Gas meter real flow detection system and detection method

Abstract

The present invention relates to a gas meter real flow detection system and detection method, wherein the gas source is connected to a low-pressure gas storage tank through a buffer valve group, and the low-pressure gas storage tank is connected to an explosion-proof vacuum pump, a reversing valve group, a piston pressure balancer and a double-chamber piston flow generator working group through a pipeline, and a plurality of gas control valves for controlling on and off are arranged on the pipeline, and the reversing valve group is connected to a workbench of the meter to be inspected. By adding an explosion-proof vacuum pump and a low-pressure gas storage tank, the present invention can complete the entire gas replacement process under the condition of using only 1 times the volume of gas in the entire system; by adding a pressure balancing piston and using a method of dynamically adjusting the volume of the detection loop, the pressure in the detection process is stabilized; by using two groups of double-chamber piston flow generators of different sizes, the detection range is expanded while ensuring the accuracy of the detection results; by adding an infrared optical communication interface, the device can quickly read the instantaneous flow output of the meter to be inspected, reducing the waiting time for the accumulated volume and improving the detection efficiency.

Description

Technical Field

[0001] The present invention relates to the field of measurement technology, and in particular to a gas meter real flow detection system and a detection method. Background Art

[0002] With the development of electronic technology, new electronic gas meters represented by ultrasonic gas meters and thermal mass gas meters have begun to emerge slowly and gradually move towards the household gas meter market. Compared with traditional membrane gas meters, this type of electronic gas meter is also called velocity gas meter. They can directly calculate the gas flow rate and have the advantages of simple structure, no mechanical transmission parts, and no mechanical wear. At the same time, the key parameters involved in the principle of ultrasonic gas meters (sound velocity) and the key parameters involved in the principle of thermal gas meters (specific heat capacity) are related to the composition of the gas. In the study of electronic gas meters, exploring the influence of gas components on their measurement is an unavoidable problem. Therefore, there is an urgent need for a system and method for real flow detection.

[0003] However, if you want to conduct real gas flow detection, you have to face two key technical problems: safety and accuracy. The so-called safety refers to how to ensure that the detection process is safe when using combustible gas; the so-called accuracy refers to how to ensure the accuracy of the detection results.

[0004] First, the consideration of safety. Since the detection process involves combustible gases, and the three elements of general combustion include combustibles, combustion aids, and temperature reaching the combustion point, none of which can be missing. Therefore, in theory, as long as the content of the combustion aid is low enough, combustion or explosion will not occur. The currently disclosed technical solutions also adopt this strategy, namely: before the test, the air in the detection system is replaced with an inert gas to make the oxygen content in the detection system much lower than the limiting oxygen concentration of the detection gas; then the detection gas is used to replace the inert gas in the detection system, thereby ensuring the safety of the detection process.

[0005] Taking the technical document with patent number CN106338322A as an example, this solution uses nitrogen as an inert gas and natural gas as a detection gas. The specific gas replacement process is as follows: first fill the gas tank with nitrogen to reduce the oxygen content, and then use the double-chamber piston to move to exhaust. After repeating the inflation and exhaust several times, the replacement of air with nitrogen is completed. In the above process, the amount of nitrogen used is two to five times the volume of the entire system. Similarly, to replace nitrogen with natural gas, first fill the gas tank with natural gas to reduce the nitrogen content, and then use the double-chamber piston to move to exhaust. After repeating the inflation and exhaust several times, the replacement of nitrogen with natural gas is completed. In the above process, the amount of natural gas used is also two to five times the volume of the entire system.

[0006] Although the above technical solution can realize gas replacement and thus ensure the safety of the detection process, the disadvantage is also obvious, that is, the gas consumption in the entire replacement process is very huge. According to the description in the embodiment of the text, a gas replacement requires 3 times the volume of nitrogen and 3 times the volume of natural gas in the entire system.

[0007] At the same time, this technical solution has a hidden flaw, which is that it does not take into account the issue of replacement of the gas meter under inspection during batch testing. The replacement process of the gas meter under inspection involves the disassembly and installation of the meter under inspection, which can easily cause the gas in the pipeline to leak out. At the same time, oxygen will be introduced into the pipeline after the meter is replaced. In order to avoid potential safety hazards, gas replacement should be performed before and after the meter is replaced. However, according to the above technical solution, since both the double-chamber piston and the gas storage tank need to participate in the gas replacement process, each time the meter is replaced, the entire system needs to replace nitrogen and natural gas, and cannot be reused. For batch testing, the replacement of the meter under inspection is very frequent. This not only increases the inspection cost of the meter under inspection, but also generates a large amount of waste gas that is difficult to handle, which is prone to safety hazards.

[0008] The second point is about accuracy. Since the double-chamber piston is not only a part of the gas circuit, but also a device for generating standard flow, if the pressure is unstable during the test, the flow will be unstable during the test, which will bring errors to the test results and ultimately affect the accuracy of the test results. Therefore, the pressure must be stable during the test.

[0009] Taking the technical document with patent number CN106338322A as an example, this technical solution achieves zero pressure difference between the left and right chambers of the piston by replenishing air from the gas tank to the piston. The specific process of replenishing air is as follows: When working in the forward direction, the stepper motor drives the double-chamber piston to move right, and the natural gas in the right chamber flows back to the left chamber through the reversing valve group and the meter under test. At the same time, during the detection process, the gas tank replenishes air to the left chamber through the one-way valve. When working in the reverse direction, the stepper motor drives the double-chamber piston to move left, and the natural gas in the left chamber flows back to the right chamber through the reversing valve group and the meter under test. At the same time, during the detection process, the gas tank replenishes air to the right chamber through the one-way valve.

[0010] The above technical solution is to balance the pressure by replenishing air, which essentially adds an extra thrust to the piston to compensate for the pressure loss during the operation of the piston. However, since the detection process is carried out in a closed circulation pipeline, each replenishment of air in the detection will cause the final overall pressure of the pipeline to rise, and thus the repeatability of the detection environment cannot be guaranteed. More importantly, after this method has been running for a period of time, the previous replenishment of air will increase the overall pressure of the pipeline, making it difficult for the piston to change the flow direction of the fluid during the reversing process, causing the piston to start more slowly and even generating a certain amount of pulsating flow. Therefore, this method of balancing the pressure by replenishing air from the air tank to the piston is prone to cause unstable flow during the startup phase.

