Dynamic elaboration on the Art & Science of Hazardous Area Protection
Conduit or Cable for Ex d or Ex de Enclosures
The term ‘Conduits’ refer to the use of Ex-certified metallic pipes to house the insulated electrical wires for transfer of electrical current.
To use conduits or cables in a certain hazardous location depends mainly on the specifications governing the whole situation and scenario. The rule of thumb is : If the specs being followed are NEC 500 then conduits .. if the specifications belong to the NEC 505 OR IEC 60079 family of documents then CABLES will be the choice.
In principle there are three methods of providing electrical connections:
Cables Systems with indirect and direct entries are specified in IEC complied systems and Conduit systems are only permitted in accordance with NEC 500.
Cable systems are mainly used in countries following IEC code. For this, high-quality cables, armored or unarmored, are laid uncovered. It is only in areas in which mechanical damage could be expected that they are laid in conduits that are open at both ends. (The ends of the conduits may require sealing for the purpose of VERMIN Proofing)
Direct Cable Entry
Indirect Cable Entry
The OPEN CONDUIT SYSTEM
Conduits can be used for Mechanical Protection ONLY. Cables are drawn through the conduits and the ends of the conduits remain open . However some sort of sealing is definitely required to prevent the :-
This system is in contrast to the STANDARD SYSTEM of Conduit Installation (As per NEC 500)
(Example : The cables are connected through cable glands and protected by open conduits )
Another example of OPEN CONDUITS . (Control station is connected through non-metallic Cable Gland and connecting cable is protected through a open conduit. )