JP4795775B2 - Underground tank leak inspection method - Google Patents

Description

  The present invention relates to a method for inspecting the presence or absence of leakage of liquid stored in an underground tank, and in particular, a minute opening formed on a wall of an underground tank or the like in which dangerous substances such as gasoline or various liquid chemicals are stored. The present invention relates to an underground tank leakage inspection method suitable for detecting leakage from a section.

  Conventionally, in reservoirs that store dangerous materials such as gasoline and other fuel oil in underground tanks, the underground tanks are airtight to prevent soil contamination and fire accidents due to leakage of fuel oil from the underground tanks. The government ordinance mandates that leakage inspections be performed regularly.

  Regarding airtight leak inspection of underground tanks buried underground and storing fuel oil, etc., when the government ordinance is revised (after April 1, 1994), when airtight leak inspection is performed with liquid stored In addition, it is obliged to conduct a leak inspection on both the gas phase portion, which is a space portion in the underground tank, and the liquid phase portion, which is a portion where a liquid such as fuel oil is stored.

  Therefore, before the revision, leak inspection manufacturers who had only conducted the leak inspection of the gas phase section in the underground tank have been making various efforts regarding the leak inspection method of the liquid phase section in response to this law revision.

  For example, in Japanese Patent Laid-Open No. 2005-292091, an underground tank leakage inspection method uses an inspection probe provided with a sensor for detecting displacement of a liquid flow velocity when liquid passes through an orifice passage, and leaks a liquid phase portion. A method for inspecting underground tank leaks is shown. In this leakage inspection method, this inspection probe is inserted into the underground tank so that the stored liquid in the underground tank is introduced into the orifice passage, and the inside of the underground tank is slightly pressurized or slightly depressurized. The liquid level displacement based on the pressure change in the underground tank caused by the leak location is detected by the above-described sensor, and the presence or absence of the leak location of the underground tank can be determined.

  And in the underground tank leakage inspection method, in order to ensure the accuracy of the inspection, the inside of the underground tank in which the inspection probe equipped with this kind of inspection sensor is inserted into the underground tank is slightly pressurized or slightly decompressed. In the previous static pressure state, it is necessary to determine whether or not the inspection sensor operates in a functional manner and the sensor itself is ready for inspection (hereinafter referred to as standby determination). ing. For example, in the case of using the sensor for detecting the liquid level displacement having the above-described configuration as the inspection sensor, the liquid in the underground tank is appropriately introduced into the orifice passage of the sensor, and the sensor functions as expected. It is necessary to carry out a standby determination as to whether or not it is in an inspectable state that operates and appropriately detects the level.

JP 2005-292091 A JP 2003-185522 A

FIG. 9A shows an inspection procedure of a conventional leakage inspection.
However, in the above-described underground tank leakage inspection method, first, static pressure inspection A for a predetermined time (for example, 40 minutes) is performed in a static pressure state before the inside of the underground tank is slightly pressurized or slightly decompressed for standby determination. After confirming that the sensor is in a state that can be inspected, for example, the inside of the underground tank is kept in a slightly pressurized state for a predetermined time (for example, 30 minutes), and the leakage inspection B of the gas phase is performed. After that, this time, it was a procedure to conduct a liquid phase leakage inspection C by holding the inside of the underground tank in a slightly reduced pressure state for a predetermined time (for example, 40 minutes) and detecting the presence or absence of liquid level displacement during this time with a sensor. .

  In other words, the airtight leak inspection of the underground tank before the revision was a leak inspection of only the gas phase part in the underground tank, whereas the airtight leak inspection of the underground tank after the revision was further performed for the liquid phase part in the underground tank. Since the leakage inspection has to be performed, the total inspection time is longer than before the revision.

  Therefore, the present invention is an airtight leak inspection of a current underground tank in which a leakage inspection of a gas phase portion and a liquid phase portion in the underground tank must be performed, and the underground tank of which the inspection total time is shortened. The purpose is to provide a leakage inspection method.

  In order to solve the above-described problems, the first aspect of the present invention is that the standby determination and the inspection of the gas phase part are performed at the same time so that the total time can be shortened.

The second is that the determination in the standby determination is performed precisely.
Therefore, the underground tank leakage inspection method of the present invention is based on the presence or absence of leakage spots in the gas phase portion and the liquid phase portion of the underground tank. A method for inspecting leaks in an underground tank that is inspected in a state, wherein a gas phase part that inspects for the presence or absence of a leak location in the gas phase part of the underground tank based on the output of a pressure sensor that detects the pressure in the gas phase part Based on the output of the leak inspection step, the liquid level displacement speed sensor that detects the change in the liquid level of the liquid phase part or the acoustic sensor that detects the sound in the underground tank. Whether or not the liquid surface displacement velocity sensor or the acoustic sensor used for detecting the presence or absence of a leaking portion generated in the liquid phase portion in the liquid phase portion leakage inspection step is in an inspectable state. To check Mumbai determination processing step has, the standby determination processing step, prior to the liquid phase portion leakage inspection step, and carrying out the gas phase leak test step the same time.

