JP2020060472A - Measurement method and device of total stock of liquid tank, and monitoring system - Google Patents

Abstract

To rapidly and accurately perform detection of the total stock of tanks, and leakage of tanks and piping connected to the tanks, monitoring of a working state of tanks in a steady state and in emergency, and the like by permitting estimation of an error of an oil level meter installed in tanks for storing liquid.SOLUTION: The present invention is based on new findings that an error of an oil level meter installed in an oil tank buried underground finely varies at a short time interval p and varies periodically between an upper limit and a lower limit as a whole. In the present invention, a calibration function of approximately obtaining a true total stock from a total stock detected by the oil level meter is obtained for each tank and a true total stock is estimated based on measurement data of an oil level meter 4 and a liquid level meter 5 for measuring a delivery amount from the tank in the past.SELECTED DRAWING: Figure 2

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for measuring an inventory amount based on a detection value of a liquid level gauge provided in a tank that stores a liquid, and a monitoring system.

  Petroleum distributed as gasoline, kerosene, etc. is supplied from former vendors to general gas stations commonly known as gas stations and private gas stations that are large-scale consumers. At gas stations, gasoline and kerosene are stored in underground tanks. Each tank is equipped with a liquid level gauge that measures the inventory amount (storage amount) in the tank, and the inventory amount calculated based on the detected value of the liquid level indicator is known by a monitor installed on the ground or in the tank control room. be able to.

  For tanks and pipes buried underground as dangerous goods facilities, it will be difficult to confirm leakage from the point when installation is completed. The presence or absence of leakage from the tank is judged by a legally prescribed inspection once every three years or once a year.

  Leaks in underground tanks are judged by legally defined inspections once every 3 years or once a year. This is because the presence or absence of leakage at the time of the inspection is judged, and the next inspection Does not guarantee that there is no leakage. Therefore, the presence or absence of leakage during that period is confirmed by the owner of the hazardous material facility by recording daily liquid level data and sales data from the fuel tank liquid level meter.

  The liquid level meter provided in the fueling machine measures each fueling machine in advance, and the error is within ± 0.5%. Therefore, it can be estimated that the measured value of the liquid meter is almost accurate. For the stock quantity of the tank, the relationship between the position of the liquid level and the stock quantity is theoretically obtained according to the shape of the tank, and the stock quantity is calculated from the detected value of the liquid level gauge by the calculated formula.

  However, in the underground tank, there is a variation between the stock quantity calculated from the detection value of the liquid level gauge and the true stock quantity for each tank. Underground tanks may be deformed or tilted due to ground subsidence after refilling, the condition of groundwater, how earth pressure is applied, etc. As a result, the relationship between the level gauge detection value and the true inventory level Deviation or error occurs.

  Liquid is supplied to the tank from a tank truck. Normally, the storage of petroleum from the tank truck is carried out in units of 2 kL (kiloliter), but it is not constant because there is evaporation during transportation, and it is difficult to measure the amount of evaporation. Therefore, it is not possible to correct the relational expression between the detected value of the liquid level gauge and the stock amount based on the amount of oil supplied from the tank truck.

  As mentioned above, the owner of the hazardous material facility confirms whether or not the tank has leaked by recording daily liquid level gauge data and liquid level gauge data. For example, at general gas stations, the amount of liquid in the underground tank is measured daily with a liquid level gauge. The stock quantity on the day is the sum of the stock quantity on the previous day and the stock quantity (the quantity received from the tank truck) and the stock quantity (sales quantity), which is subtracted from the stock quantity (hereinafter referred to as the “calculated stock quantity”). In addition, due to the measurement accuracy of the liquid level gauge and the deformation of the underground tank, an error inherent in the calculated inventory quantity occurs for each tank.

  Therefore, it is difficult to find a leak in the tank even if the inventory quantity obtained from the detection value of the liquid level gauge (hereinafter referred to as the "detected inventory quantity") and the calculated inventory quantity are compared, and various errors occur. It requires a considerable amount of skill to detect a leak based on a measurement value including a value, and it has been extremely difficult to quickly detect a small amount of error.

  The present invention makes it possible to estimate the error of the liquid level gauge installed in the tank based on the new knowledge of the inventors, so that the inventory quantity of the tank can be further improved from the detected value of the liquid level gauge. It provides a means that can be accurately estimated, enabling more accurate and speedy leak detection from tanks and piping connected to the tanks, and more accurately measuring the inventory quantity of individual tanks. Therefore, it is an object to make it possible to monitor the operating state of the tank in a steady state and in an emergency more promptly and accurately.

