Clad Pipe PWHT

[bmoorthy]

Material: Carbon Steel + Inconel 625 Clad
pipe 12" schedule 160 [323.85 OD x 33.32mm thk](Cladded -Weld overlayed inside all over),fittings and flanges are to be girth welded at site.

Internal Clad weld is Er NiCr mo 3 3mm thick.

Now i have to weld the Girth seams.

Code is ANSI/ASME B 31.3.

After welding the Girth seam fully with Er Ni Cr mo3 + E NiCr Mo 3 is it necessary to perform PWHT?

Reason for the question:
1)The table in 31.3 gives P number and F Number and PWHT temp and Soaking Time.

2)After Corrosion resistant overlay one does not require PWHT so long as corrosion resistant overlay is done with pre heat.If i choose to overlay the edges by pre heating then i make the edge (that is Buttering) and then weld the Butt joints, do i still need PWHT? (subjecting all procedures qualified one to one)

 

[metengr]

Yes, for ASME B31.1 PWHT is basically required because the nominal thickness of the P-No1 base material exceeds 25mm.

You do have an alternative approach. If you refer to Section 331.2.2 titled Exceptions to Basic Requirements" one can use less stringent requirements such as an elevated preheat to make this girth weld PROVIDED you can establish adequacy of this method to the satisfaction of the owner.

 

[metengr]

The above should be revised from B31.1 to B31.3.