reduced. They contain specific requirements to be
applied where an explosive atmosphere may be present and require the
provision of arrangements to deal with accidents, emergencies etc. and
provision of information, training and use of dangerous substances. The
regulations also require the identification of pipelines and containers containing
hazardous substances.
The following
application:
publications
contain
4
details
of
the
regulations
and
their
IGEM/UP/19 – Draft for comment






INDG370
HSL134
HSL135
HSL136
HSL137
HSL138.
All gas systems except those in domestic parts of buildings fall within the scope
of DSEAR. This requires that a risk assessment be completed for each premise
to determine if any hazardous area exists and its extent. Normally, systems of
MOP not exceeding 0.5 bar do not require the use of certified electrical
components if correctly installed, tested and maintained.
3.3.2
Electricity at Work Regulations (EWR)
These Regulations apply to a wide range of electrical work, from overhead
power lines to the use of office computers and batteries and include work on gas
equipment using electrical energy.
The Regulations are concerned with the prevention of danger from electric
shock, electric burn, electrical explosion or arcing or from fire or explosion
initiated by electrical energy.
The Regulations impose duties on every employer, employee and self-employed
person and require that persons engaged in electrical work be competent or be
supervised by competent persons.
Note:
HSR25 provides guidance on the Regulations.
3.3.3
Gas Safety (Installation and Use) Regulations (GS(I&U)R)
3.3.3.1
GS(I&U)R are relevant statutory provisions of HSWA setting out general and
detailed requirements dealing with the safe installation, maintenance and use of
gas systems, including gas fittings, appliances and flues.
Note:
GS(I&U)R do not apply to certain premises (see HSL56 Guidance Notes 28 and 29).
However, where they do not apply, the principles of GS(I&U)R need to be applied,
notwithstanding that the requirement for Gas Safe Registration need not be applied.
3.3.3.2
GS(I&U)R address both Natural Gas and LPG.
3.3.3.3
GS(I&U)R place responsibilities on those installing, servicing, maintaining or
repairing gas appliances, pipework etc. as well as suppliers and users of gas.
3.3.3.4
GS(I&U)R define the gas supplier for both Natural Gas and LPG. HSL56 provides
guidance on those definitions, in particular for the more complicated case of LPG
supplied from storage vessels and from cylinders.
3.3.3.5
GS(I&U)R define the type of work that requires persons carrying out such work,
or their employers, to be an "approved class of person". In the UK this means
registration under the Gas Safe Register scheme.
3.3.3.6
The gas operative must check the safety of any appliance or pipework they
install or work on and take appropriate action where they find faults. Where the
premises are let or hired out, the landlord or hirer has special responsibilities to
ensure that any operative they use for the gas fitting, service or maintenance of
safety is a member of an approved class of persons (see clause 3.3.2.5) and is
competent to carry out such work. If any serious fault is found, the operative
must inform both the landlord/hirer, as well as the user, so that such faults can
be rectified before further use. Reference shall be made to the requirements
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IGEM/UP/19 – Draft for comment
contained in the Gas Industry Unsafe Situations Procedures (details are
available through Gas Safe Register).
Note:
3.3.3.7
Operatives working for ESPs may have limited responsibilities in this area.
GS(I&U)R place responsibilities on LPG suppliers to deal with escapes of LPG.
For Natural Gas, GS(M)R apply (see Sub-Section 3.2.8).
Note:
Further advice on GS(I&U)R is provided in HSL56.
3.3.4
Gas Safety (Management) Regulations (GS(M)R)
3.3.4.1
These Regulations are intended to cover the transport of NG to the public. They
do not cover gases such as LPG, coke oven gases etc (see HSL80 Regulation
2(1)).
3.3.4.2
Regulation 8 of GS(M)R places an obligation on GTs/gas conveyors not to
convey gas in a network unless the gas conforms with the requirements of Part I
of Schedule 3 of the Regulations (include a stenching agent) except that this
paragraph shall not apply where the gas is at a pressure above 7 bar.
3.3.4.3
GS(M)R (Regulations 7(4); 7(5) and 7(10)) place specific duties on GTs/gas
conveyors, or their emergency service providers (ESPs), for dealing with gas
escapes from pipes on their networks. Their primary duty is to make the
situation safe. They are responsible not only for dealing with escapes from their
own pipes, but also for dealing with escapes from gas fittings supplied with gas
from pipes on their network. In GS(M)R, the term “gas escapes” includes
escapes or emissions of CO from a gas fitting.
3.3.4.4
GS(M)R places a duty on National Grid Gas (Regulation 7) to:


provide a continuously staffed national 0800 111 999 freephone number for
use by the public, consumer and the emergency services in the event of a
gas escape (gas escapes include actual or suspected emission of CO from
gas appliances, or a fire or explosion where gas is suspected to have been
involved and
contact the relevant GT, or their ESP (where different), immediately when an
emergency arises from a gas escape or suspected emission of CO.
3.3.4.5
There are also duties imposed on gas suppliers, ESPs and GTs to notify the
person who has the responsibility for dealing with the escape should they
receive a report of an escape from the consumer (Regulation 7(3) of GS(M)R).
3.3.4.6
GS(M)R require GTs to investigate gas related fire and explosion incidents
upstream of the consumer’s emergency control valve (ECV) and to send a report
of the investigation to HSE. GTs are also required to investigate fire and
explosion incidents downstream of the consumer’s ECV but this is limited to
establishing whether the seat of the fire or explosion was in an appliance and, if
so, which one, or in installation pipework. The responsibility for investigating CO
poisoning incidents from methane is placed on gas suppliers. HSE must be
notified before such investigations commence. GS(I&U)R place legal duties on
LPG suppliers to deal with escapes of LPG.
3.3.5
Management of Health and Safety at Work Regulations (MHSWR)
MHSWR impose a duty on employers and the self-employed to make
assessments of risks to the health and safety of employees, and non-employees
affected by their work. They also require effective planning and review of
protective measures.
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IGEM/UP/19 – Draft for comment
3.3.6
Personnel Protective Equipment Regulations (PPER)
3.3.6.1
PPER places duties on employers to ensure that work equipment is so
constructed or adapted as to be suitable for the purpose for which it is used or
provided and in selecting work equipment, every employer shall have regard to
the working conditions and to the risks to the health and safety of persons
which exist in the premises or undertaking in which that work equipment is to
be used and any additional risk posed by the use of that work equipment.
3.3.6.2
PPER places duties on employers to take measures to ensure that the exposure
of a person using work equipment to any risk to his health or safety from any
hazard is either prevented, or where that is not reasonably practicable,
adequately controlled, for example intrinsically safe equipment being available
as appropriate.
3.3.7
Provision and Use of Work Equipment Regulations (PUWER)
3.3.7.1
PUWER place duties on employers in relation to selection, suitability,
maintenance, inspection, installation, instruction and training, prevention of
danger and control of equipment.
Note:
More information on PUWER can be found in HSL22. Free leaflets include INDG291 and
INDG229.
3.3.7.2
The term ‘work equipment’ includes all fixed plant and machinery as well as
portable tools for use at work. This includes gas/plant/cable detection
equipment, digging tools, ladders, lifting equipment and hand tools.
3.3.8
Reporting of Injuries, Diseases and Dangerous Occurrences Regulations
(RIDDOR)
3.3.8.1
RIDDOR require employers, self employed people or those in control of work
premises to report certain work related accidents, diseases and dangerous
occurrences.
3.3.8.2
Other people have duties to report certain gas incidents which may not appear
to be work related:


