Standard
ISA-12.12.01-2007
Nonincendive Electrical
Equipment for Use in
Class I and II, Division 2
and Class III, Divisions 1
and 2 Hazardous
(Classified) Locations
Draft 4
March 2007
ISA-12.12.01-2007
Nonincendive Electrical Equipment for Use in Class I and II, Division 2 and Class III, Divisions 1
and 2 Hazardous (Classified) Locations
ISBN:
Copyright  2007 by ISA. All rights reserved. Not for resale. Printed in the United States of
America. No part of this publication may be reproduced, stored in a retrieval system, or
transmitted, in any form or by any means (electronic, mechanical, photocopying, recording, or
otherwise), without the prior written permission of the Publisher.
ISA
67 Alexander Drive
P. O. Box 12277
Research Triangle Park, North Carolina 27709
-3-
ISA-12.12.01-2007
Preface
This preface, as well as all footnotes and annexes, is included for information purposes and is not
part of ISA-12.12.01-2007.
This Standard has been prepared as part of the service of ISA toward a goal of uniformity in the
field of instrumentation. To be of real value, this document should not be static but should be
subject to periodic review. Toward this end, the Society welcomes all comments and criticisms
and asks that they be addressed to the Secretary, Standards and Practices Board; ISA; 67
Alexander Drive; P. O. Box 12277; Research Triangle Park, NC 27709; Telephone (919) 5498411; Fax (919) 549-8288; E-mail: standards@isa.org.
The ISA Standards and Practices Department is aware of the growing need for attention to the
metric system of units in general, and the International System of Units (SI) in particular, in the
preparation of instrumentation standards. The Department is further aware of the benefits to USA
users of ISA standards of incorporating suitable references to the SI (and the metric system) in
their business and professional dealings with other countries. Toward this end, this Department
will endeavor to introduce SI-acceptable metric units in all new and revised standards,
recommended practices, and technical reports to the greatest extent possible. Standard for Use
of the International System of Units (SI): The Modern Metric System, published by the American
Society for Testing & Materials as IEEE/ASTM SI 10-97, and future revisions, will be the reference
guide for definitions, symbols, abbreviations, and conversion factors.
It is the policy of ISA to encourage and welcome the participation of all concerned individuals and
interests in the development of ISA standards, recommended practices, and technical reports.
Participation in the ISA standards-making process by an individual in no way constitutes
endorsement by the employer of that individual, of ISA, or of any of the standards, recommended
practices, and technical reports that ISA develops.
The following people served as members of ISA Subcommittee SP12.12:
NAME
COMPANY
R. Masek, Chair
M. Coppler*, Managing Director
N. Abbatiello
R. Allen
S. Arnold*
A. Ballard
W. Bennett
D. Bishop
H. Bockle
K. Boegli
J. Bossert
E. Briesch
R. Cardinal
J. Dolphin
A. Engler
W. Fiske
G. Garcha
P. Hamer
D. Hohenstein
G. Kozinski
CSA International
Ametek Inc.
Optimation Technology
Honeywell Inc.
Ametek Drexelbrook
Crouse Hinds Division of Cooper Industries
Mine Safety Appliances Company
David N. Bishop Consultant
R. Stahl Inc.
Phoenix Contact Inc.
Hazloc Inc.
Underwriters Laboratories Inc.
Bentley Nevada LLC
PSC Solutions
Det Norske Veritas DNV
Intertek Testing Services
GE Energy
Chevron Texaco Corp. Research & Tech. Co.
Pepperl+Fuchs Inc.
GE Infrastructure Sensing
ISA-12.12.01-2007
J. Kuczka
C. Kurtzman
B. Larson
E. Legenski
N. Ludlam
E. Massey
J. Miller
O. Murphy
C. Oudar
D. Pace
J. Propst
V. Salupo
A. Stafford
D. Wechsler
R. Wigg
-4Killark
Rosemount Inc.
Turck Inc.
The WorleyParsons Group
FM Approvals
Rockwell Automation
Detector Electronics Corporation
Brooks Instrument
ExLoc Corporation
Olin Corporation
Equilon Enterprises
Eli Lilly & Company
Consultant
Dow Chemical Company
E-x Solutions International Pty. Ltd.
The following people served as members of ISA Committee SP12:
NAME
COMPANY
T. Schnaare, Chair
W. Lawrence, Vice Chair
M. Coppler, Managing Director
D. Ankele
A. Ballard
D. Bishop
H. Bockle
K. Boegli
D. Burns
R. Cardinal
C. Casso
S. Czaniecki
J. Dolphin
T. Dubaniewicz
A. Engler
W. Fiske
G. Garcha
D. Hohenstein
D. Jagger
F. Kent
P. Kovscek
J. Kuczka
B. Larson
R. Masek*
E. Massey
A. Mobley
S. Nguyen
A. Page
P. Schimmoeller*
R. Seitz
D. Wechsler
R. Wigg
______
* One vote per company.
Rosemount Inc.
FM Approvals
Ametek Inc.
Underwriters Laboratories Inc.
Crouse Hinds Division of Cooper Industries
David N Bishop Consultant
R. Stahl Inc.
Phoenix Contact Inc.
Shell Exploration & Production Company
Bently Nevada LLC
Nabors Industries
Intrinsic Safety Concepts Inc.
PSC Solutions
NIOSH
Det Norske Veritas DNV
Intertek Testing Services
GE Energy
Pepperl+Fuchs Inc.
Bifold-Fluid Power
Honeywell Inc.
Industrial Scientific Corp.
Killark
Turck Inc.
CSA International
Rockwell Automation
3M Company
Siemens Milltronics Ltd.
MSHA Approval & Certification Centre
CSA International
Artech Engineering
Dow Chemical Company
E-x Solutions International Pty. Ltd.
-5-
ISA-12.12.01-2007
This standard was approved for publication by the ISA Standards and Practices Board on
________________.
NAME
COMPANY
T. McAvinew, Vice President
M. Coppler
B. Dumortier
D. Dunn
W. Holland
E. Icayan
J. Jamison
K. Lindner
V. Maggioli
A. McCauley
G. McFarland
R. Reimer
N. Sands
H. Sasajima
T. Schnaare
J. Tatera
I. Verhappen
R. Webb
W. Weidman
J. Weiss
M. Widmeyer
M. Zielinski
Jacobs Engineering Group
Ametek Inc.
Schneider Electric
Aramco Services Company
Consultant
ACES Inc.
Husky Energy Inc.
Endress+Hauser Process Solutions AG
Feltronics Corporation
Chagrin Valley Controls Inc.
Emerson Process Mgmt Power & Water Solutions
Rockwell Automation
E I du Pont
Yamatake Corporation
Rosemount Inc.
Tatera & Associates Inc.
MTL Instrument Group
Robert C Webb PE
Worley Parsons
Applied Control Solutions LLC
Consultant
Emerson Process Management
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ISA-12.12.01-2007
Contents
1
Purpose ........................................................................................................................... 9
2
Scope .............................................................................................................................. 9
3
Definitions ...................................................................................................................... 10
4
General requirements ..................................................................................................... 13
5
Requirements for Class I, Division 2 equipment .............................................................. 14
6
Requirements for Class II, Division 2, Class III, Divisions 1 and 2 equipment .................. 14
7
Nonincendive circuits and nonincendive field wiring ........................................................ 15
8
Normally nonarcing components ..................................................................................... 25
9
Marking .......................................................................................................................... 26
10 Surface temperature requirements.................................................................................. 28
11 Evaluation of nonincendive circuits ................................................................................. 30
12 Evaluation of nonincendive components ......................................................................... 33
13 Evaluation of sealed device ............................................................................................ 34
14 Evaluation of enclosures for Class II and III .................................................................... 35
15 Drop tests and impact tests ............................................................................................ 37
16 Manufacturer's instructional manual................................................................................ 38
Annex A — Normative references ......................................................................................... 41
Annex B — Common standards – safety requirements for electrical equipment
(informative) ................................................................................................................... 43
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1
ISA-12.12.01-2007
Purpose
The purpose of this standard is to provide minimum requirements for the design, construction, and
marking of electrical equipment or parts of such equipment for use in Class I and Class II,
Division 2 and Class III, Divisions 1 and 2 hazardous (classified) locations. This equipment, in
normal operation, is not capable of causing ignition of the surrounding atmosphere under the
conditions prescribed in this standard, although the equipment may contain electronic components
that operate at incendive levels and may also have field wiring that is incendive. In addition, it is
the intent of this document to establish uniformity in test methods for determining the suitability of
the equipment and associated circuits and components as they relate to potential ignition of a
specific flammable gas or vapour-in-air mixture, combustible dust, easily ignitible fibers, or flyings.
