In-case half of weld cap for butt joint between pipes and flanges connections is removed flush grinded up to the base metal for 6 inch Stainless steel schedule 40(7.11mm thick) to get the proper Flange Parallelism, in re-capping during TIG welding of the joint mentioned does it will affect the root from coking or NOT, if the welder using TIG process did not apply back purging on pipe?
Richman,
In the southern hemisphere we call it tig-washing and it should always be done with backpurge.
It is impossible to say whether the root would coke on a Sch 40 6" weld because we have no idea of the heat input or travel speed.
You may be able to get away with it but it is better not to take chances,
Regards,
Shane
If they are flanged connections and you are worried about the inside of the pipe, rub some solar flux on the backside of the joints?
Some codes allow you to stop back purge when you have deposited 2 layers.
Both for P5, P9, SS, etc...
If a "color free" root is required, you might want to think twice about welding without purge.
3.2
For example in 2inch SS pipe Sch. 40/80(3.91/5.54mm thick) or 3inch SS pipe sch. 40(5.54mm thick) which normally welder deposited 2layers on the joint(butt) connections. Hence, when the welder's removed the weld cap and during re-capping the welders required to do back purging automatically, is that what you want to imply, Sir? I tried to look in B31.3 since this is our reference code here in the project but I can't find specifically states that during re-capping for thinner material same on my example does required back purging.
Thanks so much for all your response
In your case, I would purge during welding.
3.2
Sch. 40 yes, Sch. 80, no. Not quoting code here - just giving an opinion.
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