Damp heat-oxygen-internal pressure-load coupled nonmetal pipeline aging device and life evaluation method

Abstract

The invention provides a damp heat-oxygen-internal pressure-load coupled non-metal pipeline aging device and a method capable of evaluating the service life of an in-service non-metal pipeline. The non-metal pipeline aging device comprises six parts, namely an inner cavity, a box body temperature control system, a box body humidity control system, a pipeline internal pressure control system, a pipeline external load loading device and an air supply circulating system, and an accelerated aging test of a non-metal pipeline under different working condition combinations of four factors, namely damp heat, oxygen, internal pressure and load can be carried out by virtue of the aging device. Measuring oxidation induction periods before and after aging of the in-service non-metal pipeline and the non-metal pipeline with the same mark through a differential heat scanning method, substituting the oxidation induction periods into a non-metal pipeline aging life prediction formula coupled with damp heat-oxygen-internal pressure-load factors, and calculating to obtain the service aging life. According to the method, damp heat-oxygen-internal pressure-external load multi-factor coupling is realized, so that an actual service environment is accurately simulated, and comprehensive technical support can be provided for safe operation of the non-metal pipeline.

Description

Technical Field

[0001] This invention relates to an aging device and life evaluation method for non-metallic pipes, and particularly to a coupled aging device and life evaluation method that couples humidity-heat-oxygen-internal pressure-load. Background Technology

[0002] The widespread installation and long-term use of non-metallic pipelines have led to increasingly prominent safety issues. Furthermore, many non-metallic pipelines in my country have entered the middle to late stages of their service life, making performance evaluation imperative. Failure of non-metallic pipelines mainly involves processes such as material aging and stress crack propagation. Currently, aging devices on the pipe market have relatively limited functions, only able to simulate certain aging conditions (such as thermo-oxidative aging, ultraviolet aging, damp heat aging, etc.). While some aging devices can simulate pipeline pressure testing, they still cannot reflect complex coupled operating conditions.

[0003] Moreover, current methods for evaluating the aging life of non-metallic pipelines mainly consider single conditions such as pressure and heat and oxygen, and fail to comprehensively consider complex working conditions such as environmental stress coupling of damp heat, oxygen, internal pressure and external load. Therefore, there is a lack of methods for evaluating the aging life of non-metallic pipelines under complex working conditions. Summary of the Invention

[0004] The purpose of this invention is to address the aforementioned deficiencies of existing aging devices by providing an aging device capable of handling complex coupled operating conditions. This device has the advantages of simultaneously simulating operating conditions such as load, air pressure, temperature, and humidity, all of which are programmable and controllable. After aging, the device can evaluate the aging life of non-metallic pipelines under complex operating conditions under the coupled four environmental factors of humidity, heat, oxygen, internal pressure, and external load, based on the aging operating conditions and aging load.

[0005] The technical solution is as follows: the entire unit is a highly integrated aging chamber; the upper front of the chamber is an inner cavity, which is divided into several workstations. Each workstation is designed with a stainless steel clamping device with fine holes, a rubber ring sealing plug, and a sealed stainless steel pressure plug. Temperature and humidity sensors are also installed inside the inner wall; the front of the chamber is connected to a programmable controller that can adjust humidity and temperature; the lower front of the chamber is a water supply pipeline, which can realize water cooling and water tank replenishment operations; the lower rear of the chamber is a water tank, a refrigeration compressor, and an evaporator for humidification; the middle of the rear of the chamber is an air-cooled condenser, which is mainly used to regulate and control the high temperature and low humidity operation and the control of alternating temperature and humidity loads; the upper rear of the chamber is a blower and a centrifugal fan for air circulation; the pressurization end of the workstation in the inner cavity of the chamber is connected to an air compressor with a PLC controller for circulating control of the internal pressure of the pipeline; the water tank of the chamber is connected to a drain pipe for water replenishment.

[0006] The aforementioned temperature control system mainly consists of a temperature sensor, an inner cavity, a high-strength PU foam and high-density glass fiber insulation layer, a high-tensile sealing strip, a blower (hot air circulation), a centrifugal fan, a nickel-chromium rapid heating wire, and a microcomputer. The nickel-chromium rapid heating wire heats up quickly, and the hot air circulation heating method evenly distributes the temperature. The temperature is then measured by the temperature sensor. The temperature control output power is calculated by the microcomputer, which automatically controls the heating power according to the internal load. The insulation layer and sealing ensure constant temperature control.

