Is armoured cable mandatory in hazardous areas?
Abstract
Not under IEC 60079-14 itself. It requires suitable sheathed cables protected against mechanical damage along the route. Armour is one way to do that; ducts, trays, covers or routing are others. Many national codes, project specifications and the NEC set stricter wiring methods.
No, not under IEC 60079-14 itself. The standard requires cables suitable for the conditions of service, of an accepted construction (for example sheathed cables or mineral insulated cables), and protected against mechanical damage, corrosion, chemicals and heat along their whole route. Armour is one common way to provide the mechanical protection, but routing, cable trays with covers, ducts or conduit can do the same. Many national codes, company standards and the North American NEC go further, so the project specification often makes armour mandatory in practice.
Short answer
- IEC 60079-14: no general armour requirement; the cable must be suitable and protected where damage is possible.
- Accepted fixed-wiring constructions in the 2007 and 2013 editions were cables with a thermoplastic, thermosetting or elastomeric sheath, mineral insulated metal-sheathed cables and special cables (such as flat cables) with suitable glands; the 2024 edition reduced the cable clause to minimum aspects.
- Where damage is likely (traffic, lifting, impact, vermin, maintenance access), armour or another form of mechanical protection is needed.
- If armour is used, it must be bonded into the equipotential bonding system and terminated in a gland designed for armoured cable that keeps the type of protection.
- Intrinsically safe circuits follow their own rules; for example Irish HSA guidance notes armour or screening for multicore IS cables in Zone 0.
- North America uses prescribed wiring methods instead: in Class I Division 1 these include threaded rigid metal conduit, Type MI cable, or metal-clad Type MC-HL cable under restrictions.
What IEC 60079-14 actually asks for
The installation standard deals with the cable as part of the explosion protection. It has to stay intact so that no live conductor is exposed and so that the cable does not carry gas into or out of an enclosure. Its main demands are:
- Suitable construction. The 2007 edition listed sheathed cables of compact, circular form (so that the gland can seal on them), mineral insulated cables, and special cables such as flat cables only with glands made for them. The 2024 edition keeps only the minimum aspects and leaves product requirements to the cable standards.
- Suitability for the environment. Temperature, UV, oils and solvents, and the 2024 edition's adverse-conditions annex (low temperature, solar radiation, icing).
- Flame propagation. The cable selection clause covers resistance to flame propagation.
- Avoidance of damage. Cables must be protected against mechanical damage, corrosion, chemical attack and heat; clause 8.2.1 of the 2024 edition carries this title.
How the protection is achieved is left to the designer. The 2007 text gives installation in conduit or the choice of armoured, screened, seamless aluminium sheathed, mineral insulated or semi-rigid sheathed cables as examples, which shows that armour is one option among several. In a pipe rack well above walkways, an unarmoured cable on a ladder tray may be adequate. At floor level next to forklift traffic, it is not.
When armour is the right choice
| Situation | Typical solution |
|---|---|
| Buried cables | Armoured cable, or cable in duct, to the national wiring rules |
| Cables at low level, near traffic or lifting | Armour plus routing or covers |
| Offshore and many process plants | Armoured or braided cables, often required by the client specification |
| Rodent or termite exposure | Armour or metallic braid |
| Instrument cables high on covered trays | Unarmoured, screened cable is often accepted |
| Intrinsically safe multicore in Zone 0 | Follow the IS rules; armour or screening is a common requirement |
Armour brings duties of its own. It is an exposed conductive part, so it must be connected to the equipotential bonding system; IEC 60079-14 lists cable armour and metal conduit among the parts to be bonded and has a separate clause on armour bonding in intrinsically safe installations. On flameproof (Ex d) enclosures the armour gland must also meet the cable entry selection rules, which may call for a barrier gland. The gland must clamp the armour properly; a loose armour termination is both a bonding fault and a mechanical weak point.
Example: A tank farm has cables from a pump motor in Zone 1 to a local control station 5 m away and then to a substation 200 m away. The run inside the bund is at ground level where vehicles and maintenance crews pass, so the client specifies steel wire armoured cable for the whole route. The armour is bonded at the motor and control station glands, and an armour-type gland suitable for the Ex d terminal box is chosen using the selection flowchart. The same project accepts unarmoured screened instrument cables on covered trays high on the pipe rack.
North American and national practice
In NEC (NFPA 70) installations the wiring method is part of the code, not a design choice. For Class I Division 1, the methods include threaded rigid metal or intermediate metal conduit, Type MI cable with listed fittings, and Type MC-HL metal-clad cable, the latter limited to industrial establishments with restricted public access where only qualified persons service the installation (as described in a 2017 IAEI summary of section 501.10; the 2026 edition of NFPA 70 is current, so check the edition adopted locally). IEC-based codes and many national rules (for example for buried cables) can also prescribe armour. Always check the code adopted locally and the owner's specification.
Common mistakes
- Assuming armour is a legal requirement everywhere, or the opposite, that it can be left out anywhere.
- Not bonding the armour, or bonding it through a gland that does not clamp it.
- Using armour as the only protection against chemicals or heat; the sheath and insulation must also suit the conditions.
Related on excodex
- Ex installation basics under IEC 60079-14
- Cable glands for hazardous areas: barrier glands, compound glands and selection
- Can conduit be used instead of cable glands under IEC 60079-14?
- Can intrinsically safe and non-IS cables run in the same cable tray?
- Standards space: IEC 60079-14
Standards and further reading
- IEC 60079-14, design, selection and installation of electrical installations (edition 6, 2024), cable selection, avoidance of damage, armour bonding: preview
- IEC 60079-14:2007 (edition 4), quoted where the text names that edition; public text as AS/NZS 60079.14:2009
- P. Thurnherr (convenor of IEC maintenance team MT 60079-14) and G. Schwarz, "Electrical installations: design, selection, erection and inspection", presentation on IEC 60079-14, IECEx International Conference 2015, Gdańsk: slides
- Health and Safety Authority (Ireland), instrumentation and control apparatus in explosive atmospheres: hsa.ie
- NFPA 70, National Electrical Code, Article 501 wiring methods; IAEI Magazine, wiring requirements in Class I Division 1 locations (2017): iaeimagazine.org
This article is general technical information prepared by the excodex editorial team. It does not replace the applicable standards, the equipment certificates and instructions, national regulations or the assessment of a competent person.