According to the present invention,
(1) Since the standby determination task and the slightly pressurized test task are performed at the same time, the time for standby determination can be shortened compared to the conventional case.
(2) Since fine pressurization is used for the gas phase inspection, the vaporization of oil such as gasoline, which is a dangerous substance stored in the underground tank, is suppressed, and the standby determination task status in the liquid phase inspection is It is more stable and can produce a synergy effect.
(3) The reliability of the standby determination task is increased by adopting the averaging comparison method within a certain period of time in the standby determination task (the embodiment is described every 5 minutes).

  DESCRIPTION OF EMBODIMENTS Hereinafter, an embodiment of an underground tank leakage inspection method according to the present invention will be described with reference to the drawings.

  FIG. 1 is a configuration diagram of a leakage inspection system used in the underground tank leakage inspection method of the present invention. FIG. 1 shows an example in which this leakage inspection system is applied to a gas station for supplying fuel to a vehicle or the like.

  The leakage inspection system 20 of the present embodiment includes an inspection probe 21 that is inserted into the underground tank 2 and detects an opening of a leakage portion that has occurred in the underground tank 2, and a liquid incorporated in the inspection probe 21. A measurement system configured by a measurement control device 24 that detects and processes signals supplied from the surface displacement speed sensor 22 and the microphone 23, performs display, recording, output, determination, and the like, and an inspection condition are set or executed. Therefore, it is roughly classified into an equipment system including a joint 71 for sealing the underground tank 2 and pressurizing or depressurizing the gas phase portion G, a ventilation hose 72, a supply / discharge pump 73, a pressure gauge 75, and the like.

  In FIG. 1, an oil liquid 3 is stored in an underground tank 2 of a gas station 1 to be inspected, and a liquid phase part L and a gas phase part G are formed therein. Reference numeral 4 denotes an injection pipe for replenishing the underground tank 2 with an oil solution. The inlet 4a is normally covered with a lid member 5 in an airtight manner except when oil is replenished. Reference numeral 6 denotes a suction pipe for sucking up the oil liquid in the underground tank 2, one end opening on the bottom side in the underground tank 2, and the other end connected to the measuring machine 7. The measuring machine 7 has a pump and a flow meter built in the main body thereof, and a check valve (not shown) for securing the suction head pressure of the pump is provided in the flow passage portion on the pump suction side communicated with the suction pipe 6. This check valve does not open during a leak test while keeping the inside of the underground tank 2 slightly pressurized or slightly depressurized, and automatically closes the other end of the suction pipe 6 to the outside. It is possible.

  Reference numeral 8 denotes a buried box (manhole protector) buried in the upper part of the underground tank 2, and the opening on the ground surface is covered with a manhole cover (not shown). In the buried box 8, a measuring port 9 a of the measuring tube 9 is opened for inserting a measuring rod, a float of a liquid level gauge, etc. into the underground tank 2. The measuring port 9a is airtightly covered except at the time of inspection by a lid member or a liquid level meter body attached to the measuring port 9a.

  Reference numeral 10 denotes a vent pipe having one end serving as a vent 10 a and the other end communicating with the upper side in the underground tank 2. The vent pipe 10 allows oil vapor in the underground tank 2 to escape to the outside.

  Next, the configuration of each part of the equipment system and the measurement system of the leakage inspection system 20 of the present embodiment will be described taking the above-described gas station 1 as an example.

In the equipment system, the supply / discharge pump 73 discharges the gas in the gas phase part G in the underground tank 2 to the outside and depressurizes the inside of the underground tank 2, or supplies nitrogen gas or the like to the gas phase part G in the underground tank 2. An inert gas is introduced to pressurize the inside of the underground tank 2. The supply / discharge pump 73 is airtightly connected to the vent hole 10 a of the vent pipe 10 and the joint 71 via the vent hose 72. In the middle of the ventilation hose 72, a thermometer 74 for measuring the temperature state in the underground tank 2 and a pressure gauge 75 for measuring the pressure state in the underground tank 2 are provided. Even the release of via a gas atmosphere opening hose 76 in the vapor phase G in the underground tank 2 is sucked by the supply and discharge pump 73, safe by, for example to emit mixed with an inert gas such as nitrogen gas・ Environmental measures have been taken.

