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Join Date: Feb 2011
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Minimum Pipe Length Between Two 90 Degree Elbows

02/08/2011 4:11 PM

10" Chilled Water sch 40... Can anyone tell me where in ASME B31.1 does it speak to the minimum length requirement between two 90 degree elbows?

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Guru
Technical Fields - Technical Writing - New Member Engineering Fields - Piping Design Engineering - New Member

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#1

Re: minimum pipe length between two 90 degree elbows

02/08/2011 4:16 PM

Zero.

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#3
In reply to #1

Re: minimum pipe length between two 90 degree elbows

02/08/2011 6:25 PM

It's welded... where in the standard does it speak about minimum pipe length?

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#2

Re: minimum pipe length between two 90 degree elbows

02/08/2011 4:47 PM

Flanged or welded?

  • If it's welded, then zero.
  • If it's flanged, then the minimum distance will be one bolt's length.
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#4

Re: Minimum Pipe Length Between Two 90 Degree Elbows

02/08/2011 7:02 PM

Our friend PENNPIPER says zero. I think they were talking about welded fittings in another forum.

Here:

Pipelines, Piping and Fluid Mechanics engineering - Necessity of ...

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Participant

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#5
In reply to #4

Re: Minimum Pipe Length Between Two 90 Degree Elbows

02/08/2011 7:52 PM

Thank you PENNPIPER... I've searched through the code and I've had no luck finding any limitations on the issue at hand (minimum pup length). You're input has been helpful.

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#6
In reply to #4

Re: Minimum Pipe Length Between Two 90 Degree Elbows

02/08/2011 7:54 PM

And thank you Lynlynch, for directing traffic.

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Engineering Fields - Piping Design Engineering - New Member Egypt - Member - Member since 02/18/2007

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#7

Re: Minimum Pipe Length Between Two 90 Degree Elbows

02/09/2011 1:37 AM

You can weld fitting-to-fitting without pipe spool. But when it is necessary -as a dimensional requirement- to add a pipe spool, in this case we try to avoid over heating due to closest of weldment, therefore we prefer to make min. length of this this spool to be 4t or 2" which is larger (just practical experience), where t is the higher wall thickness.

See CR4 Thread Direct Welding of Fittings to Flanges (ASME).

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Anonymous Poster
#8

Re: Minimum Pipe Length Between Two 90 Degree Elbows

02/09/2011 11:30 AM

I LIKE ALL ANSWERS.

ZERO = WELD FIT UP (ROOT GAP).

WE DESIGNERS ARE TOUGHT, FITTING MAKEUP IS PREFERED

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Anonymous Poster
#9

Re: Minimum Pipe Length Between Two 90 Degree Elbows

02/09/2011 3:30 PM

If the pipe legnth between the elbows is less than the distance between the fittings you could inadvertantly create an atmospheric vent.

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