Composite pipe connector and method of connecting the same

Abstract

The application discloses a composite pipe connector and a connecting method thereof, which comprises a composite pipe, an outer taper sleeve, a taper pad, and an inner fixing cylinder. The outer wall of the composite pipe is provided with the taper pad. The taper pad comprises an elastic ring pad, a metal snap ring, and a slip. The elastic ring pad is located on the side far from the port of the composite pipe. The slip has a double-tapered segment structure. The end of the slip close to the elastic ring pad has a small taper angle, and the end of the slip far from the elastic ring pad has a large taper angle. The metal snap ring is located on the side close to the port of the composite pipe and is in interference fit with the composite pipe. The outer part of the taper pad is provided with the outer taper sleeve. The side of the outer taper sleeve far from the port of the composite pipe is in contact with the elastic ring pad. The side of the outer taper sleeve close to the port of the composite pipe is provided with a first flange structure. The inner fixing cylinder comprises a second flange and an inner cylinder. The second flange is located at the front end of the inner fixing cylinder. The second flange is connected with the first flange through a fastening bolt. The outer surface of the inner cylinder is in contact with the inner surface of the composite pipe. The components of the application can be disassembled and replaced. The sealing effect is good. The application is suitable for the connection of medium-high pressure and large-diameter pipelines.

Description

Technical Field

[0001] This invention relates to the field of pipe connection equipment technology, and in particular to a composite pipe connector and its connection method. Background Technology

[0002] Composite pipes, also known as fiber-reinforced composite pipes, are typically made of an inner layer of reinforcing fibers and an outer layer of polymer material. Composite pipes are flexible and can be coiled, with a smoother surface and low fluid friction, making them particularly suitable for fluid transportation in oil and gas production. Compared with traditional metal pipes, they are easier to install and maintain, and composite pipes have become an important pipe material for oil and gas production.

[0003] In oil and gas production, composite pipes may be exposed to complex corrosive chemicals and harsh conditions. The loads on the pipes caused by external pressure, internal pressure, and tension or compression can be extremely high, and the composite pipes must be able to withstand these conditions. Composite pipe materials are mainly made of polymers. During oil and gas transportation, small molecule gases in the oil and gas, such as CH4, inevitably seep into the pipe interior. If they accumulate in secondary forming areas such as fiber winding, it will cause pipe delamination and lead to pipe failure. Pipe joints, as terminal connection devices in pipeline systems, are important structures in pipeline systems and also the most prone to failure. They are mainly used to connect pipelines to other devices, seal the transported medium inside the pipeline, and prevent pipe pull-out.

[0004] Non-metallic pipe connection methods generally fall into two main categories: mechanical crimping connections and reinforced hot-melt sleeve connections. The hot-melt connection methods specified in "GBT20674.1-2020 Plastic Pipes and Fittings - Polyethylene System Welding Equipment - Part 1: Hot Melt Butt Connection" and "GBT32434-2015 Plastic Pipes and Fittings - Polyethylene (PE) Pipes and Fittings for Gas and Water Supply Distribution Systems" involve thermally fusing the pipe and fitting structure. This method is suitable for small-diameter, low-pressure oil and gas transportation environments, primarily used in water and oil transportation, as well as urban gas (below 1.6 MPa) pipelines. However, its application in large-diameter, high-pressure oil and gas pipelines suffers from shortcomings in strength, axial force transmission, and sealing. The specifications in "SY T6662.6-2014 Non-metallic Composite Pipes for Oil and Gas Industry Part 6: Flexible Composite Continuous Pipes and Joints for Downhole Use", "SY T6662.7-2016 Non-metallic Composite Pipes for Oil and Gas Industry Part 7: Thermoplastic Plastic Lined Fiberglass Composite Pipes", and "SY T6769.5-2016 Non-metallic Pipeline Design, Construction and Acceptance Specifications Part 5: Fiber Reinforced Thermoplastic Plastic Composite Continuous Pipes" provide the structure of mechanical crimping joints. Mechanical crimping connections have the following problems: (1) Mechanical crimping joints are also prone to strength failure under complex load conditions; (2) Sealing performance problems: Mechanical crimping sealing method is singular and cannot compensate for the creep and thermal expansion and contraction of the inner and outer layers of the composite pipe polymer material, resulting in low sealing reliability; (3) Prestress retention problems: Mechanical crimping joints ensure the limit of the pipeline through prestress, but often in actual environment In particular, the prestress is lost after the structure undergoes fatigue deformation or creep, which leads to a decrease in the load-bearing capacity of the pipeline and a decrease in the sealing performance; (4) Joint installation and removal problems: Mechanical crimping joints are one-time joints and cannot be replaced after assembly. The whole piece needs to be replaced; (5) Pipeline layer damage problems: Mechanical crimping connectors have large installation errors. The mechanical crimping joint structure is prone to stress concentration on the pipeline layer. The connection part is overloaded, and the pipeline structure is prone to damage. In practice, this manifests as the bursting of the joint part and leakage of the connection part in the burst test; (6) Small molecule gas in the pipeline transport medium penetrates into the pipe material. Summary of the Invention

