PWHT & SCC for Killed Carbon Steel

[ben]

Killed carbon steel material in ammonia service is prone to SCC and for that specific reason PWHT is done on all the weld joints.
Can PWHT be waived off by taking some other precaution?
Please share your views on the same.

[ashfaqanwer]

Ben,
Please follow the below link and you would be finding some useful discussions.
http://forums.thepetrostreet.com/viewto ... t=241#p922

[ben]

Thanks.
That was useful link.
Actually, most recently we have encountered a situation where we have waived off PWHT on gaseous ammonia flare line (intermittent service) and to avoid SCC, we have killed one big cause of SCC which is air. We advised to purge the line before taking in service so that there must not be any air.
Just wanted to share comments of other guys.

[mechcolor]

Some PSVs may also be opening up in the flare? Am I right?
And if yes would you always be purging the flare line to avoid any air / oxygen as you would not be knowing as and when any PSV pops up.

[ben]

For that particular scenario, process guys have been informed about this whole requirement in detail.
See what they say.