| 摘要 |
PURPOSE:To eliminate the need of a pump, and to simplify a device by allowing the supply pressure of gas to remain behind between shut off valves by a timing for closing the shut off valves of the upstream side and the downstream side, and detecting leakage by the decreasing state of the residual pressure. CONSTITUTION:A downstream side shut off valve 2 is closed (point A) first, thereafter, an upstream side shut off valve 1 is closed (point B). By such an operation, the supply pressure PS of gas remains behind as a residual pressure between these shut off valves 4, and when the downstream side shut off valve 2 is leaking, this residual pressure is decreased gradually as the time elapses, and becomes pressure P3 after the time (t) is elapsed, and when there is no leakage, the pressure PS is maintained. The residual pressure between the shut off valves 4 is detected by a pressure detecting means 3, and when it is lower than an allowable limit pressure P2, a leakage detecting signal is outputted.
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