METHOD OF EXTENDING LIFE EXPECTANCY OF HIGH-TEMPERATURE PIPING AND LIFE EXPECTANCY EXTENSION STRUCTURE OF HIGH-TEMPERATUE PIPING

摘要

A method of extending a life expectancy of a high-temperature piping, includes removing a heat insulation material which covers the piping having a high creep rupture risk, and lowering an outer surface temperature of piping, wherein a width of an exposed portion obtained 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 piping due to the removal of the heat insulation material is made from the tensile stress to the compressive stress, and the distance is calculated based on the following formulae, βx=5,;β=3(1-v2)a2h24;here, ν is a Poisson's ratio, a is an average radius of the piping, and h is a plate thickness of the piping.

主权项

1. A method of extending a life expectancy of a high-temperature piping, comprising:
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),
βx=5   (1) β is expressed by the following formula (2),β=3(1-v2)a2h24(2) here, ν 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.