| 摘要 |
PROBLEM TO BE SOLVED: To provide an execution method in which the execution can be easily performed in a short time, and the residual tensile stress exerted in an inner surface in a vicinity of a welded pipe portion is turned to the residual compressive stress. SOLUTION: In the execution method in which the residual tensile stress exerted in the inner surface of the welded pipe portion is turned to the residual compressive stress by using ice plug formed by the cooling from an outer surface of the pipe, a refrigerant container for forming ice plugs is installed on the upstream and downstream sides of a butt-welded pipe portion, the outer surface of the pipe is cooled to form the ice plug, and the outer surface of the pipe is cooled by using the refrigerant container for pipe expansion installed between the refrigerant containers for forming ice plug. Further, in the execution to the welded pipe portion having the large inside diameter, the ice plug forming position is placed on a bent pipe or an elbow or a branched pipe on the upstream and downstream sides of the butt-welded pipe portion. The execution in a short time and the execution with the refrigerant of low cooling capacity can be performed. The execution method which does not necessitate heating after the cooling is completed can be provided. COPYRIGHT: (C)2007,JPO&INPIT |
