Blasting depressurization experiment equipment and method for oil and gas conveying composite pipe

Abstract

The invention discloses blasting depressurization experimental equipment and method for an oil and gas conveying composite pipe. The blasting depressurization experimental equipment comprises composite pipe adapters, experimental medium injection systems, dual-mode blasting devices, discharge pipes and controllers, wherein the two ends of the composite pipe are each provided with a composite pipe adapter; the damage condition of the composite pipe under rapid pressure reduction in the pipe can be analyzed, the bursting pressure load of the pipe is converted into the bursting load of the bursting disc, rapid and instant leakage of a medium in the pipe can be simulated on the premise that the composite pipe is not damaged, the device is closer to engineering practice, and the device is simple in structural process and convenient to operate. And the collapse critical pressure of the lining layer of the composite pipe under different discharge apertures can be directly obtained.

Description

Technical Field

[0001] The present invention belongs to the technical field of composite pipe performance testing, and specifically relates to a blasting and pressure reduction experimental device and method for oil and gas transportation composite pipes. Background Art

[0002] Using composite pipes with excellent performance for oil and gas transportation is an important method to address the corrosion problem of oil and gas transportation. The composite pipe is composed of a polymer inner lining layer resistant to oil and gas media corrosion and a structural layer that bears the pipeline structural load. Most polymer materials are semi-crystalline materials, with a crystallinity far lower than that of metal materials. There are a large number of amorphous regions, with a relatively large free volume and a relatively small intermolecular force between molecules. These free volumes form microscopic channels for small-volume particles to enter the material interior. Therefore, the permeability of the material is much higher than that of metal materials. During high-pressure oil and gas transportation, the inner layer of the composite pipe is in contact with the transported oil and gas. Under the action of the pressure difference, gas small molecules in the oil and gas penetrate into the pipe wall through adsorption, diffusion, etc. After a period of accumulation, the gas pressure accumulated in the pipe wall is equivalent to the pressure of the transported medium and tends to balance. In the event of an emergency shutdown or leakage accident in the pipeline system, the internal pressure of the pipeline suddenly decreases, and the gas that has penetrated into the pipeline material rapidly expands, easily causing the collapse, bulging of the inner layer of the composite pipe, and delamination between the inner layer and the reinforcement layer and between the reinforcement layer and the outer protection layer. For gas transmission pipelines, the gas decompression wave will also propagate along the pipeline. When the toughness of the pipeline material is insufficient, long-range cracking of the pipeline will occur. How to evaluate the ability of non-metallic composite pipes to withstand rapid pressure reduction caused by emergency shutdowns or leakage accidents, and whether the composite pipes can continue to be used safely after an emergency shutdown or leakage, are questions that must be answered in the engineering application of non-metallic composite pipes. The existing CN115901483A discloses a method for testing the radial buckling and collapse pressure of thermoplastic plastic pipes for oil and gas transportation. Through an annulus pressure test, the anti-buckling and collapse performance of the inner lining layer of the thermoplastic plastic-lined steel pipe product is obtained. This method is only applicable to plastic-lined steel pipes, and the pressure application speed is not comparable to the pipeline leakage pressure reduction speed, nor can it evaluate in-service pipelines. Summary of the Invention

[0003] To solve the above problems, the present invention designs a composite pipe blasting and pressure reduction experimental device and proposes a composite pipe blasting and pressure reduction experimental method to evaluate the pipeline performance of composite pipes under rapid pressure reduction of the internal medium and whether the in-service composite pipes that have experienced rapid pressure reduction events such as pipe bursting and leakage can continue to be used safely. The technical solution is as follows:

[0004] An experimental device for blasting and pressure reduction of an oil and gas transmission composite pipe, including composite pipe adapters, a dual-mode blasting device, a relief pipe, and a controller, which are installed at both ends of the composite pipe; one of the composite pipe adapters is connected to an experimental medium injection system, and a pressure monitor 1 and a temperature monitor 1 are provided between them. The other composite pipe adapter is connected to the dual-mode blasting device. A temperature adjustment system is provided on the outer wall of the composite pipe. The dual-mode blasting device is connected to the relief pipe. A relief pipe orifice plate is provided on the relief pipe. A rupture disc A and a rupture disc B are provided in the dual-mode blasting device. A cavity part A between the rupture disc A and the composite pipe adapter is provided with a pressure monitor 2, a temperature monitor 2, and a vent valve; a cavity part B between the rupture disc A and the rupture disc B is provided with a pressure monitoring instrument 3 and a switch valve 2; a relief hole is provided on the relief pipe orifice plate. The switch valve 1, the switch valve 2, the vent valve, the temperature monitor 1, the temperature monitor 2, the pressure monitor 1, the pressure monitor 2, the pressure monitor 3, and the temperature adjustment system are all connected to the controller.

[0005] Preferably, the rupture disc A and the rupture disc B are made of stainless steel, and the bursting pressure P of the rupture disc A A is the same as the experimental pressure of the composite pipe, and the bursting pressure P of the rupture disc B B is 0.6 - 1.2P A , the cavity part A and the cavity part B are isolated by the rupture disc A, and the cavity part B and the relief pipe are isolated by the rupture disc B.

[0006] Preferably, the relief pipe is a metal pipe connecting the relief orifice plate, and the relief orifice plate and the relief pipe are connected by a flange. The relief orifice plate is an orifice plate of different specifications, which is used to simulate leakage events under different scales and different pressure reduction rates.

[0007] Preferably, the composite pipe includes a non-metallic inner lining layer resistant to oil and gas medium corrosion and a structural layer bearing loads.

[0008] Preferably, the composite pipe is any one of a fiber-reinforced thermoplastic composite pipe, a glass fiber pipe, a plastic alloy composite pipe, a steel skeleton-reinforced thermoplastic resin composite continuous pipe, and a plastic-lined steel pipe.

[0009] Preferably, the vent valve is used for evacuation during pipeline purging of the composite pipe and pressure regulation of the composite pipe pipeline during the test process.

[0010] An experimental method for blasting and pressure reduction of an oil and gas transmission composite pipe is as follows:

[0011] S1. Open the switch valve 1 and the switch valve 2, and inject the experimental medium into the composite pipe through the experimental medium injection system;

[0012] S2. When the pressure monitor 2 shows that the pressure P2 in the cavity part A reaches the bursting pressure P of the rupture disc A AWhen it reaches 1 / 2 of it, open the second switching valve to inject N2 into the cavity part B, so that the pressure P3 of the cavity part B gradually increases to 1 / 2P A , close the second switching valve to stop injecting N2 into the cavity part B. At this time, the difference between the pressure P2 of the cavity part A and the pressure P3 of the cavity part B is less than the bursting pressure P of the bursting disc A A , the difference between the pressure P3 of the cavity part B and the pressure P4 of the discharge pipe is less than the bursting pressure P of the bursting disc A B , the bursting disc B does not reach the bursting condition, and the test device can continue to be filled with the test medium;

[0013] S2. Continue to add the test medium. When the temperature monitored by the second temperature monitor is less than the set test temperature, turn on the temperature adjustment system and adjust the temperature and pressure of the test medium according to the characteristics of the test medium until the set test temperature and pressure are reached;

[0014] S3. Insulate and maintain the pressure of the composite pipe. The insulation and pressure maintenance time is determined according to the permeability of the inner lining material of the composite pipe. The insulation and pressure maintenance time should ensure that the test medium fully penetrates into the composite pipe body;

[0015] S4. After completing the insulation and pressure maintenance, continue to fill N2 into the cavity part B. As N2 is continuously filled, P3 continuously increases. When P3 - P4 > P B , the bursting disc B bursts first, and P3 instantaneously decreases. At this time, P2 - P3 > P A , causing the bursting disc A to burst and the test gas in the composite pipe to be instantaneously discharged;

