A batch airtightness testing device and method for 70MPa hydrogen storage cylinders

Abstract

This invention discloses a batch airtightness testing device for 70MPa hydrogen storage cylinders, comprising a low-pressure storage tank, the outlet of which is connected to the inlet of a liquid pump. The outlet of the liquid pump is connected to the inlets of the low-pressure storage tank, the medium-pressure storage tank, and the high-pressure storage tank. The outlet of the medium-pressure storage tank is connected to the inlet of a main inlet pipe. A medium-pressure safety valve, a high-pressure check valve, and a third high-pressure solenoid valve are sequentially arranged along the inlet direction on a fifth pipeline. The outlet of the high-pressure storage tank is connected to the inlet of the main inlet pipe. A fifth high-pressure solenoid valve is installed on the main inlet pipe. The outlet of the main inlet pipe is simultaneously connected to the inlets of several branch inlet pipes, which are connected in parallel to the main inlet pipe. A sixth high-pressure solenoid valve is installed on each branch inlet pipe. A high-pressure hose is connected to the outlet of each main inlet pipe. A high-pressure valve for connecting to the hydrogen storage cylinder under test is detachably installed at the outlet of each high-pressure hose. This invention has the advantage of enabling rapid batch airtightness testing of gas cylinders.

Description

Technical Field

[0001] This invention relates to the field of 70MPa hydrogen storage cylinder air tightness testing technology, specifically to a batch air tightness testing device and method for 70MPa hydrogen storage cylinders. Background Technology

[0002] The on-board hydrogen supply system is a key component of hydrogen fuel cell vehicles. The on-board hydrogen supply system is formed by one or more hydrogen storage cylinders arranged in pipelines and mounted on a fixed frame. The air tightness test is an important means to detect the quality of the hydrogen storage cylinders. At present, the air tightness test method for 70MPa hydrogen storage cylinders is: first, use a gas-driven pressurization device to slowly pressurize the cylinder to be tested to the required air tightness pressure, and then conduct an air tightness test on the cylinder to be tested according to the relevant requirements of GB / T 35544. The air tightness test method for 70MPa hydrogen storage cylinders currently used has the following disadvantages: (1) Pressurizing the 70MPa hydrogen storage cylinder with a gas-driven pressurization device is not only slow and time-consuming, but also cannot meet the requirements of batch pressurization in subsequent production processes, and it is a great waste of personnel, equipment and production turnover; (2) Since personnel cannot leave during the pressurization operation and the pressurization operation takes a long time, people and pressure are in contact for a long time, which poses a hidden danger to safe production. Summary of the Invention

[0003] The first objective of this invention is to provide a batch airtightness testing device for 70MPa hydrogen storage cylinders that is simple to operate, highly safe, and capable of rapidly pressurizing gas cylinders in batches.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: a batch airtightness testing device for 70MPa hydrogen storage cylinders, characterized in that it includes a low-pressure storage tank, a medium-pressure storage tank, a high-pressure storage tank, a liquid pump, and an electrical control system;

[0005] The outlet of the low-pressure storage tank is connected to the inlet of the liquid pump via a first pipeline equipped with a first low-pressure solenoid valve. The outlet of the liquid pump is connected to the inlet of the low-pressure storage tank via a second pipeline equipped with a second low-pressure solenoid valve. Simultaneously, the outlet of the liquid pump is connected to the inlet of the medium-pressure storage tank via a third pipeline equipped with a first high-pressure solenoid valve. The outlet of the liquid pump is also connected to the inlet of the high-pressure storage tank via a fourth pipeline equipped with a second high-pressure solenoid valve. The outlet of the medium-pressure storage tank is connected to the inlet of the main air intake pipe via a fifth pipeline. A medium-pressure safety valve is sequentially installed along the air intake direction on the fifth pipeline. The system includes a high-pressure check valve and a third high-pressure solenoid valve. The outlet of the high-pressure storage tank is connected to the inlet of the main intake pipe via a sixth pipeline equipped with a fourth high-pressure solenoid valve. A fifth high-pressure solenoid valve is installed on the main intake pipe. The outlet of the main intake pipe is simultaneously connected to the inlets of several intake branch pipes. Each intake branch pipe is connected in parallel to the main intake pipe. A sixth high-pressure solenoid valve is installed on each intake branch pipe. A high-pressure hose is connected to the outlet of each main intake pipe. A high-pressure cylinder valve for connecting to the hydrogen storage cylinder to be tested is detachably installed at the outlet of each high-pressure hose.

