JP2006046915A - Apparatus for sensing liquid leakage in tank - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a leakage sensing apparatus of which the sensing precision is hardly reduced even when wind is present in a ground atmosphere in the case that a vent tube is connected to a tank neck part. <P>SOLUTION: The apparatus comprises both a main body part 3 and the neck part 5 connected to its upper part for sensing the leakage of a liquid L from a tank 1, which is housed in the main body part 3 of the tank 1 in which one end of the vent tube 51 is connected to the neck part 5 for communicating with outside. The apparatus includes a measuring capillary tube through which the liquid L in the tank 1 is introduced to and discharged from a lower end, a measuring tube having a larger cross-sectional area than that of the measuring capillary tube and connected to the upper end of the measuring capillary tube, and a flow sensor part attached to the measuring capillary tube for measuring the quantity of flow of the liquid through the measuring capillary tube. The apparatus further includes a communicating hole 17a located inside the tank main body part 3 for making an internal space of the measuring tube and an internal space of the tank 1 outside the measuring tube communicate with each other. The communicating hole 17a is arranged in a region higher than the lower 90% of the capacity of the internal space of the tank main body part 3 and lower than its 100%. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an in-tank liquid leak detection device, and more particularly to an apparatus for detecting a liquid leak from a tank by converting it into a flow based on a liquid level fluctuation of the in-tank liquid.

  Conventionally, most of the fuel oil tanks in underground stations are buried underground. In the underground tank, there is a possibility that a minute crack will eventually occur due to deterioration over time, and oil leakage may occur from there. When such a situation is reached, the surrounding environment is polluted, and the recovery is expensive. For this reason, in such underground fuel oil tanks, it is obliged to periodically detect the presence or absence of oil leaks (or tank cracks that cause them).

  As an apparatus for detecting leakage of liquid in a tank as soon as possible, Japanese Patent Application Laid-Open No. 2003-185522 (Patent Document 1) discloses a measurement tube into which liquid in a tank is introduced, and a measurement thin tube positioned below the measurement tube. And measuring a flow rate of the liquid in the measurement capillary using a sensor unit attached to the measurement capillary, thereby detecting a minute liquid level fluctuation of the liquid in the tank, that is, a change in the liquid level. ing.

  In this leak detection device, an indirectly heated flow meter is used as a sensor attached to the measurement thin tube. In this flow meter, a heating element is heated by energization, a part of the generated heat is absorbed by the liquid, and the effect of this endotherm is taken advantage of the fact that the endothermic amount of the liquid varies depending on the flow rate of the liquid. Detection is based on a change in an electrical characteristic value, for example, a resistance value, due to a temperature change of the temperature sensing element.

  By the way, the underground tank generally includes a main body part for storing liquid and one or a plurality of neck parts attached to an upper part of the main body part and having an opening for communication with the outside. Through these neck openings, piping for injecting liquid into the tank and piping for pumping out liquid from the tank are inserted into the tank. Also, a liquid level gauge for detecting the remaining amount of liquid in the tank is attached to one of these necks. The leak detection device described in Patent Document 1 can have a function of detecting the remaining amount of liquid in the tank. In that case, the leak detection device is attached to the neck where the liquid level gauge is attached instead of the liquid level gauge. The upper end is attached. This leak detection device has a bar shape in which measurement tubes and measurement thin tubes are arranged in series in the vertical direction and extend in the vertical direction, and the lower end portion is positioned slightly above the bottom portion inside the tank main body. The liquid in the tank introduced into the measuring tube through the measuring thin tube forms a liquid level in the measuring tube, and the gas phase in the measuring tube and the gas phase in the tank outside the measuring tube and above the liquid level are separated from each other. A communication hole for communication is formed. The communication hole is conventionally provided at a high position in the tank so that the liquid level of the liquid in the tank does not reach, and is generally located in a neck portion to which the leak detection device is attached.

On the other hand, when the tank is sealed for a long time, the tank has a vent pipe for adjusting the pressure in the tank in order to prevent the pressure inside the tank from rising due to evaporation of the liquid in the tank, etc. Provided. The vent pipe has one end opened in the atmosphere and the other end connected to the tank. The position of the tank to which the vent pipe is connected is often the neck from the viewpoint of reducing the length of the vent pipe. Especially in the case of a tank with a relatively long neck, in most cases the vent pipe is connected to the neck.
JP 2003-185522 A

  However, when the vent pipe is connected to the tank neck as described above, the pressure in the vent pipe fluctuates when there is wind in the atmosphere on the ground, and as a result, a vertical air flow is generated in the tank neck. To do. Therefore, when the communication hole of the leak detection device is located in the tank neck, the influence of the air flow extends into the measurement pipe of the leak detection device through the communication hole, thereby reducing the accuracy of leak detection based on the minute flow measurement. There are things to do. In particular, when the cross-sectional area obtained by subtracting the cross-sectional area of the leak detection device from the cross-sectional area of the tank neck is small, the influence on the deterioration of the leak detection accuracy based on the generation of the airflow is increased.