2
2.1
Scope
This standard applies only to equipment, circuits, and components designed specifically for
use in Class I and II, Division 2 and Class III, Divisions 1 and 2 hazardous (classified)
®
locations as defined in the National Electrical Code  (NEC ) ANSI/NFPA 70.
NOTE Some equipment designed for use in unclassified locations is permitted by the NEC ® for
installing in Division 2 locations. The judgment of acceptability for the installation would be determined
by the authority having jurisdiction. Such equipment would not have the hazardous location marking or
documentation described in this standard. It is anticipated that such equipment would comply with the
other requirements in this standard and that the determination of compliance is elementary (e.g., a
nonarcing instrument inside a NEMA Type 4 or 12 enclosure used in a Class II, Division 2 location).
2.2
This standard also applies to certain unclassified location equipment specifically designed
to directly connect to nonincendive field wiring in Class I and II, Division 2 and Class III,
®
Divisions 1 and 2 hazardous (classified) locations as defined in the NEC .
2.3
This standard is primarily intended to provide requirements for electrical and electronic test,
measuring, and controlling equipment.
2.4
This standard is concerned only with equipment construction and test criteria related to
electrical or thermal ignition of specified flammable gases, vapors, combustible dusts,
fibers, and flyings in air.
2.5
This standard is not intended to cover equipment for use in Class I and Class II, Division 1
locations, such as equipment constructed to be intrinsically safe, dust ignition-proof, or
explosion-proof. Such equipment is, however, suitable for use in Class I and Class II,
Division 2 locations in the same group and temperature class for which it is suitable in
Division 1.
2.6
This standard does not cover mechanisms of ignition from external sources, such as static
electricity or lightning, that are not related to the electrical characteristics of the equipment.
2.7
This standard is not intended as an instructional manual for untrained persons. It is
intended to promote uniformity of practice among those skilled in the area of design,
construction, and application of equipment suitable for Class I and Class II, Division 2 and
Class III, Divisions 1 and 2 locations.
2.8
The requirements of this standard are based on consideration of ignition in locations made
hazardous by the presence of flammable gases, vapors, combustible dusts, fibers, and
flyings under the following ambient conditions:
a)
an ambient temperature of -25°C to 40°C
b)
an oxygen concentration of not greater than 21 percent by volume
ISA-12.12.01-2007
c)
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a pressure of 80 kPa (0.8 bar) to 110 kPa (1.1 bar)
NOTE If equipment is specified to operate in conditions outside the ranges listed above, the requirements of
this standard may not ensure the desired level of safety.
2.9
This standard covers portable battery-powered equipment other than flashlights and
lanterns for Class I and Class II, Division 2, and Class III, Divisions 1 and 2 hazardous
(classified) locations.
2.10
This standard does not cover electric luminaires for use in Division 2 hazardous (classified)
locations.
2.11
This standard does not cover electric motors, electric heaters, heat tracing cables, and
similar heat-producing devices, except where they are an integral part of the equipment
under evaluation, for use in Division 2 locations.
2.12
This standard does not cover AEx requirements for equipment for use in Class I, Zone 2
hazardous (classified) locations.
2.13
This standard does not cover the requirements for equipment for use in Zone 20, Zone 21
or Zone 22.
3
Definitions
For the purposes of this standard, the following definitions apply.
3.1
associated nonincendive field wiring apparatus
apparatus in which the circuits are not necessarily nonincendive themselves, but that affect the
energy in nonincendive field wiring circuits and are relied upon to maintain nonincendive energy
levels. Associated nonincendive field wiring apparatus may be either of the following:
a) Electrical apparatus that has an alternative type of protection for use in the appropriate
hazardous (classified) location
b) Electrical apparatus not so protected that shall not be used in a hazardous (classified) location
NOTE — Associated nonincendive field wiring apparatus has designated associated nonincendive field wiring
apparatus connections for nonincendive field wiring apparatus and may also have connections for other electrical
apparatus.
3.2
control drawing
a drawing or other document provided by the manufacturer of the nonincendive field wiring
apparatus or the associated nonincendive field wiring apparatus that details the allowed
interconnections with other circuits or equipment. The control drawing includes the applicable
electrical parameters to permit selection of equipment for interconnection.
3.3
dust-tight
enclosures constructed so that dust will not enter under specified test conditions.
3.4
hermetically sealed device
a device that is sealed against the entrance of an external atmosphere and in which the seal is
made by fusion; e.g., soldering, brazing, welding, or the fusion of glass to metal.
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ISA-12.12.01-2007
3.5
maintenance, corrective
any maintenance activity that is not normal in the operation of the equipment and requires access
to the equipment's interior. Such activities are expected to be performed by qualified personnel
who are aware of the hazards involved. Such activities typically include locating causes of faulty
performance, replacing defective components, and adjusting service controls.
3.6
maintenance, operational
any maintenance activity, excluding corrective maintenance, that is intended to be performed by
the operator and is required for the equipment to serve its intended purpose. Such operational
maintenance activities typically include the correcting of "zero" on a panel instrument, changing
charts, keeping of records, and adding ink.
3.7
make/break components
components having contacts that can interrupt a circuit (even if the interruption is transient in
nature). Examples of make/break components are relays, circuit breakers, servo potentiometers,
adjustable resistors, switches, and connectors.
3.8
maximum external capacitance (C a )
maximum value of capacitance in a circuit that can be connected to the connection facilities of the
associated nonincendive field wiring apparatus.
3.9
maximum external inductance (L a )
maximum value of inductance in a circuit that can be connected to the connection facilities of the
associated nonincendive field wiring apparatus.
3.10
maximum external inductance to resistance ratio (L a /R a )
ratio of inductance (L a ) to resistance (R a ) of any external circuit that can be connected to the
connection facilities of the associated nonincendive field wiring apparatus.
3.11
maximum input power (P i )
maximum power in an external circuit that can be applied to the connection facilities of the
nonincendive field wiring apparatus.
3.12
maximum input voltage (V max )
maximum voltage (peak a.c. or d.c.) that can be applied to the connection facilities of the
nonincendive field wiring apparatus.
3.13
maximum internal capacitance (C i )
total equivalent internal capacitance which is considered as appearing across the connection
facilities of the nonincendive field wiring apparatus.
ISA-12.12.01-2007
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3.14
maximum internal inductance (L i )
total equivalent internal inductance which is considered as appearing at the connection facilities of
the nonincendive field wiring apparatus.
3.15
maximum internal inductance to resistance ratio (L i /R i )
ratio of inductance (L i ) to resistance (R i ) that is considered as appearing at the connection
facilities of the nonincendive field wiring apparatus.
3.16
maximum output current (I sc )
maximum output current (peak a.c. or d.c.) in a circuit that can be taken from the connection
facilities of the associated nonincendive field wiring apparatus under normal operation.
3.17
maximum output voltage (V oc )
maximum output voltage (peak a.c. or d.c.) in a circuit that can appear under open-circuit
conditions at the connection facilities of the associated nonincendive field wiring apparatus under
normal operation.
3.18
maximum output power (P o )
maximum electrical power in a circuit that can be taken from the connection facilities of the
associated nonincendive field wiring apparatus under normal operation.
