In hazardous areas, selecting the correct cable is only part of ensuring a safe and compliant installation. The performance of explosion proof fittings, including cable glands and sealing accessories, is equally important.

Flexible and armored cables have different structural characteristics and therefore require different explosion protection solutions. Choosing the wrong fitting can compromise sealing performance, grounding continuity, and overall explosion protection integrity.

This article explains the key differences between flexible and armored cables and provides guidance on selecting suitable explosion proof fittings for hazardous area applications.

Flexible and Armored Cables

Flexible Cables

Flexible cables are designed with multi-strand conductors that allow frequent bending and movement. They are commonly used in applications where vibration or equipment movement is expected.

Typical applications include:

• Explosion proof lighting

• Portable equipment

• Motors and pumps

• Instrumentation systems

Flexible cables offer excellent flexibility but provide limited mechanical protection.

Armored Cables

Armored cables incorporate a protective metallic layer, such as steel wire armor (SWA) or steel tape armor (STA), to withstand mechanical impacts and harsh environments.

They are widely used in:

• Oil and gas facilities

• Petrochemical plants

• Offshore platforms

• Industrial process plants

Armored cables provide superior mechanical protection and require special cable glands capable of securing and grounding the armor.

Why Cable Construction Affects Explosion Protection

The cable gland is a critical part of the explosion protection system. Its function extends beyond simply securing the cable.

Proper fittings must provide:

• Environmental sealing

• Mechanical retention

• Ground continuity where required

• Compliance with hazardous area standards

Because flexible and armored cables have different structures, the same cable gland cannot always be used for both cable types.

Explosion Proof Fittings for Flexible Cables

Flexible cables are typically used with compression-type explosion proof cable glands.

1-Gland for flexible cable

Key Selection Considerations

Cable Diameter

The cable gland must match the cable's outer diameter to ensure proper sealing and strain relief.

Cable Movement

Applications involving vibration or repeated movement require fittings that can maintain sealing performance without damaging the cable.

Hazardous Area Classification

The gland should be selected according to the protection concept and area classification, such as Ex d or Ex e installations.

Explosion Proof Fittings for Armored Cables

Armored cables require specialized cable glands designed to secure both the cable sheath and the armor layer.

2-Gland for armored cable

Armor Clamping

A suitable armored cable gland must provide a reliable mechanical connection to the armor while maintaining electrical continuity for grounding purposes.

Double Compression Cable Glands

Double compression cable glands are widely used in hazardous areas because they seal both the inner bedding and the outer cable sheath.

Benefits include improved sealing performance, better mechanical retention, and enhanced environmental protection.

Barrier Glands

For certain flameproof (Ex d) applications, particularly where gas migration is a concern, barrier cable glands may be required.

Barrier glands use a sealing compound to prevent the passage of gases through the cable entry system, providing an additional level of protection.

Flexible Cable vs. Armored Cable Fittings Comparison

Common Selection Mistakes

Using Non-Armored Glands on Armored Cables

One of the most common mistakes is using cable glands designed for non-armored cables on armored cable installations. Armored cable glands are specifically designed to strip, clamp, and secure the armor layer while maintaining proper sealing at the cable entry point.

A standard non-armored gland cannot effectively terminate the armor or provide mechanical retention for the armored layer. As a result, the cable may not be adequately secured, and the sealing performance can be compromised. In hazardous areas, this may affect ingress protection and reduce the overall reliability of the installation.

Ignoring Grounding and Bonding Requirements

For armored cables, the armor often serves as part of the grounding and bonding system. Failure to establish proper electrical continuity between the armor and the equipment enclosure can create safety risks and may lead to non-compliance with applicable installation standards.

When selecting explosion proof fittings for armored cables, engineers should ensure that the gland provides a reliable armor clamping mechanism capable of maintaining long-term grounding continuity.

Using General Industrial Glands in Hazardous Areas

Cable glands used in ordinary industrial environments are not automatically suitable for hazardous locations. Explosion proof installations require cable entry devices that have been tested and certified for the intended protection concept, such as Ex d or Ex e.

Using uncertified glands in hazardous areas may compromise the integrity of the explosion protection system and could result in non-compliance with project specifications and regulatory requirements.

Standards and Certification Requirements

Compliance with recognized international standards is an essential part of explosion proof fitting selection. Engineers should verify that cable glands and associated fittings are designed and tested in accordance with the relevant requirements of the IEC 60079 series, which governs equipment and installations used in explosive atmospheres. These standards define key requirements for general equipment design, flameproof enclosures, increased safety equipment, and hazardous area installation practices.

In addition to meeting technical standards, products should carry appropriate third-party certification for the target market. IECEx certification is widely accepted for international projects, while ATEX certification is required for equipment installed within the European Union. Verifying certification ensures that the selected fitting has been independently assessed for safe use in the intended hazardous environment.

Choosing the Right Explosion Proof Fitting

The correct fitting depends on both the cable type and the installation environment.

For offshore and heavy industrial applications, armored cables with double compression or barrier glands are often preferred due to their superior mechanical protection.

For lighting, instrumentation, and equipment requiring flexibility, properly certified compression glands for flexible cables may provide a more practical solution.

By considering cable construction, hazardous area classification, and certification requirements, engineers can ensure safe and reliable operation throughout the life of the installation.

Conclusion

Selecting explosion proof fittings for flexible and armored cables is a critical aspect of hazardous area design. Because each cable type presents different sealing, grounding, and mechanical challenges, the cable gland should always be selected according to the cable structure and the applicable explosion protection requirements.

Proper selection not only ensures compliance with industry standards but also improves long-term safety and reliability in demanding industrial environments.