[0016] S5. After the test medium in the composite pipe is discharged, wait until the temperature of the entire test device drops to the ambient pressure and the test medium is completely dissipated, then disassemble the composite pipe to be tested and check the failure characteristics of the composite pipe to be tested under the rapid discharge of the test medium. Check whether there is liquid leakage between the layers of the composite pipe, whether there is swelling, bubbling, or collapse in the inner lining layer, and use industrial CT to check the penetration damage size of the composite pipe material.

[0017] Preferably, blind plates are used to block both ends of the bursting disc A and the bursting disc B, and the airtightness of the cavity part A and the cavity part B is checked.

[0018] Preferably, the following steps are further included:

[0019] S6. If there is no liquid leakage between the layers of the composite pipe after the test, the inner lining layer has not swelled, bubbled, or collapsed, and the penetration damage size is less than the acceptable defect size of the composite pipe, then use a composite pipe of the same specification, replace the discharge orifice plate with a larger diameter, install the bursting disc of the same specification, and conduct the next experiment;

[0020] S7. Repeat steps S1 - S6 until the detection indicates that there is liquid leakage between the composite pipe layers, the lining layer bulges or collapses, and the size of the penetration damage of the composite pipe is greater than the size of the defects that the composite pipe can withstand. At this time, the pressure reduction rate of the composite pipe is the maximum pressure reduction rate that the composite pipe can withstand.

[0021] Preferably, the following steps are further included: applying different test pressures to obtain the maximum pressure reduction rate that the composite pipe can withstand under the corresponding test pressures, and based on the experimental results, the curve of the composite pipe's resistance to rapid pressure reduction can be given through fitting.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] Through the double - membrane blasting device, the rapid, efficient, and safe release of the oil - gas medium in the composite pipe to be tested can be realized, which can be used to evaluate the ability of the composite pipe to withstand the rapid pressure reduction caused by emergency shutdown or leakage accidents. The present invention can analyze the damage situation of the composite pipe under rapid pressure reduction inside the pipe, convert the pipeline blasting pressure load into the blasting load of the bursting disc, and simulate the rapid instantaneous leakage of the medium inside the pipe without damaging the composite pipe, which is closer to the engineering reality. Moreover, the device structure process is simple, and the critical pressure of the collapse of the lining layer of the composite pipe under different discharge orifice diameters can be directly obtained. Description of the Drawings

[0024] Figure 1 It is a schematic diagram of the structure of this application.

[0025] Figure 2 It is the release process of the medium inside the pipe under different pressures and different discharge orifice diameters.

[0026] Figure 3 It is the curve of the composite pipe's resistance to rapid pressure reduction.

[0027] In the figure, 1 - Shut - off valve 1, 2 - Composite pipe adapter, 3 - Bursting disc A, 4 - Bursting disc B, 5 - Discharge pipe, 51 - Orifice plate of the discharge pipe, 6 - Vent valve, 7 - Shut - off valve 2, 8 - Pressure monitor 1, 9 - Temperature monitor 1, 10 - Pressure monitor 2, 11 - Pressure monitor 3, 12 - Pressure monitor 4, 13 - Temperature monitor 2. Detailed Embodiments

[0028] In order to more clearly understand the above - mentioned objects, features, and advantages of the present invention, the present invention will be further described below with reference to the drawings and embodiments.

