PURPOSE: To enable a pipe at a tank side divided at an outside part of a tank and another pipe at a refrigerator to be connected to each other and separated from each other without damaging a wall part around the tank and further to enable an inspection work or a repairing work for the refrigerator to be carried out easily and at a low cost.

CONSTITUTION: There are provided a joint 34 made of shape memory alloy having a characteristic in which it is expanded to open under a heating and increased temperature condition to enable each of extremity ends of a piping 30 on the side of a tank and a piping 32 on the side of a refrigerator to be removed and in turn it is reduced under a cooled temperature decreased condition to hold both pipings 30 and 32, and a heater 37 for heating the joint 34 so as to control a power supply to the heater 37.