There are a number of applications where the attachment of hot tap fittings to in-service pipelines by welding is difficult, if not impossible. These applications include very thin-wall pipelines, older carbon steel pipelines with very high carbon equivalent values, pipelines made of high-alloy materials, sub-sea pipelines, etc. There are two primary concerns with welding onto in-service pipelines and piping systems. The first concern is for welder safety during welding, since there is a risk of burnthrough, where the welding arc causes the pipe wall to be penetrated allowing the contents to escape....
There are a number of applications where the attachment of hot tap fittings to in-service pipelines by welding is difficult, if not impossible. These applications include very thin-wall pipelines, older carbon steel pipelines with very high carbon equivalent values, pipelines made of high-alloy materials, sub-sea pipelines, etc. There are two primary concerns with welding onto in-service pipelines and piping systems. The first concern is for welder safety during welding, since there is a risk of burnthrough, where the welding arc causes the pipe wall to be penetrated allowing the contents to escape. The second concern is for the integrity of the system following welding, since welds made in-service cool at an accelerated rate as the result of the flowing contents ability to remove heat from the pipe wall. These welds, therefore, are likely to have hard, crack-susceptible heat-affected zones (HAZs) and may be susceptible to hydrogen cracking. An alternative method of attaching hot tap fittings is therefore attractive. This repot evaluated the use of Grouted Tee technology developed by Advantica for the installation of in-service branch connections in situations where in-service welding is difficult or impossible.