Barrier Cable Gland — Certified Protection for Explosive Atmospheres

When electrical installations extend into environments where a single spark can trigger a catastrophic explosion, standard cable management hardware simply isn’t enough. A barrier cable gland addresses this challenge with a fundamentally different approach to cable entry, one that seals not just around the cable’s outer jacket, but deep within it, around every individual conductor core. Barrier cable glands prevent migration of gases through cable into electrical enclosure.

This compound-filled sealing architecture makes barrier cable glands the cornerstone of safe, code-compliant wiring in Zone 1 and Zone 2 hazardous areas, protecting flameproof (Ex d) enclosures from gas ingress across the oil & gas, chemical, pharmaceutical, and mining industries worldwide.

How a Barrier Cable Gland Works, The Core Difference

A conventional cable gland clamps around the outer sheath of a cable and stops there. It secures the cable mechanically and offers basic ingress protection, but it does nothing to block gases or flames from travelling along the interstices, the tiny voids between cable cores that run the full length of the cable.

A barrier cable gland eliminates this pathway entirely. Once installed, a two-part compound or epoxy resin is injected or packed into a dedicated sealing chamber within the gland body. This material flows into every void between the conductors and cures to form a solid, gas-impermeable plug. Should a flammable atmosphere exist outside the enclosure, it simply has no route through.

This distinction makes the barrier cable gland non-negotiable in applications involving Ex d (flameproof) certified equipment, where the enclosure itself must contain and cool any internal ignition before gases can escape to the outside atmosphere.

Construction & Materials

Barrier cable glands are purpose-built for demanding environments. Key construction elements include:

Body Material

Nickel-plated brass is the standard choice for most industrial installations, offering excellent machinability, corrosion resistance, and low-sparking properties. Marine, offshore, and highly corrosive environments call for 316 stainless steel bodies, which resist chloride attack and mechanical abrasion where brass would degrade over time.

Sealing Compound

Two primary systems are in use, putty-based two-part compounds that are hand-packed and shaped, and injectable liquid resins that self-level to eliminate voids. Both achieve the gas-tight barrier required under IEC 60079-1 when correctly applied.

Armour Termination

Versions are available for both armoured cables (SWA, wire braid, steel tape) and unarmoured cables, with appropriate clamping arrangements for each cable construction type.

Thread Forms

Available with metric (M-thread), NPT, PG, and G (BSP) thread options for compatibility with global enclosure standards.

Barrier Cable Gland vs. Standard Cable Gland, A Direct Comparison

Where Barrier Cable Glands Are Required, Industries & Applications

Any location classified as a hazardous area under IEC 60079-10 (Zone 1 or Zone 2) and served by Ex d rated equipment will typically require barrier cable glands. Primary sectors include:

• Oil & gas upstream: Wellhead platforms, drilling rigs, FPSO vessels, onshore processing terminals
• Downstream refining & petrochemicals: Distillation units, reactor vessels, pump houses, storage tank farms
• Mining & mineral extraction: Underground coalface installations, surface crusher buildings, ventilation control rooms
• Pharmaceutical manufacturing: Solvent processing, spray drying, coating suites
• Chemical production: Chlorine, ammonia, hydrogen, and organic solvent handling areas
• Grain, flour & dust-hazard facilities: Silos, milling buildings, packaging halls where combustible dust creates Zone 21/22 risks
• Paint, varnish & adhesive production: High-VOC environments throughout the manufacturing process
• Marine & offshore: Engine rooms, tanker pump rooms, ATEX-zone compressor decks

Applicable Standards & Regulatory Framework

Correct selection of a barrier cable gland requires understanding the standards that govern hazardous area electrical installations:

IEC 60079-1

Defines the construction and testing requirements for flameproof (Ex d) enclosures. It specifies that cable entry devices used with Ex d equipment must themselves hold an Ex Equipment Certificate and must be capable of sealing around individual conductors, a requirement that only barrier-type cable entry devices satisfy.

IEC 60079-14

Covers the design, selection, inspection, and installation of electrical systems in explosive atmospheres. Its cable entry clause directs installers to use barrier glands for cable types that are not compact, round, or filled with non-hygroscopic material. For cables that do not meet those conditions, which is the majority of multi-core instrumentation and power cables, a barrier gland is required.

ATEX Directive 2014/34/EU

The European framework that mandates CE marking and notified body certification for all equipment intended for use in potentially explosive atmospheres. Barrier cable glands sold for European hazardous area use must carry ATEX certification.

IECEx

Provides the equivalent international certification scheme recognised across Asia-Pacific, the Middle East, and Latin America. Many modern barrier glands carry both ATEX and IECEx certification to enable global project deployment without re-certification.

BS 6121-5

The British Standard specifically governing mechanical cable glands, providing additional guidance for barrier gland types used in UK installations.

The 3-Metre Rule, Understanding Modern Selection Requirements

A critical update introduced in the fifth edition of IEC 60079-14 changed how many engineers approach gland selection. Previously, the decision to specify a barrier gland was primarily linked to the hazardous area zone or the IIC gas group. The current edition introduces cable length as the determining variable.