[0011] At the same time, in the above technical solution, there is only a reversing valve and a pipeline connection between the piston flow generator and the meter under test, without any air flow buffer structure. This causes the flow disturbance caused by the piston standard during the start, reversal, stop and other operations to directly act on the meter under test, making the flow through the meter under test unstable during the test process, which ultimately brings errors to the test results and affects the accuracy of the test results.

[0012] The third point is about the consideration of the detection range. According to the principle of the piston flow generator, its standard flow is obtained by calculating the volume of gas discharged by the piston device during the measurement time:

[0013]

[0014] Where q is the standard flow rate, S is the cross-sectional area of ​​the piston cavity, L is the movement distance of the piston, and t is the test time. If the same set of pistons is used in the full flow test range, since the cross-sectional area of ​​the piston cavity is immutable, when the standard flow rate q is very small (such as: below 10 L / h), the change in the piston movement distance L will be very small, resulting in a significant increase in the measurement uncertainty of the piston movement distance L, which reduces the accuracy of the small flow test results, and even makes it impossible to test small flows.

[0015] The fourth point is about the consideration of detection efficiency. Ultrasonic gas meters and thermal mass gas meters are velocity gas meters that can output instantaneous flow. However, most detection devices currently obtain the flow of the meter under test by calculating the cumulative volume during the test time, that is:

[0016]

[0017] Where q' is the flow rate of the meter under test, N is the cumulative number of pulses, P is the pulse equivalent, that is, the volume corresponding to a unit pulse, and t is the test time. To avoid errors caused by pulse sampling, the number of pulses must be kept at a certain amount. Taking a flow rate of 16 L / h as an example, assuming that the pulse equivalent is 10 L / plus, it takes at least 2250 seconds to detect one pulse, which makes the detection time of small flow points very long and reduces the detection efficiency. Summary of the invention

[0018] In view of the problems existing in the prior art, the object of the present invention is to provide a technical solution for a gas meter real flow detection system and a detection method.

[0019] The gas meter real flow detection system is characterized by including a gas source, a buffer valve group, a low-pressure gas storage tank, an explosion-proof vacuum pump, an air control valve, a reversing valve group, a workbench for the meter to be inspected, a piston pressure balancer, a double-chamber piston flow generator working group and pipelines connecting the various components. The gas source is connected to the low-pressure gas storage tank through the buffer valve group, and the low-pressure gas storage tank is connected to the explosion-proof vacuum pump, the reversing valve group, the piston pressure balancer and the double-chamber piston flow generator working group through a pipeline. A plurality of air control valves for controlling on and off are arranged on the pipeline, and the reversing valve group is connected to the workbench for the meter to be inspected, and a plurality of groups of meters to be inspected are arranged on the workbench for the meter to be inspected.

[0020] The gas meter real flow detection system is characterized in that the gas source includes a working gas source and a protective gas source, the working gas source is natural gas, the protective gas source is nitrogen, the working gas source and the protective gas source are arranged in an explosion-proof gas cabinet, and the working gas source and the protective gas source are respectively connected to the low-pressure gas storage tank through corresponding buffer valve groups.

[0021] The gas meter real flow detection system is characterized in that the reversing valve group is used to switch the air intake direction, and the reversing valve group includes four air control valves, two of which are used for the left air intake meter being tested, and the other two are used for the right air intake meter being tested.

[0022] The gas meter real flow detection system is characterized in that the workbench of the meter under test is used to collect the flow, temperature and pressure of the meter under test during the test process. The left and right air inlet pipes of the workbench are equipped with temperature transmitters and pressure transmitters for collecting the temperature parameters and pressure parameters of the meter under test. The inlet and outlet ports of each workstation of the workbench are provided with differential pressure transmitters and infrared optical communication interfaces. The infrared optical communication interface communicates with the gas meter under test once every second, and can quickly obtain the instantaneous flow of the meter under test.

[0023] The gas meter real flow detection system is characterized in that the piston pressure balancer is composed of a piston, a screw, a piston cavity and a motor. The piston pressure balancer is connected to the air control valve, and the other end of the air control valve is connected to the overall system pipeline. By controlling the rotation of the servo motor, the screw is driven to drive the piston forward or backward, thereby adjusting the volume cavity size of the piston cavity and the connection part of the overall system pipeline to balance the pressure during operation of the double-cavity piston flow generator.

[0024] The gas meter real flow detection system is characterized in that the dual-chamber piston flow generator working group is used to generate a standard flow. The dual-chamber piston flow generator working group includes a 100L dual-chamber piston flow generator and a 20L dual-chamber piston flow generator. Each dual-chamber piston flow generator is composed of a piston, a screw, a piston cavity, a temperature transmitter, a pressure transmitter and a servo motor. The piston cavity is divided into a left cavity and a right cavity by the piston. The left cavity is a recovery cavity and the right cavity is a working cavity. The temperature transmitter and the pressure transmitter are installed on the recovery cavity to collect temperature parameters and pressure parameters during the detection process of the dual-chamber piston flow generator; the inlet and outlet of each set of dual-chamber piston flow generators are provided with air control valves. During the detection process, one of the dual-chamber piston flow generators is selected to connect to the test circuit according to the detected flow rate.

[0025] The method for detecting the actual flow of a gas meter is characterized in that it includes a gas replacement process, a detection process and a meter replacement process. The gas replacement process fills the test pipeline with experimental gas, and then executes the detection process. During the detection process, the 100L double-chamber piston flow generator and the 20L double-chamber piston flow generator are switched according to the detection flow. At the same time, the piston pressure balancer works to balance the pressure during the detection. The infrared optical communication interface communicates with the meter under test to quickly obtain the instantaneous flow of the meter under test. Then, a selection is made based on whether the meter needs to be replaced. If the meter does not need to be replaced, the detection ends. If the meter needs to be replaced, the meter replacement process is entered. The meter replacement process prevents the escape of natural gas when the meter is unloaded by purging. Gas replacement is performed after the meter is replaced. After the meter replacement process ends, the above process is repeated.

[0026] The gas meter real flow detection method is characterized in that the gas replacement process includes nitrogen replacing air and natural gas replacing nitrogen.

[0027] The method for detecting the actual flow of a gas meter is characterized in that the detection process is divided into two parts: the operation and reset of a 100L double-chamber piston flow generator and the operation and reset of a 20L double-chamber piston flow generator. The operation and reset of the 100L double-chamber piston flow generator are used to detect a large flow rate above 10L / h, and the operation and reset of the 20L double-chamber piston flow generator are used to detect a small flow rate below 10L / h. During the detection process, an infrared optical communication interface is used to communicate with the meter being tested, so that the instantaneous flow of the meter being tested can be quickly read.