[0005] In order to overcome the above-mentioned problems in the prior art, the present invention proposes a composite tube connector and its connection method.

[0006] The technical solution adopted by this invention to solve its technical problem is as follows: a composite pipe connector, comprising a composite pipe, an outer conical sleeve, a conical pad, and an inner fixed cylinder. The outer wall of the composite pipe is provided with a conical pad, which includes an elastic ring pad, a metal retaining ring, and a retaining slip. The elastic ring pad is located on the side away from the port of the composite pipe. The retaining slip has a double-conical segment structure, with a small cone angle at the end near the elastic ring pad and a large cone angle at the end away from the elastic ring pad. The metal retaining ring is located on the side near the port of the composite pipe and is interference-fitted with the composite pipe. An outer conical sleeve is provided outside the conical pad, and the side of the outer conical sleeve away from the port of the composite pipe contacts the elastic ring pad. The middle part of the outer conical sleeve has a double-conical segment structure that matches the shape of the retaining slip. A first flange structure is provided on the side of the outer conical sleeve near the port of the composite pipe. The inner fixed cylinder includes a second flange and an inner cylinder. The second flange is located at the front end of the inner fixed cylinder and is connected to the first flange by fastening bolts. A metal ring pad is installed between the first flange and the second flange. The outer surface of the inner cylinder contacts the inner surface of the composite pipe.

[0007] The aforementioned composite tube connector comprises, from the inside out, an inner layer, a reinforcing layer, and an outer layer. The inner layer is made of a thermoplastic polymer material, the reinforcing layer is formed by winding reinforcing material, and the outer layer is made of a weather-resistant modified polymer.

[0008] In the aforementioned composite tube connector, the slip is a multi-piece structure, the inner surface of the slip is sandblasted or knurled, and the slip is bonded to the outer wall of the composite tube by an adhesive.

[0009] In the aforementioned composite pipe connector, the thickness of the metal retaining ring is the same as the maximum thickness of the retaining plate.

[0010] In the aforementioned composite tube connector, the collet is provided with a reinforcing rib on the side near the composite tube, and a groove for fixing the reinforcing rib is provided at a corresponding position on the outer surface of the composite tube.

[0011] In the aforementioned composite tube connector, the inner surface of the metal retaining ring, the inner surface of the retaining plate, and the outer surface of the inner cylinder are all provided with reverse teeth.

[0012] In the aforementioned composite pipe connector, the outer surface of the slip is provided with an elastomer ring fastening groove.

[0013] In the aforementioned composite pipe connector, the first flange is a standard flange, and the second flange is an integral steel flange with a ring connection surface.

[0014] In the aforementioned composite pipe connector, the pressure rating of the second flange is the same as the design pressure of the composite pipe.

[0015] The formula for calculating the inner cylinder wall thickness of the aforementioned composite pipe connector is as follows:

[0016]

[0017] Where P is the design pressure of the composite pipe; D O [σ] is the outer diameter of the pipe; [σ] is the allowable stress of the material used for the inner fixed cylinder at the design temperature; E I , where is the welding joint coefficient, and 1 is taken for no weld; Y is the material temperature correction coefficient; C1 is the thickness reduction allowance; C2 is the corrosion or abrasion allowance; C3 is the tooth pattern machining depth.

[0018] In the aforementioned composite tube connector, sealing ring mounting grooves are also provided at both ends of the inner cylinder.

