Welding 12 sch 40 pipe with 12 sch 20 WN flange 3

[ajnabi01]

Hi Everyone..!

Due to mistake of procurement we have 12" 300# Sch20 flanges delivered at site instead of required 12" 300# Sch40 flanges.

Is it permissible to trim the pipe ends for weldability..?

Line conditions are
Oper. Press.: 24.53 Kg/cm2 g
Design Press.: 48 Kg/cm2 g
Oper. Temp.: 45 C
Design Temp.: 87 C

 

[C2it]

Your ID's will always be different, so the flange is out of spec. You would need to carefully consider any local stresses in the stepped weld that would result.

I would dump it, and sack the buyer.

Who would want 300# sch 20 in the first place ??? Sack the supplier too.

 

[TD2K]

Does sch 20 does you the necessary design conditions? 12" sch 20 is only 0.25" thick and it looks like you are pushing CL300 flange limits, take off the CA and I would wonder if sch 20 works.

 

[BigInch]

It would seem that the sch 40 pipe is the mistake. for that design pressure with a 0.5 design factor and A-105 flanges all you need is 0.25 wall.

Verify that and you will be able to counter bore the pipe to match the sch 20, if you are using B31.4 or B31.8 and your design factor is 0.5 or higher. But you can't do it if the Design factor is 0.4

What would you be doing, if you knew that you could not fail?

 

[ajnabi01]

Design Code is ASME B31.3 and calculated minimum wall thickness on above pressure is 8.45mm which corresponds to Sch40.

 

[ajnabi01]

Thanks C2it, TD2k & BigInch for your replies.

I understand Sch40 pipe bore can be trimmed to suit Sch20 flange.
My concern is these flanges are to be installed at pump discharge. Should I take the risk of installing Sch20 flanges or not..??

 

[BigInch]

If you need sch 40 THEN NO YOU CANNOT TRIM THE PIPE!!!!



What would you be doing, if you knew that you could not fail?