Class 1E to non-safety connection point

[LT1982]

If I have a certain instrument that must be safety related, IE; a pressure transmitter, how far downstream do I need to go with safety related power for it and where is the connection made between safety and non-safety.

If you could reference a standard that covers this that would be very helpful.

thanks

 

[racookpe1978]

Go downstream?

See, the "fluid" safety criteria is set up to maintain fluid system integrity, right? So the "fluid" MUST be "safety related" from source through "last joint" and "last pressure boundary" = the internals of the pressure sensor. But those are considered "upstream" of the sensor in normal US P&ID usage.

"Downstream" of a pressure sensor is the electronics and cables/wires/fiber-optincs => then the "control" network (visual, alarm, trip, computer, display, or whatever. So, any or all of THOSE functions and alarms and displays might be (or might not be) "safety related" depending on what they do and what your plant's backup requrements are.