Method for determining critical gas operating pressure for collapse of bonded composite pipe lining

Abstract

The present invention discloses a method for determining the critical gas operating pressure for collapse of the inner lining of a bonding type composite pipe, which comprises obtaining the porosity volume, operating temperature, operating time and conveying gas component of the reinforcement layer of the bonding type composite pipe; testing the gas permeability coefficient of the inner lining layer, the gas permeability coefficient of the reinforcement layer and the gas permeability coefficient of the outer protective layer respectively according to the operating temperature and the conveying gas component; inputting the pore volume, operating temperature, operating time, the gas permeability coefficient of the inner lining layer, the gas permeability coefficient of the reinforcement layer and the gas permeability coefficient of the outer protective layer into a pre-constructed pore permeability pressure model of the reinforcement layer of the bonding type composite pipe to obtain the pore permeability pressure of the reinforcement layer; determining the radial collapse pressure of the inner lining layer of the bonding type composite pipe; inputting the pore permeability pressure of the reinforcement layer and the radial collapse pressure of the inner lining layer into a pre-constructed critical collapse failure criterion model to obtain the critical gas operating pressure for collapse of the inner lining of the bonding type composite pipe.

Description

Technical Field

[0001] The invention belongs to the technical field of non-metallic composite pipe performance testing, and in particular relates to a method for determining a critical gas operating pressure for collapse of an inner lining of a bonding type composite pipe. Background Art

[0002] Reinforced thermoplastic continuous pipe (also known as RTP pipe, flexible composite pipe, coiled pipe, etc.) has been widely promoted and applied in domestic and foreign oil and gas fields due to its continuous molding, single pipe can reach hundreds of meters, few joints, good flexibility, excellent impact resistance, light weight, low transportation cost, quick and simple installation and other advantages, and has become one of the most promising non-metallic composite pipes. Reinforced thermoplastic continuous pipe can be divided into non-bonded composite pipe and bonded composite pipe according to the cross-sectional structure. The non-bonded composite pipe is composed of a layered thermoplastic plastic lining layer, a reinforcement layer and an outer protective layer, which are coated layer by layer. Relative displacement can occur between the layers when deformed. During the service of the non-bonded composite pipe, various gases dissolved in the petroleum medium, such as CH 4 , H 2 S, CO 2 The gas that penetrates into the interlayer between the thermoplastic liner and the reinforcement layer will gradually accumulate. When the pipeline is shut down, the internal pressure fluctuates, or there is a sudden negative pressure, the external pressure generated by the gas accumulated in the interlayer will cause the thermoplastic liner to collapse and fail.

[0003] In order to improve the anti-collapse performance of the lining layer of reinforced thermoplastic continuous pipe, bonded composite pipe came into being. Figure 1 As shown, this type of pipe is also divided into three layers of inner lining layer 24, reinforcement layer 25 and outer protective layer 26, but its outstanding feature is that the structural layers are bonded together. Among them, the inner lining layer is a thermoplastic plastic extruded pipe, which is in contact with the conveying medium and plays the role of corrosion prevention, barrier and temperature resistance; the reinforcement layer is a fiber reinforced thermoplastic plastic tape (CFRT) wound, heated and melted, cooled and bonded to play the role of bearing (internal pressure, stretching, etc.); the outer protective layer is extruded and coated to play the role of external protection and wear resistance.

[0004] Although the structural layers of the bonded composite pipe are bonded together to form a solid wall structure, gas permeation is still inevitable on the one hand, and pores or voids are still inevitable in composite pipes on the other hand. Therefore, the gas that penetrates into the composite pipe wall thickness direction will also accumulate in the weak positions of the composite pipe reinforcement layer, such as pores, voids or interfaces. Harsh oil and gas gathering and transportation conditions, such as high temperature and high pressure environment, will aggravate the impact of gas permeation, and the majority of oilfield users still question the radial collapse of the inner liner of the bonded composite pipe. Summary of the invention

[0005] In response to the problems existing in the prior art, the present invention provides a method for determining the critical gas operating pressure of the inner lining of a bonded composite pipe, which can determine the critical gas operating pressure of the bonded composite pipe, thereby guiding the optimization of the operating pressure parameters of the pipeline and controlling the total amount of gas penetration into the reinforcement layer, thereby avoiding the collapse and failure of the inner lining layer of the bonded composite pipe from the source.

[0006] In order to solve the above technical problems, the present invention is implemented by the following technical solutions:

[0007] A method for determining the critical gas operating pressure for the collapse of the lining of a bonded composite pipe comprises:

[0008] Obtaining the porosity volume of the reinforcement layer of the bonded composite pipe, the operating temperature of the bonded composite pipe, the operating time of the bonded composite pipe, and the transport gas component of the bonded composite pipe;

[0009] According to the operating temperature and the transported gas component, the gas permeability coefficient of the inner lining layer of the bonded composite pipe, the gas permeability coefficient of the reinforcement layer of the bonded composite pipe and the gas permeability coefficient of the outer protective layer of the bonded composite pipe are respectively tested;

[0010] Input the pore volume of the reinforcement layer, the operating temperature, the operating time, the gas permeability coefficient of the lining layer, the gas permeability coefficient of the reinforcement layer and the gas permeability coefficient of the outer protective layer into a pre-constructed pore permeability pressure model of the reinforcement layer of the bonding type composite pipe to obtain the pore permeability pressure of the reinforcement layer of the bonding type composite pipe;

[0011] Determining the radial collapse pressure of the inner lining layer of the bonded composite pipe;

[0012] The pore permeability pressure of the reinforcement layer and the radial collapse pressure of the lining layer are input into a pre-constructed critical collapse failure criterion model to obtain the critical gas operating pressure of the bonded composite pipe liner collapse.

