Producers of explosion-proof electrical equipment are responsible for routine tests, product certification and documentation. They have to guarantee that each device complies with the approved design. After that, the installer will have to consider both normative standards (such as the IEC/EN 60079-14) and what is reported on the user instructions provided by the manufacturer, in particular if there are “special conditions for safe use – (X)”. Our choice of cable glands for “Ex d” equipment is relevant. Cable glands following “Ex d” protection method can be of different types, depending on the their use. Generally, they are divided into two categories:
• for armored cable: used for the armored cable direct entry into explosion-proof enclosures, they can be built for different types of armors;
• for normal cable: used for the non-armored cable entry into explosion-proof enclosures.
The sealing is carried out with a sealing ring directly on the external cable sheath. Each sealing ring is suitable for single cable diameters. Cable glands must be chosen considering the cable diameter. The tightness is ensured by the compression of a rubber gasket that tightens on the external diameter and prevents the flame from spreading elsewhere. Usually the sealing ring is as long as the lamination joint; some cable glands with a shorter sealing ring can be used in enclosures whose internal volumes are limited by the certificate. Min and max diameters of the use of the cable are reported on the sealing rings. It is forbidden to insert more cables into the same cable gland, as well as to increase the sealing ring diameter with insulating tape or similar, in order to make it match with the sealing ring diameter. Cable glands for armored cables have two sealing rings: the front one tightens on the internal diameter and guarantees the explosion proof protection; the rear one tightens on the external diameter and prevents liquids from penetrating into the cable gland, where the armor is sealed by two conic rings guaranteeing the electronic continuity of grounding.
