rigid conduits explosion proof?

[BobB]

In Oz there are regulations for different classes of explosion proof. For example if working around wheat dust the junction boxes are of a type where ventilation is possible and the lid extends quite a long way into the junction box but there is a clearance or gap between the two. If there is an explosion in the junction box the long gap between the junction box and the lid will extinguish the flame. These are normally precisely machined cast iron and made to the standards. In most situations screwed, galvanised conduit is suitable in these situations. You really need to check the standards in your country and check what is suitable according to the standards for your application.

 

[GlenGineer]

In the United States we have several codes that would apply:
The National Fire Prevention Association (NFPA)
The National Electric Code (NEC) (Now part of NFPA)
Occupational Safety and Health Administration (OSHA)

Each of these organizations has some input in how things are done in hazardous locations. OSHA is concerned about electrical safety. NFPA is concerned about fire protection including equipment electrical design. I have a powder painting system that has a NFPA required flame detector that automatically shuts off the flow of powder.

The NEC has about 30 pages dedicated to this subject. In short the NEC divides their Hazardous Location regulation into 3 catagories. Class I deals with flammable liquids and gases. Class II deals with explosive dust. Class III deals with flammable and explosive fibers. So the number 1 question is what kind of hazard do you have? For all classes you must use threaded conduit (either Rigid Metal Conduit or IMC). Non-Metal Rigid conduit is allowable in certain situations. For Class I all the fittings need to comply to Class I standards. Flexible conduit is allowed but the fittings need to meet a certain standard. Any boxes must be sealed to meet those standards. Any conduit that enters boxes where there is power being switched must have seals in it to stop explosive gasses and liquids from entering the panel.

Class II and Class III are less stringent. Boxes must be dust proof. I did not see a mention of seals in the conduit. Flexible conduit is allowable so long as they have liquid or dust tight connections. MC cable is also permitted with the correct fittings. Boxes must be dust proof. Cables could also be used if you use the correct fittings going to devices and boxes.

The question of how to do it brings to mind something from the news recently a vet (animal doctor) from the Republic of Texas lost his license for giving free advice to people on line. They require vets to actually see the animals they treat.

There are so many unknowns involved with the question of how to do it that I can't comment. Without actually seeing the application or seeing drawings it would be very difficult.