• • • SAFETY IN ENGINEERING • • •
PROTECTING PEOPLE, PLANT AND PERFORMANCE: THE CRITICAL ROLE OF CABLE GLANDS IN EXPLOSIVE ENVIRONMENTS
Cable runs in hazardous and potentially explosive locations need to be carefully planned, with every component chosen to meet strict performance and safety requirements
By Lee Frizzell, Technical Director, CMP Products
et despite their critical role, the importance of cable glands and 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.
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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 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.
18 ELECTRICAL ENGINEERING • DECEMBER/JANUARY 2026
electricalengineeringmagazine.co.uk
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