PURPOSE: To detect the abnromality, such as clogging or the like, of the instrumentation piping by a method wherein an abnormality detecting means, measuring the flow amount of liquid in the instrumentation piping and outputting a signal indicating the abnormality of the instrumentation piping when a deviation between the measured value and a logical value has exceeded a predetermined value, is provided in the device.

CONSTITUTION: The logical value of fluid discharging or suction pressure of a pump 40 is inputted into the negative side input terminal of a subtracting circuit 68. The actually measured value of the fluid discharging or suction pressure of the pump, which is converted into an electric signal by a pressure transducer 44, is inputted into the positive side input terminal of the subtracting circuit 68. An electric signal 70, indicating the deviation ΔP between the logical value and the actually measured value of the fluid discharging or suction pressure of the pump 40, is inputted into a deviation detecting circuit 71. When the deviation ΔP is larger than the detecting accuracy of abnormal condition, it is decided that the abnormality, such as clogging or the like, is existing in the instrumentation pipings 3, 4, 5, 6 and the abnormality is indicated on a lamp indicator 73.