Contact US

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.

Students Click Here

Check valve on flare sub headers

Check valve on flare sub headers

Check valve on flare sub headers

I came across a flare header design where check valve is installed on one sub header (size 20 inch).

Is it common to have check valves on flare sub headers? can someone throw more light on this?

Thank you

Raghu N

RE: Check valve on flare sub headers

If this is downstream of a relief device, it may not comply with Code.

Good Luck,

RE: Check valve on flare sub headers

Obstructions of discharge pipe is hazardous because of risk of choked flow (Mach = 1). It is a good industry practice flow area of discharge pipe should be no less than that of discharge fitting of a relief device.

API 520-2-2015
8.3.1. ... the flow area in the outlet isolation valve should be equal to or greater than the outlet area of the PRV ... Check valves shall not be installed in PRD inlet or outlet lines since these devices are normally closed and the check valve can become stuck in the closed position or fail in a manner causing an obstruction in the PRD path.

ISO 4126-9-2008
7.4 The outlet line shall be as short as practicable and have a bore at least as large as the valve outlet.

Guess 1
Separation of subheader and main header due to low pressure or temperature rating of subheader. Check valve prevents backflow of too hot relief gas from main header to subheader.
Guess 2
Prevention of misopening of conventional spring PSV. Check valve prevents rise of pressure in subheader in case of too high pressure of relief in main header.
Guess 3
Prevention of backflow of relief gas to a vessel that breaths to subheader.

Note that any check valve can not guarantee prevention of separation of pressure in pipe segments due to design of sealing element. If backflow of gas to be prevented it is a good industry practice to provide 2 check valves in series having dedicated design of a sealing element e.g. spring-loaded or swing oriented upward.

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! Already a Member? Login


Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Design for Additive Manufacturing (DfAM)
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a part’s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. Download Now

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