Abstract: To provide a cooling method of a superconducting cable line wherein moistures contained in the cable in the superconducting cable line after laid is removed before cooling, so that solidification of the moistures can be prevented from clogging of piping including a coolant flow channel and a return pipe. There is provided an inert gas generating vessel so that before the coolant is flown into the superconducting cable line 15, the inert gas is blown into the cable line from an inflow pipe 23 connected with a supply pipe 19? and is discharged from a discharge pipe 22 together with the gas. The inert gas is preheated by a heater 3 before feeding it into the cable line. The discharge pipe 22 connected with a discharge side B of the return pipe 19 is provided with a moisture measuring instrument 20 to measure a moisture content of the discharged gas.

Abstract: A first flange and a second flange are superposed and fastened with a bolt and a nut in a fastening operation, to implement a fastening structure used at temperature lower than atmospheric temperature for the fastening operation. Assuming that the first flange has a thickness L1 and a coefficient of linear expansion ?1, the second flange has a thickness L2 and a coefficient of linear expansion ?2, superposed first flange and second flange have a thickness L, and the bolt has a coefficient of linear expansion ?, a relation of L·??L1·?1+L2·?2 is satisfied, i.e. heat shrinkage of the bolt is not smaller than the total heat shrinkage of the first and second flanges. Thus, impairment of sealing property due to heat shrinkage is avoided at a flange junction used at low temperature.

Abstract: To provide a cooling method of a superconducting cable line wherein moistures contained in the cable in the superconducting cable line after laid is removed before cooling, so that solidification of the moistures can be prevented from clogging of piping including a coolant flow channel and a return pipe. There is provided an inert gas generating vessel so that before the coolant is flown into the superconducting cable line 15, the inert gas is blown into the cable line from an inflow pipe 23 connected with a supply pipe 19? and is discharged from a discharge pipe 22 together with the gas. The inert gas is preheated by a heater 3 before feeding it into the cable line. The discharge pipe 22 connected with a discharge side B of the return pipe 19 is provided with a moisture measuring instrument 20 to measure a moisture content of the discharged gas.

Abstract: A first flange and a second flange are superposed and fastened with a bolt and a nut in a fastening operation, to implement a fastening structure used at temperature lower than atmospheric temperature for the fastening operation. Assuming that the first flange has a thickness L1 and a coefficient of linear expansion &agr;1, the second flange has a thickness L2 and a coefficient of linear expansion &agr;2, superposed first flange and second flange have a thickness L, and the bolt has a coefficient of linear expansion &agr;, a relation of L·&agr;≧L1·&agr;1+L2·&agr;2 is satisfied, i.e. heat shrinkage of the bolt is not smaller than the total heat shrinkage of the first and second flanges. Thus, impairment of sealing property due to heat shrinkage is avoided at a flange junction used at low temperature.