3.19
nonincendive circuit
a circuit, other than nonincendive field wiring, in which any arc or thermal effect produced under
normal operating conditions, is not capable of igniting the flammable gas-, vapor-, dust-air mixture,
fibers or flyings. The circuit is evaluated under prescribed test conditions.
3.20
nonincendive component
a component having contacts for making or breaking an incendive circuit and the contacting
mechanism is constructed so that the component, under normal operating conditions, is not capable
of igniting the flammable gas or vapor-air mixture. The housing of a nonincendive component is
not intended to exclude the flammable atmosphere or contain an explosion. The component is
evaluated under prescribed test conditions.
3.21
nonincendive equipment
equipment having electrical/electronic circuitry that is not capable, under normal operating
conditions, of causing ignition of a specified flammable gas-, vapor-, dust-air mixture fibers or
flyings due to arcing or thermal means.
3.22
nonincendive field wiring
wiring that enters or leaves an equipment enclosure and, under normal operating conditions of the
equipment, is not capable, due to arcing or thermal effects, of igniting the flammable gas-, vapor-,
dust- air mixture, fibers or flyings. Normal operation includes opening, shorting, or grounding the
field wiring.
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ISA-12.12.01-2007
3.23
nonincendive field wiring apparatus
nonincendive equipment intended to be connected to nonincendive field wiring.
3.24
normal operating conditions
conditions under which equipment conforms electrically and mechanically with its design
specification and is used within the conditions specified by the manufacturer. These conditions
include
a) supply voltage, current, and frequency;
b) environmental conditions (including process interface);
c) all tool-removable parts (e.g., covers) in place;
d) all operator-accessible adjustments at their most unfavorable settings; and
e) opening or grounding of any one or shorting of any two of the nonincendive field-wiring
conductors.
3.25
operator-accessible
readily accessible to the operator during normal use without use of a tool.
3.26
sealed device
a device so constructed that it cannot be opened during normal operational conditions or
operational maintenance; it is sealed to restrict entry of an external atmosphere.
3.27
unclassified locations
locations that have been evaluated by the classification process defined in ANSI/NFPA 70: and
determined to be not Class I, Division 1; Class I, Division 2; Class I, Zone 0; Class I, Zone 1;
Class I, Zone 2; Class II, Division 1; Class II, Division 2; Class III, Division 1; Class III, Division 2;
Zone 20; Zone 21; Zone 22; or any combination thereof.
3.28
maximum input current (I max )
maximum current (peak a.c. or d.c.) that can be applied to the connection facilities of the
nonincendive field wiring apparatus.
3.29
incendive circuit
a circuit, in which any arc or thermal effect produced under normal operating conditions, is
capable of igniting the flammable gas-, vapor-, dust-air mixture, fibers or flyings.
4
General requirements
Requirements for equipment intended to be used in Class I and Class II, Division 2 and Class III,
Divisions 1 and 2 hazardous (classified) locations are established on the basis that the equipment
in its normal operating condition is not capable of causing ignition of a specified flammable gas,
vapor-in-air mixture, dust, fibers, or flyings. The tolerances associated with the components of the
equipment shall be considered. Subsequent arcs or thermal effects within the equipment, resulting
from opening, shorting, or grounding of nonincendive field wiring, shall be taken into consideration
ISA-12.12.01-2007
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as they affect the suitability of the equipment for use in Division 2 locations. Equipment also shall
comply with the unclassified location requirements for the particular category of equipment except
as specifically amended herein (see Annex B).
5
Requirements for Class I, Division 2 equipment
Protection shall be provided according to 5.1.1 and 5.1.2 to ensure that under normal
operating conditions such equipment is not capable of igniting the specified flammable gas
or vapor-in-air mixture.
5.1
5.1.1
Each make/break component shall be either
a) a normally nonarcing component that meets the requirements of Clause 8;
b) used in a nonincendive circuit that meets the requirements of Clause 7;
c) a nonincendive component that meets the requirements of Clause 12; or
d) a sealed device that meets the requirements of Clause 13.
5.1.2
5.2
Equipment shall comply with the thermal ignition requirements of Clause 10.
Enclosures shall provide a suitable degree of protection against deterioration of the
equipment that would adversely affect its suitability for use in Class I, Division 2 locations.
NOTE Although general-purpose enclosures normally will suffice, particular attention should be given to the possible
need for weatherproofing, general protection from corrosion (for further information see ANSI/UL 50 or ANSI/NEMA
250, Enclosures for Electrical Equipment) and to preventive maintenance .
5.3
Fuses used in circuits that are subject to overloading in normal use shall be of a type
suitable for use in Division 2 locations or housed in an enclosure suitable for Division 1
locations.
NOTE This subclause precludes a fuse housed in a general-purpose enclosure from being used in a motor circuit
where a possibility of a stalled motor opening the fuse exists, or where there is the possibility of an overload not caused
by a fault in the circuit.
5.4
If a replaceable fuse is provided, a switch suitable for the location where it is installed shall
also be provided to remove power from the fuse. The switch need not be integral to the
equipment if the equipment installation instructions indicate the need for such a switch.
5.5
A circuit breaker that may be used as a switch shall be of a type suitable for use in
Division 2 locations or alternatively protected for use in Division 1 locations.
6
6.1
Requirements for Class II, Division 2, Class III, Divisions 1 and 2 equipment
For Class II, Division 2 equipment, protection shall be provided by the use of an enclosure
that meets the requirements of Clause 13 or 14 or shall be a nonincendive circuit meeting
the requirements of Clause 7, with consideration for possible ignition in accordance with 7.2
due to the ingress of dust or by a combination of these methods. For Class III locations,
protection shall be provided by a dust-tight enclosure that meets the requirements of
Clause 14.
Consideration shall be given to shorting or bypassing components by Class II Group E or
Class II Group F dusts.
EXCEPTION: Portable battery-powered equipment marked for use in Class II Group G or Class III
only need not have all electrical components and wiring enclosed provided both the following
conditions are met:
a) Entrance or accumulation of dust does not result in ignition or charring of the dust
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ISA-12.12.01-2007
b) Circuits with make/break components shall be determined to be nonincendive with a propaneair mixture in accordance with the spark-ignition test (see 11.1 through 11.5, or 7.1).
7
7.1
Nonincendive circuits and nonincendive field wiring
Either of the following two methods may be employed to determine that a circuit(s) or field
wiring is nonincendive:
a) Testing the circuit according to Clause 11
b) Comparing the maximum calculated or measured values of current, voltage, and associated
inductances and capacitances to the appropriate values in Figures 1 through 8 to establish
that the current and voltage levels are below those specified in 7.3; for Class II and III
locations the curves for propane are to be used.
7.2
When evaluating a circuit as nonincendive, the following ignition sources shall be
considered:
a) Discharge of capacitive circuits
b) Interruption of inductive circuits
c) Intermittent making and breaking of resistive circuits
d) opening or grounding of any one or shorting of any two of the nonincendive field-wiring
conductors
7.3
The maximum voltage and current levels (d.c. or a.c. peak) in circuits determined to be
nonincendive by the comparison method, for given circuit constants, shall be less than
a) the current from Figures 1 through 6; and
b) the voltage from Figures 7 and 8.
The maximum normal output voltage and the maximum short-circuit current shall be determined
under the worst-case normal operation.
NOTE Figures 1 and 2 apply only to circuits whose output voltage/current characteristic is a straight line drawn
between open-circuit voltage and short-circuit current.
Circuits with nonlinear outputs are subject to special
investigation.
7.4
For evaluating associated nonincendive field wiring apparatus, use the maximum output
voltage (V oc ), and maximum output current (I sc ) with the applicable ignition Figures 1 to 8 to
determine the maximum external capacitance (C a ) and maximum external inductance (L a ).
