Plastic pipe testing system based on parallel liquid supply of multiple water tanks and testing method

Abstract

The application provides a plastic pipe testing system and method based on multiple water tanks in parallel liquid supply, which comprises the following steps: starting a centrifugal pump to establish a circulating loop supplied by multiple parallel water tanks; water solution in each water tank is respectively collected into the same liquid supply manifold through corresponding electric valves and check valves, and is delivered to each test loop group through the centrifugal pump and returned to the corresponding water tank; the volume of the water tank is less than a preset volume threshold; gas back pressure is applied to each water tank to a target pressure; each water tank is heated to a target temperature under the target pressure, the target pressure and the target temperature are maintained, and a plastic pipe sample is tested; during the testing process, the liquid level value of each water tank is obtained in real time, the liquid level difference between each water tank is calculated, and the opening of the corresponding electric valve of each water tank is adjusted according to the liquid level difference, so that the liquid level difference between each water tank is less than a preset threshold. The application realizes high-throughput liquid supply demand through parallel water tanks, and uses a closed-loop feedback control mechanism to ensure the continuity and stability of the testing process.

Description

Technical Field

[0001] This application relates to the field of plastic pipe testing technology, and in particular to a plastic pipe testing system and method based on parallel liquid supply from multiple water tanks. Background Technology

[0002] The degradation patterns of pressure resistance, temperature resistance, and chemical resistance of plastic pipes (such as PPR pipes) during long-term use cannot usually be directly obtained from actual service years. Therefore, accelerated life testing is widely used in the industry to evaluate the long-term performance of pipes. A typical test method involves installing the pipe under test in a constant-temperature test chamber, continuously flowing an aqueous solution at the same temperature as the chamber inside the pipe, and maintaining operation under constant temperature and pressure conditions until the pipe breaks and fails. Its service life is then estimated based on this.

[0003] In existing technologies, to meet the high-temperature requirements (e.g., 95℃, 105℃, 115℃) of accelerated aging tests, a sealed water tank is used as a heating and storage device for the aqueous solution. Compressed gas is introduced into the tank to create back pressure, keeping the aqueous solution in a liquid state at a temperature higher than its boiling point under normal pressure. Furthermore, to improve testing efficiency, multiple (e.g., several to dozens) plastic tube samples are typically tested simultaneously within a single testing cycle, achieving high-throughput testing. For example, patent document CN121409761A applies back pressure to the water tank, directly heating the aqueous solution to the target temperature under high pressure. The solution is then transported to multiple sample tubes via a circulation pipeline, achieving high-throughput testing and circulating supply of the aqueous solution under high-temperature and high-pressure conditions.

[0004] However, high-throughput testing significantly increases the total volume of the system's circulation pipeline. To ensure sufficient liquid supply for high-throughput testing, the water tank needs to be designed with a large volume. Furthermore, to achieve high-temperature testing conditions above 100°C (such as 105°C or 115°C), the gas back pressure inside the water tank may exceed 0.1 MPa. When storing large volumes of high-temperature, high-pressure aqueous solutions in a large-volume water tank, a leak or rupture could cause a massive, instantaneous release of the solution, resulting in violent flash evaporation and rapid expansion into a large volume of high-temperature steam. The energy released in a single event is extremely high, posing a significant safety hazard and potentially causing severe burns and impact injuries to surrounding equipment and personnel. Summary of the Invention

[0005] The purpose of this application is to provide a plastic pipe testing system and method based on multi-tank parallel liquid supply, so as to improve safety while conducting life tests on plastic pipes under high temperature, high pressure, and high throughput conditions.

[0006] To address the aforementioned technical problems, this application provides the following technical solutions: The first aspect of this application provides a testing method for plastic pipes based on parallel liquid supply from multiple water tanks, including: S1. Start the centrifugal pump to establish a circulation loop with multiple parallel water tanks supplying liquid. The aqueous solutions in each water tank are connected to the same supply manifold via corresponding electric valves and check valves, and then transported to each test loop group by the centrifugal pump and returned to the corresponding water tank. The volume of each water tank is less than a preset volume threshold. S2. Apply gas back pressure to each water tank to the target pressure. S3 heats each of the water tanks to the target temperature under the target pressure, and maintains the target pressure and the target temperature to test the plastic tube sample; During the test, S4 acquires the liquid level value of each water tank in real time, calculates the liquid level difference between each water tank, and adjusts the opening degree of the electric valve corresponding to each water tank according to the liquid level difference, so that the liquid level difference between each water tank is less than a preset threshold.

[0007] In some modified embodiments of the first aspect of this application, step S4 further includes: Calculate the rate of change of liquid level difference between each of the water tanks; Feedforward compensation control is applied to the corresponding electric valve based on the liquid level difference and the rate of change of the liquid level difference.

[0008] In some modified embodiments of the first aspect of this application, step S4 further includes: The return water temperature and back pressure value of each water tank are obtained in real time. Abnormal operating conditions are identified based on the liquid level value, the liquid level difference, the rate of change of the liquid level difference, the return water temperature, and the back pressure value. Implement the graded response strategy corresponding to the abnormal operating condition.

[0009] In some modified embodiments of the first aspect of this application, the abnormal operating conditions include: When the liquid level in any of the water tanks is lower than the first preset liquid level threshold, it is determined to be a low liquid level anomaly, and a water replenishment response is executed. When the liquid level value of any of the water tanks is higher than the second preset liquid level threshold, it is determined to be a high liquid level abnormality, and a stop water replenishment response is executed; When the liquid level difference between any of the water tanks and the other water tanks continues to increase in one direction, and the absolute value of the rate of change of the liquid level difference is less than a first preset rate threshold, and the back pressure value of the water tank is within a preset pressure fluctuation range, it is determined to be a micro-leakage condition, and a water replenishment response is executed. When the liquid level difference between any of the water tanks and the other water tanks increases, and the absolute value of the rate of change of the liquid level difference is greater than the second preset rate threshold, while the back pressure value of the water tank is lower than the preset pressure threshold, it is determined to be a pipe burst condition, and an isolation response is executed. When the liquid level values ​​of each water tank fluctuate synchronously and the absolute value of the rate of change of each liquid level difference is less than the third preset rate threshold, and the back pressure value of each water tank exceeds the preset pressure fluctuation range, it is determined to be a gas source fluctuation condition, and a back pressure adjustment response is executed. When the liquid level of any of the water tanks is higher than the third preset liquid level threshold for a preset time, and the return water temperature of the water tank is continuously lower than the preset temperature threshold, while the back pressure of the water tank is within the preset pressure fluctuation range, it is determined to be a pipeline blockage condition, and an alarm response is executed.