[0029] An experimental device for bursting pressure reduction of an oil and gas transmission composite pipe, comprising composite pipe adapters 2 installed at both ends of the composite pipe, a dual-mode bursting device, a relief pipe 5, and a controller; one of the composite pipe adapters 2 is connected to the experimental medium injection system, and a pressure monitor 8 and a temperature monitor 9 are provided therebetween. The other composite pipe adapter 2 is connected to the dual-mode bursting device. A temperature adjustment system is provided on the outer wall of the composite pipe. The dual-mode bursting device is connected to the relief pipe 5. A relief pipe orifice plate 51 is provided on the relief pipe 5. A bursting disc A and a bursting disc B are provided inside the dual-mode bursting device. A cavity part A between the bursting disc A and the composite pipe adapter is provided with a pressure monitor 10, a temperature monitor 13, and a vent valve 6; a cavity part B between the bursting disc A and the bursting disc B is provided with a pressure monitoring instrument 11 and a switch valve 7; a relief hole is provided on the relief pipe orifice plate 51. The switch valve 1, the switch valve 7, the vent valve 6, the temperature monitor 9, the temperature monitor 13, the pressure monitor 8, the pressure monitor 10, the pressure monitor 11, the pressure monitor 12, and the temperature adjustment system are all connected to the controller.

[0030] The bursting disc A and the bursting disc B are made of stainless steel. The bursting pressure P of the bursting disc A A is the same as the experimental pressure of the composite pipe. The bursting pressure P of the bursting disc B B is 0.6 - 1.2P A , and the cavity part A and the cavity part B are isolated by the bursting disc A, and the cavity part B and the relief pipe are isolated by the bursting disc B.

[0031] The relief pipe 5 is a metal pipe connecting the relief orifice plate. The relief orifice plate and the relief pipe are connected by a flange. The relief orifice plate can be orifice plates of different specifications, which are used to simulate leakage events under different scales and different pressure reduction rates.

[0032] The composite pipe includes a non-metallic inner lining layer resistant to oil and gas medium corrosion and a structural layer bearing loads. The composite pipe is any one of a fiber-reinforced thermoplastic composite pipe, a glass fiber pipe, a plastic alloy composite pipe, a steel skeleton-reinforced thermoplastic resin composite continuous pipe, and a steel pipe with a plastic lining.

[0033] The vent valve 6 is used for evacuation during the purging of the composite pipeline to be tested and for pressure regulation of the composite pipeline under test during the test process.

[0034] Example 1

[0035] In this example, the test medium in the pipe is supercritical or dense-phase CO2 gas. The injected CO2 is liquefied CO2 at -20°C, and the injection pressure is 2 MPa. It is used to illustrate the usage method of this test device.

[0036] After the inlet of the composite pipe to be tested is properly connected to the CO2 injection system, slowly open the first switch valve 1. Since the temperature of the composite pipe to be tested is relatively high, at the initial stage of CO2 injection, the liquid CO2 entering the pipe will vaporize, causing the temperature of the composite pipe to drop and the pressure to rise. To ensure that enough liquid CO2 is injected into the composite pipe, fully open the vent valve of the device to depressurize the composite pipe, and continuously inject liquid CO2 into the composite pipe to be tested. After the temperature inside the composite pipe drops to -20 °C and the pressure inside the pipe drops to 2 MPa, close the vent valve slightly and slowly vent. After dry ice particles are contained in the gas discharged from the vent valve, the pipe is filled with low-temperature liquid CO2, and then close the vent valve.

[0037] Turn on the temperature control system of the device and slowly heat the composite pipe to be tested. During the heating process, the pipeline pressure gradually rises; when the temperature of the medium inside the pipe has not reached the preset experimental temperature but the pressure has reached the preset experimental pressure, open the vent valve, and the device slowly depressurizes to the preset experimental pressure.

[0038] When the pressure of the composite pipe to be tested rises to half of the bursting pressure of the selected bursting disc A, open the second switch valve of the dual-mode bursting device and inject high-pressure N2 into the dual-mode bursting device. When the pressure in the pipe section cavity of the dual-mode bursting device reaches half of the bursting pressure of the bursting disc A, close the high-pressure N2 injection switch valve 2. At this time, the bursting disc A and the bursting disc B do not burst.

