Armoured cable glands clamp the metal armour (SWA, wire braid, aluminium strip, or steel tape) and bond it to earth, while unarmoured glands only seal the outer sheath and provide strain relief on the cable jacket [S1][S2]. The two families are not interchangeable: fitting an unarmoured gland to a steel-wire-armoured cable leaves the armour unterminated, which violates the mechanical-continuity requirement of BS 6121 [S3][S5].
Cable diameters commonly supported by industrial glands span 1-75 mm across the five-component body (sealing nut, locknut, washer, body, seal) [S2]. A typical double-compression brass gland for unarmoured cable, design code CGW per IEC 60529, is rated IP66 over an operating range of -30 °C to +100 °C with neoprene seals and thread options E.T., NPT, METRIC and PG [S4].
Where the Two Families Diverge in Construction
An armoured cable gland carries an additional armour cone and clamping ring inside the body, components that bite into the metal armour layer to provide mechanical retention and a low-impedance earth path [S1][S2][S4]. Unarmoured cable glands drop those internal armour-clamping parts and substitute an inner seal plus outer seal that compress directly onto the cable jacket, which is why the unarmoured body is shorter and lighter for the same cable OD [S1][S3].
The diameter calculation is also different: for unarmoured cable the only dimension that matters is the outer jacket OD, but for armoured cable you must size for the inner bedding diameter, the armour thickness (single wire, pliable wire, braid, aluminium strip, or double steel tape), and the outer sheath OD [S3][S5][S8]. Skipping the armour OD check is the most common field error and results in either a gland that will not close or one that strips the armour without clamping it.
BS 6121 Type Codes and Suffix Letters
BS 6121 partitions the population into Type A (unarmoured) and Types B, C, D, E (armoured), with letter suffixes appended to identify the armour style: W for single wire armour, T for pliable wire armour, X for wire braid armour, Y for aluminium strip armour, and Z for double steel tape armour [S3][S5]. Type A itself splits into A1 (basic jacket seal), A2 (IP68 moisture seal), A3 and A4 (with electrical bonding for the inner jacket) [S3][S5].
Type B is a brass indoor single-wire-armour gland, Type C adds an IP68 seal for outdoor use on armoured or braided cable, Type D adds an inner-sheath seal to Type B for higher environmental exposure, and Type E carries both inner and outer IP68 seals for fully waterproof outdoor armoured terminations [S5]. A representative Type E gland specified for hazardous areas must also provide flameproof barrier sealing, so the type letter alone is not the full certification picture for Zone 1 / Zone 2 installations [S6].
Material, Thread, and Ingress Ratings
Common gland body materials are brass (often electro-nickel plated), stainless steel, mild steel, and aluminium, with plating options of chrome, tin, or zinc; polyamide (nylon) is the standard plastic body for light-duty and indoor runs [S3][S4]. Seal materials are typically neoprene rubber for -30 °C to +100 °C service, with silicone or EPDM specified for higher temperatures or chemical exposure [S4].
Thread formats cover five systems: metric (most common worldwide), PG (Panzer Gewinde, the traditional German standard), NPT (National Pipe Thread, North America), BSP (British Standard Pipe, UK and parts of Asia), and ET (electrical thread, common in Indian and Middle Eastern specifications) [S3][S4]. A double-compression CGW gland, for example, lists 19 sizes from 3/8 inch (10 mm) up to 4 inch (100 mm) entry, with ET threads as the headline option and 25.00 mm standard entry-thread length across the range [S4].
Ingress ratings to watch on the data sheet: IP66 for jet-spray and dust-tight service (the CGW level above), IP67 for temporary immersion, and IP68 for continuous submersion at a stated depth and duration that the manufacturer must publish [S3][S4][S5]. For EMC protection in panels and data centres, specify a gland that bonds the cable screen 360° to the body, since a standard plastic or unarmoured brass gland does not provide an EMI screen termination [S2][S3].
Use-Case Mapping and Decision Matrix
For unarmoured applications such as telecom racks, control-panel internal wiring, lighting circuits, and indoor cable tray drops, specify a Type A1 or A2 nylon or brass gland sized to the jacket OD only [S3][S5]. When the cable runs through a cable gland entry into a waterproof enclosure or outdoor junction box, step up to an A2 with IP68 and a neoprene seal; this configuration is the workhorse of the building-services and light-industrial stock [S3][S4].
For armoured power distribution on power cable runs to motors, generators, and switchgear in oil and gas, mining, railway, and chemical plants, choose Type B (indoor), Type C (outdoor), or Type E (outdoor with full IP68 inner-and-outer seal) matched to the armour suffix: W for SWA, X for braid, Y for aluminium strip, Z for double steel tape [S3][S5]. In hazardous areas the gland must additionally carry the appropriate Ex d or Ex e certification, and pairing it with cable tray entries requires matching the gland’s earthing tag to the tray’s bonding conductor [S1][S6].
Material selection: brass (Ni-plated) for general industrial, stainless steel (typically 316) for marine and chemical exposure, aluminium for weight-sensitive enclosures, and polyamide only for dry, low-mechanical-risk indoor zones [S2][S3][S4]. The cable wire OD must always sit inside the gland’s stated clamping range; for the CGW series the 1.1/4 inch (32 mm) entry takes a 22-27 mm crimping range, so over-sizing the gland loses both the IP rating and the strain-relief function [S4].
Common Spec Mistakes and Constraints
Mis-specifying a Type A gland on SWA cable is the single most frequent procurement error, because the body physically clamps the outer sheath while leaving the steel wire armour floating, which destroys the armour’s earth-bonding function and the mechanical termination [S1][S3][S5]. The reverse error, using a Type C armoured gland on a plain PVC-sheathed control cable, usually forces the armour cone to bite into the jacket and either cracks the sheath or prevents the gland from reaching its torque-sealed IP rating [S4][S8].
For paired conductors inside a single jacket, an unarmoured gland still needs a separate inner and outer seal (the double-compression pattern) to maintain IP66 on a flexible cable; single-seal Type A1 glands are restricted to fixed, low-flex installations [S4]. Hazardous-area glands must additionally meet the appropriate IEC 60079 series requirements for the zone, and a standard industrial Type C or E without Ex marking cannot be substituted on a Zone 1 enclosure even when the mechanical fit looks correct [S6].
For analogue signal and control cable entries on instrumentation panels, EMC-type glands that bond the overall screen are the only option that preserves the signal integrity, since a standard brass unarmoured gland neither grips the screen nor provides a low-impedance path to the panel earth [S2][S3]. Gland packing compatibility should also be checked on stuffing-box glands for high-temperature or pressure-cycling service, because rubber seals rated to 100 °C will fail prematurely if the service exceeds the published limit [S4][S6].
What to Track Before You Buy
Confirm three numbers on the data sheet before ordering: the cable’s overall OD (or the inner-bedding and armour OD for armoured versions), the entry thread on the enclosure, and the gland’s IP rating with the matching test depth/duration for IP68 [S3][S4]. For hazardous sites, pin the Ex marking (Ex d IIC, Ex e II, Ex tD) and the ambient temperature range to the certificate, not to the catalogue blurb [S6].
On the supply side, watch the entry-thread standard (metric, NPT, BSP, ET, PG) for regional stock differences, and verify that the gland’s gland packing seal compound is rated for the cable’s actual conductor insulation, since PVC, XLPE, and silicone-insulated cables have different upper-temperature limits that the seal must accommodate [S3][S4][S6].
This topic is covered further in ASTM C578 Type IV vs Type VII XPS: ICC-ES Compliance and Spec Selection.