[0010] In some modified embodiments of the first aspect of this application, step S4 includes: The real-time suction pressure of the liquid supply manifold and the real-time temperature of the aqueous solution are obtained, and the real-time net positive suction head (NPSH) of the centrifugal pump is calculated accordingly. Obtain the required net positive suction head (NPSH) for the centrifugal pump; When the real-time effective net positive suction head (NPSH) is greater than the sum of the required NPSH and the preset safety margin, the liquid level balance control mode is executed, and the opening degree of the corresponding electric valve is adjusted according to the liquid level difference between each water tank. When the real-time effective net positive suction head (NPSH) is less than or equal to the sum of the required NPSH and the preset safety margin, the system switches to pump protection control mode, locks or increases the opening of the electric valve corresponding to the tank with the highest current liquid level, until the real-time effective NPSH recovers to a level greater than the sum of the required NPSH and the preset safety margin.

[0011] In some modified embodiments of the first aspect of this application, the electrical operating parameters of the centrifugal pump are obtained, and the electrical operating parameters include at least one of real-time current value and real-time power value; The electrical operating parameters are compared with the standard parameter values ​​under the current operating conditions; When the decrease in the electrical operating parameters relative to the standard parameter values ​​exceeds a preset deviation threshold, it is determined to be a precursor to cavitation, and the pump protection control mode is forcibly entered.

[0012] In some modified embodiments of the first aspect of this application, the preset volume threshold is 29 L; The target temperature is 95℃, 105℃, or 115℃.

[0013] The second aspect of this application provides a plastic pipe testing system based on a multi-tank parallel liquid supply, used to perform the testing method described in the first aspect, including: Multiple parallel liquid supply modules are provided, each of which includes a water tank, an electric valve, and a check valve; the volume of the water tank is less than a preset volume threshold; the outlet of the water tank is connected to the same liquid supply manifold via the electric valve and the check valve in sequence; each water tank is equipped with a heating component and a liquid level detector. A back pressure assembly is connected to each of the water tanks and is used to apply gas back pressure to each of the water tanks. The test module includes a centrifugal pump, a test liquid supply manifold, and multiple test circuit groups; the suction port of the centrifugal pump is connected to the liquid supply manifold, and the discharge port of the centrifugal pump is connected to the test liquid supply manifold; the inlet of each test circuit group is connected to the test liquid supply manifold, and the outlet is connected to the corresponding water tank. The control system is connected to each of the liquid level detectors and each of the electric valves via signal connections. The control system is configured to: acquire the real-time liquid level value detected by each of the liquid level detectors, calculate the liquid level difference between each of the water tanks, and adjust the opening degree of the corresponding electric valve according to the liquid level difference, so that the liquid level difference between each of the water tanks is less than a preset threshold.

[0014] Some modified embodiments of the second aspect of this application also include: A dosing device, connected to one of the water tanks, is used to add chemicals to the water tank.

[0015] In some modified embodiments of the second aspect of this application, each of the test circuit groups includes multiple test sub-circuits, and each of the test sub-circuits is provided with a pressure regulating valve, a first pressure gauge, a first switching valve, a second switching valve and a flow regulating valve in sequence from the water inlet end to the water outlet end; The system also includes a test chamber and a leak detection device. The pipeline between the first switching valve and the second switching valve extends through the test chamber. At least one of the plastic tube samples is connected in series on the pipeline section of the test sub-circuit located inside the test chamber. The leak detection device is located inside the test chamber.

[0016] Compared to existing technologies, the plastic pipe testing method based on parallel liquid supply from multiple water tanks provided in the first aspect of this application allows each water tank to supply water independently via a one-way valve, without interconnection. This enables multiple parallel water tanks, each with a volume smaller than a preset volume threshold, to supply liquid to the system, physically dividing the total energy storage within the system into multiple independent low-energy units. Under high-temperature and high-pressure testing conditions, even if a single water tank leaks or bursts, the limited high-temperature and high-pressure aqueous solution stored within significantly reduces the energy released in a single incident, effectively suppressing violent flash steam explosions and shock waves. This greatly reduces the harm to surrounding personnel and equipment, improving safety. Through manifold convergence, the total liquid supply capacity of the system is shared by multiple small water tanks, and the combined total flow rate is sufficient to support multi-loop parallel testing.

[0017] By leveraging the coupling relationship between liquid level difference and flow rate (higher liquid level results in higher static pressure and stronger liquid supply capacity), a closed-loop feedback control mechanism is established, using liquid level difference as the feedback variable and electric valve opening as the adjustment variable. This mechanism aims to maintain a balanced static pressure contribution at the manifold for each branch under high-temperature, high-pressure parallel liquid supply conditions by actively suppressing the liquid level difference between each tank, thus ensuring stable centrifugal pump suction pressure. Under high-temperature, high-pressure conditions, stable suction pressure effectively prevents high-temperature cavitation caused by pressure drop below saturated vapor pressure, thereby ensuring the continuity and stability of the testing process.

[0018] The plastic pipe testing method based on parallel liquid supply of multiple water tanks in this application achieves high-throughput liquid supply through a physical architecture established by multiple parallel water tanks. At the same time, it uses a closed-loop feedback control mechanism of liquid level difference and electric valve opening to ensure the stability of the centrifugal pump inlet pressure, thus ensuring the continuity and stability of the testing process. Attached Figure Description

[0019] The above and other objects, features, and advantages of exemplary embodiments of this application will become readily understood by reading the following detailed description with reference to the accompanying drawings. In the drawings, several embodiments of this application are illustrated by way of example and not limitation, with the same or corresponding reference numerals denoteing the same or corresponding parts, wherein: Figure 1 A schematic diagram of a plastic tube testing system based on parallel liquid supply from multiple water tanks is shown.

[0020] Explanation of icon numbers: 1. Liquid supply module; 11. Water tank; 12. Electric valve; 13. Check valve; 14. Heating component; 15. Inlet valve; 16. Drain valve; 17. Safety valve; 18. Second pressure gauge; 19. Exhaust valve; 110. Water replenishment device; 111. Liquid level detector; 2. Back pressure component; 21. Air compressor; 22. Pressure reducing valve; 23. Air inlet valve; 3. Test module; 31. Centrifugal pump; 32. Test liquid supply main pipe; 321. Third pressure gauge; 322. First temperature sensor; 33. Test circuit group; 331. Pressure regulating valve; 332. First pressure gauge; 333. First switching valve; 334. Second switching valve; 335. Flow regulating valve; 4. Dosing device; 41. Circulation pump; 5. Test chamber; 6. Leak detection device; 7. Plastic tube sample. Detailed Implementation

[0021] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0022] It should be noted that, unless otherwise stated, the technical or scientific terms used in this application shall have the ordinary meaning as understood by one of ordinary skill in the art to which this application pertains.

