JP2005098894A - Leak detection system for liquid storage tank - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a leakage detection system for a liquid storage tank, having high accuracy. <P>SOLUTION: The leakage detection system for a liquid storage tank is provided with a decompression pump decompressing the inside of a tank decompression; a pressure gauge measuring the pressure in a tank; a probe arranging an underwater sound detector or an underwater microphone in the lower liquid phase part, a water gauge in the upper gas phase part, and a sediment clearance implement in the bottom end; an acoustic analysis device analyzing sound information of the underwater sound detector or the underwater microphone, and the frequency for acquiring leakage determining data; and a control device controlling the whole system, storing, analyzing and determining the above data. The system comprises a decompression means decompressing the inside of a tank with the decompression pump to a predetermined pressure 1, a first determining means and analyses means determining the presence of leakage and its degree of incidence from the water level of the water gauge, and the data of the acoustic analysis device, and a second determining means judging the presence of leakage from the pressure change in a tank. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a leakage inspection method for liquid storage tanks, particularly liquid underground storage tanks such as gasoline, heavy oil, light oil, kerosene, and solvents that are substantially immiscible with water.

In factories that store organic liquids such as oils and solvents in underground tanks and storage stations such as gas stations, in order to prevent soil contamination, fire accidents, etc. due to leakage of contents from underground tanks, It is instructed to regularly check underground tanks for leak inspections based on “material notifications”.
As a detector for detecting leakage, 1) a gas detector for detecting a vaporized liquid that has leaked, 2) a dielectric detector using a dielectric that deteriorates insulation properties when touching the leaked liquid, 3) Pressure gauge to detect pressure fluctuation in tank due to leakage, 4) Water detector to detect ingress of groundwater into tank due to leakage, 5) Acoustic sound of air and water intrusion into tank due to leakage There are several methods and systems for detecting leaks in underground storage tanks that combine one type or a plurality of types.

Among these detectors, 1) gas detectors, 2) dielectric detectors, these detectors are arranged around the tank in advance, and the tank contents leaking outside the tank are detected to detect leakage. Mainly used in detecting systems. For example, a system has been proposed in which information on a gas detector provided around a gasoline tank is displayed on a display unit of a liquid level gauge indicating the amount of storage in the gasoline tank, and the leakage of the tank is monitored (for example, patent document) 1 and 2). In addition, a dielectric detector that surrounds a tank that stores petroleum products is surrounded by a dielectric detector that uses an insulator that deteriorates insulative properties when shaken to the petroleum product. If a petroleum product leaks from the tank, the dielectric detector surrounds the tank. There is also a method of detecting the leakage of the tank from the change in the electrical characteristics of the deterioration of the insulating properties (for example, see Patent Documents 3 and 4).
However, all of these methods require that a plurality of detectors be installed in advance when constructing the tank, which increases the construction cost of the tank, and of course, a general liquid without such equipment. It cannot be used for leak inspection of storage tanks.

On the other hand, among the above detectors, 3) pressure gauge, 4) water detector, and 5) acoustic detector do not always need to be installed in the tank, and are mainly inserted into the tank during periodic leak inspections. And use it.
In such periodic underground liquid storage tank leakage inspection, the inside of the tank is sealed by pressurizing or depressurizing, and the method of judging the presence or absence of leakage from the change in the pressure, or the inside of the tank is depressurized, A method is used in which whether air or groundwater enters from the outside of the tank is detected to determine the presence or absence of leakage.
When pressurizing the tank, if there is a leak in the tank, the contents will be pushed out of the tank and the contamination will spread.For example, after all the oil in the tank has been drained, Pressurize and stop the pressurization at a predetermined test pressure and measure the pressure fluctuation within a certain period of time, or remove all the oil from the tank and add an inert gas. A gas pressurization test is performed in which pressurization is stopped at a predetermined test pressure and pressure fluctuation within a predetermined time is measured. However, these methods have a problem that the liquid in the tank must be once extracted and stored, which causes time and cost.