  Accordingly, an object of the present invention is to provide a leak detection device in which the leak detection accuracy is not easily lowered even when there is a wind in the ground air when the vent pipe is connected to the tank neck.

According to the present invention, the object as described above is achieved.
A tank having a main body and a neck connected to an upper portion of the main body, and having one end of a vent pipe connected to the neck connected to the outside; A device for detecting leakage of
A measuring capillary into which the liquid in the tank is introduced and discharged from the lower end, a measuring pipe connected to the upper end of the measuring capillary and having a larger cross-sectional area than the measuring capillary, and a flow rate of the liquid in the measuring capillary attached to the measuring capillary A flow sensor unit for measuring
A communication hole that communicates the space inside the measurement tube and the space outside the measurement tube and inside the tank is provided, and the communication hole is located in the tank body. , Liquid leak detection device in the tank,
Is provided.

  In one aspect of the present invention, the communication hole is disposed in a region exceeding 90% and less than 100% on the lower side of the capacity of the internal space of the tank main body. In one aspect of the invention, the upper end of the leak detection device is attached to the neck of the tank.

  In one aspect of the present invention, the flow rate sensor unit includes a first temperature sensor, a heater, and a second temperature sensor that are sequentially arranged along the measurement capillary. In one aspect of the present invention, a leakage detection control unit connected to the flow sensor unit is provided, the leakage detection control unit including a voltage generation circuit that applies a voltage to the heater, and the first temperature sensor. And a leak detection circuit connected to the second temperature sensor and generating an output corresponding to a temperature difference sensed by these temperature sensors, and calculated using the output of the leak detection circuit Liquid leakage in the tank is detected based on a flow rate corresponding value corresponding to the liquid flow rate.

  In one aspect of the present invention, the voltage generation circuit is a pulse voltage generation circuit that applies a single pulse voltage to the heater, and the leak detection control unit includes a single pulse to the heater by the pulse voltage generation circuit. The flow rate corresponding value corresponding to the flow rate of the liquid is calculated by integrating the difference between the output of the leak detection circuit and the initial value of the output according to the application of the voltage, and based on this, the leak of the liquid in the tank is calculated. Is detected. In one aspect of the present invention, the voltage generation circuit is a constant voltage generation circuit that applies a constant voltage to the heater.

  In one aspect of the present invention, each of the first temperature sensor and the second temperature sensor includes a heat transfer member that is in contact with the outer surface of the measurement thin tube and a temperature sensing member bonded thereto, The heater includes a heat transfer member in contact with the outer surface of the measurement thin tube and a heating element joined thereto.

  According to the present invention, since the communication hole that communicates the space inside the measurement tube and the space outside the measurement tube and inside the tank is arranged in the tank main body, there is wind in the ground atmosphere, Even if the influence reaches the inside of the tank neck, the influence does not reach the inside of the measurement pipe of the leak detection device through the communication hole, and thus the leak detection accuracy is hardly lowered.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a partially broken perspective view for explaining an embodiment of a leak detection apparatus for liquid in a tank according to the present invention, and FIG. 2 is a partially omitted sectional view of the leak detection apparatus of this embodiment.

  The tank 1 includes a main body 3 that stores a liquid (for example, gasoline, light oil, kerosene, or other flammable liquid) L and necks 5 and 6 that are connected to the upper portion of the main body. Note that LS indicates the liquid level of the liquid L. The tank body 3 includes a vertical cylindrical side plate 33 and a top plate 32 and a bottom plate 34 attached to the side plate so as to close the upper and lower portions thereof. The side plate 3 is formed with a liquid supply port 7 that is used when liquid is supplied from the inside of the tank body 3 to the outside of the tank. The liquid supply port 7 is closed by a lid except when liquid is supplied. When the liquid is pumped from the tank, the lid is opened, and a pipe for liquid supply (pumping) passes through the tank. Is inserted into. The neck portion 6 is provided with a liquid injection port used when pouring liquid into the tank main body portion 3 at the upper end thereof. The liquid injection port is closed by a lid except when liquid is injected, and when the liquid is injected into the tank, the lid is opened and a pipe for liquid injection passes through the tank into the tank. Inserted.

  On the other hand, the neck part 5 is provided with an opening at its upper end. This opening is used as a measuring port, and the upper end portion of the leak detection device according to the present invention is attached to the neck portion 5 so as to close the opening. One end of a vent pipe 51 for communication with the outside is connected to the side wall of the neck portion 5. The other end of the vent pipe 51 is protected from rainwater and opened in the atmosphere.

