IEC 60079-14 governs the design, selection, and erection of electrical installations in hazardous areas. This unit covers personnel qualifications, documentation requirements, cable selection, cable gland coding and selection, light metal content limits, static electricity control, and earthing principles.
Learning Objectives
State the knowledge requirements for operatives, responsible persons, and designers
List the documentation required before and during hazardous area installation
State the cable requirements for fixed wiring in Zone 1 and Zone 2
State light metal content limits for EPL Ga and EPL Gb locations
Describe bonding, earthing, and potential equalisation requirements
State the static electricity surface area limits from IEC 60079-14 Table 5
Personnel Qualifications
IEC 60079-14 defines competency for three categories:
Operatives/Technicians: understand Ex protection principles, marking, certificate content, PTW and safe isolation importance, IEC 60079-14 installation techniques
Responsible Persons: general electrical engineering, ability to read drawings, working knowledge of Ex standards, quality assurance basics
Designers: detailed knowledge of all protection principles, certificate content, installation design, PTW systems, and IEC 60079-17 inspection requirements
Cable Selection
Fixed equipment cables in Zone 1 and 2 must be:
Sheathed with thermoplastic, thermosetting, or elastomeric material
Circular, compact, with extruded bedding; fillers non-hygroscopic
Alternatively: mineral insulated metal sheathed (MIMS)
UK practice: SWA (steel wire armour) for onshore; SWB (steel wire braid) for offshore. Aluminium conductors: minimum 16mm² CSA, suitable terminations. Cable surface temperature must not exceed area T-class.
Cable Gland Codes
Code
Meaning
A
Outer seal only (unarmoured cable)
D
Inner seal and armour lock
E
Inner seal, outer seal, and armour lock
BARR
Inner barrier seal, outer seal, and armour lock
W
Single steel wire armour (SWA)
X
Braided wire armour (SWB)
Example: E1FW = inner seal + outer seal + armour lock, size 1, flameproof certified, SWA cable.
Light Metal Limits and Static Electricity
Light metals (Al, Mg, Ti, Zr) can cause thermite sparks against rusty steel:
EPL
Limit
Ga
Al + Mg + Ti + Zr ≤ 10%; Mg + Ti + Zr ≤ 7.5%
Gb
Mg + Ti ≤ 7.5%
Gc
No limitation
Non-metallic surfaces (plastic cable trays) accumulate static. Control by: insulation resistance ≤1GΩ; or limit surface area (IEC 60079-14 Table 5 — EPL Gb IIC: max 2,000mm²; EPL Gb IIB: 10,000mm²).
Earthing and Bonding
All exposed and extraneous conductive parts must connect to the equipotential bonding system. The bonding system includes: protective conductors, metal conduits, cable armour/sheathing, metallic structural parts — NOT neutral conductors. Connections must be secure against self-loosening and minimise corrosion risk.
Earthing systems for hazardous areas (IEC 60079-14): TN-S (separate neutral and protective throughout), TT (independent earth electrodes), IT (no direct earth — insulation monitoring device required).
Quick Check — 5 Questions
Test key concepts from this unit before moving on.
Q1Summary
What gland code designates a braided wire armour (SWB) cable?
X = braided wire armour (SWB). W = single steel wire armour (SWA). Y = aluminium wire armour. Z = tape armour.Ref: BS6121 / EN50262
Q2Summary
Minimum bend radius for cables in hazardous areas per IEC 60079-14?
Minimum bend radius 8× cable outer diameter, commencing at least 25mm from the cable gland end. Tighter bends damage insulation and armour.Ref: IEC 60079-14
Q3Summary
A plastic cable tray in a Zone 1 IIB area has surface area 15,000mm². Compliant?
For EPL Gb in Group IIB, non-metallic surface area limit is 10,000mm². 15,000mm² exceeds this.Ref: IEC 60079-14 Table 5
Q4Summary
Unused cores in a non-IS multi-core cable in a Zone 1 area must be:
Unused non-IS cores: connect to earth at hazardous area end, OR adequately insulate using suitable terminations. Tape alone is not permitted.Ref: IEC 60079-14
Q5Summary
What does gland code "A2F" designate?
