For closure welds, tight bends, T piece joints, dome end connections and so on, where a conventional Tandem Weld Purging System cannot be used, a range of low cost, single ended Inflatable Weld Purge Dams are available from Huntingdon Fusion Techniques HFT®.

Manufactured for pipe diameters from 6 to 96 inches (150 mm up to 2,440 mm), these lightweight systems are easy to inflate using the purge gas.

Once the Dam is inflated and seals all around the internal circumference of the pipe, the excess inert purge gas spills out and purges the space around the weld joint which then pushes the air out to the open atmosphere.

Each Dam is equipped with a purge/inflation hose (black), an extra purge gas hose (blue) as well as a hose for connecting a Weld Purge Monitor® (red).

The blue hose is suitable for passing extra gas into the weld zone at any time to cool welds to meet interpass specifications, or to provide extra inert gas in the event of titanium, zirconium or special stainless applications needing a guaranteed zero colour weld.

By producing bright shiny welds, there will be no porosity and there will be no loss of corrosion resistance caused by oxidation.

Apart from the benefit of having a metallurgically sound weld, the difficulties of cleaning an oxidised weld are eliminated, saving vast amounts of money in labour and material costs as well as the disposal costs where acids are concerned.

Even today, many companies are still allowing their technicians to spend many hours fabricating dams made of foam, cardboard, adhesive tape, wood and so on. Like paper, these materials contain a high percentage of water and water is very undesirable to have in the presence of a weld.

As these poor materials are warmed by the welding operation, they start to outgas their water vapour, which starts to circulate around the weld joint and combine with the weld pool to cause porosity and oxidation.