[0023] In existing technologies, to meet the requirements of high-throughput testing for media circulation, a single large-capacity water tank 11 is commonly used as a heating and storage device for high-temperature and high-pressure aqueous solutions. However, under high-temperature and high-pressure conditions, this large-capacity water tank 11 is equivalent to a huge energy accumulator. Once a leak or physical rupture occurs, the internal fluid will instantly flash-evaporate, generating a highly destructive explosion and shock wave, posing a very high safety hazard.

[0024] Further research by the inventors revealed that existing technological improvements are often limited to passive defense of the water tank 11's structure, primarily by increasing the tank's wall thickness or using higher-strength pressure-resistant materials to enhance the container's pressure resistance and explosion-proof capabilities. However, while this approach can delay or prevent rupture due to insufficient strength to some extent, it does not change the fundamental nature of concentrating a large amount of energy within a single container. In other words, existing technologies cannot fundamentally reduce the energy released in a single incident; once they fail, the consequences remain catastrophic.

[0025] The inventors of this application have moved beyond the conventional mindset of passively improving safety by simply reinforcing the structure of the water tank 11 (such as increasing wall thickness or improving materials), and instead innovated by changing the liquid supply architecture. The testing method proposed in this application, based on multiple parallel water tanks 11, isolates and prevents interconnection among multiple small-volume water tanks 11 through a one-way valve 13, and achieves converged liquid supply. This fundamentally divides the total energy storage of the system while meeting the high-throughput testing requirements for large-capacity liquid supply, significantly reducing the energy released from a single container in a single operation and improving the inherent safety of the system. Furthermore, addressing the challenge of liquid level synchronization introduced by the parallel architecture, this application utilizes a closed-loop feedback control mechanism based on the liquid level difference and the opening degree of the electric valve 12 to precisely maintain a balanced static pressure contribution in each branch, ensuring stable pressure at the inlet of the centrifugal pump 31, thereby effectively guaranteeing the continuity and stability of the high-temperature and high-pressure testing process.

[0026] Example 1

[0027] To implement the aforementioned testing method for plastic pipes based on parallel liquid supply from multiple water tanks 11, Embodiment 1 of this application provides a testing system for plastic pipes based on parallel liquid supply from multiple water tanks 11, used to execute the testing methods described in Embodiments 2-4, such as... Figure 1 As shown, it includes: Multiple parallel liquid supply modules 1 are provided, each of which includes a water tank 11, an electric valve 12, and a one-way valve 13; the volume of the water tank 11 is less than a preset volume threshold; the outlet of the water tank 11 is connected to the same liquid supply manifold via the electric valve 12 and the one-way valve 13 in sequence; each water tank 11 is equipped with a heating component 14 and a liquid level detector 111. The back pressure assembly 2 is connected to each of the water tanks 11 and is used to apply gas back pressure to each of the water tanks 11 to maintain the system under high pressure conditions.

[0028] Test module 3 includes a centrifugal pump 31, a test liquid supply manifold 32, and multiple test circuit groups 33; the suction port of the centrifugal pump 31 is connected to the liquid supply manifold, and the discharge port of the centrifugal pump 31 is connected to the test liquid supply manifold 32; the inlet of each test circuit group 33 is connected to the test liquid supply manifold 32, and the outlet is connected to the corresponding water tank 11. The control system is connected to each of the liquid level detectors 111 and each of the electric valves 12 via signals. The control system is configured to: acquire the real-time liquid level value detected by each of the liquid level detectors 111, calculate the liquid level difference between each of the water tanks 11, and adjust the opening degree of the corresponding electric valves 12 according to the liquid level difference, so that the liquid level difference between each of the water tanks 11 is less than a preset threshold, thereby maintaining the balance of static pressure contribution of each branch.

[0029] Specifically, the volume of water tank 11 is less than a preset volume threshold (e.g., less than 30 L) to limit single-point energy release. Heating component 14 is used to heat the solution to the target temperature. Liquid level detector 111 is used to monitor the liquid level of water tank 11 in real time.

[0030] In some embodiments, each liquid supply module 1 further includes an inlet valve 15, a drain valve 16, a safety valve 17, a second pressure gauge 18, an vent valve 19, and a water replenishment device 110 disposed on the water tank 11. The safety valve 17 is used to release pressure when the pressure in the water tank 11 exceeds the limit, and the water replenishment device 110 is used to replenish the solvent in the water tank 11. The drain valve 16 has a certain height and can also function as a water level limit overflow valve while draining water.

[0031] In some embodiments, the back pressure assembly 2 includes an air compressor 21, a pressure reducing valve 22, and an intake valve 23. The air compressor 21 supplies air to multiple sets of parallel water tanks 11 in sequence through the pressure reducing valve 22 and the intake valve 23, so as to provide a stable and consistent back pressure to each water tank 11.

[0032] In some embodiments, the system further includes: The dosing device 4 is connected to one of the water tanks 11 and is used to add chemicals into the water tank 11.

[0033] Furthermore, the water tank 11 is also equipped with a circulation pump 41. During operation, the circulation pump 41 circulates the solution containing a high concentration of reagent within the water tank 11 or pumps it into the main pipe. After being transported to each test circuit group 33 by the centrifugal pump 31, it is then returned to the remaining water tanks 11 via the return water pipeline. Thus, through system circulation, the aqueous solution in all water tanks 11 gradually reaches the target reagent concentration. This structure only requires one dosing device 4 to achieve uniform dosing throughout the system, making it simple in structure and low in cost.

[0034] In some embodiments, each of the test circuit groups 33 includes multiple test sub-circuits, and each test sub-circuit is provided with a pressure regulating valve 331, a first pressure gauge 332, a first switching valve 333, a second switching valve 334 and a flow regulating valve 335 in sequence from the water inlet end to the water outlet end; The system also includes a test chamber 5 and a leak detection device 6. The pipeline between the first switching valve 333 and the second switching valve 334 extends through the test chamber 5. At least one of the plastic tube samples 7 is connected in series on the pipeline section located inside the test chamber 5 for the test sub-circuit. The leak detection device 6 is located inside the test chamber 5.

