Explosion proof recepticals

Not open for further replies.


New member
I work for a foreign chemical manufacturer as an operations consultant. I have no electircal background. But, as a chemical operator in the USA, I worked with the Killark hazard duty explosion proof recepticals, the kind with the "sleeve" that the plug is inserted into and turned 45 deg. to energize the plug. It is my understanding that the sleeve is for more than just keeping the receptical dry and dust free. Am I wrong? I was under the impression that it is also to support the plug with the cams on the plug secured into the sleeve. Also an old timer a long time ago said something about it being a flash suppressor in case of a spark.

The reason for my question is: The locals here use the Killark receptical and Appleton plugs resulting in a not to good of fit. They don't seem to be totally compatable with each other. So after struggling with the plugs the plant operators just take the sleeves off and plug in the power. Today I found a power plug body (casting) was cracked and the wiring was visible in the gap of the crack. Now I have to explain to these people why it is important not to tamper with the recepticles. The plug body appeared to have been bumped. It was not very stable in the recepticle so I think the sleeve is for support and protection as much as anything.

Can anybody on this planet answer this for me before these guys blow my old hide away?
Dennis Dash


Senior Member
NEC 505.17

Yes the seal is important. If it doesn't seal you do not have an expolsion proof application and could cause arc exposure etc. They must be compatable to provide adequate protection.


Staff member
Mission Viejo, CA
Professional Electrical Engineer

I'm sorry I missed your original post. You definitely have a serious problem.

What is happening is a good example of why we have various “Divisions” or “Zones” for hazardous locations. You are most likely dealing with a Division 2 (or Zone 2) location. In this classification, the “fuel” part of the “fire triangle” (fuel-air-ignition source) is usually missing.

Installations for this area generally deal with items that may be ignition sources under normal operating conditions. (Division 1 also considers items that may be ignition sources under abnormal conditions - since "fuel" is usally present)

The “twist” feature of the receptacles is necessary to prevent the receptacle from creating an arc when disconnecting it.

In the US, the plugs and receptacles are required to be third party certified that they “fit” so that the situation you describe is avoided.

While the probability is fairly low in a Division 2 (or Zone 2) location for an individual event to create a fire, over time an eventual fire or explosion approaches near certainty if you allow the practice you described to continue.
Last edited:


Senior Member
Get buy in from management, then cut the Appletons off the cord and toss them in the garbage. Force the situation.
Not open for further replies.