Chrome steel pipe joints, such as those used in the power industry for high pressure, high strength pipework, need to be pre-heated for welding and also require a post weld heat treatment. Equally, some high strength stainless steel weld joints need to undergo similar heat-treating cycles.
Weld joints of this nature need to be purged of oxygen and welded in an inert atmosphere, to prevent the oxidation that would otherwise lead to loss of corrosion resistance and imperfections in the joint metallurgy.
With the high temperatures and length of time at such temperatures, most weld purging systems are unsuitable. However, Huntingdon Fusion Techniques HFT have developed HotPurge Inflatable Pipe Purging System for Heat Treated Chrome and High Strength Stainless Steel Pipe Joints where the temperatures might be as high as 760OC (1,400 OF) for many hours.
Luke Keane, Distributor Support for HFT said: “HotPurge allows the purge to be safely continued for up to 24 hours whilst pre-heating, welding and post weld heat-treating with the purge system remaining in place.”
HotPurge is manufactured as standard with PurgeGate to prevent over inflation of, and damage to the dams. No matter how high the user increases the pressure in order to deliver more gas flow, PurgeGate prevents too much pressure being delivered to the inflatable dams, but allows the increased flow, should it be required, to achieve a lower oxygen level, or for faster cooling of the weld zone.
The purge space remains tightly sealed at all times as the inflatable seals maintain an even seal throughout the weld cycle, irrespective of pressure rises or excessive flow rates of argon gas.
The large central collar dramatically reduces the space to be purged and makes it easier to reach the lower oxygen levels faster than with conventional purging systems. Each HotPurge System incorporates an innovative central band for easy positioning inside the pipe. This band, known as RootGlo will illuminate inside the dark pipe, for up to 20 hours, with only 10 minutes previous exposure to daylight.
HotPurge Systems are manufactured to suit pipe diameters from 6 to 96-in (150 to 2,440mm) and both inflatable dams have pull handles securely sewn with high temperature resistant Kevlar thread that will withstand a pulling force of 1,000lb.
These HotPurge Inflatable Tube and Pipe Purging Systems can be used repeatedly for weld purging and will keep the oxygen levels below 100 parts per million (ppm) throughout the welding cycle, ensuring oxide and coke free welds, without the metallurgical imperfections caused by exposure to too much oxygen.