Method and apparatus for relieving residual stress in welded pipe joints

Abstract From the Canadian patent

Residual stress in a butt-welded part of a pipe is improved where the butt-welded part is welded by abutting pipes to be welded. An outer surface of the pipe is cooled at each side of the butt-welded part to form ice plugs defining a watertight space therebetween inside the pipe. An outer surface of the pipe is cooled defining the watertight space to increase a water pressure in the watertight space to expand the butt-welded part of the watertight space in the pipe. A strain on the outer surface of the pipe is measured with a strain gauge at the butt-welded part to confirm that the outer surface of the pipe at the butt-welded part starts to plastically deform. In order to cool the outer …