Inflatable Weld Purge Dams are available for pipe diameters from 150 mm up to 2,440 mm (photo: HTF)
New devices for welding stainless, duplex, chrome steels and titanium are launched by Huntingdon Fusion Techniques HFT®.
Typically for closure welds, tight bends, T piece joints and dome end connections where a conventional Tandem Weld Purging System cannot be used, a range of low cost, single ended Inflatable Weld Purge Dams are available for pipe diameters from 6 to 96 inches (150 mm up to 2,440 mm).
These lightweight systems are easy to inflate and are heat resistant up to 90° C (194° F).
Ron Sewell, Chairman at Huntingdon Fusion Techniques HFT® says, “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, which is very undesirable to have in the presence of a weld. As these old fashioned, poor quality dams and 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, leading to metallurgical defects.”
Each of these new design HFT® Dams are made of low vapour pressure materials specially selected for optimum weld purging results to provide the lowest quality oxygen reading in the fastest possible time with the minimum use of expensive argon gas.
The 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 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 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 pipe length through a series of venting exhausts on the dam.
Four pull tags are located around the circumference of the Weld Purge Dam, so rope, pull wires or slings can be attached for retrieval of the deflated system, if required.
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.