[0019] In the aforementioned composite tube connector, the inner surface of the metal retaining ring and the outer surface of the inner cylinder are both treated with sandblasting or knurling.

[0020] In the aforementioned composite pipe connector, an exhaust channel is provided on the first flange corresponding to the side of the metal ring gasket near the metal retaining ring.

[0021] In the aforementioned composite pipe connector, the large cone angle of the slip is 3-6°, and the small cone angle of the slip is 1-3°.

[0022] The connection method of any of the above-mentioned composite tube connectors includes the following steps:

[0023] Step 1: Apply lubricant to the inner surface of the outer conical sleeve, insert the composite tube into the outer conical sleeve from the end, and place the outer conical sleeve at the end away from the end of the composite tube;

[0024] Step 2: Determine the pipe connection length, install an elastic ring gasket at the end furthest from the composite pipe, heat the metal retaining ring to the design temperature of the composite pipe, and fix the metal retaining ring to the end of the composite pipe.

[0025] Step 3: Apply lubricant to the outer surface of the inner cylinder, heat the composite tube to the design temperature of the composite tube, and use hydraulic tools to press the inner cylinder into the interior of the composite tube;

[0026] Step 4: Install the slips between the elastic ring gasket and the metal retaining ring on the outer wall of the composite pipe. After the slips are installed, use hydraulic tools to mechanically compress the metal retaining ring.

[0027] Step 5: Apply lubricant to the outer surface of the slip, pull the outer cone sleeve from the side away from the end of the composite pipe to the end of the composite pipe, install a metal ring gasket between the first flange and the second flange, and connect and tighten the first flange and the second flange with fastening bolts.

[0028] In the above-described method for connecting a composite pipe connector, the formula for calculating the pipe connection length L in step 2 is as follows:

[0029]

[0030] Where P is the design pressure of the composite pipe; D O d is the outer diameter of the composite pipe; d is the inner diameter of the composite pipe. t is the coefficient of friction between the slip and the composite pipe; t is the wall thickness of the composite pipe. The length of the elastic ring gasket is 0.5 times the outer diameter of the composite pipe; The length of the metal retaining ring is 0.5 times the outer diameter of the composite pipe; The contact pressure between the valve and the composite pipe is taken as three times the design pressure of the composite pipe.

[0031] In the above-mentioned method for connecting a composite pipe connector, when the calculated pipe connection length is less than the total composite pipe length but not less than twice the outer diameter of the composite pipe, the pipe connection length is taken as twice the outer diameter of the composite pipe.

[0032] The beneficial effects of the present invention are: (1) Through the self-tightening structure, the deformation caused by the creep and thermal expansion and contraction of the inner and outer layers of the composite pipe polymer material is compensated, which solves the problem of the single sealing method and low reliability of the mechanical pressing joint box heat fusion joint.

[0033] (2) The stress is uniform in all parts of the pipe joint and the stress changes smoothly, which reduces the stress concentration in the mechanical clamping part of the pipe and solves the connection failure problem caused by damage to the composite pipe.

[0034] (3) The connector and composite tube have small deformation and little damage to the composite tube. The components of the connector can be easily disassembled from the composite tube, which solves the problem that the composite tube connector cannot be replaced after assembly and can only be replaced as a whole.

[0035] (4) Using a multi-cone metal cone cylinder + elastic ring gasket, the pipe joint is subjected to uniform force and the contact surface between the connector and the composite pipe is large, which can allow relative movement between the composite pipe connector and the composite pipe to a certain extent. This solves the complex load transmission problems such as the axial force formed by the axial tension and compression of the composite pipe at the pipe joint, the torque formed by the torsion of the composite pipe at the pipe joint, and the bending moment formed by the bending of the composite pipe at the pipe joint, thereby improving the ability of the pipe to withstand axial force.

[0036] (5) The multi-piece conical pad design can better adapt to the wall thickness deviation, diameter deviation, and eccentricity of the composite pipe, thus solving the applicability problem of composite pipes with different diameters and materials;

[0037] (6) A venting channel for gas seepage into the composite pipe is provided at the pipe end, which solves the problem of gas seepage into the interior of the composite pipe and causing interlayer damage to the composite pipe during long-term use.

[0038] (7) The outermost seal of the triple sealing structure adopts a metal ring gasket seal. The inside of the ring gasket is connected to the leakage monitoring device through a microchannel, which solves the problem of leakage monitoring at the pipe joint.