  On the other hand, in the measurement system, the inspection probe 21 includes a liquid level displacement speed sensor 22 and a microphone (acoustic sensor) 23, and is inserted into the underground tank 2 from the measuring port 9a via the measuring tube 9 at the time of inspection. The The liquid level displacement speed sensor 22 measures the amount of liquid flow that passes through the flow rate sensor that is generated in accordance with the fluctuation of the liquid level. In the case of the present embodiment, a heat exchange type flow rate sensor is used as the liquid surface displacement speed sensor 22. The detection signal of the liquid surface displacement speed sensor 22 is connected to the safety holder 28 via a signal line 25a extending in the length direction of the inspection probe 21, and the output thereof is an I / F converter (interface converter). ) 29. Then, after signal processing is performed by the I / F converter 29, the signal is supplied to the measurement control device 24. The microphone 23 collects sound in the underground tank 2 and converts it into an electroacoustic signal. In the case of the present embodiment, the microphone 23 is a piezoelectric microphone having an oil-resistant anticorrosion structure. The electroacoustic signal including the non-audible wave signal output from the microphone 23 is connected to the sound converter 27 with safety holder via the signal line 25 b, and the output is supplied to the measurement control device 24. The sound converter 27 with safety holder converts the electroacoustic signal output from the microphone 23 into a sound signal and outputs the sound from the speaker. In addition, an atmosphere inside an extension portion 42 described later of the inspection probe 21 that changes in accordance with the pressure of the gas phase portion G in the underground tank 2 is introduced into the differential pressure transmitter 26 via the introduction tube 25c, The output is connected to the measurement control device 24.

  In the case of the present embodiment, the measurement control device 24 is constituted by a personal computer, and the output means 30 such as a display device or a printer for monitoring and outputting the inspection status and measurement results of the leakage inspection, and for the leakage inspection. A storage means 31 for accumulating various data and measurement results, and an input means 32 including a keyboard and the like for setting and inputting various data and starting the system and the like when performing the leakage inspection are provided. The measurement control device 24 detects a flow rate detection signal based on the liquid level displacement in the underground tank 2 detected by the liquid level displacement speed sensor 22 in the underground tank 2 supplied via the I / F converter 29, and a safety holder. The underground tank 2 is based on an electroacoustic signal (for example, 1 to 5 kHz) including a non-audible wave signal detected by the microphone 23 in the underground tank 2 converted into a frequency signal supplied via the attached sound converter 27. Inspect the presence or absence of openings (leakage points) in the interior.

  In addition, the measurement control device 24 determines the pressure level of the gas phase portion G in the underground tank 2 held at the time of the inspection, the tank capacity (tank dimensions), and the liquid level of the dangerous substance when performing the leakage inspection. (Height from the bottom of the tank to the liquid surface) and the density of dangerous materials are set. Furthermore, the groundwater level around the underground tank 2 (height from the tank bottom to the groundwater surface) is taken into account. Thus, it functions as a reduced pressure calculating means for setting the inspection pressure.

  In the leakage inspection system 20 of the present embodiment configured as described above, the underground tank 2 sealed by the air supply operation or the exhaust operation of the supply / exhaust pump 73 is brought into a slightly pressurized state or a slightly reduced pressure state, and the underground tank Detecting intrusion of groundwater or air caused by a leaked portion of the gas phase portion G or liquid phase portion L in the liquid tank 2 by the liquid level displacement speed sensor 22 or the microphone 23 of the inspection probe 21 inserted in the underground tank 2. Thus, it is possible to carry out an underground tank leakage inspection method for inspecting the presence or absence of leakage points in the underground tank 2.

  Next, the configuration of the inspection probe 21 as a leakage sensor device used in the underground tank leakage inspection method of the present invention will be described with reference to the drawings.

  FIG. 2 is a configuration diagram of an embodiment of an inspection probe as a leakage sensor device used in the underground tank leakage inspection method of the present invention.

  In the case of the present embodiment, the inspection probe 21 has a configuration in which a cylindrical sensor storage housing portion 43 is integrally connected to the head portion 41 via an elongated cylindrical tube-shaped extension portion 42. . The sensor housing case 43 and the extension part 42 are integrally inserted into the underground tank 2 from the measuring port 9a via the measuring pipe 9, and the extension part 42 places the sensor housing case 43 in the height of the underground tank 2. It has a length that can be arranged and held on the bottom side in the direction.

  The sensor housing case 43 is immersed in the oil liquid in the underground tank 2 in the inserted state in the underground tank 2, and the sensor housing case 43 through the opening 44 formed in the tip opening and the tip side peripheral surface. The oil can flow into and out of the inside. In addition, the inside of the sensor housing housing portion 43 is communicated with the inside of the cylindrical extension portion 42 through the orifice passage 45 for flow rate measurement of the heat exchange type flow meter 40 as the liquid level displacement speed sensor 22. Between the inside of the sensor housing case 43 and the inside of the extension part 42, the oil liquid can be circulated through the measurement orifice passage 45 of the heat exchange type flow meter 40.

  The cylindrical extension portion 42 is configured to store therein an oil liquid having a liquid level corresponding to the liquid level (liquid level) of the oil liquid in the underground tank 2.

  The inside of the cylindrical extension portion 42 communicates with the inside of the head portion 41, and a microphone unit 46 including a microphone (acoustic sensor) 23 is accommodated in the head portion 41. The microphone unit 46 is used for sound (acoustic vibration) generated in the underground tank 2 that is propagated to the extension part 42 through the gas phase part G, the liquid phase part L, the tank wall or the like collected by the microphone 23 at the time of leakage inspection. ) Is supplied to the sound converter 27 with safety holder.