[0035] Leak detection device 6 is used to detect leaks in the sample.

[0036] In some embodiments, a third pressure gauge 321 and a first temperature sensor 322 are also provided on the test liquid supply main pipe 32.

[0037] In some embodiments, each of the test circuit groups 33 includes two, three or more test sub-circuits, and each test circuit may be equipped with a plastic tube sample 7, or a plastic tube sample 7 may be connected in series according to test requirements.

[0038] In some embodiments, a suction pressure sensor (not shown in the figure) is also provided on the liquid supply manifold (i.e., before the suction port of the centrifugal pump 31) to monitor the suction port pressure of the centrifugal pump 31 in real time, so as to cooperate with the control system to prevent high-temperature cavitation.

[0039] In some embodiments, a second temperature sensor (not shown in the figure) may also be provided at the return water end of each of the test sub-circuits for real-time acquisition of the return water temperature.

[0040] In some embodiments, each water tank 11 is further equipped with a third temperature sensor for measuring the temperature of the aqueous solution inside the tank. The control system performs closed-loop control of the heating assembly 14 based on feedback from the third temperature sensor to maintain the target temperature.

[0041] All sensors, pressure gauges, valves, and other components in this system can be connected to the control system signals to achieve automated control.

[0042] Example 2

[0043] Embodiment 2 of this application provides a testing method for plastic pipes based on parallel liquid supply from multiple water tanks 11, referring to... Figure 1 ,include: S1 starts the centrifugal pump 31 to establish a circulation loop supplied by multiple parallel water tanks 11; wherein, the aqueous solution in each water tank 11 is respectively connected to the same supply manifold through the corresponding electric valve 12 and check valve 13, and is transported to each test loop group 33 by the centrifugal pump 31, and then flows back to the corresponding water tank 11; the volume of the water tank 11 is less than the preset volume threshold.

[0044] Specifically, the system initialization and water filling operation are performed first. The operator opens the drain valve 16 and vent valve 19 on all water tanks 11 and fills each water tank 11 with water through the inlet valve 15. When water is observed overflowing from the drain valve 16, the centrifugal pump 31 is started. At this time, due to the suction effect of the centrifugal pump 31, the liquid level in the water tank 11 will temporarily drop. Therefore, water needs to be continuously filled into the water tank 11 through the inlet valve 15 until the water is stably discharged from the drain valve 16 again and the pressure in each test circuit group 33 reaches the set pressure value, indicating that all water tanks 11 and test pipelines are full of water and have reached the predetermined water level. At this time, all drain valves 16 and vent valves 19 are closed.

[0045] Subsequently, the centrifugal pump 31 is kept running to establish a circulation loop. In this loop, the aqueous solutions in each water tank 11 are channeled into the same supply manifold via the corresponding electric valve 12 and check valve 13. The check valve 13 ensures that the branches do not cross-flow. After being pressurized by the centrifugal pump 31, the combined aqueous solution is delivered to the inlet of each test loop group 33 through the test supply manifold 32, flows through the plastic tube sample 7, and finally returns to the corresponding water tank 11, forming a closed-loop circulation.

[0046] Based on fluid energy calculations, under operating conditions of 0.2 MPa air pressure and 115℃ water temperature, when a sealed cavity with a volume less than 30 L ruptures, the released expansion energy is controlled within a low-risk range recognized by practical engineering experience. This allows the water tank 11 to achieve an acceptable safety level in engineering practice without the need for an additional complex heavy-duty explosion-proof shell. Conversely, when the volume exceeds 30 L, the energy released in a single rupture under the same temperature and pressure conditions will increase dramatically, necessitating the addition of expensive protective facilities, leading to a significant increase in equipment costs. Therefore, the volume of each water tank 11 in this application can be less than 30 L (i.e., the preset volume threshold can be 30 L), for example, the volume of each water tank 11 can be 29 L or 28 L, etc. To further enhance safety, preferably, the preset volume threshold is 29 L (i.e., the volume of a single water tank 11 is limited to less than 29 L), reserving a 1 L safety margin to ensure that the effective volume of the water tank is always below 30 L in actual engineering practice. This design physically divides the system's total energy storage into multiple independent low-energy units, fundamentally reducing the risk level of potential accidents and effectively improving the overall safety of the system.

[0047] S2 applies gas back pressure to each of the water tanks 11 to the target pressure.

[0048] Specifically, the intake valve 23 is opened, and the compressed air generated by the air compressor 21 is supplied to the gas phase space of each water tank 11 after being reduced in pressure by the pressure reducing valve 22. The gas pressure applied to the water tank 11 is controlled by adjusting the pressure reducing valve 22. The pressure change in each water tank 11 can be monitored by the second pressure gauge 18 installed on the water tank 11 until the pressure in all water tanks 11 stabilizes and reaches the target pressure (e.g., 0.2 MPa). At this time, the intake valve 23 is closed or maintained to keep the system back pressure constant.

[0049] S3 heats each of the water tanks 11 to the target temperature under the target pressure, and maintains the target pressure and the target temperature to test the plastic tube sample 7.

[0050] Specifically, after the back pressure is established, the heating components 14 (such as heating rods) in each water tank 11 are turned on to heat the aqueous solution. The temperature of the aqueous solution is monitored in real time by a third temperature sensor, and the heating power is adjusted until the water temperature reaches the set target temperature (e.g., 115°C). During this period, the test pressure of each test circuit can be adjusted by the pressure regulating valve 331 on each test circuit group 33, and automatically monitored by the first pressure gauge 332. At the same time, according to the test requirements, reagents can be added to the system using the dosing device 4, and the solution is circulated and mixed to reach the required pH value or residual chlorine and other physical properties. After the system is stably maintained at the target pressure and target temperature, a long-term pressure and temperature resistance test is started on the plastic tube sample 7, and the leak detection device 6 is used to monitor whether the sample leaks in real time.

[0051] In some embodiments, the target temperature is 95°C, 105°C, or 115°C.

[0052] During the test, S4 acquires the liquid level value of each water tank 11 in real time, calculates the liquid level difference between each water tank 11, and adjusts the opening degree of the electric valve 12 corresponding to each water tank 11 according to the liquid level difference, so that the liquid level difference between each water tank 11 is less than a preset threshold.

