Gas meter metering performance detection device and use method thereof

Abstract

The invention relates to the technical field of gas meter detection equipment, and particularly discloses a gas meter metering performance detection device and a use method thereof. The frequency conversion fan serves as a power source, air in the medium temperature adjusting area is sequentially sucked into the standard meter, the tested gas meter and the flow adjusting assembly, and finally gas is discharged to the medium temperature adjusting area to form airflow circulation. In the gas flow circulation process, through measuring the flow metering conditions of the standard meter and the tested gas meter and the pressure of the gas inlet and the temperature of the gas outlet of the standard meter and the tested gas meter, the detection of the metering performance of the gas meter influenced by the temperature is completed through calculation. The standard meter and the to-be-detected gas meter are placed in the same environment for detection, the metering performance of the to-be-detected gas meter is detected through an isothermal method, and the detection accuracy is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of gas meter detection equipment, and in particular to a gas meter measurement performance detection device and a use method thereof. Background Art

[0002] In the field of measurement, taking the diaphragm gas meter as an example, the diaphragm gas meter belongs to the volumetric gas flow meter, which uses a flexible diaphragm metering chamber to measure the gas volume flow. Under the action of pressure difference, the gas alternately enters the metering chamber through the distribution valve, and is discharged to the outlet after being filled, while pushing the flexible diaphragm in the metering chamber to make reciprocating motion. The conversion mechanism converts this cycle of filling and exhausting into the corresponding gas volume flow, and then transmits it to the counter through the transmission mechanism to complete the gas cumulative metering function. According to JJF 1354-2012 "Outline for Type Evaluation of Diaphragm Gas Meters", the accuracy level of diaphragm gas meters is 1.5, and the metering performance of the gas meter in an environment of (-10 ~ +40) ℃ should meet the maximum allowable error of no more than 3%.

[0003] At present, the variable temperature method is generally used to test the metering performance of gas meters, that is, the standard meter is placed under reference conditions, the temperature range is (20±2)℃, and the gas meter under test is placed in the working environment temperature (-10~+40)℃. During the test process, the working gas medium needs to be repeatedly "heated up" or "cooled down" to meet the requirements of the standard meter and the meter under test working at different temperatures. The entire test process is relatively complicated and has large errors. If water condenses during the temperature adjustment process, it will also affect the test results. Summary of the invention

[0004] The object of the present invention is to provide a gas meter measurement performance detection device and a method of using the same, so as to solve the problem of large error in gas meter performance detection using a variable temperature method.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is: a gas meter measurement performance detection device, including a medium temperature adjustment area, a working temperature adjustment area, a variable frequency fan and a flow adjustment structure; The medium temperature adjustment area is provided with a first temperature sensor; The working temperature adjustment area is provided with a standard meter, a first gas meter to be tested, a second gas meter to be tested and a third gas meter to be tested; the medium temperature adjustment area is connected to the standard meter through the seventh gas pipe; the standard meter is connected to the first gas meter to be tested through the first gas pipe, the first gas meter to be tested is connected to the second gas meter to be tested through the second gas pipe, and the second gas meter to be tested is connected to the third gas meter to be tested through the third gas pipe; the first gas pipe, the second gas pipe, the third gas pipe and the seventh gas pipe are all provided with a second temperature sensor and a pressure sensor; the first gas meter to be tested, the second gas meter to be tested and the third gas meter to be tested are all provided with an industrial camera; The flow regulating structure is connected to the working temperature regulating area through the fourth air pipe; The variable frequency fan is connected to the flow regulating structure through the fifth air pipe and is connected to the medium temperature regulating area through the sixth air pipe.

[0006] As a further technical solution of the above solution, it also includes a dehumidification structure, which is connected to the medium temperature adjustment area and is used to dry the air in the medium temperature adjustment area.

[0007] As a further technical solution of the above solution, it also includes two circulation fans, which are respectively arranged in the medium temperature adjustment area and the working temperature adjustment area.

