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


Steam Piping Union to Flange

Steam Piping Union to Flange

Steam Piping Union to Flange

I am looking to replace 3/4" and 1" schedule 80 and schedule 40, in both sizes, and wanted to know if there is a definite standard as to when you can and cannot use unions on certain size pipe. Steam pressure can range from 60 - 100 psi.

RE: Steam Piping Union to Flange

What does the owner's engineer say? I really doubt that you'll find an American National standard on this. I avoid unions since they can vary a bit from manufacturer to manufacturer and so you will have to replace both sides if an issue occurs. But for small bore low pressure I would probably accept 'em. Are the other fittings threaded or welded? If you're already using SW elbows etc then I'd push for SW flanges.


RE: Steam Piping Union to Flange

In the Steam service you site (60 -100psi), I would recommend:

 - Socket-weld fittings (w/ SW unions for break-out) in all sizes 2" (DN 50) and smaller

 - Butt-weld fittings (w/ Weld-neck Flanges for break-out) in all sizes 3" (DN 80) and larger.

RE: Steam Piping Union to Flange

I second pennpiper's suggestion.....

The piping joints and size ranges are consistent with the power piping codes.

You ask:

"if there is a definite standard as to when you can and cannot use unions on certain size pipe"

Yes there is..... its in the  ASME B31.1 and.3 codes and the defined list of acceptable standards for piping fittings and joints


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!


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