[0007] The humidity control system described above mainly consists of a humidity sensor, a blower (humidity circulation), an inner cavity, a water tank, a refrigeration compressor, an evaporator, an air-cooled condenser, and a microcomputer. The evaporator uses an electronic parallel positioning method for micro-humidification and superheating. A fan blows humidity into the cavity, and a humidity sensor measures the humidity. The refrigeration compressor and condenser control dehumidification to ensure stable humidity. When water is insufficient, water can be automatically replenished to the water tank through the water circuit.

[0008] The aforementioned pressure control and external load control system mainly consists of a stainless steel porous pipe wall clamp, a stainless steel plug, a pressurizing plug, an air compressor, and a PLC control system. After the wiring is connected, the air compressor pressurizes the pipe. Once the internal air pressure stabilizes, the pressurization stops. The PLC control system can set the cyclic internal pressure load. The stainless steel clamp is mainly used to control the external load clamping force.

[0009] This invention relates to a method for predicting the service life of in-service non-metallic pipelines under various environmental load couplings, and is carried out according to the following steps:

[0010] The oxidation induction period (a) of in-service non-metallic pipelines was tested using the differential thermal scanning method. 工况 (Unit: min);

[0011] Obtain operating condition data for in-service non-metallic pipelines, including: service temperature T. 工况 (Unit: K), Relative Humidity %RH 工况 (Unit: %), Pipeline internal pressure P gas工况 (Unit: MPa), External stress S 工况 (Unit: MPa);

[0012] Pipes of the same grade as those in service non-metallic pipes were selected for aging tests, forming the test group, and the following aging tests were conducted:

[0013] The oxidation induction period a0 (unit: min) of the non-metallic pipe before aging was obtained again using the differential thermal scanning method.

[0014] The non-metallic pipe sample section of this grade was placed into the aforementioned aging device, and coupled environmental loads were applied simultaneously: the temperature T (unit: K) was set through the chamber temperature control system; the relative humidity %RH (unit: %) was set through the chamber humidity control system; and the internal pressure P of the pipe was set through the internal pressure control system. gas (Unit: MPa); Set the mechanical stress S (unit: MPa) using an external loading device; Start the air circulation system to maintain a constant oxygen environment; Measure the oxidation induction period a of the sample after aging. end (Unit: min); Set the baseline parameters for the test apparatus: calibrated pressure P f Determined based on pipe diameter;

[0015] Coefficients were obtained using the least squares method: Variable temperature experiment: %RH, P were fixed. gas S, within the set temperature range, sets n temperature gradients, based on n corresponding time t. n Fitting the temperature coefficient B; obtaining the coefficient through gradient experiments: constant temperature and humidity experiment: fixed T, P gas S, within the set humidity range RH, several humidity gradients are used to fit the humidity coefficient B. h ; Variable pressure test: With fixed T, %RH, and S, several pressure gradients are applied at the set pressure to fit the pressure coefficients C and D; Variable load test: With fixed T, %RH, and P gas Several stress gradients are fitted to the stress coefficient E at the set pressure; based on multiple sets of differential scanning calorimetry (a end The aging rate constant A is determined by nonlinear regression based on the t) data.

[0016] During the oxidation induction period a end During the testing process, in order to reduce the fitting error, multiple tests were conducted for parameter fitting. When calculating the service life, the average value of the oxidation induction period after the test was used as the calculation parameter 'a'. end ;

[0017] The aging performance relationship of this grade of non-metallic pipe was obtained:

[0018]

[0019] a0 and a end These are the oxidation induction periods before and after aging for this grade of non-metallic pipe;

[0020] t is the predicted lifespan of the non-metallic pipe;

[0021] E a It is activation energy;

[0022] R is the molar gas constant;

[0023] T is the absolute temperature of aging;

[0024] P gas It is the internal pressure of a non-metallic pipe, P f It is the laboratory calibration pressure;

[0025] B h It is the Arrhenius humidity parameter;

[0026] S is the applied external mechanical stress;

[0027] The error term F(P) is determined using the above formula. gas ,%RH,S);

[0028] Finally, the service life t of the in-service non-metallic pipeline was calculated. 工况 for:

[0029]

[0030] In summary, the beneficial effects of this invention are as follows:

[0031] The accelerated aging state of non-metallic pipelines under complex coupled working conditions was simulated by adjusting different loads.