[0006] The liquid pump is equipped with a remote control sensor for the pump body and a first pressure sensor for detecting the outlet pressure of the liquid pump. The medium-pressure storage tank is equipped with a second pressure sensor for detecting the tank pressure of the medium-pressure storage tank. The high-pressure storage tank is equipped with a third pressure sensor for detecting the tank pressure of the high-pressure storage tank. The air intake manifold is equipped with a fourth pressure sensor for detecting the pressure of the air intake manifold. All solenoid valves, all pressure sensors, and remote control sensors are simultaneously electrically connected to the main electrical control system, so that the main electrical control system can receive the feedback information from each pressure sensor in real time, control the operation of each solenoid valve, and control the operation of the liquid pump through the remote control sensor.

[0007] Furthermore, the aforementioned 70MPa hydrogen storage cylinder batch airtightness testing device includes: an explosion-proof wall enclosing an explosion-proof area; a low-pressure storage tank, a medium-pressure storage tank, a high-pressure storage tank, a main electrical control unit, a liquid pump, a first pipeline with a first low-pressure solenoid valve, a second pipeline with a second low-pressure solenoid valve, a third pipeline with a first high-pressure solenoid valve, a fourth pipeline with a second high-pressure solenoid valve, a fifth pipeline with a medium-pressure safety valve, a high-pressure check valve, and a third high-pressure solenoid valve, a sixth pipeline with a fourth high-pressure solenoid valve, a pump remote control sensor, a first pressure sensor, a second pressure sensor, and a third pressure sensor, all located outside the explosion-proof area; and an inlet main pipe with a fifth high-pressure solenoid valve and a fourth pressure sensor, all inlet branch pipes with a sixth high-pressure solenoid valve, all high-pressure hoses, all high-pressure cylinder valves, and all hydrogen storage cylinders to be tested, all located inside the explosion-proof area.

[0008] Furthermore, the aforementioned 70MPa hydrogen storage cylinder batch airtightness testing device includes a first venting pipeline with a first valve, which is simultaneously connected to a first pipeline, a second pipeline, a third pipeline, and a fourth pipeline.

[0009] Furthermore, the aforementioned 70MPa hydrogen storage cylinder batch airtightness testing device includes a second venting main pipeline, and each inlet branch pipe is connected to the second venting main pipeline through a second venting branch pipe equipped with a seventh high-pressure solenoid valve.

[0010] The second objective of this invention is to provide a simple, safe, and efficient method for batch testing of the airtightness of 70MPa hydrogen storage cylinders.

[0011] To achieve the above objectives, the present invention adopts the following technical solution: a batch airtightness test method for 70MPa hydrogen storage cylinders, the specific steps of which are as follows:

[0012] Step (1): First, install a high-pressure valve on the mouth of each gas cylinder to be tested, then transfer each gas cylinder to be tested into the explosion-proof area enclosed by the explosion-proof wall, and connect each gas cylinder to the high-pressure hose of an air inlet branch pipe through the high-pressure valve.

[0013] Step (2): The main control of the electrical equipment opens the first low-pressure solenoid valve and the second low-pressure solenoid valve, and starts the liquid pump, so that the liquid nitrogen in the low-pressure storage tank continuously flows into the liquid pump through the first pipeline, and then flows back to the low-pressure storage tank through the second pipeline until the liquid pump reaches the temperature set value, thus completing the pre-cooling of the liquid pump.

[0014] Step (3): After precooling is completed, the main control of the electrical equipment opens the first high-pressure solenoid valve, so that the liquid pump vaporizes and pressurizes the liquid nitrogen in the low-pressure storage tank and then smoothly fills it into the medium-pressure storage tank through the third pipeline until the tank pressure in the medium-pressure storage tank reaches 38-46 MPa.

