3 replies to this topic

[WilliamN]

Dear peers,

For combo installation of rupture disc below PSV, API 520 states the space between them shall have a free vent, pressure gauge, trycock or other suitable telltale indicator. Comparing pressure transmitter and pressure switch, Pressure switch is simpler, and cheaper. I want to check with PSV experts in this community if pressure switch meets this API 520 requirement.

 

thanks.

 

WilliamN

[fallah]

William,

 

What API 520 expects is: providing facility of pressure sensing for the space between PSV and upstream RD in order to announce about RD failure following which mentioned space would be pressurized and the process fluid will be in direct contact with the PSV itself. Then a high reliable pressure switch/transmitter can do the job and the reponsibility for reliability is in user's scope...

[Pilesar]

A pressure switch is not a reliable indicator in my opinion. It is not likely to be maintained and can fail in ways that hide the fact it is not working. If cost is an issue, why not use one of the devices you quoted from API: free vent, pressure gauge, trycock, etc? These are all cheaper than a pressure switch or transmitter and are all very reliable if monitored routinely. Pressure transmitters in this service are generally not warranted.

[WilliamN]

Fallah and Pilesar, thanks for sharing.