Valve fatigue test system and test method

Abstract

The invention discloses a valve fatigue test system and method, and the system comprises an execution system, a pressurization system, an auxiliary hydraulic cylinder and a test pipeline, the execution system comprises a to-be-tested valve, and the two ends of the test pipeline are connected with the inlet end and the outlet end of the to-be-tested valve respectively to form a closed-loop channel. A main cut-off valve and a check valve are installed at the positions, corresponding to the two ends of the to-be-tested valve, of the testing pipeline respectively, the testing pipeline is divided into a first channel, a second channel and a third channel through the main cut-off valve and the check valve, and the first channel and the third channel are connected to the two ends of the to-be-tested valve respectively. The check valve only allows the medium to enter the third channel from the second channel, and the auxiliary hydraulic cylinder and the pressurization system are communicated with the second channel and the third channel respectively. The valve fatigue test device can simply and quickly perform fatigue test on the valve, has the advantages of low energy consumption and high frequency, and can be widely used for verifying the fatigue sealing condition of the valve under rated working pressure (or specific pressure).

Description

Technical Field

[0001] This invention relates to the field of valve testing technology, and in particular to a fatigue testing system and method for valves (ball valves, butterfly valves, gate valves, globe valves, etc.). Background Technology

[0002] Valves are control components in pipeline fluid transport systems, used to change the cross-sectional area of ​​the passage and the direction of medium flow. They have functions such as guiding, stopping, throttling, checking, diverting, or overflowing and relieving pressure. Valves used for fluid control range from the simplest shut-off valves to various valves used in extremely complex automatic control systems. Their types and specifications are numerous, with nominal diameters ranging from extremely small instrument valves to industrial pipeline valves with diameters up to 10 meters. They can be used to control the flow of various types of fluids, including water, steam, oil, gas, slurry, various corrosive media, liquid metals, and radioactive fluids. Valve operating pressures can range from 0.0013 MPa to ultra-high pressures of 1000 MPa, and operating temperatures can range from ultra-low temperatures of -270°C to high temperatures of 1430°C.

[0003] Valves need to undergo fatigue testing before leaving the factory, and the current situation is as follows: (1) Valve pressure test, such as GB / T 13927, only specifies the sealing test standard for valves in the initial state; (2) Valve leakage test, such as GB / T 26481, only specifies the sealing test of the valve stem, packing and valve cover connection position; (3) Others, such as the Chinese invention patent disclosed in patent application number CN202410346423.2, "A fatigue testing device for valve production", which only tests the fatigue of the valve stem.

[0004] In summary, existing standards and technologies do not include fatigue testing for valve seat seals, and fatigue testing of valve stems is detached from actual operating conditions. Furthermore, in real-world conditions, internal leakage (valve seat seal leakage) is often difficult to monitor and predict, yet it is extremely important, as valve internal leakage can lead to serious production accidents. Valve seat material and structure, valve stem material and surface finish, valve body casting, and machining precision are all causes of valve seal leakage. Especially under high-pressure conditions, the erosion of the valve seat by the fluid medium is extremely severe. Inappropriate valve seat design or machining precision can easily cause fatigue deformation, leading to internal leakage. Poor valve body casting processes or designs can easily cause fatigue deformation of the valve structure, resulting in both internal and external leakage. Automated production places increasingly higher demands on valves, and their usage frequency is increasing, especially for pneumatic valves, which have short opening and closing times and high operating frequencies, placing far greater demands on them than manual valves. Given the limitations of existing standards, fatigue testing of valves (including valve seat seals, valve stem seals, and valve cover seals) is essential. Summary of the Invention

[0005] The purpose of this invention is to provide a valve fatigue testing system and method. This invention can perform fatigue testing on valves simply and quickly, and has the advantages of low energy consumption and high frequency. It can be widely used to verify the fatigue sealing condition of valves under their rated working pressure (or specific pressure).

[0006] To achieve the above objectives, the present invention provides the following technical solution: a valve fatigue testing system, comprising an execution system, a pressurization system, an auxiliary hydraulic cylinder, and a test pipeline. The execution system includes a valve to be tested. The two ends of the test pipeline are respectively connected to the inlet and outlet ends of the valve to be tested, forming a closed-loop channel. A main shut-off valve and a check valve are respectively installed on the test pipeline at the positions corresponding to the two ends of the valve to be tested. The main shut-off valve and the check valve divide the test pipeline into a first channel, a second channel, and a third channel. The first channel and the third channel are respectively connected to the two ends of the valve to be tested, and the check valve only allows the medium to enter the third channel from the second channel. The auxiliary hydraulic cylinder and the pressurization system are respectively connected to the second channel and the third channel.