[0015] Step (4): The main control of the electrical equipment opens the second high-pressure solenoid valve and closes the first high-pressure solenoid valve, and makes the liquid pump continue to pressurize, vaporizes and pressurizes the liquid nitrogen in the low-pressure storage tank, and then smoothly fills the high-pressure storage tank through the fourth pipeline until the tank pressure in the high-pressure storage tank reaches 89-95MPa, then stops the operation of the liquid pump and closes the second high-pressure solenoid valve.

[0016] Step (5): The main control of the electrical equipment first opens the third high-pressure solenoid valve, and after an interval of 2 to 10 seconds, opens the fifth high-pressure solenoid valve. Then, it opens the sixth high-pressure solenoid valve on each air intake branch pipe. The medium-pressure nitrogen in the medium-pressure storage tank is then smoothly filled into each gas cylinder to be tested through the fifth pipeline, the main air intake pipe, each air intake branch pipe and each high-pressure hose until the pressure in each gas cylinder to be tested reaches 39 to 41 MPa. Then, the third high-pressure solenoid valve, the fifth high-pressure solenoid valve and each sixth high-pressure solenoid valve are closed.

[0017] Step (6): The main control of the electrical equipment first opens the fourth high-pressure solenoid valve, and after an interval of 2 to 10 seconds, opens the fifth high-pressure solenoid valve. Then, it opens the sixth high-pressure solenoid valve on each air intake branch pipe. The high-pressure nitrogen in the high-pressure storage tank is then smoothly filled into each gas cylinder to be tested through the sixth pipeline, the main air intake pipe, each air intake branch pipe and each high-pressure hose until the pressure in each gas cylinder to be tested reaches 87.5 to 88.5 MPa. Then, the fourth high-pressure solenoid valve, the fifth high-pressure solenoid valve and each sixth high-pressure solenoid valve are closed.

[0018] Step (7): During the operation of steps (5) to (6), if the pressure of the medium pressure tank is less than or equal to 35MPa, then step (3) will be executed; if the pressure of the high pressure tank is less than or equal to 80MPa, then step (4) will be executed.

[0019] Step (8): Conduct an airtightness test on the gas cylinder to be tested according to the relevant requirements of GB / T 35544;

[0020] Step (9): After the test is completed, the main electrical control unit closes the fourth high-pressure solenoid valve, the fifth high-pressure solenoid valve and each of the sixth high-pressure solenoid valves in sequence; after an interval of 4 to 8 seconds, the seventh high-pressure solenoid valve, the sixth high-pressure solenoid valve and the fifth high-pressure solenoid valve are opened in sequence until the pressure of the main air intake pipe and each air intake branch pipe is reduced to zero, and then the sixth high-pressure solenoid valve and the fifth high-pressure solenoid valve are closed; then the high-pressure cylinder valves are opened until the pressure of each gas cylinder to be tested is reduced to zero, and then the seventh high-pressure solenoid valve is closed.

[0021] Step (10): The electrical equipment master control then opens the first valve in sequence and closes the first low-pressure solenoid valve and the second low-pressure solenoid valve until the pipeline pressure of the first pipeline, the second pipeline, the third pipeline and the fourth pipeline is depressurized to zero. Then, close each high-pressure cylinder valve and disconnect each high-pressure cylinder valve from the corresponding high-pressure hose. Then, move each measured gas cylinder out of the explosion-proof area enclosed by the explosion-proof wall.

[0022] Through the implementation of the above technical solutions, the beneficial effects of the present invention are: (1) It is simple and convenient to operate. Workers can achieve stable and rapid pressurization of the gas cylinder to be tested outside the explosion-proof wall. During the pressurization operation, the personnel and pressure are separated into different areas. The personnel and pressure do not need to be in contact for a long time, and the safety performance is high; (2) It adopts two-stage pressurization, which can perform batch stable and rapid pressurization of 70MPa hydrogen storage cylinders under the condition of ensuring safety. The unit consumption time is short, realizing rapid batch air tightness test of 70MPa hydrogen storage cylinders, improving the test efficiency, improving the turnover efficiency, and reducing the ineffective loss of personnel and time; (3) The device can realize electrical intelligent linkage, which can reduce operational errors and perform more effective operations; (4) It is not only applicable to batch air tightness test of 70MPa hydrogen storage cylinders, but also applicable to batch air tightness test of 70MPa and 450L or less hydrogen storage cylinders, with a wide range of applications. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structural principle of the 70MPa hydrogen storage cylinder batch airtightness testing device described in this invention. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0025] like Figure 1 As shown, the batch airtightness testing device for 70MPa hydrogen storage cylinders includes a low-pressure storage tank 1, a medium-pressure storage tank 2, a high-pressure storage tank 3, a liquid pump 4, and an electrical control system 5.

