JP3746057B2 - Liquid storage tank leak detection system and leak detection method - Google Patents

Description

  The present invention relates to a leakage detection system and a leakage detection method for detecting leakage of liquid from a liquid storage tank installed in a gas station, a factory, or the like. In the present application, “leakage” means both outflow of stored liquid from the liquid storage tank and inflow of rainwater, groundwater, etc. into the liquid storage tank, and “liquid amount” means “liquid level” or It shall also have the meaning of “liquid level”.

  Since liquid storage tanks buried underground are used for a long time, holes or cracks occur due to corrosion of the partition wall, or the liquid stored inside flows out to the outside for other reasons, or Rainwater, groundwater, etc. may flow from the outside.

  Conventionally, in order to detect such leakage, batch inspections such as a gas pressurization method, a liquid pressurization method, a fine pressurization method, and a fine depressurization method are regularly performed.

  According to the above batch inspection performed in the form of periodic inspection, it is possible to detect leaks with high accuracy. However, since periodic inspections are usually performed only once a year, there is no leakage during that period. If it occurs, it cannot be detected early.

  On the other hand, Patent Document 1 uses a sensor that detects increase / decrease in the amount of liquid in the liquid storage tank to record and accumulate changes in the amount of liquid in the liquid storage tank over the long term. A method for early detection of leakage based on data is disclosed.

However, in order to collect the liquid amount fluctuation data in the method of Patent Document 1, the liquid amount in the liquid storage tank needs to be in a stable state for a long time. When the tank is not used for a long time, for example, in the case of a gas station, it was necessary to perform it at night or on holidays other than business hours. Therefore, in the case of a gas station or the like that is open 24 hours, there is a problem that a sufficiently long liquid quantity stable period may not be obtained, and accurate leak detection cannot be performed.
JP 2001-97500 A

  The problem to be solved by the present invention is to provide a leakage detection means for a liquid storage tank that can grasp the tendency of a change in the amount of liquid even if a stable period of liquid amount is not obtained for a long time and can detect a leak at an early stage. There is.

The leak detection system of the present invention includes a liquid amount sensor that constantly measures the liquid amount in the liquid storage tank, a liquid amount data measured by the liquid amount sensor and a database that accumulates the measurement time, and a liquid amount data that is accumulated in the database. From the measurement time, continuous long-term liquid volume change data indicating the liquid volume change over time is generated, and it is determined from the continuous long-term liquid volume change data that there is substantially no change in the liquid volume over time. A liquid volume change data in a plurality of liquid volume stable periods is extracted, and a calculation unit that obtains a liquid volume change tendency from the liquid volume change data in the liquid volume stable periods and determines the presence or absence of leakage.

In the leakage detection method of the present invention, the liquid amount in the liquid storage tank is constantly measured by the liquid amount sensor, and the measured liquid amount data is stored in the database together with the measurement time. The liquid amount data stored in the database and the measurement time are stored in the database. From the continuous long-term liquid volume change data indicating the liquid volume change over time, a plurality of liquid volumes that are determined to be substantially free from temporal change in liquid volume from the continuous long-term liquid volume change data. Liquid quantity change data in the stable period is extracted, and the liquid quantity change tendency is obtained from the liquid quantity change data in each liquid quantity stable period to detect the presence or absence of leakage.

  In the present invention, liquid amount change reference data indicating the time change of the liquid amount during the liquid amount stabilization period of the liquid storage tank in a state where there is no leakage is obtained and stored in the database in advance, and each liquid at the time of collecting leakage detection data By comparing the liquid volume change data in the volume stabilization period with the liquid volume change reference data, the liquid volume change tendency can be obtained.

  Further, in the present invention, the liquid volume stabilization period is a time when it is determined from various information and data that there is substantially no change in the liquid volume over time. Analyzing the data, if the change in liquid volume over time is within the specified value, or judging from operation data such as unloading to the liquid storage tank and the presence or absence of liquid supply, the liquid enters and exits the liquid storage tank When there is no liquid, it is determined that the liquid level is stable. In addition, the liquid volume stabilization period of less than the predetermined time during which the liquid volume change cannot be detected is excluded, and only when there is no substantial change in the liquid volume over the predetermined time over which the liquid volume change can be detected, the liquid volume stabilization period You can also.

