| 摘要 |
PROBLEM TO BE SOLVED: To surely detect reverse flow due to a defective check valve. SOLUTION: In a fluid circuit constructed by arranging a pipe 30 led from a fluid storage tank 10 to a predetermined fluid supply position (a venturi nozzle 20, for example) and provided with at least on check valve 31 (32) in this predetermined position and connecting a pump 40 to the pipe 30, a sensor 50 consisting of an electrical resistance element whose resistance value is changed when heat is taken away by fluid is arranged in the pipe 30, while a sensor output is monitored by an abnormal condition detecting means 60, and when the sensor output is detected during a stopping duration of the pump 40, an abnormal condition signal is produced.
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