[0026] The outlet of the low-pressure storage tank 1 is connected to the inlet of the liquid pump 4 via a first pipeline 7 equipped with a first low-pressure solenoid valve 6. The outlet of the liquid pump 4 is connected to the inlet of the low-pressure storage tank 1 via a second pipeline 9 equipped with a second low-pressure solenoid valve 8. The outlet of the liquid pump 4 is also connected to the inlet of the medium-pressure storage tank via a third pipeline 11 equipped with a first high-pressure solenoid valve 10. The outlet of the liquid pump 4 is also connected to the inlet of the high-pressure storage tank 3 via a fourth pipeline 13 equipped with a second high-pressure solenoid valve 12. The outlet of the medium-pressure storage tank 2 is connected to the inlet of the main air inlet pipe 15 via a fifth pipeline 14. A medium-pressure safety valve 16 and a high-pressure stop valve are sequentially installed along the air inlet direction on the fifth pipeline 14. The outlet of the high-pressure storage tank 3 is connected to the inlet of the main air intake pipe 15 via a sixth pipeline 20 with a fourth high-pressure solenoid valve 19. A fifth high-pressure solenoid valve 21 is installed on the main air intake pipe 15. The outlet of the main air intake pipe 15 is simultaneously connected to the inlet of several air intake branch pipes 22. Each air intake branch pipe 22 is connected in parallel to the main air intake pipe 15. A sixth high-pressure solenoid valve 23 is installed on each air intake branch pipe 22. A high-pressure hose 24 is connected to the outlet of each main air intake pipe 15. A high-pressure bottle valve 26 for connecting to the hydrogen storage cylinder 25 to be tested is detachably installed at the outlet of each high-pressure hose 24.

[0027] A pump body remote control sensor 27 and a first pressure sensor 28 for detecting the outlet pressure of the liquid pump are installed on the liquid pump 4. A second pressure sensor 29 for detecting the tank pressure of the medium-pressure tank is installed on the medium-pressure tank 2. A third pressure sensor 30 for detecting the tank pressure of the high-pressure tank is installed on the high-pressure tank 3. A fourth pressure sensor 31 for detecting the pressure of the air intake manifold 15 is installed on the air intake manifold 15. All solenoid valves, all pressure sensors and remote control sensors are simultaneously electrically connected to the electrical control system 5 so that the electrical control system 5 can receive the feedback information from each pressure sensor in real time, control the operation of each solenoid valve, and control the operation of the liquid pump 4 through the remote control sensor 27.

[0028] In this embodiment, it also includes an explosion-proof wall 32, which encloses an explosion-proof area 33, a low-pressure storage tank 1, a medium-pressure storage tank 2, a high-pressure storage tank 3, a main electrical control unit 5, a liquid pump 4, a first pipeline 7 with a first low-pressure solenoid valve 6, a second pipeline 9 with a second low-pressure solenoid valve 8, a third pipeline 11 with a first high-pressure solenoid valve 10, a fourth pipeline 13 with a second high-pressure solenoid valve 12, and a fifth pipeline 14 with a medium-pressure safety valve 16, a high-pressure check valve 17, and a third high-pressure solenoid valve 18. The sixth pipeline 20 with the fourth high-pressure solenoid valve 19, the pump remote control sensor 27, the first pressure sensor 28, the second pressure sensor 29, and the third pressure sensor 30 are all located outside the explosion-proof area 33. The main air inlet pipe 15 with the fifth high-pressure solenoid valve 21 and the fourth pressure sensor 31, all air inlet branch pipes 22 with the sixth high-pressure solenoid valve 23, all high-pressure hoses 24, all high-pressure bottle valves 26, and all hydrogen storage cylinders to be tested 25 are all located inside the explosion-proof area 33.

