Allen Bradley Operators

Theorectically an intrinsically safe circuit will need all its associated apparatus to “limit the energy” in-order to maintain it’s certification. The reason I asked this is because Allen Bradley’s operators are Ex ‘d’ (explosion proof) and is part of an I.S. loop. I want the operators to be housed in a Ex ‘e’ junction box rather than a Ex ‘d.’ If housed in a Ex ‘d’ box, I won’t have to worry about the I.S. loop losing its integrity, however Ex ‘d’ boxes are not cost effective.


I believe this can be achieve with the Ex ‘e’ boxes, even though I will lose my integrity. Since the AB’s operator contacts are sealed, no process gas can leak into it.

Equipment housed within an Ex d enclosure is categorised as "Flameproof" and is NOT intrinsically safe. These are two entirely different approaches to system design for hazardous areas. Similarly Ex e "Improved safety" equipment is yet another approach. You may well be able to find what you want in an Ex e enclosure but you will have to check the certification for each piece of equipment. There is nothing to stop you from running Ex d and IS equipment side by side provided that any interconnections do not breach the rules for either of the technologies used.

Andybr

Equipment such as pushbuttons are "simple devices" and any simple device can be used with a suitable IS barrier in any sort of enclosure, as long as the requirements for IS circuits are met. Such as the seperation of circuits.