High strength steel joints must be pre-heated before welding and they require a post weld heat treatment. Weld joints of this nature are often purged of oxygen and welded in an inert atmosphere to reduce the risk of ‘sugaring’ – an imperfection that could allow metal pieces to break off inside pipework and cause damage.
Due to the high temperatures and the length of time that is spent at these high temperatures, most weld purging systems are unsuitable. In response to this, Huntingdon Fusion Techniques (HFT®), has developed HotPurge®, an inflatable pipe purging system for heat treated chrome and high strength stainless steel pipe joints, where the temperatures can be as high as 760ºC (1400ºF) for several hours.
HotPurge includes PurgeGate®, a device that has been designed to prevent over inflation of, and damage to, inflatable dams. No matter how high a user increases the pressure, in order to deliver more gas flow, PurgeGate stops too much pressure being delivered to the inflatable dams, allowing for an increased flow, along with a lower oxygen level or faster cooling of the weld zone.
HotPurge ensures that the purge space remains tightly sealed at all times as the inflatable dams maintain an even seal throughout the weld cycle, regardless of pressure rises or excessive flowrates of argon gas. The large central collar dramatically reduces the space to be purged and makes it easier to reach lower oxygen levels faster than with conventional purging systems.
Each HotPurge system incorporates a central band for easy positioning inside the pipe. This band, known as RootGlo®, illuminates inside the dark pipe, for up to 20 hrs after just 10 min. previous exposure to daylight.
HotPurge systems are manufactured to suit pipe diameters of between 6 - 96 in. (150 - 2440 mm). Both inflatable dams have pull handles securely sewn with high temperature resistant Kevlar thread that will withstand a pulling force of 1000 lbs.
These inflatable pipe purging systems can be used repeatedly for weld purging and will keep the oxygen levels below 100 parts per million throughout the welding cycle. Ultimately, they ensure oxide and coke free welds without the metallurgical imperfections caused by exposure to too much oxygen.
Read the article online at: https://www.worldpipelines.com/product-news/08032017/hft-introduces-its-new-weld-purge-product/