×
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

PRV vs. Vapor space Riser for Liquid full 2" hexane piping?

PRV vs. Vapor space Riser for Liquid full 2" hexane piping?

PRV vs. Vapor space Riser for Liquid full 2" hexane piping?

(OP)
Our plant utilizes hexane in our processes.  We had an incident with a liquid full 2" line overpressuring due to thermal expansion of the hexane in the blocked in system.  The result was gasket failure at the flange.  

Now I am evaluting a new 2" piping layout that could have liquid full conditions, full sun exposure, blocked in by valving.  One solution is a PRV.  Can we use a stand pipe or riser say 4-6 feet tall with a fixed cap or valve with blind on top ( similar to a high point bleed) as a safety vapor space so as to avoid a true liquid full condition and potential failure.

I am finding little techinal data on such a "riser" vs. PRV.   It is not always suitable to use PRV since we do not have a flare line to dump to in every case.  Any suggestions on how to approach. Calculations for the riser pipe for vapor space seem difficult to find.

RE: PRV vs. Vapor space Riser for Liquid full 2" hexane piping?

How do you want to make sure that the riser pipe is not completely filled with hexane? Do you want to keep a gas pocket inside? That won't really work if the hexane is in motion unless your riser pipe connection is very, very small. An accumulator (bladder type pressure vessel) looks as if it is the solution for your problem. It allows expansion of the hexane and does not need any outlet or drain connection.

RE: PRV vs. Vapor space Riser for Liquid full 2" hexane piping?

First, when your pressure rises, or temperature falls, so the vapor cavities collapse, it could initiate waterhammer, so I'm not sure you really want to encourage vapor spaces to form, or expose an accumulator tank to that possibility either.

Arn't the real solutions a relief valve in the proper locations, adding a vent or drain system, perhaps combined with a higher pressure rating for the system and ensuring that your joints make up properly.   

 

"We have a leadership style that is too directive and doesn't listen sufficiently well. The top of the organisation doesn't listen sufficiently to what the bottom is saying."  Tony Hayward CEO BP
"Being GREEN isn't easy." Kermitfrog http://www.youtube.com/watch?v=hpiIWMWWVco

http://virtualpipeline.spaces.liv

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