Chromium/molybdenum/vanadium steels need to be pre-heated prior to welding and also require a post-weld heat-treatment in order to preserve the mechanical properties. These materials can also suffer from loss of elements through oxidation, thus changing alloy balance and affecting mechanical properties. Protection can be provided through the use of specially developed weld purge systems.
Huntingdon Fusion Techniques HFT has developed HotPurge, an inflatable tube and pipe purging system specifically designed for use where the temperatures may reach as high as 572 degrees F.
“Restricting the volume to be purged is always crucial when welding tubes and pipes in order to reduce the volume to be purged,” said Ron Sewell, HFT chairman. “With CMV steels, this is challenging as a pre- and post- weld heat treatment is necessary to prevent cracking. To prevent oxidation, the inside of piping needs to be purged continuously using a specialized pipe weld purging system as conventional purging systems will be unsuitable.”
Manufactured in sizes from 6 to 88 inches (150 to 2,235 mm), HotPurge Systems can be used repeatedly for weld purging and can keep the oxygen levels below 100 parts per million (ppm) throughout the welding cycle, ensuring oxidation-free welds and eliminating metallurgical imperfections caused by rapid heating and cooling.
Once positioned in the pipe and inflated with an inert gas supply, the HotPurge System seals inside the pipe with the inert gas supply displacing the oxygen from within the weld purging zone ready for pre-heating and welding. Each HotPurge System is manufactured with a Weld Purge Monitor connection for viewing the oxygen level throughout the welding process.
Each HotPurge System features PurgeGate, a revolutionary device to prevent over-inflation of, and damage to the inflatable dams. The innovative HotPurge System also incorporates RootGlo, a central band containing photoluminescent materials for easy positioning inside the pipe and that is effective for up to 20 hours.
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