Application and Classification of Cable Glands

Cables are laid not only along cable routes, where they are neatly laid in cable ducts, boxes or simply lie on shelves. Be sure to have a place for the input and output of the cable.

As a rule, these are switchboards and cabinets, control panels and just intermediate junction boxes, from where cables go to various equipment and machines.

Almost all distribution equipment, in the form of cabinets, consoles and boxes, has thin plastic or metal walls through the holes in which it is necessary to pass the cable.

When laying the cable in such places, there is a possibility of damage to its insulation on sharp metal edges and bending of the cable at the point of entry during operation, which results in a break in the cable and the occurrence of short circuits.

To reduce the risk of cable damage at the entry points, pressure seals, also called glands or cable glands, began to be used. They allow you to securely fix the cable in the switch cabinet or in the final equipment, prevent damage to the insulation and cable fracture, limiting its bending, and can even ensure the tightness of the input.

Main Application and Purpose

Cable glands are used for laying both thick power and thin control cables, and their main purpose is not only to protect the cable from insulation damage, bending and fracture, but also to prevent dirt, dust and moisture from entering the equipment.

Another important purpose of the cable gland is to secure the cable after it has been connected to the equipment. During operation, switchboards or equipment may be subject to more than just shaking and vibrations, which can lead to chafing of the cable at the entry point.

Also, the cable itself may be subject to some impact, for example, it may be hit by a person passing by, which will lead to the cable being pulled out of the equipment.

Reliable fixation of the cable to the equipment case using a pressure seal guarantees the integrity of the contact connections, i.e. the cable will not be pulled out of the terminal. This, in turn, guarantees constant reliable operation of the equipment, eliminates the possibility of a phase cable getting on the equipment case and causing a short circuit.

Design Features

Sealed cable glands are a prefabricated structure and consist of several parts.

Sealed cable entry design:

• clamping and locking nut (acts as a retainer);
• sealant (seals the input);
• toothed clutch (for additional compression of the seal and fixing the cable).

Standard cable glands are installed on the body of cabinets and equipment even before the start of cable installation. The cable is threaded into the cable gland, after which it is finally fixed by tightening the fixing nut.

But there is also a detachable cable gland design, which allows the cable gland to be mounted on an already installed cable. Detachable cable entry consists not only of several parts, but also disassembled into two halves. After assembling the two halves of the pressure seal on the cable, it is tightened with a combined nut and securely fixed.

Types and Classifications of Cable Glands

According to the type of installation, sealed cable glands are divided into cable glands with and without a clamping mechanism.

Material for making pressure seals:

Plastic. Sealed cable glands made of polyamide are widely used due to their low cost. Polyamide is a fairly durable material, does not support combustion, and products made from it perfectly perform their function under the operating conditions.

But when using a plastic pressure seal, there is a possibility of damage during installation. Overtightening may strip the threads or burst the housing.

Metal. Nickel-plated brass or stainless steel can be used as the cable entry metal. Structurally, metal glands are no different from plastic ones, but due to the greater strength of the material, they can be used in explosion-proof equipment and in aggressive chemical environments.

Criteria for Selecting a Pressure Seal

When choosing a cable gland, a number of parameters must be taken into account in order to ensure reliable cable routing:

• Cable entry diameter and seal size. The size, and more specifically the diameter, of the cable gland is selected depending on the diameter of the cable insulation.
• Cable entry material. The material of the pressure seal is selected depending on the operating conditions where it will be used. For domestic use, it is usually plastic; for production, metal is often chosen for greater reliability.
• The type of seal to be installed. Seals are also selected depending on the operating conditions. The silicone sealant does not lose its properties for a long time in the temperature range from -60 to +120°C, the neoprene sealant can withstand much lower temperatures from -60 to +70°C.

• The degree of protection of the pressure seal. Cable glands have different levels of protection against penetration of dust and moisture, which affects its cost. Low-security cable glands prevent dust ingress and protect against water droplets, while high-security cable glands can even withstand submersion under water.

Benefits of Using Cable Glands

• The possibility of pulling out the cable from the electrical installation is excluded, which guarantees reliable contact between the cable and the terminal.
• It prevents dust, moisture and dirt from entering the electrical apparatus, which will ensure long operation and reduce the risk of failure.