| 摘要 |
PURPOSE:To accurately and speedily detect a leak even if the flow rate of liquid to a sump varies slightly by monitoring the liquid level in the sump at all times and finding the rate of an increase in the liquid level per unit time from its process value. CONSTITUTION:The liquid level in the sump is monitored at all times to find the rate PV/ t of the increase in the liquid level PV per unit time from the process value. Then when PV/ t reaches a mean value PV0/ t0, a flag in a storage part 13 is set to 1 and when the increase rate becomes smaller than the mean value PV0/ t0, the flag is set to 0. If a leak occurs at a point A where the liquid level in the sump is rising so that PV0/ t0< PVa/ ta (increase rate at point A), the flag in the storage part 13 is set to 1. Then when the leak continues and the liquid level in the sump reaches a pump start liquid level while PV0/ t0< PVa/ ta, a pump is started. When the pump start signal is inputted 11, an arithmetic control part 11 checks the flag in the storage part 13 and outputs a leak detection signal through a control part 12 because the flag value is 1.
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