  The present invention provides a new finding that the error of a liquid level gauge installed in an oil tank buried underground fluctuates finely in a short time interval p and periodically fluctuates between an upper limit and a lower limit as a whole. It was made based on. According to the present invention, a calibration function for approximating the true stock amount from the stock amount detected by the liquid level gauge based on the measurement data of the past liquid level gauge 4 and the liquid level meter 5 for measuring the output amount from the tank. For each tank to estimate the true inventory.

  The method for measuring the stock quantity in the liquid tank of the present invention includes a liquid level gauge 4 installed in the tank 2 for detecting the stock quantity of the liquid in the tank, and a liquid level gauge for measuring the quantity of the liquid discharged from the tank 2. It is a method of measuring the inventory quantity of a liquid tank provided with a quantity meter 5.

  In the method of the present invention, the detection data of the liquid level gauge 4 received at each predetermined time interval p and the delivery amount measured by the liquid level meter 5 within the time interval are stored, and the stored data of the predetermined period is stored. The relationship between the true stock amount of the liquid in the tank 2 and the detected stock amount detected by the liquid level gauge 4 is estimated, and the detection data of the liquid level gauge 4 is corrected based on the estimated relationship to inventory the tank. The amount.

A preferred apparatus for carrying out the method of the present invention is a memory for storing the detected stock quantity x _t calculated by the calculation means 15 at predetermined time intervals p and the corrected stock quantity X _t after being corrected by the deviation correcting means 32. Means 34, small section setting means 38 for dividing a section of data used to obtain a calibration function from the data stored in the storage means into small sections s, and a calibration function obtained from the data of the divided small sections. And a deviation correcting means 32 for correcting the detected inventory quantity newly acquired by the calibration function obtained by the learning means to obtain the corrected inventory quantity. There is.

  In the underground tank monitoring system of the present invention, the management computer 3 and the detection value of the liquid level gauge 4 or the detected inventory quantity calculated by the calculation means 15 and the liquid meter 5 correspond to each predetermined time interval p. A transmitter 16 for transmitting the delivery quantity measured within the interval p to the management computer 3 via the Internet 6 is provided, and the inventory quantity measuring device of the present invention and the time axis are stored in the storage means with the horizontal axis. The management computer 3 is provided with a display unit 36 for displaying the corrected inventory quantities for a plurality of days in a graph.

  The width or number of the small sections s set in the small section setting means 38 is the order of detection of the fluctuation cycle of the detection error of the liquid level gauge from the stored data of the predetermined section and the order of the calibration function to be obtained. The width of the small section s to be divided can be obtained and automatically set.

  According to the present invention, not only the leak from the main body of the underground tank but also the leak from the buried pipe connected to the underground tank can be accurately detected. Further, it is possible to promptly detect an error or malfunction of a measuring instrument such as a liquid level meter or a liquid level gauge, and to monitor the operating state of the tank in a steady state and an emergency.

  Further, since the present invention can collect data using existing equipment such as a liquid level meter, a liquid level meter, and wiring connected to them, it can be introduced at low cost and the operation cost is low.

  Further, according to the monitoring system of the present invention, for a plurality of tanks, the corrected inventory amount obtained from the detected inventory amount of the liquid level gauge, the output amount by the liquid level meter, and if necessary, the storage amount from the tank truck are promptly managed. Since it is automatically sent to the computer and the results are displayed, it is possible to establish a system in which a skilled analyst constantly monitors.

Graph showing an example in which the deviation of the inventory detected by the liquid level gauge fluctuates periodically Block diagram of a general gas station equipped with the monitoring system of the present invention Graph (b) of corrected inventory amount corrected by the method of the present invention and graph (a) of detected inventory amount before correction A graph that measures the error of the detected inventory quantity of the liquid level gauge with the inventory quantity as the horizontal axis for four underground tanks

  Embodiments of the present invention will be described below with reference to the accompanying drawings. When the inventors of the present application measured in detail the changes in the stock amount and the output amount of the oil tank buried underground, the error of the stock amount detected by the liquid level gauge was measured at each measurement, as shown in FIG. It has been found that it changes finely and periodically fluctuates between an upper limit and a lower limit as a whole. The horizontal axis of FIG. 1 indicates the passage of time, the left vertical axis indicates the stock amount (broken line), and the right vertical axis indicates the error between the detection value of the liquid level gauge and the theoretical value (solid line) for 3 days measured every 5 minutes. Shows the data.

  Based on this knowledge, the inventors of the present application can correct the error in the detected inventory amount by learning the relationship between the inventory amount detected by the liquid level gauge (detected inventory amount) and the true inventory amount by the method of AI. The invention of the present application was completed based on the idea that it might be.

