Classification of an area

[jtester]

I?ve been asked to design the electrical for a building housing a thermal oxidizing furnace. It is used to suck gasoline vapors from leaking ug storage tanks out of the ground and burn them. This machine is existing and was designed to operate outdoors.
The manufacturer has suggested changes to make it suitable for indoor installation and has mentioned that the inside of the building will be a classified location, but he doesn?t know which one. From the description, it?s a Class I Div 2 location if it?s classified. We are installing many air exchanges, I don?t know how many, and also using a lower explosive limit detector to shut down the furnace. There is little if anything about the machine electrical that?s rated for use in a classified location, the control panel and limit switches are all in NEMA 4 enclosures, the motors are plain vanilla TEFC, etc.
What is the experience of others relating to this type of equipment and classified locations. It seems nearly impossible to put the furnace in a Class I Div 2 location.
Thanks in advance for any thoughts.
Jim T

 

[under8ed]

My understanding of the process would have you staying well separated from the decision of what class it will be. You may be called on for cost or feasibility of one over the other. I recently sat in on one of these meetings for just that reason. Included were the department engineers from production, facilities, and safety. The guest of honor was the insurance carrier specialist who was the one to please. Luckily for us, the area did not require classifying, as the fluids flash point was high enough. The European equipment was going to be costly to adapt. They had even bought a rated enclosure expecting the machine to meet our class 1 div 1.
I do suspect though, that a well ventilated room could be considered safer than outdoors on a dead calm day. The only new requirement may be operations shut down controls tied to loss of air flow.

 

[GoldDigger]

IMHO the effect of ventilation on the whole equation may differ depending on whether the furnace itself (when malfunctioning) is the source of the volatile gasses or whether there is already a potential source leading to the Div 2 classification and the furnace is just acting as a potential ignition source.

 

[jtester]

IMHO the effect of ventilation on the whole equation may differ depending on whether the furnace itself (when malfunctioning) is the source of the volatile gasses or whether there is already a potential source leading to the Div 2 classification and the furnace is just acting as a potential ignition source.

According to the manufacturer, there's a section of piping coming into the machine's intake which, if it leaks while the furnace is running, would potentially let vapors escape into the air. If the machine isn't running then there's no suction in the pipe and no vapors would leak out.
Jim

 

[jtinge]

I would expect to see a classification assessment of the oxidizing furnace installation based on the guidelines of NFPA 497. Once completed, then you could determine what NEC Chapter 5 wiring methods are applicable.