[0007] By adopting the above technical solution, a closed-loop testing system is constructed. This system uses the valve under test as the core object of the test, ensuring that the test directly targets the valve body, avoiding errors introduced by additional structures, and accurately reflecting the performance changes of the valve under test during fatigue. The check valve only allows the medium to enter the third channel from the second channel. Based on the unidirectional characteristic of the check valve, the medium flow direction is strictly restricted when the pressurization system is working, simulating the scenario where the outlet side is under pressure when the valve is closed. Testers can not only directly observe whether there is leakage at the valve stem, packing, and valve cover connection points of the valve under test, but this structure also helps to detect whether leakage occurs in the valve seat seal during cyclic testing, achieving real-time monitoring of internal leakage. This testing system is simple and quick to operate, and has the advantages of low energy consumption and high frequency, and can be widely used to verify the fatigue sealing condition of valves under their rated working pressure (or specific pressure).

[0008] The present invention is further configured to include a first bypass shut-off valve and a second bypass shut-off valve disposed on both sides of the main shut-off valve, and a third bypass shut-off valve and a fourth bypass shut-off valve disposed on both sides of the check valve. The first bypass shut-off valve and the second bypass shut-off valve are respectively connected to the first channel and the second channel through the first bypass pipe and the second bypass pipe, respectively. The third bypass shut-off valve and the fourth bypass shut-off valve are respectively connected to the third channel and the second channel through the third bypass pipe and the fourth bypass pipe, respectively.

[0009] By adopting the above technical solution, the first bypass shut-off valve, the second bypass shut-off valve, the third bypass shut-off valve, and the fourth bypass shut-off valve are connected to the external oil supply pipeline. When the first bypass shut-off valve, the second bypass shut-off valve, the third bypass shut-off valve, and the fourth bypass shut-off valve are opened, the valve to be tested, the auxiliary hydraulic cylinder, and the test pipeline can be filled with liquid to ensure that the oil pressure in each part is the same in the initial state.

[0010] The invention is further configured such that the third channel is connected to a hydraulic pressure gauge via a fifth bypass pipe.

[0011] By adopting the above technical solution, an independent pressure monitoring path is added. The hydraulic pressure gauge, as a pressure sensing element, converts the pressure signal of the third channel into a visual reading, which makes it easy for the operator to accurately adjust the pressure in the third channel to the rated working pressure of the valve under test during the test process.

[0012] The present invention is further configured such that a glass tube level gauge is installed at the end of the first bypass shut-off valve away from the first bypass pipeline.

[0013] By adopting the above technical solution, in the sealing test process, when the first bypass shut-off valve is opened and the main shut-off valve, the second bypass shut-off valve, the third bypass shut-off valve, and the fourth bypass shut-off valve are closed, if there is leakage in the valve seat seal, the medium will flow into the glass tube level gauge through the first bypass pipe, causing the liquid level to rise, thereby providing a clear and direct visual signal to judge the sealing status, improving the practicality and ease of operation of the test.

[0014] The present invention is further configured such that the execution system includes a pneumatic actuator, the valve under test is provided with a first bracket, the pneumatic actuator is mounted on the first bracket, and the output end of the pneumatic actuator is linked to the valve stem of the valve under test through a first coupling.

[0015] By adopting the above technical solution, the valve under test can be opened and closed pneumatically, enabling high-frequency cyclic testing of the valve under test.

[0016] The present invention is further configured such that the boosting system includes a boosting hydraulic cylinder and a boosting air cylinder, a second bracket is mounted on the boosting hydraulic cylinder, the boosting air cylinder is mounted on the second bracket, and the output end of the boosting air cylinder is linked to the piston rod of the boosting hydraulic cylinder through a second coupling.

[0017] By adopting the above technical solution, the booster cylinder provides the power source for the movement of the booster hydraulic cylinder, which is also beneficial for high-frequency cyclic testing of the valve under test.

