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Ex Cable Gland Selection Best Practices: What to Check Beyond Cable Size

Learn how to select Ex cable glands by checking cable construction, dimensions, armour, thread compatibility, certification, sealing
Engineer checking Ex cable gland selection against cable diameter, construction, armour, and technical specifications
Ex cable gland selection requires more than matching cable size. Cable construction, certification, sealing, and equipment compatibility must also be checked.

Selecting a cable gland for an Ex installation involves more than matching a gland to the cable conductor size. Cable construction, actual dimensions, equipment entry, explosion protection concept, sealing arrangement, certification, and installation environment can all affect the correct selection.

A cable gland forms part of the interface between the cable and Ex equipment. An unsuitable gland or incorrectly assembled cable entry can compromise the intended installation requirements, even when the cable and equipment are correctly specified.

This guide explains the practical checks engineers, procurement teams, and installers should perform before approving an Ex cable gland.

1. Why Cable Size Alone Is Not Enough

Conductor cross-section does not fully describe a cable's physical dimensions. Two cables with the same conductor size can have different overall diameters, sheath constructions, bedding dimensions, and armour arrangements.

These differences can affect whether a gland can grip, seal, and accommodate the cable as intended.

Best practice: Use the cable manufacturer's datasheet and the gland manufacturer's selection table. Do not select an Ex cable gland from conductor size alone.

2. Identify the Cable Construction

Before selecting a gland, establish the actual cable construction. Relevant details may include:

  • Armoured or unarmoured construction
  • Number of cores and conductor material
  • Insulation and sheath materials
  • Inner sheath or bedding arrangement
  • Armour type and dimensions, where applicable
  • Overall cable diameter

Armoured cables require particular attention because the gland design may need to accommodate the armour and provide the required mechanical retention and electrical continuity.

Best practice: Obtain the exact cable datasheet before approving the gland. A generic description such as "armoured cable" may not provide enough information for selection.

3. Verify the Actual Cable Dimensions

Use the dimensional information relevant to the selected gland design. Depending on the cable and gland type, this may include:

  • Overall cable diameter
  • Inner sheath or bedding diameter
  • Armour dimensions
  • Dimensions of the cable section accommodated by the gland

Compare these measurements with the manufacturer's specified gland ranges. Do not assume that a gland is suitable simply because the nominal cable size appears in a catalogue description.

Best practice: Confirm that the actual cable dimensions fall within the specified ranges for the exact gland model. Pay particular attention when dimensions are close to the limits.

4. Match the Gland to the Ex Equipment

A gland that fits the cable may still be unsuitable for the equipment entry. Review the complete cable-entry interface, including:

  • Entry thread type and size
  • Available entry space and mounting depth
  • Enclosure material and entry arrangement
  • Applicable Ex protection concept
  • Required sealing and installation arrangements

Best practice: Check the cable, gland, and equipment entry together rather than approving each component independently.

5. Consider the Ex Protection Concept

Different explosion protection concepts can impose different requirements on cable entries. For example, an Ex d flameproof enclosure may have different entry considerations from equipment using another protection concept.

The gland must be suitable for the intended application and consistent with the equipment certification, applicable installation requirements, and manufacturer's instructions.

Best practice: Identify the equipment's complete Ex marking and confirm the permitted cable-entry arrangement before selecting the gland.

6. Distinguish Between Armoured and Unarmoured Cable Glands

Armoured and unarmoured cables may require different gland designs.

For armoured cable, the gland may need to accommodate the armour and provide specified mechanical retention and electrical continuity. For unarmoured cable, the gland arrangement may focus on cable retention, sealing, and protection of the cable at the entry.

The correct selection depends on the cable construction, gland design, equipment requirements, and applicable certification.

Best practice: Do not substitute an armoured-cable gland with an unarmoured type solely because the cable diameter appears compatible.

7. Verify the Sealing Arrangement

The gland's sealing arrangement must be suitable for the actual cable construction and intended application. A matching thread does not, by itself, establish that the cable entry provides the required protection.

Depending on the equipment and protection concept, additional sealing or barrier arrangements may be required. These requirements must be established from the applicable standard, equipment certification, and manufacturer's instructions rather than assumed for every installation.

Best practice: Confirm the required gland type and sealing method before procurement. Follow the manufacturer's instructions for cable preparation and assembly.

8. Confirm Thread Type and Entry Size

Thread compatibility is an important interface check, particularly when equipment and glands are supplied by different manufacturers.

Confirm:

  • Thread type, such as metric or NPT
  • Nominal thread size
  • Equipment entry dimensions
  • Available mounting depth and clearance
  • Required locknuts, adaptors, or other accessories

Do not assume that threads are compatible because their nominal sizes appear similar.

Best practice: Match the gland thread to the actual equipment entry specification. Where an adaptor or reducer is proposed, verify its suitability for the complete certified assembly.

9. Verify the Gland Certification

For an Ex application, verify that the gland's certification and marking are appropriate for the intended use. Review the documentation for relevant information, including:

  • Certificate number and issuing certification body
  • Manufacturer and exact gland model
  • Ex marking and applicable protection concept
  • Equipment group and temperature rating, where applicable
  • Certified ambient temperature range
  • Applicable cable construction or dimensional limitations
  • Special conditions of use

Best practice: Check the certificate and product documentation before procurement. Do not assume that certification for one gland variant automatically covers another variant.