[0029] In this embodiment, it also includes a first venting pipeline 35 with a first valve 34, which is connected to the first pipeline 7, the second pipeline 9, the third pipeline 11 and the fourth pipeline 13; it also includes a second venting main pipeline 37, and each intake branch pipe 22 is connected to the second venting main pipeline 37 through a second venting branch pipe 39 with a seventh high-pressure solenoid valve 38.

[0030] A batch airtightness test method for 70MPa hydrogen storage cylinders, the specific steps of which are as follows:

[0031] Step (1): First, install a high-pressure valve 26 at the mouth of each gas cylinder 25 to be tested. Then, transfer each gas cylinder 25 to be tested into the explosion-proof area 33 enclosed by the explosion-proof wall 32. Connect each gas cylinder 25 to be tested to the high-pressure hose 24 of an air inlet branch pipe 22 through the high-pressure valve 26.

[0032] Step (2): The main control unit 5 opens the first low-pressure solenoid valve 6 and the second low-pressure solenoid valve 8, and starts the liquid pump 4, so that the liquid nitrogen in the low-pressure storage tank 1 continuously flows into the liquid pump 4 through the first pipeline 7, and then flows back to the low-pressure storage tank 1 through the second pipeline 9, until the liquid pump 4 reaches the temperature set value, thus completing the pre-cooling of the liquid pump 4.

[0033] Step (3): After precooling is completed, the electrical control 5 opens the first high-pressure solenoid valve 10, so that the liquid pump 4 vaporizes and pressurizes the liquid nitrogen in the low-pressure storage tank 1 and then smoothly fills it into the medium-pressure storage tank 2 through the third pipeline 11 until the tank pressure in the medium-pressure storage tank 2 reaches 38-46 MPa.

[0034] Step (4): The main control unit 5 opens the second high-pressure solenoid valve 12 and closes the first high-pressure solenoid valve 10, and makes the liquid pump 4 continue to pressurize, vaporizes and pressurizes the liquid nitrogen in the low-pressure storage tank 1, and then smoothly fills the high-pressure storage tank 3 through the fourth pipeline 13 until the tank pressure in the high-pressure storage tank 3 reaches 89-95MPa, then stops the operation of the liquid pump 4 and closes the second high-pressure solenoid valve 12.

[0035] Step (5): The main control unit 5 first opens the third high-pressure solenoid valve 18, and after an interval of 2 to 10 seconds, opens the fifth high-pressure solenoid valve 21. Then, it opens the sixth high-pressure solenoid valve 23 on each air intake branch pipe 22. The medium-pressure nitrogen in the medium-pressure storage tank 2 is then steadily filled into each gas cylinder 25 under test through the fifth pipeline 14, the main air intake pipe 15, each air intake branch pipe 22 and each high-pressure hose 24 until the pressure in each gas cylinder 25 under test reaches 39 to 41 MPa. Then, the third high-pressure solenoid valve 18, the fifth high-pressure solenoid valve 21 and each sixth high-pressure solenoid valve 23 are closed.

[0036] Step (6): The main control unit 5 first opens the fourth high-pressure solenoid valve 19, and after an interval of 2 to 10 seconds, opens the fifth high-pressure solenoid valve 21. Then, it opens the sixth high-pressure solenoid valve 23 on each air intake branch pipe 22. The high-pressure nitrogen in the high-pressure storage tank 3 is then smoothly filled into each gas cylinder 25 under test through the sixth pipeline 20, the main air intake pipe 15, each air intake branch pipe 22 and each high-pressure hose 24 until the pressure in each gas cylinder 25 under test reaches 87.5 to 88.5 MPa. Then, the fourth high-pressure solenoid valve 19, the fifth high-pressure solenoid valve 21 and each sixth high-pressure solenoid valve 23 are closed.

[0037] Step (7): During the operation of steps (5) to (6), if the pressure of medium pressure tank 2 is less than or equal to 35MPa, then step (3) will be executed; if the pressure of high pressure tank 3 is less than or equal to 80MPa, then step (4) will be executed.