[0039] (8) Composite pipes have low requirements for form and position tolerances and are suitable for medium and high pressure large diameter pipe connections. Attached Figure Description

[0040] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0041] Figure 1 This is a schematic diagram of the present invention;

[0042] Figure 2 This is a schematic diagram of the cone pad of the present invention;

[0043] Figure 3 This is a schematic diagram of the outer cone sleeve of the present invention;

[0044] Figure 4 This is a schematic diagram of the inner fixing cylinder of the present invention.

[0045] In the diagram: 1. Outer conical sleeve; 1-1. First flange; 1-2. First fastening bolt mounting hole; 1-3. First metal ring gasket mounting groove; 1-4. Exhaust channel; 2. Conical gasket; 2-1. Elastic ring gasket; 2-2. Metal retaining ring; 2-3. Slip; 2-4. Elastic ring fastening groove; 2-5. Reinforcing rib; 3. Composite pipe; 4. Inner fixed cylinder; 4-1. Second fastening bolt mounting hole; 4-2. Second metal ring gasket mounting groove; 4-3. Elastic sealing ring mounting groove; 4-4. Backtooth pattern; 4-5. Inner cylinder; 4-6. Second flange; 5. O-ring seal; 6. Metal ring gasket; 7. Fastening bolt. Detailed Implementation

[0046] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0047] This embodiment discloses a composite tube connector, such as Figure 1 As shown, it includes an outer conical sleeve 1 for clamping and limiting the displacement of the composite tube 3, a conical pad 2 placed on the outer wall of the composite tube, an inner fixing cylinder 4 placed inside the composite tube, a metal ring pad 6, an O-ring seal 5, and a fastening bolt 7 for connecting the inner fixing cylinder 4 and the outer conical sleeve 1.

[0048] like Figure 2As shown, the cone pad 2 is disposed on the outer wall of the composite pipe 3, including an elastic ring pad 2-1, a metal retaining ring 2-2, and a slip 2-3. The elastic ring pad 2-1 is located at the far end of the port of the composite pipe 3, so that the stress acting on the composite pipe 3 is smoothly transferred, reducing the stress concentration on the pipe wall. The slip 2-3 has a double cone structure, in which the far end of the connector port has a small cone angle and the near end has a large cone angle. The slip has a multi-piece structure, and the inner surface is sandblasted or knurled to increase the friction between the composite pipe and the cone pad. At the same time, it can be evenly bonded to the outer wall of the composite pipe with adhesive. The inner surface of the slip is also provided with reverse teeth and reinforcing ribs 2-5, and the outer surface of the slip is provided with an elastic ring fastening groove. 2-4 is used for the fixed installation of slip 2-3; the metal retaining ring 2-2 is located at the end of the composite pipe and is fitted with the composite pipe 3 using a basic shaft transition fit to ensure full contact between the metal retaining ring 2-2 and the outer wall of the composite pipe 3; the thickness of the metal retaining ring 2-2 is the same as the maximum thickness of slip 2-3, and the inner surface is provided with reverse teeth. It is sandblasted or knurled to increase the contact area between the metal retaining ring 2-2 and the composite pipe 3; the metal retaining ring 2-2 can be mechanically squeezed to form an interference fit between the metal retaining ring 2-2 and the composite pipe 3, so that the part forms a seal with the greatest stress.

[0049] like Figure 3 As shown, the outer conical sleeve 1 is placed outside the conical pad 2. The end of the outer conical sleeve 1 away from the composite pipe port is a cylindrical structure, which contacts the elastic ring pad 2-1 of the conical pad, forming an elastic seal with low contact stress between the composite pipe 3 and the connector. The middle part is a double conical section structure, where the conical section away from the composite pipe port has a small cone angle and the conical section near the composite pipe port port has a large cone angle, which contacts the slip 2-3 to form a self-tightening stress gradient seal. The end near the composite pipe port port is the first flange 1-1, which is a standard flange structure. The first flange 1-1 is provided with a first metal ring pad mounting groove 1-3 and a first fastening bolt mounting hole 1-2. The first metal ring pad mounting groove 1-3 near the composite pipe 3 is provided with an exhaust channel 1-4 that connects the space of the composite pipe end in the metal ring pad 6 to the outside of the pipe connector. This is used to monitor whether the pipe connector is leaking and to provide an escape channel for the gas that has seeped into the composite pipe 3, avoiding damage to the pipe body caused by the accumulation of gas inside the composite pipe.