  The leak detection device 11 is inserted from the neck portion 5 into the tank main body portion 3, and is disposed in the vertical direction as a whole. The leak detection device 11 includes a liquid introduction / extraction section 12, a flow rate measurement section 13, a liquid reservoir section 14, a cap 16, and a circuit housing section 15. The liquid inlet / outlet part 12, the flow rate measuring part 13, and the liquid reservoir 14 are located inside the tank body 1, and the liquid level LS is located within the height range of the liquid reservoir 14. The flow rate measurement unit 13 and the liquid storage unit 14 are configured to include a sheath tube 17 extending in the vertical direction over these.

  As shown in FIG. 2, in the flow rate measuring unit 13, a sensor holder 13 a is disposed in the sheath tube 17, and a vertical measurement capillary 13 b is fixed and held by the sensor holder. A first temperature sensor 133, a heater 135, and a second temperature sensor 134 are arranged and attached to the measurement thin tube 13b in this order from the upper side. The heater 135 is disposed at an equidistant position from the first temperature sensor 133 and the second temperature sensor 134. Since the outer side of the sensor holder 13 a is covered with the sheath tube 17, the first temperature sensor 133, the heater 135, and the second temperature sensor 134 are protected from corrosion by the liquid L. The measurement thin tube 13 b functions as a liquid flow path between the liquid reservoir 14 and the liquid inlet / outlet 12. The first temperature sensor 133, the heater 135, and the second temperature sensor 134 constitute a flow rate sensor unit for measuring the flow rate of the liquid in the measurement thin tube 13b.

  The flow rate measurement unit 13 is provided with a pressure sensor 137 attached to the sensor holder 13a in the vicinity of the lower end of the measurement thin tube 13b. The pressure sensor 137 is for measuring the level of the liquid L in the tank. For example, a piezo element or a capacitor type pressure detection element can be used, and an electric signal corresponding to the liquid level of the liquid, for example, a voltage Output a signal.

  In the liquid introduction / extraction part 12, as shown in FIG. 2, the filter cover 12b fixes the filter 12a to the lower part of the sensor holder 13a. The filter 12a has a function of removing foreign matters such as sludge that floats or settles in the liquid in the tank, and introduces only the liquid into the liquid reservoir 14 through the measurement thin tube 13b. Further, an opening is provided in the side wall of the filter cover 12b, and the liquid L in the tank 1 is introduced into the measurement capillary 13b through the filter 12a of the liquid introduction / extraction part 12.

  The liquid reservoir 14 is located above the flow rate measuring unit 13, has a space G surrounded by the sheath tube 17, and is configured to store the liquid introduced from the measurement thin tube 13 b in this space G. ing. The sheath tube 17 in the liquid reservoir 14 constitutes the measurement tube of the present invention. A cap 16 is fixed to the upper part of the sheath tube 17. A circuit housing portion 15 is attached to the cap 16, and a leak detection control portion 15a is housed in the circuit housing portion. A guide tube Pg extending so as to connect the upper portion of the sensor holder 13a and the cap 16 is disposed in the sheath tube 17, and the first temperature sensor 133, the heater 135, and the second temperature sensor 13 of the flow rate measurement unit 13 are disposed. A wiring 18 that connects the temperature sensor 134, the pressure sensor 137, and the leakage detection control unit 15a extends through the guide tube Pg.

  The cross-sectional area of the measuring thin tube 13b is sufficiently smaller than the cross-sectional area of the sheath tube 17 (excluding the cross-sectional area of the guide tube Pg) (for example, 1/50 or more, 1/100 or less, and further 1/300 times or less). ) By setting it, it is possible to generate a liquid flow that can measure the flow rate in the measurement thin tube 13b even with a slight change in liquid level when a slight liquid leaks.

  In the upper part of the sheath tube 17, a communication hole 17 a is formed for communicating the space G in the liquid reservoir 14 and the tank space outside the detection device. That is, the communication hole 17a communicates the space inside the measurement tube and the space inside the tank 1 outside the measurement tube. The communication hole 17 a is located not in the neck 5 but in the tank body 3. FIG. 2 shows a lower 0 to 90% region (region related to height) R1 and a region R2 exceeding 90% and less than 100% of the capacity of the internal space of the tank body 3. In the present embodiment, the communication hole 17a is located in the region R2. The capacity of the tank 1 is usually referred to as 90% of the total volume of the main body 3, and in the tank 1 is generally up to about 85% of the total volume of the main body 3 for safety. However, the liquid L is accommodated. Therefore, the liquid level LS does not reach the region R2, and the liquid L does not enter or leave the liquid reservoir 14 through the communication hole 17a. However, since the liquid level LS may fluctuate, the communication hole 17a preferably exceeds 91% on the lower side of the capacity of the internal space of the tank body 3 and more preferably exceeds 92%. In particular, it is located in a region exceeding 93%.

