ISO 80079-37:2016

ISO 80079-37
Edition 1.0 2016-02
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Explosive atmospheres –
Part 37: Non-electrical equipment for explosive atmospheres – Non electrical
type of protection constructional safety “c”, control of ignition source “b”, liquid
immersion “k”
Atmosphères explosives –
Partie 37: Appareils non électriques destinés à être utilisés en atmosphères
explosives – Mode de protection non électrique par sécurité de construction "c",
par contrôle de la source d'inflammation "b", par immersion dans un liquide "k"

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ISO 80079-37
Edition 1.0 2016-02
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Explosive atmospheres –
Part 37: Non-electrical equipment for explosive atmospheres – Non electrical

type of protection constructional safety “c”, control of ignition source “b”, liquid

immersion “k”
Atmosphères explosives –
Partie 37: Appareils non électriques destinés à être utilisés en atmosphères

explosives – Mode de protection non électrique par sécurité de construction "c",

par contrôle de la source d'inflammation "b", par immersion dans un liquide "k"

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 13.230; 29.260.20 ISBN 978-2-8322-3181-4

– 2 – ISO 80079-37:2016 © ISO 2016
CONTENTS
FOREWORD . 5
1 Scope . 7
2 Normative references. 7
3 Terms and definitions . 8
4 Determination of suitability . 9
5 Requirements for equipment with Type of Protection constructional safety “c” . 9
5.1 General requirements . 9
5.2 Ingress protection . 10
5.2.1 General . 10
5.2.2 Ingress protection in special cases . 10
5.3 Seals for moving parts . 10
5.3.1 Unlubricated gaskets, seals, sleeves, bellows and diaphragms . 10
5.3.2 Stuffing box seals (packed glands) . 11
5.3.3 Lubricated seals . 11
5.4 Equipment lubricants, coolants and fluids . 11
5.5 Vibration . 11
5.6 Requirements for moving parts . 11
5.6.1 General . 11
5.6.2 Clearance . 12
5.6.3 Lubrication . 12
5.7 Requirements for bearings . 12
5.7.1 General . 12
5.7.2 Lubrication . 13
5.7.3 Chemical compatibility . 13
5.8 Requirements for power transmission systems . 14
5.8.1 Gear drives . 14
5.8.2 Belt drives . 14
5.8.3 Chain drives. 15
5.8.4 Other drives . 15
5.8.5 Hydrostatic, hydrokinetic and pneumatic equipment . 15
5.9 Requirements for clutches and variable speed couplings . 16
5.9.1 General . 16
5.9.2 Slipping . 16
5.9.3 Friction . 17
5.10 Flexible couplings . 17
5.11 Requirements for brakes and braking systems . 17
5.11.1 Brakes used only for stopping in emergency . 17
5.11.2 Service brakes (including friction brakes and fluid based retarders) . 18
5.11.3 Parking brakes . 18
5.12 Requirements for springs and absorbing elements . 18
5.13 Requirements for conveyor belts . 18
5.13.1 Electrostatic requirements . 18
5.13.2 Materials . 18
5.13.3 Belt tension . 18
5.13.4 Alignment . 19
5.13.5 Earthing and bonding . 19

6 Requirements for equipment with Type of Protection control of ignition source “b” . 19
6.1 General . 19
6.2 Determination of the control parameters . 19
6.2.1 General . 19
6.2.2 Determination of the safety critical values . 20
6.3 Ignition prevention system design and settings . 20
6.3.1 Determining the performance requirements or operating characteristics . 20
6.3.2 Instructions . 20
6.3.3 System lockout . 20
6.3.4 Operator intervention . 21
6.4 Ignition protection of sensors and actuators . 21
6.5 Ignition protection types . 21
6.5.1 Ignition protection type b1 . 21
6.5.2 Ignition protection type b2 . 21
6.5.3 Application of ignition protection types . 22
6.5.4 Requirements for ignition protection types . 23
6.5.5 Programmable electronic devices . 23
7 Requirements for equipment with Type of Protection liquid immersion “k”. 23
7.1 Determination of the maximum / minimum criteria . 23
7.2 Protective liquid . 24
7.3 Equipment construction . 24
7.3.1 General . 24
7.3.2 Working angle . 24
7.3.3 Measures to ensure effectiveness of liquid . 24
7.3.4 Accidental loosening . 25
7.3.5 Level monitoring . 25
7.3.6 Loss of liquid . 25
7.3.7 Open equipment . 26
8 Type tests . 26
8.1 Type tests for equipment with Type of Protection constructional safety “c” . 26
8.2 Type tests for equipment with Type of Protection control of ignition source
“b” . 26
8.2.1 Determination of control parameters . 26
8.2.2 Function and accuracy check of the ignition protection system . 26
8.3 Type tests for equipment with Type of Protection liquid immersion “k” . 26
8.3.1 General . 26
8.3.2 Increased pressure test on enclosed equipment having a sealed
enclosure that contains static, or flowing protective liquid . 26
8.3.3 Overpressure test on enclosed equipment having a vented enclosure . 26
9 Documentation . 26
9.1 Documentation for equipment with Type of Protection constructional safety
“c” . 26
9.2 Documentation for equipment with Type of Protection control of ignition
sources “”b” . 27
9.3 Documentation for equipment with Type of Protection liquid immersion “k” . 27
10 Marking . 28
10.1 General . 28
10.2 Safety devices . 28