[0008] The present invention also provides a method for using a gas meter measurement performance detection device, comprising the following steps: Step S1, starting the variable frequency fan to blow air into the medium temperature adjustment area, and using the first temperature sensor to monitor the temperature in the medium temperature adjustment area; Step S2, blowing the air in the medium temperature adjustment zone into the standard meter, the first gas meter to be tested, the second gas meter to be tested and the third gas meter to be tested in the working temperature adjustment zone in sequence; monitoring the temperature and pressure through the second temperature sensor and the pressure sensor; Step S3, the industrial camera records the accumulated flow of the first gas meter to be tested, the second gas meter to be tested, and the third gas meter to be tested, and compares them with the data of the standard meter, respectively, to evaluate the metering performance of the first gas meter to be tested, the second gas meter to be tested, and the third gas meter to be tested under the working condition; Step S4, the gas from the third gas meter to be tested continues to flow into the flow regulating structure, and enters the variable frequency fan after the flow is adjusted, forming an air flow cycle.

[0009] Step S5, adjusting the temperature of the medium temperature adjustment zone and the working temperature adjustment zone, and retesting the performance of the first gas meter to be tested, the second gas meter to be tested, and the third gas meter to be tested under different temperature conditions.

[0010] Compared with the prior art, the present invention has the following advantages and beneficial effects: by placing the standard meter and the gas meter to be tested in the same testing environment, the present invention realizes isothermal testing of the metering performance of the gas meter to be tested, thereby improving the accuracy of the test. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a schematic diagram of the device structure of the present invention.

[0012] Figure 2 This is the workflow diagram of an industrial camera.

[0013] Figure 3 is the K coefficient of Roots flowmeter at different temperatures (0.4m³ / h).

[0014] Figure 4 is the K factor of Roots flowmeter at different flow rates (20°C).

[0015] The meanings of the numbers in the figure are: medium temperature control zone-1; first temperature sensor-11; working temperature control zone-2; standard meter-21; first gas meter to be tested-22; second gas meter to be tested-23; third gas meter to be tested-24; second temperature sensor-25; pressure sensor-26; industrial camera-27; dehumidification structure-3; variable frequency fan-4; flow regulation structure-5; circulation fan-6. DETAILED DESCRIPTION

[0016] The technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention, so as to have a further understanding of the concept of the present invention, the technical problems solved, the technical features constituting the technical scheme and the technical effects brought about.

[0017] The new membrane gas indication value error has requirements: q min ≤ q < q t The maximum allowable error is +3%; when q t ≤ q < q max The maximum allowable error is +1.5%; q min It is the lower limit flow rate for the gas meter to meet the measurement performance requirements; q max The upper limit flow rate for the gas meter to meet the metering performance requirements; q t It is the boundary flow rate for the gas meter's measurement performance requirements. Between the upper limit flow rate and the lower limit flow rate, the gas meter flow range is divided into "high zone" and "low zone" flow rates. The gas meter has corresponding maximum allowable errors in the high zone and the low zone. q t =0.1 q max .

[0018] Since there is a certain pressure loss when the gas flows through the standard meter and the gas meter being tested, △p It means that when measuring the metering performance of the gas meter under test, according to the principles of thermodynamics, it is necessary to measure the pressure at the gas meter inlet and the temperature at the gas outlet to evaluate the metering performance of the gas meter.

[0019] The reference conditions for the gas meter performance test are as follows: the temperature range is (20±2)℃, and the humidity range is 45%RH~75%RH. The measurement performance calculation process is as follows: 9.2.1.5 Data Processing in JJF 1354-2012 "Outline for Type Evaluation of Diaphragm Gas Meters": 9.2.1.5 Data processing: The single measurement indication error is calculated according to formula (1): (1); Where: is the indication error of a single measurement, %; is the indication of the gas meter, dm 3 ; is the actual value of gas passing through the gas meter, dm 3 .

[0020] During the test, the temperature and pressure at the gas meter inlet and the standard device should be measured, and the temperature and pressure corrections should be made according to formula (2); (2); Where: is the indication of the standard device, dm 3 ; is the absolute pressure at the standard device, Pa; is the thermodynamic temperature at the standard device, K; is the absolute pressure at the inlet of the gas meter, Pa; is the thermodynamic temperature at the inlet of the gas meter, K; In Article 7.3 of JJF 1354-2012 "Outline for Type Evaluation of Diaphragm Gas Meters", it is stipulated that the metering performance of the gas meter in an environment of (-10 ~ +40) ℃ should meet the requirements of Table 1. Temperature adaptability testing can also be carried out based on the wider operating temperature range of the gas meter.