3.3.8.3
death or major injury arising out of the distribution, filling, import or supply
of NG or LPG should be reported by the conveyor for NG and the filler,
importer or supplier for LPG
dangerous gas fittings (as defined in RIDDOR) should be reported by a
"member of a class of persons".
Major injuries, death and dangerous occurrences must be notified immediately,
for example by telephone, to the enforcing authority by the “responsible person”
as defined by RIDDOR. Report can be made to the Incident Contact Centre:

for fatal and major injuries only telephone on 0845 300 9923 (opening hours
Monday to Friday 8.30 am to 5 pm) and complete appropriate on-line form

all other reports at HSE website www.hse.gov.uk
Complete the appropriate online report form listed below. The form will then
be submitted directly to the RIDDOR database. You will receive a copy for
your records.
 report of an injury
 report of a dangerous occurrence
 report of an injury offshore
 report of a dangerous occurrence offshore
7
IGEM/UP/19 – Draft for comment



report of a case of disease
report of flammable gas incident
report of a dangerous gas fitting.
Other reports should be made as soon as practicable and within 10 days of the
incident.
Note:
From 6 April 2012, subject to Parliamentary approval, RIDDOR’s over three day injury
reporting requirement will change. From then the trigger point will increase from over three
days’ to over seven days’ incapacitation (not counting the day on which the accident
happened).
Incapacitation means that the worker is absent or is unable to do work that they would
reasonably be expected to do as part of their normal work.
Employers and others with responsibilities under RIDDOR must still keep a record of all
over three day injuries – if the employer has to keep an accident book, then this record will
be enough.
The deadline by which the over seven day injury must be reported will increase to 15 days
from the day of the accident.
New guidance that explains the change is available to download from the HSE website.
3.3.8.4
HSL73 contains detailed guidance on RIDDOR, including a full list of injuries etc.
that need reporting.
3.3.8.5
IGE/GL/8 provides guidance on the reporting and investigation of gas-related
incidents.
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IGEM/UP/19 – Draft for comment
SECTION 4 : DESIGN AND CONSTRUCTION
4.1
Manufacturers and designers of interlock systems shall take account of the
requirements in Appendix 3. Parts of this Appendix are not intended to apply to
simple systems such as a simple installation of a pressure or gas detector wired
to a safety shut-off valve which are defined as Interlock Systems. It is intended
to apply to Interlock Control Systems such as those within power monitoring,
within pressure proving systems, within chimney pressure/suction controls
systems.
The type of interlock systems available include:
4.2

Power monitoring (a Primary interlock) - systems are available that
measure the absorbed power of the extraction fan(s).

Power monitoring (a Primary interlock) - systems are available that
measure the absorbed power of the extraction fan(s)

Carbon Dioxide monitoring (a Secondary interlock) - systems are
available that measure the levels of carbon dioxide in the environment

Fan power failure (an additional interlock) - where 3-phase power
supplies are used on fan motors, it is practicable to utilise the auxiliary
power supply contact which opens when the fan trips or shuts down for
example under overload conditions

Fire or Gas detection (an additional interlock) - in some locations a fire
or a gas detection system may be employed

Gas Flow monitoring (an additional interlock) – systems are available
that measure the flow rate of gas and to calculate the required air flows for a
safe environment

Gas proving systems – systems that check gas is not leaking before
allowing full flow.

Weep by-pass systems - the system incorporates an automatic isolation
valve (AIV) in the main line and a by-pass line with a small solenoid and
a controlling weep orifice.

Pipework integrity system - the downstream system is pressurised and
then closed off by the weep solenoid valve. The system is then tightness
tested for a time related to the pipe volume