[0018] The present invention is further configured to include a first pneumatic pipeline and a second pneumatic pipeline, the first pneumatic pipeline and the second pneumatic pipeline being connected to a pneumatic actuator and a booster cylinder, respectively. The first pneumatic pipeline is provided with a first commutator for controlling the pneumatic actuator to perform a reversing action, and the second pneumatic pipeline is provided with a second commutator for controlling the booster cylinder to perform a reversing action.

[0019] By adopting the above technical solution and setting up independent pneumatic pipelines and reversing devices, precise and individual control of the pneumatic actuator and booster cylinder is achieved, thereby ensuring accurate control of the valve opening and closing and pressure generation during the test.

[0020] The present invention is further configured to include a main air pressure pipeline connected to an air source, wherein the first air pressure pipeline and the second air pressure pipeline are both connected to the main air pressure pipeline, and the first air pressure pipeline is provided with a first filter pressure reducing valve for controlling the air pressure in the first air pressure pipeline, and the second air pressure pipeline is provided with a second filter pressure reducing valve for controlling the air pressure in the second air pressure pipeline.

[0021] By adopting the above technical solution, the entire system can share the same gas source, avoiding control deviations caused by pressure differences when multiple gas sources are supplied.

[0022] The present invention is further configured such that both the first commutator and the second commutator are two-position five-way solenoid valves.

[0023] By adopting the above technical solutions, the accuracy and response efficiency of airflow control have been effectively improved.

[0024] This invention also provides a testing method for a valve fatigue testing system, comprising the following steps: S1. Initial operating condition settings: Ⅰ. De-energize the first and second commutators, and open the main shut-off valve, the first bypass shut-off valve, the second bypass shut-off valve, the third bypass shut-off valve, and the fourth bypass shut-off valve to fill the valve under test, the auxiliary hydraulic cylinder, and the test pipeline with liquid; II. Close the first bypass shut-off valve, the second bypass shut-off valve, the third bypass shut-off valve, and the fourth bypass shut-off valve, and adjust the first filter pressure reducing valve so that the pneumatic actuator can normally open and close the valve under test; Ⅲ. When the second commutator is energized, the air source pressure of the second filter pressure reducing valve is adjusted so that the hydraulic pressure gauge reaches the rated working pressure P2 of the valve under test. S2, Loop Test Process: Ⅰ. Open the main shut-off valve and close the first bypass shut-off valve, the second bypass shut-off valve, the third bypass shut-off valve, and the fourth bypass shut-off valve; II. The first and second commutators are cyclically controlled by time relays or PLCs to control the power-on and power-off times, thereby achieving load fatigue testing. III. When the hydraulic pressure gauge displays the rated working pressure P2 of the valve under test, the valve under test is open; when the hydraulic pressure gauge displays a pressure value of 0, the valve under test is closed. IV. Reciprocating cycle step III: Valve status under test; S3. Sealing Test Procedure: Ⅰ. During the cyclic test, observe whether there is any leakage at the valve stem, packing, and valve cover connection points of the valve under test; II. Close the cycle test control, open the first bypass shut-off valve, and close the main shut-off valve, the second bypass shut-off valve, the third bypass shut-off valve, and the fourth bypass shut-off valve; III. When the first commutator is de-energized and the valve under test is in the closed state, the second commutator is energized, and the pressure difference between the inlet and outlet of the valve under test is the rated working pressure of the valve under test, G=P2; IV. Observe whether there is a change in the liquid level of the glass tube level gauge. If the liquid level of the glass tube level gauge rises, the valve seat seal of the valve under test is leaking. If the liquid level of the glass tube level gauge remains unchanged, the valve seat seal of the valve under test is good.

[0025] By adopting the above technical solution, this test method, through initial working condition setting, cyclic test process and sealing test process, can not only directly observe with the naked eye whether there is leakage at the valve stem, packing and valve cover connection position of the valve under test, but also detect whether there is leakage in the valve seat seal, realizing real-time monitoring of internal leakage. Thus, it realizes comprehensive fatigue testing of valves under simulated actual high pressure conditions. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 This is a schematic diagram showing the change of the on / off state of the first and second commutators of the present invention over time. Figure 3 This is a schematic diagram showing the pressure change over time displayed by the hydraulic pressure gauge of the present invention; Figure 4 This is a diagram showing the medium flow direction of the system at time t1. Figure 5 This is a diagram showing the medium flow direction of the system at time t2. Figure 6 This is a flow diagram of the sealing detection medium in the system of the present invention.