[0039] Continue to heat and pressurize the pipeline until the preset experimental conditions are reached. Keep the temperature and pressure of the composite pipe to be tested stable to allow the CO2 inside the pipe to fully penetrate into the composite pipe.

[0040] After the CO2 inside the composite pipe is stably permeated, open the high-pressure N2 injection switch valve 2. When the pressure in the cavity part B of the dual-mode bursting device reaches the bursting pressure of the bursting disc B, the bursting disc B bursts, and the pressure in the cavity part B of the dual-mode bursting device instantly drops to atmospheric pressure, triggering the bursting of the bursting disc A, and the dense-phase or supercritical-phase CO2 inside the pipe is instantly discharged through the simulated discharge pipe.

[0041] Example 2

[0042] This example presents a method for detecting the maximum pressure reduction rate that a composite pipe can withstand using the composite pipe bursting and pressure reduction experimental device in Example 1, including the following steps:

[0043] 1) Connect the composite pipe to be tested and the dual-mode bursting disc using a composite pipe adapter, install the dual-mode bursting disc. Under the same test pressure, the pressure reduction rate of the pipeline is proportional to the aperture of the pipeline discharge hole, that is, the smaller the discharge hole, the slower the pipeline pressure reduction rate, as Figure 1 shown.

[0044] 2) Air tightness inspection and device integrity check: Close all valves, check the air tightness of the entire device, the operation of the valves, whether bursting discs A and B are intact, whether the temperature control system can operate normally, whether temperature monitors 9 and 13, pressure monitors 8, 10, 11, and 12 are normal, whether the data acquisition system is normal, whether the strain gauges are well pasted, and whether the strain acquisition system is normal.

[0045] 3) Connect the experimental gas cylinder to the inlet of the experimental device, purge and evacuate the composite pipe to be tested for at least 5 minutes. The purpose is to displace the air inside the pipe and remove the impurity gas inside the pipe.

[0046] 4) After purging, inject the test gas into the composite pipe to be tested. At this time, pay attention to the pressure gauge on the composite pipe to be tested. After filling to a pressure close to the design pressure of the composite pipe, the filling is completed. During the filling process, pay attention to the temperature of the medium inside the pipe. If the pipe temperature is too high and it is not suitable for gas filling, the pipe needs to be cooled first until it reaches a suitable filling temperature.

[0047] 5) Heat the composite pipe to be tested and control the pressure of the medium inside the pipe not to exceed the design pressure of the composite pipe through the vent valve 6 until the design temperature of the composite pipe is reached.

[0048] 6) After meeting the experimental requirements, keep the test pipe insulated and pressurized so that the test medium can fully penetrate into the composite pipe body.

[0049] 7) Start the double-membrane bursting device, connect the pipe section between the N2 gas cylinder and the bursting disc, open the electric valve 3, and fill the cavity between the two bursting discs with N2 to increase the pressure between the two bursting discs. The end of the composite pipe to be tested is open to the atmosphere. In the initial state, P2 - P3 < P A , P3 - P4 < P B , the bursting disc B does not reach the bursting condition. As N2 is continuously filled, P3 continuously increases. When P3 - P4 > P B , the bursting disc B bursts first, and P3 instantaneously decreases. At this time, P2 - P3 > P A , the bursting disc A bursts, and the test gas inside the pipe is instantaneously released.

[0050] 8) After the release is completed, wait for the entire device to stand still until the temperature drops to the ambient pressure and the test gas completely dissipates. Then disassemble the composite pipe to be tested, observe the failure characteristics of the composite pipe to be tested under the rapid release of the medium inside the pipe, conduct macroscopic analysis and dimensional measurement on the failed samples, check whether there is liquid leakage between the layers of the composite pipe, whether there is swelling, bubbling, or collapse in the inner lining layer, and use industrial CT to check the penetration damage size of the composite pipe material.