[0013] Furthermore, the pore permeability pressure model of the enhanced layer is specifically:

[0014]

[0015] in,

[0016] Where P i is the pore permeability pressure of the enhancement layer; P 1 is the critical gas operating pressure; P 2 is atmospheric pressure; R is the molar gas constant; T is the pipeline operating temperature; V is the pore volume of the bonding composite pipe reinforcement layer; l 1 is the wall thickness of the lining layer; C 1is the gas permeability coefficient of the lining layer; D 1 is the diameter of the inner lining; l 2 is the wall thickness of the reinforcement layer; C 2 is the gas permeability coefficient of the reinforcement layer; D 2 is the diameter of the reinforcement layer; l 3 is the wall thickness of the outer protective layer; C 3 is the gas permeability coefficient of the outer protective layer; D 3 is the diameter of the outer protective layer; t is the running time.

[0017] Furthermore, the critical collapse failure criterion model is specifically:

[0018] P i =P 1 +P c

[0019] Where P c It is the radial collapse pressure of the inner lining of the bonded composite pipe.

[0020] Further, the gas permeability coefficient of the inner lining layer of the bonded composite pipe, the gas permeability coefficient of the reinforcement layer of the bonded composite pipe and the gas permeability coefficient of the outer protective layer of the bonded composite pipe are tested respectively according to the operating temperature and the transport gas component, specifically including:

[0021] The same raw material as the inner lining layer of the bonding type composite pipe is prepared into a first thermoplastic plastic film sample, the same raw material as the reinforcing layer of the non-bonding type composite pipe is prepared into a second thermoplastic plastic film sample, and the same raw material as the outer protective layer of the non-bonding type composite pipe is prepared into a third thermoplastic plastic film sample;

[0022] The gas permeability test temperature is set to the operating temperature, and a gas permeability meter is used to test the gas permeability coefficient of the transported gas component in the first thermoplastic plastic film sample, which is the gas permeability coefficient of the inner lining layer of the bonding type composite pipe; the gas permeability coefficient of the transported gas component in the second thermoplastic plastic film sample is tested, which is the gas permeability coefficient of the bonding type composite pipe reinforcement layer; the gas permeability coefficient of the transported gas component in the third thermoplastic plastic film sample is tested, which is the gas permeability coefficient of the outer protective layer of the bonding type composite pipe.

[0023] Furthermore, the preparation process of the first thermoplastic plastic film sample is the same as the preparation process of the bonding type composite pipe lining layer;

[0024] The preparation process of the second thermoplastic plastic film sample is the same as the preparation process of the bonding type composite pipe reinforcement layer;

[0025] The preparation process of the third thermoplastic plastic film sample is the same as the preparation process of the outer protective layer of the bonding composite pipe.

[0026] Further, the determining of the radial collapse pressure of the inner lining layer of the bonding type composite pipe specifically includes:

[0027] Conduct environmental simulation tests on bonded composite pipe test samples;

[0028] Conduct radial pressure test on the inner lining layer of the bonded composite pipe test sample, and record the pressure change between the reinforcement layer and the inner lining layer of the bonded composite pipe sample;

[0029] According to the change of the interlayer pressure between the reinforcement layer and the inner lining layer of the bonded composite pipe sample, a pressure change curve between the reinforcement layer and the inner lining layer of the bonded composite pipe sample is drawn;

[0030] The radial collapse pressure of the inner lining layer of the bonding type composite pipe is obtained according to the pressure variation curve.

[0031] Furthermore, when the radial pressure test is performed on the inner lining layer of the bonded composite pipe test sample, the pressure rate is controlled at 0.1 MPa / s to 0.5 MPa / s.

[0032] Furthermore, the porosity volume of the reinforcement layer is obtained by testing using the Archimedes drainage method.

[0033] Furthermore, when there is fluctuation or negative pressure in the operating pressure of the bonded composite pipe, the radial collapse pressure should be corrected with a correction factor of 0.5 to 0.8.

[0034] Compared with the prior art, the present invention has at least the following beneficial effects: the present invention provides a method for determining the critical gas operating pressure for collapse of the inner lining of a bonded composite pipe, which tests the gas permeability coefficient of the inner lining layer of the bonded composite pipe, the gas permeability coefficient of the reinforced layer of the bonded composite pipe and the gas permeability coefficient of the outer protective layer of the bonded composite pipe according to the operating temperature and the transport gas component; the pore volume of the reinforced layer, the operating temperature, the operating time, the gas permeability coefficient of the inner lining layer, the gas permeability coefficient of the reinforced layer and the gas permeability coefficient of the outer protective layer are input into a pre-constructed permeability pressure model of the reinforced layer of the bonded composite pipe to obtain the permeability pressure in the reinforced layer of the bonded composite pipe; the radial collapse pressure of the inner lining layer of the bonded composite pipe is determined; the permeability pressure of the reinforced layer and the radial collapse pressure are input into a pre-constructed critical collapse failure criterion model to obtain the critical gas operating pressure for collapse of the inner lining of the bonded composite pipe. On the one hand, the present invention considers the gas permeation problem that causes the collapse of the lining of the bonded composite pipe, and on the other hand, it also considers the anti-collapse performance of the lining layer of the bonded composite pipe itself. The permeation pressure model in the pores of the reinforcement layer of the bonded composite pipe is used to obtain the permeation pressure of the reinforcement layer of the bonded composite pipe. Finally, the critical gas operating pressure of the collapse of the lining of the bonded composite pipe is obtained using the critical collapse failure criterion model. The calculation results are intuitive and reliable, and have strong guidance. The method of the present invention calculates and determines whether there is a risk of collapse and failure of the lining layer of the bonded composite pipe after running for a period of time. The present invention can deduce the critical operating partial pressure of different gases that cause the collapse of the liner under actual operating conditions by testing the gas permeability coefficients of different transport gas components in the lining layer, the reinforcement layer, and the outer protective layer.