7.5
For evaluating nonincendive field wiring apparatus, determine the maximum internal
capacitance (C i ) and maximum internal inductance (L i ). These parameters shall be below
the limits shown in Figures 1 to 8 based on the maximum input voltage (V max) and the
maximum input current (I max) of the nonincendive field wiring apparatus.
7.6
For nonincendive field wiring circuit evaluations the maximum input voltage (V max) of the
nonincendive field wiring apparatus shall be equal to or greater than the maximum output
voltage (V oc ) of the associated nonincendive field wiring apparatus. Additionally, the
maximum input current (I max) of the nonincendive field wiring apparatus shall be equal to or
greater than the maximum output current (I sc ) of the associated nonincendive field wiring
apparatus.
EXCEPTION: For nonincendive field wiring apparatus that controls its own operating current, the
maximum input current (I max) of the nonincendive field wiring apparatus need not correspond to
the maximum output current (I sc ) of the associated nonincendive field wiring apparatus (e.g.,
4-20 mA measurement and control devices). Likewise, the maximum input voltage (V max) of
ISA-12.12.01-2007
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nonincendive field wiring apparatus that controls its own
greater than the maximum output voltage (V oc ) of the
apparatus (e.g., current to pressure valve controllers that
Details of the permitted connections shall be provided on a
7.7
normal operating voltage need not be
associated nonincendive field wiring
are voltage clamped at the terminals).
control drawing.
Nonincendive field wiring enables interconnection of nonincendive field wiring apparatus
with associated nonincendive field wiring apparatus not specifically examined in
combination as a system when one of the following conditions is true:
a) Normal operating voltage or current not controlled by the nonincendive field wiring apparatus
V max ≥ V oc ; I max ≥ I sc ; C a ≥ C i + C cable ; L a ≥ L i + L cable
b) Normal operating current controlled by the nonincendive field wiring apparatus (I max of the
nonincendive field wiring apparatus need not be greater than the I sc of the associated
nonincendive field wiring apparatus)
V max ≥ V oc ; C a ≥ C i + C cable ; L a ≥ L i + L cable
c) Normal operating voltage controlled by the nonincendive field wiring apparatus (V max of the
nonincendive field wiring apparatus need not be greater than the V oc of the associated
nonincendive field wiring apparatus)
I max ≥ I sc ; C a ≥ C i + C cable ; L a ≥ L i + L cable
d) Normal operating current and voltage controlled by the nonincendive field wiring apparatus
(neither I max nor V max of the nonincendive field wiring apparatus need be greater than the
corresponding parameter of the associated nonincendive field wiring apparatus)
C a ≥ C i + C cable ; L a ≥ L i + L cable
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Figure 1 — Resistance circuits (L≤
≤ 5 µH)
ISA-12.12.01-2007
ISA-12.12.01-2007
- 18 -
Figure 2 — Resistance circuits (L≤
≤ 5 µH)
- 19 -
Figure 3 — Inductance circuits
ISA-12.12.01-2007
ISA-12.12.01-2007
- 20 -
Figure 4 — Inductance circuits
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Figure 5 — Inductance circuits
ISA-12.12.01-2007
ISA-12.12.01-2007
- 22 -
Figure 6 — Inductance circuits
- 23 -
Figure 7 — Capacitance circuits
ISA-12.12.01-2007
ISA-12.12.01-2007
- 24 -
Figure 8 — Capacitance circuits
- 25 -
8
ISA-12.12.01-2007
Normally nonarcing components
8.1
Make/break components that are to be considered nonarcing in normal operation shall
comply with the requirements of 8.2 through 8.7, as applicable.
8.2
Connectors and plug-in components used in incendive circuits and incorporated within
equipment shall be considered normally nonarcing if disconnection is not required under
operational conditions and if they require a separating force of at least 15 N. If accessible
during normal operating conditions, connectors in an incendive circuit shall be provided with
a warning marking in accordance with 9.2.
EXCEPTION: Plug-in components need only pass a pull test of 3 times the mass of the
component.
8.3
In incendive circuits, fuses that are removable during normal operating conditions shall be
removable only with the use of a tool and require a separating force of at least 15 N. The
fuseholders for such fuses shall be provided with a warning marking in accordance with 9.2
and located adjacent to the fuseholder.
EXCEPTION: Plug-in type fuses need only pass a pull test of 3 times the mass of the component.
8.4
Circuit breakers that cannot be manually switched off, i.e., have only a reset button, may be
used in circuits that are not subject to overloading in normal use. All such circuit breakers
shall be provided with a warning marking in accordance with 9.3 and located adjacent to the
circuit breaker.
8.5
In incendive circuits, removable lamps that are accessible during normal operating
conditions shall be removable only with the use of a tool. The lamp holders for such lamps
shall be provided with a warning marking in accordance with 9.2 and located adjacent to the
lampholder. The lamp shall be protected to prevent breakage of the bulb.
EXCEPTION: A tool need not be required to remove the lamp if the lamp is accessible only after
removal of a separate protective cover. The cover need not require a tool to remove.
8.6
If accessible during normal operating conditions, connectors used for nonincendive field
wiring shall not be interchangeable with other field wiring connectors.
EXCEPTION: Where interchange does not affect nonincendive circuits or where connectors are
so identified that interchange is unlikely, interchangeable connectors are allowed.
8.7
If accessible only by the use of a tool, manually operated make/break components in an
incendive circuit are considered normally nonarcing components.
NOTE Circuit breakers may be used in circuits that are not subject to overloading in normal use.
ISA-12.12.01-2007
9
- 26 -
Marking
9.1
In addition to the marking required for general-purpose equipment, the equipment shall be
marked with the following minimum information:
9.1.1
For equipment to be installed in a hazardous location, the hazardous location suitability:
Class, Division, and Group(s). In lieu of Group(s), a specific gas, vapor, or dust, fiber, or
flying. Apparatus that attains temperatures higher than 100°C based on a 40°C ambient
or a higher marked ambient shall be marked either by the temperature code as given in
Table 3, or by the specific temperature as measured according to 10.
9.1.2
For associated nonincendive field wiring apparatus, a statement that the equipment
provides nonincendive field wiring outputs and the hazardous location suitability of the
output: Class, Division, and Group(s). In lieu of Group(s), a specific gas, vapor, dust,
fiber, or flying
9.1.3
Any other markings or cautions necessary for the installation and safe operation of the
equipment
The international symbol
equipment instructions.
9.2
may be used to refer the operator to an explanation in the
Connectors, fuseholders, and lampholders required to be marked according to 8.2, 8.3, and
8.5 shall be marked with the following or an equivalent warning:
WARNING: DO NOT REMOVE OR REPLACE WHILE CIRCUIT IS LIVE UNLESS THE AREA IS
KNOWN TO BE FREE OF IGNITIBLE CONCENTRATIONS OF FLAMMABLE SUBSTANCES.
If practical, this marking shall be either on or adjacent to the component. Otherwise, this marking
shall be displayed on a prominent place on the enclosure.
9.3
Circuit breakers, required to be marked according to 8.4, shall be marked with the following
or an equivalent warning:
WARNING: DO NOT RESET CIRCUIT BREAKER UNLESS POWER HAS BEEN REMOVED
FROM THE EQUIPMENT OR THE AREA IS KNOWN TO BE FREE OF IGNITIBLE
CONCENTRATIONS OF FLAMMABLE SUBSTANCES.
9.4
The following information shall either be marked on the equipment or contained in the
Control drawing for equipment with nonincendive field wiring connections:
9.4.1
Connections for nonincendive field wiring shall be clearly identified
9.4.2
Associated nonincendive field wiring apparatus
a) V oc
b) I sc
c) C a
d) L a
e) P o - (optional)
NOTE In addition to the above, parameter L a /R a may also be marked.
