B31.3 Pipe Repair - Additonal Length

[DLind2005]

I have a customer requesting to add to the length of pipe on a pipe structure, consisting of a 6" Sch. 40 pipe and two weld neck flanges welded to each end, for a piping system that we have already constructed. The 6" Sch. 40 pipe needs to grow by 1-7/8". The customer asked us to add the additional length by splicing the current pipe and welding an additional pipe to make the length, having an additional seam within the pipe. Is there a limit on the length the adder piece needs to be? Or can I just add the additional 1-7/8" length to the existing pipe? The pipe complies to B31.3.

Thanks!

 

[StoneCold]

Why don't you cut out a foot long piece and add back a 13 7/8 inch piece? That's what I would do.

Regards
StoneCold

 

[racookpe1978]

Thickness of a "standard" 6 inch diameter 150 lb (not "schedule 40" but commonly used with sch 40 pipe) is 1.0 thick, 11 inch diameter with 8 bolt holes at 9.50 BCD. I am assuming this is the designation of your existing flanges.

A 6 inch dia 600 lb flange is 14.0 diameter with a 12 inch dia BCD drilled for 12 bolts. But - The 6 inch dia 600 lb flange IS 1-7/8 (1.875) thick.

Clearly, you cannot just substitute the higher-rated flange.

But - Don't bother welding up a new pipe and flange.

Machine (from compatible material standards to a 6 inch 150 lb flange!) a double-sided, double raised-faced, "blank" that is 1.875 (minus the second gasket thickness!) thick with a 6.062 hole through the center. Bolt it in place between the two flanges with extra long studs.

Design it and designate it for QA and registration purposes in the P&ID as an orifice/spacer plate with a full-sized bore.

 

[uaepiping]

StoneCold,
I would do the same!