  The inspection probe 21 of the present embodiment configured as described above is configured so that the flange portion 47 formed at the boundary between the extension portion 42 and the head portion 41 is connected to the end surface of the measuring port 9a of the measuring tube 9 when performing a leakage inspection. And is fixed and held in an airtight manner in the measuring port 9a. In FIG. 2, reference numeral 48 denotes an output derivation unit formed in the head unit 41. The detection output by the heat exchange type flow meter 40 and the detection output by the microphone unit 46 are the safety retainer 28 and the safety holding unit shown in FIG. 1. The signal lines 25a and 25b that are transmitted to the sound converter 27 with a device are led out in an airtight manner, and the introduction tube 25c to the differential pressure transmitter 26 is connected in an airtight manner.

  In the leak inspection system 20 configured as described above, the leak location of the underground tank 2 is detected by operating the supply / exhaust pump 73 to supply or exhaust air to slightly increase the pressure of the gas phase G in the underground tank 2 or After maintaining the slightly reduced pressure state, the heat exchange type flow meter 40 monitors the abnormal liquid level height displacement in the underground tank 2, monitors the abnormal sound collected by the microphone unit 46, and further from the differential pressure transmitter 26. This is performed by monitoring the atmosphere inside the extension part 42 of the inspection probe 21 that changes in accordance with the pressure of the gas phase part G in the underground tank 2 to be supplied.

  In the leakage inspection system 20 having the above-described configuration, for example, abnormal liquid surface height displacement in the underground tank 2 due to the ingress of underground water into the underground tank 2 due to the groundwater level around the outer periphery of the underground tank 2, etc. Heat exchange is used for the outflow / inflow of the oil liquid stored in the extension section 42 through the sensor housing case 43 that is generated in conjunction with the slight fluctuation in the level of the liquid level in the underground tank 2. It is detected by monitoring with the flow meter 40 (liquid level displacement speed sensor 22).

  This method measures the amount of liquid flow that passes through the heat exchange type flow meter 40 generated in accordance with the fluctuation of the liquid level, and measures the displacement speed of the liquid level, that is, the liquid level per unit time. In order to detect the amount of displacement, if the diameter of the orifice passage 45 for measurement described above is reduced, the resolution of the heat exchange type flow meter 40 is improved, and a minute liquid level displacement can be detected. .

  In the leak inspection system 20 configured as described above, the heat exchange type flow meter 40 as the liquid surface displacement speed sensor 22 has the above-described configuration, so that the inspection probe 21 is inserted into the underground tank 2 and the inspection is performed. When performing the operation, it is necessary to introduce the oil liquid in the underground tank 2 into the extension part 42 through the above-described measuring orifice passage 45 and to make the liquid level height inside and outside the extension part 42 the same. There is. Therefore, after the inspection probe 21 is inserted into the underground tank 2, the liquid level in the extension portion 42 is the same as the liquid level in the underground tank 2, and whether or not inspection is possible. Standby judgment is required.

  Then, next, an embodiment of the leakage inspection method for an underground tank of the present invention including the standby determination will be described with reference to the drawings, taking the leakage inspection system 20 described above as an example.

FIG. 3 is a flowchart of one embodiment of the underground tank leakage inspection method of the present invention.
In the present embodiment, the leak inspection of the underground tank 2 will be described on the assumption that the leak inspection of the gas phase portion G is inspected by slight pressurization, and the leak inspection of the liquid phase portion L is inspected by fine decompression.

  In conducting the leak inspection of the underground tank 2, the worker first performs test preparation work (step S100). In this test preparation work, as shown in FIG. 1, the worker performs a connection preparation work for the measurement system and the equipment system. In addition, the inspection pressure varies depending on the size (internal capacity) of the underground tank and the situation of groundwater in the vicinity of the underground tank, so after investigating the necessary items, inspection information on the underground tank 2 to be inspected (for example, tank capacity) (Tank dimensions), dangerous liquid level (height from tank bottom to liquid level), density of dangerous goods, groundwater level around underground tank 2 (height from tank bottom to ground water level)) The setting input from the means 32 is used to calculate data such as the magnitude of the pressure in the gas phase portion G in the underground tank 2 which is kept in a slightly pressurized or slightly depressurized state at the time of inspection and the monitoring time in the inspection. Then, the obtained data is stored in the storage means 31 as menu data for performing the inspection. This menu data is displayed or printed out from the output means 30, and the operator can confirm the contents of the inspection.

  When the test preparation work is completed, the operator performs a predetermined operation on the input means 32 to instruct the measurement control device 24 to start the inspection work (step S200).

