BUILDING SAFETY
The critical role of cable glands in explosive environments
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Lee Frizzell, CMP Products’ technical director, talks to BSEE about cable runs and their importance in hazardous environments and how correct specification can be achieved every time
able runs in hazardous and potentially explosive locations need to be carefully planned, with every component chosen to meet strict performance
and safety requirements. Yet despite their critical role, the importance of cable glands – the devices that seal and protect cable entries in these high- risk environments – is still frequently underestimated.
“The importance of cable glands simply can’t be underestimated – especially in hazardous and potentially explosive installation locations. Put simply, without the correct specification there’s the very real risk of gas migration and the increased danger that products aren’t able to prevent or contain an explosion. Of course, all aspects of cable runs in these kinds of installations demand exceptional attention to detail; with every component – from cables to junction boxes and everything in between – carefully specified to ensure they remain operational in times of system stress and prevent ignition of surrounding explosive atmospheres.
And while cable glands may seem a minor part of the specification challenge, it’s vital that they aren’t underestimated. They are, after all, the primary sealing point for cable entry and exit points and on top of that provide mechanical retention, environmental protection, earth continuity and, in explosive atmospheres, they help to prevent or contain an explosion.
Explosive atmosphere installations are classified into various types depending on the type of hazard; typically flammable gases, vapours or combustible dusts. In these situations, cable glands serve five essential functions:
• Explosion protection: Flameproof (Ex d) glands prevent flames produced by an explosion inside an enclosure from transmitting into the external atmosphere. While Increased Safety (Ex e) glands terminate and seal the cable into the enclosure, which itself contains certified components that cannot spark or reach temperatures high enough to ignite an explosive atmosphere
• Gas migration prevention: Correctly specified or installed glands will prevent explosive gases travelling along cable runs into neighbouring equipment, causing explosion risks
• Environmental sealing: Glands must block ingress of moisture, dust and corrosive elements. This is particularly important in offshore, marine or chemical processing plants
• Mechanical stability: Pull-out resistance, or strain relief prevents cable damage and preserves safety over the equipment’s lifespan.
• Earth continuity: Any armour or metallic screen in the cable is terminated and grounded inside the cable gland
If not correctly specified, then even a high- quality cable installation and enclosure can become dangerously compromised. So, what steps need to be taken to ensure correct and safe specification? There are several key steps that need to be taken; starting with understanding the environment in which the system will operate. This is classified by different zones – with Zones 0, 1 and 2 relating to explosive gas; and Zones 20, 21 and 22 concerning explosive dust. These zones are then broken down to confirm the explosive atmosphere and subgroup and from there the type of enclosure protection concept needed can be identified. As mentioned, Ex d
18 BUILDING SERVICES & ENVIRONMENTAL ENGINEER FEBRUARY 2026
is flameproof, while Ex e is increased safety – no sparks or heat sources. There are also Ex i, Ex nR and Ex t options. The correct type of cable gland is then chosen to complement the enclosure. Problems arise if the wrong kind of gland is used – for example, fitting an Ex e gland on an Ex d enclosure is extremely dangerous.
The cable type then needs to be matched to the appropriate gland. For example, armoured cables require glands that can correctly terminate steel wire armour (SWA), steel tape armour (STA) or aluminium wire armour (AWA). The material of the cable gland itself, most commonly brass, nickel- plated brass, stainless steel or aluminium must also be selected appropriately. Attention must also be paid to the cable’s inner bedding diameter, overall diameter, any armour or braid thickness and the applicable tolerances. Any uncertainty in selection risks compromising the cable or cable gland’s performance and overall system integrity. The inner construction of the cable also needs
careful consideration. For example, multicore cables increase the risk of gas migration and flame transmission through any gaps; to mitigate this risk and maintain Ex d integrity, a barrier type gland is required to seal directly around the cable inner cores. Barrier glands are mandatory for Ex d with unfilled multicore cables (per EN/ IEC 60079-14). A correctly specified barrier gland will provide the peace of mind that gas will be prevented from travelling between the inner cores into neighbouring equipment or enclosures. This is essential in installations where explosive gases (e.g. hydrogen, acetylene, methane, ethylene) are present and pressure differentials exist. As with every element of any cable installation, cable glands need to comply with industry wide standards. For projects following UKEX/ATEX or IECEx requirements, the key is the EN/IEC 60079 series and every explosive
atmosphere cable gland we sell complies with the strict requirements of these internationally recognised standards.
On top of this, glands should carry certification markings that match the explosive atmosphere classification of the system; with temperature ratings that meet or exceed site requirements; gland materials match environmental and chemical exposure profiles; and Ingress Protection (IP) ratings align with enclosure and site specifications. Any deviation can make the entire installation non-compliant.
And the specification challenge doesn’t end there:
• Corrosion resistance requirements instruct the choice of product material and coating or plating
• Thread type mismatch is a frequent cause of installation error. Enclosure and gland entry threads need to match in type, length and taper. For Ex d, minimum thread engagement must also meet EN/ IEC 60079-1
And, of course, and it should go without saying – the manufacturer’s installation instructions need to be followed precisely. Cable glands may be small, but their importance in hazardous and explosive atmospheres is mighty. They protect personnel and infrastructure by maintaining the integrity of the system. Incorrect gland specification or installation increases the risk of a catastrophic explosion, gas migration, or moisture ingress. By following a structured approach— beginning with proper explosive atmosphere classification and matching gland design to cable type, through to confirming certification, assessing environmental conditions and ensuring correct thread engagement—engineers and installers can achieve the right cable gland specification every time.”
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