What Is an Armoured Cable Gland?

An armoured cable gland is a cable entry device that terminates a cable with metallic armour — steel wire, aluminium wire or steel tape — by gripping that armour, bonding it to the enclosure earth and sealing the cable where it enters the box. That combination separates it from a standard compression gland, which cannot substitute for it even when the thread and diameter match.

Three duties define the product, and every selection question comes back to them:

• Mechanical retention — the armour is clamped, so pulling or vibration loads the enclosure, not the terminals.
• Electrical bonding — the armour is a conductive path to earth, and the gland closes that path.
• Environmental sealing — the sheath, and on some types the bedding as well, is sealed so water cannot track inside the armour.

Why a Standard Cable Gland Cannot Terminate Armoured Cable

A standard gland seals around one round surface — the outer sheath. An armoured cable has an extra metallic layer between the bedding and the sheath, so a standard gland has nothing to grip and nothing to bond. Three failures follow, usually years apart:

• The armour is left floating. The wires are neither fixed nor earthed, so the fault path through the armour does not exist.
• Non-compliance at handover. Wiring rules such as IEC 60364 and BS 7671 require the armour, where it acts as a protective conductor, to be bonded at the gland. Earthing clamps and tape wraps do not achieve this.
• Slow cable damage. Loose wires move with vibration and can pierce the bedding from the inside.

A fourth failure is less visible: water entering an unsealed outdoor entry wicks along the wire cage to the enclosure, which is why wet terminal boxes are often a gland problem. The basic кабельный ввод principles are unchanged; what is added is a clamping and bonding stage.

What Is Inside an Armoured Cable Gland

Most armoured glands use the same stack of parts. Names vary between manufacturers — the brass range calls them armour cone, clamping ring and outer seal — but the function of each part does not.

The seals and the cone touch the cable, so they decide compatibility: a gland matching the thread but not the cone geometry will tighten correctly and still fail.

Armour Type Comes First: SWA, AWA, STA and Braided

Before gland sizes, confirm the armour under the sheath. Strip back the outer sheath and the answer is visible: round wires wound helically, flat tape wrapped circumferentially, or a woven braid. Armour geometry sets the clamping geometry, and glands are not interchangeable between armour types.

Buy against the cable’s construction, not its part number: a SWA gland on an STA cable is a correct thread with the wrong gripping mechanism.

What the Gland Type Letters Actually Mean

The letter codes — BW, CW, E1W — are usually described as indoor and outdoor types, but that is a side effect. They tell you which surfaces the gland seals and which it only grips, which is what matters on a wet or heavy-duty site.

So BW and CW both clamp armour, but only CW seals the outer sheath, and E1W adds a bedding seal. Where a gland must preserve an enclosure’s protection concept, the same logic applies inside the certificate: a CMP-style certified gland is not a CW body with a different label. Body material follows the environment, not the armour: a кабельный ввод из нержавеющей стали suits chloride, offshore and washdown exposure. Markings follow EN 50262 and IEC 62444.

Two Diameters Decide the Gland Size

Most armoured gland selections go wrong here. A gland is sized against two cable diameters: the diameter over the bedding, which the inner seal and inner compression stage act on, and the overall diameter over the outer sheath, which the outer seal grips.

A datasheet lists a bedding range, an overall range and an armour range for every size. Select on overall diameter alone and you can land on a size whose inner seal cannot close on the bedding: the gland threads in, the outer nut tightens, and the assembly still leaks at the inner stage.

Measure both with a caliper on a cut sample rather than a nominal figure. Bedding diameter changes with core count at the same conductor size, so gland size is a cable property before it is a thread property.

Bonding the Armour: Both Ends, and When the Armour Is Not the CPC

Armour is a conductor, not a shield, and that decides how it is bonded. A screen is bonded to manage interference, and single-end bonding can be a legitimate EMC choice, as explained for shielded cable gland installations. Armour carries fault current, so the default is bonding at both ends and at every gland, with an earth tag or banjo under the locknut and a tail to the enclosure earth bar.

