Large diameter stainless steel pipes can be purged of air quickly and easily – with reported savings of up to 90% in purge gas requirements – using a British-made weld purging system.

The Argweld® Quick Purge from Huntingdon Fusion Techniques will typically purge a 36” diameter pipe to pipe joint to below 0.1% oxygen in less than ten minutes, with faster purging for smaller pipes, says the company.

Savings in time and purge gas consumption are achieved by reducing the volume purged.

Two Argon expanding dams are positioned inside the pipe or vessel, restricting the length of the purged section to approximately just 3” on each side of the weld. At the same time, a sleeve joining the dams occupies most of the pipe’s inside diameter, so that only the much reduced space between the outer surface of the sleeve and the inner surface of the pipe needs to be purged.

Inert gas supply
When the Argweld® Quick Purge has been positioned inside the pipe, by using pull tags, it is charged by the inert gas supply so that each end dam forms a leak tight seal.
Once the dams are fully expanded, the pressure opens a valve to allow the inert gas to enter the space between the sleeve and the pipe to quickly displace the air.

Welding can begin as soon as the oxygen level is low enough. The flow of inert gas is maintained throughout the welding operation, to purge any oxygen or water vapour released by the increasing temperature, and is continued until the completed weld has cooled to below oxidation temperature. The purge gas supply is then cut off and the system deflates to allow its removal from the pipe.