Ex-proof installation advice req'd 1

[bklauba]

We are supplying a captive coal-burning power plant ex-proof rotary electric vibrators as material flow aids. Their req'ts are not well defined as to their need for ex-proof equipment; the impression we rec'd was that the ex-proof req'ts were being explored so they would have the option to burn hi-energy-yield coal, which is more hazardous in nature.

The supplier of the ex-prf electric vibrators supplies a "wiring kit for hazardous locations" that includes SEOW-A cable, which is: "SEOW-A Extra hard service cord. Thermoplastic elastomer, oil resistant (TPE) construction Jacket. 600 volt, weather resistant for outdoor use."

Is this cable considered ex-proof, or should we instead use flexible ex-proof conduit + cable (and then, what type of cable)??

Either way, the SEOW-A cable or flex conduit will enter an ex-prf JB, which is fed thru rigid, so I think they are AOK from the ex-prf JB back. But the bridge 'tween the JB and the vibrator, which must have some flexibility is the issue.

Thanks in advance for your responses.

BK

 

[rbalex]

The cable type itself (SEOW) is not explosion-proof; nevertheless it is acceptable for the application you havce described. There a several additional requirements for flexible connections listed in NEC (2005 Ed) Section 501.140. You probably won't have too many problems if this is offered as a "kit" by the system supplier.

 

[resqcapt19]

If we are talking about coal, shouldn't we be talking about dust ignition proof equipment and not explosionproof equipment? Some explosionproof equipment is not suitable for use in Class II areas because of excessive operating temperature.
Don

 

[bklauba]

resqcapt19, thanks for that point. The electric vibrators involved run at modest temperatures, outside temperature rarely getting above 150 F. The real concern has been not the device, which is rated Ex-proof, but the conduit feeding it, which must be flexible.

What we have decided to do is leave this up to customer, giving the choice of the "wiring kit for hazardous locations" which contains the SEOW-A cable, or Cross-Hinds ex-proof flex conduit, thru which would be fed cable, likely the SEOW-A or SOOW of sufficient ampacity. Our recommendation is the latter; anthing short of that is not rated ex-proof. The vibes pull less than 2 amps, and the cable will likely be AWG 12, unless someone has a better idea.

BK

 

[EEJaime]

The critical points of any Hazardous atmosphere electrical installation are the transition points. Connector to cable, cable to box, connector to equipment, box to conduit and conduit through hazardous area boundary. As long as the cable to box transition is with an explosion/ignition proof connection, such as the Crouse-Hinds kit. Or as long as the conduit into the box is gas/dust tight, you should be fine. Remember that when the conduit passes through the boundary of the hazardous area, you must have seals in the conduit to prevent the travel of explosive gas or igniteable dust into the non rated side or into switchgear.