Method for online calibration of tank gauges

Abstract

The present application relates to a kind of methods for verifying the online tank capacity table, extract the history liquid level of gas station liquid level instrument platform oil tank and the sales flow data of gas dispenser, establish the corresponding relationship between the oil product liquid level height in gas station oil tank and the oil product volume amount emitted by gas gun;Considering the temperature influence and the indication error of gas gun, after the compensation correction of tank oil product and sales oil product volume, the corresponding relationship between oil tank height and cumulative volume amount is established;System fitting is realized by applying measurement model, and new capacity table with centimeter interval corresponding verification interval is generated.The advantage of the present application is to specify verification specification operation, to generate oil tank volume table automatically through temperature compensation, oil gun indication error reduction after sales flow uploaded automatically by gas station liquid level instrument platform, to avoid the influence of oil product volume expansion coefficient, oil product measurement temperature, liquid level instrument equipment error, oil product liquid level fluctuation, gas dispenser calibration result uncertainty, gas dispenser oil product emission temperature and other uncertain components on verification result.

Description

Technical Field

[0001] This invention belongs to the field of oil tank calibration technology, specifically relating to a method for online calibration of oil tank capacity tables. Background Technology

[0002] As gas station management becomes increasingly refined, oil companies are demanding higher accuracy in their inventory management. Gas station tank capacity tables are fundamental to the handover of underground tanks and the standardized management of losses and gains. After the initial tank calibration, because most oil storage tanks used in domestic gas stations are initially buried and then used long-term, settlement, tilting, and deformation inevitably occur during actual operation, leading to errors in the capacity tables. This results in inaccurate capacity tables at some gas stations, introducing significant uncertainty into gas station operations and hindering the accuracy of basic data in the oil company's information technology infrastructure. Therefore, subsequent calibrations are necessary to adjust the inaccurate capacity tables caused by displacement, deformation, and other factors during tank use.

[0003] The current conventional calibration methods are geometric measurement methods or internal measurement methods. For details, please refer to GB / T17605-1998 "Verification Method of Horizontal Cylindrical Metal Tanks for Petroleum and Liquid Petroleum Products". This calibration method assumes that the tank body has a regular geometric shape. Based on the measurement of geometric characteristic parameters, the calculation formulas for capacity and height are derived, and the volume occupied by the contents of the tank is averaged throughout. A volume table is formed by using 10mm height-volume data pairs.

[0004] For existing automated calibration methods, please refer to patents US4977528 "Equipment and Method for Calculating the Material Capacity in an Oil Tank", US5544518 "System and Method for Calibrating Various Tanks", and US5665895 "System and Method for Calibrating Storage Tanks". These three patents represent progressive, step-by-step optimization methods, exhibiting consistency in their technical implementation. The principle behind automated calibration is as follows: assuming a regular oil tank shape, the system directly connects to the fuel dispenser flow meter to acquire dispensing data. Through automated methods, using a volume comparison method, it fits the geometric feature model of the oil tank and derives various tank parameters. Based on these parameters, appropriate standard calculation formulas are applied to calculate the volume table for each point. The main geometric features include: 1) tank length; 2) probe offset; 3) end cap shape; 4) diameter; and 5) inclination. This method is essentially an extended application of geometric measurement methods.

[0005] Clearly, the above calibration methods have the following drawbacks: Both geometric measurement and automated methods have strict requirements on the quality of the oil tank itself and are only applicable to standard oil tanks with regular shapes. They are unsuitable for non-standard tanks widely used in China, deformed tanks, and tank tilting caused by foundation settlement, thus severely limiting their applicability. Traditional geometric measurement methods for calibrating capacity meters have an uncertainty of 0.40%, which cannot meet the ±0.30% requirement for tank handover at gas stations, and can only be performed after the tank has been cleaned. In recent years, the widely adopted capacity comparison calibration method suffers from long operation times and high risks associated with calibrating with oil, primarily applicable to pre-opening calibration of newly built or renovated gas stations, and is also expensive. Therefore, there is an urgent need for a safe, economical, convenient, efficient, accurate, and reliable method for verifying the accuracy of capacity meters. Summary of the Invention

[0006] The purpose of this invention is to address the problems existing in the prior art by proposing an online verification method for oil tank capacity tables. This method automatically generates oil tank capacity tables using sales data uploaded from a gas station level gauge platform. The new capacity tables generated by this method use corresponding verification intervals with centimeter intervals, resulting in high accuracy of the verification results.

[0007] To achieve the above objectives, the present invention provides a method for online verification of oil tank capacity tables, comprising the following steps:

[0008] Step 1: By extracting historical liquid level data from the gas station's liquid level gauge platform and sales data from the fuel dispensers, select the verification range that exceeds the set threshold, and establish the correspondence between the liquid level height in the gas station's liquid tank and the volume of oil dispensed from the fuel dispenser.

[0009] Step 2: Based on the correspondence between the oil level height and the volume of oil dispensed by the refueling gun established in Step 1, and considering the error of the refueling gun reading and the influence of temperature, after compensating and correcting the volume of oil stored in the tank and the volume of oil sold, establish the correspondence between the tank height and the cumulative volume after compensation and correction.

[0010] Step 3: Apply the measurement model to fit the system and generate a new capacity table with corresponding verification intervals in centimeters.