[0027] In the diagram: 1. Execution system; 2. Pressurization system; 3. Auxiliary hydraulic cylinder; 4. Test pipeline; 5. Valve under test; 6. Main shut-off valve; 7. Check valve; 8. First channel; 9. Second channel; 10. Third channel; 11. First bypass shut-off valve; 12. Second bypass shut-off valve; 13. Third bypass shut-off valve; 14. Fourth bypass shut-off valve; 15. First bypass pipeline; 16. Second bypass pipeline; 17. Third bypass pipeline; 18. Fourth bypass pipeline; 19. Fifth bypass pipe; 20. Hydraulic pressure gauge; 21. Glass tube level gauge; 22. Pneumatic actuator; 23. First support; 24. First coupling; 25. Booster hydraulic cylinder; 26. Booster air cylinder; 27. Second support; 28. Second coupling; 29. ​​First pneumatic pipeline; 30. Second pneumatic pipeline; 31. First commutator; 32. Second commutator; 33. Main pneumatic pipeline; 34. First filter pressure reducing valve; 35. Second filter pressure reducing valve. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] Example: As attached Figures 1-6The valve fatigue testing system shown includes an execution system 1, a pressurization system 2, an auxiliary hydraulic cylinder 3, and a test pipeline 4. The execution system 1 includes a valve under test 5 (ball valve, butterfly valve, gate valve, etc.). The valve under test 5 is a conventional valve on the market, so its specific structure will not be described in detail here. The two ends of the test pipeline 4 are connected to the inlet and outlet ends of the valve under test 5, respectively, forming a closed loop channel. A main shut-off valve 6 and a check valve 7 are installed on the test pipeline 4 at the positions corresponding to the two ends of the valve under test 5, respectively. The main shut-off valve 6 and the check valve 7 divide the test pipeline 4 into a first channel 8, a second channel 9, and a third channel 10. The first channel 8 and the third channel 10 are respectively connected to the two ends of the valve under test 5, and the check valve 7 only allows the medium to enter the third channel 10 from the second channel 9. The auxiliary hydraulic cylinder 3 and the pressurization system 2 are respectively connected to the second channel 9 and the third channel 10. This structure constructs a closed-loop testing system, using the valve under test (5) as the core object of the test. This ensures the test directly targets the valve body, avoiding errors introduced by additional structures and accurately reflecting the performance changes of the valve under test (5) during fatigue. The check valve (7) only allows the medium to enter the third channel (10) from the second channel (9). Based on the unidirectional characteristic of the check valve (7), the medium flow direction is strictly restricted when the pressurization system (2) is operating, simulating the pressure scenario on the outlet side when the valve is closed. Testers can not only directly observe whether there is leakage at the valve stem, packing, and valve cover connection points of the valve under test (5) with the naked eye, but this structure also helps to detect whether leakage occurs in the valve seat seal during cyclic testing, achieving real-time monitoring of internal leakage. This testing system is simple and quick to operate, and has the advantages of low energy consumption and high frequency, and can be widely used to verify the fatigue sealing condition of valves under their rated working pressure (or specific pressure).

[0030] As attached Figure 1 As shown, the system also includes a first bypass shut-off valve 11 and a second bypass shut-off valve 12 located on both sides of the main shut-off valve 6, and a third bypass shut-off valve 13 and a fourth bypass shut-off valve 14 located on both sides of the check valve 7. The first bypass shut-off valve 11 and the second bypass shut-off valve 12 are connected to the first channel 8 and the second channel 9 respectively through the first bypass pipe 15 and the second bypass pipe 16. The third bypass shut-off valve 13 and the fourth bypass shut-off valve 14 are connected to the third channel 10 and the second channel 9 respectively through the third bypass pipe 17 and the fourth bypass pipe 18. The first bypass shut-off valve 11, the second bypass shut-off valve 12, the third bypass shut-off valve 13, and the fourth bypass shut-off valve 14 are connected to the external oil supply pipe. When the first bypass shut-off valve 11, the second bypass shut-off valve 12, the third bypass shut-off valve 13, and the fourth bypass shut-off valve 14 are opened, they can fill the valve 5 under test, the auxiliary hydraulic cylinder 3, and the test pipe 4 with liquid, ensuring that the oil pressure in each part is the same in the initial state.