[0053] In the parallel water tanks 11, a higher liquid level results in greater static pressure and stronger liquid supply capacity. To maintain a balanced static pressure contribution at the liquid supply manifold and ensure stable inlet pressure of the centrifugal pump 31, the control system collects the liquid level values ​​detected by the level detectors 111 in each water tank 11 in real time and calculates the liquid level difference between each water tank 11. Based on this liquid level difference, the control system outputs control signals through proportional-integral-derivative (PID) or other control algorithms to adjust the opening degree of each branch electric valve 12.

[0054] The number of parallel water tanks 11 is preferably two, but it can also be three or more.

[0055] In some embodiments, the control system may employ any one of the following strategies for adjustment: the mean method, the adjacent comparison method, or the benchmark comparison method. Regardless of the strategy employed, the core logic is to synchronously adjust the opening of the corresponding electric valve 12 according to the liquid level difference, thereby achieving dynamic balance of flow in each branch.

[0056] When using the mean method, the average level of all water tanks 11 is calculated. For water tanks 11 with levels higher than the average, the corresponding electric valve 12 is opened to increase the output of that branch, and the centrifugal pump 31 is used to lower the level of that water tank 11 to the average. For water tanks 11 with levels lower than the average, the corresponding electric valve 12 is closed to reduce the output of that branch, and the level of that water tank 11 is raised back to the average, thus making all levels more consistent.

[0057] When using the adjacent comparison method, taking two water tanks 11 as an example, the control system calculates the liquid level difference between them. When the liquid level of one water tank 11 (denoted as the first water tank 11) is higher than that of the other water tank 11 (denoted as the second water tank 11), the electric valve 12 of the branch of the first water tank 11 is opened wider and the electric valve 12 of the branch of the second water tank 11 is closed smaller; and vice versa. When the system contains three or more water tanks 11, they can be compared pairwise in adjacent order, or any water tank 11 can be compared with its adjacent water tanks 11, and the corresponding electric valves 12 can be adjusted accordingly.

[0058] When using the benchmark comparison method, any one of the water tanks 11 can be used as the benchmark tank, and the liquid levels of the other water tanks 11 can be compared with those of the benchmark tank and adjusted accordingly. At the same time, the electric valve 12 of the benchmark tank can also participate in the adjustment with the average liquid level of all water tanks 11 as the target, or maintain the current opening degree unchanged, and automatically switch to adjusting with the average value as the target when the liquid level of the benchmark tank exceeds the preset safety range.

[0059] In some embodiments, the preset fluctuation threshold is any value between ±5 mm and ±30 mm, preferably ±15 mm. The control system is configured to: output an adjustment command to change the opening degree of the corresponding electric valve 12 only when the absolute value of the deviation between the real-time liquid level of any water tank 11 and the target liquid level (average value or reference value) exceeds the preset fluctuation threshold; when the absolute value of the deviation is within the range of the preset fluctuation threshold, maintain the current opening degree of each electric valve 12 unchanged. By limiting the threshold to a reasonable range, it can be ensured that the liquid level deviation between each water tank 11 is not significantly affected by the static pressure stability of the liquid supply manifold, and the system can be avoided from being too sensitive and frequently adjusted.

[0060] Compared to existing technologies, the plastic pipe testing method based on parallel liquid supply from multiple water tanks 11 provided in Embodiment 2 of this application utilizes multiple parallel water tanks 11 with volumes smaller than a preset volume threshold to supply liquid to the system, physically dividing the total energy storage within the system into multiple independent low-energy units. Under high-temperature and high-pressure testing conditions, even if a single water tank 11 leaks or bursts, the energy released in a single leak is significantly reduced due to the limited high-temperature and high-pressure aqueous solution stored inside, thereby effectively suppressing violent flash steam explosions and shock waves, greatly reducing the damage to surrounding personnel and equipment, and improving safety. Simultaneously, the one-way valves 13 installed in each branch ensure that the water tanks 11 do not cross-flow when they converge before the pump, avoiding backflow of aqueous solution due to pressure differences between branches. Through the convergence of the manifold, the total liquid supply capacity of the system is shared by multiple small water tanks 11, and the total flow rate after aggregation is sufficient to support multi-loop parallel testing.

[0061] By leveraging the coupling relationship between liquid level difference and flow rate (higher liquid level results in higher static pressure and stronger liquid supply capacity), a closed-loop feedback control mechanism is established, using liquid level difference as the feedback quantity and the opening degree of electric valve 12 as the adjustment quantity. This mechanism aims to maintain a balanced static pressure contribution at the manifold of each branch under high-temperature and high-pressure parallel liquid supply conditions by actively suppressing the liquid level difference between each water tank 11, thus ensuring stable suction pressure at the inlet of centrifugal pump 31. Under high-temperature and high-pressure conditions, stable suction pressure effectively prevents high-temperature cavitation caused by pressure drop below saturated vapor pressure, thereby ensuring the continuity and stability of the testing process.

[0062] The plastic pipe testing method based on parallel liquid supply of multiple water tanks 11 in this application achieves high-throughput liquid supply through the physical architecture established by multiple parallel water tanks 11. At the same time, the closed-loop feedback control mechanism of liquid level difference-electric valve 12 opening degree ensures the stability of the suction pressure of centrifugal pump 31, thus guaranteeing the continuity and stability of the testing process.

[0063] Example 3

[0064] Embodiment 3 of this application provides a testing method for plastic pipes based on parallel liquid supply from multiple water tanks 11, which differs from Embodiment 2 in that: refer to Figure 1 Step S4 further includes: Calculate the rate of change of liquid level difference between each of the water tanks 11; Feedforward compensation control is applied to the corresponding electric valve 12 based on the liquid level difference and the rate of change of the liquid level difference.

[0065] Specifically, the control system records the liquid level data of each water tank 11 at continuous time points. By analyzing the trend of the liquid level difference over time, it calculates the rate of increase or decrease of the liquid level difference (i.e., the amount of change in the liquid level difference per unit time). This rate of change reflects the development trend of the unbalanced liquid supply state of each parallel water tank 11: for example, when the rate of change of the liquid level difference is large, it means that the liquid level difference between the two water tanks 11 is changing rapidly. If not intervened in time, it will soon exceed the safety threshold or cause large pressure fluctuations.

[0066] Based on this, the control system superimposes feedforward compensation control logic on the feedback control (such as PID regulation) described in Example 2: When the rate of change of the liquid level difference is detected to indicate that the difference is rapidly increasing (i.e., the absolute value of the liquid level difference is continuously increasing), the control system no longer simply waits for the liquid level difference to reach the preset threshold before performing hysteresis adjustment. Instead, it sends a compensation adjustment command to the corresponding electric valve 12 in advance based on the magnitude and direction of the rate of change.

