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!

*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.

Jobs

PSV Set Pressure 10% Above Piping MAP?

PSV Set Pressure 10% Above Piping MAP?

(OP)
Hello,

I seem to remember reading somewhere that PSVs may be set 10% above piping MAP, as ASME B31.1 allows up to 20% overpressure of flanged piping for short durations. Has anyone else read this somewhere or did I just imagine this? Anyone have a code reference on this?

I am interested in raising the PSV set pressure to 10% above the 150# flange rating as the PSV often operates at 95-99% of PSV set pressure.

RE: PSV Set Pressure 10% Above Piping MAP?

For liquid thermal expansion, B31.3 allows the set pressure to be the lesser of the system hydrotest pressure or 120% of the design pressure. (Ref: B31.3 paragraph 322.6.3)

The relieving pressure can be as high as 133% of the piping design pressure, provided you don't exceed the hours limitation (no more than 10 hrs per incident and no more than 100 hrs/yr). (Ref: B31.3 paragraph 302.2.4)

Common question: Is the 33% accumulation allowance (paragraph 302.2.4) applicable to pressure relief events?
Answer: Yes, as long as the allowable hours are not exceeded. This is stated in an ASME B31.3 interpretation (Ref: ASME B31.3 Interpretation: 20-51).



RE: PSV Set Pressure 10% Above Piping MAP?

In most cases, these exceedences are permitted only for rare operating scenarios - even liquid hammer is typically required to be contained within the B31.3 normal design limits.

The fact that this PSV is triggered at MAWP " often " wouldnt permit the justification for this exceedence.

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