[0021] like Figure 1 and Figure 2As shown, a gas meter measurement performance detection device and its use method, the working process of the whole device is that the variable frequency fan is used as the power source, the air in the medium temperature control area is sucked into the standard meter, the gas meter to be tested and the flow regulating component in turn, and finally the gas is discharged to the medium temperature control area to form an air flow cycle. During the air flow cycle, the flow measurement conditions of the standard meter and the gas meter to be tested, as well as the pressure of the air inlet and the temperature of the air outlet of the standard meter and the gas meter to be tested are measured, and the detection of the gas meter's measurement performance affected by temperature is completed through calculation.

[0022] The functions of each part of the device are as follows: 1. The medium temperature adjustment area is used to adjust the temperature of the working airflow of the calibration device. The temperature adjustment range is -40℃~70℃.

[0023] 2. In order to ensure that the working airflow of the calibration device is free of moisture, the dehumidification device is used to dry the air in the medium temperature control area.

[0024] 3. The working temperature adjustment area is used to place the gas meter under test, industrial camera and standard meter, and the temperature adjustment range is -40~70. The industrial camera is used to collect the real-time metering data of the gas meter under test, and each gas meter under test corresponds to an industrial camera. In order to ensure the uniform temperature of the space, the medium temperature adjustment area and the working temperature adjustment area use circulating fans to force the uniformity of the temperature. Multiple gas meters under test can be placed in the working temperature adjustment area as needed, such as Figure 1 According to the working principle of the detection device, it is necessary to collect the pressure value of the air inlet and the temperature value of the air outlet of the standard meter and the gas meter to be tested.

[0025] 4. The flow regulating component is composed of multiple pipelines. Each pipeline has a built-in "flow limiting plate" and is independently controlled by a solenoid valve. During operation, the flow through the "flow limiting plate" in each pipeline is fixed and can be opened or closed in combination as needed.

[0026] 5. The variable frequency fan is the power source for the gas flow of the entire device. The device is started to avoid excessive starting current. Low frequency is used for starting. After starting, it runs according to the set frequency. The operating frequency can be adjusted according to the internal pressure of the device to meet the detection requirements.

[0027] 6. The process of data collection is to first open the pipeline valve of the flow regulating component according to the setting, start the variable frequency fan, form a suitable gas flow field, and collect the temperature of the medium temperature adjustment area and the working temperature adjustment area, the pressure value of the standard meter gas port and the temperature value of the gas outlet through the RS485 bus, as well as the pressure value of the gas inlet and the temperature value of the gas outlet of the gas meter under test. The industrial camera is connected to the USB to collect the cumulative flow display value on the gas meter display in real time, and the cumulative flow of the gas meter during the detection process is calculated. The above data is calculated to obtain the measurement accuracy of the gas meter under the working environment.

[0028] In the present invention, a Roots flowmeter is used as a standard meter. The Roots flowmeter is mainly composed of a housing, a Roots wheel, a bearing, a sensor and other components. The Roots wheel is usually composed of a pair or a group of synchronously rotating rotors, which rotate at high speed in the housing to form a sealed metering chamber. When the fluid passes through the Roots flowmeter, the pressure difference generated by the fluid between the inlet and the outlet acts on a pair of Roots wheels connected by high-precision synchronous gears, driving the Roots wheels to rotate. During the rotation process, the closed space formed between the Roots wheel and the inner wall of the housing and the gland - the metering chamber is periodically inflated and exhausted. The number of revolutions of the Roots wheel is proportional to the volume of gas passing through the flowmeter.

[0029] The rotation of the Roots wheel is transmitted to the mechanical counter (or output flow pulse signal) through the magnetic coupler, thereby accumulating the volume flowing through the metering chamber to achieve the purpose of metering.

[0030] Among them, the K factor of the Roots flowmeter is an important parameter that characterizes the metering characteristics of the flowmeter, and is also called the instrument factor or K factor. It indicates the number of signal pulses output by the sensor when a unit volume of fluid flows through the flowmeter sensor. For Roots flowmeters, the K factor is usually related to the structural parameters of the flowmeter, such as the speed of the rotor, the structural dimensions of the metering chamber, etc.