A = outer seal only (unarmoured); 2 = size; F = flameproof. A2F = certified Ex d gland for unarmoured cable.Ref: EN50262 / BS6121
IEC 60079-14 governs the design, selection, and erection of electrical installations in hazardous areas. This unit covers personnel qualifications, documentation requirements, cable selection, cable gland coding and selection, light metal content limits, static electricity control, and earthing principles.
Learning Objectives
State the knowledge requirements for operatives, responsible persons, and designers
List the documentation required before and during hazardous area installation
State the cable requirements for fixed wiring in Zone 1 and Zone 2
State light metal content limits for EPL Ga and EPL Gb locations
Describe bonding, earthing, and potential equalisation requirements
State the static electricity surface area limits from IEC 60079-14 Table 5
10.3 Personnel Qualifications
IEC 60079-14 defines three levels of competency for persons involved in the design, selection, and erection of Ex installations.
Operatives/Technicians
(a) Understanding of Ex protection principles; (b) understanding of protection types and marking; (c) understanding of design aspects affecting protection; (d) understanding of certificate content and IEC 60079-14; (e) general understanding of IEC 60079-17 inspection requirements; (f) familiarity with specific installation techniques; (g) understanding of the importance of PTW systems and safe isolation in Ex protection contexts.
Responsible Persons
General electrical engineering understanding; ability to read and assess engineering drawings; practical understanding of Ex protection principles and techniques; working knowledge of relevant Ex standards; basic knowledge of quality assurance, documentation, and measurement calibration.
Designers
Detailed knowledge of all protection principles; detailed knowledge of certificate content; understanding of practical installation skills; detailed knowledge of PTW systems and safe isolation; detailed knowledge of specific installation techniques in IEC 60079-14; general understanding of IEC 60079-17 inspection requirements.
10.4 Documentation
A verification dossier must be prepared for every installation. Required documentation includes:
Area classification documents and drawings showing zone extents
Gas/vapour group and T-class requirements for each area
Manufacturer's instructions for equipment selection and installation
Documents for X-suffix certificate equipment (special conditions)
IS system descriptive documents
Purge rate calculations (for analyser houses)
Wiring system plans and circuit identification schedules
Cable entry system selection records
Initial inspection records
Installer/qualified person declaration
10.7 Cable Types
Fixed equipment cables for Zone 1 and 2:
Sheathed with thermoplastic, thermosetting, or elastomeric material
UK practice: SWA (Steel Wire Armour) for onshore; SWB (Steel Wire Braid) for offshore. Gland designations mark W (wire armour) and X (braid armour).
Aluminium conductors: permitted but minimum 16mm² CSA; suitable termination connectors required. Cable surface temperature must not exceed the T-class of the installation. The minimum cable bend radius is 8× the outer cable diameter, commencing at least 25mm from the cable gland end.
10.10 Cable Glands
Cable glands must:
Firmly secure the cable entering the equipment
Maintain IP rating of the enclosure
Maintain earth continuity between equipment and cable armour
Ensure containment of internal explosion in Ex d (barrier gland inner seal)
Maintain restricted breathing integrity in Ex nR equipment
Code
Meaning
A
Outer seal only — unarmoured cable
D
Inner seal and armour lock — armoured cable
E
Inner seal, outer seal, and armour lock — armoured cable
BARR
Inner barrier seal, outer seal, armour lock — barrier gland for Ex d
W
Single steel wire armour (SWA)
X
Braided wire armour (SWB)
Y
Aluminium wire armour
Z
Tape armour
Example markings:
A2F — flameproof gland, unarmoured cable, outer seal only
BARR — barrier gland (Ex d direct entry, SWA cable)
10.12 Light Metal Content Limits
Light metals (aluminium, magnesium, titanium, zirconium) can cause thermite sparks when contacting rusty steel. IEC 60079-14 limits their content in installation materials:
EPL Requirement
Limit
Ga (Zone 0)
Total Al + Mg + Ti + Zr ≤ 10%; Mg + Ti + Zr ≤ 7.5%
Limitation of surface area per IEC 60079-14 Table 5
EPL
Group IIA
Group IIB
Group IIC
Ga
5,000mm²
2,500mm²
400mm²
Gb
10,000mm²
10,000mm²
2,000mm²
Gc
10,000mm²
10,000mm²
2,000mm²
10.14 Earthing and Bonding Principles
Earthing — connection of exposed conductive parts of an installation to the main earthing terminal. Bonding — electrical connection maintaining exposed and extraneous conductive parts at substantially the same potential.