10. Consider the Installation Environment

The gland material and construction must also suit the actual installation environment. Depending on the site, relevant conditions may include:

  • Corrosive atmospheres and salt exposure
  • Moisture and water exposure
  • Ultraviolet exposure for outdoor installations
  • Temperature variation
  • Chemical exposure
  • Mechanical impact or physical damage

Material selection should account for environmental compatibility as well as the applicable equipment and project requirements.

Best practice: Specify the site conditions and verify the gland material, finish, and environmental ratings against them.

11. Include Accessories in the Selection

The complete cable-entry arrangement may require additional components, such as:

  • Locknuts and earth tags
  • Adaptors or reducers
  • Stopping plugs for unused entries
  • Washers or other specified mounting components

Not every installation requires all these accessories. Their suitability depends on the equipment, entry arrangement, and applicable requirements.

Best practice: Identify the complete accessory list and verify that each component is suitable for the intended installation. Do not assume that an accessory is acceptable merely because the main gland is certified.

12. Use the Manufacturer's Selection Table

Gland manufacturers typically publish selection tables showing the cable dimensions, construction types, and application ranges covered by each gland model.

Use the table for the exact product variant rather than relying on a generic product description or an approximate cable-size match.

Where the cable dimensions approach the limits of the specified range, obtain clarification from the manufacturer before approving the selection.

Best practice: Retain the selection table or manufacturer's confirmation with the technical submittal to document the basis of selection.

13. Check the Installation Instructions

Correct gland selection does not guarantee a correct installation. The installer must follow the manufacturer's requirements for cable preparation, assembly sequence, tightening, armour termination, and sealing, as applicable to the specific design.

Incorrect assembly can affect cable retention, sealing, and the intended protection of the cable entry.

Best practice: Include the relevant installation instructions in the approved technical documentation and make them available to the installation team.

Common Ex Cable Gland Selection Mistakes

  • Selecting a gland based only on conductor cross-section.
  • Ignoring the actual cable dimensions and construction.
  • Choosing the wrong gland type for armoured cable.
  • Failing to check compatibility with the equipment's protection concept.
  • Using an incompatible thread or unsuitable adaptor.
  • Assuming the correct thread guarantees adequate sealing.
  • Not verifying the exact gland model and certification.
  • Ignoring special conditions and environmental requirements.
  • Overlooking accessories or installation instructions.

Practical Ex Cable Gland Selection Checklist

Use this checklist during technical evaluation and procurement. Adapt it to the cable type, equipment, installation conditions, and project requirements.

Check What to Verify Status
Cable construction Armoured or unarmoured type and relevant construction details are confirmed. Pass / Fail / N/A
Cable dimensions Actual dimensions fall within the specified gland ranges. Pass / Fail / N/A
Gland type Gland design is suitable for the cable and application. Pass / Fail / N/A
Equipment entry Entry thread, size, clearance, and mounting arrangement are compatible. Pass / Fail / N/A
Ex protection Gland is suitable for the equipment's protection concept and application. Pass / Fail / N/A
Certification Certificate and product marking correspond to the exact gland model. Pass / Fail / N/A
Sealing Sealing arrangement and any required barrier provisions are confirmed. Pass / Fail / N/A
Environment Materials and environmental ratings are suitable for site conditions. Pass / Fail / N/A
Accessories Required accessories and entry closures are identified and suitable. Pass / Fail / N/A
Installation Manufacturer's installation requirements are available and understood. Pass / Fail / N/A
Documentation Selection basis, certification, and product details are traceable. Pass / Fail / N/A

When Should Cable Gland Selection Be Verified?

Verify cable gland selection during engineering and procurement, before materials are ordered and installation begins. This provides time to resolve dimensional, thread, certification, or application issues before they cause delays at site.

For projects involving multiple cable types, prepare a cable gland schedule that links each cable type to its dimensions, equipment entry, selected gland model, and relevant certification.

Conclusion

Ex cable gland selection requires more than matching a gland to the nominal cable size. Cable construction, actual dimensions, equipment entry, protection concept, certification, sealing arrangement, accessories, and site conditions all need to be considered.

Verifying these details before procurement can reduce incorrect selections, installation delays, and certification issues during inspection.

A good selection process should leave a clear technical record explaining why a particular gland is suitable for a particular cable and Ex equipment entry.

Important Note

This article provides practical guidance for Ex cable gland selection. It does not replace applicable IEC standards, equipment certification, manufacturer's instructions, project specifications, or local regulatory requirements.

Final selection must be verified against the actual cable construction, equipment entry, relevant certification, and installation conditions.

Sources

  • IEC 60079-14 — Explosive atmospheres — Part 14: Electrical installation design, selection and erection.
  • IEC 60079-0 — Explosive atmospheres — Part 0: Equipment — General requirements.
  • Applicable cable gland manufacturer's certification, selection tables, and installation documentation.

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