– 4 – ISO 80079-37:2016 © ISO 2016
Annex A (informative) Approach and application: equipment with Type of
Protection “c” . 29
A.1 General remarks regarding ignition hazard assessment . 29
A.2 Stuffing box seal (see Table A.2) . 29
A.3 Slide ring seal . 31
A.4 Radial seal . 36
A.5 Belt drives . 40
Annex B (normative) Test requirements . 42
B.1 "Dry run" type test for lubricated sealing arrangements . 42
B.2 Type test for determining the maximum engaging time of clutch assembly . 42
B.2.1 Apparatus . 42
B.2.2 Procedure . 43
Annex C (informative) Methodology: equipment with Type of Protection “b” . 44
Annex D (informative) Approach to assign the required ignition protection type used
for equipment to achieve different EPL . 45
D.1 For EPL Gc and Dc . 45
D.2 For EPL Gb and Db . 45
D.3 For EPL Mb . 45
D.4 For EPL Ga and Da . 46
Annex E (informative) Information on functional safety concept . 47
E.1 ISO 13849-1 . 47
E.2 IEC 61508-1 . 47
E.3 IEC 62061 . 47
E.4 Reliability according to functional safety standards . 47
Bibliography . 49

Figure C.1 – Flow diagram of the procedures described in this document . 44

Table 1 – Minimum ignition protection types required when Ex “b” is selected to
achieve the intended EPL for Group II and III equipment. 22
Table 2 – Minimum ignition protection types required when Ex “b” is selected to
achieve the intended EPL for Group I equipment . 23
Table A.1 – List of examples for some of the thought processes and principles used . 29
Table A.2 – Stuffing box seal . 30
Table A.3 – Slide ring seal . 32
Table A.4 – Radial seal . 37
Table A.5 – Belt drives . 41
Table E.1 – Application of ignition protection type . 48

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
EXPLOSIVE ATMOSPHÈRES –
Part 37: Non-electrical equipment for explosive atmospheres –
Non electrical type of protection constructional safety “c”,
control of ignition source “b”, liquid immersion “k”

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard ISO 80079-37 has been prepared by IEC sub-committee 31M: Non-
electrical equipment and protective systems for explosive atmospheres, of IEC 31: Equipment
for explosive atmospheres.
The text of this standard is based on the following documents of the IEC:
FDIS Report on voting
31M/104/FDIS 31M/110/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table. In ISO, the standard has been approved by 15 P members
out of 20 having cast a vote.
– 6 – ISO 80079-37:2016 © ISO 2016
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
"A list of all parts in the IEC 60079 series, under the general title Explosive atmospheres, as
well as the International Standard 80079 series, can be found on the IEC website."
The committee has decided that the contents of this publication will remain unchanged until
the stability date indicated on the IEC web site under "http://webstore.iec.ch" in the data
related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
.
EXPLOSIVE ATMOSPHERES –
Part 37: Non-electrical equipment for explosive atmospheres –
Non electrical type of protection constructional safety “c”,
control of ignition source “b”, liquid immersion “k”