[0051] 9) After the test, there is no liquid leakage between the layers of the composite pipe, the inner lining layer does not swell, bubble, or collapse, and the size of the penetration damage is less than the acceptable defect size of the composite pipe. Then, use a composite pipe of the same specification, replace the relief orifice plate with a larger diameter, install a bursting disc of the same specification, and conduct the next experiment.

[0052] 10) Repeat steps 1) - 9) until the detection shows that there is liquid leakage between the layers of the composite pipe, the inner lining layer bulges or collapses, and the size of the penetration damage of the composite pipe is greater than the acceptable defect size of the composite pipe. At this time, the pressure reduction rate of the composite pipe is the maximum pressure reduction rate that the composite pipe can withstand.

[0053] 11) Similarly, by using different test pressures, the maximum pressure reduction rate that the composite pipe can withstand under the corresponding test pressures can be obtained. According to the experimental results, the performance curve of the composite pipe's resistance to rapid pressure reduction can be given through fitting, as Figure 3 .

[0054] Example 3:

[0055] A method for the bursting pressure reduction experiment of an oil and gas transportation composite pipe, which is realized by using the bursting pressure reduction experimental device in Example 1 and is used to evaluate the damage condition of the in-service composite pipe with leakage, including the following steps:

[0056] 1) Inspect the leaking composite pipe to determine the operating conditions of the composite pipe, including but not limited to temperature, pressure, flow rate, etc., and obtain the morphology of the leakage hole;

[0057] 2) Select a suitable bursting disc according to the operating temperature and pressure of the leaking composite pipe;

[0058] 3) Install the experimental leakage pipe section prepared by 3D printing or the leakage hole pipe section intercepted from the leaking composite pipe at the end of the test device as the simulated relief pipe;

[0059] 4) Select an unused composite pipe of the same specification as the composite pipe to be tested and connect it to the dual-mode bursting device through a composite pipe adapter;

[0060] 5) Introduce nitrogen into the composite pipeline to purge the composite pipe to be tested;

[0061] 6) Introduce the medium transported by the leaking pipeline into the pipeline to displace the composite pipe to be tested; after the displacement is completed, continue to inject the test medium into the composite pipe to be tested. Through the temperature control system and the pressure boosting system, make the temperature and pressure of the composite pipe to be tested the same as those of the leaking composite pipe, keep the temperature and pressure constant, and make the test medium fully penetrate into the composite pipe and reach stability;

[0062] 7) Start the double-membrane bursting device, connect the pipe section between the N2 gas cylinder and the bursting disc, open the electric valve 3, and fill the cavity between the two bursting discs with N2 to increase the pressure between the two bursting discs. The end of the composite pipe to be tested is open to the atmosphere. In the initial state, P2 - P3 < P A , P3 - P4 < P B , the bursting disc does not reach the bursting condition. As N2 is continuously filled, P3 increases continuously. When P3 - P4 > P B , bursting disc B bursts first, P3 decreases instantaneously. At this time, P2 - P3 > P A , bursting disc A bursts, and the medium in the pipe is discharged instantaneously;

[0063] 8) After the discharge is completed, wait for the temperature of the entire experimental device to drop to the ambient pressure, the test medium to completely dissipate, and the test pipeline to be purged and replaced qualified. Then remove the composite pipe to be tested, observe the failure characteristics and properties of the tested composite pipe under the rapid discharge of the medium in the pipe, conduct macroscopic analysis and dimension measurement on the failed samples, observe whether there is liquid leakage between the layers of the composite pipe, whether there are bulges or collapses in the inner lining layer, and use industrial CT to check whether the penetration damage size of the composite pipe is greater than the defect size that the composite pipe can withstand at the working temperature and working pressure;

[0064] 9) When there is liquid leakage between the layers of the composite pipe, there are bulges or collapses in the inner lining layer, and the penetration damage size of the composite pipe is greater than the defect size that the composite pipe can withstand at the working temperature and working pressure, the leaking composite pipe cannot be used continuously and should be replaced. If the above phenomena do not occur, the leaking composite pipe can be used continuously after passing the hydrostatic test.

