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Weld Purging with Preheat

Huntingdon Fusion Techniques HFT’s HotPurge minimizes the potential for cracking when welding the high-strength steel pipes used in power generation projects. The inflatable purging system is reusable.

Posted: November 10, 2020

When positioned in the pipe and inflated with an inert gas supply, Huntingdon Fusion Techniques HFT’s HotPurge displaces oxygen from within the weld purging zone.

In the power generation and nuclear industry, low- and medium-alloy steels such as SA 213 T91 and SA 335 P91 are chosen for their high strength but are prone to cracking during welding. Preheating and post-heating minimizes that potential.

To meet the requirements of inert gas purging when temperatures exceed 392ºF (200ºC), purge systems capable of withstanding such high temperatures for lengthy periods are necessary.

Huntingdon Fusion Techniques HFT’s HotPurge is an inflatable purging system for high-strength steel pipe joints where pre- and post-weld temperatures of up to 572ºF (300ºC) for lengthy periods. The inflatable seals at each end of the system are made from flexible but thermally resistant materials, and the central collar is also temperature-resistant.

Manufactured in sizes 6 inches to 88 inches (150 mm to 2,235 mm), the system can be used repeatedly to keep oxygen levels below 100 parts per million (ppm) throughout the welding cycle, ensuring oxidation-free welds free of  imperfections caused by rapid heating and cooling.

Each system comes with a weld purge monitor connection for monitoring oxygen levels; a PurgeGate for preventing overinflation of dams; and RootGlo, a central band that illuminates the inside of a pipe for 20 hours.

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