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

Equivalent Flange Pressure Method

Equivalent Flange Pressure Method

Equivalent Flange Pressure Method

I understand the equivalent pressure method to be a conservative method for evaluating tendency of a pipe flange to leak, and particularly when using the temperature/pressure ratings lookup as the threshold.

That said, for a scenario in which I have a class 250 flanged valve mated with a class 300 pipe flange, is it appropriate to use the Class 250 pressure/temperature ratings using this method? This sets the allowable flange pressure much lower than class 300, despite being the same size.


RE: Equivalent Flange Pressure Method

ASME class 250 is for cast iron flanges.

They will be substantially lower than pressure /temperature rating than a class 300 which is a steel flange. You always rate to the lowest flange rating.

I'm not sure what an equivalent pressure method is tbh. Can you define this?

If your class 250 flange is indeed cast iron, make sure that your mating flange if it is steel is a FF Flat face or has the raised face machined off it otherwise you could very easily break your cast iron flange.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: Equivalent Flange Pressure Method

I found this link for Crane valves, and I suspect all manufacture's will have the same ratings. You should - of course - verify this for yourself, for whatever make of valve you have/


The table on page 5 shows that for up to 12", their 250 CI valves are rated for 250 PSIG at 450*F.

250 cast iron flanges have a 1/16" raised face, while the Class 150's have a flat face. You should machine the raised face off any mating Class 150 steel flange, and use a full-face gasket.

RE: Equivalent Flange Pressure Method

Forgot to say the design code is ASME B 16.1 for class 250 flanges.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: Equivalent Flange Pressure Method

I have had good results calculating required gasket preload out of the Garlock Gasket Calculator..

The Gasket Calculator will work with any gasket suppliers material, except spiral gaskets, which will not work with flat faced flanges.

If you want no leaks, make sure the flanges are parallel.

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