[0011] Furthermore, the formula for the measurement model in step 3 is as follows:

[0012]

[0013] In the formula, V 20 Vh represents the volume value at 20℃ corresponding to a liquid level height of h in the horizontal oil tank, and V0 represents the original oil tank volume table value corresponding to a starting height of h0 under the horizontal oil tank volume verification. jβ represents the actual volume of fuel dispensed by the fuel dispenser when the liquid level in the horizontal oil tank is between h0 and h. y This represents the coefficient of thermal volume expansion of oil stored in oil tanks, β. g t represents the coefficient of thermal volume expansion of the horizontal oil tank body, t0 represents the average temperature of the oil in the tank when the liquid level is h0, and t1 represents the average temperature of the oil in the tank when the liquid level is h. j E represents the weighted average temperature of the fuel dispensed by the fuel dispenser when the liquid level in the horizontal fuel tank is between h0 and h. j This indicates the calibration error of the fuel dispenser.

[0014] Furthermore, in step 2, the volume compensation correction for tank-stored oil refers to compensating for the volume difference of tank-stored oil according to formula (1) based on the temperature changes in the oil tank during the sales process.

[0015] Furthermore, in step 2, compensating for the volume of oil sold refers to compensating for the temperature difference and sales error volume of the oil stored in the tank and the oil sold, according to formula (1), based on the changes in sales temperature during the sales process and the comprehensive error of the fuel dispenser.

[0016] Furthermore, in step 2, when establishing the correspondence between the tank height and the cumulative volume, the tank level is used as the horizontal axis and the cumulative volume is used as the vertical axis to draw a curve showing the relationship between the height and the cumulative volume, thereby generating a new capacity table with corresponding verification intervals in centimeters.

[0017] Furthermore, online verification of oil tank capacity tables must meet the following conditions:

[0018] (1) The oil tank is not severely deformed and is installed on a stable base. It does not shift during oil receiving and dispensing operations.

[0019] (2) The slope of the oil tank unloading pipeline meets the design specifications and does not affect the normal return of the remaining oil in the pipeline to the tank after unloading.

[0020] (3) The oil tank level gauge is firmly installed and there is no visible displacement during use. The equipment has a metering tolerance of ±0.5mm for level and ±0.2℃ for average output temperature.

[0021] (4) The standard metal measuring instrument used for fuel dispenser calibration shall be no less than 50L and the accuracy class shall be no less than Class II; the minimum scale division of the thermometer shall be 0.1℃ and the maximum allowable deviation shall be ±0.2℃; the vapor recovery device shall be in good condition and shall be connected during fuel dispenser calibration.

[0022] (5) Correct the calibration error when using the fuel dispenser; the fuel dispenser calibration should use the maximum flow rate point data and be carried out in a quantitative manner. Temperature correction should be performed during calibration; for fuel dispensers that have not been refueled for a long time, the calibration data should be calculated from the second container.

[0023] (6) If the liquid level difference in the corresponding interval is greater than 1.2m, the verification result will only provide the tank capacity data within the verification interval; the capacity data within 50mm of the upper and lower points of the verification height will not be used.

[0024] (7) No refueling or oil return operations shall be carried out during the oil stabilization period after the oil stabilization period ends; the oil receiving and acceptance operations shall be carried out in a timely manner after the oil stabilization period ends; during the oil tank calibration data collection period, there shall be no operations that affect data analysis, such as fuel dispenser calibration or oil return.

[0025] (8) The historical liquid level curve of the oil tank is complete in the liquid level gauge system;

[0026] (9) Verify twice, and take the average of the cumulative capacity within the common interval.

[0027] This invention is based on the sales volume and height of fuel dispensers and corresponding tanks at gas stations. After compensating for temperature difference and sales volume errors by considering tank temperature variations and overall fuel dispenser errors, it performs trend fitting between liquid level height and corresponding volume to generate a new tank capacity table. During the calibration process, only the start and end dates need to be specified; data analysis, calculation, and tank capacity table generation are automatically completed, with calibration time for a single tank within 10 minutes. Verification shows that the capacity tables adjusted using this method achieve an accuracy of ±0.15% for over 90% of tanks, ±0.20% for over 95% of tanks, and ±0.30% for over 99.5% of tanks, providing crucial support for gas station tank handover and loss / gain management. The tank capacity table is valid for 4 years and requires calibration / verification every 4 years. Currently, the cost of capacity comparison verification is approximately 2500 yuan per tank, demonstrating significant cost reduction.

[0028] Furthermore, the present invention also includes uncertainty assessment of the new capacity table, including: Type A assessment of measurement uncertainty, Type B assessment of measurement uncertainty, assessment of combined standard uncertainty, and assessment of expanded uncertainty.

[0029] Furthermore, taking the commonly used 30m gas station 3 Taking oil tanks as an example, the same oil tank is calibrated three times, the maximum cumulative capacity difference within the interval is calculated, the standard uncertainty is calculated using the range method, and the measurement uncertainty is assessed as Type A.

[0030] The formula for Type A evaluation of measurement uncertainty is as follows:

[0031] S(x) = R / C

[0032] In the formula, S(x) refers to the Type A standard uncertainty, R refers to the maximum cumulative capacity difference within the tank range, and C refers to the range coefficient.

