×
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

Why is greater accumulation allowed for fire relief

Why is greater accumulation allowed for fire relief

Why is greater accumulation allowed for fire relief

(OP)
Can anyone explain why 21% accumulation is allowed for fire relief but only 10% for other cases?  I can't see any explanation in API 520.

RE: Why is greater accumulation allowed for fire relief

21% is 10% above 10%.  I think it has to do with the extreme rarity of a relief valve opening during a fire event (which is also rare).

RE: Why is greater accumulation allowed for fire relief

in the 21% accumulation there is more relief load than in the 10% accumulation and it is more safe.  

RE: Why is greater accumulation allowed for fire relief

I have thought about this myself (perhaps its in ASME?) but my expalnation is:

In the fire case the normal protection is deluge. If the deluge is in place then the vessel should get hotter, suffer no damage and see no higher pressure.

If the deluge fails then the vessel will get hotter - and the vessel is considered "lost". The purpose is now to limit escalation should the vessel burst. In this case you can save a buck and buy a smalle PSV because a higher pressure can be accepted when you have to discard the vessel anyway after the fire. No law against using 10% over pressure in the fire case as far as I know though.

Lizking don't think the probability of the event occuring has anything to do with it. If it happens then it should be safe - or you don't need it.

Koshan - don't think your argumentation makes much sense. If you need more capacity why not just buy a larger valve?

Best regards

Morten

RE: Why is greater accumulation allowed for fire relief

(OP)
MortenA,

your explanation seems to make sense and I agree with your response to other suggestions. I would be interested to know if vessels really are scrapped when a PSV sized for fire relief lifts!

Cheers,

Nick

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