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Guru
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How Square Do Flanges Have to Be?

11/03/2009 9:47 AM

How square do flanges have to be?

3/4" CS XH RF Flanges, Grafoil Gasket.

I have a short spool that, after welding an olet, is 1 degree out of square. I'm looking through the spec. and cannot find a reference to the exact degree of perpendicularity required by ASME.

I look forward to your comments and criticism.

Thanks,

-A-

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#1

Re: How square do flanges have to be?

11/03/2009 10:01 AM

B31.3? see 335.1

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Guru
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#2
In reply to #1

Re: How square do flanges have to be?

11/03/2009 10:05 AM

Wow, thanks. Yeah, I just saw it. I started reading at 335.2

I think I'm going to hide for the rest of the day.

-A-

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Guru

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#3

Re: How square do flanges have to be?

11/03/2009 10:18 AM

For manifolds, short spools etc. we used to bolt the flange in place, then make the weld. As close to a perfect fit as you can get.

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#4
In reply to #2

Re: How square do flanges have to be?

11/03/2009 10:42 AM

also if you were going to reweld/wanted to justify the angularity of welded fittings - see 328.4.2(6)

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Guru
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#5

Re: How Square Do Flanges Have to Be?

11/04/2009 1:46 AM

Good posts which refer to ASME B31.3, also for some details as per code, see LANL_Engineering_Standard_Manual-Process_Piping_Guide_for_ASME_B313, Appendix E-Flanged Connections & Appendix F-Alignment Fit-up Tolerances (Pages 116:127).

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#6

Re: How Square Do Flanges Have to Be?

11/13/2009 5:29 AM

You can very easily draw the flange back to square. grind off the cap on the weld on the appropriate side of the pipe. It is always the weld on the "long or opposite side" of the flange. after you grind it of just re-weld the cap and cool it as fast as you dare, the flange will move back to square when it cools so faster cooling usually draws it more.

I have done this many times to remove stresses from steam turbine piping connections and it works very well. I have used dial indicators to determine where to apply the weld/heat needed to draw flanges back into square and many times just a few inches of re weld or even a dry wash over the weld will draw it enough to do straighten the fittings/pipe will draw the flange back. use common since and figure out which side would cause the flange move in the direction you want. Be careful in cooling the pipe to fast because most company's frown on using water to cool pipe welds these days. Drawing things into square or plumb is more of an art than a learned skill and it takes allot of practice to make flanges draw in a controlled manner and to a certain position.

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Users who posted comments:

-A- (1); Abdel Halim Galala (1); Anonymous Poster (2); passingtongreen (1); pipewelder (1)

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