  In the present embodiment, first, the measurement control device 24 drives and controls the supply / discharge pump 73 and the like to pressurize the pressure of the gas phase portion G in the underground tank 2 and finely set as menu data. A fine pressurizing process is performed so as to obtain a pressure value (step S300). In this case, since the measurement control device 24 stipulates that the pressure is kept at 2 kPa by law in the micro-pressure leakage inspection of the underground tank 2, the measurement control device 24 includes the differential pressure transmitter 26. If the pressure in the gas phase section G in the underground tank 2 becomes 2 kPa based on the read output or measured data of the pressure gauge 75 (step S400), the supply / discharge pump 73 and the like are stopped and controlled. The fine pressurizing process is stopped (step S500).

  And the measurement control apparatus 24 starts simultaneously the standby determination process (step S600) and the micro pressurization leak inspection process (step S700) of the gaseous-phase part G in the underground tank 2, for example simultaneously. In the present embodiment, the standby determination process (step S600) and the slightly pressurized leak inspection process (step S700) of the gas phase portion G are started at the same time, but at the same time, in other words, at least If a part of the processing is performed in parallel, the start time may not be simultaneous.

  In this case, in the standby determination process (step S600), the liquid level in the extension part 42 of the inspection probe 21 inserted into the underground tank 2 after the slight pressurization of the underground tank 2 is the liquid level in the underground tank 2. In the process of determining whether or not it is in an inspectable state in which the heat exchange flow meter 40 of the inspection probe 21 can detect even a minute liquid level displacement, with the height being the same as or corresponding to the surface height. is there. In the present embodiment, in this standby determination process, it is also confirmed whether noise in a band that interferes with the leakage inspection from the microphone (acoustic sensor) 23 has occurred.

  Further, the slightly pressurized leak inspection process (step S700) is performed on the underground tank 2 sealed in a slightly pressurized state during the inspection time set as menu data according to the capacity of the underground tank 2 to be inspected. Whether or not there is a pressure change exceeding a predetermined value determined in advance is determined by the measurement control device 24 as to whether or not there is a leaking point in the gas phase G such as the output of the differential pressure transmitter 26 or the pressure gauge 75. This is a process of reading the measurement value of the sensor used and monitoring and determining the read measurement data.

Here, in the standby determination process shown in step S600, the heat exchange type flow meter 40 as the liquid surface displacement speed sensor 22 of the inspection probe 21 can be inspected so that a minute liquid surface displacement can be detected. A specific example of whether or not there is a determination process will be described with reference to FIG .
FIG. 4 is a flowchart of an example of standby determination processing of the liquid surface displacement speed sensor 22 by the underground tank leakage inspection method of the present embodiment.

4, the measurement control unit 24, the count time t _c timer with the timing with stop of slight pressure processing described in step S600 is determined previously set as the menu data latency T _{wait (e.g.} 30 Minute) has elapsed (step S601), and if the determination waiting time _Twait has elapsed, the liquid level displacement speed standby using the heat exchange type flow meter 40 as the liquid level displacement speed sensor 22 is determined. Judgment measurement is started.

In this case, the measurement control device 24 first resets the timer (t _c = 0) when the determination waiting time T _wait elapses as standby determination measurement of the liquid surface displacement speed using the heat exchange type flow meter 40, and measures the time. Is started (step S602). Then, the measurement control device 24 starts the time measurement of the timer and each time the timer measures a predetermined sampling time t _int (for example, 5 seconds), the heat exchange type flow meter as the liquid level displacement speed sensor 22 is used. The liquid level displacement speed f _int based on the measured flow rate by 40 is read, and the sequential storage process for storing and holding the read liquid level displacement speed f _int in correspondence with the timer time t _c is started (step S603). .

The measurement control device 24 calculates the reference determination time Tb _judg together with the start of the standby determination measurement of the liquid surface displacement speed using the heat exchange type flow meter 40 (step S604), and the reference determination time Tb _judg. The determination time T _judg is calculated based on (step S605).

Here, the reference determination time Tb _judg is a predetermined liquid surface average displacement speed calculation time T _av (for example, 5 minutes, where T _av is Tb _judg > T _av > t _int ) and the liquid surface average displacement. Based on the speed calculation shift time δ (for example, 5 minutes, where δ ≧ t _int ), calculation is performed as shown in the following equation.
Reference determination time Tb _judg = liquid surface average displacement speed calculation time T _a (5 minutes) + liquid surface average displacement speed calculation Displacement time δ (5 minutes) Equation (1)

FIG. 5 is a diagram illustrating the relationship between the sampling time t _int , the liquid surface average displacement speed calculation time T _av , the liquid surface average displacement speed calculation shift time δ, the reference determination time Tb _judg , and the determination time T _judg . is there.

After the start of the sequential storage process, the measurement control device 24 determines whether or not the timer time t _c has passed the determination time T _judg (the first determination time T _judg is 10 minutes of the reference determination time Tb _judg ). Determination is made (step S606).