Pressure test system - the downstream system is pressurised and then
closed off by the AIV. The system is then tightness tested for a time
related to the pipe volume.
The quality of the materials, the design and the structure of the components
used shall be such that the system will operate safely for a reasonable period of
time (service life) under the normally expected mechanical, chemical, thermal
and environmental conditions, even in the event of such carelessness as may
occur in normal use, provided that the manufacturer's instructions for
installation, adjustment, operation and maintenance are complied with.
The system shall be designed such that changes in critical circuit component
values such as those affecting timing or sequence within the component
manufacturer’s declared worst case tolerances, including the long term stability,
shall result in the System continuing to function correctly and safely.
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IGEM/UP/19 – Draft for comment
SECTION 5 : APPLICATION OF INTERLOCKS
Failure during operation of an interlock system could lead to major financial losses and a
number of existing systems incorporate a manual over-ride. Such over-rides are not now
permitted since the system could operate in this mode without limit.
Note:
There are failure implications for boiler plant in essential processes such as in refineries and in hospitals and
in major catering systems which will need to be considered when specifying the equipment to be installed.
There are distinct safety differences between interlocks associated with Type A and Type B
appliances, see Clause 1.5. The following guidance introduces the concept of a secondary
interlock that could be used in association with Type A appliances and is actuated upon a
failure condition and this interlock would automatically shut-down after an pre-set period such
as 24 hours.
Interlocks will be used for a variety of ventilation applications. They will also be used in
conjunction with chimney systems such as induced draught flues and fan diluted flues.
CO2 interlock systems are often used to monitor and control general ventilation to spaces such
as classrooms, other teaching areas (see IGEM/UP/11) and catering installations. In some
cases, such interlocks may be seen to be a secondary safety issue and may actuate a visual
alarm for action by responsible persons, such as for general space ventilation.
Rarely do standards cover the retrospective issue of existing installations. They can however
set a basis for consideration of performance upon which a risk assessment should be
developed. It can be argued that any improvements in safety are better than none at all. It
may be unreasonable to expect that an old installation should be brought right up-to-date in
all respects.
5.1
DESCRIPTION OF INTERLOCK SYSTEMS
Primary interlocks shall be applied in conjunction with mechanical ventilation
systems associated with Type B appliance installations where externally flued
equipment is installed.
Secondary interlocks can be applied in conjunction with primary interlocks or
independently for Type A appliance installations.
In each case the interlock shall be required to either prevent gas flowing to
appliances or to prevent their operation. In the latter case, removal of the
power supply is acceptable where such removal stops the appliance operating.
5.1.1
Pressure/Flow (a Primary interlock)
The simplest method of sensing the correct operation of fans is by the use of a
pressure or differential pressure switch. The latter normally being fitted across
the inlet and outlet of the fan. The paddle flow switch is rarely used as it can
become fouled in the ‘dirty’ exhaust products e.g. from cooking processes, it
does however provide a true indication of air flow which the pressure switch
does not unless it operates as an air flow differential device. The sensing devices
shall be able to reliably detect the correct flow conditions and to cause a lockout condition of the system upon failure.
5.1.2
Power monitoring (a Primary interlock)
Systems are available that measure the absorbed power of the fan(s). They can
discriminate between normal power absorption, power absorption if the flow is
low due to high resistances say in the grease filters or low absorption if the
impellor has broken or the drive fan belt has broken. The sensing devices shall
be able to reliably determine the correct flow conditions and to cause a lock-out
condition of the system upon failure.
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IGEM/UP/19 – Draft for comment
5.1.3
Carbon Dioxide monitoring (A Secondary interlock)
The intention of the various codes is to ensure a safe working environment in
applications where combustion products are emitted into the environment such
as catering or food technology (domestic science) laboratories and it can be
argued that environmental monitoring is the true indication of the fan
performance and of the resulting ventilation rates.
For Type B appliance installations, CO2 monitoring is not permitted as the
Primary interlock, but may be used as a Secondary interlock in conjunction with
say pressure interlocks as a back-up system which may be actuated by a
responsible person on site should a major failure of the ventilation system occur
during a period of food service.
This back-up intervention shall be limited within the interlock system to not
more than 24 hours of continuous timer operation. This is to enable remedial
work to be completed after which period, the control system shall proceed to
lock-out. This lock-out condition shall not be possible to be reset by the user for
at least 12 hours.
Actuation of a CO2 alarm condition above 2800 ppm shall cause a visual or
audible warning to occur. Above 5000 ppm, the primary interlock shall cause
lockout of the system to occur.
For Type A appliance installations in small pseudo domestic systems such as a
village hall or B&B it is acceptable to use a CO2 alarm only system. (see
Figure 1)
Note:
5.1.4
Carbon dioxide can be reliably sensed at concentrations well below harmful levels and
therefore can give accurate assessment of ventilation efficiency. The current prescribed
evaluation of extract and supply air efficacy, in this context, advocates measuring CO2
levels with hand held devices. Fixed systems obviously monitor this on a permanent basis.
Fan power failure (an additional interlock)
Where 3-phase power supplies are used on fan motors, it is practicable to utilise
the auxiliary power supply contact which opens when the fan trips or shuts
down for example under overload conditions. This contactor should normally be
wired in series with the power supply to the gas isolation valve (AIV) control
system. This interlock should to be applied in addition to those described above.
5.1.5
Fire or Gas detection (an additional interlock)
In some locations a fire or a gas detection system may be employed. This may
be independent of any other interlock system but could be integrated into a
primary or secondary interlock system if required.
Detection of smoke or fire shall cause shut-down of the system using an
automatic isolation valve. Reset shall be a manual operation.
Gas detection systems will normally have two alarm levels similar to that
described for CO2 systems. Typically at 10% LEL and alarm condition will occur
and at 20% LEL shut-down and lock-out of the system will occur.
5.1.6
Gas Flow monitoring (An additional interlock)
It is possible to measure the flow rate of gas and to calculate the required air
flows for a safe environment. The controller shall then control a variable speed
drive exhaust/supply system to meet demand. This is also considered to be a
demand control system and could be used in conjunction with a Primary
interlock.
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IGEM/UP/19 – Draft for comment
5.2
GAS PROVING SYSTEM OPTIONS
The original weep by-pass proving systems were developed for multi-burner
process plant such as ovens and furnaces which were not fitted with full flame
safeguard systems. They have been widely applied in commercial catering and
schools where a large number of individual appliances and burners operate
without the provision of flame safeguard systems.
The intention was to prevent gas being restored to the downstream system until
it has been proven that all the gas taps on the appliances are in the closed
position. They all relied on a simple pressure switch and originally they were all
manually controlled without in-built timers.
With new technology variants have been produced which require differentiation
between process plant application (UP/12) and commercial applications (e.g.
schools, hospitals, restaurants)
Any of these systems can be applied where Type B appliances without full flame
safeguards are installed with mechanical ventilation systems. They may also be
considered where Type A appliances without full flame safeguards are installed.
They would not normally be required where every appliance has full flame
safeguards fitted.
5.2.1
Weep by-pass systems
The design of weep by-pass systems remains in IGE/UP/12 for process plant.
The system incorporates an automatic isolation valve (AIV) in the main line and
a by-pass line with a small solenoid and a controlling weep orifice. Downstream
of the AIV there is fitted a gas pressure switch. The system will only pass a
small controlled amount of gas through the by-pass and its weep control orifice
such that even if a burner valve is left open, the volume of gas would never
present a hazard. The weep solenoid only remains open for a short time during
which if the valves are closed and the pipework is gas tight, then the rise in gas
pressure will energise the AIV.
5.2.3
Pipework Integrity system
This is similar to the weep by-pass system but operates differently and has less
reliance on the design of the orifice in the weep line. The downstream system is
pressurised and then closed off by the weep solenoid valve. The system is then
tightness tested for a time related to the pipe volume; very similar to an
IGEM/UP/1 test.
This system may be reset immediately following a failed gas test as the release
of gas downstream is controlled through a limiting orifice. Such a system shall
be able to detect a natural gas leak of 0.3 m3 h-1 (0.1 m3 h-1 for LPG). The test
time or purge volume adjustment shall not be readily accessible to the user.
The pressurisation period shall not exceed 10 seconds for systems using a weep
by-pass with a limiting orifice greater than 1 mm diameter.
5.2.4
Pressure Test system
This is similar to the above system but operates differently and has no reliance
on the design of the orifice in the weep line. It does however rely on accurate
opening and closing time of the main AIV. The downstream system is
pressurised and then closed off by the AIV. The system is then tightness tested
for a time related to the pipe volume; very similar to a IGE/UP/1 test. Some
systems use pressure transducers and some measure pressure change across
the AIV.
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IGEM/UP/19 – Draft for comment
After a pressure test failure there shall be a purge delay time of at least 2 mins
before reset can take place Thisshort delay is in order to ventilate any gas that
may have passed into closed combustion spaces such as ovens. The test time or
purge volume adjustment shall not be readily accessible to the user.
Such a system shall be able to detect a natural gas leak of 0.3 m3 h-1 (0.1 m3 h-1
for LPG). The design shall be such that the pressurising safety shut-off valve is
not energised for more than 2 seconds as controlled by a ‘fixed’ timing device of
high reliability. The timing device shall fail safe to zero.
In this system the pressurising safety shut-off valve should not normally need to
be open for more than two seconds but where the time has to be extended for a
specific application, calculations will need to be made to ensure that there is no
excess of gas released to the atmosphere that could create a dangerous
situation.
FIGURE 1 – EXAMPLE OF A WEEP BY-PASS PROVING SYSTEM
FIGURE 2 – EXAMPLE OF A WEEP BY-PASS PROVING SYSTEM
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IGEM/UP/19 – Draft for comment
SECTION 6 : MAINTENANCE AND INSPECTION
In GB – the Gas Safety (Installation and Use) Regulations (GS(I&U)R) Regulation 35 is the
primary legislation concerning the safe installation, maintenance and use of gas systems and
appliances in domestic and commercial installations. Together with duties under the Health
and Safety etc. at Work Act, this requires employers and users to ensure that gas appliances,
flues, pipework and safety devices are maintained in a safe condition to prevent the risk of
injury to any person (see Note).
Note 1: Similar requirements apply in other geographical areas covered by Gas Safe Register. For details of current
gas safety legislation, building legislation and industry standards for the geographical areas covered by Gas
Safe Register, see Technical Bulletin (TB) 999(1) at: https://engineers.gassaferegister.co. - login and visit
the Technical Information area.
Note 2: There are also implications under PUWER for the occupier or employer to ensure that safety systems are
working correctly. The manufacturer of safety and interlock systems will provide information on the
maintenance instructions and procedures for the items of equipment being supplied. It is important to ensure
that such maintenance is performed by competent persons and that any remedial works following
maintenance are actioned with due diligence.
SECTION 7 : USER INSTRUCTIONS
7.1
The installer shall ensure that all user is trained on the use of the interlock
system and the required responses to alarm conditions.
7.2
The installer shall ensure that User Instructions provided with the equipment are
handed to the user. These shall advise the user on the actions to take in the
event of a failed interlock proving system:





a failed ventilation system
a failed pressure test with a valve proving system
a CO2 monitor and alarm system indicating ventilation failure
power failure
gas pressure failure.
SECTION 8 : RECORDS
8.1
Information on all work undertaken on the gas and ventilation systems should
be retained on site by the site occupier.
8.2
These records should include details of all controls systems, maintenance
records, risk assessments and faults/remedial work requirements.
8.3
Where the GIUSP procedures have been applied, details of the faults and
recommendations should be retained in the records.
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IGEM/UP/19 – Draft for comment
SECTION 9 : CATERING INSTALLATIONS
INTRODUCTION
The content of this Section of the Standard is additional to Section 5 to 7 inclusive and has
been developed by the Institution of Gas Engineers and Managers in conjunction with Gas Safe
Register and representatives from the catering industry. Gas Safe Register has issued a
Technical Bulletin TB 140 which replaces HSE guidance note CAIS23 for the catering sector
with regards the necessary advice for installers and designers. A revised version of CAIS23 is
to be issued by HSE for catering businesses.
The aim is to clarify some of the options and requirements for new and existing catering
installations, large and small covered by BS 6173.
The main Standards for reference are BS 6172, BS 6173 and BS 5440-2.
BS 6173 is not intended to apply to dwellings or primarily domestic premises, such as those in
Bed & Breakfast installations for which reference would normally need to be made to
standards such as BS 5440-2 and BS 6172, however some installations may border on
commercial activities due to their high cooking loads.
Small systems also exist in village halls, churches, and country pubs. What really matters is
how often the kitchen is used and what sort of cooking load. The country pub with two
domestic cookers might rely on the microwave for serving hot food with little use on the gas
cooking. Equally it might use two or three domestic cookers flat out if say it is in a holiday
area. A single domestic cooker however can be installed according to BS 5440-2.
It is possible that natural ventilation could achieve adequate safety levels of CO2 in a kitchen
environment, but for small spaces with a large cooker or large catering installations the fitting
of mechanical ventilation would normally be required. This may or may not require extract
canopies but special care will be needed to ensure good air movement within the space to
ensure a safe working environment.
So the application of ventilation, canopies and interlocks of any type to ensure the safety of
staff must use a risk assessment approach as to what is seen as the sensible and safe
solution. It is thus important that all installations other than those in dwellings are required to
have a risk assessment looking at the range of safety issues.
9.1
VENTILATION SYSTEM DESIGN – GENERAL ASPECTS
9.1.1
Reference should be made to Building & Engineering Services Association (B&ES)
(formally the Heating and Ventilation Contractors Association (HVCA)) in their
publication DW 172 ‘Specification for kitchen ventilation systems’ for the design and
installation of catering ventilation systems.
Note:
This information has been developed to safely remove cooking products from a kitchen area
but does not claim to guarantee that the combustion products will be diluted to figures
required in this Standard or indeed in BS 6173. In reality in the great majority of cases it
does however achieve the ventilation rates required.
9.1.2
No advice is given in DW/172 on the sizing of natural ventilation grilles but
Standards such as IGE/UP/10 indicate that the free area of grilles can be
designed using a grille face velocity of 2 m s-1. This means that to dilute the
products of combustion to 2500 ppm CO2 requires approximately 48 m3 per
hour of air per kW of heat input. This equates to approximately 70 cm2 for free
grille open area per kW of heat input. In all cases, the ventilation shall ensure a
safe working environment by limiting the maximum CO2 levels.
9.1.3
Advice is also given on the option of preheating the incoming air supplies which
may, in certain circumstance, be required by the client in cold environments to
overcome cold draughts in the work areas. The use of variable speed fan
15
IGEM/UP/19 – Draft for comment
controls will also reduce such complaints, but where this method is employed,
the minimum operational level of the ventilation systems shall not fall below the
required ventilation rates to ensure safe removal of products of combustion.
Consideration shall be given to ensure that where supply air is provided through
mechanical means, that the correct ratio to extracted air is maintained
throughout the speed controlled process. The supply air can be preheated where
the client requires it, but most systems do not consider such a feature to be
necessary.
9.2
MECHANICAL VENTILATION SYSTEM INTERLOCK REQUIREMENTS
9.2.1
General
9.2.1.1
Interlocks shall be provided to ensure the safety of a system should a
component fail that might then lead to a risk to persons. Failure during
operation of a kitchen in a catering environment could lead to major financial
losses and a number of existing systems incorporate a manual over-ride. Such
over-rides are now considered to be unsatisfactory since the system could
operate in this mode without limit.
9.2.1.2
This Standard introduces the concept of a secondary interlock that could be
actuated upon a failure condition and this interlock would automatically shutdown after a pre-set period such as 24 hours. Manual over-rides of interlocks on
existing systems are no longer considered acceptable and when encountered a
risk assessment should be performed to evaluate the classification to be
adopted in accordance with the current Gas Industry Unsafe Situations
Procedure (see Figure 3).
9.2.1.3
Manual over-rides of interlocks on new systems are no longer considered
acceptable and reference should be made to BS 6173 and Figure 3.
9.2.1.4
A small domestic type installation, for example in a village hall or B & B, that is
used infrequently and only for short periods could have opening windows or a
domestic type wall extract fan. Interlocks would be unnecessary but safe
systems of works shall be in place and suitable signage should be used
identifying the ventilation procedures.
Note:
Notices typically would be expected to say ‘When cooking, ensure adequate ventilation by
opening windows or operating extractor fans’.
9.2.1.5
For the intermediate pseudo-domestic installations, for example not more than
two domestic gas cookers, where for example a small guest house providing a
wider range of meals then there is more need to ensure the safety of the
environment during the design stage but the design of the installation makes it
difficult to apply interlocks. Power monitoring or CO2 environmental monitoring
should be applied, either providing an alarm as a minimum or shut-down if
practicable. This recognizes that valve proving systems may be too expensive to
apply for small operations.
9.2.2
Types of Interlock
Interlocks are divided into primary and secondary types.
Primary interlocks


Pressure/Flow
Power monitoring.
Secondary interlocks


Gas Flow monitoring
Carbon Dioxide monitoring.
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IGEM/UP/19 – Draft for comment
Additional interlock


