To provide a gas shut-off device capable of correctly detecting inner pipe leakage even when gas supply pressure is varied.
The gas shut-off device includes: an ordinary period measurement part 14 for performing ordinary flow rate measurement; a flow rate operation part 15 for calculating a flow rate based on propagation time measured by the ordinary period measurement part 14; a no-flow-rate determination part 16 which when the flow rate calculated by the flow rate operation part 15 is a predetermined range or less, determines no flow rate; a short period measurement part 17 which when the no-flow-rate determination part 16 determines no flow rate, performs measurement of propagation time for several seconds to several hundred seconds at a frequency of once or more per day in a short propagation time measurement period of about 0.001 to 0.1 seconds shorter than the period of the ordinary period measurement part 14 and shorter than gas pressure supply variation; and a leakage determination part 18 which when the gas flow rate calculated by the flow rate operation part 15 is a predetermined value or more and is continued by the predetermined number of times or more, determines gas leakage based on the measurement result of the propagation time by the short period measurement part 17.
YASUDA KENJI
KONO YASUHARU
永野 大介
藤井 兼太郎
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