[0035] The radial collapse pressure test method of the bonded composite pipe liner of the present invention is reasonably designed, intuitive to test, and easy to operate. It can also simulate the service conditions of full-size composite pipe products under oil and gas transportation working conditions to the maximum extent. The temperature, pressure, gas components, and liquid medium can all be adjusted. The test sample can be rotated. The adhesive is used to achieve the bonding of the thermoplastic plastic liner pipe and the steel pipeline. The interface bonding between the bonded composite pipe liner and the reinforcement layer is simulated. The P c The value is more accurate, and the test data obtained is accurate and reliable.

[0036] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the technical solutions in the specific implementation modes of the present invention, the drawings required for use in the description of the specific implementation modes will be briefly introduced below. Obviously, the drawings described below are some implementation modes of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0038] Figure 1 It is a gas permeation model of bonded composite pipe;

[0039] Figure 2 It is a schematic diagram of a collapse pressure test system for a thermoplastic lined pipe;

[0040] Figure 3 This is the radial collapse pressure test curve of thermoplastic lined pipe.

[0041] In the figure: 1-transfer joint; 2-pressure gauge; 3-thermoplastic plastic liner pipe; 4-sealing plug; 5-flange; 6-fastening screw; 7-steel base pipe; 8-water inlet; 9-pressure hose; 10-pressure pump; 11-nut; 12-inlet valve; 13-pressure relief valve; 14-pressure sensor connection port; 15-data acquisition system; 16-pressure sensor; 17-pressure pipe; 18-gas cylinder; 19-transmission belt; 20-motor; 21-environmental test chamber; 22-support seat; 23-exhaust gas treatment system; 24-inner lining; 25-reinforcement layer; 26-outer protective layer. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] As a specific embodiment of the present invention, a method for determining the critical gas operating pressure for collapse of a bonded composite pipe liner specifically comprises the following steps:

[0044] Step 1: Obtain the pore volume V of the reinforcement layer of the bonded composite pipe, the operating temperature T of the bonded composite pipe, the operating time t of the bonded composite pipe, and the transport gas component of the bonded composite pipe; generally, the transport gas component includes CH 4 , CO 2 , O 2 、N 2 and H 2 S.

[0045] Specifically, the pore volume V of the reinforcement layer is obtained by testing using the Archimedes drainage method.

[0046] Step 2: Test the gas permeability coefficient C of the inner lining of the bonded composite pipe according to the operating temperature T and the transported gas composition. 1 , Gas permeability coefficient C of the reinforcement layer of the bonding composite pipe 2 Gas permeability coefficient C of the outer protective layer of the bonding composite pipe 3 .

[0047] As a preferred embodiment, the gas permeability coefficient C of the inner lining of the bonded composite pipe is tested. 1 , Gas permeability coefficient C of the reinforcement layer of the bonding composite pipe 2 Gas permeability coefficient C of the outer protective layer of the bonding composite pipe 3 The specific steps include:

[0048] Step a: preparing a first thermoplastic plastic film sample from the same raw material as the inner lining layer of the bonding type composite pipe, preparing a second thermoplastic plastic film sample from the same raw material as the reinforcement layer of the non-bonding type composite pipe, and preparing a third thermoplastic plastic film sample from the same raw material as the outer protective layer of the non-bonding type composite pipe;

[0049] The preparation process of the first thermoplastic film sample is the same as the preparation process of the inner lining layer of the bonding type composite pipe;

[0050] The preparation process of the second thermoplastic film sample is the same as the preparation process of the reinforcement layer of the bonding type composite pipe;

[0051] The preparation process of the third thermoplastic plastic film sample is the same as the preparation process of the outer protective layer of the bonding type composite pipe.

[0052] Step b: Set the gas permeability test temperature to the operating temperature T, refer to GB / T 1038, use a gas permeameter to test the gas permeability coefficient of the transported gas component in the first thermoplastic plastic film sample, which is the gas permeability coefficient C of the inner lining layer of the bonded composite pipe. 1 , the gas permeability coefficient of the transported gas component in the second thermoplastic film sample is tested, which is the gas permeability coefficient C of the reinforced layer of the bonding composite pipe. 2 , the gas permeability coefficient of the transported gas component in the third thermoplastic plastic film sample is tested, which is the gas permeability coefficient C of the outer protective layer of the bonding composite pipe 3 .

[0053] Step 3: The pore volume V of the reinforcement layer, the operating temperature T, the operating time t, and the gas permeability coefficient C of the lining layer 1 , gas permeability coefficient C of the reinforcement layer 2 and the gas permeability coefficient C of the outer protective layer 3Input the pre-built pore permeability pressure model of the bonded composite pipe reinforcement layer to obtain the pore permeability pressure P of the bonded composite pipe reinforcement layer. i ;

[0054] Interlayer osmotic pressure P i The calculation formula is f(T,t,C 1 ,C 2 ,C 3 ,P 1 ,V), specifically, the interlayer penetration pressure model is:

[0055]

[0056] in:

[0057] In the formula, P 1 is the critical gas operating pressure.

[0058] Step 4: Determine the radial collapse pressure P of the bonded composite pipe liner c .