Fan power failure
Gas flow monitoring.
A full description of these interlocks and the requirements for their use is given
in Sub-Section 5.1
9.2.3
Valve proving systems
If a valve proving system is required (see Sub-Section 5.3), it may be
acceptable in very small installations to have manual operation of the isolating
valve to an area. In this case, staff shall be trained in the procedures and be
able to recognise the dangers and safety warning signage shall be provided. It
shall be the responsibility of the chef or site management for safe operation of
the valve.
9.2.4
Air flow proving systems
Where reasonably practical and cost acceptable, a Primary air proving interlock
such as the pressure interlock system should be applied as a minimum as it is
probably the least expensive to apply. Where a Primary interlock is not
practicable for example where there are a number of wall mounted extract fans,
a Secondary interlock should be applied. Where even this is not practicable such
as on small installations, a simple 2-stage CO2 audible alarm system might be
seen to be a minimum as a means of controlling the environment to safe levels.
9.3
COOKER CANOPIES
9.3.1
Ventilation shall be provided as required in BS 6173 and where this is achieved
with mechanical systems, canopies and exhaust systems should be designed in
accordance with DW/172.
Note 1: Such a system may not be practical or acceptable on cost grounds for existing smaller
domestic type cooking installations.
Note 2: It is always preferred on new installations to install canopies over the cooking appliances.
9.3.2
Whatever system is installed, during commissioning, a check shall be made for
the CO2 level in the atmosphere at 2 m above floor level in the centre of the
cooking work area(s) and at the outside edge of any canopy. Where the levels
exceed 2800 ppm, additional ventilation shall be required.
9.4
ASSESSING THE EFFECTIVENESS OF VENTILATION PROVISION OR
SYSTEMS
Assessing the effectiveness of existing ventilation provision for a catering
establishment has always been difficult, and guidance has previously been
provided in the 2004 and 2007 editions of CAIS23 and currently in BS 6173 and
BS 7967-5.
9.4.1
The test to measure the levels of CO2 in the atmosphere shall be taken at 2 m
above floor level in the centre of the cooking work area(s) and at the outside
edge of any canopy.
9.5
TEST EQUIPMENT FOR MEASURING CO2
To carry out environmental testing direct reading CO2 analysers that meet the
minimum requirements of the product standard BS 8494 shall be used.
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IGEM/UP/19 – Draft for comment
9.6
TESTING
9.6.1
Tests shall be performed with appliances and burners operating under maximum
cooking load conditions.
9.6.2
After the environment has settled (not less than 10 minutes) the concentrations
of CO2 at the sample positions should not exceed 2800 ppm.
9.6.3
Where it is found that the concentration of CO2 exceeds that given above, the
person performing the test should advise the responsible person for the
installation that they shall consider improving ventilation or turning off /isolating
non-essential gas cooking equipment. It may also be necessary to ventilate the
affected area by opening windows and doors as necessary until the
concentrations of CO2 are reduced below 2800 ppm.
9.6.4
Where an atmosphere sampling test identifies that continued use of the catering
establishment would be considered unsafe, the current Gas Industry Unsafe
Situations Procedure (GIUSP) shall be implemented (see TB 140 Figure 1
Flowchart dealing with assessment protocol when dealing with gas-fired
commercial catering appliances) and the necessary actions taken to make the
installation safe.
Note:
This decision can only be made following close liaison with the responsible person for the
catering establishment and may involve the isolation of some appliances to achieve
acceptable environmental conditions rather than shutting down the kitchen.
9.7
EXISTING SYSTEMS
9.7.1
Monitoring for levels of CO2 in the atmosphere shall be performed as above (see
Sub-Sections 9.4, 9.5 and 9.6).
9.7.2
Where an atmosphere sampling test identifies that continued use of the catering
establishment would be considered unsafe, the current Gas Industry Unsafe
Situations Procedure (GIUSP) shall be implemented (see Figure 3)
Note:
Rarely do standards cover the retrospective issue of existing installations. They can,
however, set a basis for consideration of performance upon which a risk assessment may
be developed.
It can be argued that any improvements in safety are better than none at all. It may be
unreasonable to expect that an old installation ought to be brought right up-to-date in all
respects. Where a major refurbishment of the installation takes place, then it would be
reasonable to consider the installation as a new installation as far as is reasonably
practicable.
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IGEM/UP/19 – Draft for comment
FIGURE 3 - FLOWCHART DEALING WITH ASSESSMENT PROTOCOL WHEN
DEALING
WITH
GAS-FIRED
COMMERCIAL
CATERING
APPLIANCES TAKEN FROM GAS SAFE REGISTER’S TB 140
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IGEM/UP/19 – Draft for comment
APPENDIX 1 :
GLOSSARY, ACRONYMS, ABBREVIATIONS, SYMBOLS
AND UNITS
GLOSSARY
primary interlock
Component which monitors prescribed operating conditions and
ensures appropriate action if conditions deviate from the normal
operating level
Note:
secondary interlock
A primary component that will prevent the appliance operation by cutting its
power supply
Component which monitors prescribed operating conditions and
ensures appropriate action if conditions deviate from the normal
operating level
Note:
A secondary component that will prevent the appliance operation by cutting its
power supply.
All other definitions are given in IGEM/G/4 which is freely available by downloading a printable
version from IGEM’s website www.igem.org.uk.
Standard and legacy gas metering arrangements are given in IGEM/G/1 which is freely
available by downloading a printable version from IGEM’s website.
ACRONYMS AND ABBREVIATIONS
AC
ACoP
AIV
AR
B&ES
CAIS
CB
CoP
COSHH
DC
DECT
DSEAR
ECV
ESP
EWR
GB
GIUSP
GS(M)R
GS(I&U)R
GT
HSE
HSWA
HVCA
ID
IGEM
I/O
IP
ISM
alternating current
Approved Code of Practice
automatic isolation valve
At Risk
Building and Engineering Services Association (formally HVCA)
catering information sheet (provided by HSE)
citizen band
Code of Practice
Control of Substances Hazardous to Health Regulations
direct current
digital European cordless telephone
Dangerous Substances and Explosive Atmospheres Regulations
emergency control valve
emergency service provider
Electricity at Work Regulations
Great Britain
Gas Industry Unsafe Situations Procedure
Gas Safety (Management) Regulations
Gas Safety (Installation and Use) Regulations
gas transporter
Health and Safety Executive
Health and Safety at Work etc. Act
Heating and Ventilation Contractors Association
Immediately Dangerous
Institution of Gas Engineers and Managers
input/output
ingress protection
industrial, scientific and medical radio-frequency equipment
20
IGEM/UP/19 – Draft for comment
LEL
LPG
MHSWR
NG
PE
PPE
PPER
PUWER
RIDDOR
SSOV
TB
UK
lower flammability limit
Liquefied Petroleum Gas
Management of Health and Safety at Work Regulations
Natural Gas
polyethylene
personal protective equipment
Personal Protective Equipment Regulations
Provision and Use of Work Equipment Regulations
Reporting of Injuries, Diseases and Dangerous Occurrences Regulations
Safety shut-off valve
technical bulletin (by Gas Safe Register)
United Kingdom.
UNITS
bar
V m-1
V
kV
kW
Hz
kHz
MHz
m
s
min
mbar
m3
cm2
m3 h-1
m s-1
dB
°C
K
ppm
bar
Volt per meter
Volt
kilovolt
kilowatt
Hertz
kilohertz
megahertz
metre
second
minute
millibar
cubic metre
square centimetre
cubic metre per hour
metre per second
decibel
degree Centigrade
Kelvin
part per million.
SYMBOLS
CO
CO2
%
carbon monoxide
carbon dioxide
percentage.
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IGEM/UP/19 – Draft for comment
APPENDIX 2 – REFERENCES
This Standard is set out against a background of legislation in force in GB at the time of
publication. Similar considerations are likely to apply in other countries and reference to the
appropriate national legislation will be necessary. The following list is not exhaustive.
All relevant legislation must be complied with and relevant Approved Codes of Practice
(ACoPs), official Guidance Notes and referenced codes, standards, etc. shall be taken into
account.
Where British Standards, etc. are quoted, equivalent national or international standards, etc.
equally may be appropriate.
Care shall be taken to ensure that the latest editions of the relevant documents are used.
A2.1
A2.2
LEGISLATION