[0050] The composite pipe comprises an inner layer, a reinforcing layer, and an outer layer. The inner layer is made of thermoplastic polymer material through a plastic extrusion process and can consist of multiple layers of thermoplastic polymer material with different functions. The reinforcing layer is made of non-metallic or metallic reinforcing materials wound around the inner layer using a specific winding process. It is used to reinforce the pipe wall and can withstand axial tension and circumferential tension. The non-metallic reinforcing material used in the reinforcing layer is thermoplastic fiber prepreg tape or fibers with a surface treatment compatible with the inner layer material. The outer layer is made of weather-resistant modified polymer and is extruded around the wound reinforcing layer to protect the composite pipe's reinforcing layer from damage caused by external forces. The outer layer surface has grooves that mate with the reinforcing ribs 2-5 of the slips.

[0051] like Figure 4 As shown, the inner fixed cylinder includes a second flange 4-6 connected to the outer conical sleeve and an inner cylinder 4-5 that forms a seal with the inner wall of the composite pipe. The second flange 4-6 is an integral steel flange with a ring connection surface, and its pressure rating is the same as the design pressure of the composite pipe. The second flange 4-6 is provided with a second metal ring gasket mounting groove 4-2 and a second fastening bolt mounting hole 4-1. The wall thickness of the inner cylinder 4-5 is... The outer diameter and wall thickness are controlled according to ASME B31.3, GB150, and GB50253 standards. Designed by the following formula:

[0052]

[0053] Where P is the design pressure of the composite pipe; D O [σ] represents the outer diameter of the pipe; [σ] represents the allowable stress of the material used for the inner fixed cylinder at the design temperature. , where is the welding joint coefficient, and 1 is taken for no weld; Y is the material temperature correction coefficient; C1 is the thickness reduction allowance; C2 is the corrosion or abrasion allowance; C3 is the tooth pattern machining depth.

[0054] The outer surface of the inner cylinder is sandblasted or knurled to increase friction between the composite pipe's inner wall and the fixed cylinder, improving the load-bearing capacity of the pipe joint. The inner cylinder surface has reverse serrations 4-4, with a tooth height of 0.3-0.5mm, to prevent the composite pipe from detaching from the connector. The inner cylinder also has four elastomer sealing ring mounting grooves 4-3 for placing O-rings 5 ​​with outer diameter controlled according to GBT3452 "Hydraulic and Pneumatic O-rings". The outer diameter of the O-ring 5 is 0.5-1% larger than the inner diameter of the composite pipe, and the depth of the elastomer sealing ring mounting grooves 4-3 is equal to the diameter of the sealing ring cross-section. ~ This ensures that the sealing ring does not detach from the mounting groove during installation in the inner fixed cylinder and maintains tight contact with the inner wall of the composite pipe. The connector can be connected to other equipment using various methods such as welding or flange connections. During composite pipe connector installation, the sealing ring forms a tight contact with the inner wall of the composite pipe, ensuring the airtightness of the connector. The O-ring 5 is made of an elastic polymer material suitable for pipeline materials and process conditions, such as polyetheretherketone (PEEK), polytetrafluoroethylene (PTFE), and modified nitrile rubber (NBR).

[0055] When installing the composite pipe connector, first apply lubricant to the inner surface of the outer conical sleeve 1, insert the composite pipe 3 into the outer conical sleeve 1 from the end, and place the outer conical sleeve 1 at the far end of the port of the composite pipe 3. Then, calculate the pipe connection section length L according to the following formula.