1 Scope
This part of ISO/IEC 80079 specifies the requirements for the design and construction of non-
electrical equipment, intended for use in explosive atmospheres, protected by the types of
protection constructional safety “c”, control of ignition source “b” and liquid immersion “k”.
This part of ISO/IEC 80079 supplements and modifies the requirements in ISO 80079-36.
Where a requirement of this standard conflicts with the requirement of ISO 80079-36 the
requirement of this standard takes precedence.
Types of Protection “c”, “k” and “b” are not applicable for Group I, EPL Ma without additional
protective precautions.
The types of ignition protection described in the standard can be used either on their own or
in combination with each other to meet the requirements for equipment of Group I, Group II,
and Group III depending on the ignition hazard assessment in ISO 80079-36.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and
are indispensable for its application. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 60079-0, Explosive atmospheres – Part 0: Equipment – General requirements
IEC TS 60079-32-1, Explosive atmospheres – Part 32-1: Electrostatic hazards, Guidance
IEC 60529, Degrees of protection provided by enclosures (IP Code)
ISO 281, Rolling bearings – Dynamic load ratings and rating life
ISO 1813, Belt drives – V-ribbed belts, joined V-belts and V-belts including wide section belts
and hexagonal belts – Electrical conductivity of antistatic belts: Characteristics and methods
of test
ISO 9563, Belt drives – Electrical conductivity of antistatic endless synchronous belts –
Characteristics and test method
ISO 4413, Hydraulic fluid power – General rules and safety requirements for systems and
their components
ISO 4414, Pneumatic fluid power – General rules and safety requirements for systems and
their components
ISO 19353, Safety of machinery – Fire prevention and protection

– 8 – ISO 80079-37:2016 © ISO 2016
ISO 80079-36: 2016, Explosive atmospheres – Non-electrical equipment for explosive
atmospheres – Part 1: Basic method and requirements
EN 13237, Potentially explosive atmospheres – Terms and definitions for equipment and
protective systems intended for use in potentially explosive atmospheres
EN 13501-1, Fire classification of construction products and building elements – Part 1:
Classification using data from reaction to fire tests
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 80079-36,
IEC 60079-0 and the following apply.
3.1
constructional safety “c”
ignition protection where constructional measures are applied so as to protect against the
possibility of ignition from hot surfaces, sparks and adiabatic compression generated by
moving parts
3.2
mechanically generated sparks
sparks produced by mechanical impact or friction burning particles, as well as showers of
particles, produced by impact or friction between two solid materials
3.3
control of ignition source “b”
ignition protection where mechanical or electrical devices are used in conjunction with non-
electrical equipment to manually or automatically reduce the likelihood of a potential ignition
source from becoming an effective ignition source
Note 1 to entry: This might for example be a level sensor used to indicate loss of oil, a temperature sensor to
indicate a hot bearing or a speed sensor to indicate over-speed.
3.3.1
automatic control measure
action taken without manual intervention, to reduce the likelihood of a potential ignition source
from becoming an effective ignition source
3.3.2
manual control measure
action taken by a person as a result of a warning, indication, or alarm, to reduce the likelihood
of a potential ignition source from becoming an effective ignition source
3.3.3
ignition prevention devices/systems
arrangement that converts signals from one or more sensors into an action, or indication, to
reduce the likelihood of a potential ignition source from becoming an effective ignition source
____________
To be published.
3.3.4
safety devices
devices intended for use inside or outside explosive atmospheres but required for or
contributing to the safe functioning of equipment and protective systems with respect to the
risks of explosion
3.4
liquid immersion “k”
type of protection where potential ignition sources are made ineffective or separated from the
explosive atmosphere by either totally immersing them in a protective liquid, or by partially
immersing and continuously coating their active surfaces with a protective liquid in such a way
that an explosive atmosphere which may be above the liquid, or outside the equipment
enclosure, cannot be ignited
3.4.1
protective liquid
a liquid which prevents the explosive atmosphere from making direct contact with potential
ignition sources and thereby ensures the explosive atmosphere cannot be ignited
3.4.2
equipment with a sealed enclosure
totally enclosed equipment that limits the ingress of an external atmosphere during the
expansion and contraction of the internally contained protective liquid during use in service
Note 1 to entry: Such equipment includes any pipework associated with it and often contains an overpressure
relief device.
3.4.3
equipment with a vented enclosure
enclosed equipment that allows the ingress and egress of an external atmosphere through a
breathing device or constricted opening during the expansion and contraction of the internally
contained protective fluid during normal operation
Note 1 to entry: Such equipment includes any pipework associated with it.
3.4.4
open equipment
equipment that is immersed, or has its components immersed, in a protective liquid that is
open to the external atmosphere
Note 1 to entry: For example, an open top vessel with immersed moving components. Such equipment includes
any pipework associated with it.
4 Determination of suitability
Before a decision is made to protect equipment or parts of equipment for use as an assembly,
including interconnecting parts, by the measures described in this standard, it shall have been
subjected to the ignition hazard assessment in accordance with ISO 80079-36.
5 Requirements for equipment with Type of Protection constructional safety
“c”
5.1 General requirements
Equipment designed and constructed according to the applicable safety requirements of the
relevant industrial standards is intended to be capable of functioning in conformity with the
operational parameters established by the manufacturer, including any mechanical and
thermal stresses that they are intended to be subjected to.