This change has significant implications for engineers working from older specifications or legacy documentation. Any design review using pre-fifth-edition IEC 60079-14 should be revisited against current requirements.

Additionally, installations in IIC gas group environments (hydrogen, acetylene) and enclosures with an internal volume greater than 2 litres retain specific requirements that almost always point toward barrier gland selection.

Installation — Step-by-Step Overview

Barrier cable gland installation demands greater care than standard gland fitting. The sealing compound must be correctly applied to achieve the certified gas-tight performance. A general installation sequence:

1. Cable preparation: Strip the outer sheath to the required depth. For armoured cables, cut armour wires to the appropriate length and dress the cores to avoid nicking insulation.
2. Gland assembly onto cable: Thread all gland components onto the cable in the manufacturer’s specified order before compound is applied.
3. Entry into enclosure: Pass the cable through the enclosure wall and engage the gland body thread. Torque to the manufacturer’s specified value.
4. Core preparation: Spread the individual conductors apart within the barrier chamber to ensure compound can penetrate between each core fully.
5. Compound application: Inject or pack the specified compound into the barrier chamber until all voids are filled and compound is visible at the chamber’s exit face.
6. Compression and cure: Tighten the compression nut to the manufacturer’s specification, which distributes and pressurises the compound. Allow full cure time as specified — do not energise the circuit before cure is complete.
7. Final inspection: Visually inspect for compound voids, check armour and outer sheath clamping is secure, and confirm thread engagement depth meets standard requirements.

⚠️ Important: Barrier cable gland installation must be carried out by a competent person familiar with IEC 60079-14 installation requirements. Incorrect compound filling is the most common cause of installation failures and can void the equipment’s explosion protection certification.

Frequently Asked Questions

What does a barrier cable gland actually seal against?

It seals against the migration of flammable gas or flame along the internal voids within a multi-core cable. Without this seal, gas from a hazardous outside atmosphere could travel through the cable and accumulate inside a flameproof enclosure, making the enclosure’s explosion protection rating irrelevant.

Is a barrier cable gland necessary for every Ex d installation?

For most practical installations involving cable runs over 3 metres and standard multi-core instrumentation or power cables, yes. IEC 60079-14 (current edition) and the cable gland selection criteria within IEC 60079-1 will direct you to a barrier gland for the vast majority of common cable types.

Can barrier cable glands be reused if a cable is replaced?

No. Once the sealing compound has cured, the gland assembly cannot be reused on a new cable. A replacement cable requires a new barrier cable gland and a fresh compound application.

What is the cured compound’s temperature rating?

This varies by manufacturer and compound system. Most commercial barrier gland compounds are rated for continuous operation between -60°C and +120°C. Confirm the compound’s specific temperature classification against the operating environment before specifying.

Are barrier cable glands rated for submersible or buried applications?

Yes. Stainless steel barrier glands with appropriate O-ring sealing on the entry thread can achieve IP68 ratings suitable for buried ducting and wash-down environments. Always confirm the IP rating on the product certificate rather than assuming from the material alone.

Do barrier cable glands work with single-core cables?

Barrier glands are primarily designed for multi-core cables where interstice voids exist between conductors. Single-core cables in Ex d applications typically require a different sealing approach, consult the enclosure manufacturer’s guidance for the correct entry device.

What sealing compound is used in barrier cable glands, and why does it matter?

Barrier cable glands use an epoxy-based two-component compound to create a certified gas-tight seal around individual cable cores. This compound available as a semi-solid putty or liquid pour resin, chemically cures after mixing to permanently fill all interstices between conductors, preventing flammable gases from migrating through the cable into explosion-proof (Ex d) enclosures. The quality of the seal directly determines compliance with IEC 60079-1, ATEX, and IECEx standards, making the correct selection and application of epoxy compound critical for safe installations in Zone 1 and Zone 2 hazardous areas such as oil & gas, chemical, and petrochemical plants.

What is the difference between epoxy putty compound and liquid resin in a barrier cable gland?

Both are two-component epoxy-based systems used to seal barrier cable glands, but they differ significantly in application and reliability. Epoxy putty (clay-based compound) is manually mixed and packed around cable cores, a time-consuming process that requires high installer skill, and risks air voids especially on multi-core cables. Liquid pour resin, by contrast, flows freely between and around individual conductors, self-expels air pockets, and cures in under 40 minutes, delivering a void-free, consistent seal with minimal skill dependency. For critical hazardous area installations, liquid resin is the preferred method as it reduces rework risk and ensures full compliance with IEC 60079-14 installation requirements.

How to Specify a Barrier Cable Gland — Key Parameters

When raising a purchase order or specification document, include these criteria for accurate supply:

Providing these details upfront avoids back-and-forth on technical queries and ensures the correct certified product is supplied first time.

Metalmech is proudly approved by major organizations such as ADNOC, EIL, Petroleum Development Oman, and KPC (Kuwait Petroleum Corporation).