We want to weld a One inch dia pipe of A 312TP 321H with ER 347 filler wire. Purging normally is done with Argon. However, in this particular case we would like to use Nitrogen for the back purging. Shielding will be with Argon only. Can pure nitrogen be used for welding of 321H pipe without causing any defects in the weld due to dissolved Nitrogen. ?The service temperature of the weld is 670 degC at a pressure of 450 psi and handles vaporized naphtha.
Any clarification will be highly appreciated.
Rajaram
Sr.Inspection Engineer
IOCL