×
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

Relief capacity conversion

Relief capacity conversion

Relief capacity conversion

(OP)
I am looking to size a PRV for a propane cylinder and have run into a snag that my simple mind can't seem to get past.  The NFPA code calculation gives an answer in lb/hr but the relief valves are certified in SCFM of free air.  I can get to SCFM of propane without issue but how does one compare propane to air?

Thank you for any insight.

Jason

RE: Relief capacity conversion

SCFM GAS = [(lb/hr)/(4.5*SpecGrav)]

RE: Relief capacity conversion

ASME Section VIII, Division 1, Appendix 11 explains how to perform capacity conversions for pressure safety valves.  If you don't have the ASME code you can find an excerpt in the Crosby Engineering Handbook...
www.tycovalves-na.com/ld/CROMC-0296-US.pdf

Also, don't overlook contacting a local valve supplier.  I'm sure they would be happy to assist.

RE: Relief capacity conversion

I use the following

SCFM (air)= (flow x 13.36)/(SG x (1/SG)^.5)

where

flow= flow rate of propane in lb/minute
and SG= specific gravity of propane

RE: Relief capacity conversion

density of gas = density of air x specific gravity of gas

RE: Relief capacity conversion

If it's a PRV I'd go with the method in Appendix 11, since it's what the vendors will have to go by to certify the capacity of the valve (provided it's an ASME UV valve).

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