[0028] The method for detecting the actual flow of a gas meter is characterized in that the meter replacement process includes replacing natural gas with nitrogen before unloading the meter and replacing air with nitrogen and nitrogen with natural gas after replacing the meter.

[0029] Advantages of the present invention:

[0030] 1) To overcome the shortcomings of current technology, an explosion-proof vacuum pump and a low-pressure gas storage tank are added, so that the entire gas replacement process can be completed using only 1 times the volume of gas in the entire system; at the same time, the pipelines and valves are adjusted so that the gas in the piston cavity and the gas storage tank can be retained during batch inspection and meter replacement, reducing the generation of waste gas, ensuring safety while reducing inspection costs;

[0031] 2) In order to overcome the shortcomings of the current technology, the pressure during the test is stabilized by adding a pressure balancing piston and dynamically adjusting the volume of the test circuit. At the same time, a gas storage tank is added in front of the meter being tested to stabilize the flow through the meter being tested during the test, making the test results more accurate.

[0032] 3) In order to overcome the shortcomings of the current technology, two sets of double-chamber piston flow generators of different sizes are used, so that large flow detection uses a large double-chamber piston flow generator, and small flow detection uses a small double-chamber piston flow generator, which expands the detection range while ensuring the accuracy of the test results;

[0033] 4) To overcome the shortcomings of current technology, an infrared optical communication interface is added so that the device can quickly read the instantaneous flow output of the meter being tested, reducing the waiting time for cumulative volume and improving detection efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0035] Figure 2 This is a schematic diagram of the first vacuuming during gas replacement in the present invention;

[0036] Figure 3 It is a schematic diagram of nitrogen filling during gas replacement of the present invention;

[0037] Figure 4 This is a schematic diagram of the second vacuuming during gas replacement in the present invention;

[0038] Figure 5 This is a schematic diagram of the natural gas filling during gas replacement in the present invention;

[0039] Figure 6 This is a working schematic diagram of the 100L double-chamber piston flow generator during the detection process of the present invention;

[0040] Figure 7 This is a schematic diagram of resetting the 100L double-chamber piston flow generator during the detection process of the present invention;

[0041] Figure 8 This is a working schematic diagram of a 20L double-chamber piston flow generator during the detection process of the present invention;

[0042] Fig. 9This is a schematic diagram of resetting the 20L double-chamber piston flow generator during the detection process of the present invention;

[0043] Fig.10 This is a schematic diagram of replacing natural gas before unloading the meter in the meter replacement process of the present invention;

[0044] Fig.11 It is a schematic diagram of vacuuming in the meter replacement process of the present invention;

[0045] Fig.12 This is a schematic diagram of nitrogen filling in the meter changing process of the present invention;

[0046] Fig.13 It is a detection flow chart of the present invention;

[0047] In the figure: gas source 1, nitrogen gas source 2, natural gas source 3, pressure regulating valve 4, stop valve 5, heat exchanger 6, buffer valve group 7, pressure regulating valve 8, stop valve 9, heat exchanger 10, buffer valve group 11, low-pressure natural gas tank 12, low-pressure nitrogen tank 13, explosion-proof vacuum pump 14, reversing valve group 15, left air inlet pipe of the inspected table workbench 16, right air inlet pipe of the inspected table workbench 17, inspected table workbench 18, piston pressure balancer piston 19, piston pressure balancer screw 20, piston pressure balancer piston cavity 21, piston pressure balancer servo motor 22, piston pressure balancer 23, double-chamber piston flow generator working group 24, 20L double-chamber piston flow generator left cavity 25, 20L double-chamber piston flow generator piston 26, 20L double-chamber piston flow generator right cavity 27, 20L double-chamber piston flow generator Screw 28, 20L double-chamber piston flow generator servo motor 29, 100L double-chamber piston flow generator left chamber 30, 100L double-chamber piston flow generator piston 31, 100L double-chamber piston flow generator right chamber 32, 100L double-chamber piston flow generator screw 33, 100L double-chamber piston flow generator servo motor 34, air control valve F1, air control valve F2, air control valve F3, air control valve F 4. Air-controlled valve F5, air-controlled valve F6, air-controlled valve F7, air-controlled valve F8, air-controlled valve F9, air-controlled valve F10, air-controlled valve F11, air-controlled valve F12, air-controlled valve F13, air-controlled valve F14, air-controlled valve F15, air-controlled valve F16, air-controlled valve F17, three-way T0, three-way T1, three-way T2, three-way T3, three-way T4, three-way T5, three-way T6, three-way T7, four-way T8, four-way T9. DETAILED DESCRIPTION

[0048] The present invention will be further described below in conjunction with the accompanying drawings:

[0049] The gas source 1 of the present invention includes a nitrogen gas source 2 and a natural gas gas source 3, which is used to provide working gas and protective gas for the system; the working gas can be selected according to actual needs. The present invention uses natural gas as the working gas, that is, the working gas source is a natural gas source, and the protective gas generally selects nitrogen or helium. The present invention uses nitrogen as the protective gas, that is, the protective gas source is a nitrogen gas source, that is, the nitrogen gas source 2 is used as the protective gas, and the natural gas source 3 is used as the working gas, and both are placed in an explosion-proof gas cabinet. The natural gas source 3 is connected to the pressure regulating valve 4 of the buffer valve group 7, and the nitrogen gas source 2 is connected to the pressure regulating valve 8 of the buffer valve group 11.

[0050] The present invention is provided with two sets of independent buffer valve groups to buffer and reduce the pressure of the gas output by the gas source, and restore the gas temperature to room temperature, so as to ensure that the gas entering the gas storage tank is a gas at normal temperature and pressure. Since the gas in the gas source is a high-pressure gas, and the gas storage tank at the rear end is a low-pressure container, a buffer valve group is required between the two for buffering. The air inlet of one set of buffer valve groups is connected to the natural gas source, and the air outlet is connected to the low-pressure natural gas tank; the air inlet of the other set of buffer valve groups is connected to the nitrogen source, and the air outlet is connected to the low-pressure nitrogen tank. Each set of buffer valve groups is composed of a pressure regulating valve, a heat exchanger and a stop valve connected in series in sequence. The pressure regulating valve is used to reduce the pressure of the high-pressure gas source output by the gas source to normal pressure, and then the heat exchanger restores the reduced pressure gas from low temperature to room temperature, and finally the stop valve is used to control whether the gas is input into the corresponding gas storage tank. Specifically, the buffer valve group 7 is composed of a pressure regulating valve 4, a heat exchanger 6, and a stop valve 5 connected in series in sequence, and is connected to a low-pressure natural gas tank 12; the buffer valve group 11 is composed of a pressure regulating valve 8, a heat exchanger 10, and a stop valve 9 connected in series in sequence, and is connected to a low-pressure nitrogen tank 13.