[0031] Specifically, the K factor of the Roots flowmeter can be obtained through experimental calibration, which is the proportional relationship between the number of pulses output by the flowmeter and the flow rate passing through the flowmeter. For example, in some Roots flowmeters, the K factor may be expressed as n pulses output per revolution, that is, K=n / flow rate per revolution. This means that when the flowmeter rotor rotates one revolution, n pulse signals will be output, so that the volume of fluid passing through the flowmeter can be calculated. (1) The K coefficient of Roots flowmeter is relatively stable and is not greatly affected by temperature. Taking 0.4m³ / h flow rate as an example, Table 1 shows the change of K coefficient of Roots flowmeter at different temperatures.

[0032] Table 1 K coefficient of Roots flowmeter at different temperatures (0.4m³ / h) .

[0033] Table 1 shows that within the range of -10℃~50℃, compared with the standard temperature of 20℃, the maximum change of the K coefficient of the Roots flowmeter is 28, and the change rate is 2‰, which can be ignored for the error of the measurement system.

[0034] Figure 3 The curve generated for Table 1 shows that from the figure, the K coefficient of the Roots flowmeter changes linearly with temperature from -10℃ to 20℃. The linear function is used to further correct the measurement system to ensure the accuracy of the measurement.

[0035] (2) The starting flow and pressure loss of the Roots flowmeter are small, the range ratio is wide, the measurement accuracy is not easily affected by changes in pressure and flow, and the accuracy is good. Taking 20℃ as an example, Table 2 shows the change of the K coefficient of the Roots flowmeter at different flow rates.

[0036] Table 2 K coefficient changes of Roots flowmeter at different flow rates .

[0037] Table 2 shows that the K coefficient of the Roots flowmeter has a more obvious flow cutoff point. When the flow rate is greater than the cutoff point, the K coefficient tends to be constant within the flow range. Figure 4 The curve generated for Table 2. In order to ensure the accuracy of the standard table measurement, the curve correction method is adopted to further correct the measurement system to ensure the accuracy of the measurement.

[0038] (3) There is no requirement for special straight pipe sections before and after the flow meter, so it can be installed in narrow places.

[0039] There are many methods for flow measurement. Many flow meters have clear straight pipe section requirements before and after. In order to meet the straight pipe section requirements, the measurement system will be relatively large. One of the characteristics of the present invention is low energy consumption. Since there is no straight pipe section requirement, the controllable temperature zone can be made compact enough to reduce the space of the temperature control area, thereby achieving the purpose of reducing energy consumption.

[0040] After the present invention adopts the Roots flowmeter as the standard meter, its metering performance can be corrected by temperature. After the correction, the Roots flowmeter can be directly placed in the same space as the gas meter to be tested, that is, the measurement and evaluation can be carried out at the same temperature, thereby realizing the isothermal method for testing the metering performance of the gas meter and improving the accuracy of the detection.

[0041] When reading the cumulative flow of the gas meter to be tested, the industrial camera collects the "minimum metering position" on the gas meter display in real time. The display range of the "minimum metering position" is 0~9. Each movement of one digit represents the volume of gas flowing through the gas meter to be tested is 0.001m³. During the operation of the gas meter, the number of the "minimum metering position" will flip and measure in the range of 0~9. Using the image processing algorithm, the industrial camera is used to collect the "minimum metering position" image, and a certain number of the "minimum metering position" is used as the starting feature value. When the image of the "minimum metering position" collected by the camera is consistent with the starting feature value, the "minimum metering position" rotates one circle, and the cumulative flow of the gas meter is 10×0.001 m³. The entire test process only needs to count the rotations of the "minimum metering position" to obtain the cumulative flow. For example, during the detection process, 0.27m³ of gas needs to be collected for detection. The "starting cumulative flow" is 193.146m³, the "ending cumulative flow" is 193.416 m³, and the actual flow is 193.416-193.146=0.27m³. The method for the data acquisition system to collect flow is to first use an industrial camera to collect the "minimum metering position" of the "starting cumulative flow". The result is "6". The image algorithm is used to mark it for characterization, and the standard meter starts measuring at the same time. During the detection process, the industrial camera continuously collects the "minimum metering position" and compares it with the characteristic value. When the comparison results are consistent, the counter +1. When the counter is 27, stop counting, and read the metering results of the standard meter as well as the related temperature and pressure at the same time, and calculate the accuracy of the gas meter being tested. The detection flow chart is as follows Figure 2 shown.