[0056]

[0057] Where P is the design pressure of the composite pipe; D O d is the outer diameter of the composite pipe; d is the inner diameter of the composite pipe. t is the coefficient of friction between the slip and the composite pipe; t is the wall thickness of the composite pipe. The length of the elastic ring gasket is 0.5 times the outer diameter of the composite pipe; The length of the metal retaining ring is 0.5 times the outer diameter of the composite pipe; The contact pressure between the slip and the composite pipe is taken as three times the design pressure of the composite pipe; when the calculated length is less than twice the outer diameter of the composite pipe (not less than twice the total length), L is taken as twice the outer diameter of the composite pipe. Install the elastic ring gasket 2-1, then heat the metal retaining ring 2-2 to the design temperature of the composite pipe to expand it, and fix it to the end of the composite pipe 3. Next, apply lubricant to the outer surface of the inner cylinder 4-5, heat the composite pipe 3 to the design temperature to expand its diameter, and use hydraulic tools to press the inner cylinder 4-5 into the composite pipe 3. The gap between the outer diameter of the inner cylinder and the inner diameter of the composite pipe is 0.1~0.4mm. After the inner cylinder 4-5 is installed in place, place the slip 2-3 on the outer wall of the composite pipe, place the reinforcing rib 2-5 into the corresponding groove, and set an elastic ring in the elastic ring fastening groove 2-4 to fix the slip. The metal retaining ring 2-2 is mechanically squeezed using hydraulic tools, causing it to neck and further increasing the contact pressure between the composite pipe 3, the metal retaining ring 2-2, and the inner fixed cylinder, thus improving its sealing performance. Lubricant is applied to the outer surface of the retaining ring, and a metal ring pad 6 is placed in the second metal ring pad mounting groove 4-2 or the first metal ring pad mounting groove 1-2. The outer cone sleeve 1 is pulled from the far end to the near end of the composite pipe port, and the outer cone sleeve 1 is moved towards the composite pipe port by tightening the bolt 7, so that the preload force acting on the bolt is converted into the clamping force applied to the cone pad, thereby forming a seal on the composite pipe body.

[0058] In composite pipe connectors, the stress distribution on the composite pipe can be divided into sections that gradually increase in stress. The first section is an elastic ring gasket section with relatively low stress, and the second section has a cone angle of 1~3. The distal end of the carva, the third segment has a cone angle of 3~6 degrees. The fourth section, near the collet, is a mechanically clamping section with a metal retaining ring. This forms a gradually stress-varying pipe connector for the composite pipe, reducing stress concentration at the distal connection point of the composite pipe and preventing damage caused by stress concentration at the distal end. When the composite pipe experiences slight axial movement relative to the connector, the friction between the inner fixed cylinder and the tapered sleeve and the composite pipe increases the clamping force of the collet section of the tapered sleeve, achieving a self-tightening effect. When the long-term fatigue properties of the material change, causing a decrease in the clamping force of the composite pipe connector, the pre-tightening force of the fastening bolt 7 can be adjusted during inspection and maintenance to compensate for the loss of pre-stress.

[0059] The composite pipe connector can be connected to other equipment or pipelines through various forms such as welding heads, flanges, clamps, unions, etc.

[0060] The above embodiments are merely exemplary embodiments of the present invention and are not intended to limit the present invention. The scope of protection of the present invention is defined by the claims. Those skilled in the art can make various modifications or equivalent substitutions to the present invention within its spirit and scope of protection, and such modifications or equivalent substitutions should also be considered to fall within the scope of protection of the present invention.

Claims

1. A composite tube connector, characterized in that: The system includes a composite pipe, an outer conical sleeve, a conical pad, and an inner fixed cylinder. The outer wall of the composite pipe is provided with a conical pad, which includes an elastic ring pad, a metal retaining ring, and a retaining slip. The elastic ring pad is located on the side away from the composite pipe port. The retaining slip has a double-conical structure, with a small cone angle at the end near the elastic ring pad and a large cone angle at the end away from the elastic ring pad. The metal retaining ring is located on the side near the composite pipe port and is interference-fitted with the composite pipe. An outer conical sleeve is provided outside the conical pad, and the side of the outer conical sleeve away from the composite pipe port contacts the elastic ring pad. The middle part of the outer conical sleeve has a double-conical structure that matches the shape of the retaining slip. A first flange structure is provided on the side of the outer conical sleeve near the composite pipe port. The inner fixed cylinder includes a second flange and an inner cylinder. The second flange is located at the front end of the inner fixed cylinder and is connected to the first flange by fastening bolts. A metal ring pad is installed between the first and second flanges. The outer surface of the inner cylinder contacts the inner surface of the composite pipe. The formula for calculating the inner cylinder wall thickness is as follows: Where P is the design pressure of the composite pipe; D O [σ] is the outer diameter of the composite pipe; [σ] is the allowable stress of the material used for the inner fixed cylinder at the design temperature; E I For welded joints, take 1; Y is the material temperature correction factor; C1 is the thickness reduction allowance; C2 is the corrosion or abrasion allowance; C3 is the tooth pattern machining depth. The large cone angle of the kava is 3-6°, and the small cone angle of the kava is 1-3°.