[0032] To achieve circulating pressure changes during gas transportation via pipeline;

[0033] To achieve coupled accelerated aging conditions under different environmental loads such as high temperature and low humidity, high temperature and medium humidity, and high temperature and high humidity;

[0034] The components are highly integrated, resulting in significant energy savings and improved control performance;

[0035] The aforementioned aging device and life prediction model, which couples four environmental factors—humidity, heat, oxygen, internal pressure, and external load—can accurately simulate various complex combinations of working conditions during pipeline aging. This overcomes the limitations of traditional equipment that can only simulate one or two influencing factors. A special fixture design ensures uniform distribution of external load stress on the pipe wall, avoiding data distortion caused by localized stress concentration. Furthermore, it quantifies the humidity-stress coupling effect for the first time, providing a more accurate basis for pipeline life prediction. This invention empowers fields such as intelligent monitoring systems and pipeline design, and provides strong support for the safe operation of infrastructure such as non-metallic pipe networks. Attached Figure Description

[0036] Appendix Figure 1This is an overall schematic diagram of the present invention. In the diagram: 1. Air compressor; 2. PLC controller; 3. Air supply pipeline; 4.1. Solenoid valve; 4.2. Solenoid valve (vent); 4.3. Solenoid valve (supply); 4.4. Valve and water source; 5. Water supply pipeline; 6. Clamping device; 7. Water tank; 8. Evaporator; 9. Condenser; 10. Refrigeration compressor; 11. Centrifugal fan; 12. Blower; 13.1. Internal return air pipeline; 13.2. Internal supply air pipeline; 14. Integrated control panel; 15. Inner cavity; 16. Nickel-chromium rapid heating wire; 17. Microcomputer.

[0037] Appendix Figure 2 This is a schematic diagram of the internal cavity. In the diagram: temperature sensor 15.1, humidity sensor 15.2, insulation layer 15.3, air nozzle 15.4, clip 15.5, porous shelf 15.6, top air outlet 15.7, and light fixture 15.8.

[0038] Appendix Figure 3 This is a schematic diagram of a pipe sample. In the diagram: rubber sealing gasket 18, compression ring 19, plug 20, pressurizing plug 21, gas filling pipe 22, porous pipe wall clamp 23, pipe sample 24, adjusting bolt 25, clamp adjusting bolt 26.

[0039] Appendix Figure 4 This is a flowchart of a method for evaluating the aging life of non-metallic pipelines that couples humidity, heat, oxygen, internal pressure, and load. Detailed Implementation

[0040] Combined with appendix Figure 1 Appendix Figure 2 Appendix Figure 3 and attached Figure 4 The non-metallic pipe aging device and life evaluation method described herein are further illustrated in the following specific embodiments:

[0041] The non-metallic pipe aging device coupling humidity-heat-oxygen-internal pressure-load is a highly integrated aging chamber. The upper front of the chamber contains an inner cavity 15, divided into several workstations. Each workstation is equipped with a rubber sealing gasket 18, a clamping ring 19, a plug 20, a pressurizing plug 21, a gas filling line 22, and a porous pipe wall clamp 23. The inner cavity 15 also houses a temperature sensor 15.1, a humidity sensor 15.2, an insulation layer 15.3, a gas filling nozzle 15.4, a clip 15.5, and a porous shelf 15.6. The front of the chamber is also connected to... The integrated control panel 14 and microcomputer 17 are combined to form a programmable controller for adjusting humidity and temperature; the lower front of the cabinet has a water supply pipe 5 and a water tank 7; the lower rear of the cabinet has an evaporator 8 and a refrigeration compressor 10 for humidification; the middle of the rear of the cabinet has a condenser 9, which is mainly used to adjust and control the high temperature and low humidity operation and the alternating temperature and humidity load; the upper rear of the cabinet has a centrifugal fan 11 and a blower 12 for air circulation; the pressurized end of the cabinet's internal cavity is connected to an air compressor 1 and a PLC controller 2 for circulating control of the internal pressure of the pipeline.

