×
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

Use of 150# SS Fittings B31.3
2

Use of 150# SS Fittings B31.3

Use of 150# SS Fittings B31.3

(OP)
Hello,

I'm new to B31.3 and am trying to clarify the use of SS threaded pipe fittings.  Can anyone clarify what ASME/ANSI/MSS standard covers the use of 150lb cast stainless steel threaded pipe fittings?

Regards,
Allen

RE: Use of 150# SS Fittings B31.3

Iron threaded fittings would be Class 150.  Steel threaded fittings would be per ASME B16.9, and would be 2000# to 9000#.

RE: Use of 150# SS Fittings B31.3

They're covered by MSS SP-114.

http://www.mss-hq.org/price_list.htm

Good luck using threaded SS pipe and fittings. My experience is that they're notorious leakers.

Donf

RE: Use of 150# SS Fittings B31.3

(OP)
Thank you Donf for the information.  Do you have any knowledge of MSS SP-114 fittings being acceptable for B31.3 normal service?

Allen

RE: Use of 150# SS Fittings B31.3

Leakage with threaded systems is entirely a matter of how good the piping designer and pipefitter are and what kind of sealant system is used.  If an appropriate sealant is used, properly-assembled threaded piping is appropriate for B31.3 normal fluid service up to and including 2"NPS.  

Commonsense on the part of the person selecting the fitting method used for the service is key- that goes for all piping systems, but it goes double when threaded piping is selected.

Clearly, if you have significant vibration, wide/frequent temperature cycling, the tendency for crevice corrosion, or solvents which will affect the sealant chosen, or if minor leakage will result in catastrophe if it ever occurs, you're better off with welded/flanged piping.  You've got to trade those issues off against the (greatly) reduced cost of fabrication and the increased flexibility to future change offered by threaded piping.

Stainless adds a complication not encountered to the same degree with malleable iron fittings and steel pipe:  galling during installation.  Choose the wrong sealant system or install the stainless pipe/threaded fitting combination improperly and you will get leaks because the pipe/fittings gall before they're tightened adequately.  

As to 150# stainless fittings, be careful to ensure that you use the correct design T/P range for these fittings- it's quite limited.  There are both 150# cast and 1000# forged fittings in stainless (with similar dimensions) and they have widely different design T/P ranges.

One area of concern is the lack of mill test reports for 150# fittings.  The best you can get around here is lot certificates of compliance, which may not satisfy inspectors/regulators in some jurisdictions.

RE: Use of 150# SS Fittings B31.3

They are not listed in ASME B31.3 so they would have to be qualified as unlisted components.  Suggest using B16.9 fittings if it is a B31.3 system.

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