  Therefore, even if there is a leak by slightly pressurizing or depressurizing the inside of the tank, in order to prevent a large amount of tank contents from leaking in the pressurization test, a fine pressurization is performed without taking out the liquid in the tank. A micro decompression test method has been proposed (see, for example, Patent Document 5). According to this, when the change of the pressure of the tank sealed by pressurizing or depressurizing to a predetermined pressure is faster than the change when there is no leak set according to the tank, it is determined that there is a leak. However, this method has a problem in that the tank contents leak out of the tank if there is a leak if the pressure is applied even if it is slightly pressurized. In the case of slight decompression, there is no problem if air enters from the leaked part of the tank, but if water enters, as in the case where there is a leaked part below the groundwater level, the pressure due to the leak There is a problem that detection is extremely difficult to detect, and the reliability of leakage determination is low.

  There has been proposed a method of collecting an intake sound that is sucked into the tank from the outside after the tank is depressurized or a sound that becomes bubbles in the liquid [see, for example, Patent Document 6]. However, this method can detect leakage when air enters, but there is no disclosure of a specific method when water enters. Therefore, there is a problem that leakage cannot be detected when water enters, as in the case where there is a leakage point below the groundwater level.

  In addition to collecting the intake sound that is sucked into the tank from the outside or the sound of bubbles in the liquid as in the case of the above-mentioned Patent Document 6, a means for detecting leakage by pressure change in the tank is added. Furthermore, a method for detecting leakage using a water level meter has also been proposed for water intrusion [see, for example, Patent Document 7]. However, with this method, even if a leak can be detected, the magnitude of the leak is not quantified. If a leak is detected, it is natural to repair the leak, but if the size of the leak or whether the size meets the standards stipulated by laws and regulations cannot be determined, the urgency of countermeasures Cannot be judged. In addition, there is a problem that the leak detection procedure is not systematic and the determination of leak is left to human judgment.

  There has also been proposed a tank having a double wall structure that reduces the possibility of leakage (see, for example, Patent Document 8). In such a double-structured tank, if the inner shell leaks, the liquid in the contents leaks into the gap between the inner shell and outer shell, and if there is a leak in the outer shell, the groundwater around the tank It penetrates into the gap between the inner and outer shells. Such intrusion of liquid into the gap between the inner shell and outer shell is detected by a liquid level gauge using a float to detect leakage. Such a tank has a problem that the manufacturing cost becomes extremely high.

Japanese Unexamined Patent Publication No. 64-84896 JP 2000-85896 A Japanese Patent Application Laid-Open No. 62-182091 JP-T 6-503178 JP-A-8-108398 JP 59-170739 US patent USP 5,319,956 JP-A-8-327489

  The problem to be solved by the present invention is that a liquid storage tank leak inspection system is capable of detecting a leak location in any position of a liquid storage underground tank buried in any place with a high degree of detection accuracy and to the extent of leakage. Is to propose.

A leak detection system for a liquid storage tank according to the present invention includes a decompression pump for depressurizing a gas phase part in a tank that stores a substantially water-insoluble liquid containing a volatile component, and a liquid in the lower part of the tank. Collected by a hydrophone or microphone with a hydrophone or microphone and water level meter in the phase section, and a probe with a pressure gauge that measures the pressure of the gas phase section in the tank above the gas phase section and the hydrophone or microphone The sound information is converted into leakage judgment acoustic data, the frequency is analyzed and converted into leakage location size evaluation data, the control of the entire system, and the water level sent from the probe water gauge Control for recording, analyzing, and judging data, pressure data sent from a pressure gauge, acoustic data for leak judgment sent from the acoustic analysis device, and leak location size evaluation data A leak detection system of the liquid storage tank comprising a location, a,
(1) The suction port of the vacuum pump is connected to the upper gas phase in the tank, and the tank is configured to be airtight,
(2) Based on the pressure data, the control device operates the pressure reducing pump until the inside of the tank is depressurized to a predetermined first pressure, and stops the pressure reducing pump when the first pressure is reached. Decompression control means; recording the leakage determination acoustic data by the acoustic analyzer and the water level water level data while the decompression pump is stopped, and recording the leakage determination acoustic data and the water level data And a first determination means for determining whether or not there is a leak; if it is determined in the first determination that there is a leak, the leak location size evaluation data indicates the location of the leak An analysis means for analyzing the size; when there is a leak in the gas due to the vaporization of the liquid in the tank when the decompression pump is stopped, the air or water entering the tank due to the leak is On the other hand, when the pressure rises to the predetermined second pressure, the time required for the pressure increase from the first pressure to the second pressure is recorded, and the pressure reducing pump is operated to move the inside of the tank to the predetermined pressure. When the pressure is reduced to the first pressure, the pressure reducing pump is stopped, and when the pressure is increased to the second pressure, the pressure is reduced to the first pressure. A second determination means for comparing the record of the time required with a predetermined leakage determination criterion and determining whether there is a leakage;
It is characterized by having.