Two qualifications belong on the spec sheet:

• Armour as protective conductor is conditional. Where national wiring rules allow this, the permission depends on the armour’s cross-section meeting the fault-current requirement for the circuit. Below that threshold a separate core is required, terminated inside the enclosure rather than on the gland.
• Continuity is an assembly property, not a product property. A certified gland on a loose cone, painted mating faces or a deformed bedding does not deliver the earth path it was tested with. Verify continuity with a low-resistance measurement after tightening.

Motor feeders sit at that intersection: an armoured motor cable needs armour bonding for safety and correct screen termination for drive compatibility, covered in the VFD cable gland guidance.

Common Mistakes and Honest Limits

The recurring problems are selection and assembly errors, not product defects:

• Fitting the shroud after the gland body — on most designs it can only go onto the cable first.
• Over-tightening the clamping ring to stop a leak, which deforms the bedding and destroys the inner seal.
• Using a BW body outdoors and expecting a weatherproof entry; that type does not seal the outer sheath.
• Substituting a fibre indoor washer for a neoprene outdoor washer.
• Treating the earth tag as optional where the armour is the protective conductor.

What an armoured gland will not do matters just as much. It cannot upgrade undersized armour into a compliant protective conductor, cannot correct a damaged bedding, and will not deliver the enclosure’s ingress protection if the entry thread is unsealed — the finished Степень защиты IP is set by the gland, the washer and the enclosure together. Nor does it make a hazardous-area installation compliant unless the gland is certified. Tightening values come from the datasheet, not from feel; where none is published, the criteria are that the cone grips the armour without crushing it, the cable neither rotates nor pulls out, and continuity is verified.

How to Specify an Armoured Cable Gland for a Project

An enquiry carrying these lines can be quoted without clarification. Read them from the datasheet and a cut sample, not the drum label.

Brass armoured glands are normally quoted with a minimum order quantity per size; stainless steel and certified types are quoted at a lower minimum because they are built to order. The figures below are indicative for budgeting.

Indicative FOB Ningbo / Shanghai for nickel-plated brass at 1,000 pcs per size. Stainless steel and certified hazardous-area types are quoted from 300 pcs per size and are confirmed against a live quotation.

The takeaway: an armoured cable gland is a three-function part — grip the armour, bond the armour, seal the sheath — and every question resolves to which the site needs. Confirm the armour construction and both cable diameters first, choose the sealing stage that matches the environment, then match the entry thread to the enclosure. Where a project mixes SWA and STA cables, or indoor and outdoor entries on one board, treat them as separate line items with their own type codes. On certified work, start from a hazardous area selection review rather than a product list.

Часто задаваемые вопросы

What is the difference between an armoured cable gland and a standard cable gland?

A standard gland grips and seals the outer sheath only. An armoured gland adds a clamping stage that holds the steel wire or tape mechanically and bonds it to the enclosure earth.

Can I use a standard gland on SWA cable if the thread and diameter match?

No. The armour would be left unclamped and unearthed, removing both the mechanical retention and the earth path. A matching thread and diameter does not create a way to grip the armour.

Does armoured cable armour have to be earthed at both ends?

Where the armour acts as the circuit protective conductor, the default is bonding at every gland at both ends of the run, because it carries fault current rather than managing interference. Single-end bonding belongs to screens and shields.

How do I know whether I need BW, CW or E1W?

Read the letters as sealing stages. BW clamps armour but does not seal the outer sheath, so it suits dry indoor entries. CW adds an outer sheath seal for outdoor and damp locations. E1W adds an inner seal on the bedding, which exposed and heavy-duty entries usually require.

Are armoured cable glands available in stainless steel?

Yes. The armour clamping geometry is the same, but an SS316L body is specified where chlorides, offshore atmospheres or washdown would attack a plated brass body. Stainless steel types are quoted per size rather than held in stock.