TIG root pass on 6 mm 316L pipe — purge or no purge?

Question

We are welding 6 mm 316L pipe for a food line. Some welders say a purge is unnecessary at this thickness. What does the inspection usually require?

Answer

For hygiene service, purge. The root bead oxidises without argon and the oxide is a corrosion initiation site, even if it looks acceptable. At 6 mm you can use a simple soluble purge dam and 8-10 L/min for a few minutes before striking.

TIG root pass on 6 mm 316L pipe — purge or no purge?

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