Patent ID: 7574897

Claim:
A device for detecting leakage of liquid in a tank, comprising: a measurement slim-pipe into/from the lower end of which the liquid in a tank is injected or discharged; a measurement pipe connected to the upper end of the measurement slim-pipe and having a cross-section area larger than that of the measurement slim-pipe; a flow rate sensor section for measuring the flow rate of liquid in the measurement slim-pipe, which is additionally provided to the measurement slim-pipe and includes a first temperature sensor, indirectly heated sensor and a second temperature sensor, the indirectly heated sensor being provided with a heater and third temperature sensor; a pressure sensor for measuring the liquid level of the liquid; and a leakage detection controller connected to the flow rate sensor section and pressure sensor, wherein the leakage detection controller has: a voltage generation circuit for applying a voltage to the heater; a first leakage detection circuit which is connected to the first and second temperature sensors and generates an output corresponding to a difference between temperatures sensed by the first and second temperature sensors; and a second leakage detection circuit which is connected to the indirectly heated sensor and generates an output corresponding to a temperature sensed by the third temperature sensor, performs: a first leakage detection to detect leakage of liquid in the tank based on a value equivalent to the liquid flow rate calculated using the output of the first leakage detection circuit; a second leakage detection to detect leakage of liquid in the tank based on the liquid level variation rate with respect to time measured by the pressure sensor; and a third leakage detection to detect leakage of liquid in the tank based on a value equivalent to the liquid flow rate calculated using the output of the second leakage detection circuit, and outputs at least one of detection results of the first to third leakage detections that fall within first to third predetermined ranges which are defined for each of the first to third leakage detections.