  The sheath tube 17, the sensor holder 13a, the filter cover 12b, the cap 16 and the guide tube Pg are preferably made of a metal having a thermal expansion coefficient similar to the material constituting the tank 1, and the tank 1 such as cast iron or stainless steel. More preferably, it is made of the same metal as the material.

  FIG. 3 is an enlarged perspective view of a mounting portion of the first temperature sensor 133, the heater 135, and the second temperature sensor 134 with respect to the measurement thin tube, and FIG. 4 is a sectional view thereof. The heater 135 includes a heat transfer member 181 disposed in contact with the outer surface of the measurement thin tube 13b, and a thin film heating element 182 laminated on the heat transfer member 181 via an electrically insulating thin film. The thin film heating element 182 is formed in a required pattern, and a wiring 182 ′ is connected to an electrode for energizing the thin film heating element 182. The heat transfer member 181 is made of a metal or alloy having a thickness of about 0.2 mm and a width of about 2 mm, for example. The wiring 182 'is connected to a wiring (not shown) formed on the wiring board 24 such as a flexible wiring board. This wiring is connected to the wiring 18 in the guide tube Pg. The heat transfer member 181, the thin film heating element 182, and the wiring 182 ′ are sealed with a sealing member 23 made of a synthetic resin together with a part of the wiring board 24 and a part of the measurement capillary 13 b. The first temperature sensor 133 and the second temperature sensor 134 have the same configuration as the heater 135 except that a thin film temperature sensing element is used instead of the thin film heating element.

  When the leak detection device 11 as described above is attached to the neck portion 5 of the tank 1, the liquid level LS of the liquid L in the tank is located in the region R1 within the height range of the liquid reservoir 14 as described above. . Therefore, the pressure sensor 137 is immersed in the liquid L in the tank filtered by the filter 12a of the liquid introduction / extraction part 12, and the liquid L in the tank rises through the measurement thin tube 13b of the flow rate measurement part 13 and accumulates the liquid. Introduced into the space G of the part 14, the liquid level in the liquid reservoir 14 finally becomes the same height as the liquid level LS of the liquid in the tank outside the leak detection device. Then, when the liquid level LS of the liquid in the tank fluctuates, the liquid level of the liquid in the liquid reservoir 14 also fluctuates, and the liquid flow in the measurement capillary 13b with this liquid level fluctuation, that is, the liquid level change. Will occur.

  FIG. 5 is a diagram showing a circuit configuration of the flow rate sensor unit, the pressure sensor, and the leak detection control unit. As a power source for these circuits, a battery (not shown) arranged in the circuit housing portion 15 can be used.

  The thin film heating element 182 of the heater 135 is connected to the voltage generation circuit 67. In the present embodiment, a pulse voltage generation circuit is used as the voltage generation circuit 67. A single pulse voltage is applied to the thin film heating element 182 from the pulse voltage generation circuit in a timely manner. The thin film temperature detectors 60 and 61 constituting the first and second temperature sensors 133 and 134 are connected to the leak detection circuit 71. That is, the thin film temperature detectors 60 and 61 form a bridge circuit together with the resistors 62 and 63. A power supply voltage V1 is supplied to the bridge circuit, and a voltage output signal corresponding to the potential difference between the points a and b is obtained by the differential amplifier 65. The output of the leak detection circuit 71 corresponds to the temperature difference detected by the thin film temperature detectors 60 and 61 of the temperature sensors 133 and 134 and is input to the CPU 68 via the A / D converter 66. The pulse voltage generation circuit 67 is controlled in accordance with a command from the CPU 68. On the other hand, the output of the pressure sensor 137 is input to the CPU 68 via the A / D converter 73. A clock 69 and a memory 70 are connected to the CPU.

  Hereinafter, the leak detection operation in the present embodiment, that is, the operation of the CPU 68 will be described.