Building Regulations (England and Wales) 2000 as Amended



Noise at Work Regulations 1989
Building (Scotland) Regulations 2000 and Amendments
Building Regulations (Northern Ireland) 2000 and Amendment
Confined Spaces Regulations 1997
Control of Substances Hazardous to Health Regulations 2002
Dangerous Substances and Explosive Atmospheres Regulations 2002
Electricity at Work Regulations 1989
Gas Act 1986 (as amended by the Gas Act 1995)
Gas Appliances (Safety) Regulations 1995
Gas Cooking Appliances (Safety) Regulations 1989
Gas Safety (Installation and Use) Regulations 1998
Health and Safety at Work etc. Act 1974
Heating Appliances (Fireguard) Regulations 1991
Management of Health and Safety at Work Regulations 1999 as amended
2006
Provision and Use of Work Equipment Regulations 1998
Reporting of Injuries, Diseases and Dangerous Occurrences Regulations
1995.
HSE ACOPS AND GUIDANCE




CAIS 10
Ventilation of kitchens in catering establishments
CAIS 23
Gas safety in catering and hospitality
HSG48
Human factors in industrial safety. Guidance
HSG65
Successful
Guidance

HSL21


Management of health and safety at Work. ACoP
and Guidance
HSL22
Safe use of work equipment. ACoP and Guidance
HSL56
Safety in the installation and use of gas systems
and appliances. ACoP and Guidance

HSL73
Reporting of Injuries, Diseases and Dangerous
Occurrences Regulations. Guidance
22
health
and
safety
management.
IGEM/UP/19 – Draft for comment
A2.3
A2.4



HSL80
Gas Safety (Management) Regulations. Guidance
HSR25
Electricity at Work Regulations. Guidance
INDG291

Simple guide to the Provision and Use of Work
Equipment Regulations
INDG229
Using work equipment safely.
IGEM

IGE/UP/1
Edition 2 RWA
Strength and tightness testing and direct purging of
industrial and commercial gas installations

IGE/UP/1A
Edition 2 RWA
Strength and tightness testing and direct purging of
small low pressure industrial and commercial Natural
Gas installations

IGEM/UP/1B
Edition 3
Tightness testing and direct purging of small Natural
Gas installations

IGEM/UP/1C
Strength testing, tightness testing and direct purging
of NG and LPG meter installations

IGEM/UP/2
Edition 2
Installation pipework on industrial and commercial
premises

IGE/UP/3
Edition 2
Gas fuelled spark ignition and dual fuel engines

IGEM/UP/4
Edition 3
Commissioning of gas fired plant on industrial and
commercial premises

IGEM/UP/6
Edition 2
Application of compressors to Natural Gas fuel
systems

IGE/UP/10
Edition 3
Gas appliances in industrial and commercial premises

IGEM/UP/11
Edition 2
Gas installations in educational establishments

IGE/UP/12
Application of burners and controls to gas fired
process plant

IGEM/UP/16
Design for NG installations on industrial and
commercial premises with respect to hazardous area
classification and preparation of risk assessments

IGE/G/1
Defining the end of the Network, a meter installation
and installation pipework

IGE/GL/8
Edition 2
Reporting and investigation of gas related incidents

IGEM/SR/29
Dealing with gas escapes.
BRITISH STANDARDS INSTITUTION (abbreviated titles)

BS 5440-2

Flueing and ventilation for gas appliances of rated
input not exceeding 70 kW net (1st, 2nd and 3rd
family gases)
BS 5482

Domestic
butane
installations
BS 5588
Fire precautions for buildings
23
and
propane
gas
burning
IGEM/UP/19 – Draft for comment
A2.5



BS 5885
Automatic gas burners
BS 6129
Bellows expansion joints
BS 6172
Specification for installation, servicing and
maintenance of domestic gas cooking appliances (2nd
and 3rd family gases)

BS 6173
Specification for installation and maintenance of gasfired catering appliances for use in all types of
catering establishments (2nd and 3rd family gases)



BS 6400
Domestic-sized meter installations
BS 6501
Metallic hose assemblies
BS 6644
Specification for the installation and maintenance of
gas-fired hot water boilers of rated inputs between 70
kW (net) and 1.8 MW (net) (2nd and 3rd family
gases)





BS 6891
Low pressure gas pipework (domestic premises)
BS 7461
Automatic gas shut off valves
BS 7671
IEE wiring regulations
BS 7838
CSST pipe and fittings
BS 7967-5
Carbon monoxide in dwellings and other premises
and the combustion performance of gas-fired
appliances

BS 8494
Electronic portable and transportable apparatus
designed to detect and measure carbon dioxide in
indoor ambient air




BS EN 161
Automatic shut off valves
BS EN 1775
Gas pipework in buildings
BS EN 10497
Testing of valves. Fire type-testing requirements
BS EN 50073
Apparatus for the detection and measurement of
combustible gases

BS EN 50379-3


Specification for portable electrical apparatus
designed to measure combustion flue gas parameters
of heating appliances
BS EN 60079
Electrical apparatus for explosive gas atmospheres
BS EN 61779
Electrical
apparatus
for
the
detection
measurement of combustible gases.
and
MISCELLANEOUS (abbreviated titles)