[0051] The gas storage tank of the present invention includes two types: a low-pressure natural gas tank and a low-pressure nitrogen tank. Since the technical solution needs to be vacuumed during the gas replacement process, the gas storage tank, as a link in the gas circuit, needs to work in a low-pressure environment, so a low-pressure gas storage tank is used. The low-pressure natural gas tank has two air inlets and one air outlet, one of which is connected to the buffer valve group, and the other air inlet and air outlet are connected to the corresponding gas control valve respectively. In addition to the function of storing gas, the natural gas storage tank also acts as a buffer as part of the sealed circulation loop in the detection. If there is no low-pressure natural gas tank as a buffer, the gas discharged by the operation of the double-chamber piston gas flow generator will directly act on the air inlet of the meter to be tested, resulting in large pressure fluctuations during the detection process of the meter to be tested, and ultimately making the flow rate very unstable during the detection process. Therefore, the volume of the low-pressure natural gas tank is increased to 3 times the volume of the large piston cavity in the double-chamber piston gas flow generator working group, which effectively buffers the gas discharged by the operation of the double-chamber piston gas flow generator, thereby achieving a stable flow rate flowing through the meter to be tested during the detection process. The low-pressure nitrogen tank is used to store nitrogen. The low-pressure nitrogen tank has an air inlet and an air outlet, wherein the air inlet is connected to the buffer valve group, and the air outlet is connected to the control valve. Specifically, the low-pressure natural gas tank 12 has 3 interfaces. In addition to being connected to the buffer valve group 7, the other two interfaces are connected to the gas control valve F1 and the gas control valve F2 respectively, wherein the other end of the gas control valve F1 is connected to the outlet of the three-way T6, and the other end of the gas control valve F2 is connected to the air inlet of the three-way T0. The low-pressure natural gas tank 12 plays the role of storing natural gas. At the same time, during the detection process, the low-pressure natural gas tank 12 buffers the flow disturbance generated by the double-chamber piston flow generator working group during startup, operation, reversal, and stop, so that the flow rate flowing through the inspected meter during the detection process is stable. The low-pressure nitrogen tank 13 plays the role of storing nitrogen. The low-pressure nitrogen tank 13 has 2 interfaces, one interface is connected to the buffer valve group 11, and the other interface is connected to the gas control valve F3, wherein the other end of the gas control valve F3 is connected to the three-way T1 air inlet.

[0052] The explosion-proof vacuum pump of the present invention cooperates with the gas circuit and valve to realize efficient vacuum gas replacement. The so-called vacuum gas replacement has the following specific process: first open all valves to evacuate, so that the gas pressure in the whole system is reduced to an absolute pressure of 2kPa; then fill the whole system with nitrogen to restore the gas pressure to an absolute pressure of 100kPa; then, evacuate again to an absolute pressure of 2kPa; finally, fill the whole system with natural gas to restore the gas pressure to 100kPa. In this way, the oxygen concentration in the system is reduced from 21% before replacement to 0.0084% after replacement, which is much lower than the limiting oxygen concentration (LOC) of 12% in methane, and the amount of nitrogen and natural gas used is only 1 times the volume of the whole system volume. At the same time, taking into account the meter replacement requirements during batch testing, the meter workbench to be inspected is separated from the low-pressure natural gas storage tank and the double-chamber piston flow generator working group by controlling the gas control valve, so that only the meter workbench to be inspected and the connecting pipeline are replaced with gas during the meter replacement process, retaining the natural gas in the low-pressure natural gas storage tank and the double-chamber piston flow generator working group, and reducing the amount of nitrogen and natural gas. Specifically, the explosion-proof vacuum pump 14 has two interfaces, one interface is connected to the atmosphere, and the other interface is connected to the gas control valve F4, wherein the other end of the gas control valve F4 is connected to the outlet of the tee T1, and the last air inlet of the tee T1 is connected to the outlet of the tee T0. The explosion-proof vacuum pump 14 is used for vacuuming when the pipeline is replaced with gas, ensuring the efficiency of the replaced gas. At the same time, in the process of changing the meter, in conjunction with the gas control valve, the natural gas in the low-pressure natural gas storage tank and the double-chamber piston flow generator working group is retained, and the meter replacement process of the inspected meter is completed, saving gas consumption.

[0053] The reversing valve group of the present invention is used to switch the air intake direction. The reversing valve group includes four air control valves, two of which are used for the left air intake test meter, and the other two are used for the right air intake test meter, so as to meet the test meters with different air intake directions. Specifically, the reversing valve group 15 is formed by connecting the air control valve F5, the air control valve F6, the air control valve F7, the air control valve F8 with the three-way T2, the three-way T3, the three-way T4, and the three-way T5, wherein the two air outlets of the three-way T2 are connected to the air control valve 5 and the air control valve 7, and the air inlet of the three-way T2 is connected to the air outlet of the three-way T0; the two air inlets of the three-way T3 are connected to the air control valve F3 and the air control valve F6 respectively, and the air outlet of the three-way T3 is connected to the The left air inlet pipe 16 of the inspected meter workbench is connected; the air outlet of the tee T4 is connected to the air control valve F7 and the air control valve F8, and the air inlet of the tee T4 is connected to the right air inlet pipe 17 of the inspected meter workbench; the air inlet of the tee T5 is connected to the air control valves F6 and F8, the air outlet of the tee T5 is connected to the air inlet of the tee T7, and the air outlet of the tee T7 is connected to the air control valve F10, wherein the other end of the air control valve F10 is connected to the atmosphere.

