Sealing requirements in Class I Areas

[reynokj60]

In my 35+ years experience I have found that engineers and construction folks (like myself) have placed seals on equipment that are not necessary, because of either misinterpretation of the "Code" or failure to try to understand. (When in doubt, place a seal) The situation that prompts my question is: An Oil and Gas Separator/Heater Skid is rated Class I Division 2 over the entire skid. There are approximately 10 instruments rated at least Class I Division 2 on the skid, along with the J-Box which is NEMA 4X with no arcing devices inside, only terminal strips. The instruments include temperature, pressure and level transmitters which are hermetically sealed from process. Wiring is through ridged conduit and Liquid-tight at the instrument.

My understanding of the code is that if there is no transitioning to/from unclassified or higher classified areas, no sealing is required. The primary cable coming into my NEMA 4X J-Box from the RTU in an Unclassified Area would certainly need to be sealed, but each individual instrument on the skid that goes to the J-Box does not. Is this a correct assumption?

 

[retirede]

When I did process gas compressor instrumentation, every run got a seal unless it was intrinsically safe wiring or hermetically sealed. The seal was to stop flame propagation from a NEMA 7 enclosure in case of an "event".
If a NEMA 4X enclosure is sufficient, I don't think you need any seals.