[0031] As attached Figure 1As shown, the third channel 10 is connected to a hydraulic pressure gauge 20 via a fifth bypass pipe 19. An independent pressure monitoring path is added, with the hydraulic pressure gauge 20 acting as a pressure sensing element to convert the pressure signal of the third channel 10 into a visible reading. This allows operators to accurately adjust the pressure within the third channel 10 to the rated working pressure of the valve 5 under test during the testing process.

[0032] As attached Figure 1 As shown, a glass tube level gauge 21 is installed at the end of the first bypass shut-off valve 11 away from the first bypass pipe 15. During the sealing test procedure, when the first bypass shut-off valve 11 is opened and the main shut-off valve 6, the second bypass shut-off valve 12, the third bypass shut-off valve 13, and the fourth bypass shut-off valve 14 are closed, if there is leakage in the valve seat seal, the medium will flow into the glass tube level gauge 21 through the first bypass pipe 15, causing the liquid level to rise. This provides a clear and direct visual signal to judge the sealing status, improving the practicality and ease of operation of the test.

[0033] As attached Figure 1 As shown, the execution system 1 also includes a pneumatic actuator 22 (angular stroke pneumatic actuator 22 or linear stroke pneumatic actuator 22). A first bracket 23 is provided on the valve under test 5, and the pneumatic actuator 22 is mounted on the first bracket 23. The output end of the pneumatic actuator 22 is linked to the valve stem of the valve under test 5 via a first coupling 24. By driving the opening and closing action of the valve under test 5 pneumatically, high-frequency cyclic testing of the valve under test 5 can be achieved.

[0034] As attached Figure 1 As shown, the pressurization system 2 includes a pressurization hydraulic cylinder 25 and a pressurization air cylinder 26. A second bracket 27 is mounted on the pressurization hydraulic cylinder 25, and the pressurization air cylinder 26 is mounted on the second bracket 27. The output end of the pressurization air cylinder 26 is linked to the piston rod of the pressurization hydraulic cylinder 25 through a second coupling 28. The pressurization air cylinder 26 provides the power source for the movement of the pressurization hydraulic cylinder 25, which is also beneficial for high-frequency cyclic testing of the valve 5 under test.

[0035] As attached Figure 1 As shown, the system also includes a first pneumatic pipeline 29 and a second pneumatic pipeline 30. The first pneumatic pipeline 29 and the second pneumatic pipeline 30 are respectively connected to the pneumatic actuator 22 and the booster cylinder 26. The first pneumatic pipeline 29 is equipped with a first directional switch 31 for controlling the pneumatic actuator 22 to perform a reversing action, and the second pneumatic pipeline 30 is equipped with a second directional switch 32 for controlling the booster cylinder 26 to perform a reversing action. By setting independent pneumatic pipelines and directional switches, precise and individual control of the actions of the pneumatic actuator 22 and the booster cylinder 26 is achieved, thereby ensuring accurate control of the opening and closing of the valve 5 under test and the generation of pressure during the test.

[0036] As attached Figure 1 As shown, the system also includes a main air pressure pipeline 33 connected to the air source. The first air pressure pipeline 29 and the second air pressure pipeline 30 are both connected to the main air pressure pipeline 33. The first air pressure pipeline 29 is equipped with a first filter pressure reducing valve 34 for controlling the air pressure within the first air pressure pipeline 29, and the second air pressure pipeline 30 is equipped with a second filter pressure reducing valve 35 for controlling the air pressure within the second air pressure pipeline 30. This design allows the entire system to share the same air source, avoiding control deviations caused by pressure differences when multiple air sources are supplied.

[0037] More specifically, the first commutator 31 and the second commutator 32 are both two-position five-way solenoid valves, which are marked as Ev1 and Ev2 in the figure, respectively.