When the measurement control device 24 determines that the determination time T _judg has elapsed, the liquid level displacement that has been acquired and stored in _{association with} the time _count t _{c of the} timer each time the sampling time t _int has elapsed. Among the speeds f _int , the liquid level displacement speeds f _int corresponding to the respective time _counts t _{c that} are traced back by the reference judgment time Tb _judg from the judgment time T _judg are read out.

In this case, the measurement control device 24 includes the determination time T _judg (initially 10 minutes) and is arranged in time series from the determination time T _judg by the reference determination time Tb _judg (10 minutes). That is, “Tb _judg / t _int ” (1200 in this case) liquid surface displacement speeds after the time (T _judg −Tb _judg ) and until the determination time (determination time) T _judg Based on the liquid level average displacement speed calculation time T _av (5 minutes) and the liquid level average displacement speed calculation shift time δ (5 minutes), the read sample of f _int is time (T _judg −Tb _judg ) later than at the time _{(T Judg} - [delta) until the _"t av _/ t _int" number (in this case, due to the time series aligned liquid level displacement speed _{f int} in 5 min 600) A first group G1, the time _(T judg _-Tb judg + _δ) of up to the time _{T Judg} later than _"t av _/ t _int" number (in this case, 600 for 5 min) chronologically aligned in Dividing into the second group G2 based on the liquid surface displacement speed f _int , the liquid surface average displacement speeds VG1 _av and VG2 _av for each group G1 and G2 are calculated (steps S607 and S608).

Based on the calculation result, the measurement control device 24 determines whether or not the deviation of the liquid surface average displacement velocities VG1 _av and VG2 _av is within a predetermined range, thereby determining the liquid surface displacement of the inspection probe 21. It is determined whether or not the heat exchange type flow meter 40 as the speed sensor 22 is ready for inspection (standby completion state) (step S609).

  In addition, if the measurement control device 24 determines that it is in the standby state in the determination of step S609, the slight pressurization leakage with respect to the gas phase portion G of the underground tank 2 as shown in FIG. After confirming the determination result of the absence of a leaked part by inspection (step S1000), in order to shift own processing to the implementation of the micro vacuum leakage inspection process for the liquid phase part L (steps S1200 to S1700), this standby completion state is set. Once stored and held (step S610).

On the other hand, in the determination in step S609 described above, the measurement control device 24 is not yet in a state (standby state) in which the heat exchange type flow meter 40 as the liquid level displacement speed sensor 22 of the inspection probe 21 can be inspected. In the case of the determination, the measurement control device 24 is predetermined with respect to the previously calculated determination time T _judg (in the case of the first determination time T _judg , 10 minutes of the reference determination time Tb _judg ). and are determined intervals [delta] _Judg (e.g., 1 minute) was added,
Determination time T _judg = determination time T _judg + determination interval δ _judg formula (2)
(Step S611), and the process after step S606 is repeated based on the updated standby determination time _Tjudg .

Incidentally, as shown in FIG. 5, the liquid surface slip rate _VG1 av, _{VG2 av} as an example of the liquid surface slip rate _{VG1 av ~VGm} av for each group G1~Gm described in step S607, S608 described above, time series aligned _"t av _/ t _int" pieces thereof (in this case, 5 minutes 600) extraction method to the group G of the liquid surface displacement rate _{f int} liquid level displacement speed _{f int} formed by of, By changing the liquid surface average displacement speed calculation time T _av , the liquid surface average displacement speed calculation shift time δ, the reference determination time Tb _judg based on these, and the determination interval δ _judg within a predetermined range, various _values can be obtained. Variations of this are possible.

6, 7, and 8 show the liquid level average displacement speed VG1 for each group G1, G2 when the group number m is 2 regarding the liquid level average displacement speeds VG1 _{av to} VGm _{av for the} groups G1 to Gm. it is a view showing a modified example of the _{av, VG2 av.}

FIG. 6 shows that in each group G1, G2, the liquid surface average displacement speed calculation shift time δ is longer than the liquid surface average displacement speed calculation time T _av (for example, 5 minutes) (for example, 6 minutes, δ> T _av ). Between the data of the liquid level displacement speed f _int of “t _av / t _int ” (in this case, 600 in 5 minutes) arranged in time series of each of the groups G1 and G2. A modification example in which an interval of minutes, δ−T _av ) is provided is shown.

FIG. 7 shows that in each group G1, G2, the liquid surface average displacement speed calculation shift time δ is set to a predetermined time (for example, 1 minute) shorter than the liquid surface average displacement speed calculation time T _av (for example, 5 minutes). A part of data of the liquid level displacement velocity f _int (for example, for 4 minutes) of “t _av / t _int ” (in this case, 600 in 5 minutes) arranged in time series between G1 and G2. ) And the same interval as the liquid level average displacement speed calculation shift time δ based on step S611 in FIG. 4 as the determination interval δ _judg between the previous determination and the current determination ( For example, a modification example in which the same 1 minute) is set in advance is shown.

