The correct use of cable glands

The standard establishes various cable entries into electrical equipment such as: cable installation with Ex cable gland with seal; cable...

The standard establishes various cable entries into electrical equipment such as:

  • cable installation with Ex cable gland with seal;
  • cable installation with sealed Ex cable gland;
  • cable installation with sealing fittings.

We spoke about the cable entry with sealing fittings in the newsletter of last January.

Now we speak about the cable installation with direct entry into ex-proof junction boxes. These Ex "d" cable glands are in accordance with EN 60079-1 standard and must be certified and marked. They can be different depending on the uses for which they are intended.

Usually they are divided into two main categories:

  • with a compression seal
  • “barrier”. 

These categories are then divided according to the cable use in:

  • for armored cable
  • for non-armored cable.

Cable glands are chosen according to the diameter of the cable. Sealing is guaranteed by the compression of a rubber gasket that squeezes on the external diameter of the cable and stops the flame from spreading outside the enclosure.

The gasket is normally as long as the longest part of the lamination joint. Some cable glands with a shorter gasket can be used for enclosures with internal volumes limited by certification. The minimum and maximum diameters of the cable are indicated on the gaskets. It is not possible to pass more than one cable through the same cable gland or increase the diameter of the cable sheath with friction tape or anything else in the attempt to make it match the gasket diameter. Cable glands for armored cables have two gaskets: a front one that holds the internal diameter of the cable and guarantees explosion-proof protection, and a back one that holds the cable sheath and prevents liquids from penetrating the cable gland. This is where the armor is secured by two tapered rings to guarantee electrical continuity of the earth connection.

If you have to dismantle a cable gland for plant maintenance, it is advisable to change the gaskets as they may no longer be reliable. Barrier type cable glands seal the cable with resin inside a sleeve, which is inserted in the cable gland and forms a lamination joint with the inside part of the structure. This means that the cable gland can be dismantled for maintenance and then easily remounted. The only thing to remember is to check that the surface of the fitting is perfect condition. Cable glands of all types must be used in accordance with Standard EN 60079-14 which introduced the below graphic for choose the correct cable gland. 

Publication date: 2010-04-01

Topic: Additional information