[0033] Furthermore, the uncertainties affecting the verification results are analyzed, including: the uncertainty component u(V0) caused by the uncertainty of the starting liquid level height at the low liquid level, and the uncertainty component u(β) caused by the oil expansion coefficient in the horizontal tank. y The uncertainty component u(t1) is introduced due to the uncertainty of the high liquid level starting temperature, the uncertainty component u(t0) is introduced due to the uncertainty of the low liquid level starting temperature, and the uncertainty component u(V) is introduced due to the uncertainty of the accumulated pump code of the fuel dispenser. j The uncertainty component u(E) introduced by the uncertainty of the fuel dispenser calibration (verification) results. j The fuel dispenser outputs an uncertain component u(t) caused by the measurement of fuel temperature. j The uncertainty component u(β) introduced by the volume expansion of the oil tank body g The uncertainty component u(V) introduced by the simplification of the data model m );

[0034] The formula for Type B evaluation of measurement uncertainty is as follows:

[0035]

[0036] In the formula, [u c (V 20 )] 2 Let be the combined variance of the Type B standard uncertainty, and c be the propagation coefficient corresponding to the uncertain component.

[0037] Furthermore, based on the Type A uncertainty assessment and the Type B uncertainty assessment, a combined standard uncertainty assessment is performed;

[0038] The formula for evaluating the combined standard uncertainty is as follows:

[0039]

[0040] In the formula, u is the combined standard uncertainty, and S(x) refers to the Type A standard uncertainty. The combined variance of the type B standard uncertainty.

[0041] Furthermore, based on the assessment of combined standard uncertainty, the expanded uncertainty is calculated;

[0042] The formula for expanded uncertainty is as follows:

[0043] U = ku

[0044] In the formula, U is the expanded uncertainty of the tank capacity verification result, u is the combined standard uncertainty, and k is the coverage factor;

[0045] The relative expanded uncertainty U of the oil tank inspection results rel The formula is as follows:

[0046] U rel =U / Tank area capacity.

[0047] This invention clarifies the standard operating procedure for verification and automatically generates a tank volume table by using sales data automatically uploaded from the gas station level gauge platform, after temperature compensation and restoration of fuel nozzle indication error. This avoids the influence of uncertain components such as the volume expansion coefficient of oil, oil measurement temperature, level gauge equipment error, oil level fluctuation, uncertainty of fuel dispenser calibration results, and temperature of oil emitted from the fuel dispenser on the verification results. Detailed Implementation

[0048] Preferred embodiments of the invention will now be described in more detail. While preferred embodiments of the invention are described below, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein.

[0049] The online verification method for oil tank capacity tables of the present invention includes the following steps:

[0050] Step 1: By extracting historical liquid level data from the fuel tank and sales data from the fuel dispenser on the gas station's liquid level gauge platform, select the verification range that exceeds the set threshold, and establish the correspondence between the liquid level height in the fuel tank and the volume of fuel dispensed from the fuel dispenser, corresponding to the direct data of liquid level and fuel dispenser volume.

[0051] Step 2: Based on the correspondence between the oil level height and the volume of oil dispensed by the refueling gun established in Step 1, and considering the error of the refueling gun reading and the influence of temperature, after compensating and correcting the volume of oil stored in the tank and the volume of oil sold, establish the correspondence between the tank height and the cumulative volume after compensation and correction. The relationship between the height and volume of the corresponding tank is the basic data information of the tank capacity table.

[0052] Step 3: Apply the measurement model to fit the system and generate a new capacity table with corresponding verification intervals in centimeters.

[0053] This invention is based on computational logic to complete software development. Addressing the issue of significant data loss in sales records on gas station level gauge platforms, it adds a sales record upload function. Sales records for the corresponding sales period are exported from the fuel card system and directly uploaded to the system, which automatically fills in the missing fuel dispenser sales record data from the level gauge system. To ensure data accuracy and reliability, this invention clearly defines the verification procedures.

[0054] Step 1 establishes the correspondence between the fuel level in the gas station's tank and the volume of fuel dispensed from the fuel dispenser. Step 2 involves compensating for the volume of fuel stored in the tank based on temperature changes during the sales process, and compensating for temperature differences and sales errors based on changes in sales temperature and the overall error of the fuel dispenser. When establishing the correspondence between tank height and cumulative volume, a curve is plotted with the tank level on the x-axis and the cumulative volume on the y-axis, generating a new capacity table with corresponding verification intervals in centimeters.

[0055] In step 3, the formula for the measurement model is as follows:

[0056]

[0057] In the formula, V 20 Vh represents the volume value at 20℃ corresponding to a liquid level height of h in the horizontal oil tank, in L; V0 represents the original oil tank volume table value corresponding to a starting height of h0 under the horizontal oil tank volume verification, in L; V0 j This represents the actual volume of fuel dispensed by the fuel dispenser when the liquid level in the horizontal oil tank is between h0 and h, expressed in L; β y This indicates the coefficient of thermal expansion of the oil stored in the tank; for gasoline, it is 0.0012, and for diesel, it is 0.0008, in °C. -1 ;β g This represents the coefficient of thermal expansion of the horizontal oil tank body; for carbon steel: 33 × 10⁻⁶. -6 ℃ -1 t0 represents the average temperature of the oil in the horizontal oil tank when the liquid level is h0, in °C; t1 represents the average temperature of the oil in the horizontal oil tank when the liquid level is h, in °C; t j E represents the weighted average temperature of the fuel dispensed by the fuel pump when the liquid level in the horizontal fuel tank is between h0 and h (the fuel temperature dispensed by the fuel pump is the real-time average temperature of the fuel in the tank at the time of refueling), in °C; j This indicates the fuel dispenser calibration error, expressed as a percentage.