[0059] As a preferred embodiment, the radial collapse pressure P of the inner liner of the bonding composite pipe is determined as follows: c , specifically including:

[0060] Conduct environmental simulation tests on bonded composite pipe test samples;

[0061] Perform a radial pressure test on the inner lining layer of the bonded composite pipe test sample, and record the pressure change between the reinforcement layer and the inner lining layer of the bonded composite pipe sample; preferably, when performing a radial pressure test on the inner lining layer of the bonded composite pipe test sample, the pressure rate is controlled at 0.1 MPa / s to 0.5 MPa / s;

[0062] According to the pressure change between the reinforcement layer and the inner lining layer of the bonded composite pipe sample, a pressure change curve between the reinforcement layer and the inner lining layer of the bonded composite pipe sample is drawn;

[0063] According to the pressure change curve, the radial collapse pressure P of the inner lining of the bonding composite pipe is obtained. c ,like Figure 3 As shown, the pressure corresponding to the highest peak of the pressure change curve is the radial collapse pressure of the inner lining layer of the bonding type composite pipe.

[0064] More specifically, Figure 2As shown, in this embodiment, the bonding type composite pipe test sample is a thermoplastic lined composite steel pipe test sample, and the thermoplastic lined composite steel pipe test sample is composed of a thermoplastic lined pipe 3 with the same material and the same size as the inner lining layer of the bonding composite pipe inserted into the steel base pipe 7, and the outer surface of the thermoplastic lined pipe 3 is coated with adhesive, and the bonding with the steel base pipe 7 is achieved by steam pressure heating, and the interface between the thermoplastic lined pipe 3 and the steel base pipe 7 is the interlayer. Preferably, the length of the bonding type composite pipe test sample is at least greater than 5 times the outer diameter, and the end of the thermoplastic lined pipe 3 is 15mm to 30mm longer than the steel base pipe 7.

[0065] like Figure 2 As shown, in this embodiment, a method for determining the radial collapse pressure P of the inner lining of the bonding type composite pipe is provided. c The test system includes test samples, end sealing system, interlayer pressure system, interlayer pressure monitoring system and oil and gas working environment simulation test system.

[0066] In the test system, the two ends of the test sample are inserted into the thermoplastic plastic liner tube 3 by the sealing plug 4 and the ends are sealed by the sealing ring. The transfer joint 1 is connected to the sealing plug 4 by threaded connection. The transfer joint (1) is provided with a pressure gauge 2, an air inlet valve 12 and a pressure relief valve 13 to control the pressure or pressure relief inside the test sample during the environmental simulation test. The transfer joint 1 is also provided with a through hole to connect an external gas cylinder or a vacuum pump and a pressure circulation pump.

[0067] In the test system, the end face of the steel base pipe 7 is sealed with a flange 5 and a sealing ring. The flanges 5 at both ends of the test sample are connected by a fastening screw 6 and fastened with a nut 11. The steel base pipe 7 is provided with a water inlet 8 and a pressure sensor connection port 14. The pressure pump 10 is connected to the water inlet 8 through a pressure hose 9 to achieve pressure on the interlayer of the test sample. The data acquisition system 15 is connected to the pressure sensor connection port 14 through a pressure sensor 16 to monitor the change of the interlayer pressure in real time and collect the pressure change curve.

[0068] When in use, after one end of the test sample is sealed with a sealing plug 4, the liquid medium for simulating oil field transportation (such as oil, water, oil field on-site stock liquid, simulated stock liquid configured in the laboratory) is placed into the test sample, and the other end of the test sample is sealed with a sealing plug 4. The transfer joint 1 connected to the sealing plug 4 is connected to the pressure pipe 17 and the gas cylinder 18 through the internal through hole. Close the pressure relief valve 13 and open the air inlet valve 12 to pressurize the inside of the test sample. After the test sample is pressurized to the set value, close the air inlet valve 12, place the entire test sample filled with liquid medium and maintaining a certain internal pressure on the support seat 22, and push it into the environmental test box 21. The environmental test box 21 is heated by air to achieve the functions of heating, heat preservation and air circulation constant temperature. The transfer joint 1 connected to the sealing plug 4 can be connected to the motor 20 through the transmission belt 19. The motor 20 is started to drive the test sample to rotate. Preferably, the motor speed is 10-50r / min, which can ensure that the entire inner wall of the thermoplastic lining pipe is in contact with the liquid medium and realize dynamic simulation test. The test cycle is preferably 2 days, 7 days or 14 days. After setting the corresponding test parameters (such as pressure, temperature, time and speed), the oil and gas working environment simulation test of the thermoplastic lining can be completed. Then, connect Figure 2 The interlayer pressure system, interlayer pressure monitoring system and other modules shown can carry out radial collapse pressure test of thermoplastic lined pipes. The gas after the test is safely treated through the exhaust gas treatment system 23.

[0069] In summary, the radial collapse pressure P of the inner liner of the bonding type composite pipe of this embodiment is c The specific test steps are as follows:

[0070] 1) The hot melt adhesive is evenly applied to the outer surface of the thermoplastic liner pipe to be used in the bonding type composite pipe, and it is inserted into the steel base pipe of matching size according to the traditional internal insertion process, and hot steam is passed into the thermoplastic liner pipe, and the hot melt adhesive is melted by pressurized heating, and then the thermoplastic liner pipe and the steel base pipe are bonded together to prepare a thermoplastic liner composite steel pipe test sample;

[0071] 2) According to the specifications and dimensions (outer diameter, inner diameter, wall thickness) of the thermoplastic lined composite steel pipe test sample, the test sample end sealing system is designed, and an interlayer pressure system and an interlayer pressure monitoring system are set up in the middle part of the steel base pipe layer of the test sample;

[0072] 3) After placing the oil-water medium into the test sample, seal it with the end sealing device and put it into the environmental test box to establish the field application conditions of the thermoplastic lined composite steel pipe (heating to a certain temperature, dynamic operation) and carry out environmental simulation tests;

[0073] 4) After the environmental simulation test is completed, the test sample is connected to the interlayer pressure system and the interlayer pressure monitoring system, the interlayer pressure test is carried out, the interlayer pressure change is recorded, the interlayer pressure change curve is analyzed, and the radial collapse pressure P of the thermoplastic lined pipe under the simulated working environment is determined. c .

