Where there is a final weld joint to be purged in a critical pipework fabrication or pipeline with no available exit for purging dams, the welders can sometimes use water-soluble dams to isolate the weld and introduce argon gas through the root gap.
With such critical joints the preparation has to be 100% effective, so the choice between water-soluble paper and water-soluble plastic film must be considered carefully.
Traditionally, paper has been the material of choice, however with specifications becoming tighter all the time, it is now becoming necessary to consider the water content of paper, which is relatively high.
Where the ambient air has a humidity level, the paper and the tape which fixes it to the pipe wall absorbs even more water and is reported to fall away from the joint, causing loss of purge and an expensive cut-out and re-weld. Placing water content in the form of paper is not conducive to such critical welds.
The Weld Purge Film® option contains hundreds of times less water than paper does and it has the big advantage of being really tough and pressure resistance to the gas flows in a pipeline, so with the super water soluble adhesive, the dams will not fall away.
For those welders using water soluble dams, it is possible to build a barrier of three paper dams in line with each other, giving a little extra protection to the weld, however, if one dam falls away because of the pressure and humidity, then this is no guarantee that all three won't.
Weld Purge Film ® and Super Weld Purge Adhesive ® material makes dams which produce an impenetrable purge barrier but which can easily be washed away when hydrostatically testing the pipe or just by normal wash out, dissolving away completely without leaving any fibres to clog up filters or other sensitive parts in a system.
The technical advantages of using Weld Purge Film ® instead of other materials include:
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