[0058] To ensure the accuracy of the verification results, the metering equipment and operations must meet the following conditions during the online verification process of the oil tank capacity meter:

[0059] (1) The oil tank is not severely deformed and is installed on a stable base. It does not shift during oil receiving and dispensing operations.

[0060] (2) The slope of the oil tank unloading pipeline should meet the design specifications and should not cause local subsidence or deformation of the pipeline due to external forces, which would affect the normal return of the remaining oil in the pipeline to the tank after unloading.

[0061] (3) The oil tank level gauge is firmly installed and there is no visible displacement during use. The equipment measurement tolerance meets the requirements of ±0.5mm for liquid level and ±0.2℃ for average output temperature.

[0062] (4) The standard metal measuring instrument used for fuel dispenser calibration shall be no less than 50L and the accuracy class shall be no less than Class II; the minimum scale division of the thermometer shall be 0.1℃ and the maximum allowable deviation shall be ±0.2℃; the vapor recovery device shall be in good condition and shall be connected during fuel dispenser calibration.

[0063] (5) The metering performance of the fuel dispenser meets the requirements of the "Verification Procedure for Fuel Dispensers". The verification (calibration) error shall be corrected during use. The fuel dispenser calibration shall use the maximum flow point data and be carried out in a quantitative manner. Temperature correction shall be performed during the calibration (calibration). For fuel dispensers that have not been dispensed for a long time, the calibration data shall be calculated from the second container.

[0064] (6) If the liquid level difference in the corresponding interval is greater than 1.2m, the verification result only provides the tank capacity data within the verification interval; the capacity data within 50mm of the upper and lower points of the verification height is not recommended.

[0065] (7) Gas stations shall conduct regular incoming goods inspection. During the oil stabilization period, refueling and oil return operations shall not be carried out. After the oil stabilization period ends, incoming goods inspection operations shall be carried out in a timely manner. During the oil tank calibration data collection period, there shall be no operations that affect data analysis, such as fuel dispenser calibration and oil return.

[0066] (8) The historical liquid level curve of the oil tank is complete in the liquid level gauge system;

[0067] (9) It is recommended to perform two verifications, and the cumulative capacity of the verification should be the average of the cumulative capacity within the common interval.

[0068] This invention performs measurement uncertainty analysis and evaluation on a new capacity meter, including: Type A evaluation of measurement uncertainty, Type B evaluation of measurement uncertainty, evaluation of combined standard uncertainty, and evaluation of expanded uncertainty.

[0069] (1) Type A assessment of measurement uncertainty

[0070] The formula for Type A evaluation of measurement uncertainty is as follows:

[0071] S(x) = R / C

[0072] In the formula, S(x) refers to the Type A standard uncertainty, R refers to the maximum cumulative capacity difference within the tank range, and C refers to the range coefficient.

[0073] Gas stations typically use 30m 3 Taking oil tanks as an example, the same oil tank was calibrated three times, and the data is shown in Table 1.

[0074] Table 1 Height Capacity Comparison Table

[0075]

[0076] Due to the inconsistent starting height of the liquid level in each calibration, the centimeter capacity table ranges generated by the three calibrations were (360-2080) mm, (700-2060) mm, and (610-2040) mm, respectively. The range (700-2000) mm, which was covered by all three calibrations, was taken for comparison. The cumulative capacity of 700 mm was set to zero. The cumulative capacity difference data is shown in Table 2 (with 100 mm intervals).

[0077] Table 2. Cumulative Capacity Difference Statistics

[0078]

[0079] The maximum cumulative capacity difference within the interval is 12.677 liters. Using the range method to calculate the standard uncertainty, and taking a range coefficient of 1.69, we get:

[0080] S(x) = 12.677 / 1.69 = 7.502L

[0081] (2) Type B evaluation of measurement uncertainty

[0082] The uncertainties affecting the verification results are analyzed, including: the uncertainty component u(V0) caused by the uncertainty of the starting liquid level height at the low liquid level, and the uncertainty component u(β) caused by the oil expansion coefficient in the horizontal tank. y The uncertainty component u(t1) is introduced due to the uncertainty of the high liquid level starting temperature, the uncertainty component u(t0) is introduced due to the uncertainty of the low liquid level starting temperature, and the uncertainty component u(V) is introduced due to the uncertainty of the accumulated pump code of the fuel dispenser. j The uncertainty component u(E) introduced by the uncertainty of the fuel dispenser calibration (verification) results. j The fuel dispenser outputs an uncertain component u(t) caused by the measurement of fuel temperature. j The uncertainty component u(β) introduced by the volume expansion of the oil tank body g The uncertainty component u(V) introduced by the simplification of the data model m ).

[0083] The formula for Type B evaluation of measurement uncertainty is as follows:

[0084]

[0085] In the formula, [u c (V 20 )] 2Let be the combined variance of the Type B standard uncertainty, and c be the propagation coefficient corresponding to the uncertain component.

[0086] Summary of Type B Standard Uncertainty c =23.337L.

[0087] (3) Evaluation of combined standard uncertainty

[0088] The formula is as follows:

[0089]

[0090] In the formula, u is the combined standard uncertainty, and S(x) refers to the Type A standard uncertainty. The combined variance of the type B standard uncertainty.

[0091] u = 24.514L.

