For closure welds, tight bends, T piece joints and dome end connections, a range of low cost, single ended weld purging dams are available from Huntingdon Fusion Techniques HFT.
Manufactured from low vapour pressure materials, weld purging dams are used when a conventional tandem weld purging system cannot be used.
Ron Sewell, chairman at Huntingdon Fusion Techniques HFT,said: “Even today, many companies are still allowing their technicians to spend time fabricating dams made of foam, cardboard, adhesive tape, wood and so on. Like paper, these materials contain a high percentage of moisture, which is undesirable to have in the presence of a weld.
“As these poor quality 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.”
Weld purge dams are fitted with a dual inflation and purge hose, an additional purge gas hose and an exhaust which can be connected to one of the HFT’s weld purge monitors.
The additional purge gas hose is suitable for introducing extra purge gas into the weld zone at any time to cool welds to meet interpass temperature specifications, or to provide more inert gas in the event of titanium, zirconium or special stainless applications needing a guaranteed zero colour weld.
Once the Dam is inflated using the purge gas 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. The air (oxygen) is then released out and into the open through a series of venting exhausts on the dam.
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