  In addition, the probe is provided with a sediment removing tool at the tip, and is configured to be able to perform an operation of removing the sediment on the bottom surface of the tank before being installed in the tank.

  Further, the determination of the presence or absence of leakage by the leakage determination acoustic data performed by the first determination means is performed by converting sound information collected by the hydrophone or microphone into leakage determination acoustic data in the acoustic analyzer. The air that enters the tank from the outside through the leaked part in the gas phase part or the liquid phase part in the tank stored in advance in the control unit, or in the liquid by the infiltration sound of water or the infiltration of air. It is determined whether or not it coincides with any of the sound data corresponding to the sound of bubbles generated in the water or the dripping sound of water falling on the liquid surface. .

  Further, the determination of the presence or absence of leakage based on the water level data made by the first determination means is realized by determining whether or not the water level is rising due to water entering the tank from the outside. To do.

  Further, the determination of the presence or absence of leakage by recording the time required for the pressure in the gas phase portion to increase made by the second determination means is reduced to the first pressure when the pressure increases to the second pressure. The change in time required for the increase from the first pressure to the second pressure is compared with the change in time when there is a leak stored in the control unit in advance. If it is determined that they are the same, it is determined that there is a leak.

  Further, the leak location size evaluation data used for analyzing the size of the leak location made by the analyzing means is a frequency distribution of sound information collected by the hydrophone or microphone, and this is used as a control unit. The size of the leaking part is calculated by collating with the correspondence data of the frequency distribution stored in advance and the size of the leaking part.

  In the liquid storage tank leakage inspection system according to the present invention, the pressure of the tank is reduced, and the intrusion sound of air or water entering from the outside of the tank through the leakage portion is detected to determine whether the tank is leaking. In order to detect the intrusion sound, a high-sensitivity hydrophone or microphone is installed in the liquid phase part, so that the leak point is naturally in the liquid phase part of the tank, but also in the gas phase part. It can be detected, and it can be detected even if the leak point is above the ground water surface outside the tank (air enters) or below (water enters). In addition, it has means for analyzing the frequency of the intrusion sound and estimating the size of the leaked portion, so that the urgency of the leakage countermeasure can be determined. Furthermore, independent of the detection of the intrusion sound of air or water, there is provided means for detecting leakage by measuring the amount of water entering the tank with a water level meter, and means for detecting leakage from fluctuations in pressure in the tank. By performing double leak detection, highly reliable test results can be obtained.

A liquid storage tank leakage inspection system according to the present invention will be described with reference to the drawings.
FIG. 1 is a configuration diagram of a liquid storage tank leakage inspection system according to the present invention. A liquid 2 that is substantially insoluble in water is stored in the tank 1, and a gas phase portion 4 that is not filled with a liquid is provided above the liquid surface 3. The amount of storage in the liquid phase part 2 is 60 to 90% of the tank capacity when the capacity of the tank 1 is about 280 kiloliters or less, and 5 to 95% when the capacity is about 110 kiloliters or less. It is desirable from the aspect of accuracy. A suction port of a decompression pump 7 is connected to an exhaust port 5 on the upper surface (gas phase portion) of the tank 1 via a connection pipe 6.

  The probe 9 is inserted into the tank from the probe insertion port 8 on the upper surface of the tank 1 so that the airtightness of the insertion port 8 is maintained. The probe 9 is provided with a water level gauge 10 and a hydrophone or a microphone 11 at a tip portion that is in contact with the bottom surface of the tank and is located in the liquid phase portion 2. In addition, a pressure gauge 13 is provided in the upper part located in the gas phase part 4. It is preferable that the tip of the probe 9 is provided with a sediment removing tool for removing the sediment on the bottom surface of the tank. And when attaching a probe to a tank, a probe is rotated and a deposit removal tool is rotated, A deposit is removed. This is because conductive or sticky sludge, such as metal powder, often settles at the bottom of the tank, which prevents the water level gauge from malfunctioning due to adhesion to the probe.