TB 140


Guidance on ventilation and extract requirements for
commercial catering installations by Gas Safe
Register
TB 999
Gas Safe Register Normative Document List
DW/172
Specification for kitchen ventilation systems by the
Building & Engineering Services Association (B&ES)
(formally the Heating and Ventilation Contractors
Association (HVCA)).
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APPENDIX 3 – SPECIFICATION AND TESTING OF CONTROL SYSTEMS
Parts of this Appendix are not intended to apply to simple systems such as a pressure or gas
detector wired to a safety shut-off valve which are defined as Interlock Systems. It is intended
to apply to Interlock Control Systems such as those within power monitoring, within pressure
proving systems, within chimney pressure/suction controls systems.
A3.1
GENERAL
Any tests shall be carried out under normal conditions unless otherwise
specified. The normal conditions are:



rated voltage or rated voltage range
rated frequency
ambient temperature of (20  5)C.
The error of measurement shall not exceed:




for time measurements  0.1 s
for temperature measurements  1K
for supply frequency measurements  0.1 Hz
for electrical supply measurements  0.5%.
All measurements shall be made after stable temperature conditions have been
achieved.
Tests shall be carried out in the mounting positions specified by the
manufacturer. When several mounting positions are specified, the tests shall be
carried out with the system installed in the least favourable position.
A3.2
GENERAL CONSTRUCTION REQUIREMENTS
The quality of the materials, the design and the structure of the components
used shall be such that the system will operate safely for a reasonable period of
time (service life) under the normally expected mechanical, chemical, thermal
and environmental conditions, even in the event of such carelessness as may
occur in normal use, provided that the manufacturer's instructions for
installation, adjustment, operation and maintenance are complied with.
The system shall be designed such that changes in critical circuit component
values such as those affecting timing or sequence within the component
manufacturer’s declared worst case tolerances, including the long term stability,
shall result in the System continuing to function correctly and safely.
Compliance shall be checked by worst case analysis.
The construction of any additional functions included in the system for which no
provisions exist in this Standard shall be such that they do not degrade the safe
and correct operation of the system.
A3.3
COMPONENTS
The devices used in systems are normally items such as pressure switches,
pressure transducers, safety shut-off valves, manual valves and electronic
components.
The safety of such systems relies to a major extent on compliance with relevant
standards and in some cases with testing to a manufacturing specification.
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Some of the applicable Standards are:





pressure switches for gas
BS EN 1854
pressure transducers
BS EN 1854
safety shut-off valves
BS EN 161
manual valves
BS EN 331
electrical and electronic components
EN 60730-1.
Where standards already exist for System components, the requirements
specified in these standards will have priority for these components. Valves (for
example for pressurizing and relieving the test section) integrated into the
functional sequence shall satisfy the requirements of EN 161 Class A and
pressure sensing devices of EN 1854.
The gas system shall be capable of withstanding a minimum pressure of
100 mbar.
A3.4
HOUSING
Parts of the housing that directly or indirectly separate a gas-carrying
compartment from the atmosphere shall be manufactured only of metallic
materials.
A3.5
SWITCHING CYCLES
Mechanical and electro-mechanical components and contacts which are
actuated at every switch-on operation or only when a shut-down occurs due to
a disturbance shall satisfy the number of switching cycles specified in 5.11 of
EN 1643. Relays shall, as a minimum, meet the requirements of according to
EN 298 Annex A including note 7 and 8.
A3.6
SWITCHING CONTACTS
Appropriate measures (for example over-current protection devices) shall be
used to protect switching contacts against the effects of short circuits. Where
these measures are external, the manufacturer shall provide installation
instructions.
A3.7
SIGNAL FOR INDICATION
A signal for indication for example optical indication shall be given when the
leakage detected by a valve proving system exceeds the detection limit.
A3.8
SETTING
The setting of an interlock shall require the use of tools or otherwise be
protected against unauthorised adjustment. If the Interlock System is
adjustable the manufacturer shall supply information for its setting for example
detection setting.
Adjustment of safety critical timing shall only be by means of tools or accessible
by tools or secured by passwords in programmable systems.
The response time to achieve shut-down and lock-out following failure of an
interlock shall not exceed 2 seconds.
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A3.9
PROTECTION PROVIDED BY THE ENCLOSURE
The class of protection for systems with their own enclosure shall be a
minimum of EN 60529 IP 40 when installed in accordance with the
manufacturer’s instructions. For systems for use in the open air the protection
shall conform to at least EN 60529 IP 54 when installed in accordance with the
manufacturer's instructions.
A3.10
ELECTRICAL EQUIPMENT
The electrical equipment shall comply with the relevant requirements of
EN 60730-1; Clauses 8, 9, 10, 11, 12, 13, 14, 18, 19, 20, 21, 22, 23 and 24. If
the supply voltage polarity can affect the safety, either provisions to avoid
uncontrolled opening of a gas valve shall be provided or clear warnings shall be
given in the installation and operating instructions.
Any program sequence including safety relevant timings shall be in accordance
with the manufacturer’s specifications at:


AC voltages between 85% of the minimum and 110% of the maximum rated
voltage
DC voltages between 80% of the minimum and 120% of the maximum rated
voltage when tested at ambient temperatures between 0 and 60C.
Outside these ranges the interlock device shall either continue to operate safely
or fail to safety.
Interruption of the mains supply and its restoration shall not affect the safety of
the System or its program sequence.
The Interlock Control System shall be designed so that a re-start attempt
following any shut-down or lock-out condition shall only be possible following a
manual reset with an integrally or remotely mounted reset button.
Interlock Control Systems incorporating a clock/timer circuitry which is
synchronized with or compared to the supply frequency, shall be designed so
that in the event of variations in that frequency the timings do not vary by  5%
of the specified figure. Outside this figure, the Interlock Control Systems shall
be prevented from being reset but may continue in operation.
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A3.11
ELECTRICAL SURGE IMMUNITY TESTS
A3.11.1
General
The Interlock Control System shall tolerate voltage surges on the mains supply
and relevant signal terminals, so that when tested in accordance with A311.2 for
the values of Table 1, assessment criterion a) it shall continue to function
correctly and safely. It shall neither proceed to shut-down or lock-out nor shall it
reset from lock-out.
Assessment
criteria
Severity
level
a)
b)
2
3
DC inputs and
DC outputs
power ports
Ports for process
measurement and
control lines
(sensors and
actuators)
Mains
Mains
line to
line
lines
to
earth
line
to
line
lines
to
earth
line to
line
lines
to
earth
0.5 kV
1 kV
1.0 kV
2.0 kV
0.5
kV
0.5 KV
0.5 kV
0.5 kV
1.0 kV
TABLE 1 – OPEN CIRCUIT TEST VOLTAGE  0% FOR AC MAINS
SYSTEMS
A3.11.2
Surge immunity
The Interlock Control System shall be tested in accordance with EN 61000-4-5.
The tests shall be carried out by subjecting the system to five pulses and with
the voltage and current values listed in Table 1a) and b) at intervals not less
than 60 s.
The five pulses of each polarity () and each phase angle as described in
EN 61000-4-5 are delivered in the following order:



2 pulses with the system in the lock-out position
1 pulse with the system in stand-by position (if applicable)
2 pulses randomly applied during the Interlock timed sequence.
The tests on interface cables are not carried out if the manufacturer explicitly
specifies that the length of that cable shall not exceed 10 m or 20 m if it is a
screened cable.
A3.11.3
Transient bursts
The system shall tolerate electrical fast transient/bursts on the mains supply
and signal lines so that when tested in accordance with A3.11.4:


for the values of Table 2, assessment criterion a) it shall continue to function
correctly and safely. It shall neither go to shut-down or lock-out, nor shall it
reset from lock-out
for the values of Table 2, assessment criterion b) either it shall perform as in
a) or it may proceed to shut-down followed by lock-out. A defect of the
system is not allowed.
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L1.L2. PE
L1.L2. PE
I/O
I/O
Severity
level
Voltage
peak
kV
Repetition
rate
kHz
Voltage
peak
kV
Repetition
rate
kHz
a)
2
1
5
0.5
5
b)
3
2
5
1
5
Assessment
criteria
TABLE 2 – OPEN CIRCUIT OUTPUT TEST VOLTAGES  10% AND
REPETITION RATE OF THE IMPULSES  20%
A3.11.4
Electrical fast transient/burst test
The Interlock Control System shall be tested in accordance with EN 61000-4-4.
The test shall be performed for 20 cycles during the Interlock Control System
sequence. The test shall also be performed for a minimum of 2 min with the
system in the lock-out position.
The test on the interface cables are not carried out if the manufacturer explicitly
specifies that the length of the cable must not exceed 3 m or 20 m if it is a
screened cable.
A3.12
IMMUNITY TO CONDUCTED DISTURBANCES, INDUCED BY RADIOFREQUENCY FIELDS
Note:
A3.12.1
The following tests may not be required if the selected components and system design can
be shown to be immune from such interference that might lead to incorrect or unsafe
operation.
General
The Interlock Control System shall tolerate conducted disturbances, induced by
radio frequency fields on the main supply and relevant control lines so that
when tested in accordance with A3.12.2:


for the values of Table 3, assessment criterion a) it shall continue to function
correctly and safely. It shall neither go to shut-down or lock-out, nor shall it
reset from lock-out.
for the values of Table 3, assessment criterion b) either it shall perform as in
a) or it may proceed to shut-down followed by lock-out. Any detect of the
system is not allowed.
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Frequency range
150 kHz – 80 MHz
Assessment
Severity
Voltage level (emf) U0 [V]
150 kHz
ISM and CB
a)
2
3
6
b)
3
10
20
The levels in the ISM, CB bands are chosen to be 6 dB higher.
ISM: Industrial, scientific and medical radio frequency equipment 13.56 
0.007 MHz. 40.68 : 0.02 MHz
CB: Citizen Band: 27.125  1.5 MHz
TABLE 3 – TEST VOLTAGES FOR CONDUCTED IMMUNITY ON MAINS AND
I/O LINES
Note:
The industrial, scientific and medical (ISM) radio bands are radio bands which are reserved
internationally for the use of radio frequency (RF) energy for various purposes other than
communications. The powerful emissions from many pieces of equipment can create electromagnetic
interference thereby disrupting radio communications using the same frequency,. In general,
communications equipment operating in these bands must tolerate any interference generated by ISM
equipment, and users have no regulatory protection from ISM device operation.
The tests on interface cables are not carried out if the manufacturer explicitly
specifies that the length of that cable shall not exceed 1 m or the cables are
screened.
A3.12.2
Immunity to conducted disturbances, induced by radio-frequency fields,
test
The Interlock Control System shall be tested in accordance with EN 61000-4-6.
The Interlock Control System is swept through the complete frequency range at
least once with the system in each of the following positions:



stand-by position (if applicable)
Interlock Control System sequence position
lock-out position.
Note:
During sweeping through the frequency range the dwell time at each frequency to be not
less than the time necessary for the Interlock Control System to be exercised and be able
to respond. Sensitive frequencies or the frequencies of dominant interest may be analysed
separately.
A3.12.3
Radiated, radio frequency, electromagnetic field immunity test
A3.12.3.1
General
The Interlock Control System shall tolerate radiated electromagnetic fields so
that when tested in accordance with A3.12.3.2:


for the values of Table 4 assessment criterion a) it shall continue to function
correctly and safely. It shall neither go to shut-down or lock-out, nor shall it
reset from lock-out.
for the values of Table 4 assessment criterion b) either it shall perform as in
a) or it may proceed to shut-down followed by lock-out. Any defect of the
system is not allowed.
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Frequency range
80 MHz – 1000 MHz and 1890 MHz
Assessment
criteria
Severity level
a)
2
3
6
b)
3
10
20
Test field strength (V/mJ)
80 MHz-ISM, GSM-1000 MHz and DECT
bands
The levels in the ISM. CB. GSM and DECT bands are chosen to be 6 dB higher.
ISM: Industrial, scientific and medical radio-frequency equipment 433.92  1%
pulses of equal mark/space ratio (2.5 ms on and 2.5 ms off)
DECT: Digital European Cordless Telephone: 1890:t 10 MHI. modulated by 200
Hz ~ 1% pulses at equal mark/space ratio (2.5 ms on and 2.5 ms off).
TABLE 4 – TEST LEVELS FOR RADIATED IMMUNITY
A3.12.3.2
Radiated radio-frequency, electromagnetic field immunity, test
The system shall be tested in accordance with EN 61000-4-3.
The Interlock Control System has to be swept through the complete frequency
range at least once with the system in each of the following positions:



stand-by position (if applicable)
Interlock Control System sequence position
lock-out position.
Note:
During sweeping through the frequency range the dwell time at each frequency to be not
less than the time necessary for the Interlock Control System to be exercised and be able
to respond. Sensitive frequencies or the frequencies of dominant interest may be analysed
separately.
A3.12.4
Electrostatic discharge immunity test
A3.12.4.1
General
The Interlock Control System shall tolerate electrostatic discharges so that when
tested in accordance with A3.12.4.2:

for the values of Table 5 assessment criterion a) it shall continue to function
correctly and safely. It shall neither go to shut-down or lock-out nor shall it
reset from lock-out.

for the values of Table 5 assessment criterion b) either it shall perform as in
a) or it may proceed to shut-down followed by lock-out. Any defect of the
system is not allowed.
This requirement is applied only to units having their own protective enclosure.
Assessment
criteria
Severity level
Contact discharge
Air discharge
a)
2
4 kV
4 kV
b)
3
6 kV
8 kV
TABLE 5 – TEST VOLTAGES FOR DIRECT AND INDIRECT ELECTROSTATIC
DISCHARGES
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IGEM/UP/19 – Draft for comment
A3.13
Marking, installation and operating instructions
A3.13.1
Marking
The System and/or its components shall be durably marked in a clear and
visible position with the following:
A3.13.2



name of manufacturer and/or registered trademark




degree of protection (IP rating)
nature of supply and frequency
maximum pressure in mbar/bar
Note: this may be the Strength Test Pressure (see IGEM UP/1) and shall not
be less than 100 mbar
rated voltage range
maximum load rating of outputs
date of manufacture (at least the year), which may be in code.
Installation and operating instructions
Instructions shall include all relevant information on use, testing, installation,
operation and maintenance, in particular:





type reference




information on how to reset the system
electrical data including maximum ratings of loads on output terminals
maximum and minimum permissible ambient temperature
maximum gas strength test pressures (STP see IGE/UP/1)
wiring diagram with clear terminal markings for the connection of the mains
and/or battery supply and external wiring
permissible installation position
Information on dealing with fault indication and alarm conditions
information on dealing with faults.
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33