[0065] Figure 3 In, when the pipeline operating pressure P is P2, the maximum pressure reduction rate V that the composite pipe can withstand a is expressed as a function of the operating pressure and is represented by the function L3: V a = P2;

[0066] When the pipeline operating pressure P is P1, the maximum pressure reduction rate that the composite pipe can withstand can be represented by the function L1: V a = V2;

[0067] When P1 < P < P2, the maximum pressure reduction rate V that the composite pipe can withstand a can be represented by the function L2, which is a function of the pipeline operating pressure V a = V2 + 0.07*P + 0.002*P 2 - 0.0001P 3 .

[0068] This application can be applied to the field of oil and gas transportation composite pipes. In particular, it relates to the failure behavior of oil and gas transportation composite pipes under rapid pressure reduction, which can be used for the assessment of the safety status of leaking pipelines and also for the quality inspection of composite pipelines.

[0069] The above are only the preferred embodiments of the present invention, and are not limitations on the present invention in other forms. Any person skilled in the art may use the technical content disclosed above to make changes or modifications into equivalent embodiments with equivalent changes and apply them to other fields. However, as long as it does not depart from the technical solution content of the present invention, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. An experimental device for bursting pressure reduction of an oil and gas transportation composite pipe, characterized in that, It includes installing composite pipe adapters, a dual-mode blasting device, a relief pipe, and a controller at both ends of the composite pipe; one of the composite pipe adapters is connected to the experimental medium injection system, and a pressure monitor I and a temperature monitor I are provided between them. The other composite pipe adapter is connected to the dual-mode blasting device. A temperature adjustment system is provided on the outer wall of the composite pipe. The dual-mode blasting device is connected to the relief pipe. A relief pipe orifice plate is provided on the relief pipe. A bursting disc A and a bursting disc B are provided inside the dual-mode blasting device. A pressure monitor II, a temperature monitor II, and a vent valve are provided in the cavity part A between the bursting disc A and the composite pipe adapter; a pressure monitoring instrument III and a switch valve II are provided in the cavity part B between the bursting disc A and the bursting disc B; a relief hole is provided on the relief pipe orifice plate. The switch valve I, switch valve II, vent valve, temperature monitor I, temperature monitor II, pressure monitor I, pressure monitor II, pressure monitor III, and temperature adjustment system are all connected to the controller.

2. The blasting pressure reduction experimental equipment for an oil and gas transportation composite pipe according to claim 1, characterized in that, The rupture discs A and B are made of stainless steel. The bursting pressure P of rupture disc A A is the same as the test pressure of the composite pipe. The bursting pressure P of rupture disc B B is 0.6 - 1.2P A . The cavity part A is isolated from the cavity part B by the rupture disc A, and the cavity part B is isolated from the discharge pipe by the rupture disc B.

3. The blasting pressure reduction experimental equipment for an oil and gas transportation composite pipe according to claim 1, characterized in that The relief pipe is a metal pipe connecting the relief orifice plate, and the relief orifice plate is connected to the relief pipe through a flange. The relief orifice plate is an orifice plate of different specifications and is used to simulate leakage events under different scales and different pressure reduction rates.

4. An experimental device for blasting pressure reduction of an oil and gas transmission composite pipe according to claim 1, characterized in that, The composite pipe includes a non-metallic inner lining layer resistant to oil and gas medium corrosion and a structural layer bearing the load.

5. The blasting pressure reduction experimental equipment for an oil and gas transportation composite pipe according to claim 1 or 4, characterized in that, The composite pipe is any one of a fiber-reinforced thermoplastic composite pipe, a glass fiber pipe, a plastic alloy composite pipe, a steel skeleton reinforced thermoplastic resin composite continuous pipe, and a plastic-lined steel pipe.

