Class I, Div 1 Motors

[Eric L. Nilson]

Art 501.8 lists four types of rotating machinery that is suitable for Class I, Div 1 locations. The first three types are clear: rated for XP, ventilated and inert gas purged. The fourth type is ambiguous to me. Here is a quote from 501.8: Par (A)(4),

(4) Of a type designed to be submerged in a liquid that is
flammable only when vaporized and mixed with air, or
in a gas or vapor at a pressure greater than atmospheric
and that is flammable only when mixed with air; and
the machine is arranged so to prevent energizing it until
it has been purged with the liquid or gas to exclude air,
and also arranged to automatically de-energize the
equipment when the supply of liquid or gas or vapor
fails or the pressure is reduced to atmospheric.

Can anyone explain what type of motor or installation Par (A)(4) refers to?? Or where it would be used??

Here is the scenario that I'm facing on an existing installation. We have a 5" diameter well casing driven into groundwater, perhaps 20 feet below grade. The groundwater aquifer has a 1" layer of gasoline (Flash Point < 100 dF) floating on the surface. A non XP submersible electric pump is used to depress the water surface. The pump is equipped with "redundant" level switches to de-energize the pump if it becomes uncovered with water.

I'm taking this position that this is a Class I, Div 1 space, below grade, and to a 30 ft circle up to 18" above grade. Also, that the installation does not comply with Art 501.8, despite what Par (A)(4) says. The low level interlock to de-energize the non-XP motor does not comply with Art 501.8. My recommendation was to shut this system down immediately.

 

[don_resqcapt19]

I don't see the the area below the surface of the water as being a classified area. I don't have an issue with the submersible pump in the water, but the level controls may be in a Class I, Division 1 area and I am not sure how would be able to install the boundry seals.

 

[bobgorno]

Interesting.....so the most likely scenario where you would have vapor and no water is the time when your redundant, non-rated low level switches would arc......

It would be difficult to make the switches intrinsically safe and keep the required circuit segregation.


I hope the install is separated from the general public and small animals. Any ignition is likely a short term flash, but enough to scare someone and make a projectile out of the well cover.

 

[don_resqcapt19]

Interesting.....so the most likely scenario where you would have vapor and no water is the time when your redundant, non-rated low level switches would arc......

While I did not acutall say it, I implied that the controls would have to be suitable for a Class I, Division 1 area.

It would be difficult to make the switches intrinsically safe and keep the required circuit segregation.

The don't have to be instrinsically safe, they just have to be suitable for Class I, Division 1.

I hope the install is separated from the general public and small animals. Any ignition is likely a short term flash, but enough to scare someone and make a projectile out of the well cover.

That is a possible problem, but to me, it would not be very likely. I would expect that the area where the pump and controls are located would have vapor levels far above UEL (upper explosive limit) making ignition not possible. The most likely point of ignition would be at the cover area where the gas vapors have mixed with the air to provide a conecntration betweel LEL (lower explosive limit) and UEL.

Mabe a solution would be to use a submersible gas pump...the ones used in many gas stations.