[0042] The aforementioned temperature control system mainly consists of a centrifugal fan 11, a blower 12 (hot air circulation), an inner cavity 15, a temperature sensor 15.1, an insulation layer 15.3 (made of high-strength PU foam and high-density glass fiber cotton, equipped with a high-tensile sealing strip), a nickel-chromium rapid heating wire 16, and a microcomputer 19. The nickel-chromium rapid heating wire 16 rapidly heats up the temperature, and the blower 12 distributes the temperature evenly through heating. The temperature sensor 15.1 measures the temperature, and the temperature control output power is calculated by the microcomputer 19, which automatically controls the heating power according to the load. The insulation layer 15.3 ensures constant temperature control.

[0043] The humidity control system described above mainly consists of a water tank 7, a condenser 9, an evaporator 8, a refrigeration compressor 10, a blower 12 (humidity circulation), a humidity sensor 15.2, an inner cavity 15, and a microcomputer 17. The evaporator uses an electronic parallel positioning method for micro-humidification and superheating. The blower 12 blows the humidifier into the cavity, and the humidity sensor 15.2 measures the humidity. The condenser 9 and the refrigeration compressor 13 control dehumidification to ensure stable humidity. When water is insufficient, water can be automatically replenished to the water tank through the water source, valve 4.4, and water supply pipeline 5.

[0044] The aforementioned pressure control and external load control system mainly consists of an air compressor 1, a PLC controller 2, an air supply pipeline 3, solenoid valves 4.1-4.3, a plug 20, a pressurizing plug 21, an air supply line 22, and a porous pipe wall clamp 23. After the circuit is connected, the air compressor 1 pressurizes the system. Once the internal air pressure stabilizes, the pressurization stops. The PLC 2 control system can set the cyclic internal pressure load. The porous pipe wall clamp 23 is mainly used to control the external load clamping force.

[0045] Depend on Figure 1It is understood that the present invention provides a non-metallic pipeline aging test platform that couples humidity, heat, oxygen, internal pressure, and load, characterized in that:

[0046] like Figure 1 As shown in the pipeline pressure control system, air compressor 1 is controlled by PLC controller 2, which controls its start and stop. PLC controller 2 is connected to solenoid valve 4.1 via a cable and monitors real-time pressure data in the pipeline system using a built-in pressure sensor. It is also connected to pressure-increasing solenoid valve 4.3 and pressure-reducing solenoid valve 4.2 via cables to complete gas delivery and control the pressurization and depressurization actions of the two solenoid valves. When the pipeline pressure drops significantly, PLC controller 2 automatically shuts down and issues an alarm. Manual operation is required for the platform to resume operation. In addition, PLC controller 2 is connected to air compressor 1 via a cable and requires a three-phase AC power supply.

[0047] like Figure 1 As shown, the coupling aging device mainly consists of a water supply pipeline 5, a clamping device 6, a pressure plug 7, a plug 8, a water tank 7, an evaporator 8, a condenser 9, a refrigeration compressor 10, a centrifugal fan 11, a blower 12, an internal return air pipeline 13.1, an internal supply air pipeline 13.2, an integrated control panel 14, an inner cavity 15, a temperature sensor 15.1, a humidity sensor 15.2, an insulation layer 15.3, an air nozzle 17.4, a buckle 17.5, a porous shelf 15.6, a nickel-chromium rapid heating wire 16, and a microcomputer 17. Additionally, high-strength PU foam and high-density glass fiber cotton insulation material 17.3 is added inside the outer shell surrounding the inner cavity 15. Figure 1 As shown in the schematic diagram of the inner cavity indicated by the blue arrow, when the non-metallic pipe is placed into the inner cavity 17, the evaporator 8, condenser 9, refrigeration compressor 10, centrifugal fan 13, blower 12, nickel-chromium rapid heating wire 16, and microcomputer 17 are started. At this time, fresh air enters the oven from the air supply duct 15.2, and circulates counterclockwise through the nickel-chromium rapid heating wire 16, evaporator 8, condenser 9, refrigeration compressor 10, centrifugal fan 11, and blower 12, and then enters the inner cavity 15 through the top air supply port 15. Some of the gas is discharged through the internal return air duct 13.1, and the remaining gas continues to enter the heating cycle. Throughout the process, the temperature sensor 15.1 and humidity sensor 15.2 collect temperature and humidity signals at all times and feed them back to the microcomputer 17, which can be monitored and controlled through the integrated control panel 14. The arrangement of the nine external holes on the right side of the inner cavity allows each external hole to hold one non-metallic pipe sample, and a maximum of nine sets of non-metallic pipes can be accommodated simultaneously for coupled aging tests.

