IEC TS 60079-40:2015

Explosive atmospheres - Part 40: Requirements for process sealing between flammable process fluids and electrical systems

IEC TS 60079-40:2015(E) provides specific requirements for process sealing between a flammable process fluid and an electrical system where a failure could allow the migration of the process fluid directly into the premises wiring system. This document contains requirements for evaluation, construction and testing of single process seal equipment, dual process seal equipment, and add-on secondary process seals. The requirements of this document do not apply to conduit sealing devices, cable glands and other wiring sealing methods addressed in the IEC 60079 series or other standards. Requirements for basic electrical safety and explosion protection are not addressed by this document, but may apply to the equipment under investigation. The effects of leakage to the environment are not addressed by this document. Keywords: process sealing between a flammable process fluid and an electrical system

General Information

• Status: Published
• Publication Date: 04-Feb-2015
• ICS: 29.260.20 - Electrical apparatus for explosive atmospheres
• Technical Committee: TC 31 - Equipment for explosive atmospheres
• Drafting Committee: WG 30 - TC 31/WG 30
• Current Stage: PPUB - Publication issued
• Start Date: 05-Feb-2015
• Completion Date: 15-May-2015

Overview

IEC TS 60079-40:2015 - Explosive atmospheres - Part 40: Requirements for process sealing between flammable process fluids and electrical systems - specifies requirements for design, evaluation and testing of process seals where a failure could allow a flammable process fluid to migrate into the premises wiring system. It covers single process seal equipment, dual process seal equipment and add‑on secondary process seals. The document is focused on preventing migration of flammable process fluids into electrical wiring; it does not cover conduit seals, cable glands or basic electrical safety/explosion protection measures, nor environmental leakage effects.

Key topics and technical requirements

• Scope & definitions: clear terminology for primary/secondary process seals, single vs dual process seal equipment, process-connected equipment, and equipment with moving parts.
• Design categories: requirements for single process seal equipment (single barrier), dual process seal equipment (redundant barriers) and add‑on secondary process seals for unspecified equipment.
• Type verification and testing: structured test program including conditioning, temperature cycling, pressure cycling, leakage testing, burst pressure testing and verification of annunciation systems.
• Special cases: requirements for equipment with limited pressure at the electrical connections, purged/pressurized assemblies and seals with moving parts.
• Marking & instructions: identification and user guidance required for compliant equipment, including installation and maintenance instructions.
• Annunciators & venting: verification of annunciation effectiveness and procedures for venting/venting pressure determination for dual-seal solutions.

Practical applications

IEC TS 60079-40:2015 is directly applicable wherever flammable process fluids interface with electrical systems and where a seal failure could allow fluid migration into premises wiring. Typical users include:

• Equipment manufacturers designing sensors, transmitters, pumps or other process-connected electrical equipment requiring process seals.
• Design and safety engineers in oil & gas, petrochemical, chemical and industrial process plants evaluating sealing strategies.
• Test laboratories and certification bodies performing type verification, leakage and burst testing.
• Maintenance and inspection teams implementing installation, maintenance and marking requirements to sustain safe operation.

Using this specification helps reduce the risk of explosive atmospheres originating from process fluid migration into electrical wiring and supports compliance with the wider IEC 60079 explosive atmospheres framework.

Related standards

• IEC 60079 series (general standard for explosive atmospheres)
• Normative references in the TS include IEC 60079-0 and IEC 60079-2; guidance may also reference IEC 60079-10-1 and IEC 60079-20-1 for zoning and gas properties.

Standards Content (Sample)

IEC TS 60079-40 ®
Edition 1.0 2015-02
TECHNICAL
SPECIFICATION
Explosive atmospheres –
Part 40: Requirements for process sealing between flammable process fluids
and electrical systems
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IEC TS 60079-40 ®
Edition 1.0 2015-02
TECHNICAL
SPECIFICATION
Explosive atmospheres –
Part 40: Requirements for process sealing between flammable process fluids

and electrical systems
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.260.20 ISBN 978-2-8322-2248-5

– 2 – IEC TS 60079-40:2015 © IEC 2015
CONTENTS
FOREWORD . 3
1 Scope . 5
2 Normative references. 5
3 Terms and definitions . 5
4 General requirements . 8
4.1 Basis for requirements . 8
4.2 Single process seal equipment . 9
4.3 Dual process seal equipment . 9
4.4 Equipment with limited pressure at the electrical connections . 9
4.5 Purged or pressurized equipment . 9
4.6 Add-on secondary process seals . 9
4.7 Annunciators . 10
5 Type verifications and tests . 10
5.1 Test sample . 10
5.2 Single process seal equipment . 10
5.2.1 Order of conditioning . 10
5.2.2 Temperature cycling . 10
5.2.3 Pressure cycling . 11
5.2.4 Leakage test . 12
5.2.5 Burst pressure test . 12
5.3 Dual process seal equipment . 12
5.3.1 Primary process seal leakage test . 12
5.3.2 Primary process seal burst pressure test . 12
5.3.3 Venting pressure determination . 12
5.3.4 Verification of annunciation effectiveness . 13
5.3.5 Secondary process seal leakage test . 13
5.4 Verification of limited pressure effectiveness . 13
6 Marking . 13
7 Instructions. 13
Annex A (informative) Conditioning and test flowchart . 15
Bibliography . 17