  According to the present invention, since the liquid volume change data in a plurality of liquid volume stable periods is comprehensively analyzed to determine the liquid volume change tendency and the presence or absence of leakage is determined, a long liquid volume stable period cannot be obtained. Also, the presence / absence of leakage can be determined with high accuracy.

  Therefore, for example, even when a liquid storage tank is used intermittently regardless of day or night, such as a 24-hour gas station, a minimum liquid quantity stable period in which a liquid quantity change can be detected is obtained. If it is possible, data for determining the presence or absence of leakage can be collected, and therefore the presence or absence of leakage can be determined at an early stage without impeding the operation of the liquid storage tank.

  As described above, since it is possible to determine the presence / absence of leakage with high accuracy based on continuous long-term liquid amount change data in the liquid storage tanks of all usage forms, it is possible to omit the conventional periodic inspection.

  Hereinafter, embodiments of the present invention will be described based on examples shown in the drawings.

  FIG. 1 is a system configuration diagram of a leak detection system of the present invention.

  As shown in the figure, the leak detection system of the present invention accumulates the liquid quantity sensor 2 that constantly measures the liquid quantity in the liquid storage tank 1, the liquid quantity data measured by the liquid quantity sensor 2, the measurement time, and the like. It comprises a database 3 and a calculation unit 4 that calculates the data stored in the database 3 and determines the presence or absence of leakage. The leak detection signal from the calculation unit 4 is transmitted to the alarm output / display means 5. In addition, a POS system 6 and a weighing machine 7 are connected to the database 3 via the communication line 8 as external devices, and various data from these external devices are also stored in the database 3.

  Various sensors can be used as the liquid level sensor 2, but it is preferable to use a sensor capable of measuring a liquid level or a change in liquid level with high resolution, such as a magnetostrictive sensor.

  The database 3 can be composed of a computer memory. The calculation unit 4 can be constituted by a CPU of a computer. As will be described in detail later, the calculation unit 4 is a liquid that indicates a change in the liquid amount over time from the liquid amount data accumulated in the database 3 and its measurement time. In addition to generating volume change data, a process of extracting liquid volume change data in a plurality of liquid volume stable periods in which it is determined that there is substantially no change in liquid volume over time is performed. And the liquid quantity change tendency is calculated | required from the liquid quantity change data in each liquid quantity stable period, and the presence or absence of leakage is determined.

  Hereinafter, the leak detection method by the leak detection system of this invention is demonstrated.

  FIG. 2 is a flowchart showing the entire process of the leak detection method of the present invention. In the leak detection method shown in the figure, first, reference data of the liquid storage tank 1 subject to leak detection is collected by the liquid amount sensor 2 shown in FIG. 1 (S1), and the reference data is analyzed to analyze the liquid storage tank. Liquid quantity change reference data in the liquid quantity stable period is obtained (S2). The obtained reference data and liquid volume change reference data are both stored in the database 3 shown in FIG.

  FIG. 3 is a flowchart showing the above-described reference data collection process. This reference data is collected in a state where it has been confirmed that there is no leakage by regular inspections.

  In the reference data collecting step, first, it is confirmed whether or not the measurement time interval of the liquid amount by the liquid amount sensor is a predetermined time (1 second in the embodiment) (S1-1). Next, measurement time data is acquired (S1-2), and the capture of the liquid amount data and liquid phase temperature data of the liquid storage tank is started (S1-3, S1-4). Thereafter, it is confirmed whether or not there is a change in events such as supply (unloading) and discharge (liquid supply) of the liquid to the liquid storage tank while the liquid volume data and the liquid phase temperature data are being captured (S1-5). If the event has changed, the event data is acquired (S1-6), and the liquid volume data and the liquid phase temperature data are stored in the database together with the measurement time data and the event data (S1-7). The collection of the reference data is continued until the cumulative time of the portion determined as the liquid volume stabilization period reaches a predetermined time (200 hours in the embodiment) (S1-8). The collection of the reference data is finished (S1-9). The determination as to whether or not the liquid amount is stable is made by a method described later.

  FIG. 4 is a flowchart showing the flow of the reference data analysis step for obtaining the liquid amount change reference data in the liquid amount stable period from the reference data collected in the reference data collection step of FIG.