[0074] Preferably, when there is fluctuation or negative pressure in the operating pressure of the bonded composite pipe, the radial collapse pressure should be corrected with a correction factor of 0.5 to 0.8.

[0075] Step 5: Input the interlayer penetration pressure and radial collapse pressure into the pre-constructed critical collapse failure criterion model to obtain the critical gas operating pressure for the collapse of the bonded composite pipe liner;

[0076] Combination Figure 1 As shown, when P i =f(T,t,C 1 ,C 2 ,C 3 ,P 1 ,V)>P 1 +P c When the inner lining collapses and fails, the critical collapse failure criterion model is obtained as follows:

[0077] P i =P 1 +P c

[0078] Where P c It is the radial collapse pressure of the inner lining of the bonded composite pipe.

[0079] In order to explain the interlayer penetration pressure model between the reinforcement layer and the lining layer of the bonded composite pipe in more detail, the following is a specific description:

[0080] The formula governing gas permeation can be derived from Fick's first law:

[0081]

[0082] Where: Q is the gas permeability; A is the surface area; P is the pipeline operating pressure; l is the wall thickness of the thermoplastic lining layer; C is the gas permeability coefficient; t is time.

[0083] like Figure 1 As shown in the figure, since the reinforcement layer is a fiber-reinforced thermoplastic composite material, it is the part of the pipe where pores or voids are most likely to exist. Therefore, the pore permeability pressure P of the reinforcement layer is i The amount of gas permeating through the liner dQ 1 , the amount of gas permeating through the reinforcement layer dQ 2The amount of gas entering the air from the outer protective layer dQ 3 The difference between is determined (as shown in Formula 2):

[0084]

[0085] Where: Q is the gas permeation; P 1 is the critical gas operating pressure; P i is the pore permeability pressure of the enhanced layer; 1 is the wall thickness of the lining layer; C 1 is the gas permeability coefficient of the lining layer; D 1 is the inner lining diameter; P o is the osmotic pressure of the outer interlayer; l 2 is the wall thickness of the reinforcement layer; C 2 is the gas permeability coefficient of the reinforcement layer; D 2 is the diameter of the reinforcement layer; P 2 is atmospheric pressure (0.1MPa); l 3 is the wall thickness of the outer protective layer; C 3 is the gas permeability coefficient of the outer protective layer; D 3 is the diameter of the outer protective layer; R is the molar gas constant; T is the pipeline operating temperature; V is the pore volume of the bonding composite pipe reinforcement layer.

[0086] The formula (2) is as follows:

[0087]

[0088] in:

[0089] Since the reinforcing layer is a fiber-reinforced thermoplastic composite material, its gas permeability coefficient is much smaller than that of the outer protective layer material. It can be inferred that the gas that slowly permeates through the reinforcing layer will quickly pass through the outer protective layer into the air. In this case, the outer interlayer (also pores or gaps) between the reinforcing layer and the outer protective layer is basically pressure-free, that is, P o = 0. Therefore, the calculation formula (3) is as follows:

[0090]

[0091] By formula (4), we can get:

[0092]

[0093] set up:

[0094]

[0095]

[0096] Then formula (4) is:

[0097]

[0098] When t = 0, P i =0, so E = C

[0099] Substituting the above parameters into the equation:

[0100]

[0101] in:

[0102] Example 1

[0103] Determine the delivery of CH at 30°C 4 The critical gas operating pressure for the collapse of the liner of the DN80mm bonded composite pipe (nylon liner + glass fiber reinforced polyethylene belt reinforcement layer + polyethylene outer protective layer) is as follows:

[0104] (1) Gas permeability coefficient test: Use the same raw materials as the nylon lining layer, glass fiber reinforced polyethylene tape reinforcement layer, and polyethylene outer protective layer to prepare a film (sheet) sample with a thickness of 0.1 mm to 0.5 mm. Set the test temperature to 30°C, refer to GB / T 1038, and use a gas permeometer to test CH 4 The permeability coefficient of gas in nylon, glass fiber reinforced polyethylene tape and polyethylene film (sheet) samples is C 1 , C 2 and C 3 .

[0105] (2) Establish the calculation formula of interlayer penetration pressure: As shown in formula (3), the wall thickness of the inner lining layer of DN80mm bonding composite pipe l 1 , Lining pipe diameter D 1 , reinforcement layer thickness l 2 , outer diameter of reinforcement layer D 2 , outer protective layer thickness l 3 , Outer protective layer pipe diameter D 3 , in C 1 , C 2 , C 3 When the parameters such as R (molar gas constant, known), T (pipeline operating temperature 303K), and V (pore volume of the reinforcement layer) can be tested or calculated, the pore permeability pressure (P i ) and critical gas operating pressure (P 1 ) can be derived from formula (3): That is, the pore permeability pressure (P i ) is related to the critical gas operating pressure (P1 ) and running time (t).