FIG. 2 is an explanatory view showing the structure of the tip of the probe. As shown in FIG. 2, a precipitate removing tool 64 having a brush shape made of a shape memory metal or shape memory plastic thin wire having a rounded tip and curved toward the central axis of the cylindrical probe is a tip of the probe 9. Is attached.
FIG. 2 shows a water level meter 10 used in this embodiment. A plurality of conductive electrodes 61 each having a predetermined length are formed on a plastic plate-like substrate 60. When the electrical resistance between two adjacent electrodes is sequentially measured, the resistance decreases when immersed in water, so it is possible to determine how far it has been immersed in water. When the leak detection inspection is performed, the probe 9 is attached to the tank so that the front end surface 62 of the substrate 60 is in contact with the bottom surface of the tank.

The water level meter 10 measures the water level of the water 14 accumulated under the liquid phase part 2 and sends the water level data 15 to the control device 16.
The hydrophone or microphone 11 collects the sound of the liquid phase part 2 and the gas phase part 4 and sends it to the acoustic analysis unit 17, and the acoustic analysis unit 17 uses the hydrophone or the microphone 11 to detect the sound captured by the hydrophone or the microphone 11. And is sent to the control device 16 as acoustic data 18, and frequency-analyzed and converted into leak location size evaluation data, and sent to the control device 16 as leak size data 19.
The acoustic analysis unit 17 includes a speaker or headphones for monitoring the sound captured by the hydrophone or the microphone 11, a cassette recorder (none of which is shown) for recording the sound, and the like. Usually, the sound captured by the hydrophone or the microphone 11 is recorded and stored.
The pressure gauge 13 measures the pressure in the gas phase section 4 and sends pressure data 20 to the control device 16.
The pump operation switch 21 operates to operate the decompression pump 7 with an ON signal 22 sent from the control device 16 and stop the decompression pump 7 with an OFF signal 50.

  The control device 16 is a normal personal computer including a data processing device 23, a storage device 24, an input / output device 25, a monitor screen 26, a printer 27, and the like. In the storage device 24, the basic sound entry pattern 28 of the acoustic data 18 corresponding to the intrusion sound of water or air entering the tank through the leak location of the tank in any case, the relationship between the frequency of the intrusion sound and the size of the leak location. A frequency table 29 showing a first pressure 30 for stopping the pressure reducing pump 7 when the pressure is reduced to the pressure, a second pressure 31 for operating the pressure reducing pump when the pressure is increased, and a change in time when the pressure reducing pump is stopped. The pressure change pattern 32 indicating the relationship between this pattern and the presence or absence of tank leakage is stored. Alternatively, data stored in these storage devices may be input from a floppy disk or the like via the input / output device 25. In addition, all of the setting conditions, acquired data, determination results, etc. relating to a series of leak detection inspections are displayed on the monitor screen 26, printed by the printer 27, stored on a recording medium such as a flexible disk, and taken out, or the input / output device 25. It is also possible to send data to a management source via the Internet via the Internet and to centrally manage the data at a remote location.

Next, a flow for inspecting the liquid storage tank for leakage using the above system will be described.
FIG. 3 shows a flow for inspecting the liquid storage tank for leaks. First, all the stoppers leading to the tank 1 are closed to ensure airtightness of the tank. Thereafter, the tank 1 is depressurized by the depressurization control means. That is, when an inspection start button (not shown) of the control device 16 is pressed, an ON signal 22 is sent from the control device 16 to the pump operation switch 21, the pump 7 is operated, and the tank 1 is depressurized. When the pressure data 20 measured by the pressure gauge 13 reaches the first pressure 30 stored in the storage device 24 of the control device, an OFF signal 23 is sent from the control device 16 to the pump operation switch 21, and the decompression pump 7 Stop.
It is desirable that the first pressure 30 is set as low as possible within the pressure range where air or water from the leaked portion enters a substantially measurable amount in order to reduce the strength burden that leads to damage to the tank. . For example, in the case of a steel tank, -6.9 KPa, in the case of a reinforced plastic (FRP), or in the case of a diameter of 2.43 m or more, it is -3.4 KPa even if it is made of steel.