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ISA-12.12.01-2007
Nonincendive field wiring apparatus
9.4.3
Normal operating voltage or current not controlled by the nonincendive field wiring
apparatus
9.4.3.1
a) V max
b) I max
c) C i
d) L i
e) P i - (optional)
Normal operating current controlled by the nonincendive field wiring apparatus
9.4.3.2
a) Vmax
b) Ci
c) Li
d) Pi (optional)
Normal operating voltage controlled by the nonincendive field wiring apparatus
9.4.3.3
a) Imax
b) Ci
c) Li
d) Pi (optional)
9.4.3.4
Normal operating current and voltage controlled by the nonincendive field wiring
apparatus
a) Ci
b) Li
c) Pi (optional)
EXCEPTION: Equipment supplied, as a system, including cables supplied for field wiring, need
only comply with 9.4.1.
NOTE 1 In addition to the above, parameter L i /R i may also be marked,.
NOTE 2 Ordinary locations standards such as ANSI/ISA-61010-1 require the marking of the rated values of the supply
voltages or rated range of the supply voltages, and either;
a)
the maximum rated power in either watts or volt-amperes or
b)
the maximum rated input current.
9.4.4
9.5
The control drawing reference shall be marked on the associated nonincendive field
wiring apparatus and on the nonincendive field wiring apparatus.
In addition, equipment may be marked Class I, Zone 2 Group IIA (or IIB, or IIC as
applicable) and the operating temperature or temperature class. The temperature class
shall be in accordance with 10.2. The correlation between Groups for Zones and Groups for
Divisions are shown below.
Where the electrical equipment is suitable for use in a particular gas, the chemical formula or
name of the gas shall follow the symbol II.
ISA-12.12.01-2007
Class I Division 2 Groups
- 28 Class I Zone 2 Groups
A
B
C
D
IIC
(IIB + H 2 )
IIB
IIA
NOTE (IIB +H 2 ) is not a Group as defined by the NEC ® .
9.6
For practical reasons the symbols used for voltage, current capacitance, inductance, and
L/R ratio may be replaced by the symbols defined in ANSI/ISA-60079-0, Electrical
Apparatus for Use in Class I, Zones 0, 1, & 2 Hazardous (Classified) Locations – General
Requirements. A comparison is shown in the following table. Division and zone parameters
should not be mixed.
Table 1 — Nonincendive field wiring apparatus parameters
Electrical Parameter
Associated Nonincendive Field Wiring Apparatus
Maximum output voltage
Maximum output current
Maximum output power
Maximum external capacitance
Maximum external inductance
Maximum external inductance to resistance ratio
Nonincendive Field Wiring Apparatus
Maximum input voltage
Maximum input current
Maximum internal capacitance
Maximum internal inductance
Maximum input power
Maximum internal inductance to resistance ratio
Division
parameters
Zone
parameters
V oc
I sc
Po
Ca
La
L a /R a
Uo
Io
Po
Co
Lo
L o /R o
V max
I max
Ci
Li
Pi
L i /R i
Ui
Ii
Ci
Li
Pi
L i /R i
10 Surface temperature requirements
10.1
Determination of maximum surface temperature
The maximum temperature of any surface that may come in contact with a flammable gas or
vapor-in-air mixture, dust, fibers, or flyings shall be determined under normal operational
conditions. Such measurements need not be made on the internal parts of sealed devices.
Measurements shall be made at any convenient ambient temperature, corrected linearly to 40°C
or higher marked ambient.
Maximum surface temperature shall be determined for rated duty of the electrical equipment but
with the most unfavorable supply voltage between 90% and 110% of the rated voltage of the
electrical equipment, unless other applicable standards prescribe wider tolerances.
NOTE More than one temperature class may be established for different ambient temperatures.
- 29 10.2
ISA-12.12.01-2007
Surface temperature
The maximum surface temperature obtained during testing shall be used to determine the
applicable temperature class. The maximum surface temperature may be exceeded for small
components meeting the requirements of 10.3.
10.3
Small components
Small components, for example transistors or resistors, whose temperature exceeds that
permitted for the temperature classification, shall be acceptable providing that they conform to
one of the following.
a) When tested in accordance with Clause 26.5.3 of ANSI/ISA-60079-0, small components shall
not cause ignition of the flammable mixture and any deformation or deterioration caused by
the higher temperature shall not impair the type of protection; or
b) For T4 classification, small components shall conform to Table 2; or
c) For T5 classification, the surface temperature of a component with a surface area smaller than
1 000 mm 2 (excluding lead wires) shall not exceed 150 °C.
Table 2 – Assessment for T4 classification according to component size
and ambient temperature
Total surface area excluding wire
terminations
< 20 mm 2
≥ 20 mm
Surface temperature ≤ 275 °C
2
2
≥ 20 mm ≤ 1 000 mm
Requirement for T4 classification
Power dissipation ≤ 1,3 W*
2
Surface temperature ≤ 200 °C
* Reduced to 1,2 W with 60 °C ambient temperature or 1,0 W with 80 °C ambient temperature.
For potentiometers, the surface to be considered shall be that of the resistance element and not
the external surface of the component. The mounting arrangement and the heat-sinking and
cooling effect of the overall potentiometer construction shall be taken into consideration during the
test. Temperature shall be measured on the track with that current which flows under the test
conditions required by this standard. If this results in a resistance value of less than 10 % of the
track resistance value, the measurements shall be carried out at 10 % of the track resistance
value.
The surface temperature of components having a total surface area of not more than 1 000 mm 2
may exceed the temperature class marked on the electrical equipment, if they are not ignition
capable with a safety margin of:
•
50 K for T1, T2 and T3;
•
25 K for T4, T5 and T6.
This safety margin shall be ensured by tests of the electrical equipment.
NOTE
During the tests, the safety margin may be provided by increasing the ambient temperature.
ISA-12.12.01-2007
- 30 -
Table 3 — Temperature classifications (T codes)
Degrees °C
Temperature Code
450
300
280
260
230
215
200
180
165
160
135
120
100
85
T1
T2
T2A
T2B
T2C
T2D
T3
T3A
T3B
T3C
T4
T4A
T5
T6
11 Evaluation of nonincendive circuits
11.1
The spark test apparatus used for performing ignition tests on circuits shall consist of an
3
explosion chamber at least 250 cm in volume, in which circuit-making and circuit-breaking
sparks can be produced in the presence of the prescribed test gas.
11.2
Components of the contact arrangement are a cadmium disc with 2 slots and 4 tungsten
wires of 0,2 mm diameter, which slide over the disc. The free length of the tungsten wires
shall be 11 mm. The driving spindle, to which the tungsten wires are attached, shall make
80 revolutions per minute. The spindle on which the cadmium disc is mounted shall revolve
in the opposite direction. The ratio of the speeds of the driving spindle to the disc spindle
shall be 50 to 12. The spindles shall be insulated from one another and from the housing.
See Figure 9. The explosion chamber shall be able to withstand pressures of 1 470 kPa or
shall be provided with suitable pressure relief. When cadmium, zinc, or magnesium will not
be present, the cadmium disc may be replaced by a tin disc.
11.3
Gas mixture
11.3.1
For Group D, the test mixture shall be 5,25 ± 0,25 percent propane by volume in air.
11.3.2
For Group C, the test mixture shall be 7,8 ± 0,5 percent ethylene by volume in air.
11.3.3
For Groups A and B, the test mixture shall be 21 ± 2 percent hydrogen by volume in air.
11.3.4
For Classes II and III, the test mixture shall be 5,25 ± 0,25 percent propane by volume in
air.
11.3.5
Apparatus that is intended for use in a specific gas or vapor-in-air may be tested in the
most easily ignitable concentration of that gas or vapor-in-air mixture in lieu of the
mixtures specified in 11.3.1 through 11.3.4.
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ISA-12.12.01-2007
Figure 9 — Test apparatus for evaluating nonincendive circuits
ISA-12.12.01-2007
11.4
- 32 -
Sensitivity verification of spark test apparatus
11.4.1
The sensitivity of the spark test apparatus shall be verified before and after each test
series conducted in accordance with 11.4.2. The test apparatus shall be operated in
a 24 V d.c. circuit containing a 95 mH air-core coil. The currents in these circuits shall
be set at the corresponding value given for the appropriate group in Tables 4 or 5, as
applicable.
