Direct and indirect entrances into explosion-proof electrical systems

As is well known, the systems are mainly divided into systems with metal protective conduits and cable systems.The various devices require cable entries suitable for the type of protection used.Get more news about Terminal Box Explosion Proof,you can vist our website!

Specifically, now we analyze the type of protection [0] 'Ex d', at most in its composition with the type of protection 'Ex e'. This is limited to explosive atmospheres due to gas and leaving out the 'Ex n' and 'Ex i' methods of protection in this article.

Generally cables enter devices in three ways:

directly via conduit sealing fittings directly through 'Ex d' cable glands, following the selection criteria as per plant engineering standard EN 60079-14 [1] indirectly through the interposition of an increased safety case used as a terminal box. The figure 1 well represents the types of entrance in explosion-proof enclosures and the types of systems. The direct entries The entry through sealing fittings is typical of a system with cables in protective metal conduits (conduit) and, therefore, it is the most traditional system in the areas classified as Zone 1. The conductors passing through the metal pipes are sealed in the sealing fitting and then enter the explosion-proof enclosure.

The entry through the 'Ex d' cable gland is the entry solution made entirely in the 'Ex d' protection system which is most often present in the cable system. Logically, the choice of use between a cable gland with barrier and one with a sealing ring is made in accordance with the selection criteria for cable glands according to the EN-60079-14 plant engineering standard [1].

The indirect entries The third system relates to the connection to the network of those equipment or enclosures that are equipped with an increased safety terminal box. This allows the connection to be made with an 'Ex e' cable gland, that is a certified cable gland equipped with a sealing ring, thus avoiding any on-site sealing operations. Furthermore, since these are 'Ex e' cable glands, it is not necessary to apply the criterion of choice as on 'Ex d' cable glands, which, as far as we talk about it, remains undoubtedly a complex technical evaluation. The indirect entries in 'ex d' equipment It is interesting to note that more and more 'Ex d' explosion-proof devices use an increased safety terminal box for connection to the system [2].

In these devices, the explosion-proof part is separated from the 'Ex e' terminal box by means of special certified wall passages [3].

This in fact makes these devices very versatile, excluding the on-site sealing procedures required with the use of sealing fittings or barrier cable glands.