[0054] The inspected meter workbench of the present invention is used to install the inspected meter and collect parameters such as flow rate, temperature and pressure of the inspected meter during the test. The left air inlet pipe and the right air inlet pipe of the inspected meter workbench are equipped with temperature transmitters and pressure transmitters for collecting temperature parameters and pressure parameters of the inspected meter. There are 3 workstations inside the inspected meter workbench, and the air inlet and outlet of each workstation are equipped with a differential pressure transmitter and an infrared optical communication interface. The infrared optical communication interface communicates with the inspected gas meter once every second, and the instantaneous flow rate of the inspected meter can be quickly obtained, saving the time of waiting for the accumulated number of pulses and improving the detection efficiency. Specifically, the inspected meter workbench 18 is used to install the inspected meter and collect parameters such as flow, temperature and pressure of the inspected meter during the inspection process; the inspected meters are installed in sequence, wherein the air inlet of the first inspected meter (taking the left air inlet inspected meter as an example) is connected to the left air inlet pipe 16 of the inspected meter workbench, and the air outlet of the last inspected meter (taking the left air inlet inspected meter as an example) is connected to the right air inlet pipe 17 of the inspected meter workbench; the left air inlet pipe 16 of the inspected meter workbench and the right air inlet pipe 17 of the inspected meter workbench are both equipped with temperature transmitters and pressure transmitters for collecting the temperature and pressure of the gas flowing through the inspected meter during the inspection process, and each inspected meter workstation is equipped with a differential pressure sensor for measuring the pressure loss of the inspected meter during the inspection process; at the same time, each inspected meter workstation is also equipped with an infrared optical communication interface, which can read the instantaneous flow of the inspected meter during the inspection process to achieve rapid inspection.

[0055] The piston pressure balancer of the present invention is used to reduce the pressure fluctuations in the operation of the double-chamber piston flow generator during the test process. The piston pressure balancer is composed of a piston, a lead screw, a piston cavity and a motor. The piston pressure balancer is connected to the air control valve, and the other end of the air control valve is connected to the overall system pipeline. During the detection process, according to the pressure changes in the operation of the double-chamber piston flow generator, the servo motor is controlled to rotate, thereby driving the lead screw to drive the piston forward or backward, and then adjusting the volume cavity size of the piston cavity and the connection part of the overall system pipeline, and finally achieving the pressure balance in the operation of the overall system double-chamber piston flow generator. Compared with the prior art solution, there is no need to additionally replenish air to the overall double-chamber piston flow generator. At the same time, the solution can be adjusted in real time according to the pressure fluctuations in the operation of the double-chamber piston flow generator, that is, the pressure balance can be quickly achieved from the start-up stage, so that the pressure is stable during the entire detection process. Specifically, the piston pressure balancer and the piston cavity 21 of the piston pressure balancer 23 are connected to the air control valve F9, and the other end of the air control valve F9 is connected to the air outlet of the three-way T6; during the detection process, according to the pressure changes in the pipeline, the piston pressure balancer servo motor 22 is controlled to drive the piston pressure balancer screw 20 to drive the piston pressure balancer piston 19 forward or backward, and then adjust the volume of the piston pressure balancer piston cavity 21 and the overall system pipeline connection part, and finally achieve pressure balance in the overall system pipeline.

[0056] The dual-chamber piston flow generator working group of the present invention is used to generate a standard flow. The dual-chamber piston flow generator working group includes two sets of dual-chamber piston flow generators of different sizes, each set of dual-chamber piston flow generators is composed of a piston, a screw, a piston cavity, a temperature transmitter, a pressure transmitter and a servo motor. Among them, the 100L dual-chamber piston flow generator is used for the detection of large flow, and the 20L small dual-chamber piston flow generator is used for the detection of small flow. Each set of piston cavities is divided into a left cavity and a right cavity by the piston. The left cavity is a recovery cavity for recovering natural gas; the right cavity is a working cavity filled with natural gas. During the detection process, the servo motor is controlled to rotate, and then the screw is driven to move the piston to the right, and the natural gas in the right cavity is discharged from the working cavity; the discharged natural gas is in a sealed circulation loop, passes through a buffer and a meter under test, and returns to the left cavity and is collected. At the same time, a temperature transmitter and a pressure transmitter are installed on the recovery cavity to collect temperature parameters and pressure parameters during the detection process of the dual-chamber piston flow generator. The air inlet and outlet of each set of dual-chamber piston flow generators are controlled by air control valves. During the detection process, one of the dual-chamber piston flow generators is selected to connect to the test circuit according to the detected flow rate. The large dual-chamber piston flow generator is used for the detection of large flow rates (above 10 L / h), and the small dual-chamber piston flow generator is used for the detection of small flow rates (below 10 L / h), which expands the range of the detected flow rate. Specifically, the dual-chamber piston flow generator working group 24 consists of two parts: a 20L dual-chamber piston flow generator and a 100L dual-chamber piston flow generator. Among them, the piston cavity of the 20L double-chamber piston flow generator is divided into two parts, namely, a left cavity 25 of the 20L double-chamber piston flow generator and a right cavity 27 of the 20L double-chamber piston flow generator, by the 20L double-chamber piston flow generator piston 26; the left cavity 25 of the 20L double-chamber piston flow generator is connected to an air inlet at one end of the four-way T8 through the air control valve F15; the right cavity 27 of the 20L double-chamber piston flow generator is connected to an air inlet at one end of the four-way T9 through the air control valve F16; the piston cavity of the 100L double-chamber piston flow generator is divided into two parts, namely, a left cavity 30 of the 100L double-chamber piston flow generator and a right cavity 32 of the 100L double-chamber piston flow generator, by the 100L double-chamber piston flow generator piston 31; the left cavity 30 of the 100L double-chamber piston flow generator is connected to an air inlet at one end of the four-way T8 through the air control valve F14; The right chamber 32 of the 100L double-chamber piston flow generator is connected to the air inlet at one end of the four-way T9 through the air control valve 17, the air outlet at one end of the four-way T8 is connected to the air inlet at one end of the four-way T9 through the air control valve F13, the other air outlet of the four-way T8 is connected to the air outlet of the three-way T7 through the air control valve F11, and the other air outlet of the four-way T9 is connected to the air inlet of the three-way T6 through the air control valve F12.When the detection flow rate is less than 10 L / h, the air control valve F14 and the air control valve F17 are closed, the air control valve F15 and the air control valve F16 are opened, and the 20L double-chamber piston flow generator is enabled; when the detection flow rate is greater than 10L / h, the air control valve F14 and the air control valve F17 are opened, the air control valve F15 and the air control valve F16 are closed, and the 100L double-chamber piston flow generator is enabled; in this way, the movement distance of the piston can be made long enough during small flow detection, and its measurement uncertainty is consistent with that during large flow detection, thereby expanding the detection range.

