| 摘要 |
PURPOSE:To eliminate the variance in the effect after execution of a freezing method for the purpose of improving the residual stress on the inside surface of plant pipings and tubular vessels in said method by combining quick heating for the pipe with the stopping of the cooling upon arrival of the intended internal pressure, thereby quickly dropping the pressure in the pipe. CONSTITUTION:The internal pressure in the section W enclosed by the two ice plugs I1, I2 in a pipe T is increased by the growth of the ice to deform the pipe T plastically, whereby a residual stress state is improved. Upon arrival of said internal pressure at the prescribed internal pressure at this time, the cooling is stopped; at the same time, electric current is conducted between the ring-like electrodes E and E mounted on the outer side in the cooling section J-J, that is, the pipe T, so that Joule heat is evolved. The pipe diameter is expanded by the thermal expansion caused by this quick heating of the pipe; at the same time, the binding force of the ice plugs to the pipe wall is decreased by the temp. elevation of the pipe wall and the internal pressure of the pipe is reduced quickly. |