  FIG. 6 is a timing chart showing the relationship between the voltage Q applied from the pulse voltage generation circuit 67 to the thin film heating element 182 and the voltage output S of the leak detection circuit 71. From the CPU 68, based on the clock 69, a single pulse voltage having a width t1 is applied at a predetermined time interval t2. This single pulse voltage has, for example, a pulse width t1 of 2 to 10 seconds and a pulse height Vh of 1.5 to 4V. As a result, the heat generated in the thin film heating element 182 heats the measuring thin tube 13b and the liquid inside thereof, and is transmitted to the surroundings. The influence of this heating reaches the thin film temperature sensors 60 and 61, and the temperature of these thin film temperature sensors changes. Here, when the flow rate of the liquid in the measurement thin tube 13b is zero, the temperature changes in the two temperature sensing bodies 60 and 61 are equal if the contribution of heat transfer by convection is ignored. However, when the liquid level of the liquid in the tank is lowered as when the liquid in the tank leaks from the tank, the liquid is introduced from the liquid reservoir 14 into the tank outside the detection device through the measurement thin tube 13b. 12, the liquid in the measurement capillary 13b flows from top to bottom. As a result, more heat from the thin film heating element 182 is transmitted to the thin film temperature sensing element 61 of the lower temperature sensor 134 than to the thin film temperature sensing element 60 of the upper temperature sensor 133. Thus, there is a difference between the temperatures detected by the two thin film temperature sensors, and the resistance value changes of these thin film temperature sensors are different from each other. FIG. 6 shows changes in the voltage VT1 applied to the thin film temperature sensor 60 of the temperature sensor 133 and the voltage VT2 applied to the thin film temperature sensor 61 of the temperature sensor 134. Thus, the output of the differential amplifier, that is, the voltage output S of the leak detection circuit 71 changes as shown in FIG.

  FIG. 7 shows a specific example of the relationship between the voltage Q applied from the pulse voltage generation circuit 67 to the thin film heating element 182 and the voltage output S of the leak detection circuit 71. In this example, the single pulse voltage has a pulse height Vh of 2 V, a pulse width t1 of 5 seconds, and the liquid level change rate F [mm / h] is changed to obtain a voltage output S [F].

In the CPU 68, in response to the application of the single pulse voltage to the thin film heating element 182 of the heater 135 by the pulse voltage generation circuit 67, the voltage output S of the leak detection circuit and the voltage output S at a predetermined time t3 after the start of the single pulse voltage application. The difference (S ₀ −S) from the initial value (ie, at the start of applying a single pulse voltage) S ₀ is integrated. This integral value ∫ (S ₀ −S) dt corresponds to the hatched area in FIG. 6 and is a flow rate corresponding value corresponding to the flow rate of the liquid in the measurement capillary 13b. The predetermined time t3 is, for example, 20 to 150 seconds.

FIG. 8 shows a specific example of the relationship between the liquid level change rate corresponding to the flow rate F of the liquid in the measurement capillary 13b and the integral value ∫ (S ₀ −S) dt. In this example, the predetermined time t3 for obtaining the integral value is 30 seconds, and relationships at three different temperatures are obtained. It can be seen that in a region where the liquid level change rate is 1.5 mm / h or less, there is a good linear relationship between the liquid level change rate and the integral value ∫ (S ₀ -S) dt regardless of the temperature. In this example, a good linear relationship was shown in the region where the liquid level change rate was 1.5 mm / h or less. By doing so, it is possible to obtain a good linear relationship in a region where the liquid level change rate is 20 mm / h or less.

Such a typical relationship between the integral value ∫ (S ₀ -S) dt and the liquid level change speed can be stored in the memory 70 in advance. Therefore, based on the integral value ∫ (S ₀ −S) dt which is a flow rate corresponding value calculated using the output of the leak detection circuit 71, conversion is performed with reference to the stored contents of the memory 70, thereby converting the liquid in the tank. Leakage can be obtained as the liquid level change rate. However, when a liquid level change rate smaller than a certain value (for example, 0.01 mm / h) is obtained, it can be determined that there is no leakage, considering that it is within the measurement error range.

  This first leak detection is repeatedly performed at an appropriate time interval t2. The time t2 is, for example, 40 seconds to 5 minutes (however, a time longer than the integration time t3).

  Further, the CPU 68 can immediately convert the liquid level corresponding output P input from the pressure sensor 137 via the A / D converter 73 into the liquid level p. The value of the liquid level p is based on the height of the pressure sensor 137. The height of the measuring port 5 of the tank 1 and the distance from the attachment portion of the leak detection device to the measuring port to the pressure sensor 137 Can be converted into a liquid level value for the tank itself. A liquid level detection signal indicating the result of the liquid level detection is output from the CPU 68.

  Further, the CPU 68 stores the value of the liquid level p in the memory 70 every predetermined time tt, for example, every 2 to 10 seconds, and calculates the difference from the previous stored value every time this storage is performed. The change rate p ′ is stored in the memory 70 as a value.

  FIG. 9 shows a specific example of the relationship between the liquid level change rate and the time change rate P ′ of the liquid level corresponding output P. In the region where the liquid level change rate is 150 mm / h or less, there is a good linear relationship between the liquid level change speed and the time change rate P ′ of the liquid level corresponding output, and therefore the liquid level change rate and the liquid level time change rate. It can be seen that p ′ corresponds well. In this example, a good linear relationship was shown in the region where the liquid level change rate was 150 mm / h or less. However, a good linear relationship was obtained in the region up to the liquid level change rate of 200 mm / h. It is possible.

