Gas supply system

A gas supply system comprising:

• a gas tank that includes a self-closing valve that opens when a push rod is pushed in and that closes when the push rod is pulled out;
• a gas supply pipe to which the gas tank is connected, at a distal end of which the push rod is provided, and that leads gas from the gas tank to a gas utilizing device;
• an actuator that moves the gas tank forward and backward relative to the gas supply pipe;
• a sealing that seals off a connection space including an opening of the self-closing valve and the distal end of the gas supply pipe, when a distance between the self-closing valve and the push rod is shorter than a predetermined threshold value distance;
• a check valve that is provided in the gas supply pipe and that suppresses backflow of gas;
• a first pressure sensor that measures a pressure in the gas supply pipe upstream of the check valve;
• a second pressure sensor that measures a pressure in the gas supply pipe downstream of the check valve;
• and
• a controller, wherein
• when replacing the gas tank in a state in which the gas supply pipe is connected and the self-closing valve is open, the controller
• moves the gas tank backward to a position where the self-closing valve is closed while maintaining the sealing of the connection space,
• reduces a predetermined amount of gas from the gas supply pipe on a downstream side of the check valve,
• outputs a gas leak signal indicating that a gas leak is occurring other than at the check valve, when an amount of decrease in a measurement value of the first pressure sensor or the second pressure sensor, before and after a first amount of time elapses, exceeds a predetermined first differential pressure threshold value,
• when the amount of decrease in the measurement value of the first pressure sensor or the second pressure sensor before and after the first amount of time elapses does not exceed the first differential pressure threshold value, the gas tank is moved backward to a position where the sealing of the connection space is disengaged, and
• when the amount of decrease in the measurement value of the second pressure sensor before and after a second amount of time elapses exceeds a predetermined second differential pressure threshold value, a check valve abnormality signal indicating that a gas leak is occurring in the check valve is output, and also the gas tank is moved forward to a position where the connection space is sealed.