– 10 – ISO 80079-37:2016 © ISO 2016
This also applies to interconnecting parts of equipment including joints (e.g. cemented,
soldered, or welded joints).
NOTE This is accomplished by using one or more of the following documents:
• International standards or Technical Specifications
• FDIS of International standards or Technical Specifications
• National Standards or Technical Specifications
• Technical specifications or Test Reports issued by an Ex accredited Test Laboratory
• Technical specifications of industrial associations.
5.2 Ingress protection
5.2.1 General
The degree of ingress protection (IP) as specified in IEC 60529 provided by the outer
enclosures of equipment depends upon its intended duty and the type of environment it is
designed to be used in. An appropriate rating shall be determined as part of the ignition
hazard assessment (see Clause 4) and, if relevant for ignition protection, shall be able to
provide that degree of protection.
NOTE IP degrees of protection according to IEC 60529 are not intended to provide protection against the ingress
of an explosive gas atmosphere.
5.2.2 Ingress protection in special cases
The following points specify the minimum IP rating for enclosures used in the circumstances
described.
a) In the case of equipment intended for use in explosive gas atmospheres, where entry of
foreign objects can cause ignition, but entry of dust is harmless, the required degree of
protection against the entry of foreign objects shall be determined in the ignition hazard
assessment and shall be at least IP20.
b) In the case of equipment intended for use in explosive gas atmospheres, where the entry
of dusts or liquids could cause a malfunction leading to an ignition source, the degree of
protection shall be at least IP5X for dust and IPX4 for liquids.
c) In the case of equipment intended for use in explosive dust atmospheres, where ingress of
dust can result in an ignition source or fire, the degree of protection shall be IP6X.
d) In the case of equipment intended for use in explosive dust atmospheres, where ingress of
dust, foreign objects and liquids are not likely to cause an ignition, no specific degree of
protection is necessary for the purpose of ignition protection.
NOTE An enclosure is often employed for other safety reasons, e.g. IP2X to prevent parts of the body coming into
contact with rotating parts.
5.3 Seals for moving parts
5.3.1 Unlubricated gaskets, seals, sleeves, bellows and diaphragms
Un-lubricated gaskets, seals, sleeves, bellows and diaphragms shall not become an effective
ignition source, e.g. if there is a risk of mechanically generated sparks and hot surfaces which
can become an effective ignition source. Light metals shall not be used for these parts in this
case (see ISO 80079-36).
Non-metallic materials shall be resistant to distortion and degradation which would reduce the
effectiveness of explosion protection within the specified lifetime of operation.

5.3.2 Stuffing box seals (packed glands)
Stuffing box seals (packed glands) shall only be used when instructions are provided by the
manufacturer to limit the maximum surface temperature during operation of the gland;
alternatively an automatic means shall be provided.
5.3.3 Lubricated seals
Seals which normally require the presence of a lubricant which can be replenished to reduce
the likelihood of hot surfaces occurring at their interface with equipment parts shall be
designed to ensure the sufficient presence of lubricant or shall be protected by one of the
following means:
• provision of an effective means to monitor the continued presence of the lubricant; or
• provision of a temperature detection device to warn of increasing temperatures; or
• design of the equipment to be capable of completing the ‘dry run’ type test, as described
in Annex B, without exceeding the maximum surface temperature of the equipment and
without suffering damage which would reduce the effectiveness of its ignition protection.
Monitoring shall be either continuous or by required appropriate inspection and examination.
Where the level of lubricant cannot be easily monitored (e.g. seal containing grease) the
relevant information shall be given in the instructions.
The instructions shall include details relating to the correct lubrication, monitoring and
maintenance of such seals.
5.4 Equipment lubricants, coolants and fluids
Lubricants and coolants, which are required for the protection against incendive hot surfaces
or mechanically generated sparks (see Clause 7) shall have an auto-ignition temperature (see
IEC 60079-20-1) at least 50 K above the maximum surface temperature of the equipment
where the liquid is being used.
NOTE IEC 60079-20-1 is under revision and is expected to be published as ISO/IEC 80079-20-1.
Any fluid which can be released shall not result in an effective ignition source, e.g. due to high
temperature or electrostatic charging.
5.5 Vibration
Effective ignition sources, hot surfaces or mechanically generated sparks or loss of
protection, caused by vibration shall be avoided. Vibration can arise from the equipment itself
or from the place where it is mounted.
The manufacturer shall prepare any necessary installation, operation and maintenance
instructions. In particular, the instructions shall specify the correct operating speed range of
the equipment in order to avoid excessive vibration.
5.6 Requirements for moving parts
5.6.1 General
The ignition hazard assessment (see ISO 80079-36) shall identify those moving parts which
could lead to the occurrence of unsafe vibration or impact or friction. Such parts shall be
constructed in such a way so that they are unlikely to become an effective ignition source
during the specified lifetime of operation of the equipment, taking the EPL into consideration
in combination with the instructions.
Where the melting point of the material used in the construction of moving parts is below the
maximum surface temperature of the equipment, or is not capable of causing incendive hot