All exposed and extraneous conductive parts must be connected to the equipotential bonding system. The bonding system may include protective conductors, metal conduits, metal cable sheaths, steel wire armouring, and metallic structural parts — but must NOT include neutral conductors.
Potential Equalisation in Hazardous Areas
IEC 60079-14 requires potential equalisation for all hazardous area installations. All exposed and extraneous conductive parts must be connected to the equipotential bonding system. This eliminates potential differences that could cause sparking between adjacent metalwork.
10.15 Earthing System Types
System
Description
Notes for Hazardous Areas
TN-S
Separate neutral (N) and protective earth (PE) conductors throughout
Preferred for hazardous areas — no shared N/PE paths
TT
Independent earth electrodes for power source and exposed parts
RCD protection required
IT
No direct connection between live parts and earth; exposed parts earthed
Insulation monitoring device (IMD) required; first earth fault must be located and cleared promptly
Unit 10 Knowledge Check — 10 Questions
CompEx-style questions covering the full unit content.
Q1Unit {num}
A cable with SWB (steel wire braid) armour is being terminated. Which gland code designates braid armour?
X = braided wire armour (SWB). W = single SWA. Y = aluminium wire armour.Ref: BS6121
Q2Unit {num}
Minimum cable bend radius per IEC 60079-14?
8× cable outer diameter, starting at least 25mm from the cable gland end.Ref: IEC 60079-14
Q3Unit {num}
A plastic cable tray in Zone 1 IIB has 15,000mm² surface area. Compliant?
Unused non-IS cores: earth at HV end or adequately insulate with suitable terminations. Tape alone not permitted.Ref: IEC 60079-14
Q5Unit {num}
What does gland "E1FW" designate?
E = inner seal + outer seal + armour lock; 1 = size; F = flameproof certified; W = single wire armour (SWA).Ref: EN50262 / BS6121
Q6Unit {num}
What is the maximum non-metallic surface area for a Zone 0 (EPL Ga) IIC installation?
For EPL Ga in Group IIC: maximum 400mm². This is the most restrictive limit — IIC gases are most easily ignited by electrostatic discharge.Ref: IEC 60079-14 Table 5
Q7Unit {num}
A cable gland marked with suffix X on its certificate — what does this mean?
X suffix on a cable gland certificate means special conditions apply. IEC 60079-14 specifies: X-suffix glands for fixed installations only; if the cable may be subject to pulling or twisting stress, an additional mechanical clamp must be provided within 300mm of the cable gland end.Ref: IEC 60079-0
Q8Unit {num}
Multi-stranded conductors must be protected against strand separation by:
IEC 60079-14 requires multi-stranded and fine-stranded conductors to be protected by cable lugs or core-end ferrule sleeves. Soldering alone is not permitted — a cold-soldered joint can lose mechanical integrity causing strand separation.Ref: IEC 60079-14
Q9Unit {num}
Which earthing system requires an insulation monitoring device and prompt correction of first earth faults?
IT system: no direct live-to-earth connection; exposed parts earthed. An IMD detects the first earth fault — which must be found and cleared before a second fault creates a dangerous situation.Ref: IEC 60079-14
Q10Unit {num}
A conductor joint in a Zone 1 hazardous area cannot be made in an enclosure. What alternative methods does IEC 60079-14 permit?
Where joints cannot be in an enclosure (subject to no mechanical stress): epoxy-filled, compound-filled, or sleeved with heat-shrunk or cold-shrunk tubing per manufacturer instructions. The preferred option is always an enclosure with appropriate Ex protection.Ref: IEC 60079-14