[0038] The test method using this valve fatigue testing system includes the following steps: S1. Initial operating condition settings: Ⅰ. De-energize the first and second commutators, and open the main shut-off valve, the first bypass shut-off valve, the second bypass shut-off valve, the third bypass shut-off valve, and the fourth bypass shut-off valve to fill the valve under test, the auxiliary hydraulic cylinder, and the test pipeline with liquid; II. Close the first bypass shut-off valve, the second bypass shut-off valve, the third bypass shut-off valve, and the fourth bypass shut-off valve, and adjust the first filter pressure reducing valve so that the pneumatic actuator can normally open and close the valve under test; Ⅲ. When the second commutator is energized, the air source pressure of the second filter pressure reducing valve is adjusted so that the hydraulic pressure gauge reaches the rated working pressure P2 of the valve under test. S2, Loop Test Process: Ⅰ. Open the main shut-off valve and close the first bypass shut-off valve, the second bypass shut-off valve, the third bypass shut-off valve, and the fourth bypass shut-off valve; II. As attached Figure 2 As shown, the first and second commutators are cyclically controlled by a time relay or PLC to control the power-on and power-off times, thereby achieving load fatigue testing. III. As attached Figure 3 As shown, when the hydraulic pressure gauge displays the rated working pressure P2 of the valve under test, the valve under test is open; when the hydraulic pressure gauge displays a pressure value of 0, the valve under test is closed. IV. Reciprocating cycle step III: The state of the valve to be tested, as shown in the attached diagram. Figure 4 and attached Figure 5 Two states, repeating in a cycle; S3. Sealing Test Procedure: Ⅰ. During the cyclic test, observe whether there is any leakage at the valve stem, packing, and valve cover connection points of the valve under test; II. Close the cycle test control, open the first bypass shut-off valve, and close the main shut-off valve, the second bypass shut-off valve, the third bypass shut-off valve, and the fourth bypass shut-off valve; III. As attached Figure 6 As shown, the first commutator is de-energized, the valve under test is in the closed state, the second commutator is energized, and the pressure difference between the inlet and outlet of the valve under test is the rated working pressure of the valve under test, G=P2; IV. Observe whether there is a change in the liquid level of the glass tube level gauge. If the liquid level of the glass tube level gauge rises, the valve seat seal of the valve under test is leaking. If the liquid level of the glass tube level gauge remains unchanged, the valve seat seal of the valve under test is good.

[0039] This testing method, through initial operating condition settings, cyclic testing procedures, and sealing testing procedures, not only allows for direct visual observation of whether leaks occur at the valve stem, packing, and valve cover connection points of the valve under test, but also detects whether leaks occur in the valve seat seal, achieving real-time monitoring of internal leaks. This enables comprehensive fatigue testing of valves under simulated actual high-pressure conditions.

Claims

1. A valve fatigue testing system, characterized by: The utility model provides an improved valve test system, which comprises an execution system (1), a booster system (2), an auxiliary hydraulic cylinder (3) and a test pipeline (4), the execution system (1) comprises a valve (5) to be tested, the test pipeline (4) is connected with the inlet end and the outlet end of the valve (5) to be tested respectively and forms a closed loop channel, the test pipeline (4) is provided with a main cut-off valve (6) and a check valve (7) at the positions corresponding to the two ends of the valve (5) to be tested respectively, the main cut-off valve (6) and the check valve (7) divide the test pipeline (4) into a first channel (8), a second channel (9) and a third channel (10), the first channel (8) and the third channel (10) are connected to the two ends of the valve (5) to be tested respectively, and the check valve (7) only allows the medium to enter the third channel (10) from the second channel (9), the auxiliary hydraulic cylinder (3) and the booster system (2) are connected with the second channel (9) and the third channel (10) respectively.

2. The valve fatigue testing system of claim 1, wherein: The utility model also comprises a first bypass cut-off valve (11) and a second bypass cut-off valve (12) arranged on the two sides of the main cut-off valve (6), and a third bypass cut-off valve (13) and a fourth bypass cut-off valve (14) arranged on the two sides of the check valve (7), the first bypass cut-off valve (11) and the second bypass cut-off valve (12) are connected with the first channel (8) and the second channel (9) through a first bypass pipeline (15) and a second bypass pipeline (16) respectively, and the third bypass cut-off valve (13) and the fourth bypass cut-off valve (14) are connected with the third channel (10) and the second channel (9) through a third bypass pipeline (17) and a fourth bypass pipeline (18) respectively.

3. The valve fatigue testing system of claim 2, wherein: The third channel (10) is connected with a hydraulic pressure gauge (20) through a fifth bypass pipeline (19).

4. The valve fatigue testing system of claim 3, wherein: The end of the first bypass cut-off valve (11) away from the first bypass pipeline (15) is provided with a glass tube liquid level meter (21).