[0106] (3) Nylon lined pipe radial collapse pressure test: Cut a 1200 mm long bonded composite pipe and take out the nylon lined pipe. Apply hot melt adhesive evenly to the outer surface of the nylon lined pipe and insert it into a steel base pipe of matching size according to the traditional internal insertion process. Pass hot steam into the nylon lined pipe and heat it under pressure to melt the hot melt adhesive. Then, bond the nylon lined pipe and the steel pipe together to prepare a nylon lined composite steel pipe test sample. After machining and cutting off about 15 mm to 30 mm of the steel base pipe at both ends, open a water inlet in the middle of the steel base pipe layer of the nylon lined steel pipe test sample, and open a pressure sensor connection port perpendicular to the water inlet. Design and install a sealing plug according to the specifications of the nylon lined pipe. Connect the transfer joint equipped with the air inlet valve, pressure relief valve and pressure gauge to the sealing plug, then insert the flange plate, and use the fastening screw to fasten the flange plates at both ends of the test sample. Place the entire test sample on the support and push it into the environmental test chamber. Control the environmental test chamber to 30°C and start the environmental simulation test timing. After the set test time (such as 168h) is reached, stop the environmental simulation test. Keep the test sample in the environmental test chamber and keep the temperature at 30°C, connect the interlayer pressurization system and the interlayer pressure monitoring system. Turn on the pressure pump, pressurize the interlayer at a rate of 0.2MPa / s, and record the interlayer pressure changes. When the interlayer pressure appears as follows Figure 3 When the pressure changes as shown, stop pressing. The inflection point of the pressure change curve is the collapse pressure P of the nylon lining layer of the bonded composite pipe at 30°C. c .

[0107] (4) Calculation of critical gas operating pressure for collapse of nylon liner pipe: When the pore permeability pressure of the reinforcement layer (P i )>critical gas operating pressure (P 1 )+Nylon lining anti-collapse pressure (P c ), the liner collapses and fails. i =P 1 +P c At this time, we calculate that at 30°C, the transport CH 4 Critical gas operating pressure P for liner collapse of DN80mm bonded composite pipe (nylon liner + glass fiber reinforced polyethylene belt reinforcement layer + polyethylene outer protective layer) 1 .

[0108] Example 2

[0109] Tested at 60℃, delivering CO 2The critical gas operating pressure for the inner lining collapse of DN100mm bonded composite pipe (heat-resistant polyethylene inner lining + aramid fiber reinforced polyethylene tape + polyethylene outer protective layer) for gas and oil-water media is as follows:

[0110] (1) Gas permeability coefficient test: Use the same raw materials as the heat-resistant polyethylene liner, aramid fiber reinforced polyethylene tape, and polyethylene outer protective layer to prepare a film (sheet) sample with a thickness of 0.1 to 0.5 mm. Set the test temperature to 60°C, refer to GB / T1038, and use a gas permeometer to test CO 2 The permeability coefficient of gas in heat-resistant polyethylene, aramid fiber reinforced polyethylene tape, polyethylene film (sheet) samples is C 1 , C 2 and C 3 .

[0111] (2) Establish the calculation formula of interlayer penetration pressure: As shown in formula (3), the wall thickness of the inner lining layer of DN80mm bonding composite pipe is tested. 1 , Lining pipe diameter D 1 , reinforcement layer thickness l 2 , outer diameter of reinforcement layer D 2 , outer protective layer thickness l 3 , Outer protective layer pipe diameter D 3 , in C 1 , C 2 , C 3 When the parameters such as R (molar gas constant, known), T (pipeline operating temperature 333K), and V (pore volume of the reinforcement layer) can be tested or calculated, the pore permeability pressure (P i ) and critical gas operating pressure (P 1 ) can be derived from formula (3): That is, the pore permeability pressure (P i ) is related to the critical gas operating pressure (P 1 ) and running time (t).

[0112] (3) Radial collapse pressure test of heat-resistant polyethylene lined pipe: Cut a 1500mm long bonded composite pipe and take out the heat-resistant polyethylene lined pipe. Apply hot melt adhesive evenly on the outer surface of the heat-resistant polyethylene lined pipe and insert it into a steel pipe of matching size according to the traditional internal insertion process. Pass hot steam into the heat-resistant polyethylene lined pipe and heat it under pressure to melt the hot melt adhesive. Then, bond the heat-resistant polyethylene lined pipe and the steel pipe together to prepare a heat-resistant polyethylene lined composite steel pipe test sample. After machining and cutting off about 15 to 30mm of the steel base pipe at both ends, open a water inlet in the middle of the steel base pipe layer of the test sample and open a pressure sensor connection port perpendicular to the water inlet. Design and install a sealing plug according to the specifications of the DN100mm heat-resistant polyethylene lined pipe. Connect the transfer joint equipped with the air inlet valve, pressure relief valve and pressure gauge to the sealing plug. Install the connected sealing plug with the inner sealing ring and insert it into one end of the heat-resistant polyethylene lined pipe. Pour the prepared oil-water solution from the other end and seal it with the connected sealing plug. Then put on the flange and use the tightening screws to tighten the flanges at both ends of the test sample. Place the entire test sample filled with liquid medium on the support seat, push it into the environmental test chamber, and connect the motor's transmission belt to the transfer joint. Start the motor to drive the test sample to rotate, and at the same time control the environmental test chamber to heat up to 60°C, and start the environmental simulation test timing. After the set test time (such as 200h) is reached, stop the motor. Keep the test sample in the environmental test chamber and keep the temperature at 60°C, connect the interlayer pressurization system and the interlayer pressure monitoring system. Turn on the pressure pump, pressurize the interlayer at a rate of 0.3MPa / s, record the change in interlayer pressure, and when the interlayer pressure appears as follows Figure 3 When the pressure changes as shown, stop pressing. The inflection point of the pressure change curve is the collapse pressure P of the heat-resistant polyethylene lining layer of the DN100mm bonded composite pipe at 60℃. c .