  According to the present invention, a calibration function for obtaining the true inventory amount from the detected inventory amount is obtained for each underground tank based on the past measurement value. In the present embodiment, the calibration function is obtained by applying the cubic spline regression of the non-parametric regression analysis of the machine learning method that approximates a complicated function form.

That is, x is the detected stock amount, and at the detection time point t = 2, ..., T,
f (x _t = f (x _t−1 ) + accepted amount at−delivered amount bt
A function (calibration function) that is close to the function f (x _t ) is obtained by cubic spline regression to correct the deviation between the detected inventory amount and the true inventory amount, and by monitoring the corrected inventory amount, the underground tank Manage health.

  It is difficult to find a calibration function corresponding to a phenomenon with a complicated curved structure. However, the periodicity of the deviation between the change in the detected inventory amount found by the inventors of the present application and the change in the inventory amount calculated from the output amount (calculated inventory amount) is added, and the predetermined interval used for obtaining the calibration function is added. The complex data structure is modeled by dividing the data group of 2 into a plurality of small sections s, a polynomial that applies to the measured data is found for each small section, and for example, the boundary between adjacent small sections is moved to obtain for each small section. By connecting the ends of the polynomial, an appropriate calibration function could be obtained from the measured data of the complex structure.

By dividing the section in which the data used to obtain the calibration function is collected according to the amount of the data, m−1 small sections s are set, and the m sections that are the boundaries of these small sections are t ₁ · as ·· t _m, calibration function by cubic spline regression

の係数ｗ₀、ｗ₁、ｗ₂、ｗ₃、ｗ_j+3（ｊ＝１・・・ｍ）を求めて、検出在庫量ｘを補正して真の在庫量とするのである。

Seeking coefficients w _{0 of, w 1, w 2, w} 3, w j + 3 (j = 1 ··· m), by correcting the detected stock amount x is to the true inventory.

  The above-described stock amount correction calculation can be performed at any stage in the process of displaying the true stock amount from the detection value of the liquid level gauge. An embodiment of the present invention will be described below with reference to FIG. 2 and subsequent figures showing an example in which the management computer 3 monitors the soundness of an underground tank 2 provided in a general gas station. FIG. 2 is a diagram schematically showing a general gas station, in which a tank 2 is buried under the site where the building 1 is built. Petroleum (for example, gasoline) is stored in the tank 2, and the position of the liquid level thereof is detected by the liquid level gauge 4. The tank 2 includes an entrance 21 and an exit 22. Petroleum in the tank 2 is received from the tank truck 23 through the storage port 21, and is supplied from the storage port 22 through the buried pipe 24 to the consumer (usually an automobile) from the refueling machine 25. The refueling machine 25 is provided with a liquid level meter 5 for measuring the amount of petroleum that has flown out from the refueling nozzle 26. Although only one tank 2 and one refueling machine 25 are shown in the figure, a plurality of tanks 2 and refueling machines 25 are usually provided.

  The liquid level gauge 4 converts the detected position of the liquid level of petroleum into an electric signal and sends it to a monitor 11 installed in the building 1 through a signal line 7. The monitor 11 shown in the figure is a monitor having a conventional structure, and calculates the stock quantity of petroleum in the tank from the position of the liquid surface and displays it on the display 12. This calculation is a calculation based on a calculation formula that theoretically determines the relationship between the inner dimension of the tank and the position of the liquid surface.

  The liquid amount meter 5 provided in the fuel filler 25 converts the output amount measured when refueling is performed into an electric signal and sends it to the POS terminal 13. The POS terminal 13 calculates a price based on the received weighing signal, exchanges money, and sends sales data to a computer of a POS system (not shown). The POS terminal 13 may be built in the refueling machine 25 or may be installed in the building 1. The input terminal 14 of the POS terminal and the transmitter 16 provided in the monitor 11 are connected by the branch signal line 8, and the measurement signal sent from the liquid level meter 5 to the POS terminal 13 is sent by the branch signal line 8. , To the transmitter 16.

  Note that the transmitter 16 acquires the detection value of the liquid level meter 5 from the input end 14 of the POS terminal because when it is acquired from the data processed by the POS terminal 13, the data such as the sales amount of the gas station is included. This is because, on the other hand, in the method of directly collecting data from the liquid volume meter 5, a large number of new wirings are required.

  The general monitor 11 displays a display 12, a calculation means 15 for calculating the stock amount theoretically from the detection value of the liquid level gauge 4, and a calculation result of the calculation means 15 on the display 12. A display means and a warning means for displaying a warning when the calculation result becomes less than or equal to a predetermined amount are provided. The monitor 11 of the embodiment further includes a transmitter 16.