11.4.2
Verification of the apparatus shall be satisfactory if ignition of the gas occurs within 400
revolutions of the tungsten wire holder.
Table 4 — Current in verification circuit - cadmium disk
Group
Inductive Circuit
D
C
A&B
100 mA
65 mA
30 mA
Table 5 — Current in verification circuit - tin disk
11.5
Group
Inductive Circuit
D
C
A&B
110 mA
90 mA
50 mA
Tests
11.5.1
The spark test apparatus shall be connected in the circuit under test at each point where
a spark can normally occur, taking into account the requirements of this standard.
11.5.2
Ignition test conditions
There shall be no ignition of the test mixture under any of the following conditions:
a) For line-connected apparatus, the input voltage shall be increased to 110 percent of nominal
line voltage.
b) All adjustments shall be set at their most unfavorable positions.
c) All circuits shall be tested for the following number of revolutions of the tungsten wire holder in
the spark test apparatus:
1) For d.c. circuits, not less than 400 revolutions - 200 revolutions at each polarity
2) For a.c. circuits, not less than 1000 revolutions
- 33 -
ISA-12.12.01-2007
The test apparatus shall be verified according to 11.4 after each ignition test. The ignition
test shall be considered invalid if the verification test is unsatisfactory.
11.5.3
12 Evaluation of nonincendive components
12.1
Nonincendive components shall be subjected to the tests specified in 12.2.
12.1.1
A nonincendive component is limited in use to the rating for which it has been
satisfactorily tested according to 12.2.
12.1.2
Nonincendive components shall be preconditioned by being operated a minimum of 6 000
times at the rate of approximately 6 times per minute while carrying their normal
electrical load.
12.2
Spark ignition test for nonincendive components
12.2.1
Following the preconditioning test, the nonincendive component shall be placed in a
suitable test chamber of at least ten (10) times the volume of the device and connected
to an electrical load of 150 percent of the a.c. or d.c. current (maximum 75 percent power
factor if for a.c.) and at maximum voltage of the circuit for which the component is being
tested.
EXCEPTION: The 75 percent power factor requirement may be neglected for totally resistive loads
only.
12.2.1.1
12.2.2
Components intended for use with high inrush current loads (e.g., motor or tungsten
lamp loads) shall be subjected to overload testing that is representative of actual
circuit applications. Preconditioning and overload conditions shall be according to the
requirements of national standards that cover these applications.
Nonincendive components shall be filled with and surrounded by a gas mixture according
to 11.3.1 through 11.3.5. The samples should be prepared by using one of the methods
in 12.2.2.1 to 12.2.2.3 and then successfully withstand the test in 12.2.3.
12.2.2.1
Remove the housing adjacent to the contacts to permit free access of the air-gas
mixture to the contacts.
12.2.2.2
Drill at least two holes in the enclosure that will assure propagation of an ignition from
the inside to the outside of the enclosure. The test gas shall flow through the device.
A tube may be connected to one of the holes for this purpose.
12.2.2.3
Draw a vacuum within the chamber and maintain the vacuum for 100 seconds. Fill the
test chamber with the specified air-gas mixture and maintain the concentration for 100
seconds before applying the required electrical load. An explosion detection device
(e.g., a pressure transducer) shall be connected to the device under test to detect
ignition.
12.2.3
The component shall be operated a minimum of 50 times at not less than 10-second
intervals, renewing the air-gas mixture after each set of 10 operations (or more
frequently, if necessary to ensure the presence of the air-gas mixture within the
nonincendive component). There shall be no ignition of the air-gas mixture.
ISA-12.12.01-2007
- 34 -
13 Evaluation of sealed device
13.1
13.1.1
This subclause covers the requirements for electrical equipment or parts of electrical
equipment or components that contain normally arcing parts or heat-producing surfaces
that, by their location in a sealed enclosure, are intended to be made incapable of causing
ignition of the specified gas or vapor-in-air mixtures at their most easily ignitable
concentration.
Hermetically sealed devices (see definition in Clause 3) shall be considered to meet
these requirements without test.
13.2
Except as permitted in 13.1.1, the free internal volume of the device shall be less than
3
100 cm .
13.3
Resilient gasket seals or poured seals shall be arranged so that they are not subject to
mechanical damage during normal operational conditions and shall retain their sealing
properties for the intended conditions of use.
13.3.1
Sealing and encapsulating material shall have softening or melting points at least 20K
higher than the maximum temperature of the material achieved during the tests specified
in this standard.
13.4
A sealed device shall have structural integrity and shall be constructed of materials suitable
for the intended environment with full consideration for anticipated atmospheric
contaminants and corrosive compounds. The enclosure shall be sufficiently rugged to
withstand normal handling and assembly operations without damage to any seals provided.
13.5
To ensure that damage affecting safety of operation will not occur during normal
operational conditions of the sealed device, three samples shall be preconditioned by oven
aging according to 13.5.1 and subjected to an air leakage test according to 13.5.2.
13.5.1
Oven aging
If the device contains a gasket or seal of elastomeric or thermoplastic material or a composition
gasket utilizing an elastomeric material, each sample shall be subjected to temperature aging in a
circulating air oven in accordance with the following formula:
t = 2685e
− ( 0.0693 )( T − T1)
where
t
=
the test time in hours
e
=
2.7183
T
=
the aging temperature in °C
T1 = the maximum rated operating temperature in °C (40°C minimum)
13.5.2
Air leakage test
Each of the samples shall pass one of the following tests:
a) At an initial temperature of 25°C the test samples shall be immersed in water at a temperature
of 50°C to a minimum depth of 25 mm for a minimum of 1 minute. If no bubbles emerge from
the samples during this test, they are considered to be "sealed" for the purpose of this
standard.
- 35 -
ISA-12.12.01-2007
b) The test sample shall be immersed to a minimum depth of 75 mm in water contained in an
enclosure that can be partially evacuated. The air pressure within the enclosure shall then be
reduced by 120 mm of mercury. If no visible bubbles emerge from the samples during this
test, samples are considered to be sealed for the purpose of this standard.
-5
c) The test sample shall be shown to leak at a rate not greater than 10 ml of air per second at a
pressure differential of 1 atmosphere (101.3 kPa) by means of a suitable leak rate detector.
13.5.3 As an alternative to the test detailed in 13.5.1 a gasket of an elastomeric or thermoplastic
material, or a composition gasket utilizing an elastomeric material, shall be tested by
submitting the enclosures to continuous storage for one week in an ambient of (90 ± 5) %
relative humidity and at a temperature of (20 ± 2) K above the maximum service
temperature but at least 80 °C.
In the case of a maximum service temperature above 75 °C the period of one week
specified above will be replaced by a period of 85 hours at (95 ± 2) °C and (90 ± 5) %
relative humidity followed by a period of 85 hours at a temperature of (20 ± 2) K higher
than the maximum service temperature.
14 Evaluation of enclosures for Class II and III
An enclosure that is required to exclude the entry of dust shall pass any one of the tests
according to 14.2, 14.3, or 14.4.
14.1
14.1.1
For the tests in 14.2 or 14.4 a length of conduit may be installed in the enclosure under
test to equalize the internal and external pressures, but it shall not serve as a drain.
14.1.2
A gasket used to make an enclosure dust-tight shall be made of material acceptable for
the purpose, e.g., plant-fiber sheet packing or similar material. A gasket of elastomeric
or thermoplastic material may be used if it is resistant to aging when tested in
accordance with 14.1.3. Gaskets shall be either secured or captive if they could be
dislodged during installation or maintenance of the apparatus.
