Huntingdon Fusion Techniques® (HFT) new HotPurge® Pipe Purging Systems have been designed and developed for the high temperatures required during a post weld heat treatment (PWFT), which is used to retain the strength of metal, when welding materials such as high-strength stainless steel and chromium-molybdenum (chromoly) steel such as P91.
Temperatures during PWHT might reach as high as 760°C (1,400°F) for many hours, during which time the insides of the pipes need continuous purging. To ensure welds are free from oxidation which could otherwise lead to joint imperfections, they must be welded in an environment free from oxygen that has to be maintained during the lengthy high temperature post weld heat treatment process, Ron Sewell, Chairman for HFT.
The Argweld® Tube and Pipe Purging Systems are positioned inside the pipe with one dam on each side of the joint and inflated with an inert gas supply. Once a system is fully inflated and sealed in a pipe, the inert gas displaces the oxygen from within the weld purging zone ready for pre-heating and welding.
Image courtesy of Huntingdon Fusion Techniques®