In-Service welding

In-service welding is a technic of welding onto piping, pipeline or any equipment where there is product inside which may be pressurized and/or flowing.

There are 2 primary concerns with welding onto in-service pipelines.

1. First concern is to avoid “burning through” where welding arc causes the pipe wall to be breached.
2. Second concern is for hydrogen cracking. Due to flowing contents’ ability to remove heat from the pipe wall, welds can cool the in-service down at an accelerated rate and leads to hydrogen cracking.