VAPORIZER FOR LIQUEFIED NATURAL GAS AND COOLING AND STAND-BY HOLDING METHOD THEREOF

PURPOSE: To prevent heat source fluid from freezing in a device by providing a cutoff valve in a heating medium liquid pipe out of a heating medium vapor pipe for guiding heating medium vapor from an evaporator to vaporizers, and the heating medium liquid pipe for refluxing heating medium liquid condensed-liquefied in the vaporizers to the evaporizer. CONSTITUTION: The inlet ports 2b to 4b of vaporizers 2 to 4 are connected to a heat medium vapor exhaust port 1a of an evaporator 1 through a cutoff valve S-1 by a heat medium vapor pipe 5, and the exhaust ports 2a to 4a of vaporizers 2 to 4 are connected to a heating medium liquid inlet port 1b of the evaporator 1 through a cutoff valve S-2 by a heating medium liquid pipe 6. When a failure occurs in a control system, a supply system of heat source fluid, or when there is a possibility of drop in the temperature of heating medium in the evaporator 1 below zero deg.C, the cutoff valve S-1 provided in the heat medium vapor pipe 5 and the cutoff valve S-2 provided in the heating medium liquid pipe 6, are shut off to stop the evaporation of heating medium in the evaporator 1. Further, when only the cutoff valve S-2 provided in the heating medium liquid pipe 6 is shut off to seal the heating medium liquid in the vaporizers 2 to 4, the heat exchange between the heating medium vapor and LPG is restricted to stop the evaporation in the evaporator 1.