[0048] Depend on Figure 2It is known that there are 9 workstations in the inner cavity 15, and each workstation has a buckle 15.5 near the bottom of the shelf. The pipe sample 24 is a non-metallic pipe, cut into a small section with a length of about 80cm. One end of the pipe is sealed by a rubber sealing gasket 18, a compression ring 19, a plug seal 22 and an adjusting bolt 25, and the other end is sealed by a rubber sealing gasket 18, a compression ring 19, a pressure plug seal 22 and an adjusting bolt 25. Connect the pressure end of the pipe sample 24 to the buckle 15.5, and tighten the air nozzle 15.4 on the outside of the box to start applying internal pressure. Place the porous pipe wall clamp 23 tightly against the outer end of the pipe sample 24, and adjust the bolt 26 to achieve external load clamping.

[0049] Depend on Figure 3 It is known that the pipe sample 24 is installed between the plug 20 and the pressurizing plug 21 by the pre-tightening force provided by the adjusting bolt 25, the sealing gasket 18 and the compression ring 19, and is connected to the gas nozzle 15.4 through the gas filling line 22; the plugs at both ends of the pipe sample 24 are placed on the porous plate 15.6, the internal pressure is added from the right, and the external load is provided by the porous pipe wall clamp 23 and the clamp adjusting bolt 26; the porous plate 15.6 is used to prevent the pipe sample from moving in the inner cavity 15; the buckle 15.5 can facilitate the disassembly and installation of the pipe sample.

[0050] The following are descriptions of some steps and precautions regarding aging tests.

[0051] The aging test first requires sample preparation and grouping: Select 24 representative non-metallic pipe samples, ensuring that their brand, batch and other parameters are consistent, and use non-contamination tools to cut or prepare the samples to the required size for the workstation; randomly divide the samples into at least three groups: aging test group 1, aging test group 2 and non-aging control group, and the number of samples in each group must meet the statistical requirements; permanently mark the test group samples; after each aging test, store them in a pollution-free, room temperature and low humidity environment.

[0052] Adjust the aging chamber according to the test requirements: First, install the porous pipe wall clamp 23 on the outer surface of the pipe sample 24 and place it on the porous shelf 15.6; second, install the internal pressure loading equipment and place the pipe sample 24 into the inner cavity 15, check that the air nozzle 15.4 and the buckle 15.5 are installed correctly, and ensure that the pipe sample 24 is fixed; then turn on the air compressor 1 and PLC controller 2 to check for air leakage and pressure fluctuations; after checking that everything is correct, close the inner cavity 15; finally, set the humidity load and temperature load on the integrated control panel 14 according to the test requirements, and start the aging test timing when the load stabilizes.

[0053] The aging temperature of non-metallic pipes should be below the melting point of 30℃. If it exceeds this temperature, it will affect the subsequent assessment and prediction of aging. The internal pressure during aging is generally controlled between 0.4 and 0.8 MPa, and the aging time is generally selected to be more than one month. Otherwise, the aging effect will not be significant. Before the experiment, a graded evaluation system for the aging degree of non-metallic pipes should be established in advance so as to determine the evolution of the aging level under different set time through multiple sets of comparative tests. In addition to temperature, humidity, pressure and load, the aging cycle of non-metallic pipes of different materials, the influence of pipe diameter differences on aging, the aging law of non-metallic pipes with defects, and the changing trend of slow crack propagation with aging time can all be included in the research scope.

[0054] The constant temperature and humidity test process only requires setting the target temperature and humidity values ​​on the integrated control panel 14; the alternating temperature and humidity load can be directly controlled by inputting function equations through the integrated control panel 14; the temperature and humidity adjustment power can be controlled by setting the T signal through the integrated control panel 14; the temperature and humidity range can also be monitored in real time through the integrated control panel 14.