[0038] Step (8): Conduct an airtightness test on the gas cylinder to be tested according to the relevant requirements of GB / T 35544;

[0039] Step (9): After the test is completed, the main electrical control 5 sequentially closes the fourth high-pressure solenoid valve 19, the fifth high-pressure solenoid valve 21 and each of the sixth high-pressure solenoid valves 23; after an interval of 4 to 8 seconds, sequentially open each of the seventh high-pressure solenoid valves 38, each of the sixth high-pressure solenoid valves 23 and the fifth high-pressure solenoid valve 21 until the pressure in the main air intake pipe 15 and each of the air intake branch pipes 22 is reduced to zero, and then close each of the sixth high-pressure solenoid valves 23 and the fifth high-pressure solenoid valves 21; then open each of the high-pressure cylinder valves 26 until the pressure in each gas cylinder 25 to be tested is reduced to zero, and then close each of the seventh high-pressure solenoid valves 38.

[0040] Step (10): The electrical control 5 then sequentially opens the first valve 34 and closes the first low-pressure solenoid valve 6 and the second low-pressure solenoid valve 8 until the pipeline pressure of the first pipeline 7, the second pipeline 9, the third pipeline 11 and the fourth pipeline 13 is reduced to zero. Then, the high-pressure cylinder valves 26 are closed and the high-pressure cylinder valves 26 are disconnected from the corresponding high-pressure hoses 24. Next, the measured gas cylinders 25 are moved out of the explosion-proof area 33 enclosed by the explosion-proof wall 32.

[0041] The advantages of this invention are: (1) It is simple and convenient to operate. Workers can perform stable and rapid pressurization of the gas cylinders under test outside the explosion-proof wall. During the pressurization operation, the personnel and pressure are separated into different areas. The personnel and pressure do not need to be in contact for a long time, which ensures high safety performance; (2) It adopts two-stage pressurization, which can perform batch stable and rapid pressurization of 70MPa hydrogen storage cylinders under the condition of ensuring safety. The unit consumption time is short, realizing rapid batch air tightness test of 70MPa hydrogen storage cylinders, improving test efficiency, improving turnover efficiency, and reducing the ineffective loss of personnel and time; (3) The device can realize electrical intelligent linkage, which can reduce operational errors and perform more effective operation; (4) It is not only applicable to batch air tightness test of 70MPa hydrogen storage cylinders, but also applicable to batch air tightness test of 70MPa and 450L or less hydrogen storage cylinders, with a wide range of applications.

[0042] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other way. Any modifications or equivalent changes made based on the technical essence of the present invention shall still fall within the scope of protection claimed by the present invention.

Claims

1. A 70MPa hydrogen storage cylinder batch air tightness test device, characterized in that: The low-pressure storage tank, the medium-pressure storage tank, the high-pressure storage tank, the electric device total control, the liquid pump, the first pipeline with the first low-pressure electromagnetic valve, the second pipeline with the second low-pressure electromagnetic valve, the third pipeline with the first high-pressure electromagnetic valve, the fourth pipeline with the second high-pressure electromagnetic valve, the fifth pipeline with the medium-pressure safety valve, the high-pressure check valve and the third high-pressure electromagnetic valve, the sixth pipeline with the fourth high-pressure electromagnetic valve, the pump body remote control sensor, the first pressure sensor, the second pressure sensor and the third pressure sensor are located outside the explosion-proof area, the inlet of the inlet manifold with the fifth high-pressure electromagnetic valve and the fourth pressure sensor, all the inlet branches with the sixth high-pressure electromagnetic valve, all the high-pressure hoses, all the high-pressure bottle mouth valves and all the to-be-tested hydrogen storage cylinders are located inside the explosion-proof area.

2. The 70MPa hydrogen storage cylinder batch air tightness test device according to claim 1, characterized in that: The first dispersing pipeline with the first valve is connected with the first pipeline, the second pipeline, the third pipeline and the fourth pipeline.

3. The 70MPa hydrogen storage cylinder batch air tightness test device according to claim 2, characterized in that: The second dispersing main pipeline is connected with the second dispersing branch pipeline with the seventh high-pressure electromagnetic valve.

