When Should I Choose Armoured Cable?

When does a project need armoured cable?

Armoured cable is usually specified where the cable faces a mechanical risk that the outer sheath alone cannot handle. Typical cases include:

• Direct burial in soil, where stones, digging tools and ground movement can damage the cable.
• Industrial plants, where vehicles, equipment and falling objects can strike the route.
• Tunnels and cable trenches, where the cable is exposed to impact or must be pulled into place.
• Routes where the cable is exposed to pulling stress during installation or later movement.

Conduit or guarded tray may be an alternative in many places. Whether it is allowed depends on local rules, so check those rules before the armour is specified rather than after the order is placed.

Which armour type fits a multicore or single-core circuit?

Armour type follows the cable construction as well as the site. Steel wire armour (SWA) is widely used on multicore cables where tensile and mechanical protection are needed. Steel tape armour gives radial protection in many fixed installations.

Single-core AC cable needs more care. Steel around one AC conductor causes magnetic losses (eddy current and hysteresis), which heat the cable. For that reason single-core AC cable is normally armoured with non-magnetic aluminium wire armour (AWA). Sheath bonding for single-core cables is a separate design question, covered in the single-core sheath bonding guide.

Two British standards are often quoted for this construction. BS 5467 covers single-core AWA and multicore SWA cables for 0.6/1 kV use. BS 6724 covers the LSZH-sheathed armoured equivalent. Confirm which standard and construction your project specifies before ordering.

How do the situation and armour choice fit together?

The table below gives a starting point for the buyer's specification. It does not replace the cable standard or the project's electrical design.

These are starting points only. The cable standard edition and the manufacturer datasheet decide the final armour construction.

Does armour make the cable waterproof or fireproof?

No. Armour is not the water barrier. Moisture performance comes from the bedding, the sheath, the water-blocking layers and the installation drainage. A damaged outer sheath can expose the steel to corrosion, and an armoured cable can still fail after water enters. Specify water protection separately, and treat drainage, bedding, joints and sheath integrity as part of the underground design.

Fire performance is a separate requirement. If the project needs low smoke or halogen-free behaviour, specify it with the sheath material, as explained in the flame retardant and LSZH guide.

How do glands, earthing and bonding work with armour?

Cable glands must fit both the cable diameter and the armour type. IEC 62444 covers cable glands for electrical installations, and hazardous-area glands also follow the IEC 60079 series. Check the gland IP rating against the site. IP66 means dust-tight and protected against powerful water jets, and IP68 means continuous immersion under conditions the manufacturer states (IEC 60529). Gland selection is covered in more detail in the cable gland selection guide.

Armour continuity, bonding and earth-fault performance must be verified. Do not assume the armour alone is an adequate protective conductor without calculation. Armour selection and earthing must be coordinated with the electrical protection design from the start.

Frequently asked questions