[0042] The terms “connection” and “fixation” mentioned in the description of the present invention may refer to fixed connection, processing and forming, welding or mechanical connection. The specific meanings of the above terms in the present invention shall be understood according to the specific circumstances.

[0043] In the description of the present invention, the terms "center", "upper", "lower", "horizontal", "inside", "outside", etc., which indicate the orientation or position relationship, are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying a specific orientation that the device or element referred to must have, and therefore cannot be understood as a limitation on the present invention.

[0044] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments can still be modified, or some or all of the technical features therein can be replaced by equivalents. However, these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A gas meter measurement performance detection device, characterized in that: It includes a medium temperature adjustment area (1), a working temperature adjustment area (2), a variable frequency fan (4) and a flow adjustment structure (5); The medium temperature adjustment area (1) is provided with a first temperature sensor (11); The working temperature adjustment area (2) is provided with a standard meter (21), a first gas meter to be tested (22), a second gas meter to be tested (23) and a third gas meter to be tested (24); the medium temperature adjustment area (1) is connected to the standard meter (21) via a seventh gas pipe; the standard meter (21) is connected to the first gas meter to be tested (22) via a first gas pipe, the first gas meter to be tested (22) is connected to the second gas meter to be tested (23) via a second gas pipe, and the second gas meter to be tested (23) is connected to the third gas meter to be tested (24) via a third gas pipe; The first gas pipe, the second gas pipe, the third gas pipe, and the seventh gas pipe are each provided with a second temperature sensor (25) and a pressure sensor (26); the first gas meter to be tested (22), the second gas meter to be tested (23), and the third gas meter to be tested (24) are each provided with an industrial camera (27); A flow regulating structure (5) connected to the working temperature regulating zone (2) via a fourth air pipe; The variable frequency fan (4) is connected to the flow regulating structure (5) via a fifth air pipe, and is connected to the medium temperature regulating area (1) via a sixth air pipe.

2. A gas meter measurement performance detection device as claimed in claim 1, characterized in that: It also includes a dehumidification structure (3), which is connected to the medium temperature adjustment area (1) and is used to dry the air in the medium temperature adjustment area (1).

3. A gas meter measurement performance detection device as claimed in claim 1, characterized in that: It also includes two circulation fans (6), which are respectively arranged in the medium temperature adjustment area (1) and the working temperature adjustment area (2).

4. A method for using the gas meter measurement performance detection device according to claim 1, characterized in that: The following steps are involved: Step S1, starting the variable frequency fan (4) to blow air into the space of the medium temperature adjustment zone (1), and using the first temperature sensor (11) to monitor the temperature in the medium temperature adjustment zone (1); Step S2, blowing the air in the medium temperature adjustment zone (1) into the standard meter (21), the first gas meter to be tested (22), the second gas meter to be tested (23) and the third gas meter to be tested (24) in sequence in the working temperature adjustment zone (2); monitoring the temperature and pressure by means of the second temperature sensor (25) and the pressure sensor (26); Step S3, the industrial camera (27) records the accumulated flow rates of the first gas meter to be tested (22), the second gas meter to be tested (23), and the third gas meter to be tested (24), and compares them with the data of the standard meter (21), respectively, to evaluate the metering performance of the first gas meter to be tested (22), the second gas meter to be tested (23), and the third gas meter to be tested (24) under the working condition; Step S4, the gas from the third gas meter to be tested (24) continues to flow into the flow regulating structure (5), and after the flow is adjusted, enters the variable frequency fan (4), forming an air flow cycle; Step S5, adjusting the temperature of the medium temperature adjustment area (1) and the working temperature adjustment area (2), and retesting the performance of the first gas meter to be tested (22), the second gas meter to be tested (23), and the third gas meter to be tested (24) under different temperature conditions.

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