The use of water soluble film for pipe purging

When stainless steel pipes and tubes, hereafter referred to only as pipes, (and some made of other materials such as chrome moly carbon steel, copper nickel, titanium, etc.) are welded together or to fittings, it is desirable to purge the oxygen out of the inside of the material near the weld zone to prevent it from reacting with the hot metal and causing coking, porosity, uneven penetration and so on.