14.1.3
Aging test
A gasket of an elastomeric or thermoplastic material, or a composition gasket utilizing an
elastomeric material, shall be of such quality that samples have a tensile strength of not less than
60 percent and an elongation of not less than 75 percent of values determined for unaged
samples, when subjected to temperature aging in a circulating air oven in accordance with the
following formula:
t = 2685e
− ( 0.0693 )( T − T1)
where
t
e
T
=
=
=
T1 =
the test time in hours
2,7183
the aging temperature in °C
the maximum rated operating temperature in °C (40°C minimum)
ISA-12.12.01-2007
14.1.4
- 36 -
As an alternative to the test detailed in 14.1.3 a gasket of an elastomeric or thermoplastic
material, or a composition gasket utilizing an elastomeric material, shall be tested by
submitting the enclosures to continuous storage for one week in an ambient of (90 ± 5) %
relative humidity and at a temperature of (20 ± 2) K above the maximum service
temperature but at least 80 °C.
In the case of a maximum service temperature above 75 °C the period of one week
specified above will be replaced by a period of 85 hours at (95 ± 2) °C and (90 ± 5) %
relative humidity followed by a period of 85 hours at a temperature of (20 ± 2) K higher
than the maximum service temperature.
14.2
Dust-blast method
The enclosure shall be subjected to a blast of compressed air mixed with dry Type 1 generalpurpose Portland cement (or equivalent) using a suction-type sandblast gun that is equipped with
a 4.8-mm diameter air jet and a 9.5-mm diameter nozzle. The air shall be at a supply pressure of
620-690 kPa. The cement is to be supplied by a suction feed. A minimum of 6 kg/m of test length
(sum of height, width, and depth) of the enclosure under test is to be applied at a minimum rate of
2.3 kg per minute. The nozzle is to be held 305-381 mm from the enclosure, and the blast of air
and cement is to be directed at all points of potential dust entry, such as, but not limited to,
seams, joints, and external operating mechanisms. There shall be no visible dust inside the
enclosure at the end of this test.
14.3
Circulating dust method
The test is made using equipment in which talcum powder is maintained in suspension in a
suitable closed chamber. The talcum powder used shall pass through a square-meshed sieve
whose nominal wire diameter is 50 µm and whose nominal width between wires is 75 µm. The
3
amount of talcum powder used shall be 2 kg/m of the test chamber volume. It shall not have
been used for more than 20 tests.
Enclosures shall be determined to fit in one of two categories:
a) enclosures where the normal working cycle of the apparatus causes a reduction in the air
pressure within the enclosure below the surrounding atmosphere (e.g., caused by thermal
cycling effect); or
b) enclosures where reductions in pressure below the surrounding atmospheric pressure are not
caused by normal cycles of the apparatus.
For enclosures of category (a) the enclosure under test shall be supported inside the test chamber
and the pressure inside the enclosure is maintained below the surrounding atmospheric pressure
by a vacuum pump. The suction connection shall be made to a hole specifically provided for this
test. If not otherwise specified in the relevant product standard, this hole shall be in the vicinity of
the vulnerable parts. If it is impracticable to make a special hole, the suction connection shall be
made to the cable inlet hole. If there are other holes (e.g. more cable inlet holes or drain holes)
these shall be treated as intended for normal use on site. The object of this test is to draw into the
enclosure, by means of depression a volume of air 80 times the volume of the sample enclosure
tested without exceeding the extraction rate of 60 volumes per hour. In no event shall the
depression exceed 2 kPa (20 mbar). If an extraction rate of 40 to 60 volumes per hour is obtained
the duration of the test is 2 hours. If, with a maximum depression of 2 kPa (20 mbar) of water, the
extraction rate is less than 40 volumes per hour, the test shall be continued until 80 volumes have
been drawn through, or a period of 8 hours has elapsed. For an enclosure of category (b), the
apparatus under test should be supported in its normal operating position inside the test chamber,
but the test chamber shall not be connected to a vacuum pump. Any drain hole normally open
shall be left open for the duration of the test. The test shall continue for a period of 8 hours.
- 37 -
ISA-12.12.01-2007
If it is not possible to place the complete assembly in the test chamber, one of the following
procedures shall be used:
a) Individual testing of separate enclosed sections of the apparatus
b) Testing of representative parts of the apparatus (such as doors, ventilating openings, joints,
and shaft seals), with the vulnerable parts of the apparatus (such as terminals and slip rings)
in position at the time of testing
c) Testing of smaller apparatus having the same full-scale design details
The enclosure shall be deemed to pass the test if no visible dust is detected inside the enclosure
at the end of the test.
14.4
Atomized-water method
The enclosure shall be sprayed with atomized water using a nozzle that produces a round pattern
76-102 mm in diameter, 305 mm from the nozzle. The air pressure shall be 207 ± 6 kPa. The
water is to be supplied by a suction feed with a siphon height of 102-204 mm. A minimum of 485
ml/m of test length (sum of height, width, and depth) of the enclosure under test shall be applied
at a minimum rate of 11 liters per hour. The nozzle shall be held 305-381 mm from the enclosure,
and the spray of water shall be directed at all points of potential dust entry including, but not
limited to, seams, joints, and external operating mechanisms. To pass the test there shall be no
visible water inside the enclosure at the end of this test.
15 Drop tests and impact tests
15.1
Portable equipment (equipment intended to be carried by hand) shall be subjected to a drop
test as specified in 15.2. There shall be no damage to the equipment that may affect its
acceptability for use in hazardous (classified) locations.
15.2
Equipment is to be dropped six times, not more than once on any one equipment surface,
from a height of 0,9 m onto a smooth concrete floor. A nonrestrictive guide may be used.
15.3
Equipment with non-metallic enclosures or parts of enclosures intended for use in Class II,
or Class III hazardous (Classified) locations shall be subject to a 2,7 joules impact test prior
to dust tests.
15.3.1
The point(s) of impact shall be the place(s) considered to be the weakest. No location
shall be subjected to more than one impact. The equipment shall be tested completely
assembled, and with any guards installed that are normally supplied as part of the
equipment. Ambient temperature for the test shall be 20°C ± 5°C except where the
electrical enclosure or parts of the enclosure are made from polymeric material. In this
case, the impact tests shall be repeated at the lower ambient temperature of the device
as marked on the equipment label or listed in the product literature.
15.3.2
The test mass shall be fitted with a steel hemisphere of 25 mm diameter. The equipment
shall be positioned on a steel or concrete base so the direction of impact is normal to the
surface being tested. The base shall have a mass of at least 20 kg.
15.4
Class I equipment shall be examined to ensure there is no damage to the equipment that
may affect its acceptability for use in Division 2 locations after impact test specified in the
applicable standards for products in unclassified locations.
ISA-12.12.01-2007
- 38 -
16 Manufacturer's instructional manual
16.1
The manufacturer's instructional material shall include, in addition to the information
required for unclassified locations, the information shown in 16.2 through 16.5 to
emphasize the precautions required when operating the equipment in a Division 2 location.
16.2
The following or equivalent specification for the location of the equipment shall be included:
This apparatus is suitable for use in Class (as applicable), Division 2 groups (as applicable), or
unclassified locations.
16.3
The following or equivalent information for use of the equipment shall be included.
A control drawing shall be provided for all nonincendive field wiring apparatus or associated
nonincendive field wiring apparatus. A nonincendive field wiring system could consist of
equipment investigated as a system or equipment investigated under the nonincendive field wiring
concept. If the nonincendive field wiring and the associated nonincendive field wiring are
investigated as a system, the control drawing shall provide information for proper connection and
installation. If the nonincendive field wiring or associated nonincendive field wiring apparatus is
investigated separately the control drawing shall include applicable electrical parameters to permit
selection of apparatus for interconnection.
The control drawing shall contain notes to explain the following if applicable:
a) The polarity requirements for associated nonincendive field wiring apparatus
b) That associated nonincendive field wiring apparatus shall not be connected in parallel unless
this is permitted by the associated nonincendive field wiring apparatus approval
c) How to calculate the allowed capacitance and inductance values for the field wiring used in the
nonincendive field wiring circuit
d) The hazardous (classified) locations in which the apparatus may be located
e) Permissible connections to simple apparatus
The control drawing shall provide the following information where applicable, either the Division
parameters, the Zone parameters, or both, as shown in Table 1, may be used to designate
electrical parameters on the apparatus and in the installation documents and control drawing.