  In the state where the decompression pump 7 is stopped and the operation sound, exhaust sound, and vibration of the decompression pump 7 are eliminated, the presence or absence of leakage is determined by the first determination means. That is, the acoustic data 18 obtained by converting the sound captured by the hydrophone or the microphone 11 into the leakage determination acoustic data by the acoustic analysis unit 17 and the intrusion sound basic pattern 28 stored in the storage device 24 of the control device 16, respectively. The data processing device 23 compares and determines that there is a leak if they match. The basic pattern of intrusion sound is the air that enters the tank from the outside through the leak point in the gas phase part or liquid phase part of the tank, or the sound of water intrusion or the sound of bubbles generated in the liquid due to the ingress of air. Or acoustic data corresponding to a dripping sound or the like in which water falls on the liquid surface.

  Further, if there is an increase in the water level in the water level data 15, it is determined that there is a leak even if it is determined that there is no leak in the comparison inspection with the intrusion sound basic pattern. This is because when water enters the liquid phase portion 2 of the tank 1, the intrusion sound may be difficult to detect, and the water level data is more reliable. For example, when water enters from a leaking point with a diameter of 0.3 mm, the water level rises by 0.8 mm (increase rate of 0.07 mm / min) in 12 minutes, and when the diameter is 0.2 mm, the water level increases by 1 in 56 minutes. If the water pressure outside the tank is the same, the rising speed of the water level is roughly proportional to the area of the leaking part.

  If it is determined that there is a leak, the size of the leaked portion is analyzed by the analyzing means. The leakage magnitude data 19 is data obtained by frequency analysis of the sound captured by the hydrophone or the microphone 11 by the acoustic analysis unit 17, and is compared with the frequency table 29 stored in the storage device 24 by the data processing device 23. Calculate the size of the leak location. The frequency table 28 is a correspondence table between the frequency and the size of the leaked part. For example, when the leaked part exists in the liquid phase part 2 and air enters from there and bubbles are generated, the frequency of the intruding sound is shown. The diameter of the leak location is 6000 Hz at 0.07 mm and 800 Hz at 1.2 mm, and the frequency increases as the leak location becomes smaller. Therefore, it is impossible to detect a leaked portion with a human ear, and analysis by a device such as the acoustic analysis unit 17 of the present invention is indispensable.

  When the decompression pump 7 is stopped, the liquid in the tank is vaporized into a gas, so that the pressure in the tank gradually increases. When there is a leak in the tank, air or water entering from outside the tank is added, and the pressure increase is accelerated. When the pressure data 20 measured by the pressure gauge 13 reaches the second pressure 31, the time required for the pressure to rise from the first pressure to the second pressure is stored in the storage device 24. Then, the ON signal 22 is sent from the control device 16 to the pump operation switch 21 by the depressurization control means, the pump 7 is operated again, and the tank 1 is depressurized. When the pressure data 20 measured by the pressure gauge 13 reaches the first pressure 30 stored in the storage device 24 of the control device, an OFF signal 23 is sent from the control device 16 to the pump operation switch 21, and the decompression pump 7 Stop.