4. The 70MPa hydrogen storage cylinder batch air tightness test device according to claim 3, characterized in that: The specific steps of the 70MPa hydrogen storage cylinder batch air tightness test device are as follows:

5. A method for batch leak tightness test of 70MPa hydrogen storage cylinders, characterized in that: ​ Step (1): first install high-pressure cylinder valve on the mouth of each test cylinder, then transfer each test cylinder into the explosion-proof area surrounded by the explosion-proof wall, connect each test cylinder with the high-pressure hose of one gas inlet branch pipe through the high-pressure cylinder valve; Step (2): the electric control opens the first and second low-pressure electromagnetic valves and starts the liquid pump, so that the liquid nitrogen in the low-pressure storage tank flows into the liquid pump through the first pipeline and then returns to the low-pressure storage tank through the second pipeline until the liquid pump reaches the temperature setting value, completing the pre-cooling of the liquid pump; Step (3): after pre-cooling is completed, the electric control opens the first high-pressure electromagnetic valve, so that the liquid pump vaporizes and pressurizes the liquid nitrogen in the low-pressure storage tank and then smoothly charges it into the medium-pressure storage tank through the third pipeline until the tank pressure in the medium-pressure storage tank reaches 38-46 MPa; Step (4): the electric control opens the second high-pressure electromagnetic valve and closes the first high-pressure electromagnetic valve, and continues to pressurize the liquid pump, vaporizes and pressurizes the liquid nitrogen in the low-pressure storage tank and then smoothly charges it into the high-pressure storage tank through the fourth pipeline until the tank pressure in the high-pressure storage tank reaches 89-95 MPa, then stops the liquid pump and closes the second high-pressure electromagnetic valve; Step (5): the electric control opens the third high-pressure electromagnetic valve, then opens the fifth high-pressure electromagnetic valve after 2-10 seconds, and then opens the sixth high-pressure electromagnetic valve on each gas inlet branch pipe, so that the medium-pressure nitrogen in the medium-pressure storage tank is sequentially and smoothly charged into each test cylinder through the fifth pipeline, the gas inlet main pipe, each gas inlet branch pipe and each high-pressure hose until the pressure in each test cylinder reaches 39-41 MPa, then the third, fifth and sixth high-pressure electromagnetic valves are closed; Step (6): the electric control opens the fourth high-pressure electromagnetic valve, then opens the fifth high-pressure electromagnetic valve after 2-10 seconds, and then opens the sixth high-pressure electromagnetic valve on each gas inlet branch pipe, so that the high-pressure nitrogen in the high-pressure storage tank is sequentially and smoothly charged into each test cylinder through the sixth pipeline, the gas inlet main pipe, each gas inlet branch pipe and each high-pressure hose until the pressure in each test cylinder reaches 87.5-88.5 MPa, then the fourth, fifth and sixth high-pressure electromagnetic valves are closed; Step (7): during the operation of steps (5)-(6), when the tank pressure of the medium-pressure storage tank is less than or equal to 35 MPa, step (3) is executed; when the tank pressure of the high-pressure storage tank is less than or equal to 80 MPa, step (4) is executed; Step (8): according to the relevant requirements of GB / T 35544, the gas tightness test of the test cylinder is detected; Step (9): after the detection is completed, the electric control closes the fourth, fifth and sixth high-pressure electromagnetic valves in turn, then opens the seventh high-pressure electromagnetic valve, the sixth high-pressure electromagnetic valve and the fifth high-pressure electromagnetic valve after 4-8 seconds, then closes the sixth and fifth high-pressure electromagnetic valves after the pipeline pressure of the gas inlet main pipe and each gas inlet branch pipe is released to zero, and then opens the high-pressure cylinder valve until the pressure of each test cylinder is released to zero and the seventh high-pressure electromagnetic valve is closed. Step (10): the electric system control opens the first valve and closes the first low-pressure electromagnetic valve and the second low-pressure electromagnetic valve in turn, until the pipeline pressure of the first pipeline, the second pipeline, the third pipeline and the fourth pipeline is released to zero, then closes each high-pressure cylinder port valve, and separates each high-pressure cylinder port valve from the corresponding high-pressure hose, and then moves each measured gas cylinder out of the explosion-proof wall to form an explosion-proof area.

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