5. The valve fatigue testing system of claim 1, wherein: The execution system (1) further comprises a pneumatic actuator (22), the valve (5) to be tested is provided with a first support (23), the pneumatic actuator (22) is installed on the first support (23), and the output end of the pneumatic actuator (22) is connected with the valve stem of the valve (5) to be tested through a first coupling (24).

6. A valve fatigue testing system as claimed in claim 5, wherein: The booster system (2) comprises a booster hydraulic cylinder (25) and a booster pneumatic cylinder (26), the booster hydraulic cylinder (25) is provided with a second support (27), the booster pneumatic cylinder (26) is installed on the second support (27), and the output end of the booster pneumatic cylinder (26) is connected with the piston rod of the booster hydraulic cylinder (25) through a second coupling (28).

7. A valve fatigue testing system as claimed in claim 6, wherein: The utility model also comprises a first air pressure pipeline (29) and a second air pressure pipeline (30), the first air pressure pipeline (29) and the second air pressure pipeline (30) are connected with the pneumatic actuator (22) and the booster pneumatic cylinder (26) respectively, the first air pressure pipeline (29) is provided with a first reversing device (31) for controlling the reversing action of the pneumatic actuator (22), and the second air pressure pipeline (30) is provided with a second reversing device (32) for controlling the reversing action of the booster pneumatic cylinder (26).

8. The valve fatigue testing system of claim 7, wherein: The main gas pressure pipeline (33) connected with the gas source is further included, the first gas pressure pipeline (29) and the second gas pressure pipeline (30) are connected with the main gas pressure pipeline (33), and the first filter pressure reducing valve (34) for controlling the gas pressure in the first gas pressure pipeline (29) is arranged on the first gas pressure pipeline (29), and the second filter pressure reducing valve (35) for controlling the gas pressure in the second gas pressure pipeline (30) is arranged on the second gas pressure pipeline (30).

9. The valve fatigue testing system of claim 7, wherein: The first commutator (31) and the second commutator (32) are both two-position five-way electromagnetic valves.

10. A method of testing a valve fatigue testing system according to any one of claims 1 to 9, characterized in that: The method comprises the following steps: S1, initial working condition setting: I, the first commutator and the second commutator are powered off, the main cut-off valve, the first bypass cut-off valve, the second bypass cut-off valve, the third bypass cut-off valve and the fourth bypass cut-off valve are opened, and the to-be-tested valve, the auxiliary hydraulic cylinder and the test pipeline are filled with liquid; II, the first bypass cut-off valve, the second bypass cut-off valve, the third bypass cut-off valve and the fourth bypass cut-off valve are closed, and the first filter pressure reducing valve is adjusted, so that the pneumatic actuator can normally open and close the to-be-tested valve; III, the second commutator is powered on, the gas source pressure of the second filter pressure reducing valve is adjusted, and the hydraulic pressure gauge reaches the rated working pressure P2 of the to-be-tested valve; S2, cycle test process: I, the main cut-off valve is opened, and the first bypass cut-off valve, the second bypass cut-off valve, the third bypass cut-off valve and the fourth bypass cut-off valve are closed; II, the first commutator and the second commutator are powered on and powered off through time relays or PLC cycle control, so as to realize load fatigue test; III, when the hydraulic pressure gauge displays the rated working pressure P2 of the to-be-tested valve, the to-be-tested valve is opened, and when the hydraulic pressure gauge displays a pressure value of 0, the to-be-tested valve is closed; IV, the to-be-tested valve state in step III is reciprocally cycled; S3, sealing test process: I, in the cycle test process, whether the valve rod, the packing and the valve cover connection position of the to-be-tested valve appear leakage is observed; II, the cycle test control is closed, the first bypass cut-off valve is opened, and the main cut-off valve, the second bypass cut-off valve, the third bypass cut-off valve and the fourth bypass cut-off valve are closed; III, the first commutator is powered off, the to-be-tested valve is in a closed state, the second commutator is powered on, the pressure difference between the inlet end and the outlet end of the to-be-tested valve is the rated working pressure of the to-be-tested valve, G=P2; IV, whether the liquid level of the glass tube liquid level meter changes is observed, if the liquid level of the glass tube liquid level meter rises, the valve seat sealing of the to-be-tested valve leaks, and if the liquid level of the glass tube liquid level meter does not change, the valve seat sealing of the to-be-tested valve is good.

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