When the pressure reducing pump is stopped by the control device 16 and the pressure rises to the second pressure, the time required for the pressure to rise from the first pressure to the second pressure is stored in the storage device 24, and the pressure is reduced again. The cycle of operating the pump and stopping the vacuum pump when the pressure is reduced to the first pressure is repeated a predetermined number of times. The number of repetitions is usually about 3 times, and it takes about 120 minutes for 3 times. Then, the presence or absence of leakage is determined by the second determination means. That is, the time during which the decompression pump has been stopped from the storage device 24, that is, the transition of the time necessary for the pressure to rise from the first pressure to the second pressure, is read as pressure change data to the data processing device 23, This is compared with the pressure change pattern 32 stored in the storage device 24 to determine the presence or absence of leakage. An example of the transition of the time when the pressure rises from the first pressure to the second pressure is 9 minutes 33 seconds-22 minutes 33 seconds-28 minutes 53 seconds when there is a leak, When there is no leak, it is 37 minutes 6 seconds-59 minutes 26 seconds. When there is a leak, there is a feature that the time extension is smaller than when there is no leak. This is for the reason described below.
That is, before the decompression, the gas phase section 4 is a mixture of air and stored liquid vapor. When there is no leakage, the pressure rises only by the vaporization of the liquid, but the air in the gas phase part 4 decreases each time the pressure reduction is repeated, so that more liquid needs to be vaporized during the pressure-increasing process. It takes time. Although it becomes constant when the air in the gas phase portion is exhausted, the time required for pressure increase becomes longer during two to three pressure reduction and pressure increase cycles. Further, it is necessary to determine the first pressure and the second pressure so as to be like that. On the other hand, when there is a leak, the pressure increase due to the leak is always constant, so that the time required for the pressure increase is less than when there is no leak. Therefore, the pressure change pattern 32 that is a leakage determination criterion stored in the storage device 24 is configured to determine the presence or absence of leakage based on the rate of change of time required for pressure increase. As can be seen from this principle, the second determination means is effective for detecting leakage mainly when air enters from a leakage point, but is not suitable when water enters.

Next, it will be described how each leakage detection means is effective depending on the position of the leakage location.
FIG. 4 is a diagram showing the positional relationship between the liquid level 3 in the tank, the groundwater surface 33 outside the tank, and the leaking location of the tank. (A) When the liquid level 3 is lower than the groundwater level 33, (b) Is higher than the groundwater surface 33.
4A and 4B, when the leaked portion is located below the groundwater surface 33 and below the liquid level 3, water enters the liquid phase part 2, The intrusion sound is detected by a hydrophone or a microphone 11 at the tip of the probe 9, and a rise in the water level due to water intrusion is detected by the water level meter 10 to detect leakage.

When the leak location is above the ground water surface 33 and below the liquid level 3 as in the leak location 35 of FIG. 4B, air enters the liquid phase portion 2 and rises as bubbles. The sound of the bubbles is detected by the hydrophone or the microphone 11 at the tip of the probe 9, and the intrusion of air is also detected by a change in pressure, and leakage is detected.
As shown in FIG. 4 (a), when the leak location is below the groundwater surface 33 and above the liquid level 3, water enters the gas phase portion 4, so that the intrusion sound or the liquid level 3 enters. Is detected by a hydrophone or a microphone at the tip of the probe 9, and a rise in the water level due to water intrusion is detected by the water level meter 10 to detect leakage.
4A and 4B, when the leaked portion is located above the groundwater surface 33 and above the liquid surface 3, air enters the gas phase section 4. The intrusion sound of air is detected by the hydrophone or the microphone 11 at the tip of the probe 9, and the intrusion of air is also detected by a change in pressure, and leakage is detected.
As described above, according to the leak detection system of the present invention, since the leak can be detected by two kinds of methods regardless of the position of the leak point in the tank, the detection accuracy is extremely high.

  According to the leakage detection system for a liquid storage tank according to the present invention, since water is introduced into the tank as part of the inspection, the liquid stored in the tank to be inspected is not suitable to be mixed with water. Of course, it is also desirable that the viscosity be low so that water or air can easily enter. As long as these conditions are satisfied, the present invention can be applied to any liquid storage tank. Specifically, inspection of storage tanks such as gasoline, gasoline such as normal hexane, kerosene, light oil, heavy fuel oil A, heavy fuel oil B, heavy fuel oil C, tetralin, cyclohexane, etc., solvents such as toluene, xylene, etc. Is possible.

