×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Pilot PSV Popping far below set pressure

Pilot PSV Popping far below set pressure

Pilot PSV Popping far below set pressure

(OP)
Anyone have experience with Pilot PSVs popping significantly below set pressure? I have some in ethylene service that keep popping and not in the other systems. There appears to be some issue with Ethylene and the pilot mechanism. Any ideas on what could be the failure mechanism or how to investigate this would be appreciated.

RE: Pilot PSV Popping far below set pressure

Focal,

It might the pilot valve being stuck open due to very low temperature conditions; hence the process pressure cannot be kept above the main valve to keep it closed even in low and normal pressure inside the relevant vessel/tank...

RE: Pilot PSV Popping far below set pressure

POSRV's require system pressure to remain tight. The area above the disc called the dome, requires system pressure to keep the main valve closed. Running at below normal operating pressure (anything below 90% of set pressure), will quite often make the main valve seats leak. Then again you have Ethylene service which can be tricky.

Per ISO, only the term Safety Valve is used regardless of application or design.

RE: Pilot PSV Popping far below set pressure

(OP)
Thanks for your replies e43u8 and avalveman. We have believed it to be low ambient temperatures because we had so many pops in the winter months. The summer was fine and we have heat tracing on the pilots now, but there have been pops in the evenings (Again lower temperatures). I can understand why an immediate change in temperature would cause a relief scenario, but when it's such a slow temperature drop over a duration of hours I would assume the pressure/temperature/volume changes in the pilot/dome would be recovered from the process feed before any imbalance the dome would cause an opening. I'm going to inspect the PSVs tomorrow.

RE: Pilot PSV Popping far below set pressure


I am sure you can find a commercial available PSV system with pilot fluid separated from the process fluid. This could perhaps help avoiding unwanted release. Although a high-cost solution this could be economic positive in the long run avoiding extra costs at shut-downs and maintenance.

Example: http://www-eng.lbl.gov/~shuman/NEXT/MATERIALS&...

RE: Pilot PSV Popping far below set pressure

Sounds like you've got a leak somewhere in the pilot mechanism - check if a non flowing type pilot valve helps.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close