  In the reference data analysis step, first, liquid amount change data indicating a time change of the liquid amount is generated from the collected reference data (S2-1). This is graphed as shown in FIG. Next, using the liquid volume change data, the time when it is determined that the liquid volume does not substantially change with time is extracted as the liquid volume stable period (S2-2). In the examples, the portion where the change in the liquid amount with time was within 0.2 L / h and the time length was 30 minutes or more was extracted as the liquid amount stable period. In addition to the extraction method using the liquid amount change data, judgment is made from operation data such as the presence / absence of liquid supply from the liquid storage tank separately collected by the POS system 6, the weighing machine 7, etc. (see FIG. 1). Thus, the time when it is determined that no liquid enters or leaves the liquid storage tank can be extracted as the liquid amount stable period.

  Next, liquid volume change data in each liquid volume stable period is extracted (S2-3), and liquid volume change reference data in the liquid volume stable period is calculated (S2-4). The liquid volume change reference data is simply the average of the liquid volume change data in each liquid volume stable period, and preferably, the average of the liquid volume change data is the temperature in order to correct the liquid volume change due to the temperature change. As a function of. Then, the liquid amount change reference data is accumulated in the database (S2-5), and the reference data analysis is finished (S2-6).

  Returning to FIG. 2, after performing the above-described reference data collection and analysis process in advance, the actual leak detection data is collected by the liquid amount sensor 2 shown in FIG. 1 (S3), and the data is analyzed. The presence or absence of leakage is determined (S4).

  FIG. 6 is a flowchart showing a leakage detection data collection process.

  The leak detection data collection process is the same as the basic data collection process shown in FIG. 3. First, whether or not the measurement time interval of the liquid volume by the liquid volume sensor is a predetermined time (1 second in the embodiment). (S3-1). Next, measurement time data is acquired (S3-2), and the acquisition of the liquid amount data and liquid phase temperature data of the liquid storage tank is started (S3-3, S3-4). Thereafter, it is confirmed whether or not there is a change in events such as liquid supply (unloading) and discharge (liquid supply) to the liquid storage tank while the liquid volume data and the liquid phase temperature data are being captured (S3-5). If the event has changed, the event data is acquired (S3-6), and the liquid volume data and the liquid phase temperature data are stored in the database together with the measurement time data and the event data (S3-7). In the middle of collecting the leakage detection data, if an abnormality is recognized in the liquid amount change amount such as a significant change in the liquid amount, an alarm such as a leakage alarm is output (S3-8, S3-9). Such collection of leakage detection data is continued until the accumulated time reaches a predetermined time (20 hours in the embodiment) (S3-10). When the predetermined time is reached, collection of leakage detection data is terminated ( S3-11).

  FIG. 7 is a flowchart showing the flow of the leakage detection data analysis step for obtaining the liquid amount change data in the liquid amount stable period from the data collected in the leakage detection data collection step of FIG.

  In the leakage detection data analysis step, liquid amount change data indicating the time change of the liquid amount as shown in FIG. 5 is generated from the collected leakage detection data (S4-1). Next, using the liquid volume change data, the time when it is determined that the liquid volume does not substantially change with time is extracted as the liquid volume stable period (S4-2). In the example, the portion where the change in the liquid amount with time was within 0.4 L / h and the time length was 20 minutes or more was extracted as the liquid amount stable period. In addition to the extraction method using the liquid amount change data, operations such as unloading to the liquid storage tank and the presence / absence of liquid supply separately collected by the POS system 6, the weighing machine 7, etc. (see FIG. 1) Judging from the data, it is possible to extract the time when it is determined that the liquid does not enter or leave the liquid storage tank as the liquid quantity stable period.

  Next, liquid volume change data in each liquid volume stable period is extracted (S4-3), and this is compared with liquid volume change reference data stored in advance in the database (S4-4). Specifically, the difference between each liquid amount change data and the liquid amount change reference data is calculated. Then, the comparison result is accumulated in the database (S4-5), and the leakage detection data analysis is terminated (S4-6).

  Returning to FIG. 2, using the comparison result (difference) between the liquid volume change data and the liquid volume change data in each liquid volume stability period obtained by the leakage detection data analysis, the liquid volume in the liquid volume stability period A change tendency is obtained, and leakage detection determination is made as to whether or not there is a possibility of occurrence of leakage (S5). In this leakage detection determination, there is a significant difference when the difference between the liquid amount change data in the liquid amount stable period and the liquid amount change reference data is a predetermined value or more (in the embodiment, 0.38 L / h or more), and there are a plurality of differences. If a significant difference is recognized at a predetermined ratio or more (80% or more in the embodiment) during the liquid volume stabilization period, it is determined that there is a possibility of leakage of the liquid storage tank, and there is a possibility of leakage of the liquid storage tank. The candidate is stored in the database as a candidate (S6).