It is a block diagram of the leakage inspection system of the liquid storage tank which concerns on this invention. It is explanatory drawing which shows the structure of the front-end | tip part of a probe. It is a flowchart which test | inspects with the leak inspection system of the liquid storage tank which concerns on this invention. (A) It is a figure which shows the positional relationship of a liquid level, a groundwater surface, and a leak location when a liquid level is lower than a groundwater surface. (B) is a liquid level, a groundwater surface, and a leakage when a liquid level is higher than a groundwater surface. It is a figure which shows the positional relationship of a location.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tank 2 Liquid phase part 4 Gas phase part 7 Pressure reduction pump 9 Probe 10 Water level gauge 11 Hydrophone or microphone 13 Pressure gauge 16 Controller 17 Acoustic analysis part 18 Pump operation switch

Claims (6)

A vacuum pump for depressurizing the gas phase in a tank that stores a substantially water-insoluble liquid containing volatile components;
A probe in which a hydrophone or a microphone and a water level meter are disposed in the liquid phase portion below the tank, and a pressure gauge for measuring the pressure in the gas phase portion in the tank is disposed in the gas phase portion above the tank. ,
An acoustic analyzer for converting sound information collected by the hydrophone or microphone into leakage determination acoustic data, and analyzing the frequency to convert into leak location size evaluation data;
Control of the entire system, and recording, analysis and analysis of water level data sent from the water level gauge of the probe, pressure data sent from the pressure gauge, acoustic data for leakage judgment sent from the acoustic analysis device, and leakage location size evaluation data A control device for performing the determination;
A liquid storage tank leak detection system comprising:
(1) The suction port of the decompression pump is connected to the upper gas phase in the tank, and the tank is configured to be airtight,
(2) The control device
Decompression control means for operating the decompression pump until the inside of the tank is decompressed to a predetermined first pressure based on the pressure data, and stopping the decompression pump when the first pressure is reached;
While the decompression pump is in a stopped state, the acoustic data for leakage determination and recording by the acoustic analyzer, and the water level data of the water level meter are recorded, and the acoustic data for leakage determination and the recording of the water level data are recorded in a predetermined manner. A first determination means for determining the presence or absence of leakage in comparison with a leakage determination criterion;
An analysis means for analyzing the size of the leak location from the leak location size evaluation data when it is determined that there is a leak in the first determination;
When there is a leak in the gas resulting from the vaporization of the liquid in the tank when the decompression pump is stopped, air or water entering the tank is added due to the leak, and the pressure rises to a predetermined second pressure. , Recording the time required for pressure increase from the first pressure to the second pressure, operating the pressure reducing pump to reduce the pressure in the tank to a predetermined first pressure, and stopping the pressure reducing pump Then, when the operation of reducing the pressure to the first pressure is performed a required number of times when the pressure rises to the second pressure, a record of the time required for the pressure to rise is compared with a predetermined leak judgment criterion, Second determination means for determining the presence or absence of
A leakage detection system for a liquid storage tank, comprising:   The probe is provided with a sediment removing tool at a tip, and is configured to be able to perform an operation of removing the sediment on the bottom surface of the tank before being installed in the tank. The leak detection system of the liquid storage tank of 1.   The determination of the presence or absence of leakage by the leakage determination acoustic data made by the first determination means converts sound information collected by the hydrophone or microphone into leakage determination acoustic data in the acoustic analyzer, Is generated in the liquid by the intrusion sound of air or water entering the tank from the outside through the leaked part in the gas phase part or liquid phase part in the tank stored in the control unit in advance. It is determined whether or not it coincides with any of the sound data corresponding to the sound of bubbles or the dripping sound of water falling on the liquid surface, and if it coincides with any of them, it is determined that there is leakage. Item 2. The liquid storage tank leakage detection system according to Item 1.   The determination of the presence or absence of leakage by the water level data made by the first determination means is realized by determining whether the water level is rising due to water entering the tank from the outside, The liquid storage tank leakage detection system according to claim 1.   The determination of the presence or absence of leakage by recording the time required for the pressure in the gas phase portion to rise made by the second judgment means is an operation of reducing the pressure to the first pressure when the pressure rises to the second pressure. Is performed the required number of times, and the change in time required for the increase from the first pressure to the second pressure is compared with the change in time when there is a leak stored in the control unit in advance. 2. The liquid storage tank leak detection system according to claim 1, wherein it is determined that there is a leak if it is determined.   The leak location size evaluation data used for analyzing the size of the leak location made by the analysis means is a frequency distribution of sound information collected by the hydrophone or microphone, and is stored in the control unit in advance. 2. The leak detection system for a liquid storage tank according to claim 1, wherein the size of the leaking part is calculated by collating with correspondence data of the frequency distribution and the size of the leaking part.

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