[0067] For example, if the level difference between the first water tank 11 and the second water tank 11 is detected to be increasing rapidly (i.e., the level in the first water tank 11 is rising too fast or the level in the second water tank 11 is falling too fast), the control system will add an additional "opening compensation" for the electric valve 12 of the first water tank 11 and / or a "closing compensation" for the electric valve 12 of the second water tank 11, based on the PID output adjustment. The magnitude of this compensation action increases with the rate of change of the level difference; that is, the faster the rate of change, the greater the pre-applied compensation adjustment force, aiming to counteract the current deteriorating trend.

[0068] By introducing feedforward compensation control based on the rate of change of liquid level difference, the system can "predict" the development direction of liquid level imbalance and intervene in advance to adjust before the liquid level difference deviates significantly from the target value. This control method effectively shortens the system response time, suppresses liquid level fluctuations, further maintains the dynamic stability of static pressure at the liquid supply manifold, avoids large-scale reciprocating oscillations of the valve caused by system lag, and improves the pressure control accuracy and system stability during the plastic pipe testing process.

[0069] Furthermore, step S4 also includes: The return water temperature and back pressure value of each water tank 11 are obtained in real time. Abnormal operating conditions are identified based on the liquid level value, the liquid level difference, the rate of change of the liquid level difference, the return water temperature, and the back pressure value. Implement the graded response strategy corresponding to the abnormal operating condition.

[0070] Furthermore, the abnormal operating conditions include: During the test, the water level will gradually decrease due to minor leaks in the pipeline, venting, or thermal expansion and contraction of the system. When the liquid level in any of the water tanks 11 falls below a first preset liquid level threshold, it is determined to be a low liquid level anomaly, and a water replenishment response is executed to automatically inject water into the water tank 11 to protect the centrifugal pump 31.

[0071] Heating can cause water volume expansion, or the water supply valve may malfunction and remain open. When the liquid level in any of the water tanks 11 exceeds the second preset liquid level threshold, it means that the buffer space (gas phase space) at the top of the water tank 11 used to contain gas back pressure is excessively compressed, which will cause violent fluctuations in system back pressure or even liquid overflow. At this time, it is determined to be a high liquid level anomaly, and a stop water supply response is executed, forcibly closing the water supply valve to restore the gas phase space.

[0072] When the liquid level difference between any one of the water tanks 11 and the others shows a continuous increasing trend in one direction, it indicates that the water loss rate of that specific water tank 11 is faster than that of the other water tanks 11, ruling out common problems in the main pipe and belonging to a "point-to-point" difference. Furthermore, if the absolute value of the rate of change of the liquid level difference is less than a first preset rate threshold, it indicates that the leakage rate is slow and not a gushing leak. Simultaneously, when the back pressure value of the water tank 11 is within a preset pressure fluctuation range, it indicates that the leakage rate has not exceeded the gas supply system's replenishment capacity, and the gas supply can replenish the pressure in real time, so the back pressure does not drop significantly. This is determined to be a micro-leakage condition, and the system still has the conditions to maintain the test, executing a water replenishment response; by replenishing water, the liquid level balance is maintained, so that data can be recorded or the test continuity can be maintained without interrupting the test.

[0073] When the liquid level difference between any one of the water tanks 11 and the others increases, and the absolute value of the rate of change of the liquid level difference is greater than a second preset rate threshold, while the back pressure value of the water tank 11 is lower than a preset pressure threshold, it indicates that the plastic tube sample 7 has ruptured instantaneously, and a large amount of high-pressure liquid is ejected in a very short time. Due to the huge leakage at the rupture point, far exceeding the gas supply rate of the gas source regulating valve, the pressure in the gas phase space drops sharply. At this time, it is determined to be a tube rupture condition, and an isolation response is executed. The electric valve 12 of the branch is immediately closed to physically isolate the faulty circuit to prevent the collapse of the main pipe pressure from affecting other test circuits and to avoid injury from high-pressure liquid splashing.

[0074] When the liquid levels of each water tank 11 fluctuate synchronously and the absolute value of the rate of change of each liquid level difference is less than the third preset rate threshold, and the back pressure values ​​of each water tank 11 exceed the preset pressure fluctuation range, it indicates that the inlet and outlet water of each water tank 11 is balanced, the fluctuation is relatively gentle, and the disturbance originates from the common air supply system (such as the loading and unloading fluctuation of the air compressor 21 or the vibration of the pressure reducing valve 22), rather than a fault in the water tank 11 or pipeline. At this time, it is determined to be an air supply fluctuation condition, and a back pressure adjustment response is executed. The control system temporarily ignores the liquid level fluctuation to avoid valve misadjustment, and instead actively adjusts the state of the pressure reducing valve 22 on the air intake manifold or the air compressor 21. After the air supply stabilizes, the liquid level naturally returns to a stable state.

[0075] When the liquid level of any of the water tanks 11 is higher than the third preset liquid level threshold for a preset time, and the return water temperature of the water tank 11 remains lower than the preset temperature threshold, while the back pressure of the water tank 11 is within the preset pressure fluctuation range, it indicates that the water replenishment system has responded to the liquid level drop signal and continues to replenish water, causing the water tank 11 to be replenished to a high liquid level. Simultaneously, the return water temperature remaining lower than the preset temperature threshold indicates that hot water has failed to return, and the water accumulated in the pipeline gradually cools. Furthermore, the back pressure value being within the preset pressure fluctuation range eliminates flow changes caused by abnormal pressure. This set of characteristic parameters (high liquid level + low temperature + normal pressure) precisely indicates that a physical blockage (such as pipe kinking or valve jamming) has occurred in the test pipeline or return water pipeline. At this time, it is determined to be a pipeline blockage condition, an alarm response is executed, and the operator is notified to check whether there is a blockage in the pipeline after the pump and the sample section.

[0076] Example 4

[0077] In this embodiment, considering that the pressure resistance test of plastic pipes is usually carried out in a high-temperature and high-pressure environment, the circulating medium (aqueous solution) is in a high-temperature state, and its physical properties are extremely sensitive to cavitation. Specifically, as the temperature of the aqueous solution increases, its saturated vapor pressure increases significantly, causing the water to easily vaporize and form bubbles at the suction inlet of the centrifugal pump 31 due to the pressure drop. When these bubbles enter the high-pressure zone inside the pump with the fluid, they will quickly collapse and generate high-frequency impacts, causing pitting or even perforation on the impeller surface, i.e., severe cavitation damage. In addition, since the test circuit usually maintains a high back pressure, the centrifugal pump 31 needs to overcome a large system resistance to do work. If the suction inlet pressure supply is insufficient, it will further aggravate the risk of cavitation.

