Q & A > Question Details
1. On what design basis would a vendor recommend pilot operated safety valves in a refinery? In our MSQU unit, they are used in RGC and Make-up gas compressor whereas in HDT unit they are used in H.P. separator and Stripper.
2. How are they different from normal spring type PSV?
 
Answers
30/06/2012 A: Lionel SHEIKBOUDHOU, Sara, lionel.sheikboudhou@gmail.com
I recommend you to read the article referred in the following link:
http://www.linkedin.com/groups/Useful-Manufacturer-Manual-4276141.S.104816234?qid=663fd1a9-09c1-42c0-88d5-f582ddb7aacc&trk=group_most_popular_guest-0-b-ttl&goback=%2Egmp_4276141
29/06/2012 A: keith bowers, B and B Consulting, kebowers47@gmail.com
Pilot operated PSVs are used when the margin between normal operating pressure and the design relieving pressure is typically less than 5% of the relieving pressure. A 'pilot operated' PSV will have less tendency to 'simmer' or 'seep' as sealing force remains high all the way to relieving pressure. Then the 'pilot' valve opens, dumping the closing pressure on the main valve and allowing it to rapidly open. When when pressure has dropped sufficiently, the pilot valve closes, and the sealing pressure on the main valve is restored' to to full value. These valves are also not likely chatter or cycle rapidly due to inertial pressure drops in the piping inlet to the PSV.