– 12 – ISO 80079-37:2016 © ISO 2016
surfaces or mechanical sparks, additional protective measures are not normally necessary
(e.g. the provision of a low melting point sacrificial wear plate; the use of a plastic fan inside a
metal housing, or a metallic fan with sacrificial non-sparking low melting point fan blade-tips).
5.6.2 Clearance
Clearances between un-lubricated moving parts and fixed parts shall be designed such that
likelihood of frictional contact, able to produce an effective ignition source in the form of hot
surfaces or mechanically generated sparks, is appropriate to the intended EPL.
5.6.3 Lubrication
For moving parts needing lubrication to avoid excessive temperatures or mechanically
generated sparks, effective lubrication shall be ensured, e.g. by:
• an oil splash lubricator, or
• a constant oil feed by means of a reservoir, pump and perhaps an oil cooler, or
• an automatic greasing system, or
• an adequate maintenance procedure to provide for routine greasing or oil level verification
by manual or visual means.
If the above measures do not achieve the required EPL of the equipment additional measures
to monitor adequate lubrication shall be applied, e.g. level, flow, pressure or temperature
sensors which operates an alarm or switch function before a critical lubricant condition is
reached, see Clause 6.
Where equipment is designed to process liquids and the presence of the process liquid is
essential for the purpose of lubrication, cooling, quenching, or ignition protection, or when the
safe operation of the equipment (e.g. of a pump) requires special priming considerations, this
shall be stated in the instructions.
5.7 Requirements for bearings
5.7.1 General
Bearings are basically divided into three types, sliding plane motion, sliding rotary motion and
rolling element. When assessing bearings, as part of the ignition hazard assessment required
by ISO 80079-36, at least the following shall be taken into account:
a) the bearing’s suitability for the equipment’s intended duty e.g. speed, temperature, loading
and variations of speed and loading;
b) the bearing’s basic rated life as described in ISO 281 for rolling element bearings (see
also Note 1);
c) the proper fit of the bearings in their housing and on the shaft (tolerances, roundness and
surface quality), taking into consideration the vertical and axial loads on the bearing with
respect to shaft and housing;
d) the correct alignment of the bearings;
e) the axial and radial loading of the bearings caused by thermal expansion of the shaft and
the housing under the most severe operating conditions;
f) protection of the bearing from ingress of water and solids, if necessary to avoid premature
failure;
g) protection of the bearing from electrical currents, including stray circulating currents
(which can cause, for example, incendive sparking, or spark erosion leading to premature
failure, at the point of contact between the ball and ball race of a ball bearing);
h) the provision of adequate lubrication, according to the lubricating regime necessary for the
type of bearing (e.g. for sliding bearings, boundary lubrication, mixed film, or full film
hydrodynamic lubrication are the most commonly used regimes);

i) Maintenance checks at recommended intervals (e.g. vibration, temperature);
j) replacement after unacceptable wear or at the end of its recommended life, whichever
comes first;
k) protection of the bearing from vibration, especially at standstill;
l) the use of low reliability non-metallic bearing cages in industrial applications.
m) Where a special initial running in period is necessary that could lead to an effective
ignition source, information shall be given in the instructions.
NOTE 1 At the present time, no suitable experimental test exists to demonstrate that a given type of bearing has
a low risk of becoming an ignition source in service. Ball and roller bearing manufacturers do, however, quote a
basic rated life corresponding to a probability of mechanical failure occurring during operation (e.g. failure by
deformation of an element, or fatigue flaking or spalling occurring on one of its elements). This basic rating can be
used in the ignition hazard assessment in an attempt to determine the risk of bearing malfunction that might lead to
the production
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