  Therefore, the leakage of the liquid in the tank can be obtained as the magnitude of the time change rate p ′ of the liquid level p measured by the pressure sensor 137.

  This second leak detection can cover a wider liquid level change speed range than the first leak detection. On the other hand, the first leak detection can measure a minute liquid level change speed region with higher accuracy than the second leak detection.

  By the way, the liquid level change in the tank 1 also occurs when liquid is injected from the liquid injection port of the neck 6 into the tank 1 or when liquid is supplied from the liquid supply port 7 to the outside. However, the rising or lowering speed of the liquid level in the tank 1 in these cases is generally much larger than the liquid level change rate or the liquid level time change rate in the case of leakage.

  Therefore, the CPU 68 performs the following processing regarding leakage.

  (1) When the level of the liquid level time change rate p ′ is within a predetermined range (for example, 10 to 100 mm / h) in the second leak detection, the result of the second leak detection is output as a leak detection signal.

  (2) When the level of the liquid level time change rate p ′ is smaller than the lower limit of the predetermined range (for example, smaller than 10 mm / h) in the second leak detection, the result of the first leak detection is output as a leak detection signal. To do.

  (3) In the second leak detection, when the level of the liquid level time change rate p ′ exceeds the upper limit of the predetermined range (for example, greater than 100 mm / h), a cause other than the leak, for example, liquid injection or liquid supply Judgment and no leak detection signal is output.

  Further, in the present embodiment, when the state (3) is reached, that is, when the level of the liquid level time change rate p ′ exceeds the upper limit of the predetermined range in the second leak detection, the CPU 68 The first leak detection can be stopped for a predetermined time tm. The predetermined time tm for stopping the leakage detection is preferably a time slightly longer than the settling time of the liquid level LS after the liquid is injected from the outside into the tank or the liquid is supplied from the inside to the outside. It can be 10 to 60 minutes. In particular, during this predetermined time tm, the CPU 68 can stop the operations of the pulse voltage generation circuit 67 and the leak detection circuit 71. According to this, power consumption is reduced.

  The liquid level change rate or the liquid level time change rate is related to the leak amount (leak amount per unit time). That is, the liquid level change rate or the liquid level time change rate multiplied by the horizontal sectional area inside the tank at the liquid level corresponds to the liquid leakage amount. Therefore, the shape of the tank (that is, the relationship between the height position and the horizontal cross-sectional area inside the tank) is stored in the memory 70 in advance, and the liquid detected as described above with reference to the stored contents of the memory. The amount of leakage of the liquid in the tank can be calculated based on the position and leakage (liquid level change rate or liquid level time change rate).

  When the tank has a constant horizontal cross-sectional area regardless of the height, such as the vertical cylindrical shape shown in FIG. 1, the liquid level change rate or the liquid level time change rate The amount of leakage is simply proportional, so it is easy to multiply the liquid level change rate or liquid level time change rate by the proportional constant according to the horizontal cross-sectional area inside the tank regardless of the liquid level value itself. The amount of leakage can be calculated. That is, in this case, the leakage detected by the above-described device of the present invention is substantially equivalent to that based on the leakage amount.

  In the case of the above leak detection, if there is a wind in the ground air, the influence will reach the tank neck 5. That is, a gas flow that flows from the tank 1 to the outside atmosphere or a gas flow that flows from the outside atmosphere to the tank 1 may occur in the vent pipe 51 due to the wind pressure. Under the influence of this gas flow, gas flow also occurs in the space outside the leak detection device 11 in the neck portion 5. The speed of this gas flow increases as the cross-sectional area obtained by subtracting the cross-sectional area of the leak detection device 11 from the cross-sectional area of the neck portion 5 decreases. However, in this embodiment, since the communication hole 17a formed in the sheath tube 17 of the leak detection device 11 is located not in the neck portion 5 but in the tank body portion 3, there is a gas flow around the communication hole 17a. There is a large space, so the rate of gas flow is very small. Thus, in the present embodiment, the influence of the gas flow in the space in the neck portion 5, that is, the change in atmospheric pressure hardly reaches the space G in the sheath tube 17 through the communication hole 17a, and the leak detection accuracy is maintained well. The In order to enhance such an action, the communication hole 17a is preferably located in a region of less than 99%, more preferably less than 98%, particularly less than 97% on the lower side of the capacity of the internal space of the tank body 3. To do.

  In the above description, it is assumed that the liquid supply port 7 is formed in the side plate 33 of the tank main body 3. However, when the tank 1 is an underground tank, the liquid supply port is used for the convenience of pumping out the liquid from the tank. A mouth can be provided in the top plate 32. Moreover, it is also possible to share the opening of the neck 6 for the liquid supply port and the liquid injection port.