[0078] Based on the above background, Embodiment 4 of this application provides a testing method for plastic pipes based on parallel liquid supply from multiple water tanks 11, which differs from Embodiment 2 or Embodiment 3 in that: refer to Figure 1 Step S4 includes: The real-time suction pressure of the liquid supply manifold and the real-time temperature of the aqueous solution are obtained, and the real-time net positive suction head (NPSH) of the centrifugal pump 31 is calculated accordingly. To obtain the required net positive suction head (NPSH) of the centrifugal pump 31; When the real-time effective net positive suction head (NPSH) is greater than the sum of the required NPSH and the preset safety margin, the liquid level balance control mode is executed, and the opening degree of the corresponding electric valve 12 is adjusted according to the liquid level difference between each of the water tanks 11. When the real-time effective net positive suction head (NPSH) is less than or equal to the sum of the required NPSH and the preset safety margin, the system switches to pump protection control mode, locks or increases the opening of the electric valve 12 corresponding to the water tank 11 with the highest current liquid level, until the real-time effective NPSH recovers to a level greater than the sum of the required NPSH and the preset safety margin.

[0079] Specifically, the control system acquires the real-time suction pressure within the manifold through a suction pressure sensor installed on the supply manifold, and obtains the real-time temperature of the aqueous solution through a temperature sensor. Combining preset local atmospheric pressure and fluid property parameters, the control system calculates the current real-time effective net positive suction head (NPSH) of the centrifugal pump 31 using the NPSH formula. Simultaneously, the system retrieves the pre-stored performance curves of the centrifugal pump 31 from its memory and reads the corresponding required NPSH based on the current flow rate. (The required NPSH is an inherent characteristic of the centrifugal pump 31, determined experimentally by the manufacturer, and typically varies with flow rate. In the control system, it is obtained by directly querying pre-stored pump performance curve data or fitting formulas based on the pump's current real-time operating flow rate.) The control system compares the real-time effective net positive suction head (NPSH) with (the sum of the required NPSH and the preset safety margin) in real time to execute the corresponding control mode: Liquid level balance control mode: When the real-time effective net positive suction head (NPSH) is greater than the sum of the required NPSH and the preset safety margin, the centrifugal pump 31 is determined to be in a safe operating range with no risk of cavitation. At this time, the control system executes the liquid level balance control strategy described in Example 2 or Example 3, that is, it adjusts the opening of the electric valve 12 according to the liquid level difference and rate of change between each water tank 11 to maintain the liquid level of each water tank 11 being consistent.

[0080] Pump protection control mode: When the real-time effective net positive suction head (NPSH) is less than or equal to the sum of the required NPSH and the preset safety margin, it is determined that the centrifugal pump 31 is approaching the cavitation critical point and there is a risk of cavitation damage. At this time, the control system immediately suspends the liquid level balance adjustment and switches to the pump protection control mode.

[0081] The system automatically identifies the tank with the highest liquid level among all tanks 11 (i.e., the tank 11 contributing the most hydrostatic head) and locks or further increases the opening of the electric valve 12 corresponding to that tank 11. The logic is as follows: when the effective net positive suction head (NPSH) approaches the safety threshold, it indicates insufficient pressure in the supply manifold. The tank 11 with the highest liquid level has the greatest potential energy due to its highest liquid surface, enabling it to provide the greatest hydrostatic pressure compensation to the manifold. By prioritizing the activation of this high-level tank 11, its high potential energy can be utilized to rapidly increase the pump inlet pressure with minimal flow resistance, thereby forcibly increasing the real-time effective NPSH.

[0082] The system will maintain this state until the real-time effective net positive suction head (NPSH) recovers to a level greater than the sum of the required NPSH and the preset safety margin, ensuring that the centrifugal pump 31 always operates within the safety margin. This method utilizes the liquid level difference advantage of multiple water tanks 11 connected in parallel to effectively solve the technical problem of cavitation damage to the centrifugal pump 31 under high temperature and high pressure environments, ensuring the long-term stable operation of the testing equipment and the accuracy of the test data.

[0083] Furthermore, the preset safety margin is dynamically determined based on the real-time temperature of the aqueous solution; the dynamic safety margin is positively correlated with the real-time temperature.

[0084] Furthermore, the electrical operating parameters of the centrifugal pump 31 are obtained, including at least one of real-time current value and real-time power value; The electrical operating parameters are compared with the standard parameter values ​​under the current operating conditions; When the decrease in the electrical operating parameters relative to the standard parameter values ​​exceeds a preset deviation threshold, it is determined to be a precursor to cavitation, and the pump protection control mode is forcibly entered.

[0085] Specifically, the control system collects real-time operating data of the motor driving the centrifugal pump 31 through a frequency converter or power meter, obtaining real-time current and power values. Based on the current operating conditions of the centrifugal pump 31 (such as real-time flow rate or speed), the system queries the pre-stored pump standard performance curve to obtain the corresponding theoretical standard current and standard power values ​​under that operating condition as a comparison benchmark.

[0086] When cavitation precursors occur, the vaporization of the liquid inside the pump leads to a decrease in fluid density and a deviation in the pump's head / flow characteristics, manifested as an abnormal drop in motor output shaft power and load current. The system compares the real-time electrical operating parameters with standard parameter values ​​and calculates the deviation rate. When the decrease in real-time current or real-time power exceeds a preset deviation threshold (e.g., a decrease exceeding 5%), it is determined that cavitation precursors have occurred. At this time, to prevent actual cavitation from damaging the pump body, the system will no longer wait for feedback from liquid level or pressure calculations, but will directly force entry into the pump protection control mode, prioritizing locking or increasing the opening of the electric valve 12 of the high-level water tank 11 to quickly increase the pump inlet pressure and eliminate the cavitation hazard.

