Weld Purging closure welds can be challenging, especially when using a tandem inflatable system to reduce the volume being purged. Often, the system becomes irretrievable and therefore other weld purging methods have to be used, to avoid unwanted products in the pipe.
The innovative Weld Purge Dams from Huntingdon Fusion Techniques HFT® help to avoid some problems faced by closing welds, T piece joints and dome end connections where a conventional Tandem Weld Purging System cannot be used. The single ended dams are ideal for welding stainless, duplex, chrome steels and titanium joints.
The single ended Inflatable Weld Purge Dams, available for pipe diameters from 6 to 88 inches (150 mm up to 2,235 mm) are made of low vapour pressure materials specially selected for optimum weld purging results to provide the lowest oxygen reading in the fastest possible time with the minimum use of expensive argon gas.
Ron Sewell, Chairman at Huntingdon Fusion Techniques HFT® said: “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.”
The 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 our 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.
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, as 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.
Now there is no more reason to put welds at risk by using apparently cheaper materials, when for a very low cost, Argweld® Inflatable Weld Purge Dams can be purchased instead!