[0055] The constant internal pressure loading process requires opening the valve of air compressor 1 and connecting the air compressor's air supply pipe to the air inlet 15.4 next to the inner cavity, so that the output pressure is slightly higher than the upper limit of the pressure required for the experiment; start PLC controller 2 and monitor the constant pressure data in real time after the pressure stabilizes; when the detected pressure is lower than the set value, PLC controller 2 energizes the boost solenoid valve 4.1 to drive the internal pressure of the pipeline to increase; after the pressure reaches the preset value, PLC controller 2 automatically shuts off the boost solenoid valve; the cycle internal pressure setting requires completing the air compressor startup and pre-pressure adjustment according to the previous steps, starting PLC controller 2 and setting the boost amplitude and cycle period; the pressure should rise to the peak value, automatically close the valve after reaching the limit, and open the pressure reduction solenoid valve 4.3 to release the pressure after the peak pressure is maintained for the set time; when the pressure drops to the preset lower limit, the pressure reduction valve is closed and the low pressure state is maintained for the set time; after reactivation, the boost solenoid valve 4.2 replenishes the pressure to the upper limit value, completing a single cycle.

[0056] Depend on Figure 4 It can be seen that, based on the environmental load coupled aging test of a certain brand of in-service PE80 polyethylene gas pipeline using this aging device, and to predict the service life of this in-service non-metallic pipeline, the calculation is performed according to the following steps:

[0057] Differential thermal scanning method was used to test the oxidation induction period (a) of in-service non-metallic pipelines. 工况 ;

[0058] Obtain the operating condition data (temperature T) of the in-service non-metallic pipeline. 工况 Relative humidity %RH 工况 Pipeline internal pressure P gas工况 External stress S 工况 );

[0059] PE80 gas pipelines of the same brand were selected as the test group, and the following aging tests were conducted:

[0060] The oxidation induction period a0 of PE80 pipe before aging was measured using differential thermal scanning method;

[0061] The PE80 pipe sample section of this grade was placed in the aging device described above, and a reference coupled environmental load was applied simultaneously: the temperature was set to 353K through the chamber temperature control system; the relative humidity was set to 45% RH through the chamber humidity control system; the internal pressure of the pipe was set to 0.4MPa through the internal pressure control system; and the mechanical stress was set to 2MPa through the external loading device. The air circulation system was started to maintain a constant oxygen environment. After aging, samples were taken to test the oxidation induction period a. end (Unit: min); Set the baseline parameters for the test apparatus: calibrated pressure P f =1 MPa (constant);

[0062] Coefficients were obtained using the least squares method: Variable temperature experiment: RH = 70%, P gas =0.3MPa, S=6MPa, four temperature gradients of 343K, 353K, 363K and 373K were taken, and the corresponding aging times t1, t2, t3 and t4 were recorded. The temperature coefficient B was fitted. The coefficient was obtained through gradient experiments. Constant temperature and humidity experiment: T=363K, P gas =0.3MPa, S=6MPa, let four humidity gradients of 30%, 50%, 70%, and 90%R be fitted with the humidity coefficient B. h ; Variable pressure test: fixed T = 363K, RH = 70%, S = 6MPa, with four pressure gradients of 0.1MPa, 0.2MPa, 0.3MPa and 0.4MPa, and fitting pressure coefficients C and D; Variable load test: fixed T = 363K, RH = 70%, P gas =0.3MPa, and set the stress coefficient E for four stress gradients of 2MPa, 4MPa, 6MPa and 8MPa;

[0063] For the oxidation induction period a end The oxidation induction period of PE80 pipes at different aging temperatures needs to be measured twice using differential thermal scanning: a ij i represents four temperatures, i = a, b, c, d, which are 343K, 353K, 363K, and 373K respectively; j represents the number of measurements, j = 1, 2;

[0064] Based on the oxidation induction period a0 before aging and the average oxidation induction period a after aging, the aging rate constant A is determined through nonlinear regression, ultimately yielding the performance relationship a for the same type of non-metallic pipe. end :

[0065]

[0066] in:

[0067]

[0068]

[0069]

[0070]

[0071]

[0072]

[0073]

[0074]

[0075]

[0076] Substituting the terms, we can obtain the coupling term F(P). gas ,%RH,S);

[0077] The service life (t) of the in-service non-metallic pipeline is finally obtained. 工况

[0078]

[0079] The service life of the in-service non-metallic pipeline can be calculated from the above steps to be 38.52 years. Based on the 50-year service life stipulated in the relevant national standards, if the current service environment remains unchanged, the non-metallic pipeline can continue to be used for another 11.48 years.

[0080] The aforementioned coupled humidity-oxygen-internal pressure-load non-metallic pipe aging test platform and its usage method enable parallel coupled aging tests on various non-metallic pipes, allowing for multiple combinations of different loads, aging times, and non-metallic pipes (different diameters, compositions, or diameter ratios). The relevant parameters obtained from the experimental results and the aforementioned life calculation steps constitute a coupled humidity-oxygen-internal pressure-load non-metallic pipe aging life evaluation method.

