JP2003214974A - Leak detector for liquid in tank - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a simplified but accurate leak detector capable of detecting a trace leak of liquid in a tank. <P>SOLUTION: A vertical measuring pipeline unit into which the liquid in a tank is introduced has a measuring tube 10 and a measuring capillary tube 14. The capillary tube 14 is located below the tube 10 and is not more than 1/50 of the tube 10 in terms of cross section area. The capillary tube 14 has a thermal flow sensor 16 for measuring the liquid flow rate. An opening/closing valve 126 and a leak detector circuit 22 are provided at the upper part of the tube 10. The sensor 16 senses the flow rate upon opening of the valve 126 after a closure of a prescribed time length, eight hours for instance. The measurements are integrated, and the circuit 22 detects a leak based on the integrated value, issuing a leak-detected signal when the integrated value increases to reach or exceed a prescribed level. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for detecting liquid leakage in a tank, and more particularly to a device for detecting liquid leakage from a tank based on the flow of liquid.

A liquid leak detection device of the present invention is, for example,
It is suitably used to detect a minute amount of liquid leakage from fuel oil tanks such as oil tanks buried underground and tanks of various liquid chemicals.

[0003]

2. Description of the Related Art Conventionally, the problems to be solved by the invention
Most fuel oil tanks in gas stations are underground. The underground tank is likely to cause minute cracks due to deterioration over time, and oil leakage may occur from there. If such a situation is reached, it will cause pollution of the surrounding environment, and it will take a huge cost to recover it. For this reason, in such an underground fuel oil tank, it is obliged to regularly detect whether or not there is an oil leak (or a tank crack that causes the oil leak).

As a method conventionally used for detecting such an oil leak, a gas such as air is pressurized and injected into the tank while the tank is hermetically sealed, and whether or not the pressure decreases after a predetermined time has elapsed. There is something to detect. On the contrary, there is a method in which the inside of the tank is depressurized while the inside of the tank is hermetically sealed, and whether or not the pressure has increased after a predetermined time has elapsed is detected.
However, with these methods, it is necessary to seal all the openings of the tank with putty etc. prior to the leak detection work, and in some cases it is necessary to stop the use of the tank and drain all the oil in the tank. It becomes necessary and the work becomes very troublesome. In addition, if the above seals are not perfect, the leaks detected by these methods do not necessarily reflect the actual oil leaks due to tank cracks, etc. Cannot be said to have high detection accuracy.

On the other hand, other methods for detecting liquid leakage include, for example, Japanese Patent Application Laid-Open No. 62-223640 and Japanese Patent Application Laid-Open No.
As described in Japanese Patent Application Laid-Open No. 0-120099, there is one that detects a change in liquid level. Since this method measures the fluctuation of the liquid level based on the volume change of the liquid in the tank due to the leak, the leak can be accurately reflected and detected. However, in this method, when the leak amount is small, the fluctuation of the liquid surface level is extremely small, and therefore the detection thereof is extremely difficult.

In order to promptly deal with the leakage of the liquid in the tank, it is important that cracks in the tank are small and the leakage can be detected at an early stage. Therefore, a small amount of the leakage can be detected. It cannot be said that the method of detecting the level fluctuation can sufficiently meet such a demand.

Therefore, it is an object of the present invention to provide a leak detection device for liquid in a tank, which can detect even a small amount of leak easily and accurately.

It is another object of the present invention to provide a leak detection device for liquid in a tank, which can detect leaks without stopping the use of the tank.

A further object of the present invention is to provide a leak detection device for liquid in a tank which can be mounted on an existing tank without special processing.

A further object of the present invention is to provide a leak detection device for liquid in a tank, which is capable of accurately grasping the leak amount.

[0011]

According to the present invention, in order to achieve the above object, there is provided a device which is inserted into a tank and detects a liquid leak in the tank, wherein the liquid in the tank is Is equipped with a measuring line through which
The measuring pipe line has a measuring pipe and a measuring thin pipe communicating with the measuring pipe and located below the measuring pipe and having a cross-sectional area smaller than that of the measuring pipe. A sensor used to measure the flow rate of the liquid is additionally provided, and an opening / closing valve is provided on the upper part of the measuring tube, and the sensor is continuously opened after closing the opening / closing valve for a predetermined time. There is provided a leak detection device for liquid in a tank, which is provided with a leak detection means for detecting a leak of liquid in the tank based on an integrated value of flow rates measured by using the leak detection device.

In one aspect of the present invention, the cross-sectional area of the measuring thin tube is 1/50 or less, preferably 1/100 or less, more preferably 1/300 or less of the cross-sectional area of the measuring tube. In one aspect of the present invention, the measuring tube and the measuring thin tube are oriented substantially in the vertical direction.

In one aspect of the present invention, the sensor is a thermal flow sensor. In one aspect of the present invention, the thermal type flow sensor includes a flow rate detection unit and a temperature detection unit, and the leak detection unit includes an electric circuit including the flow rate detection unit and the temperature detection unit. To obtain the temperature-compensated flow rate value. In one aspect of the present invention, both the flow rate detection unit and the temperature detection unit include a heat transfer member that is in contact with the outer surface of the measurement thin tube. In one aspect of the present invention, the leak detection means controls opening / closing of the opening / closing valve.

In one aspect of the present invention, a liquid level height detecting means used for detecting the height of the liquid level of the liquid is provided, and the leak detecting means uses the sensor. The integrated value of the measured flow rate is corrected based on the liquid level height value detected using the liquid level height detection means and the value of the parameter related to the shape of the tank to obtain a corrected integrated value, The leak of the liquid in the tank is detected based on the corrected integrated value. In one aspect of the present invention, the liquid level height detecting means is a pressure sensor that detects the liquid pressure received from the liquid in the tank. In one aspect of the present invention, the parameter relating to the shape of the tank is the ratio of the effective cross-sectional area of the tank to the cross-sectional area of the measuring pipe at the same height, and the correction integrated value is the integrated value and the liquid level height. It is obtained by multiplying the value of the parameter by the height value.

In one aspect of the present invention, the leak detection means issues a leak detection signal when the integrated value of the flow rate or the corrected integrated value is equal to or more than a predetermined value.

In one aspect of the present invention, the measurement conduit is formed by passing through a sheath tube and a sensor holder member attached to a lower portion of the sheath tube, and the sensor holder member holds the sensor. The measurement thin tube is arranged through the sensor holder member. In an aspect of the present invention, a cap member is attached to an upper portion of the sheath tube, and the cap member is fixed to a communication passage that communicates the measurement tube with the outside and a means for fixing the opening to the tank. And the on-off valve is interposed in the communication passage.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a partially omitted sectional view showing an embodiment of a leak detection device for liquid in a tank according to the present invention.
Is a partial perspective view thereof.

The detection device comprises a cylindrical sheath 2 arranged vertically, a cap member 4 adapted to the upper part of the sheath tube, and a sensor holder member 6 adapted to the lower part of the sheath tube 2. It has and. Within the sheath 2 there is a measuring tube 10 extending between the lower part of the cap member 4 and the upper part of the sensor holder member 6. A communication passage 12 is formed in the cap member 4, and the communication passage 12 communicates the inside of the measuring tube 10 with the outside of the cap member 4 through the small holes 12a and 12b.

The sensor holder member 6 is provided with a measuring thin tube 14 extending vertically. The upper end of the measuring thin tube 14 opens into the measuring tube 10, and the lower end of the measuring thin tube 14 opens into a recess 6 a formed in the lower portion of the sensor holder member 6. The measuring capillary tube 14 forms a measuring conduit with the measuring tube 10. When the detector is inserted into the tank from above, the liquid in the tank is introduced into the measuring conduit from the lower end opening of the measuring capillary tube 14. A liquid level is formed in the measuring tube 10. The cross-sectional area of the measuring thin tube 14 is smaller than the cross-sectional area of the measuring tube 10, for example, 1/50 or less, preferably 1/100 or less, more preferably 1/3 of the cross-sectional area of the measuring tube 10.
It is 00 or less. Thus, by making the cross-sectional area of the measuring thin tube 14 sufficiently smaller than the cross-sectional area of the measuring tube 10,
The flow velocity of the liquid in the measuring thin tube 14 due to the height variation of the liquid surface can be made extremely large.

The sensor holder member 6 is provided with a sensor 16 for detecting a leak in the sensor housing recess 6b. The sensor 16 is used to measure the flow rate of the liquid in the measuring thin tube 14 and the integrated value thereof for leak detection, and is connected to the leak detection circuit 22 via the sensor wiring 20. As shown, the wire 20 extends through the space inside the sheath tube 2 and outside the measuring tube 10 and through a vertical through hole formed in the cap member 4. A filter mesh 24 is attached to the lower end of the sensor holder member 6 so as to cover the recess 6a.

FIG. 3 is a diagram showing the sensor 16.
(A) shows a front view and (b) shows a side view. Sensor 1
Reference numeral 6 denotes an indirectly heated thermal type flow rate sensor, which includes a flow rate detection unit 16
It has F and the temperature detection part 16T. These are integrated by a common resin housing 16H. The flow rate detection unit 16F and the temperature detection unit 16T have heat transfer members 16Fa and 16Ta and electrode terminals 16Fb and 16Tb for heat exchange with the liquid, respectively. FIG. 4 shows a measuring thin tube 1.
4A and 4B are diagrams showing the sensor 4 and the sensor 16, where FIG. 4A is a front view and FIG. 4B is a side view. The heat transfer members 16Fa and 16Ta of the flow rate detection unit and the temperature detection unit are both measuring thin tubes 14.
Is in contact with the outer surface of the liquid flow sensor, so that heat exchange between the flow rate detection unit 16F and the temperature detection unit 16T and the liquid in the measurement thin tube 14 is possible. As shown in FIG. 1, the heat transfer members 16Fa and 16Ta of the sensor 16 are disposed in the detection cavity 6c formed in the sensor holder member 6 in the measurement capillary tube 1c.
In contact with 4.

Further, as shown in FIG. 1, the communication passage 1
An on-off valve 126 and its driver (driver) 12
8 are arranged. The on-off valve 126 is vertically movable between a closed position (lower position) that closes the small hole 12a and an open position (upper position) that is separated from the small hole 12a. Such a valve mechanism can be constituted by, for example, an electromagnetic valve. When the open / close valve 126 is in the open position, the inside of the measuring pipe 10 communicates with the outside of the cap member 4, but when the open / close valve 126 is in the closed position, the inside of the measuring pipe 10 and the outside of the cap member 4 are not connected. Communication is broken. The driver 128 is connected to the leak detection circuit 22 via the drive wiring 130.

FIG. 5 includes a circuit for measuring the flow rate using the sensor 16 and further controls the internal and external communication at the upper part of the measuring pipe 10 by using the opening / closing valve 126 and the driver 128 to detect a leak. FIG. 3 is a schematic diagram showing a leak detection circuit 22 that constitutes a leak detection unit that does this. The circuit for this flow rate measurement is similar to the circuit of the indirectly heated type thermal flow meter as described in, for example, Japanese Patent Application Laid-Open No. 11-118566, and the instantaneous flow rate of the liquid flowing in the measurement thin tube 14 is the same. The electric signal according to is output. It is also possible to appropriately integrate and output an electric signal corresponding to the integrated flow rate.

In the flow rate detecting portion 16F, the heat transfer member 1
A thin film heating resistor 48 and a thin film temperature sensitive resistor 41 are provided so that heat can be exchanged with respect to 6 Fa. Further, in the temperature detector 16T, a thin film temperature sensitive resistor 41 'is provided so that heat can be exchanged with the heat transfer member 16Ta.

The DC voltage V1 is supplied to the bridge circuit (detection circuit) 40. The bridge circuit 40 includes the flow rate detection unit 1
It includes a thin film temperature sensitive resistor 41 of 6F, a thin film temperature sensitive resistor 41 ′ of the temperature detection unit 16T, and resistors 43 and 44. The potentials Va and Vb at the points a and b of the bridge circuit 40 are input to the differential amplification / integration circuit 46.

On the other hand, the DC voltage V2 is detected by the flow rate detecting unit 1 mentioned above.
Through the transistor 50 for controlling the current supplied to the thin film heating resistor 48 of 6F, the thin film heating resistor 48
Is supplied to. That is, in the flow rate detection unit 16F, the heat transfer member 16Fa is generated based on the heat generated by the thin-film heat generating resistor 48.
Through the influence of the heat absorption by the liquid in the measurement thin tube 14 via, the temperature sensing by the thin film temperature sensing resistor 41 is executed. Then, as a result of the temperature sensing, a difference between the potentials Va and Vb at the points a and b of the bridge circuit 40 is obtained.

The value of (Va-Vb) changes as the temperature of the temperature sensitive resistor 41 changes according to the flow rate of the liquid.
By appropriately setting the resistance values of the resistors 43 and 44 of the bridge circuit 40 in advance, the value of (Va-Vb) can be set to zero in the case of a desired reference liquid flow rate. At this reference flow rate, the output of the differential amplification / integration circuit 46 becomes constant (a value corresponding to the reference flow rate), and the resistance value of the transistor 50 also becomes constant. In that case, the thin film heating resistor 4
The partial pressure applied to 8 also becomes constant, and the voltage at point P at this time indicates the reference flow rate.

When the liquid flow rate is increased or decreased, the output of the differential amplification / integration circuit 46 changes in polarity (depending on whether the resistance-temperature characteristic of the temperature sensitive resistor 41 is positive or negative) and its magnitude according to the value of (Va-Vb). Changes, and the differential amplification / integration circuit 46 changes accordingly.
Output changes.

When the liquid flow rate increases, the temperature of the temperature sensitive resistor 41 decreases, so that the differential amplifier / integrator circuit is arranged to increase the heat generation amount of the thin film heat generating resistor 48 (that is, increase the power). From 46, a control input for reducing the resistance value of the transistor 50 is applied to the base of the transistor 50.

On the other hand, when the liquid flow rate decreases, the temperature of the temperature sensitive resistor 41 rises, so that the thin film heating resistor 48 is used.
To reduce the amount of heat generated (that is, reduce the power),
From the differential amplification / integration circuit 46, a control input for increasing the resistance value of the transistor 50 is applied to the base of the transistor 50.

As described above, the heat generation of the thin-film heat generating resistor 48 is feedback-controlled so that the temperature detected by the temperature sensitive resistor 41 always becomes the target value regardless of the change in the liquid flow rate. Then, at that time, the thin film heating resistor 4
Since the voltage applied to 8 (voltage at point P) corresponds to the liquid flow rate, it is taken out as a flow rate output. This flow rate output can be supplied to the A / D converter 52 if desired.
It can be converted into a digital signal. A digital signal corresponding to this flow rate value is input to the CPU 54.
A timer 56 is connected to the CPU 54.

The CPU 54 detects a leak as described later and outputs a leak detection signal. The temperature detection unit 16T
Is used to obtain a compensated flow rate value for liquid temperature.

FIG. 6 is a schematic cross-sectional view showing a state in which the leak detection device of this embodiment is mounted on a tank, and FIG. 7 is an enlarged cross-sectional view of a portion of the leak detection device fixed to the tank.

In FIG. 6, a tank 30 contains petroleum OIL as a liquid. Connected to the tank 30 are an oil supply pipe 32 for replenishing the oil OIL from the outside and an oil supply pipe 34 for pumping the oil OIL at the time of sale to the consumer. Further, the tank 30 is provided with a measuring port 36 as an opening for inserting a measuring scale. The measuring port 36 is, for example, a circular opening having a diameter of about 30 mm and is usually closed by a lid. The lid is removed, the outer peripheral edge portion of the cap portion 4 is arranged on the upper end portion of the measuring port via the packing 60, and the cap nut 62 is fitted to the measuring port 36 to fix the leak detection device 38 to the tank 30. . As shown in FIG. 6, the oil OI in the tank 30
The liquid level of L is located above the sensor 16 and below the cap portion 4, so that the liquid level in the detection device 38 is located within the measuring tube 10 shown in FIG. 7.

Next, the leak detecting operation of the leak detecting apparatus of this embodiment will be described. The leak detection operation is performed in a state where the oil OIL is not replenished from the outside through the oil supply pipe 32 and the oil OIL is not pumped out through the oil supply pipe 34. Such a state is, for example,
It is realized during non-business hours such as night.

FIG. 8 is a schematic view showing the fluctuation of the liquid level in the tank at the time of leak detection. First, as shown in FIG. 8A, the opening / closing valve 126 is moved downward by the driver 128 to the closed position. After that, for a predetermined time (for example, 4
The open / close valve 126 is maintained in the closed position for up to 12 hours. When there is a leak of petroleum OIL from the tank 30, as shown in FIG. 8B, the liquid level in the tank 30 excluding the inside of the measuring pipe 10 is indicated by the arrow X after the elapse of the predetermined time. Is descending. However, the liquid level in the measuring pipe 10 of the detection device 38 does not drop because the open / close valve 126 is in the closed position.

Then, as shown in FIG. 8 (c),
The driver 128 moves the open / close valve 126 upward to the open position. Thereby, the measuring tube 10 of the detection device 38
The liquid level in the tank is lowered until it becomes the same as the liquid level in the tank 30 excluding the inside of the measuring pipe 10. At that time, the flow rate measuring circuit using the sensor 16 detects the flow rate F based on the downward flow as indicated by the arrow Y. The detected flow rate changes with time t, as shown in FIG.

Since the integrated value IF = ∫Fdt obtained by time-integrating this flow rate F corresponds to the leakage amount of the oil OIL in the tank 30 within the predetermined time, the CPU 54 causes the A / D converter 52 to operate. The integrated value IF is calculated based on the flow rate value input from, and the following processing is performed according to the magnitude of the flow rate integrated value: (a) When the flow rate integrated value is less than the predetermined value, If it is determined that there is no leakage, and (b) the integrated value of the flow rate is equal to or greater than the predetermined value, it is determined that there is leakage and a leakage detection signal is issued.

The reason why there is no leakage when the integrated value of the flow rate is less than the predetermined value is because the measurement error in the flow rate measurement is taken into consideration. If the measurement error can be reduced, the predetermined value can be reduced.

The timing of the above operation (particularly in FIG. 8A,
The start timing of the state (c) can be set in the timer 56 in advance. Alternatively, the operation timing may be set by manual input to an input means (not shown).

As described above, in the present embodiment, the leak is detected based on the flow rate integrated value corresponding to the amount of petroleum OIL leaked from the tank 30 over a predetermined time, so that the leak per unit time is extremely small. Even if there is, the leak can be detected accurately.

By the way, the shape of the tank 30 does not always have a uniform cross-sectional area (horizontal cross-sectional area) in the vertical direction. That is, as shown in FIG. 10, in the case of a cylindrical tank having a circular vertical cross-sectional shape, the cross-sectional area at the lower portion and the upper portion of the tank is smaller than that at the intermediate height portion of the tank. On the other hand, the measuring pipe 10 of the detector has a uniform cross-sectional area (horizontal cross-sectional area) in the vertical direction. Therefore, even if the integrated value IF of the flow rate of the petroleum OIL flowing through the measuring thin tube 14 is the same with the fluctuation of the liquid level of the measuring pipe 10 (that is, the amount of fluctuation of the liquid level is the same), the liquid level is the tank. In the lower part or the upper part of the oil, the fluctuation of the oil amount in the whole tank is smaller than that in the middle height part, so even if the same integrated flow rate is detected, the amount of oil leakage is small. It depends on the height of the liquid level in the tank.

In the embodiment of the leak detection device for liquid in a tank according to the present invention described below, in order to solve the technical problem based on such a liquid level, the leak amount is not proportional to the integrated value of the detected flow rate. The surface level H is detected, the detected flow rate integrated value is corrected based on the detected level, and the corrected flow rate integrated value is obtained. Leak detection is performed based on the magnitude of the corrected flow rate integrated value.

That is, in this embodiment, as shown in FIG. 10, as the liquid level detecting means used for detecting the liquid level of the liquid, the liquid received from the liquid in the tank is used. A pressure sensor 26 that detects pressure is arranged. When the pressure sensor 26 is inserted into the tank of the detection device,
The pressure receiving surface is adapted to receive the liquid pressure from the liquid in the tank outside the sheath. The pressure sensor 26 is connected to the leak detection circuit 22 via a wiring extending in the same path as the sensor 16. The output of the pressure sensor 26 (the output corresponding to the liquid surface height value) is A / D converted and input to the CPU 54.

To the CPU 54, the value of a parameter relating to the shape of the tank is input by an input means (not shown). The parameter is, for example, the effective cross-sectional area of the internal space of the tank with respect to the cross-sectional area (horizontal cross-sectional area) of the measurement tube 10 at the same height (the horizontal cross-sectional area of the measurement tube 10 is removed [however, The cross-sectional area of the internal space is not removed]). Such parameters can be created in advance based on the shape of the tank 30 and the measuring tube 10 of the detection device 38 attached to the tank.

In FIG. 11, when the diameter of the tank 30 is D and the liquid level height from the lowest portion of the tank 30 is H, the value of the parameter P and the flow rate output F with respect to the value of H / D.
The magnitude relationship between the value of and is shown schematically. Usually, the liquid level is in the region where H / D is 0.1 or more and 0.9 or less. As shown in FIG. 10, the pressure sensor 26 has a height H0 from the bottom of the tank 30 (H0 is known and H0
0 / D is set to be 0.1 or less), and the liquid level height is H from the pressure sensor 26.
It is at a height of 1. Therefore, by detecting the liquid level height corresponding to H1 by the pressure sensor 26, the liquid level height H from the lowest portion of the tank 30 can be detected.

As the parameters relating to the shape of the tank, in addition to the above parameters, the value of the inner diameter D of the tank and the value of the length L (dimension in the direction perpendicular to the paper surface of FIG. 10) can be mentioned. . In this case, the CPU 54 obtains the above ratio by calculation.

By inputting the type of liquid in the tank 30 or its specific gravity, the height value of the liquid level detected by the pressure sensor 26 can be calibrated in the CPU 54.

The CPU 54 calculates the corrected integrated value based on the integrated value IF obtained in the same manner as in the above embodiment and the liquid level height corresponding value input from the pressure sensor 26. This correction integrated value can be obtained by multiplying the flow rate integrated value by the parameter value (the above ratio) corresponding to the liquid level height value H obtained based on the input value from the pressure sensor 26. As the liquid level height corresponding value used for correction, any value before and after the liquid level drop may be used, or an average value of the values before and after the liquid level drop may be used. is there. This is because the amount of leakage is usually sufficiently small compared to the capacity of the entire tank, and the parameter value does not change significantly before and after the above-mentioned drop in liquid level.

In this embodiment, the correction integrated value is calculated, and the following processing is performed according to the magnitude of the correction integrated value: (a) The correction integrated value is a predetermined value (different from the above embodiment). If it is less than), it is determined that there is no leakage,
(B) If the corrected integrated value is equal to or greater than the predetermined value, it is determined that there is a leak, and a leak detection signal is issued.

In the present embodiment, the pressure sensor for detecting the liquid pressure received from the liquid in the tank is used as the liquid level height detecting means, but in the present invention, other suitable liquid level height detecting means is used. Means, such as a mechanical type using a float, an optical type that detects light reflection on the liquid surface, and an electric type that detects a difference in electrical characteristics such as electric resistance values above and below the liquid surface It is also possible to use etc. In such a case, if necessary, a vertical liquid level height detecting conduit different from the above measuring conduit can be attached.

FIG. 12 is a partial cross-sectional view showing another embodiment of the leak detection device for liquid in a tank according to the present invention. In this embodiment, the leak detection circuit 22 is housed in a member integrated with the cap member 4. This makes the device compact. The configuration and function of the leak detection circuit 22 are similar to those of the above-described embodiment.

FIG. 13 is a partial sectional view showing still another embodiment of the leak detection device for liquid in a tank according to the present invention. In this embodiment, the sensor holder member 6 is provided with a bypass 66 in the up-down direction that connects the measurement tube 10 and the recess 6a to each other in addition to the measurement thin tube 14. A check valve 68 is attached to the bypass 66, and the check valve 68 is provided.
This prevents the oil OIL from flowing downward in the bypass 66. When inserting the leak detection device into the tank,
If the petroleum OIL is not introduced into the measuring pipe 10 promptly by using only the measuring thin tube 14, it takes a long time to start the leak detecting operation. The leak detection operation can be started immediately after the insertion of the detection device. The cross-sectional area of the bypass 66 is made sufficiently larger than the cross-sectional area of the measuring thin tube 14 so that such a function can be exhibited.