[0092] (4) Expanded uncertainty

[0093] The formula is as follows:

[0094] U = ku

[0095] In the formula, U is the expanded uncertainty of the tank capacity verification result, u is the combined standard uncertainty, and k is the coverage factor;

[0096] The relative expanded uncertainty U of the oil tank inspection results rel The formula is as follows:

[0097] U rel =U / Tank area capacity.

[0098] Taking a coverage factor k = 2, the expanded uncertainty of the horizontal tank capacity verification result is U = 49.028L; for a commonly used 30m... 3 The interval capacity is 23599.577L, and the relative expanded uncertainty U of the verification result is... rel =0.208% (k=2).

[0099] The online verification method for oil tank capacity tables of the present invention establishes a data measurement model, completes measurement uncertainty analysis, and the relative expanded uncertainty U of the verification result. rel = 0.208% (k = 2).

[0100] Example 1

[0101] (1) Define the data source

[0102] Based on the historical data of gas station purchase and acceptance, the data range within a specified time interval that meets the verification condition of liquid level difference exceeding 1.2mm in claim 6(6) is automatically identified by the difference in liquid level height between adjacent purchase batches, and recorded as the verification interval.

[0103] Download historical trend lines of oil tanks and sales data of fuel dispensers from the level gauge system; to address the current issue of incomplete sales data for fuel dispensers in the level gauge system, add functions for controlling the upload of sales data and automatic data supplementation.

[0104] (2) Determination of verification points

[0105] ① Static liquid level

[0106] Based on the historical trend line of the oil tank level gauge, a level fluctuation of less than 0.2 mm for 12 consecutive times (the level gauge system takes data at 5-second intervals) is determined as a static level point. All static level points that meet the determination criteria within the verification interval are automatically identified.

[0107] ②High liquid level starting point

[0108] Based on the time of completion of the acceptance inspection of the oil tank for the gas station's level gauge, locate the highest static liquid level point 5 minutes in advance.

[0109] ③ Verification points

[0110] Starting from the highest liquid level point and moving downwards, take static liquid level points that have been continuously recorded for 50 or more consecutive times at intervals of (80-120) mm. The lowest liquid level point should be at least 50 mm away from the previous liquid level point. If the normal point selection conditions cannot be met, other static liquid level points should be found (for example, points with 45 or more consecutive static times can be selected by setting a 5-times decrease, provided that the interval range of (80-120) mm is ensured; a minimum threshold for consecutive static times can be set) to replace them (minor differences caused by the height of intermediate static liquid level points can be recovered when the system performs data fitting). If there are no static liquid level points that meet the requirements within the normal interval range, the upper limit of the interval can be appropriately relaxed to 150 mm.

[0111] (3) Data sent by the fuel dispenser is confirmed.

[0112] Based on the start and end times of the static liquid level point records and the start and end times of refueling in the fuel dispenser sales logs, the system automatically calculates the data emitted by the fuel dispensers between the automatically identified verification points. A common problem with current gas station liquid level gauge systems is that sales log records (including not only start and end refueling times, but also the corresponding tank level and temperature data, which are automatically matched and listed by the system) are sometimes missing. Therefore, by controlling the sales logs at the gas station (where the corresponding tank level and temperature data are missing), the system matches and verifies the TTC number against the sales log data in the liquid level gauge system. This allows for the data replenishment of missing sales log records in the liquid level gauge system, and the replenished sales log temperature is added based on historical liquid level gauge curve data before proceeding to the next calculation.

[0113] (4) Data processing

[0114] ① Cumulative tank capacity calculation

[0115] The calculation is performed according to formula (1), outputting the liquid level height of each corresponding verification point within the verification interval and the corresponding cumulative capacity of the oil tank. When calculating the cumulative capacity of the oil tank, firstly, the indication error of the fuel dispenser must be considered, and the quantity of oil sold within the corresponding height range of the fuel nozzle must be restored. Secondly, the temperature change factor during the sales process must be considered, and temperature compensation must be applied to the corresponding tank storage volume and sales volume. Then, based on the initial height, the corrected oil tank capacity corresponding to the verification point is calculated segment by segment.

[0116] ② Verification of data

[0117] After performing a high-order fitting of the liquid level height and its corresponding cumulative capacity at each verification point, the fitted capacity corresponding to each verification height point is recalculated based on the results of the high-order fitting. The difference between the cumulative capacity before and after fitting is compared. The difference is generally within ±2 liters. When the difference is greater than ±5 liters, it is determined that there is an anomaly in the data. The system will automatically perform a second point search and re-select the verification point for calculation.

[0118] ③ Tank capacity table generation

[0119] The system generates a capacity table for the corresponding verification interval by high-order fitting based on the relationship between the liquid level and tank capacity at each verification point.

[0120] ④ Analysis of inaccurate crude oil tank capacity tables

[0121] The system compares the oil output from tanks within the intervals of each verification point in the new and old capacity tables, and provides the deviation of the capacity tables for each interval, which helps users to better analyze and verify.

[0122] ⑤ Data Analysis Applications

[0123] Based on the analysis of the incoming goods data from the system's calibration capacity table, equipment and management deficiencies at gas stations can be identified in a timely manner. For example, there was a case where a significant loss of incoming goods was observed after calibration of a certain oil tank's capacity table. After investigation, it was found that the PV valve on the vent pipe of the gas station's vapor recovery tank had failed, leading to increased evaporation losses.

