PWHT for -43degC in A333 GR6 pipe 1

[paulbrown]

Do you need to PWHT fillet welds in A333 gr6 pipe
for propane duty down to -43degC (-45degF)?

As material has P No.1 pipe does not need PWHT unless thicker than 19mm (3/4") according to B31.3, but I think this might be a bit simplistic due to the low temperature?

 

[sterl]

a333 Employed frequently with Fillet Welds and Socket Weld Fittings at temps Lower than this....Contents would be Ammonia and Carbon Dioxide, and the CO2 would be at a considerably higher pressure than Propane in most cases.

Weld Engineers will tell you there is not such thing as a well designed fillet weld, and PWHT will resolve some of the circumferential residual stresses...Course the reason for using 333 is not the non-dynamic, standing pressure concern but transient pipe conditions, mainly associated with phase change or rapid acceleration of the contents.

PWHT is going to recover some of the original fracture toughness in a localized sense, but the comparison between Charpy testing and pipe rupture or joint degradation mechanisms is not quite a closed loop. These mechanisms have been well studied by the refrigeration, cryogenic and oil pipeline folks, and they reccommend against PWHT for field pipe welds.