[0081] The above description is merely a preferred design of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent changes, and alterations made by those skilled in the art of aging using the above-disclosed technical content shall fall within the scope of the technical solution of the present invention.

Claims

1. A non-metallic pipe aging device coupled with humidity-heat-oxygen-internal pressure-load and its life prediction method, characterized in that, The non-metallic pipeline aging device comprises six parts: an inner cavity, a chamber temperature control system, a chamber humidity control system, a pipeline internal pressure control system, a pipeline external load loading device, and an air circulation system. It can conduct parallel aging tests on multiple non-metallic pipelines under different combinations of the four influencing factors: humidity, oxygen, internal pressure, and load. Furthermore, using the aging device, aging tests are performed on non-metallic pipelines of the same grade under the same service conditions (soil moisture, pipeline internal pressure, and external stress). The oxidation induction period before and after aging of in-service non-metallic pipelines and non-metallic pipelines of the same grade is measured using differential thermal scanning calorimetry. The service life of the non-metallic pipeline coupled with the humidity-heat-oxygen-internal pressure-load parameters is then calculated using the following formula: In the formula: t 工况 Service life of in-service non-metallic pipes; a0 and a 工况 These are the oxidation induction periods (unit: min) of non-metallic pipes of the same brand before aging and during service; E a It is the activation energy; R is the molar gas constant; T 工况 This refers to the service temperature (in K) of non-metallic pipes; P gas工况 This refers to the internal pressure of non-metallic pipes (unit: MPa). B h This is the Arrhenius humidity parameter; %RH 工况 It is the relative humidity of the soil in service (unit: %); P f This is the laboratory calibration pressure (unit: MPa, constant, related to pipe diameter); B h It is the Arrhenius humidity parameter; S 工况 The external stress of the pipeline in service (unit: MPa); A is the aging rate constant; B, C, and D are fitting parameters; F(P) gas ,%RH,S) represents the humidity-internal pressure-external stress coupling term.

2. The non-metallic pipe aging device coupled with humidity, heat, oxygen, internal pressure, and load according to claim 1, characterized in that, The inner cavity includes a temperature sensor, a humidity sensor, a microcomputer, an integrated control panel, air supply and return ducts, a top air outlet, an insulation layer, and shelves. The inner cavity has porous shelves with several external connection holes, allowing for the arrangement of several workstations for parallel aging tests. The chamber temperature control system mainly consists of a temperature sensor, the inner cavity, a high-strength PU foam and high-density glass fiber insulation layer, a high-tensile sealing strip, a blower (hot air circulation), a centrifugal fan, a nickel-chromium rapid-heating heating wire, and a microcomputer. These components, connecting the inner cavity and the air supply and circulation system, form a heat load control loop. The chamber humidity control system mainly consists of a humidity sensor... The system comprises a blower (humidity circulation), an inner cavity, a water tank, a refrigeration compressor, an evaporator, an air-cooled condenser, and a microcomputer. These components, along with the inner cavity and the air circulation system, form a wet load control loop. The pipeline internal pressure and external load loading device mainly consists of a porous pipe wall clamp, a stainless steel plug, a pressurizing plug, an air compressor, and a PLC control system. It connects to the sample inside the cavity via an air nozzle on the right side of the inner cavity and a snap-fit ​​connection. The system includes several sets of non-metallic pipes with plugs at both ends and an external wall clamping device. The pressurizing plug is connected via a snap-fit ​​connection, an air nozzle, and an air supply pipe. The plug is sealed to the non-metallic pipe using rubber rings and bolts with external pre-tightening force.

3. The method of using the non-metallic pipe aging device coupled with humidity, heat, oxygen, internal pressure, and load according to claim 1, characterized in that, Includes the following steps: 1) Select the load application mode, determine the load coupling method, and check the sensors, microcomputer, and other control devices inside the box; 2) Cut the non-metallic pipes that are tested in multiple parallel states under various coupling conditions into suitable sample segments. Use plugs 20 and 21 and porous pipe wall clamps 23 to clamp and seal the non-metallic pipes at both ends, and connect them to the gas nozzle 15.4 device and pipe through buckle 15.5 to confirm that the pipe sample segment has been fixed on the porous plate 15.

