Previous in Forum: threads   Next in Forum: centrifugal pump
Close

Comments Format:






Change Mode
Close

Subscribe to Discussion:

CR4 allows you to "subscribe" to a discussion
so that you can be notified of new comments to
the discussion via email.

Close

Rating Vote:







Add Vote
2 comments
Rate Comments: Nested
sv13
Commentator

Join Date: Jun 2009
Location: Between India & Australia
Posts: 71
Good Answers: 3

How PSV Set Off Below Set Pressure

07/17/2009 1:18 AM

My question is regarding a recent incident in our gas turbine plant. During operation one of the main isolating gas valve was inadvertently closed and then opened within a span of 1 min. The GTs continued to operate during that time.

However as soon as the main valve opened again, 2 PSVs (small thermal) located downstream of the pressure control valves (PCV) popped up. During investigation it revealed that the main line gas pressure went down and when the valve suddenly opened there was a spike of pressure almost 3.5 bar/s.

The PCVs that regulate the main line pressure, could not arrest the spike downstream where the spike was 2.7 bar/s. Even though the total pressure in the line remained below the PSV set pressure (95%), the PSV located here popped up and one of the PSV did not reseat at all.

The contractor is claiming that PSVs will pop up if you get up rapid pressure rise within 90% of set pressure. Anyone having more information on this? Thanks

__________________
 Continuous Learning
Register to Reply
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.
betomachine
Power-User
United States - Member - New Member Engineering Fields - Chemical Engineering - New Member

Join Date: Apr 2007
Location: Austin, TX
Posts: 367
Good Answers: 10
#1

Re: How PSV Set Off Below Set Pressure

07/18/2009 9:52 AM

This is certainly possible, there is a good chart in API 520 (maybe 521) that will show you the range of PSV operation. It is right in the front of the standard. How old are the PSVs and what is their condition? As for not re-seating, did the pressure get back down below the blow down pressure? You could check their last test report and see what the lift conditions and re-seat conditions were as well. I'm assuming that you keep such records, of course (and test your PSVs).

To rephrase what happened, the manual valve closed and the PCV went wide open to try and maintain fuel pressure at the GTs, the manual valve was opened and the PCV oscillated a bit getting the line pressure back under control, causing a spike downstream of the PCV? Is that correct?

__________________
 Money doesn't talk, it screams in your face.
Register to Reply
sv13
Commentator

Join Date: Jun 2009
Location: Between India & Australia
Posts: 71
Good Answers: 3
#2
In reply to #1

Re: How PSV Set Off Below Set Pressure

07/19/2009 7:08 PM

The PSVs are very new, just installed a month back. The rapid spike downstream of the PCV took the pressure to 95% of set pressure, and one of the PCV did not close at all, inspite of reducing the pressure much below the blowdown pressure.

__________________
 Continuous Learning
Register to Reply
Register to Reply
Have a Different Question?
2 comments

Previous in Forum: threads   Next in Forum: centrifugal pump

Advertisement

Got Something to Say?
Ask a Question
Start a Discussion

Search this Forum
Mechanical Engineering:
Go

CR4 Sections
Aerospace
BioMech & BioMed
Chemical & Material Science
Civil Engineering
Communications & Electronics
Education and Engineering Careers
Electrical Engineering
General Discussion
Instrumentation
Manufacturing
Mechanical Engineering
New Technologies & Research
Software & Programming
Sustainable Engineering
Transportation

Site Directories
Forum Directory
Blog Directory
User Group Directory
RSS Feeds

CR4 Rules of Conduct
CR4 FAQ
Site Glossary

Who's Online (175 right now)
Show Members
Advertisement