Area Classification requirements for pressure transmitter

[bjmpepper]

I have an application where I want to sense headspace pressure in a solvent waste drain line using a Rosemount 3051 mounted directly to a welded flange on the pipe. The environment inside the drain line is class 1 div 1. The environment outside the drain line is unclassified due to sufficient air changes (H5 occupancy). This is a case where the transmitter itself crosses the hazardous/safe boundary. The transmitter head (electronics) is in a safe area, yet it "sees" a class 1 div 1 environment inside the pipe.

Is the transmitter required to be rated for hazardous areas (i.e. explosion proof, intrinsically safe, etc)?
I have called Rosemount about this and the application engineer didn't think so, but it was not a definitive "no".
I could be conservative and just spec an explosionproof version, but the installation would be weird because I would just be connecting up to it using EMT and no seal-offs.
Sure would be nice to fully understand what is required. Any advice would be greatly appreciated!

Thanks,
Bryan Pepper, P.E.
Control Systems Engineer

 

[petersonra]

I think you need a double seal between the process fluid and the unclassified area. see 501.17.

 

[bjmpepper]

I have previously researched process sealing, and I tend to agree with your statement. And if the instrument is spec'd such that it meets ANSI/ISA 12.27.01 (Single or Double Seal internal to the device), then a process seal in the conduit entering the instrument housing is no longer required. My take, anyway. Thank you for responding.
Bryan