  On the other hand, in FIG. 8, in the modified example of FIG. 6 and FIG. 7 described above, the group G for examining the deviation is set to 2 in steps S607 to S609 in FIG. The modification which made it 3 groups is shown.

  Returning to FIG. 3 again, after performing the standby determination process (step S600) as described with reference to FIGS. Step S700) is performed.

In this case, when the standby determination process (step S600) has already been performed, the pressure in the gas phase portion G in the underground tank 2 is maintained at 2 kPa, which is defined as the inspection pressure by law, so the measurement control device 24 It is not necessary to perform the pressurizing process, and whether or not there is a pressure change in the gas phase portion G only during the monitoring time corresponding to the tank to be inspected previously set as the menu data in step S100. The liquid surface displacement speed f _int based on the measured flow rate of the heat exchange type flow meter 40 as the surface displacement speed sensor 22 is acquired and monitored (steps S700 and S800). And the measurement control apparatus 24 performs the leak determination about the gaseous-phase part G of the underground tank 2 based on the monitoring result (step S900). The detailed description of the fine pressure leak inspection process (steps S700 and S800) and the leak determination process (step S900) in this case is the same as in the prior art, and is therefore omitted.

On the other hand, in the present embodiment, unlike the case of the prior art, the measurement control device 24 supplies a standby signal to each part of the system and performs a slightly pressurized leak inspection process during the standby determination process in step S600 described above. All or part of the liquid surface displacement speed f _int used for the determination of the standby determination (step S609 shown in FIG. 4) that is the basis for the transition to the mode is performed by the fine pressurization leakage inspection process of step S700. By using it as all or part of the liquid level displacement speed f _int to be acquired, the monitoring time can be shortened within the range of the reference determination time Tb _judg of the standby determination processing.

  FIG. 9 is a process comparison diagram between the underground tank 2 leakage inspection method according to the prior art and the underground tank 2 leakage inspection method according to the present embodiment.

As shown in FIG. 9, according to the underground tank leakage inspection method according to the present embodiment, the standby determination process is performed after the underground tank is slightly pressurized, so that the range of the reference determination time Tb _judg of the standby determination process It is possible to shorten the inspection time of the slight pressure leak inspection.

For example, assuming that the underground tank 2 having a size of 10k requires 40 minutes for the standby determination by the static pressure inspection and 30 minutes for the slight pressure leak inspection, The inspection time required for the pressure leak inspection can be shortened from the total inspection time of 70 minutes. Similarly, assuming that the underground tank 2 having a size of 30 k requires 40 minutes for the standby determination by the static pressure inspection and 60 minutes for the slight decompression leakage inspection, the inspection time required for the standby determination 40 minutes can be reduced from the total inspection time of 100 minutes. In addition, assuming that the underground tank 2 having a size of 20k requires 40 minutes for the standby determination by the static pressure inspection and 45 minutes for the slight decompression leakage inspection, the inspection time required for the standby determination 40 minutes can be shortened from the total inspection time of 85 minutes.

  Returning to FIG. 3 again, the measurement control device 24 completes the standby determination (step S1000) when it is determined that there is no leakage (step S1000) as a result of the leakage determination for the gas phase portion G of the underground tank 2 (step S900). On the condition of S1100), the fine pressure leak inspection for the gas phase part G of the underground tank 2 is completed, and the process proceeds to the fine vacuum leak inspection (step S1200) for the liquid phase part G of the underground tank 2, Do. The detailed description of each process (steps S1200 to S1700) of the fine pressurization leakage inspection process in this case is the same as in the prior art, and is therefore omitted.

  As described above, the underground tank 2 leakage inspection method of the present embodiment is configured, but various modifications can be made to the embodiment. For example, in the embodiment described above, the standby determination process is performed after the underground tank 2 is slightly pressurized, but the standby determination process is performed after the underground tank 2 is slightly depressurized. Is also possible. In this case, a slight decompression leakage inspection is performed after the standby determination.

It is a block diagram of the Example of the leakage inspection system used for the leakage inspection method of the underground tank of this invention. It is a block diagram of one Example of the test | inspection probe as a leak sensor apparatus used for the leak test method of the underground tank of this invention. It is a flowchart of one Embodiment of the leakage inspection method of the underground tank of this invention. It is a flowchart of the Example of the standby determination process by the leak inspection method of the underground tank of one embodiment of this invention. FIG. 6 is a diagram for explaining the relationship _{among a} sampling time t _int , a liquid surface average displacement speed calculation time T _av , a liquid surface average displacement speed calculation shift time δ, a reference determination time Tb _judg , and a determination time T _judg in standby determination processing. Regarding the liquid level average displacement speeds VG1 _{av to} VGm _{av for} each of the groups G1 to Gm, a modification example of the liquid level average displacement speeds VG1 _av and VG2 _av for each of the groups G1 and G2 when the number of groups m is 2. FIG. Regarding the liquid surface average displacement speeds VG1 _{av to} VGm _{av for} each of the groups G1 to Gm, another modification of the liquid surface average displacement speeds VG1 _av and VG2 _av for each of the groups G1 and G2 when the number of groups m is 2. It is the figure which showed the example. With respect to the liquid level average displacement speeds VG1 _{av to} VGm _{av for} each of the groups G1 to Gm, if the number of groups m is assumed to be 2, the liquid level average displacement speeds VG1 _av and VG2 _av for each group G1 and G2 are further different. It is the figure which showed the modification. It is a process comparison figure with the underground tank leakage inspection method by a prior art, and the underground tank leakage inspection method by this Embodiment.

