Class 1, Div 2 switch in Class 1, Div 1 Area

[prchick1984]

I was doing an audit of my plant and found several limit switches in our plant are Class 1, Div 2 but the electrical classification has the plant as Class 1, Div 1 for ethyl acetate. Are these switches okay to use in our plant or should they really be Class 1, Div 1?

 

[moltenmetal]

If the area classification is Cl1 Div 1, devices in that area classification MUST be certified for Cl1 Div 1.

Div 2 devices are permitted to be nonincendive, which is OK for an area which is normally NOT hazardous (div 2).

Div 1 areas should be thought of as the interior of a gasoline tank in a car, i.e. with the headspace filled with air. If a source of ignition is present, ever, there WILL be a fire or explosion with a high probability. Accordingly, switches in Div 1 areas must be either intrinsically safe or protected by an explosion proof housing with poured seal, by hermetic sealing (i.e. with glass), by oil immersion etc. The approved methods of protection are all listed in the appropriate standards.

Many devices are listed as approved for Div 2 by virtue of being nonincendive, but are also built inside an explosion proof housing certified for Div 1. The only difference then is whether or not you need to pour a seal. Approval drawings will come with wiring/installation drawings suitable for each area classification which MUST be followed for the approval to be valid.

 

[zappedagain]

Check the control drawing for that installation (if there is one). As mm said, there might be additional protection in place allowing them to be used, otherwise they are not safe.

Z