  The transmitter 16 transmits the inventory amount calculated by the calculation unit 15 of the monitor to the management computer 3 installed in the management company 9 at preset short time intervals (for example, at intervals of 3 to 30 minutes, preferably 3 to 10 minutes). To do. The transmitter 16 also divides the weighing signal input from the branch signal line 8 into a predetermined data amount (for example, about 1 kbyte), and transmits the division signal to the management computer 3 via the Internet at each division timing.

  The management computer 3 includes a receiver 31, a deviation correction means 32, a storage amount calculation means 33, a storage means 34, a Web page creation / transmission means 35, a display means 36, a learning means 37 and a small section setting means 38. There is.

The receiver 31 receives the data transmitted at a predetermined time interval p from the transmitter 16 of the monitor. The storage unit 34 stores the detected inventory amount x _t received at each time and the corrected inventory amount X _t after being corrected by the deviation correcting unit 32.

A small section s corresponding to the order of the calibration function to be obtained is set in the small section setting means 38. When the small section s is automatically set, a small section calculation is performed to detect a cycle in which the difference between the leveled detected inventory quantity and the calculated inventory quantity in the past predetermined section has an extreme value and calculate the corresponding small section s. Means 39 are provided. The learning means 37 obtains the calibration function f (x _t ) by the above-described machine learning method.

Deviation correcting unit 32, the calibration function learning unit 37 is determined, obtaining the correction amount of inventory X _t by correcting the detected stock amount x _t newly received. The new detected inventory amount, the corrected inventory amount, and the measurement data are sequentially stored in the storage unit 34.

The display means 36 displays a graph of the stored corrected inventory quantity X _t on the monitor of the management computer 3 with the horizontal axis as the time axis. The web page creation / transmission means 35 creates a web page of the graph and uploads it to a web server (not shown). The person in charge at the gas station can browse the Web page with the browser 17 given the browsing authority.

  FIG. 3A is a graph of detected inventory amount-calculated inventory amount (before correction), and FIG. 3 (b) is a graph of detected inventory amount-calculated inventory amount (after correction). The correction used reduces the standard deviation of the difference between the actual inventory and the calculated inventory by 54%. In the graph (a) before the correction, the original error is mixed due to the error in the display deviation of the liquid level gauge, and it is difficult to judge the tank abnormality such as leakage. On the other hand, in the corrected graph (b), errors other than the liquid level error such as the existence of the tank back due to the verification of the liquid level meter remain, but since the deviation of the detected stock amount of the liquid level meter is removed, Error becomes clear and it becomes easy to judge the tank abnormality.

  Based on the data displayed on the display of the management company 9, the monitoring person or analyst of the management company 9 promptly detects abnormal operation of the measuring instruments 4 and 5 or leakage from the underground tank 2 or the buried pipe 24. It is also possible to detect the deformation of the tank due to the earthquake by analyzing the data for several days.

  It should be noted that there is a relation between the cycle of error change, the division width when dividing into small sections s, and the obtained calibration function, and if the division is performed in a small section of 1.5 times the period, a quadratic calibration function is obtained. In addition, for the data at the start and the end, the error in a short cycle can be corrected by averaging the data measured at short intervals.

  When the existing monitor 11 is not used, the transmitter 16 directly transmits the detection value of the liquid level gauge 4, and the calculation means 15 for calculating the inventory amount from the detection value of the liquid level gauge and the calculation result are predetermined. Warning means for generating a warning when the quantity becomes less than or equal to the quantity can be provided on the management computer 3 side. Further, the storage unit 34, the small section setting unit 38, and the learning unit 37 of the present invention may be provided in the calculation unit 15 of the monitor 11 to correct the detected stock amount.

  By sending the measurement data to the browser of the manufacturer of the tank, an analyst having expert knowledge about the tank can check the shipping status, liquid leakage, and other abnormalities based on the sent data. A skilled analyst checks the measurement data for several days (for example, three days), so that it is possible to promptly respond when an abnormality occurs. Leakage monitoring becomes easier by cutting out the data only during the night when warehousing is not performed. Further, by displaying the deviation data for each tank, it is possible to find a manufacturing problem of each tank.

  4 (a), (b), (c), and (d) show how the deviation of the detected stock quantity of the level gauge detected by the method of the present invention changes for four different underground tanks. Is a graph showing the inventory quantity in the tank on the horizontal axis.