[0124] (5) System Operation

[0125] When planning to inspect oil tanks, it is necessary to first coordinate secondary logistics to ensure the delivery of oil products to the corresponding tanks. Under the premise of ensuring safety, try to ensure that the incoming goods are delivered to the highest liquid level, and then deliver them to the lower liquid level in one go (it is recommended not to exceed 300mm).

[0126] System login does not require logging into the external network and allows multiple users to operate simultaneously; the system supports single tank verification and simultaneous verification of multiple tanks, which can be selected as needed; operators enter information such as the station name according to the system prompts, and after confirmation, the system can automatically retrieve and calculate data.

[0127] Example 2

[0128] (1) Type B assessment of measurement uncertainty

[0129] The verification results are affected by uncertain components such as the volume expansion coefficient of oil, the expansion coefficient of oil tank, oil metering temperature, level gauge equipment error, oil level fluctuation, uncertainty of fuel dispenser verification results, and oil temperature emitted from fuel dispenser.

[0130] (1.1) Variance and Propagation Coefficient

[0131] 1) The variance can be obtained from equation (1) as the composite variance.

[0132]

[0133] In the formula, represents the combined variance of the Type B standard uncertainty; c1, c2, c3, c4, c5, c6, c7, c8, and c9 are all propagation coefficients; u(V0) refers to the uncertainty component caused by the uncertainty of the initial liquid level height at the low liquid level starting point; u(β) represents the uncertainty component caused by the uncertainty of the initial liquid level height at the low liquid level starting point. y The uncertainty component caused by the coefficient of thermal expansion of oil in the horizontal tank is u(t1), the uncertainty component introduced by the uncertainty of the high liquid level starting temperature is u(t0), and the uncertainty component introduced by the uncertainty of the low liquid level starting temperature is u(V). j ) refers to the uncertainty component introduced by the uncertainty of the accumulated pump code of the fuel dispenser, u(E) j ) refers to the uncertainty component introduced by the uncertainty of the fuel dispenser calibration (verification) results, u(t) j ) refers to the uncertain component caused by the fuel temperature measurement emitted by the fuel dispenser, u(β)g ) refers to the uncertainty component introduced by the volume expansion of the oil tank body, u(V m ) refers to the uncertainty component introduced by the simplification of the data model.

[0134] 2) Propagation coefficient

[0135] When calculating c1, the terms related to V0 are organized separately as follows:

[0136] V 20 =[V0(1+β) y (t1-t0))](1+β g (20-t1)) (3)

[0137] Taking the derivative to obtain the propagation coefficient, we have:

[0138] c1=[1+β y (t1-t0)](1+β g (20-t1)) (4)

[0139] The same principle applies:

[0140] Find β when c2 y Related items are listed separately as follows:

[0141]

[0142] Taking the derivative to obtain the propagation coefficient, we have:

[0143]

[0144] When calculating c3, ​​the relevant terms for t1 are summarized separately as follows:

[0145]

[0146] Taking the derivative to obtain the propagation coefficient, we have:

[0147]

[0148] When calculating c4, the terms related to t0 are summarized separately as follows:

[0149] V 20 =[V0β y (-t0)](1+β g (20-t1)) (9)

[0150] Taking the derivative to obtain the propagation coefficient, we have:

[0151] c4=-V0β y (1+β g (20-t1)) (10)

[0152] When finding c5, Vj Related items are listed separately as follows:

[0153]

[0154] Taking the derivative to obtain the propagation coefficient, we have:

[0155]

[0156] When finding c6, E j Related items are listed separately as follows:

[0157]

[0158] Taking the derivative to obtain the propagation coefficient, we have:

[0159]

[0160] When c7, t j Related items are listed separately as follows:

[0161]

[0162] Taking the derivative to obtain the propagation coefficient, we have:

[0163]

[0164] Find β when c8. g Related items are listed separately as follows:

[0165]

[0166] Taking the derivative to obtain the propagation coefficient, we have:

[0167]

[0168] u(V m To simplify the complexity of uncertainty analysis, some simplifications were made during data modeling, which introduced a certain degree of uncertainty into the measurement results, c9=1.

[0169] For ease of calculation, we input actual measurement data from an oil tank, taking V0 = 2512.410L; t1 = 23.1℃;

[0170] β y =0.0012℃ -1 t0 = 20.8℃; V j =23599.577L; E j =0.15%; β g =33×10 -6 ℃ -1 ;t j=21.8℃. The various propagation coefficients are as follows:

[0171] c1=1.0027; c2=36409; c3=30.4268; c4=-3.146; c5=1; c6=-23564; c7=-28.2742; c8=-80745.1567; c9=1.

[0172] (1.2) Standard uncertainty components

[0173] 1) Uncertainty component caused by the uncertainty of the starting liquid level height at low liquid level

[0174] The initial liquid level is affected by the measurement uncertainty of the level gauge itself and liquid surface fluctuations. The maximum permissible error of the level gauge is ±0.5mm. The system data acquisition conditions require liquid surface fluctuations to be less than ±0.2mm and to follow a uniform distribution. The normal starting liquid level is relatively low, corresponding to a capacity of approximately 12L / mm.

[0175] u(V0)=12*((0.5 / √3) 2 +(0.2 / √3) 2 ) 1 / 2 =3.7310L

[0176] Assuming the level gauge used for calibrating the tank capacity table is the same as the one actually in use, uncertainties caused by equipment installation are ignored here. 3 represents a uniform distribution, calculated as the standard deviation of a symmetrical rectangular distribution.