  FIG. 10 is a schematic cross-sectional view for explaining still another embodiment of the tank liquid leakage detection device according to the present invention. In this figure, the same code | symbol is attached | subjected to the member or part etc. which have the function similar to the said FIGS. 1-9.

  In this embodiment, the tank 1 is an underground tank, and the main body 3 has a horizontal cylindrical shape. The neck 5 of the tank 1 is located in a cavity formed in the ground, and the cavity is closed by a manhole 100. The communication hole 17 a of the leak detection device 11 is located in the region R <b> 2 of the tank body 3. Further, in the present embodiment, a constant voltage generation circuit that applies a constant voltage (that is, a constant DC voltage) to the heater 135 is used as the voltage generation circuit 67 of FIG. A DC constant voltage Q is applied to the thin film heating element 182. Thereby, the heater 135 maintains a constant heat generation state, and a part of the heat is transmitted to the liquid in the measurement capillary 13b via the heat transfer member 181 and is used as a heat source for heating the liquid.

  When the liquid in the measurement thin tube 13b is not flowing, that is, when the flow rate of the liquid in the measurement thin tube 13b is zero, the first and second temperature sensors 133 are ignored if the contribution of heat transfer by convection is ignored. , 134 are substantially the same. However, when the liquid flow occurs in the measurement thin tube 13b, the influence of the liquid heating by the heater 135 is generated more strongly on the downstream side than on the upstream side, so that the detected temperatures of the first and second temperature sensors 133 and 134 are mutually different. To be different. Since the voltage output corresponding to the difference between the detected temperatures of the first and second temperature sensors 133 and 134 corresponds to the fluid flow rate, it is used as the flow rate value output. That is, the potentials at points a and b of the bridge circuit of the leak detection circuit 71 are input to the differential amplifier circuit 65. By appropriately setting the resistance values of the resistors 62 and 63 of the bridge circuit in advance, a voltage output S corresponding to the difference between the detected temperatures of the first and second temperature sensors 133 and 134 is obtained from the differential amplifier circuit. Can do.

  As described above, the two-point temperature difference detection type flow rate measurement is performed. In the present invention, the two-point temperature difference detection type flow rate measurement is a temperature difference (actually corresponding to the detected temperature difference) detected by the first and second temperature sensors respectively arranged on the upstream side and the downstream side of the heater. The value corresponding to the flow rate is obtained based on the difference in the electrical characteristics detected.

  Next, the leak detection operation in this embodiment, that is, the operation of the CPU 68 will be described. The operation of the CPU 68 of this embodiment is different from that of the embodiment described above with reference to FIGS. 1 to 9 only in the first leak detection operation, and the other operations are the same.

  That is, the CPU 68 performs conversion into a corresponding flow rate value using a built-in calibration curve based on the voltage output S. FIG. 11 shows an example of a calibration curve for S conversion. As shown in FIG. 11, in a region where the liquid level change rate corresponding to the flow rate value is smaller than 10 mm / h, for example, there is a good linear correspondence between the liquid level change rate and the voltage output S. . Therefore, the CPU 68 can perform processing similar to that of the embodiment described with reference to FIGS.

  Note that the two-point temperature difference detection type flow rate measurement used in the present embodiment may be used in place of the single pulse heat generation type flow rate measurement in the embodiment described with reference to FIGS. 10 to 11, instead of the two-point temperature difference detection type flow rate measurement, the single pulse heating type flow rate measurement used in the present embodiment described with reference to FIGS. 1 to 9 is used. May be.

  The present embodiment has an advantage that the calculation for obtaining the flow rate corresponding value in the first leak detection by the CPU 68 becomes simpler than the embodiment described with reference to FIGS.

  FIG. 12A shows the results of an example in which the speed of change of the liquid level LS (liquid level change speed) was measured using the apparatus of the present embodiment under conditions without actual liquid leakage. The tank 1 used had a capacity of 10 kiloliters, and about 5 kiloliters of kerosene was used as the liquid L. The communication hole 17 a is provided at a lower 98% height position of the capacity of the internal space of the tank body 3. When the liquid level change rate is a positive value, it indicates that the liquid level has increased, and when the liquid level change rate is a negative value, it indicates that the liquid level has decreased. FIG. 12B shows the result of a comparative example using the same device as in the above embodiment except that the communication hole is provided at the central height position of the tank neck. From comparison between (a) and (b) of FIG. 12, the apparatus according to the embodiment of the present invention has less fluctuation in the liquid level change rate than the comparative example, and therefore, stable measurement with less error is possible. I understand that.