[0055]

As described above, according to the leak detecting device of the present invention, the liquid flow rate is measured in the measuring thin tube which is in communication with the measuring tube, is located below the measuring tube, and has a smaller cross-sectional area than the measuring tube. A sensor is attached, and the on-off valve installed on the upper part of the measuring pipe is closed for a predetermined time and then opened, and then the leak of the liquid in the tank is detected based on the integrated value of the flow rate measured by the sensor. Therefore, even a very small amount of leak can be detected easily and accurately without stopping the use of the tank, and the existing tank can be mounted without any special processing.

Further, according to the leak detecting apparatus of the present invention, the leak of the liquid in the tank is detected by detecting the leak of the liquid in the tank based on the corrected integrated value obtained based on the liquid level height value and the parameter value related to the tank shape. Even if is a shape in which the cross-sectional area changes in the vertical direction, the leak amount can be accurately grasped, and based on this, accurate liquid leak detection can be performed.

[Brief description of drawings]

FIG. 1 is a partially omitted sectional view showing a leak detection device for liquid in a tank according to the present invention.

FIG. 2 is a partial perspective view showing a leak detection device for liquid in a tank according to the present invention.

FIG. 3 is a diagram showing a sensor.

FIG. 4 is a diagram showing a measuring capillary tube and a sensor.

FIG. 5 is a schematic diagram showing a leak detection circuit.

FIG. 6 is a schematic cross-sectional view showing a state in which the leak detection device for liquid in a tank according to the present invention is mounted on the tank.

FIG. 7 is an enlarged cross-sectional view of a portion of the liquid leakage detection device for a tank according to the present invention, which is fixed to the tank.

FIG. 8 is a schematic diagram showing a liquid level variation in a tank when a leak is detected by the tank liquid leak detection device according to the present invention.

FIG. 9 is a diagram showing a change over time in the flow rate detected by the leak detection device for liquid in a tank according to the present invention.

FIG. 10 is a schematic cross-sectional view for explaining leak detection by the leak detection device for liquid in a tank according to the present invention.

11 is a diagram schematically showing a magnitude relationship between a parameter value and a flow rate output value in the tank shown in FIG.

FIG. 12 is a partial cross-sectional view showing a leak detection device for liquid in a tank according to the present invention.

FIG. 13 is a partial cross-sectional view showing a leak detection device for liquid in a tank according to the present invention.

[Explanation of symbols]

2 sheath tube 4 Cap member 6 Sensor holder member 6a recess 6b Sensor housing recess 6c Detection cavity 10 measuring tubes 12 passages 12a, 12b small hole 14 Measuring tube 16 sensors 16F Flow rate detector 16T temperature detector 16Fa, 16Ta heat transfer member 16Fb, 16Tb electrode terminal 16H housing 20 wiring 22 Leak detection circuit 24 filter mesh 26 Pressure sensor 30 tanks 32 lubrication pipe 34 Oil supply pipe 36 Measuring port 38 Leak detection device 40 bridge circuit (detection circuit) 41,41 'Thin film temperature sensitive resistor 43,44 resistor 46 Differential amplification / integration circuit 48 Thin film heating resistor 50 transistors 52 A / D converter 54 CPU 56 timer 60 packing 62 cap nut 66 Bypass 68 Check valve 126 open / close valve 128 drivers 130 wiring OIL oil

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Takayuki Takahata             1333-2 Hara-shi, Ageo-shi, Saitama Mitsui Mining & Smelting             Research Institute, Inc. (72) Inventor Toshimi Nakamura             1333-2 Hara-shi, Ageo-shi, Saitama Mitsui Mining & Smelting             Research Institute, Inc. (72) Inventor Toshiaki Kawanishi             1333-2 Hara-shi, Ageo-shi, Saitama Mitsui Mining & Smelting             Research Institute, Inc. F-term (reference) 2F014 BA10                 2F030 CA10 CB02 CC03 CD15 CE02                       CE04                 2G067 AA04 BB22 CC03 DD04 DD07                 3E070 AA02 AB03 AB09 CA13 CB03                       CC02 DA01 QA04 VA13

