×
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

ASME B31.3 Piping

ASME B31.3 Piping

ASME B31.3 Piping

(OP)
Hi,
Does ASME B31.3 allows to weld STD. 90 deg.elbow (Matl.-P8) to Slipon flange (SORF)-(Matl.-P8)?
Prompt reply will be highly appreciated!
Thanks in Advance!
BPVN

RE: ASME B31.3 Piping

BPVN,
      What you suggest is not a recommended combination. A bend welded to a weld neck flange is a better option.

RE: ASME B31.3 Piping

BPVN,
1. The Code (ASME B31.3) does not state that you cannot weld a Slip-On flange to a 90 degree Elbow.

2. In my work history over more than 45 years I did it with no ill effects.   

RE: ASME B31.3 Piping

Well pennpiper I bow to your experience but in my working life of 37 years I have never seen it done on this side of the pond because it is a very poor detail design since the flange is sat on the bend radius. The normal detail to use is a weld neck directly onto the bend - much better. I have heard that pipe-fitters like to use a SORF directly on a bend though.  

RE: ASME B31.3 Piping

Pennpiper's suggestion in the original thread on the subject is to use a "long tangent" elbow in this case, which would work just fine.  Just fine, that is, if you can GET such an animal from your piping supplier, and can ensure that it will be used in the correct location by whoever is doing the fitting.  We tend to purge our pipe specs (and our pipe design software's fitting catalogs) of unusual fittings, as they're always a problem to source when we need them.  I'd rather do an extra weld here and there than be waiting 6 weeks for odd components to arrive.

An ordinary long-radius elbow when inserted the proper distance into even 150# SO flanges gives you a very ugly and asymmetrical fillet weld between the hub of the SO and the OD of the elbow.  It's a real mess when you go 300# or higher.  The problem is even worse on the branch of a tee.  You're going to be welding both front and back fillets on the SO, the front fillet is no problem and in category D piping you are permitted to weld only one of the two fillets.  The practice of welding only one of the two welds on a SO is prohibited in normal fluid service in B31.3, so it stands to reason that both welds need to be sound and symmetrical when they're required.  

We prohibit the practice on code piping purely on the basis that it looks bad, and we always do both welds on a SO, even for category D.

We prohibit the insertion of a fitting directly into a socket-welding flange entirely.  In that case, I think there's sufficient justification to call that a bad practice from a strength and durability perspective rather than just on the basis of appearance.

As to whether there's a specific code prohibition against either practice, I've never seen one but that doesn't mean it isn't in there somewhere.  I'll leave it to the people who have B31.3 tatooed to the back of their eyelids to answer the real question posed by the OP.  

RE: ASME B31.3 Piping

moltenmetal,
            You expanded my concern eloquently.

Regards

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