  Thereafter, for the liquid storage tank with the possibility of leakage, the above-described leakage detection data collection (S3), leakage detection data analysis (S4) and leakage detection determination (S5) are repeated a predetermined number of times (10 times in the embodiment). Try (S7). Then, in the leakage detection determination, if the determination that there is a possibility of leakage is not less than a predetermined number of times (in the embodiment, 7 times or more in 10), it is determined that there is leakage (S8, S9). A detection signal is generated (S10). This leakage detection signal is transmitted to the alarm output and display means 5 shown in FIG. On the other hand, if the determination that there is a possibility of leakage is less than a predetermined number of times, it is determined that there is no leakage (S11), the data collected in steps S7 and S8 is initialized, and the process returns to step S3.

  In the above embodiment, the liquid volume change reference data in the liquid volume stable period in the absence of leakage is obtained in advance, and the liquid volume change reference data is compared with the liquid volume change data in the actual liquid volume stable period. The presence / absence is determined, but comparison with the liquid amount change reference data is not always necessary. In this case, in step S5 described above, when the liquid amount change data in the actual liquid amount stable period is a predetermined value or more (for example, ± 0.38 L / h or more), it is counted that there is a possibility of leakage.

  The present invention is applicable as a leakage detection system that detects leakage of liquid from any liquid storage tank installed in a gas station, factory, or the like.

It is a system configuration figure of a leak detection system of the present invention. It is a flowchart which shows the whole process of the leak detection method of this invention. It is a flowchart which shows the reference | standard data collection process in the leak detection method of this invention. It is a flowchart which shows the flow of the reference | standard data analysis process which analyzes the reference | standard data collected by the reference | standard data collection process of FIG. It is a schematic diagram which shows the time change of a liquid quantity. It is a flowchart which shows the data collection process for leak detection in the leak detection method of this invention. It is a flowchart which shows the flow of the data analysis process for leak detection which analyzes the data collected in the data collection process for leak detection of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Liquid storage tank 2 Liquid quantity sensor 3 Database 4 Calculation part 5 Alarm output and display means 6 POS system 7 Weighing machine 8 Communication line

Claims (4)

A liquid volume sensor that constantly measures the liquid volume in the liquid storage tank;
A database for storing liquid volume data measured by a liquid volume sensor and its measurement time;
From the accumulated liquid volume data and the measurement time in the database, to generate a long-term liquid quantity variation data consecutive showing temporal changes of the liquid volume, the time change of the liquid amount from the continuous long-term liquid quantity variation data Calculation of liquid volume change data in a plurality of liquid volume stable periods judged to be substantially non-existent, calculation of liquid volume change data from the liquid volume change data in the plurality of liquid volume stable periods to determine the presence or absence of leakage And
A leak detection system for a liquid storage tank. In the database, liquid amount change reference data indicating the time change of the liquid amount in the liquid amount stable period of the liquid storage tank in a state where there is no leakage is accumulated,
The liquid storage tank leakage detection system according to claim 1, wherein the calculation unit obtains a liquid amount change tendency by comparing the liquid amount change data in each liquid amount stable period with the liquid amount change reference data. . The liquid level in the liquid storage tank is constantly measured by the liquid level sensor,
The measured liquid volume data is stored in the database together with the measurement time,
From the stored liquid volume data and the measurement time in the database, to generate a long-term liquid quantity variation data consecutive showing temporal changes of the liquid volume, the time change of the liquid amount from the continuous long-term liquid quantity variation data Extract liquid volume change data in multiple liquid volume stable periods that are judged to be practically not,
A leakage detection method for a liquid storage tank that detects a liquid volume change tendency from liquid volume change data in each liquid volume stabilization period and detects the presence or absence of leakage. Accumulating liquid amount change reference data indicating the time change of the liquid amount in the liquid amount stabilization period of the liquid storage tank in a state where there is no leakage in the database in advance,
4. The liquid storage tank leak detection method according to claim 3, wherein a liquid volume change tendency is obtained by comparing liquid volume change data in each liquid volume stable period with the liquid volume change reference data.

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