16.4
If equipment contains sealed components the following shall be provided:
16.4.1
A warning such as: "WARNING: EXPOSURE TO SOME CHEMICALS MAY DEGRADE
THE SEALING PROPERTIES OF MATERIALS USED IN THE FOLLOWING DEVICES";
identification of the sealed devices
16.4.2
The list of materials used in the construction of these devices
Name of sealed device - generic name of the material and the supplier's name and type
designation.
- 39 16.4.3
16.5
16.5.1
ISA-12.12.01-2007
A recommendation for the user to periodically inspect the devices named above for any
degradation of properties and replace if degradation is found
The following warning or equivalent warnings for repair of the equipment shall be included:
If replacement of a component (e.g., fuse, lamp or plug-in module) could ignite the
flammable atmosphere
WARNING: EXPLOSION HAZARD. DO NOT REMOVE OR REPLACE LAMPS, FUSES OR PLUGIN MODULES (AS APPLICABLE) UNLESS POWER HAS BEEN DISCONNECTED OR THE AREA
IS KNOWN TO BE FREE OF IGNITIBLE CONCENTRATIONS OF FLAMMABLE GASES OR
VAPORS.
16.5.2
If disconnecting the equipment supply could ignite the flammable atmosphere
WARNING: EXPLOSION HAZARD. DO NOT DISCONNECT WHILE THE CIRCUIT IS LIVE OR
UNLESS THE AREA IS KNOWN TO BE FREE OF IGNITIBLE CONCENTRATIONS.
16.5.3
If components are relied upon to make the equipment suitable for Division 2 locations,
these components shall be individually identified. The following is an example of
identifying such components:
WARNING: SUBSTITUTION OF THE FOLLOWING COMPONENTS MAY IMPAIR SUITABILITY
FOR DIVISION 2:
Reference designation
K3
OL1
M1
S6
16.6
Description
Relay
Thermal switch
Fan
Switch
Type of Protection
Sealed contacts
Hermetically sealed contacts
Brushless motor
Nonincendive component
Documentation accompanying nonincendive components that are not factory-installed in
equipment shall state the circuit parameters for which the components have been
determined to be safe.
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ISA-12.12.01-2007
Annex A — Normative references
The following referenced documents may be necessary for the application of this document. For
dated references, only the edition cited applies. For undated references, the latest edition of the
referenced document (including any amendments) applies.
ANSI/NFPA 70:2005, National Electrical Code®
ANSI/ISA-60079-0 (12.00.01)-2005, Electrical Apparatus for Use in Class I, Zones 0, 1 & 2
Hazardous (Classified) Locations: General Requirements
ANSI/ISA-61010-1 (82.02.01)-2004, Safety Requirements for Electrical Equipment for
Measurement, Control, and Laboratory Use – Part 1: General Requirements
NEMA 250-2003, NEMA 250-2003, Enclosures for Electrical Equipment (1000 Volts Maximum)
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ISA-12.12.01-2007
Annex B — Common standards – safety requirements for electrical
equipment (informative)
The following are common standards used to verify conformance with safety requirements for
electrical equipment. This list is not comprehensive.
ANSI/ISA 61010-1
ANSI/UL 20
ANSI/UL 50
ANSI/UL 67
ANSI/UL 94
ANSI/UL 153
ANSI/UL 298
ANSI/UL 347
ANSI/UL 427
ANSI/UL 429
ANSI/UL 464
ANSI/UL 486A
ANSI/UL 486B
ANSI/UL 486C
ANSI/UL 486E
ANSI/UL 489
ANSI/UL 498
ANSI/UL 508
ANSI/UL 512
ANSI/UL 514A
ANSI/UL 514B
ANSI/UL 514C
ANSI/UL 595
ANSI/UL 746A
ANSI/UL 746B
ANSI/UL 746C
ANSI/UL 746D
ANSI/UL 746E
ANSI/UL 840
ANSI/UL 864
ANSI/UL 873
ANSI/UL 924
ANSI/UL 943
ANSI/UL 984
ANSI/UL 1004
ANSI/UL 1053
ANSI/UL 1059
ANSI/UL 1097
UL 1104
ANSI/UL 1480
ANSI/UL 1481
UL 1562
ANSI/UL 1585
ANSI/UL 1598
Safety Requirements for Electrical Equipment for Measurement, Control,
and Laboratory Use – Part 1: General Requirements
General-Use Snap Switches
Enclosures for Electrical Equipment
Panelboards
Tests for Flammability of Plastic Materials for Parts in Devices and
Appliances
Portable Electric Lamps
Portable Electric Hand Lamps
High Voltage Industrial Control Equipment
Refrigerating Units
Electrically Operated Valves
Audible Signal Appliances
Wire Connectors and Soldering Lugs for Use with Copper Conductors
Wire Connectors for Use with Aluminum Conductors
Splicing Wire Connectors
Equipment Wiring Terminals for Use with Aluminum and/or Copper A
Conductors
Molded-Case Circuit Breakers and Circuit-Breaker Enclosures
Attachment Plugs and Receptacles
Industrial Control Equipment
Fuseholders
Metallic Outlet Boxes
Fittings for Conduit and Outlet Boxes
Nonmetallic Outlet Boxes, Flush-Device Boxes, and Covers
Marine-Type Electric Lighting Fixtures
Polymeric Materials – Short Term Property Evaluations
Polymeric Materials – Long Term Property Evaluations
Polymeric Materials – Use in Electrical Equipment Evaluations
Polymeric Materials – Fabricated Parts
Polymeric Materials – Industrial Laminates, Filament Wound Tubing
Insulation Coordination Including Clearances and Creepage Distances
for Electrical Equipment
Control Units for Fire Protective Signaling Systems
Temperature-Indicating and -Regulating Equipment
Emergency Lighting and Power Equipment
Ground-Fault Circuit-Interrupters
Hermetic Refrigerant Motor-Compressors
Electric Motors
Ground-Fault Sensing and Relaying Equipment
Terminal Blocks
Double Insulation Systems for Use in Electrical Equipment
Marine Navigation Lights
Speakers for Fire Protective Signaling Systems
Power Supplies for Fire Protective Signaling Systems
Transformers, Distribution, Dry-Type – Over 600 Volts
Class 2 and Class 3 Transformers
Luminaires
ISA-12.12.01-2007
ANSI/UL 1638
UL 1682
ANSI/UL 1740
ANSI/UL 60950-1
ANSI/UL 1971
UL 2111
UL 2225
-44Visual Signaling Appliances – Private Mode Emergency and General
Utility Signaling
Plugs, Receptacles, and Cable Connectors of the Pin and Sleeve Type
Industrial Robots and Robotic Equipment
Safety of Information Technology Equipment, Including Electrical
Business Equipment (Second Edition)
Signaling Devices for the Hearing Impaired
Overheating Protection for Motors
Metal-Clad Cables and Cable-Sealing Fittings for Use in Hazardous
(Classified) Locations
Developing and promulgating sound consensus standards, recommended practices, and technical
reports is one of ISA’s primary goals. To achieve this goal the Standards and Practices
Department relies on the technical expertise and efforts of volunteer committee members,
chairmen and reviewers.
ISA is an American National Standards Institute (ANSI) accredited organization. ISA administers
United States Technical Advisory Groups (USTAGs) and provides secretariat support for
International Electrotechnical Commission (IEC) and International Organization for
Standardization (ISO) committees that develop process measurement and control standards. To
obtain additional information on the Society’s standards program, please write:
ISA
Attn: Standards Department
67 Alexander Drive
P.O. Box 12277
Research Triangle Park, NC 27709
ISBN: