Tubes and pipes made from titanium, stainless steel, chrome/nickel steels are mostly required to be welded in a non-oxidised environment in order to achieve a metallurgically correct, zero colour weld. Best results are obtained by reducing the volume to be purged, with an inflatable Weld Purging System.
Leading the way in Weld Purging Technology, Huntingdon Fusion Techniques HFT® have developed PurgExtra®, for purging tube and pipe joints from 1 – 24” diameter that provide an extra gas purge hose to speed up the purging process even further.
Additional advantages of this design improvement are that the operator can use the extra purge gas supply for welding reactive metal joints in particular, such as those made from titanium and zirconium. In addition, the extra gas can be used for cooling welded joints faster than normal, where permissible.
Luke Keane, Technical Support for HFT® said: “The PurgExtra® Range complements the PurgElite® Series that has a single purging inlet and is more appropriate for stainless steel only. PurgExtra® however, allows the operator to purge at the recommended rates initially and then, when conditions are correct, to introduce the additional gas at high flow rates. This system is especially valuable for achieving the lower oxygen levels required for welding materials around 20 parts per million.”
When welding joints where interpass temperature control is necessary, PurgExtra® allows extra argon gas into the welding zone, helping to cool the weld zone dramatically. The extra gas also helps to remove the gases that are expelled by the outgassing, which occurs as the metal is being heated. The extra gas flow will prevent these expelled gases from combining with the hot metal and oxidising, which would otherwise cause the metal to discolour and lose its corrosion resistance and possibly introduce defects that would cause loss of joint integrity.
PurgExtra® comprises two inflatable dams connected by a heat resistant, highly flexible gas hose that has the unique IntaCal® gas release system. IntaCal® allows the dams to be inflated correctly and then releases the inert gas to safely purge the space between the dams. The low profile IntaCal® Valve replaces the old fashioned, bulky complicated valves and eliminates the need to make adjustments to flow rates.
The highly flexible spinal hose between the inflatable dams allows the PurgExtra® Systems to be pulled or pushed easily around bends and elbows. In the centre of the spinal hose a strip of RootGlo® material is adhered, allowing the welder to see clearly through the root gap, when the system has reached the correct position in the pipe. RootGlo® can be charged by exposing it to daylight for 10 minutes, after which it will provide up to 24 hours of bright illumination inside the pipe.
The innovative PurgeGate® Valve may be fitted to the PurgExtra® Systems as an accessory, to protect the inflatable dams from bursting due to accidental over pressurisation.
Heat Resistant Covers are also available for PurgExtra®, which fit onto the inflatable dams and allow operation with pre-heated and post-weld heat-treated pipe joints where the temperatures might reach 760°C.
The HFT® Weld Purge Monitors® are used to give precise oxygen values throughout the purging process.