METHOD FOR EXTENDING LIFE OF HIGH-TEMPERATURE PIPING AND LIFE-EXTENDING STRUCTURE FOR HIGH-TEMPERATURE PIPING

摘要

A method of extending a life expectancy of a high-temperature piping, includes, when it is determined that a continued stationary use cannot be performed by a remaining life expectancy evaluation of a creep rupture of a welded portion of the high-temperature piping, removing a part of a heat insulation material which covers a location having a high creep rupture risk in the high-temperature piping, and lowering an outer surface temperature of the high-temperature piping locally to extend the life expectancy of the location having the high creep rupture risk, wherein a width of an exposed portion obtained by removing a part of a heat insulation material is twice or more a distance from a peeled-off end portion of the exposed portion to a portion where a compressive stress is asymptotical to 0 after a change in stress between a tensile stress and the compressive stress occurring in the high-temperature piping due to the removal of the heat insulation material is made from the tensile stress to the compressive stress, and the distance at which the compressive stress after a change in stress is made from the tensile stress to the compressive stress is asymptotical to 0 is based on the following formula (1), ²x = 5 ² is expressed by the following formula (2), ² = 3 �¢ 1 - v 2 a 2 �¢ h 2 4 here, ½ is a Poisson's ratio, and symbol a is an average radius of the piping, and symbol h is a plate thickness of the piping.