6. The blasting pressure reduction experimental equipment for an oil and gas transportation composite pipe according to claim 1, characterized in that, The vent valve is used for evacuation during the pipeline purging of the composite pipe and for pressure regulation of the composite pipe pipeline during the test process.

7. A method for the bursting pressure reduction experiment of an oil and gas transportation composite pipe, characterized in that, The steps are as follows: S1. Open the switch valve I and switch valve II, and inject the experimental medium into the composite pipe through the experimental medium injection system. S2. When the pressure monitor II shows that the pressure P2 in the cavity part A reaches 1 / 2 of the bursting pressure P of the bursting disc A A open the switch valve II, inject N2 into the cavity part B, and gradually increase the pressure P3 in the cavity part B to 1 / 2P A , close the switch valve II, and stop injecting N2 into the cavity part B. At this time, the difference between the pressure P2 in the cavity part A and the pressure P3 in the cavity part B is less than the bursting pressure P of the bursting disc A A , the difference between the pressure P3 in the cavity part B and the pressure P4 in the discharge pipe is less than the bursting pressure P of the bursting disc A B , the bursting disc B does not reach the bursting condition, and the test device can continue to be filled with the experimental medium; S2. Continue to add the experimental medium. When the temperature monitored by the temperature monitor II is less than the set experimental temperature, open the temperature adjustment system, and adjust the temperature and pressure of the experimental medium according to the characteristics of the experimental medium until the set experimental temperature and pressure are reached. S3. Keep the temperature and pressure of the composite pipe constant. The heat preservation and pressure maintenance time is determined according to the permeability of the inner lining material of the composite pipe, and the heat preservation and pressure maintenance time should ensure that the experimental medium fully penetrates into the composite pipe body. S4. After the heat preservation and pressure holding are completed, continue to inject N2 into the cavity part B. As N2 is continuously filled, P3 continuously increases. When P3 - P4 > P B , the rupture disc B bursts first, and P3 instantaneously decreases. At this time, P2 - P3 > P A , causing the rupture disc A to burst, and the test gas in the composite pipe is instantaneously discharged; S5. After the experimental medium in the composite pipe is discharged, wait until the temperature of the entire experimental device drops to the ambient pressure and the test medium is completely dissipated, then disassemble the composite pipe under test, check the failure characteristics of the composite pipe under test under the rapid discharge of the experimental medium, check whether there is liquid leakage between the layers of the composite pipe, whether there is swelling, bubbling, or collapse of the inner lining layer, and use industrial CT to check the penetration damage size of the composite pipe material.

8. A method for a bursting pressure reduction experiment of an oil and gas transportation composite pipe according to claim 7, characterized in that, Seal both ends of the bursting disc A and bursting disc B with blind plates, and check the airtightness of the cavity part A and cavity part B.

9. A method for a bursting pressure reduction experiment of a composite pipe for oil and gas transportation according to claim 7, characterized in that, It also includes the following steps: S6. If there is no liquid leakage between the layers of the composite pipe after the test, the inner lining layer has not swelled, bubbled, or collapsed, and the penetration damage size is less than the acceptable defect size of the composite pipe, then use a composite pipe of the same specification, replace the relief orifice plate with a larger diameter, install the bursting disc of the same specification, and conduct the next experiment. S7. Repeat steps S1 to S6 until the detection shows that there is liquid leakage between the composite pipe layers, the lining layer bulges, collapses, and the penetration damage size of the composite pipe is greater than the defect size that the composite pipe can withstand. At this time, the pressure reduction rate of the composite pipe is the maximum pressure reduction rate that the composite pipe can withstand.

10. A method for bursting pressure reduction experiment of an oil and gas transportation composite pipe according to claim 7, characterized in that, It also includes the following steps: Using different test pressures, obtain the maximum pressure reduction rate that the composite pipe can withstand under the corresponding test pressures. According to the experimental results, the rapid pressure reduction resistance performance curve of the composite pipe can be given by fitting.

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