Chrome Moly Fillet Welds 3

[Seeker88]

Hi folks,
Just finished manufacturing a pressure vessel in Chrome Moly material including PWHT. Prior to hydro the client wants to add a welded earthing boss to the foot of the vessel i.e. not the pressure envelope.

Would I be ok to preheat the area of welding and the boss then weld as per my wps with slow cooling under a thermal blanket without having to do a PWHT on the whole vessel? My instincts tell me the weld is external, small in size (5mm fillet) and not going to see service fluids. The weld procedure for the fillets has already seen a 100 percent pass rate on all other welds under radiography.

Any help would be greatly appreciated.

Many thanks

Brian

 

[metengr]

What is the code of construction? If the welding is done before the hydrostatic test, follow the code requirements for PWHT in the code of construction.

 

Internal or external makes no difference if you are welding directly on pressure boundary. The construction code will define where the PB ends. There do exist potential avenues for what you want to do, but you must always follow Code rules, both the construction code and Section IX (assuming this is ASME B&PV).
So if (for example) your WPS was qualified with PWHT, it can never be used to make a weld that will not be PWHT. The fact that you have a 100% pass rate tells me you have good welders, but it tells me little about the applicability of a given WPS.
Oh, and always follow metengr's advice.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[Don56]

See OP "i.e. not the pressure envelope."

 

[metengr]

If the foot of the vessel is not a pressure retaining part, you can fillet weld to this foot using a WPS, and perform surface NDT.

 

[r6155]

Earthing lug shall be stainless steel when attached to carbon and low alloy steel parts. When attached to other materials shall be similar to the the material to which attached.
DO NOT PAINT THE LUG.

NDE is visual examination

Regards
r6155