Explanation of symbols

1 Gas station 2 Underground tank 3 Oil liquid 4 Injection pipe 5 Lid member
6 Suction Pipe 7 Measuring Machine 8 Buried Box 9 Measuring Pipe 10 Ventilation Pipe 20 Leakage Inspection System 21 Inspection Probe 22 Liquid Surface Displacement Speed Sensor 23 Microphone 24 Measurement Control Device 26 Differential Pressure Transmitter 27 Voice Converter with Safety Holder 28 Safety holder 29 I / F converter 30 Output means 31 Storage means 32 Input means 40 Heat exchange type flow meter 41 Head part 42 Extension part 43 Sensor housing case 44 Opening 45 Orifice passage 46 Microphone unit 47 Flange part 48 Output deriving part 71 Joint 72 Ventilation hose 73 Supply / discharge pump 74 Thermometer 75 Pressure gauge 76 Air release hose

Claims (8)

An underground tank leakage inspection method for inspecting the presence or absence of leaks occurring in a gas phase part and a liquid phase part of an underground tank with the pressure state of the gas phase part of the underground tank being slightly pressurized or slightly depressurized. ,
A gas-phase part leakage inspection step for inspecting the presence or absence of a leaked portion generated in the gas-phase part of the underground tank based on the output of a pressure sensor for detecting the pressure of the gas-phase part;
Liquid that inspects the presence or absence of leaks in the liquid phase part of the underground tank based on the output of a liquid level displacement speed sensor that detects a change in liquid level in the liquid phase part or an acoustic sensor that detects sound in the underground tank Phase leak inspection step,
A standby determination processing step for confirming whether or not the liquid surface displacement speed sensor or the acoustic sensor used for detecting the presence or absence of a leakage portion generated in the liquid phase part in the liquid phase part leakage inspection step is in an inspectable state;
Have
An underground tank leakage inspection method, wherein the standby determination processing step is performed prior to the liquid phase portion leakage inspection step at the same time as the gas phase portion leakage inspection step. The step of inspecting the gas phase portion leakage is a step of inspecting the presence or absence of a leak location in the gas phase portion while maintaining the pressure state of the gas phase portion of the underground tank in a slightly pressurized state based on the output of the pressure sensor. And
2. The underground according to claim 1, wherein the standby determination processing step is performed at the same time in a state where the pressure state of the gas phase portion of the underground tank is slightly pressurized by the gas phase portion leakage inspection step. Tank leak inspection method. The sensor used in the liquid phase leakage inspection step is a liquid level displacement speed sensor,
The standby determination step calculates a liquid surface average displacement speed VGk _av detected by the liquid surface displacement speed sensor in units of a predetermined liquid surface average displacement speed calculation time T _av , and calculates the calculated liquid surface average displacement speed. VGk _av ,... When the mutual deviation is within a predetermined range, it is determined that the sensor is in a standby state in which a change in the liquid level of the liquid phase portion in the underground tank can be detected. The leakage inspection method for underground tanks according to 1 or 2 . The liquid surface average displacement speed is characterized in that the liquid surface average displacement speed calculation time T _av is shifted by time δ in the time direction between the liquid surface average displacement speeds VGk _av and VGk + 1 _av adjacent in time series. The underground tank leakage inspection method according to claim 3 . Time δ is a value smaller than the liquid surface slip rate calculating time T _av, time series on the liquid surface average slip rate VGk adjacent av, time between _{VGk +} 1 _av, each of the liquid surface slip rate calculating time T _av 5. The underground tank leakage inspection method according to claim 4 , wherein a part of the tanks overlaps each other in the series direction. Time δ is a value smaller than the liquid surface slip rate calculating time T _av, time series on the liquid surface average slip rate VGk adjacent av, time between _{VGk +} 1 _av, each of the liquid surface slip rate calculating time T _av 5. The underground tank leakage inspection method according to claim 4, wherein time intervals are provided in the series direction. The standby determination step, according to claim 3 the calculated liquid surface slip rate VGk av, _... mutual deviations if not within a predetermined range, which is characterized in that repeatedly at a determination interval [delta] _Judg predetermined Inspected underground tank leak inspection method. The decision interval [delta] _Judg the leak testing method of underground tanks according to claim 7, characterized in that the value smaller than the liquid surface slip rate calculating time T _av.

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