[0113] (4) Calculation of critical gas operating pressure for collapse of heat-resistant polyethylene liner pipe: When the pore permeability pressure of the reinforcement layer (P i )>critical gas operating pressure (P 1 )+Heat-resistant polyethylene liner pipe anti-collapse pressure (P c ), the liner collapses and fails. i =P 1 +P c Calculate this time and get the transport CH at 60℃. 4 Critical gas operating pressure P for liner collapse of DN100mm bonded composite pipe (nylon liner + glass fiber reinforced polyethylene belt reinforcement layer + polyethylene outer protective layer) 1 .

[0114] Example 3

[0115] Test and confirm the oil, water and CH transport at 40℃ and 4MPa operating pressure 4 After 10 years, is there a risk of collapse and failure of the inner lining of the DN150mm bonded composite pipe (cross-linked polyethylene inner lining + glass fiber reinforced polyethylene tape + polyethylene outer protective layer)? The details are as follows:

[0116] (1) Gas permeability coefficient test: Use the same raw materials as the cross-linked polyethylene liner, glass fiber reinforced polyethylene tape, and polyethylene outer protective layer to prepare a film (sheet) sample with a thickness of 0.1 to 0.5 mm. Set the test temperature to 40°C, refer to GB / T1038, and use a gas permeometer to test CH 4 The permeability coefficient of gas in cross-linked polyethylene, glass fiber reinforced polyethylene tape, polyethylene film (sheet) samples is C 1 , C 2 and C 3 .

[0117] (2) Establish the calculation formula of interlayer penetration pressure: As shown in formula (3), the wall thickness of the inner lining layer of the DN150mm bonding composite pipe is tested. 1 , Lining pipe diameter D 1 , reinforcement layer thickness l 2 , outer diameter of reinforcement layer D 2 , outer protective layer thickness l 3 , Outer protective layer pipe diameter D 3 , in C 1 , C 2 , C 3 When the parameters such as R (molar gas constant, known), T (pipeline operating temperature 313K), and V (pore volume of the reinforcement layer) can be tested or calculated, the pore permeability pressure (P i ) and critical gas operating pressure (P 1 ) can be derived from formula (3): That is, the pore permeability pressure (P i ) is related to the critical gas operating pressure (P 1 ) and running time (t).

[0118] (3) Radial collapse pressure test of cross-linked polyethylene lined pipe: Cut a 2000mm long bonding composite pipe and take out the cross-linked hot polyethylene lined pipe. Apply hot melt adhesive evenly on the outer surface of the cross-linked polyethylene lined pipe and insert it into a steel pipe of matching size according to the traditional internal insertion process. Pass hot steam into the cross-linked polyethylene lined pipe and heat it under pressure to melt the hot melt adhesive. Then, the cross-linked polyethylene lined pipe and the steel pipe are bonded together to prepare a cross-linked polyethylene lined composite steel pipe test sample. After machining and cutting off about 15 to 30mm of the steel base pipe at both ends, a water inlet is opened in the middle of the steel base pipe layer of the test sample, and a pressure sensor connection port is opened perpendicular to the water inlet. Design and install a sealing plug according to the specifications of the DN150mm cross-linked polyethylene lined pipe. Connect the transfer joint equipped with the air inlet valve, pressure relief valve and pressure gauge to the sealing plug. Install the connected sealing plug with the inner sealing ring and insert it into one end of the cross-linked polyethylene lined pipe. Pour the prepared oil-water solution from the other end and seal it with the connected sealing plug. Then insert the flange and use the tightening screw to tighten the flanges at both ends of the test sample. 4 Gas cylinder to the transfer joint, close the pressure relief valve, open the air inlet valve, and increase the pressure to 4MPa. After closing the air inlet valve, place the entire test sample filled with liquid medium and maintaining a certain internal pressure on the support seat, push it into the environmental test chamber, and connect the motor's conveyor belt to the transfer joint. Start the motor to drive the test sample to rotate, and at the same time control the temperature of the environmental test chamber to 40°C. After reaching the set test time (such as 240h), stop the motor and open the pressure relief valve to release the internal gas pressure of the test sample. Keep the test sample in the environmental test chamber and keep the temperature at 40°C, connect the interlayer pressurization system and the interlayer pressure monitoring system. Turn on the pressure pump to pressurize the interlayer at a rate of 0.3MPa / s, record the change in interlayer pressure, and when the interlayer pressure appears as follows Figure 3 When the pressure changes as shown, stop pressurizing. The inflection point of the pressure change curve is 40℃, 4MPa operating pressure for transporting oil, water and CH 4 Radial collapse pressure P of cross-linked polyethylene lined pipe under gas conditions c .

[0119] (4) Collapse failure risk prediction of cross-linked polyethylene liner pipe: In calculating and determining the pore permeability pressure (P i ) and tested the collapse pressure of cross-linked polyethylene lined pipe (P c ), if P i -P c > Pipeline operating pressure (4MPa), it can be determined that at 40℃ and 4MPa operating pressure, oil, water and CH 4After 10 years, the inner lining of DN150mm bonded composite pipe (cross-linked polyethylene inner lining + glass fiber reinforced polyethylene tape + polyethylene outer protective layer) has the risk of collapse and failure; on the contrary, if P i -P c ≤ pipeline operating pressure (4MPa), it can be determined that there is no risk of collapse failure.