2. A composite tube connector according to claim 1, characterized in that, The composite tube consists of an inner layer, a reinforcing layer, and an outer layer from the inside out. The inner layer is made of a thermoplastic polymer material, the reinforcing layer is formed by winding reinforcing material, and the outer layer is made of a weather-resistant modified polymer.

3. A composite tube connector according to claim 1, characterized in that, The slip is a multi-piece structure, and the inner surface of the slip is treated with sandblasting or knurling. The slip is bonded to the outer wall of the composite pipe with an adhesive.

4. A composite tube connector according to claim 1, characterized in that, The thickness of the metal retaining ring is the same as the maximum thickness of the retaining clip.

5. A composite tube connector according to claim 1, characterized in that, The clasp has a reinforcing rib on the side near the composite pipe, and a groove for fixing the reinforcing rib is provided on the corresponding position on the outer surface of the composite pipe.

6. A composite tube connector according to claim 1, characterized in that, The inner surface of the metal retaining ring, the inner surface of the retaining plate, and the outer surface of the inner cylinder are all provided with reverse teeth.

7. A composite tube connector according to claim 1, characterized in that, The outer surface of the slip is provided with an elastic ring fastening groove.

8. A composite tube connector according to claim 1, characterized in that, The first flange is a standard flange, and the second flange is an integral steel flange with a ring connection surface.

9. A composite tube connector according to claim 1, characterized in that, The pressure rating of the second flange is the same as the design pressure of the composite pipe.

10. A composite tube connector according to claim 1, characterized in that, The inner cylinder is also provided with sealing ring mounting grooves at both ends.

11. A composite tube connector according to claim 1, characterized in that, The inner surface of the metal retaining ring and the outer surface of the inner cylinder are both treated with sandblasting or knurling.

12. A composite tube connector according to claim 1, characterized in that, An exhaust channel is provided on the first flange corresponding to the side of the metal ring gasket near the metal retaining ring.

13. A connection method based on any one of the composite tube connectors according to claims 1-12, characterized in that: Includes the following steps: Step 1: Apply lubricant to the inner surface of the outer conical sleeve, insert the composite tube into the outer conical sleeve from the end, and place the outer conical sleeve at the end away from the end of the composite tube; Step 2: Determine the pipe connection length, install an elastic ring gasket at the end furthest from the composite pipe, heat the metal retaining ring to the design temperature of the composite pipe, and fix the metal retaining ring to the end of the composite pipe. Step 3: Apply lubricant to the outer surface of the inner cylinder, heat the composite tube to the design temperature of the composite tube, and use hydraulic tools to press the inner cylinder into the interior of the composite tube; Step 4: Install the slips between the elastic ring gasket and the metal retaining ring on the outer wall of the composite pipe. After the slips are installed, use hydraulic tools to mechanically compress the metal retaining ring. Step 5: Apply lubricant to the outer surface of the slip, pull the outer cone sleeve from the side away from the end of the composite pipe to the end of the composite pipe, install a metal ring gasket between the first flange and the second flange, and connect and tighten the first flange and the second flange with fastening bolts.

14. The connection method of a composite tube connector according to claim 13, characterized in that: The formula for calculating the pipe connection length L in step 2 is as follows: Where P is the design pressure of the composite pipe; D O d is the outer diameter of the composite pipe; d is the inner diameter of the composite pipe. t is the coefficient of friction between the slip and the composite pipe; t is the wall thickness of the composite pipe. The length of the elastic ring gasket is 0.5 times the outer diameter of the composite pipe; The length of the metal retaining ring is 0.5 times the outer diameter of the composite pipe; The contact pressure between the valve and the composite pipe is taken as three times the design pressure of the composite pipe.

15. The connection method of a composite tube connector according to claim 14, characterized in that: When the calculated pipe connection length is less than the total composite pipe length but not less than twice the outer diameter of the composite pipe, the pipe connection length is taken as twice the outer diameter of the composite pipe.

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