[0177] 2) Uncertainty component caused by the coefficient of expansion of oil in horizontal tank

[0178] According to relevant data, the uncertainty of the volumetric expansion coefficient of gasoline and diesel is 5 × 10⁻⁶. -6 ℃ -1 (k=2)

[0179] u(β y )=(5×10 -6 ℃ -1 ) / 2=2.5×10 -6 ℃ -1

[0180] 2 is the inclusion factor.

[0181] 3) Uncertainty component introduced by the uncertainty of the starting temperature of the high liquid level

[0182] The permissible average temperature deviation of oil output from a horizontal oil tank is ±0.5℃, and it follows a uniform distribution.

[0183] u(t1)=0.5 / √3=0.2887℃

[0184] 4) Uncertainty component introduced by the uncertainty of the low liquid level starting temperature

[0185] The permissible average temperature deviation of oil output from a horizontal oil tank is ±0.5℃, and it follows a uniform distribution.

[0186] u(t0)=0.5 / √3=0.2887℃

[0187] 5) Uncertainty component introduced by the uncertainty of the cumulative pump code of the fuel dispenser.

[0188] The minimum jump variable of the fuel dispenser pump code is 0.01L, the half-width of the interval is 0.005L, and it follows a uniform distribution.

[0189] u(V j )=0.005 / √3=0.0029L

[0190] 6) Uncertainty component introduced by the uncertainty of the fuel dispenser calibration (verification) results.

[0191] Based on on-site verification and relevant data, the uncertainty of fuel dispenser verification (calibration) is generally no greater than 0.07% (k=2).

[0192] u(E j ) = 0.07% / 2 = 0.035%

[0193] The maximum permissible tolerance for fuel dispensers specified in the national verification regulations includes the error at each flow point within the range of the flow rate. However, actual refueling typically involves high-flow rates, resulting in relatively fewer uncertainties. Furthermore, the volume dispensed by the fuel dispenser has been corrected for based on the verification (calibration) error at the maximum flow point during data calculation. Therefore, using the verification (calibration) uncertainty of the fuel dispenser to calculate the uncertain components is more reasonable than using the maximum permissible tolerance specified in the national verification regulations.

[0194] 7) Uncertain components caused by fuel temperature measurement from the fuel dispenser

[0195] The temperature of the fuel dispensed by the fuel pump is based on the temperature of the fuel stored in the tank. When the refueling interval is long, there will be some inconsistency between this temperature and the actual temperature of the fuel dispensed by the pump. According to on-site observation data, during non-continuous refueling, when the average single refueling volume is 50 liters or more, the temperature difference is approximately 1.2℃, following a uniform distribution.

[0196] u(t j ) = 1.2 / √3 = 0.6929℃

[0197] 8) Uncertainty component introduced by the volume expansion of the oil tank body

[0198] The uncertainty of the volumetric expansion coefficient of the gas station tanks is 3.3 × 10⁻⁶.-6 If it follows a uniform distribution, then

[0199] u(β g ) = 3.3 × 10 -6 / √3=1.9054×10 -6 ℃ -1

[0200] 9) Uncertainty components introduced by data model simplification

[0201] Based on the analysis of practical application data, the uncertainty component introduced by the simplification of the data model is approximately 1.5L, which follows a uniform distribution.

[0202] u(V m ) = 1.5 / √3 = 0.8661L

[0203] (1.3) Summary of Type B Standard Uncertainty

[0204] Table 3. Overview of Type B Uncertainty in the Capacity Comparison Method

[0205]

[0206]

[0207] (2) Evaluation of combined standard uncertainty

[0208]

[0209] (3) Expanded uncertainty

[0210] Taking a coverage factor of k = 2, the expanded uncertainty of the horizontal tank capacity verification result is:

[0211] U = 2 × 24.514 L = 49.028 L

[0212] For commonly used 30m 3 The interval capacity is 23599.577L, and the relative expanded uncertainty of the verification result is:

[0213] U rel =49.028 / 23599.577=0.208% (k=2).

[0214] In addition to the embodiments described above, the present invention may have other implementations. All technical solutions formed by equivalent substitution or equivalent transformation fall within the protection scope claimed by the present invention.

