The use of Weld Purge Film® for Pipe Purging
04 Aug 2015
When tubes and pipes of certain materials, such as stainless steel, titanium, copper nickel and zirconium are welded together it is desirable to purge the oxygen out of the inside of the weld zone to prevent it from reacting with the hot metal and causing oxidation, porosity and corrosion.
Some products available include Inflatable Tube and Pipe Purging Systems PurgElite®, QuickPurge® and HotPurge™. These systems require an open end to enable the system to be retrieved after the weld is finished, meaning it is impossible to use one of these tandem system for closing welds.
To overcome this difficulty Huntingdon Fusion Techniques, HFT® has developed and manufactured Argweld® Weld Purge Film® kits, with water soluble materials that can be used for open assemblies and closing welds. The Film produces an impenetrable purge barrier, but which can easily be washed away when hydrostatically testing the pipe or just by normal wash out.
To obtain a quality purge is not easy and it has been customary to fill pipes with expensive argon gas and keep the gas running at what is thought to be a suitable flow rate for an estimated period of time. In today’s climate of ever improving quality control and increasing demands on procedures with traceability, it is inappropriate to use such hit and miss methods to guarantee a satisfactory purge.
It is not desirable to simply pour gas into a pipe assembly in the hope that a good purge and ultimately, a good weld will be achieved. This technique rarely works.
It is so easy to cut a circle of water soluble film and place it a short distance inside each pipe end, before welding, using the Argweld® Super Water Soluble Adhesive™ to ensure a leak tight barrier, keeping the purging volume to the barest minimum.
Argweld® Weld Purge Film® will save operators large costs by minimising gas usage and cutting down dramatically on time taken to make a purge.
After welding, the water soluble film is simply washed away during the standard hydrotest cycle or by simply washing of the pipe interior and dissolved down to molecular level leaving no trace.