TPi May 2018

products & developments

Bright, oxide-free welds Tubes and pipes made from titanium, stainless steel and chrome/nickel steels are mostly required to be welded in a non- oxidised environment in order to achieve a metallurgically correct, zero-colour weld. The volume to be purged can be reduced by using an inflatable weld purging system. Huntingdon Fusion Techniques (HFT) has developed PurgExtra ® , for purging tube and pipe joints from 1" to 24" diameter, that provides an extra gas purge hose to further accelerate the purging process. Additional advantages of the design 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. The extra gas can also be used for cooling welded joints faster than normal, where permissible. Luke Keane, technical support for HFT, commented, “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 inter-pass temperature control is necessary, PurgExtra allows extra argon gas into the welding zone, helping to cool the weld zone. 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, flexible gas hose with the 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 bulky, complicated valves and eliminates the need to make adjustments to flow rates. The flexible spinal hose between the inflatable dams allows the PurgExtra systems to be easily pulled or pushed around bends and elbows. In the centre of the spinal hose, a strip of RootGlo ® material allows 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 ten minutes, after which it will provide up to 24 hours of illumination inside the pipe. The PurgeGate valve may be fitted to the PurgExtra systems as an accessory, to protect the inflatable dams

PurgExtra inflatable weld purging system from HFT

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. HFT Weld Purge Monitors ® are used to give precise oxygen

values throughout the purging process. Huntingdon Fusion Techniques – UK

hft@huntingdonfusion.com www.huntingdonfusion.com

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May 2018 TUBE PRODUCTS INTERNATIONAL