Claims

1. A method for online verification of oil tank capacity tables, characterized in that, Includes the following steps: Step 1: By extracting historical liquid level data from the gas station's liquid level gauge platform and sales data from the fuel dispensers, select the verification range that exceeds the set threshold, and establish the correspondence between the liquid level height in the gas station's liquid tank and the volume of oil dispensed from the fuel dispenser. Step 2: Based on the correspondence between the oil level height and the volume of oil dispensed by the refueling gun established in Step 1, and considering the error of the refueling gun reading and the influence of temperature, after compensating and correcting the volume of oil stored in the tank and the volume of oil sold, establish the correspondence between the tank height and the cumulative volume after compensation and correction. Step 3: Apply the measurement model to fit the system and generate a new capacity table with corresponding verification intervals in centimeters; the formula for the measurement model is shown below: In the formula, V 20 Vh represents the volume value at 20°C corresponding to a liquid level height of h in the horizontal oil tank, and V0 represents the original oil tank volume table value corresponding to a starting height of h0 under the horizontal oil tank volume verification. j β represents the actual volume of fuel dispensed by the fuel dispenser when the liquid level in the horizontal oil tank is between h0 and h. y This represents the coefficient of thermal volume expansion of oil stored in oil tanks, β. g t represents the coefficient of thermal volume expansion of the horizontal oil tank body, t0 represents the average temperature of the oil in the tank when the liquid level is h0, and t1 represents the average temperature of the oil in the tank when the liquid level is h. j E represents the weighted average temperature of the fuel dispensed by the fuel dispenser when the liquid level in the horizontal fuel tank is between h0 and h. j This indicates the fuel dispenser calibration error; Uncertainty assessment of the new capacity table includes: Type A assessment of measurement uncertainty, Type B assessment of measurement uncertainty, assessment of combined standard uncertainty, and assessment of expanded uncertainty; the formula for Type A assessment of measurement uncertainty is as follows: S(x) = R / C In the formula, S(x) refers to the Type A standard uncertainty, R refers to the maximum cumulative capacity difference within the tank range, and C refers to the range coefficient. The analysis of uncertainties affecting the verification results includes: the uncertainty component u(V0) caused by the uncertainty of the starting liquid level height at the low liquid level, and the uncertainty component u(β) caused by the oil expansion coefficient in the horizontal tank. y The uncertainty component u(t1) is introduced due to the uncertainty of the high liquid level starting temperature, the uncertainty component u(t0) is introduced due to the uncertainty of the low liquid level starting temperature, and the uncertainty component u(V) is introduced due to the uncertainty of the accumulated pump code of the fuel dispenser. j The uncertainty component u(E) introduced by the uncertainty of the fuel dispenser calibration (verification) results. j The fuel dispenser outputs an uncertain component u(t) caused by the measurement of fuel temperature. j The uncertainty component u(β) introduced by the volume expansion of the oil tank body g The uncertainty component u(V) introduced by the simplification of the data model m ); The formula for Type B evaluation of measurement uncertainty is as follows: In the formula, Let c1 be the combined variance of the Type B standard uncertainty, and c9 be the propagation coefficients corresponding to the uncertain components. Based on the Type A and Type B uncertainty assessments, the combined standard uncertainty is assessed. The formula for evaluating the combined standard uncertainty is as follows: In the formula, u is the combined standard uncertainty, and S(x) refers to the Type A standard uncertainty. The combined variance of Type B standard uncertainties; Calculate the expanded uncertainty based on the combined standard uncertainty assessment; The formula for expanded uncertainty is as follows: U = ku In the formula, U is the expanded uncertainty of the tank capacity verification result, u is the combined standard uncertainty, and k is the coverage factor; The relative expanded uncertainty U of the oil tank inspection results rel The formula is as follows: U rel =U / Tank area capacity.

2. The method for online verification of oil tank capacity tables according to claim 1, characterized in that, In step 2, the volume compensation correction for tank-stored oil refers to compensating for the temperature difference in the volume of tank-stored oil based on the temperature changes in the oil tank during the sales process.

3. The method for online verification of oil tank capacity tables according to claim 1, characterized in that, In step 2, compensating for the volume of oil sold refers to compensating for the temperature difference and sales error volume of the oil stored in the tank and the oil sold based on the temperature changes during the sales process and the overall error of the fuel dispenser.

4. The method for online verification of oil tank capacity tables according to claim 1, characterized in that, In step 2, when establishing the correspondence between the tank height and the cumulative volume, the tank level is used as the horizontal axis and the cumulative volume is used as the vertical axis to draw a curve showing the relationship between the height and the cumulative volume, generating a new capacity table with corresponding verification intervals in centimeters.

5. The method for online verification of oil tank capacity tables according to claim 1, characterized in that, Online verification of oil tank capacity tables must meet the following conditions: (1) The oil tank is not severely deformed and is installed on a stable base. It does not shift during the oil receiving and dispensing operations. (2) The slope of the oil tank unloading pipeline meets the design specifications and does not affect the normal return of the remaining oil in the pipeline to the tank after unloading; (3) The oil tank level gauge is firmly installed and there is no visible displacement during use. The equipment has a metering tolerance of ±0.5 mm for level and ±0.2 ℃ for average output temperature. (4) The standard metal measuring instrument used for fuel dispenser calibration shall be no less than 50 L and have an accuracy class of no less than Class II; the thermometer shall have a minimum scale division of 0.1 ℃ and a maximum tolerance of ±0.2 ℃. The vapor recovery device is in good working order; it should be connected during fuel dispenser calibration. (5) Correct the calibration error when using the fuel dispenser; the fuel dispenser calibration should use the maximum flow point data and be carried out in a quantitative manner. Temperature correction should be performed during calibration; for fuel dispensers that have not been refueled for a long time, the calibration data should be calculated from the second container. (6) If the liquid level difference in the corresponding interval is greater than 1.2 m, the verification result will only provide the tank capacity data within the verification interval; the capacity data within 50 mm of the upper and lower points of the verification height will not be used. (7) No refueling or oil return operations shall be carried out during the oil stabilization period; after the oil stabilization period ends, the oil receiving and acceptance operations shall be carried out in a timely manner; during the oil tank calibration data collection period, there shall be no operations that affect data analysis, such as refueling machine calibration or oil return. (8) The historical liquid level curve of the oil tank is complete in the liquid level gauge system; (9) Verify twice, and take the average of the cumulative capacity within the common interval.

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