[0120] Finally, it should be noted that the above-described embodiments are only specific implementations of the present invention, which are used to illustrate the technical solutions of the present invention, rather than to limit them. The protection scope of the present invention is not limited thereto. Although the present invention is described in detail with reference to the above-described embodiments, ordinary technicians in the field should understand that any technician familiar with the technical field can still modify the technical solutions recorded in the above-described embodiments within the technical scope disclosed by the present invention, or can easily think of changes, or make equivalent replacements for some of the technical features therein; and these modifications, changes or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A method for determining the critical gas operating pressure for the collapse of the bonded composite pipe lining. It is characterized in that include: Obtaining the porosity volume of the reinforcement layer of the bonded composite pipe, the operating temperature of the bonded composite pipe, the operating time of the bonded composite pipe, and the transport gas component of the bonded composite pipe; According to the operating temperature and the transported gas component, the gas permeability coefficient of the inner lining layer of the bonded composite pipe, the gas permeability coefficient of the reinforcement layer of the bonded composite pipe and the gas permeability coefficient of the outer protective layer of the bonded composite pipe are respectively tested; The pore volume of the reinforcement layer, the operating temperature, the operating time, the gas permeability coefficient of the lining layer, the gas permeability coefficient of the reinforcement layer and the gas permeability coefficient of the outer protective layer are input into a pre-constructed pore permeability pressure model of the reinforcement layer of the bonding type composite pipe to obtain the pore permeability pressure of the reinforcement layer of the bonding type composite pipe; the pore permeability pressure model of the reinforcement layer is specifically: in, Where, P i is the pore osmotic pressure of the reinforcement layer; P 1 is the critical gas operating pressure; P 2 is the atmospheric pressure; R is the molar gas constant; T is the pipeline operating temperature; V is the pore volume of the reinforcement layer of the bonded composite pipe; l 1 is the wall thickness of the inner lining layer; C 1 is the gas permeability coefficient of the inner lining layer; D 1 is the diameter of the inner lining layer; l 2 is the wall thickness of the reinforcement layer; C 2 is the gas permeability coefficient of the reinforcement layer; D 2 is the diameter of the reinforcement layer; l 3 is the wall thickness of the outer protective layer; C 3 is the gas permeability coefficient of the outer protective layer; D 3 is the diameter of the outer protective layer; t is the operating time; Determining the radial collapse pressure of the inner lining layer of the bonded composite pipe; The pore permeability pressure of the reinforcement layer and the radial collapse pressure of the lining layer are input into a pre-constructed critical collapse failure criterion model to obtain the critical gas operating pressure of the bonded composite pipe liner collapse; the critical collapse failure criterion model is specifically: P i =P 1 +P c Where P c It is the radial collapse pressure of the inner lining of the bonded composite pipe.

2. According to claim 1, a method for determining the critical gas operating pressure for the collapse of the bonding type composite pipe liner, It is characterized in that The gas permeability coefficient of the inner lining layer of the bonded composite pipe, the gas permeability coefficient of the reinforcement layer of the bonded composite pipe and the gas permeability coefficient of the outer protective layer of the bonded composite pipe are tested respectively according to the operating temperature and the transported gas component, specifically including: A first thermoplastic plastic film sample is prepared from the same raw material as the inner lining layer of the bonding type composite pipe, a second thermoplastic plastic film sample is prepared from the same raw material as the reinforcing layer of the bonding type composite pipe, and a third thermoplastic plastic film sample is prepared from the same raw material as the outer protective layer of the bonding type composite pipe; The gas permeability test temperature is set to the operating temperature, and a gas permeability meter is used to test the gas permeability coefficient of the transported gas component in the first thermoplastic plastic film sample, which is the gas permeability coefficient of the inner lining layer of the bonding type composite pipe; the gas permeability coefficient of the transported gas component in the second thermoplastic plastic film sample is tested, which is the gas permeability coefficient of the bonding type composite pipe reinforcement layer; the gas permeability coefficient of the transported gas component in the third thermoplastic plastic film sample is tested, which is the gas permeability coefficient of the outer protective layer of the bonding type composite pipe.

3. A method for determining the critical gas operating pressure for collapse of a bonded composite pipe liner according to claim 2, It is characterized in that The preparation process of the first thermoplastic plastic film sample is the same as the preparation process of the bonding type composite pipe lining layer; The preparation process of the second thermoplastic plastic film sample is the same as the preparation process of the bonding type composite pipe reinforcement layer; The preparation process of the third thermoplastic plastic film sample is the same as the preparation process of the outer protective layer of the bonding composite pipe.

4. According to claim 1, a method for determining the critical gas operating pressure for the collapse of the bonding type composite pipe liner, It is characterized in that Determining the radial collapse pressure of the inner lining layer of the bonding type composite pipe specifically includes: Conduct environmental simulation tests on bonded composite pipe test samples; Conduct radial pressure test on the inner lining layer of the bonded composite pipe test sample, and record the pressure change between the reinforcement layer and the inner lining layer of the bonded composite pipe sample; According to the change of the interlayer pressure between the reinforcement layer and the inner lining layer of the bonded composite pipe sample, a pressure change curve between the reinforcement layer and the inner lining layer of the bonded composite pipe sample is drawn; The radial collapse pressure of the inner lining layer of the bonding type composite pipe is obtained according to the pressure variation curve.

5. A method for determining the critical gas operating pressure for collapse of a bonded composite pipe liner according to claim 4, It is characterized in that When the radial pressure test is performed on the inner lining layer of the bonded composite pipe test sample, the pressure rate is controlled at 0.1 MPa / s to 0.5 MPa / s.

6. The method for determining the critical gas operating pressure for the collapse of the bonded composite pipe liner according to claim 1, It is characterized in that The porosity volume of the reinforcement layer is obtained by testing using the Archimedes drainage method.

7. The method for determining the critical gas operating pressure for the collapse of the bonded composite pipe liner according to claim 1, It is characterized in that When there is fluctuation or negative pressure in the operating pressure of the bonded composite pipe, the radial collapse pressure should be corrected with a correction factor of 0.5 to 0.8.

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