[0087] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A testing method for plastic pipes based on parallel liquid supply from multiple water tanks, characterized in that, include: S1 starts the centrifugal pump to establish a circulation loop supplied by multiple parallel water tanks; wherein, the aqueous solution in each water tank is respectively connected to the same supply manifold through the corresponding electric valve and check valve, and is transported to each test loop group by the centrifugal pump, and then flows back to the corresponding water tank; the volume of the water tank is less than the preset volume threshold. S2 applies gas back pressure to each of the water tanks to the target pressure; S3 heats each of the water tanks to the target temperature under the target pressure, and maintains the target pressure and the target temperature to test the plastic tube sample; During the test, S4 acquires the liquid level value of each water tank in real time, calculates the liquid level difference between each water tank, and adjusts the opening degree of the electric valve corresponding to each water tank according to the liquid level difference, so that the liquid level difference between each water tank is less than a preset threshold.

2. The testing method for plastic pipes based on parallel liquid supply from multiple water tanks according to claim 1, characterized in that, Step S4 further includes: Calculate the rate of change of liquid level difference between each of the water tanks; Feedforward compensation control is applied to the corresponding electric valve based on the liquid level difference and the rate of change of the liquid level difference.

3. The testing method for plastic pipes based on parallel liquid supply from multiple water tanks according to claim 2, characterized in that, Step S4 further includes: The return water temperature and back pressure value of each water tank are obtained in real time. Abnormal operating conditions are identified based on the liquid level value, the liquid level difference, the rate of change of the liquid level difference, the return water temperature, and the back pressure value. Implement the graded response strategy corresponding to the abnormal operating condition.

4. The testing method for plastic pipes based on parallel liquid supply from multiple water tanks according to claim 3, characterized in that, The abnormal operating conditions include: When the liquid level in any of the water tanks is lower than the first preset liquid level threshold, it is determined to be a low liquid level anomaly, and a water replenishment response is executed. When the liquid level value of any of the water tanks is higher than the second preset liquid level threshold, it is determined to be a high liquid level abnormality, and a stop water replenishment response is executed; When the liquid level difference between any of the water tanks and the other water tanks continues to increase in one direction, and the absolute value of the rate of change of the liquid level difference is less than a first preset rate threshold, and the back pressure value of the water tank is within a preset pressure fluctuation range, it is determined to be a micro-leakage condition, and a water replenishment response is executed. When the liquid level difference between any of the water tanks and the other water tanks increases, and the absolute value of the rate of change of the liquid level difference is greater than the second preset rate threshold, while the back pressure value of the water tank is lower than the preset pressure threshold, it is determined to be a pipe burst condition, and an isolation response is executed. When the liquid level values ​​of each water tank fluctuate synchronously and the absolute value of the rate of change of each liquid level difference is less than the third preset rate threshold, and the back pressure value of each water tank exceeds the preset pressure fluctuation range, it is determined to be a gas source fluctuation condition, and a back pressure adjustment response is executed. When the liquid level of any of the water tanks is higher than the third preset liquid level threshold for a preset time, and the return water temperature of the water tank is continuously lower than the preset temperature threshold, while the back pressure of the water tank is within the preset pressure fluctuation range, it is determined to be a pipeline blockage condition, and an alarm response is executed.

5. The testing method for plastic pipes based on parallel liquid supply from multiple water tanks according to claim 1, characterized in that, Step S4 includes: The real-time suction pressure of the liquid supply manifold and the real-time temperature of the aqueous solution are obtained, and the real-time net positive suction head (NPSH) of the centrifugal pump is calculated accordingly. Obtain the required net positive suction head (NPSH) for the centrifugal pump; When the real-time effective net positive suction head (NPSH) is greater than the sum of the required NPSH and the preset safety margin, the liquid level balance control mode is executed, and the opening degree of the corresponding electric valve is adjusted according to the liquid level difference between each water tank. When the real-time effective net positive suction head (NPSH) is less than or equal to the sum of the required NPSH and the preset safety margin, the system switches to pump protection control mode, locks or increases the opening of the electric valve corresponding to the tank with the highest current liquid level, until the real-time effective NPSH recovers to a level greater than the sum of the required NPSH and the preset safety margin.

6. The testing method for plastic pipes based on parallel liquid supply from multiple water tanks according to claim 5, characterized in that, Obtain the electrical operating parameters of the centrifugal pump, wherein the electrical operating parameters include at least one of real-time current value and real-time power value; The electrical operating parameters are compared with the standard parameter values ​​under the current operating conditions; When the decrease in the electrical operating parameters relative to the standard parameter values ​​exceeds a preset deviation threshold, it is determined to be a precursor to cavitation, and the pump protection control mode is forcibly entered.

7. The testing method for plastic pipes based on parallel liquid supply from multiple water tanks according to claim 1, characterized in that, The preset volume threshold is 29 L; The target temperature is 95℃, 105℃, or 115℃.

8. A plastic pipe testing system based on parallel liquid supply from multiple water tanks, used to perform the testing method according to any one of claims 1-7, characterized in that, include: Multiple parallel liquid supply modules are provided, each of which includes a water tank, an electric valve, and a check valve; the volume of the water tank is less than a preset volume threshold; the outlet of the water tank is connected to the same liquid supply manifold via the electric valve and the check valve in sequence; each water tank is equipped with a heating component and a liquid level detector. A back pressure assembly is connected to each of the water tanks and is used to apply gas back pressure to each of the water tanks. The test module includes a centrifugal pump, a test liquid supply manifold, and multiple test circuit groups; the suction port of the centrifugal pump is connected to the liquid supply manifold, and the discharge port of the centrifugal pump is connected to the test liquid supply manifold; the inlet of each test circuit group is connected to the test liquid supply manifold, and the outlet is connected to the corresponding water tank. The control system is connected to each of the liquid level detectors and each of the electric valves via signal connections. The control system is configured to: acquire the real-time liquid level value detected by each of the liquid level detectors, calculate the liquid level difference between each of the water tanks, and adjust the opening degree of the corresponding electric valve according to the liquid level difference, so that the liquid level difference between each of the water tanks is less than a preset threshold.

9. The plastic pipe testing system based on parallel liquid supply from multiple water tanks according to claim 8, characterized in that, Also includes: A dosing device, connected to one of the water tanks, is used to add chemicals to the water tank.

10. The plastic pipe testing system based on parallel liquid supply from multiple water tanks according to claim 8, characterized in that, Each of the test circuit groups includes multiple test sub-circuits, and each test sub-circuit is provided with a pressure regulating valve, a first pressure gauge, a first switching valve, a second switching valve and a flow regulating valve in sequence from the water inlet end to the water outlet end; The system also includes a test chamber and a leak detection device. The pipeline between the first switching valve and the second switching valve extends through the test chamber. At least one of the plastic tube samples is connected in series on the pipeline section of the test sub-circuit located inside the test chamber. The leak detection device is located inside the test chamber.

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