6. 3) Turn on air compressor 1 and PLC controller 2. After the pressure in the non-metallic pipeline is increased to the required value, check for air leaks and pressure instability. For the constant internal pressure loading process, the valve of air compressor 1 needs to be opened and the air compressor supply pipe connected to the air inlet 15.4 next to the inner cavity so that the output pressure is slightly higher than the upper limit of the pressure required for the experiment. Start PLC controller 2 and monitor the constant pressure data in real time after the pressure stabilizes; when the detected pressure is lower than the set value, PLC controller 2 sends a signal to the boost solenoid valve. 4.1 Power on to drive internal pressurization of the pipeline; after the pressure reaches the preset value, PLC controller 2 automatically shuts off the pressure boosting solenoid valve; the cycle pressure setting requires completing the air compressor startup and pre-pressure adjustment according to the previous steps, starting PLC controller 2 and setting the pressure boosting amplitude and cycle period; the pressure should show that the pressure rises to the peak value, automatically closes the valve after reaching the limit, and opens the pressure reducing solenoid valve 4.3 to release the pressure after the peak pressure is maintained for the set time; when the pressure drops to the preset lower limit, the pressure reducing valve closes and maintains the low pressure state for the set time; after reactivation, the pressure boosting solenoid valve 4.2 replenishes the pressure to the upper limit value, completing one cycle; 4) Close the inner cavity outer door, turn on the inner cavity lighting fixture, and turn on the power to the aging device; 5) Turn on the integrated control panel 14 and set the target temperature and humidity values; the alternating temperature and humidity load can be directly controlled by inputting function equations through the integrated control panel 14; the temperature and humidity regulation power can be controlled by setting the T signal through the integrated control panel 14; the temperature and humidity range can also be monitored in real time through the integrated control panel 14. 6) Disconnect the power supply, open the buckle, remove the plug, and obtain the non-metallic pipe after coupling aging. The aging test is now complete.

4. The life prediction method for the non-metallic pipeline aging device coupled with humidity, heat, oxygen, internal pressure, and load according to claim 1, characterized in that, The service life of non-metallic pipes is calculated according to the following steps: 1) The oxidation induction period a of in-service non-metallic pipelines was measured using differential thermal scanning method. 工况 ; 2) Obtain operating condition data (temperature T) of in-service non-metallic pipelines. 工况 Relative humidity %RH 工况 Pipeline internal pressure P gas工况 External stress S 工况 ); 3) The oxidation induction period a0 of the same grade of unaged non-metallic pipe was measured again using differential thermal scanning method; 4) Next, the non-metallic pipe sample section of this grade is placed in the aging device described in claim 1, and a coupled environmental load is applied simultaneously: the temperature T is set through the chamber temperature control system; the relative humidity %RH is set through the chamber humidity control system; and the internal pressure P of the pipe is set through the internal pressure control system. gas The stress S is set using an external loading device; the air circulation system is activated to maintain a constant oxygen environment; the oxidation induction period a is tested periodically; and the baseline parameters of the test apparatus are set: calibration pressure P. f ; 5) Obtaining coefficients using the least squares method: Variable temperature experiment: Fixed %RH, P gas S, within the set temperature range, sets n temperature gradients, based on n corresponding time t. n Fitting the temperature coefficient B; obtaining the coefficient through gradient experiments: constant temperature and humidity experiment: fixed T, P gas S, within the set humidity range RH, several humidity gradients are used to fit the humidity coefficient B. h ; Variable pressure test: With fixed T, %RH, and S, several pressure gradients are applied at the set pressure to fit the pressure coefficients C and D; Variable load test: With fixed T, %RH, and P gas Under the set pressure, several stress gradients are fitted to the stress coefficient E; based on multiple sets of differential scanning calorimetry (a, t) data, the aging rate constant A is determined by nonlinear regression. 6) The oxidation induction period 'a' of the aged pipeline was obtained again using the differential thermal scanning method. Multiple measurements were taken for parameter fitting, and the average oxidation induction period 'a' from multiple tests was used in the lifespan calculation. end ; 7) Obtain the aging performance formula for this grade of non-metallic pipe: 8) The coupling term F(P) is calculated using the above formula. gas ,%RH,S); 9) Finally, the service life t of the in-service non-metallic pipeline is obtained. 工况 for:

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