  In the tank of FIG. 4 (a), the increase / decrease amount tends to be positive when the inventory amount increases, and the increase / decrease amount tends to be negative when the inventory amount decreases, and the difference in size between the liquid level gauge and the tank (smaller tank size) Presumed to be.

  In the tank of FIG. 4B, the increase / decrease amount tends to be negative when the inventory amount increases, and the increase / decrease amount tends to be positive when the inventory amount decreases. This is presumed to be due to the difference in size between the liquid level gauge and the tank (the tank size is larger).

  In the tank of FIG. 4 (c), the tendency of the increase / decrease amount is reversed when the stock amount is about half of the total volume, and it is presumed that the displacement of the installation position of the liquid level gauge is the cause.

  In the tank of FIG. 4D, the tendency of error inversion is seen at a plurality of places, and it is presumed that the difference in the tank table of the liquid level gauge is the cause.

2 Tank 3 Management Computer 4 Liquid Level Meter 5 Liquid Level Meter 6 Internet 13 POS Terminal 14 Input Terminal 16 Transmitter 32 Deviation Correction Means 33 Storage Volume Calculation Means 34 Storage Means 36 Display Means 37 Learning Means 38 Small Section Setting Means 39 Small Section Computing means

Claims (6)

A liquid level meter (4) installed in the tank (2) for detecting the stock amount of the liquid in the tank, and a liquid level meter (5) for measuring the delivery amount of the liquid from the tank were provided. A method of measuring the inventory quantity of a liquid tank,
The detection data of the liquid level gauge received at each predetermined time interval (p) and the warehousing amount measured by the liquid level meter within the time interval are stored, and the data of the stored predetermined period is stored in the tank. The relationship between the true stock quantity of liquid and the detected stock quantity detected by the level gauge is estimated, and the detection data of the level gauge is corrected based on the estimated relationship to calculate the stock quantity of the tank. , How to measure inventory in liquid tanks.   The estimation of the relationship between the true inventory amount and the detected inventory amount detected by the liquid level gauge includes the step of detecting the fluctuation cycle of the detection error of the liquid level gauge from the stored data of the predetermined period, and the detected cycle. The tank according to claim 1, further comprising a step of dividing the period into small sections (s) based on the above, and a step of connecting a calibration function for each small section to obtain a calibration function for performing the estimation. How to measure inventory. A liquid level gauge (4) installed in the tank (2) for detecting the liquid level of the liquid in the tank, and the detected inventory quantity is calculated based on the detected liquid level and the shape and size of the tank. A device for measuring the stock quantity of a liquid tank, comprising a calculation means (15) and a liquid quantity meter (5) for measuring the quantity of the liquid discharged from the tank,
Storage means (34) for storing the correction stock amount X _t corrected by the predetermined time interval detected stock amount x _t and deviation correction means said calculating means is calculated for each (p) (32),
A small section setting means (38) that divides the section of the data used to obtain the calibration function from the data stored in the storage means into small sections (s),
Learning means (37) for obtaining a calibration function for correction calculation by connecting the calibration functions obtained from the data of the partitioned small section (s),
The learning means is provided with deviation correction means (32) for obtaining the corrected inventory quantity by correcting the newly obtained detected inventory quantity with the calibration function.
Liquid tank inventory quantity measuring device.   The extreme value of the difference between the detected inventory quantity stored in the storage means (34) and the calculated inventory quantity calculated from the delivery quantity measured by the liquid level meter is calculated to obtain the extreme value of the small section width or the small section setting means. The liquid tank inventory amount measuring device according to claim 3, further comprising a small section calculating means (38) for setting the number of sections. A liquid level gauge (4) installed in the tank (2) for detecting the liquid level of the liquid in the tank, and the detected inventory quantity is calculated based on the detected liquid level and the shape and size of the tank. A monitoring system of a stock quantity of a liquid tank, which comprises a calculation means (15) and a liquid quantity meter (5) for measuring the delivery amount of the liquid from the tank,
The detection value of the liquid level gauge or the inventory amount calculated by the calculation means at every predetermined time interval (p) and the delivery amount measured within the time interval (p) corresponding to the liquid level meter via the Internet (6) A transmitter (16) for transmitting to a management computer (3) via a computer, the management computer comprising the measuring device according to claim 3 or 4, and a plurality of days stored in the storage means with a time axis as a horizontal axis. A monitoring system for an underground tank, comprising: a display means (36) for displaying the corrected inventory amount of a minute.   The underground tank monitoring system according to claim 5, wherein the transmitter acquires the measurement data of the liquid level meter from an input end (14) of a POS terminal connected to the liquid level meter.

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