Heat-treating method for pipes
AssigneeHitachi, Ltd.
InventorsNoriaki Matsuda, Kunio Enomoto
Life of this patent
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Abstract
Disclosed is a method of heat-treating a pipe in which cooling water is passed through the pipe while the pipe is heated from the outer side thereof, so as to create a temperature differential between the outer and the inner sides of the pipe, so that the inner side of the pipe may be tension-yielded or the outer side of the pipe may be compression-yielded, thereby to generate a compressive residual stress and a tensile residual stress at the inner and the outer sides of the pipe, respectively.
Claims26
A method of heat-treating piping in situ within a plant comprising the steps of:
- (a) supplying a liquid coolant to the piping after said piping is installed by plastic working or welding of portions of the piping in a plant, said plastic working or welding causing residual stresses that may lead to stress corrosion;
- (b) heating the outer side of the plastic worked or welded portions of said piping while the liquid coolant is present in said piping to create a great temperature differential between said outer side of said piping and the inner side of said piping so that compressive yielding is produced in said outer side of said piping and tensile yielding is produced in said inner side of said piping;
- and then
- (c) stopping the heating of said piping whereby residual compressive stress is induced into said portions to reduce possible stress corrosion during subsequent operation of said plant.
A method of heat-treating piping in situ within a nuclear power plant comprising the steps of:
- (a) supplying a liquid coolant to the piping after the piping is installed by plastic working or welding of portions of the piping in the plant, said working or welding causing residual stresses that may lead to stress corrosion of said piping;
- (b) heating the outer side of the plastic work or welded portions of said piping while said coolant is present in said piping to create a great temperature differential between said outer side of said piping and the inner side of said piping so that compressive yielding is produced in said outer side of said piping and tensile yielding is produced in said inner side of said piping;
- and then
- (c) stopping the heating of said piping whereby a residual compressive stress is induced into said portions to reduce possible stress corrosion during operation of said nuclear power plant.
Dependencies are inferred from the claim text.