Friction stud welding

A clamping system is also required to hold the tool onto the work piece and to provide reaction to the force on the stud.

Some notable advantages of the process are: In the “as welded” condition the residual stresses are compressive which tend to result in good fatigue life.

When this process is used underwater, a shroud is fitted around the stud which prevents the weld from being cooled too rapidly by the surrounding water.

The hydraulically powered systems can also be used by divers and have welded to depths in excess of 300m from a Remotely Operated Vehicle (ROV).

Another option is a tripartite weld where the lug on the anode cable is made of steel with a tapered hole in it.

The advantage of this method is that there is no significant increase in the electrical resistance of the connection due to corrosion during the lifetime of the pipeline.

Many subsea pipelines have concrete weight coating on them and a small area of this can be removed with a water jet to permit welding.

A friction stud weld.
An M16 stud weld being performed with a shroud inside a vacuum clamp. In this example the central part of the clamp is flooded with water during welding.