Figure 1 – Equipment process sealing components . 6
Figure 2 – Examples of add-on secondary process seals . 8
Figure 3 – Temperature cycle conditioning profile . 11
Figure A.1 – Conditioning and test flowchart . 16

Table 1 – Leakage test pressures . 12
Table 2 – Burst test pressures . 12

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
EXPLOSIVE ATMOSPHERES –
Part 40: Requirements for process sealing between
flammable process fluids and electrical systems

FOREWORD
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The main task of IEC technical committees is to prepare International Standards. In
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• the required support cannot be obtained for the publication of an International Standard,
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• the subject is still under technical development or where, for any other reason, there is the
future but no immediate possibility of an agreement on an International Standard.
Technical specifications are subject to review within three years of publication to decide
whether they can be transformed into International Standards.
IEC 60079-40, which is a technical specification, has been prepared by IEC technical
committee 31: Equipment for explosive atmospheres.

– 4 – IEC TS 60079-40:2015 © IEC 2015
The text of this technical specification is based on the following documents:
Enquiry draft Report on voting
31/1134/DTS 31/1170/RVC
Full information on the voting for the approval of this technical specification can be found in
the report on voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts in the IEC 60079 series, published under the general title Explosive
atmospheres, 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 website under "http://webstore.iec.ch" in the data
related to the specific publication. At this date, the publication will be
• transformed into an International standard,
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
A bilingual version of this publication may be issued at a later date.

EXPLOSIVE ATMOSPHERES –
Part 40: Requirements for process sealing between
flammable process fluids and electrical systems

1 Scope
This document provides specific requirements for process sealing between a flammable
process fluid and an electrical system where a failure could allow the migration of the process
fluid directly into the premises wiring system.
NOTE Some definitions differentiate the terms “flammable” and “combustible” liquids on the basis of their
flashpoints. Combustible liquids under conditions of elevated pressure and/or temperature can lead to the
formation of flammable mists and aerosols which are within the scope of this technical specification.
This document contains requirements for evaluation, construction and testing of single
process seal equipment, dual process seal equipment, and add-on secondary process seals.
The requirements of this document do not apply to conduit sealing devices, cable glands and
other wiring sealing methods addressed in the IEC 60079 series or other standards.
Requirements for basic electrical safety and explosion protection are not addressed by this
document, but may apply to the equipment under investigation. The effects of leakage to the
environment are not addressed by this document.
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 60079-2, Explosive atmospheres – Part 2: Equipment protection by pressurized enclosure
"p"
3 Terms and definitions
For the purposes of this document the following terms and definitions apply.
NOTE See Figure 1 for a graphical representation of the various process seal components.

– 6 – IEC TS 60079-40:2015 © IEC 2015
Premises
Wiring
System
Secondary
Process
Seals
Vent
(when provided)
Electrical Equipment
Electrical Equipment
Primary
Process
Seal
Process Fluid
IEC
Figure 1 – Equipment process sealing components
3.1
dual process seal equipment
equipment which incorporates, along any single potential leakage path, a primary process
seal and one or more secondary process seals such that the failure of two or more
independent process seals is required to allow migration of process fluids from their designed
containment into the premises wiring system
3.2
process connected equipment
electrical equipment that contains a process seal and is intended for connection to an external
system that contains the process fluid
3.3
process fluid
gas, liquid or vapour that is used in or is a by-product of an industrial process
Note 1 to entry: For the purposes of this technical specification, use of the term process fluid refers to a
flammable process fluid. For further information, refer to IEC 60079-0, IEC 60079-10-1, and IEC 60079-20-1.
3.4
process seal
seal between the electrical system and a flammable process fluid where a failure could allow
the migration of the process fluid into the premises wiring system
Note 1 to entry: Although an entire containment system may constitute a potential source of release under
unusual conditions, this technical specification recognizes the concept of infallible containment as defined in
IEC 60079-2.
3.5
single process seal equipment
equipment that incorporates, along any single potential leakage path, a single sealing
structure such that a failure of the seal would result in the migration of the process fluid from
the designed containment into the premises wiring system
Note 1 to entry: Single process seal equipment in compliance with this document is considered to have a
negligible probability of failure when used in accordance with the manufacturer's specification.

3.6
primary process seal
process seal that is directly in contact with process fluids under conditions of normal
operation
3.7
secondary process seal
process seal that comes into contact with process fluids only in the case of a primary process
seal failure
3.8
process seal with moving parts
process seal containing mechanical parts that, under conditions of normal operation, are
capable of motion relative to other parts of the s
...