[0057] The actual flow detection method of the invention, as shown in the attached Fig.13 As shown in the figure, a detection process can be summarized into the following three steps: gas replacement process, detection process and meter replacement process. After the detection starts, it is necessary to enter the gas replacement process to ensure safety and fill the test pipeline with experimental gas; then, perform the detection. During the detection process, the corresponding double-chamber piston flow generator is switched according to the detection flow; at the same time, the piston pressure balancer works to balance the pressure during the detection; the infrared optical communication interface communicates with the meter under test to quickly obtain the instantaneous flow of the meter under test and obtain the detection results efficiently. Then, it is selected according to whether the meter needs to be replaced. If the meter does not need to be replaced, the detection ends; if the meter needs to be replaced, the meter replacement process is entered. The meter replacement process prevents the escape of natural gas when the meter is unloaded by purging; at the same time, gas replacement is performed after the meter is replaced to prevent the secondary introduction of oxygen. In addition, by switching the pipeline and valve, the natural gas in the natural gas storage tank and the double-chamber piston flow generator working group is retained in the entire meter replacement process, saving gas consumption and avoiding the generation of waste gas. After the meter replacement process is completed, the above detection process is re-entered.

[0058] Among them, the gas replacement process includes two parts: nitrogen replacing air and natural gas replacing nitrogen; nitrogen replacing air reduces the oxygen content in the device to ensure safety; natural gas replaces nitrogen to ensure that the test pipeline is filled with experimental gas.

[0059] The detection process can be divided into two parts: the operation and reset of the 100L double-chamber piston flow generator, and the operation and reset of the 20L double-chamber piston flow generator. The operation and reset of the 100L double-chamber piston flow generator is used to detect large flows above 10L / h, and the operation and reset of the 20L double-chamber piston flow generator is used to detect small flows below 10L / h. At the same time, the piston pressure balancer is enabled during the detection process, and is dynamically adjusted according to the real-time pressure fluctuations in the double-chamber piston flow generator to reduce pressure fluctuations. In addition, during the detection process, an infrared optical communication interface is used to communicate with the meter under test, which can quickly read the instantaneous flow of the meter under test and efficiently obtain the test results.

[0060] The meter replacement process is a way to deal with the introduction of oxygen when replacing the prototype, which mainly includes nitrogen replacing natural gas before unloading the meter, and nitrogen replacing air and natural gas replacing nitrogen after the meter replacement. Nitrogen replaces natural gas before unloading the meter to prevent the natural gas in the pipeline from escaping into the environment due to meter unloading; nitrogen replaces air after the meter replacement to prevent oxygen from mixing into the environment and causing danger; finally, natural gas replaces nitrogen to ensure that the test pipeline is filled with experimental gas. During the meter replacement process, by controlling the gas control valve and explosion-proof vacuum pump, only the workbench of the meter being inspected and part of the pipeline participate in the meter replacement process, retaining the natural gas in the natural gas storage tank and the double-chamber piston flow generator working group.

[0061] The following is an example of a meter with left air intake as an example:

[0062] Gas replacement process:

[0063] like Figure 2 As shown, close the buffer valve group 7, the buffer valve group 11, and the air control valve F10; open the air control valve F1, the air control valve F2, the air control valve F3, the air control valve F4, the reversing valve group 15, the air control valve F9, the air control valve F11, the air control valve F12, the air control valve F13, the air control valve F14, the air control valve F15, the air control valve F16, and the air control valve F17, and then start the explosion-proof vacuum pump 14 to evacuate the gas. When the pipeline gas pressure drops to an absolute pressure of 2 kPa, the evacuation is completed, and most of the oxygen in the pipeline has been discharged.

[0064] Then as Figure 3 As shown, close the buffer valve group 7, air control valve F4, and air control valve F10, and open the buffer valve group 11, air control valve F1, air control valve F2, air control valve F3, air control valve F4, reversing valve group 15, air control valve F9, air control valve F11, air control valve F12, air control valve F13, air control valve F14, air control valve F15, air control valve F16, and air control valve F17, and start to fill nitrogen into the low-pressure nitrogen tank and pipeline. When the pipeline gas pressure rises to 100 kPa, stop filling nitrogen. At this time, the oxygen content is 2% of the initial pipeline content.

[0065] like Figure 4 As shown, close the buffer valve group 7, the buffer valve group 11, the air control valve F3, and the air control valve F10, open the air control valve F1, the air control valve F2, the air control valve F4, the reversing valve group 15, the air control valve F9, the air control valve F11, the air control valve F12, the air control valve F13, the air control valve F14, the air control valve F15, the air control valve F16, and the air control valve F17, start the explosion-proof vacuum pump 14 to evacuate the gas, and when the pipeline gas pressure drops to an absolute pressure of 5 kPa, the evacuation is completed, and at the same time, the remaining oxygen in the pipeline is discharged together with the nitrogen.

[0066] Then, Figure 5As shown, close the buffer valve group 11, air control valve 3, air control valve 4, and air control valve 10, and open the buffer valve group 7, air control valve 1, air control valve 2, reversing valve group 15, air control valve F9, air control valve F11, air control valve F12, air control valve F13, air control valve F13, air control valve F14, air control valve F15, air control valve F16, and air control valve F17, and fill the low-pressure natural gas tank and pipeline with natural gas. When the pipeline gas pressure rises to 100 kPa, stop filling with natural gas. At this time, the oxygen content is 0.04% of the initial pipeline content.

[0067] The entire gas replacement process is now complete. The oxygen concentration in the pipeline is reduced from 21% before replacement to 0.0084% after replacement, which is far lower than the 12% limit oxygen concentration (LOC) of methane.

[0068] Testing process:

[0069] When the detection flow rate is greater than 10L / h, such as Figure 6 As shown, the 100L double-chamber piston flow generator is working, closing the buffer valve group 7, buffer valve group 11, air control valve F3, air control valve F4, air control valve F10, air control valve F13, air control valve F15, and air control valve F16, and opening air control valves F1, F2, F9, F11, F12, F14, and F17. Since the meter under test is assumed to be a left intake meter, the air control valves F5 and F8 are opened in the reversing valve group 15, and the air control valves F6 and F7 are closed. After the detection starts, the servo motor 34 of the 100L double-chamber piston flow generator rotates according to the set value, driving the 100L double-chamber piston flow generator screw 33 to drive the 100L double-chamber piston flow generator piston 31 to move to the right, and the volume of the right chamber 32 of the 100L double-chamber piston flow generator is reduced, and natural gas is discharged. The discharged natural gas enters the low-pressure natural gas tank 12 through the air control valve F17, the air control valve F12 and the air control valve F1. The low-pressure natural gas tank 12 buffers the natural gas entering from the air control valve F1, and at the same time inputs natural gas from the air control valve F2 to the reversing valve group 15. After the natural gas enters the reversing valve group 15, it is output by the air control valve F6 to the left air inlet pipe 16 of the inspected meter workbench, then enters the inspected meter, and is output by the right air inlet pipe 17 of the inspected meter workbench back to the reversing valve group 15. After the natural gas enters the reversing valve group 15 for the second time, it is output by the air control valve F8, and after passing through the air control valves F11 and F14, it enters the left chamber 30 of the 100L double-chamber piston flow generator.