It is a partially broken perspective view for demonstrating one Embodiment of the leak detection apparatus of the liquid in a tank by this invention. FIG. 2 is a partially omitted cross-sectional view of the leak detection device of the embodiment of FIG. 1. It is an expansion perspective view of the attachment part of the 1st temperature sensor with respect to a measurement thin tube, a heater, and a 2nd temperature sensor. FIG. 4 is a cross-sectional view of FIG. 3. It is a figure which shows the circuit structure of a flow sensor part, a pressure sensor, and a leak detection control part. It is a timing diagram which shows the relationship between the voltage Q applied to a thin film heating element, and the voltage output S of a leak detection circuit. It is a figure which shows the specific example of the relationship between the voltage Q applied to the thin film heating element, and the voltage output S of a leak detection circuit. It is a diagram showing a specific example of the relationship between liquid level change rate and the integral value ∫ (S 0 _-S) dt. It is a figure which shows the specific example of the relationship between a liquid level change speed and the time change rate P 'of a liquid level corresponding | compatible output. It is a typical sectional view for explaining one embodiment of the leak detection device of the liquid in a tank by the present invention. It is a figure which shows an example of the calibration curve for conversion of the voltage output S of a leak detection circuit. It is a figure which shows the result of the Example which measured the liquid level change speed in a tank using the leak detection apparatus of the liquid in a tank by this invention, and the comparative example with respect to it.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tank 3 Tank main-body part 32 Top plate 33 Side plate 34 Bottom plate 5,6 Tank neck part 7 Liquid supply port L Liquid LS Liquid surface 11 Leak detector 12 Liquid introduction / extraction part 12a Filter 12b Filter cover 13 Flow rate measurement part 13a Sensor holder 13b Measurement Narrow tube 133 First temperature sensor 134 Second temperature sensor 135 Heater 137 Pressure sensor 14 Liquid reservoir G Space 15 Circuit accommodating portion 15a Leak detection control portion 16 Cap 16a Air passage 17 Sheath tube 17a Communication hole R1, R2 region Pg guide Tube 18 Wiring 181 Heat transfer member 182 Thin film heating element 182 'Wiring 23 Sealing member 24 Wiring board 51 Ventilation tube 60, 61 Thin film temperature sensing element 62, 63 Resistor 65 Differential amplifier 66 A / D converter 67 Voltage generation circuit 68 CPU
69 Clock 70 Memory 71 Leak Detection Circuit 73 A / D Converter

Claims (8)

A tank having a main body and a neck connected to an upper portion of the main body, and having one end of a vent pipe connected to the neck connected to the outside; A device for detecting leakage of
A measuring capillary into which the liquid in the tank is introduced and discharged from the lower end, a measuring tube connected to the upper end of the measuring capillary and having a larger cross-sectional area than the measuring capillary, and a flow rate of the liquid in the measuring capillary attached to the measuring capillary A flow sensor unit for measuring
A communication hole that communicates the space inside the measurement tube and the space outside the measurement tube and inside the tank is provided, and the communication hole is located in the tank body. , Liquid leak detection device in the tank. 2. The inside of the tank according to claim 1, wherein the communication hole is disposed in a region that is lower than 90% and less than 100% of the capacity of the internal space of the tank main body. Liquid leak detection device. 3. The leak detection device for liquid in a tank according to claim 1, wherein an upper end portion of the leak detection device is attached to a neck portion of the tank. The said flow sensor part comprises the 1st temperature sensor, heater, and 2nd temperature sensor which are arrange | positioned in order along the said measurement thin tube, The one in any one of Claims 1-3 characterized by the above-mentioned. Tank leak detection device. A leakage detection control unit connected to the flow rate sensor unit, the leakage detection control unit being connected to a voltage generation circuit for applying a voltage to the heater, the first temperature sensor, and the second temperature sensor; And a leak detection circuit that generates an output corresponding to a temperature difference sensed by these temperature sensors, and corresponding to the flow rate of the liquid calculated using the output of the leak detection circuit 5. The tank liquid leakage detection device according to claim 4, wherein leakage of the liquid in the tank is detected based on a value. The voltage generation circuit is a pulse voltage generation circuit that applies a single pulse voltage to the heater, and the leak detection control unit is configured to apply the leak according to the application of the single pulse voltage to the heater by the pulse voltage generation circuit. The flow rate corresponding value corresponding to the flow rate of the liquid is calculated by integrating the difference between the output of the detection circuit and the initial value of the output, and based on this, leakage of the liquid in the tank is detected. The tank leak detection device according to claim 5. 6. The tank liquid leakage detection device according to claim 5, wherein the voltage generation circuit is a constant voltage generation circuit that applies a constant voltage to the heater. Each of the first temperature sensor and the second temperature sensor includes a heat transfer member in contact with the outer surface of the measurement thin tube and a temperature sensing member joined thereto, and the heater includes an outer surface of the measurement thin tube. The in-tank liquid leak detection device according to any one of claims 4 to 7, further comprising a heat transfer member in contact with the heating element and a heating element joined thereto.

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