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Improving pipe welding

Published by
World Pipelines,

Huntingdon Fusion Techniques (HFT®) has announced the launch of its new devices for welding stainless, duplex, chrome steels and titanium.

The device is typically used for closure welds, tight bends, T piece joints and dome end connections – where a conventional tandem weld purging system cannot be used. HFT has introduced a range of low cost, single ended Inflatable weld purge dams, available for pipe diameters from 6 to 96 in. (150 - 2440 mm).

Each of the 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. These lightweight systems are easy to inflate and are heat resistant up to 90oC.

The dams are fitted with a dual inflation and purge hose, an additional purge gas hose and an exhaust, which can be connected HFT’s weld purge monitors.

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 is then released into the pipe length through a series of venting exhausts on the dam.

Four pull tags are located around the weld purge dam. Therefore, rope, pull wires or slings can be attached for retrieval of the deflated system.

Ron Sewell, Chairman of HFT, said: “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 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.”

Adapted from press release byAnna Nicklin

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