[0070] After the detection process starts, the piston pressure balancer 23 is dynamically adjusted according to the real-time pressure fluctuations in the dual-chamber piston flow generator. For example, when the pressure in the dual-chamber piston flow generator increases, the piston pressure balancer servo motor 22 rotates, driving the piston pressure balancer screw 20 to drive the piston pressure balancer piston 19 to move right, and the volume of the piston pressure balancer piston cavity 21 connected to the pipeline increases, thereby reducing the pressure in the pipeline to achieve balance. After the detection flow reaches the set value and stabilizes, the infrared optical communication module begins to communicate with the meter under test and returns the instantaneous flow parameters of the meter under test. At the same time, the temperature transmitter returns the temperature parameters of the meter under test, and the pressure transmitter returns the pressure parameters of the meter under test.

[0071] After the testing process is completed, Figure 7 As shown, the 100L double-chamber piston flow generator performs a reset operation, closing the buffer valve group 7, the buffer valve group 11, the air control valve F1, the air control valve F2, the air control valve F3, the air control valve F4, the reversing valve group 15, the air control valve F9, the air control valve F10, the air control valve F11, the air control valve F12, the air control valve F15, and the air control valve F16, and opening the air control valve F13, the air control valve F14, and the air control valve F17. The 100L double-chamber piston flow generator servo motor 34 rotates according to the set value, driving the 100L double-chamber piston flow generator lead screw 33 to drive 1 00L double-chamber piston flow generator piston 31 moves to the left, the volume of the left chamber 30 of the 100L double-chamber piston flow generator decreases, and the natural gas is discharged. The discharged natural gas passes through the air control valve F14 and the air control valve F13 and enters the right chamber 32 of the 100L double-chamber piston flow generator; when the double-chamber piston flow generator piston 31 moves to the left limit position, it stops immediately. At this time, the natural gas has returned from the left chamber 30 of the 100L double-chamber piston flow generator to the right chamber 32 of the 100L double-chamber piston flow generator, that is, the 100L double-chamber piston flow generator is reset.

[0072] Similarly, when the detection flow rate is less than 10L / h, Figure 8As shown, the 20L double-chamber piston flow generator is working. Close the buffer valve group 7, buffer valve group 11, air control valve F3, air control valve F4, air control valve F10, air control valve F13, air control valve F14, and air control valve F17, and open the air control valves F1, F2, F9, F11, F12, F15, and F16. Since the meter under test is assumed to be a left intake meter, in the reversing valve group 15, open the air control valves F5 and F8, and close the air control valves F6 and F7. After the test starts, the servo motor 29 of the 20L double-chamber piston flow generator rotates according to the set value, driving the lead screw 28 of the 20L double-chamber piston flow generator to drive the piston 26 of the 20L double-chamber piston flow generator to move to the right, and the volume of the right chamber 27 of the 20L double-chamber piston flow generator decreases, and the natural gas is discharged. The discharged natural gas enters the low-pressure natural gas tank 12 through the air control valve F17, the air control valve F12 and the air control valve F1. The natural gas entering the low-pressure natural gas tank 12 from the air control valve F1 Buffering is performed, and at the same time, natural gas is input from the air control valve F2 to the reversing valve group 15. After the natural gas enters the reversing valve group 15, it is output by the air control valve F6 to the left air inlet pipe 16 of the inspected meter workbench, and then enters the inspected meter, and is output from the right air inlet pipe 17 of the inspected meter workbench back to the reversing valve group 15. After the natural gas enters the reversing valve group 15 for the second time, it is output by the air control valve F8, and after passing through the air control valve F11 and the air control valve F14, it enters the left chamber 25 of the 20L double-chamber piston flow generator.

[0073] After the test is completed, if Fig. 9 As shown, the 20L double-chamber piston flow generator performs a reset operation. Close the buffer valve group 7, buffer valve group 11, air control valve F1, air control valve F2, air control valve F3, air control valve F4, reversing valve group 15, air control valve F9, air control valve F10, air control valve F11, air control valve F12, air control valve F14, air control valve F17, and open the air control valve F13, air control valve F15, and air control valve F16. The 20L double-chamber piston flow generator servo motor 29 rotates according to the set value, driving the 20L double-chamber piston flow generator screw 28 to drive the 20L double-chamber piston flow generator. The piston 26 moves to the left, the volume of the left chamber 25 of the 20L double-chamber piston flow generator decreases, and the natural gas is discharged. The discharged natural gas passes through the air control valve F14 and the air control valve F13 and enters the right chamber 27 of the 20L double-chamber piston flow generator. When the piston 26 of the 20L double-chamber piston flow generator moves to the left limit position, it stops immediately. At this time, the natural gas returns from the left chamber 25 of the 20L double-chamber piston flow generator to the right chamber 27 of the 20L double-chamber piston flow generator, that is, the resetting of the 20L double-chamber piston flow generator is completed.

[0074] Table replacement process:

[0075] To prevent natural gas from escaping, keep the natural gas in the low-pressure natural gas tank and the double-chamber piston flow generator working group, such as Fig.10 As shown, the natural gas replacement step before unloading the meter replacement process is carried out. Close the buffer valve group 7, gas control valve F1, gas control valve F2, gas control valve F4, gas control valve F9, gas control valve F11, gas control valve F12, gas control valve F13, gas control valve F14, gas control valve F15, gas control valve F16, gas control valve F17, open the buffer valve group 11, gas control valve F3, reversing valve group 15, gas control valve F10, and then fill in nitrogen to purge the inspected meter and pipeline, the purpose is to remove the natural gas in the current inspected meter and pipeline section, while retaining the natural gas in the low-pressure natural gas tank and the double-chamber piston flow generator working group. The reason why an explosion-proof vacuum pump is not used here to directly evacuate the vacuum is to prevent the natural gas from mixing with the air in the explosion-proof vacuum pump to produce safety hazards. At the same time, considering that the inspected meter and pipeline occupy a small volume of the system, the natural gas can be discharged by purge and the replacement of the inspected meter can be completed.