Claims (15)

[Claims] 1. A device which is inserted into a tank to detect leakage of liquid in the tank, the measuring pipe being provided with a liquid into which the liquid in the tank is introduced, the measuring pipe being a measuring pipe. And a measuring thin tube communicating with the measuring tube and located below the measuring tube and having a smaller cross-sectional area than the measuring tube, for measuring the flow rate of the liquid in the measuring thin tube. Is attached to the measuring pipe, and an opening / closing valve is provided in the upper part of the measuring pipe, and after the opening / closing valve is closed for a predetermined time and then opened, the flow rate measured by the sensor is changed. A leak detection device for liquid in a tank, comprising a leak detection means for detecting a leak of liquid in the tank based on an integrated value. 2. The cross-sectional area of the measuring tube is 1/50 or less of the cross-sectional area of the measuring tube.
The leak detection device for liquid in a tank according to. 3. The leak detection device for liquid in a tank according to claim 1, wherein the cross-sectional area of the measuring thin tube is 1/100 or less of the cross-sectional area of the measuring tube. 4. The leak detection device for liquid in a tank according to claim 1, wherein a cross-sectional area of the measuring thin tube is 1/300 or less of a cross-sectional area of the measuring tube. 5. The measuring tube and the measuring thin tube are oriented in a substantially vertical direction.
A leak detection device for liquid in a tank according to any one of 1. 6. The leak detection device for liquid in a tank according to claim 1, wherein the sensor is a thermal flow sensor. 7. The thermal type flow rate sensor comprises a flow rate detecting section and a temperature detecting section, and the leak detecting means temperature-compensates by an electric circuit including the flow rate detecting section and the temperature detecting section. The leak detection device for a liquid in a tank according to claim 6, wherein the already-obtained flow rate value is obtained. 8. The leak detection of the liquid in the tank according to claim 7, wherein each of the flow rate detection unit and the temperature detection unit includes a heat transfer member that is in contact with the outer surface of the measurement thin tube. apparatus. 9. The leak detection device for liquid in a tank according to claim 1, wherein the leak detection means controls opening / closing of the on-off valve. 10. A liquid level height detecting means used to detect the height of the liquid level of the liquid is provided, and the leak detecting means is provided for detecting the flow rate of the liquid measured by the sensor. The integrated value is corrected based on the liquid level height value detected using the liquid level height detection means and the value of the parameter relating to the shape of the tank to obtain a corrected integrated value, and the corrected integrated value is used to obtain the corrected integrated value. The leak detection device for liquid in a tank according to any one of claims 1 to 9, which detects a leak of liquid in the tank. 11. The leak detection device for liquid in a tank according to claim 10, wherein the liquid level detection means is a pressure sensor for detecting a liquid pressure received from the liquid in the tank. 12. The parameter relating to the shape of the tank is the ratio of the effective cross-sectional area of the tank to the cross-sectional area of the measuring pipe at the same height, and the correction integrated value is the liquid level height value in the integrated value. The leak detection device for liquid in a tank according to any one of claims 10 to 11, wherein the leak detection device is obtained by multiplying the value of the parameter. 13. The leak detection means emits a leak detection signal when the integrated value of the flow rate or the corrected integrated value is equal to or more than a predetermined value, according to any one of claims 1 to 12. Leak detection device for liquid in tank. 14. The sensor pipe is formed by passing through a sheath pipe and a sensor holder member attached to a lower portion of the sheath pipe, and the sensor holder holds the sensor. The leak detection device for liquid in a tank according to any one of claims 1 to 13, wherein the measurement thin tube is arranged through a member. 15. A cap member is attached to an upper portion of the sheath tube, and the cap member is provided with a communication passage for communicating the measurement pipe with the outside and a means for fixing the communication pipe to an opening of the tank. 15. The leak detection device for liquid in a tank according to claim 14, wherein the on-off valve is interposed in the communication passage.