A guide to cable glands

09 Nov.,2022

 

unarmored cable

A guide to cable glands

How to choose cable glands

There’s a world of choices out there and unfortunately no one-size-fits-all option. But it does mean that you can custom select a cable gland based on your parameters. And to do that, you first need to consider a range of environmental and application factors.

The role of the environment

It doesn’t matter whether you’re working in aerospace, industrial, marine, power and utility, telecommunications or any other key industry. What’s important is identifying the core application environment of your cable gland. Questions to ask yourself:

  • Are you using it indoors or outdoors?
  • Will it be situated in a safe industrial zone or a hazardous or explosive environment?
  • What’s the temperature and is it constant?
  • Is the surrounding area damp or dusty?
  • Are there any gases or corrosive materials nearby?

Your answers will help determine the cable gland specs and whether it requires a special protective plating or coating.

The purpose of armouring in cables

Different cables demand different types of cable glands. For example, the requirements for an armoured cable, also called steel wired armoured (SWA) are different to those of unarmoured cables. Armoured, or SWA, cables are used on exterior walls or underground.

Type

Characteristics

Application

Armoured Extra layer of protection to prevent damage

This may be a single wire armour, braided armour, pliable wire armour or double steel tape armour Areas where exposed to threat of mechanical damage Unarmoured More basic than armoured

Can have no seal, or have a single outer seal or a double outer seal Fixed installations not exposed to risk of mechanical damage

Does armoured cable need conduit?

Typically, no. They’re armoured for protection. You should use conduit for unarmoured cable, however.

IP-rated cable glands

Cable glands are designed with safety in mind, so they come with an IP rating to ensure you know what you’re getting. The Ingress Protection Marking (IP) rates the glands depending on their design and efficiency throughout different tasks. These ratings often go up to IP68 and IP69K. It’s important to check that any devices placed in explosive atmospheres comply with national or international codes of practice.

Types of cable glands

Below are examples of cable glands:

Spiral cable glands

These types of cable glands provide excellent strain relief to protect against conductor fatigue caused by flexing cables. IP68 rated, resisting dust, dirt and sand, and withstanding submersion in water for 30 minutes.

Straight cable glands – nylon

Rated IP68 for outstanding protection against the elements. Designed for superior sealing and strain relief, these cable glands are rated IP68 for excellent protection against the environment. With an IP68 rating, these are waterproof cable glands.

Click-in cable glands

Convenient mounting and dismounting without the need for tools. Clicks in for a secure, weatherproof seal, preventing twisting, straining and snagging. The ideal pass-through cable gland for enclosures when saving time matters. Made of nylon 6/6 and TPE.

Straight cable glands – brass

Cable gland brass types screen against electromagnetic disturbances, enabling enclosures to perform as intended. This nickel-plated brass gland resists corrosion and is rated IP68.

Cable gland size guide

To determine the right cable gland size for armoured and unarmoured, you need to consider:

  • Cable diameter
  • Construction size
  • Cable material.

For armoured cables, you also need to consider:

  • The diameter of the inner bedding
  • The diameter of the lead covering
  • The short circuit fault rating of the cable armour
  • The type and size of the armour braid

Cable gland material types

Cable gland materials perform differently depending on the application, environment and cable type.

  • Metal cable glands are used in a range of applications, including the chemical industry, technology and areas with high demands on special mechanical and chemical stability. The pros are durability over time, even in wet conditions, and its rigid stability.
  • Plastic cable glands have a wide cable range due to their claw and seal design, which makes them extremely adaptable to a wide range of applications. The pros are resistance to salt water, grease and weak acids, to name a few.

At a glance:

Material

Common applications

Characteristics

Brass cable glands
  • Medical equipment
  • Controlling devices
  • Measuring devices
  • In machinery
  • Corrosion resistance
  • Electrical and thermal conductivity
Nylon cable glands
  • Telecommunications
  • Instrumentation
  • Data cables
  • Electrical power
  • Ideal for use on flexible cables
  • High strain relief
  • Can bear the highest IP rating (IP68)
  • Available in colours for colour coding cables

How to install a cable gland

Cable gland installation depends on the type of gland you’re using, but the basics are the same. You’ll need to follow the relevant codes of practice, your local regulations and the manufacturer’s cable-gland-installation instructions. Installation should only be carried out by a skilled person with experience and knowledge of cable glands.

Note: Take care not to damage loose entry wires.

Getting started

Step 1: Turn off all electrical equipment and disconnect any live wires

Step 2: Make sure your cable gland is compatible with your cables

Step 3: Keep cable glands clear of solvents, chemical substances, and dirt during installation

Installing cable glands

Step 1: Open the cable gland and remove the nut.

Step 2: Peel back the outer sheath of the cable to the same length of the cable gland itself. If there’s an inner metal armour, expose it.

Step 3: Insert the right end of the gland into the cable.

Step 4: Lay the peeled sheath or armour evenly around the gland.

Step 5: Apply the nut, taking care to tighten with a spanner to secure the gland in place.

Extra protection features

Your application or environment may demand the cable gland to possess a specific quality, above and beyond its basic function. That’s where you may consider the following special features:

  • Fire-stop cable gland which can withstand fire propagation through a barrier
  • Explosion-proof cable glands
  • EMI and RFI shielding and associated grounding features to minimise or eliminate electromagnetic or radio frequency interference
  • Romex connections to specifically deal romex cables
  • Wire mesh for additional strain relief
  • Liquid tight cable glands to protect against penetrating oils and waters

Cable gland consideration

There are a few important considerations that fall outside of the categories above. So before you choose a cable gland, also ask yourself:

  • Is the wire hole diameter large enough to house all the cables in the system?
  • Is the cable diameter sufficient?
  • Is the pressure rating high enough for your application needs?
  • Is the mounting hold diameter large enough for my cable gland?
  • Is the depth and size of the gland thread metric or PG?
  • Is there a requirement for stopper plugs to close off any unused cable entries?