[0076] Since air will be introduced after replacing the meter under test, it is necessary to re-evacuate the vacuum. Fig.11 As shown, the meter replacement process is carried out and the meter is vacuumed after installation. Close the buffer valve group 7, buffer valve group 11, gas control valve 1, gas control valve 2, gas control valve 3, gas control valve 9, gas control valve F10, gas control valve 11, gas control valve 12, gas control valve 13, gas control valve F14, gas control valve F15, gas control valve F16, gas control valve F17, and open the gas control valve F4 and the reversing valve group 15. Then, start the explosion-proof vacuum pump 14 to vacuumize, and when the pipeline gas pressure drops to an absolute pressure of 2kPa, the vacuumization is completed.

[0077] After the vacuum is drawn, Fig.12 As shown, enter the nitrogen filling step in the meter replacement process. Close the buffer valve group 7, gas control valve F1, gas control valve F2, gas control valve F4, gas control valve F9, gas control valve F10, gas control valve F11, gas control valve F12, gas control valve F13, gas control valve F14, gas control valve F15, gas control valve F16, gas control valve F17, and open the buffer valve group 11 and gas control valve F3. In the reversing valve group 15, open the gas control valve F5 and gas control valve F8, and close the gas control valve F6 and gas control valve F7. Then, fill the pipeline with nitrogen. When the pipeline gas pressure rises to 100kPa, stop filling with nitrogen.

[0078] Finally, follow Fig.11 As shown, perform secondary vacuuming. When the pipeline gas pressure drops to an absolute pressure of 2 kPa, the vacuuming is completed. Figure 5 As shown in the figure, natural gas is charged into the pipeline, and when the pipeline gas pressure rises to 100kPa, the charging of natural gas is stopped. At this point, the meter replacement process is completed.

Claims

1. A gas meter real flow detection system, characterized in that It includes an air source, a buffer valve group, a low-pressure air storage tank, an explosion-proof vacuum pump, an air-controlled valve, a reversing valve group, a workbench for inspected meters, a piston pressure balancer, a double-chamber piston flow generator working group and pipelines connecting various components. The air source is connected to the low-pressure air storage tank through the buffer valve group. The low-pressure air storage tank is connected to the explosion-proof vacuum pump, the reversing valve group, the piston pressure balancer and the double-chamber piston flow generator working group through pipelines. Multiple air-controlled valves for controlling on and off are arranged on the pipeline. The reversing valve group is connected to the workbench for inspected meters, and multiple groups of inspected meters are arranged on the workbench for inspected meters.

2. A gas meter real flow detection system according to claim 1, characterized in that The gas source includes a working gas source and a protective gas source. The working gas source is natural gas, and the protective gas source is nitrogen. The working gas source and the protective gas source are arranged in an explosion-proof gas cabinet. The working gas source and the protective gas source are respectively connected to the low-pressure gas storage tank through corresponding buffer valve groups.

3. A gas meter real flow detection system according to claim 1, characterized in that The reversing valve group is used to switch the air intake direction. The reversing valve group includes four air control valves, two of which are used for the left air intake meter under test, and the other two are used for the right air intake meter under test.

4. A gas meter real flow detection system according to claim 1, characterized in that The inspected meter workbench is used to collect the flow, temperature and pressure of the inspected meter during the test process. The left and right air inlet pipes of the inspected meter workbench are equipped with temperature transmitters and pressure transmitters for collecting the temperature parameters and pressure parameters of the inspected meter. The inlet and outlet ports of each workstation of the inspected meter workbench are equipped with differential pressure transmitters and infrared optical communication interfaces. The infrared optical communication interface communicates with the inspected gas meter once every second, and can quickly obtain the instantaneous flow of the inspected meter.

5. A gas meter real flow detection system according to claim 1, characterized in that The piston pressure balancer consists of a piston, a screw, a piston cavity and a motor. The piston pressure balancer is connected to the air control valve, and the other end of the air control valve is connected to the overall system pipeline. By controlling the rotation of the servo motor, the screw is driven to drive the piston forward or backward, and then the volume cavity size of the connecting part of the piston cavity and the overall system pipeline is adjusted to balance the pressure during the operation of the double-cavity piston flow generator.

6. A gas meter real flow detection system according to claim 1, characterized in that The dual-chamber piston flow generator working group is used to generate standard flow. The dual-chamber piston flow generator working group includes a 100L dual-chamber piston flow generator and a 20L dual-chamber piston flow generator. Each dual-chamber piston flow generator is composed of a piston, a screw, a piston cavity, a temperature transmitter, a pressure transmitter and a servo motor. The piston cavity is divided into a left cavity and a right cavity by the piston. The left cavity is a recovery cavity and the right cavity is a working cavity. The temperature transmitter and the pressure transmitter are installed on the recovery cavity to collect temperature parameters and pressure parameters during the detection process of the dual-chamber piston flow generator; the air inlet and outlet of each set of dual-chamber piston flow generators are provided with air control valves. During the detection process, one of the dual-chamber piston flow generators is selected to connect to the test circuit according to the detected flow rate.

7. A gas meter real flow detection method of the gas meter real flow detection system as claimed in claim 1, characterized in that It includes gas replacement process, detection process and meter replacement process. The gas replacement process fills the test pipeline with experimental gas, and then executes the detection process. During the detection process, the 100L double-chamber piston flow generator and the 20L double-chamber piston flow generator are switched according to the detection flow. At the same time, the piston pressure balancer works to balance the pressure in the detection. The infrared optical communication interface communicates with the meter under test to quickly obtain the instantaneous flow of the meter under test. Then, a selection is made based on whether the meter needs to be replaced. If the meter does not need to be replaced, the detection is completed. If the meter needs to be replaced, the meter replacement process is entered. The meter replacement process prevents the escape of natural gas when the meter is unloaded by purging. Gas replacement is performed after the meter is replaced. After the meter replacement process is completed, the above process is repeated.

8. A gas meter real flow detection method according to claim 7, characterized in that The gas replacement process includes replacing air with nitrogen and replacing nitrogen with natural gas.

9. A gas meter real flow detection method according to claim 7, characterized in that The detection process is divided into two parts: the operation and reset of the 100L double-chamber piston flow generator and the operation and reset of the 20L double-chamber piston flow generator. The operation and reset of the 100L double-chamber piston flow generator is used to detect a large flow rate above 10L / h, and the operation and reset of the 20L double-chamber piston flow generator is used to detect a small flow rate below 10L / h. During the detection process, an infrared optical communication interface is used to communicate with the meter under test, so that the instantaneous flow rate of the meter under test can be quickly read.

10. A gas meter real flow detection method according to claim 7, characterized in that The meter replacement process includes replacing natural gas with nitrogen before meter unloading and replacing air with nitrogen and nitrogen with natural gas after meter replacement.

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