Joint for non-metallic oil pipes, oil pipe and method for installing a joint

Abstract

The application provides a joint for non-metal oil pipe, an oil pipe and a method for installing the joint, the non-metal pipe body of the oil pipe comprises a tubular reinforcing layer and a tubular inner lining layer located in the reinforcing layer, the inner lining layer is tightly combined with the reinforcing layer, the joint for non-metal oil pipe comprises a joint body, one end of the joint body is provided with a connecting thread, a locking sleeve is tubular, the locking sleeve is sleeved outside the joint body and coaxial with the joint body, in the state that the joint body and the pipe body of the non-metal oil pipe are installed, a part of the inner wall of the locking sleeve is opposite to the outer wall of the joint body and is fixed together through tight fit, and the other part presses the part of the reinforcing layer between the inner wall of the locking sleeve and the outer wall of the joint body against the outer wall of the joint body. The joint for non-metal oil pipe, the oil pipe and the method for installing the joint can overcome the shortcomings that the connecting bearing capacity between the joint and the pipe body of the existing non-metal oil pipe is low and the heat resistance is poor.

Description

Technical Field

[0001] This invention relates to the field of oil and gas transportation, and more particularly to a joint for non-metallic oil pipes, an oil pipe and a method for installing the joint. Background Technology

[0002] In existing technologies, seamless steel pipes are widely used in oil and gas extraction. Commonly used tubing consists of a pipe body and fittings, with the pipe bodies connected and sealed by tapered threads at both ends of the fittings. Multiple sections of tubing are connected together and extended downhole. The complex downhole conditions and the reciprocating motion of the sucker rod easily cause tubing wear, corrosion, scaling on the pipe walls, and damage to the tapered threads. Damage to metal tubing inevitably leads to frequent well workovers, reducing oil and gas production efficiency and increasing extraction costs.

[0003] Oil pipes are prone to wear, corrosion, and scaling. Currently, the common approach is to coat the inner wall of the pipe. However, it is difficult to completely remove rust from the inner wall, resulting in poor adhesion of the coating. Especially during use, the poorly adhered coating will gradually peel off, and the detached paint impurities can even cause pump jamming. Therefore, the application of inner coating technology for oil pipes is limited. Currently, a more advanced technology to solve various oil pipe problems is to install a polyethylene liner on the inner wall of the pipe, which can solve problems such as wear, corrosion, and scaling to some extent. However, due to the liner material and installation process, the liner does not fit well with the pipe body, causing peeling, loosening, and unstable service life. Furthermore, the liner has poor heat resistance; at high temperatures of the transported medium, the connection between the liner and the joint is also prone to loosening. On the other hand, installing a liner requires a high level of thorough cleaning of the inner surface of the pipe, and the installation process involves cumbersome steps such as diameter reduction, pipe insertion, heating, and flanging, resulting in high manufacturing costs and hindering widespread application. Summary of the Invention

[0004] This invention provides a connector for non-metallic oil pipes, which can overcome the shortcomings of existing non-metallic oil pipe connectors and pipe bodies, such as low load-bearing capacity and poor heat resistance.

[0005] The present invention relates to a connector for a non-metallic oil pipe, wherein the non-metallic body of the oil pipe includes a tubular reinforcing layer and a tubular inner liner layer located within the reinforcing layer, the inner liner layer being tightly bonded to the reinforcing layer, and the connector comprising:

[0006] The connector body is tubular, and one end of the connector body is provided with a connecting thread;

[0007] A locking sleeve, which is tubular, is fitted over the connector body and coaxial with it. When the connector body and the non-metallic oil pipe are installed, a portion of the inner wall of the locking sleeve is opposite to the outer wall of the connector body and fixed together by a tight fit. Another portion presses the reinforcing layer located between the inner wall of the locking sleeve and the outer wall of the connector body against the outer wall of the connector body, so that the inner wall of the reinforcing layer is directly and tightly fitted to the outer wall of the connector body and fixed together.

[0008] Preferably, the outer wall of the connector body has annular first steps, second steps, and third steps arranged sequentially from one end to the other, with the diameters of the first step, second step, and third step decreasing sequentially. When the connector body and the non-metallic oil pipe are installed, a portion of the inner wall of the locking sleeve is opposite to the outer wall of the second step and forms a tight fit to fix it together, and another portion is opposite to the outer wall of the third step and forms a tight fit to fix it together. The connecting thread is provided at the end of the connector body with the first step.

[0009] Preferably, the inner wall of the end of the connector body away from the connecting thread is provided with a fourth step, and the outer wall of the end of the inner liner forms an inner liner step that matches the fourth step. When the connector body and the non-metallic oil pipe are installed, the outer wall of the first step and the inner wall of the inner liner step are tightly fitted together and fixed together.

[0010] Preferably, the outer walls of both the second and third steps are provided with multiple annular first protrusions, and the inner wall of the locking sleeve is provided with multiple annular second protrusions. When the connector body and the non-metallic oil pipe are fully installed, the second protrusions are offset from the first protrusions. The length of the third step is greater than the length of the second step. The outer wall of the end of the connector body with the third step forms a conical surface that allows the reinforcing layer to smoothly transition at the end of the third step.

[0011] Preferably, the outer wall of the locking sleeve is provided with knurling or an annular groove circumferentially surrounding the locking sleeve. The end of the locking sleeve used to press against the second step has an axial groove parallel to the axial direction of the locking sleeve, the axial groove penetrating both the outer and inner walls of the locking sleeve.

[0012] Preferably, the connector further includes a cylindrical protective layer covering the outside of the locking sleeve and the portion of the locking sleeve that connects to the reinforcing layer at the end away from the connecting thread, while the locking sleeve is pressing against the outer wall of the second step and the reinforcing layer. The protective layer is formed by injection molding, and the portion of the inner wall of the protective layer opposite to the axial groove protrudes inward and passes through the axial groove to tightly bond with the outer wall of the second step. The thickness of the portion of the reinforcing layer pressed by the locking sleeve is greater than the thickness of the other portions of the reinforcing layer.

[0013] Preferably, when the connecting thread is formed on the outer wall of the first step, the connector constitutes a male connector, and when the connecting thread is formed on the inner wall of the first step, the connector constitutes a female connector.

[0014] The present invention also provides an oil pipe comprising a non-metallic pipe body, wherein at least one end of the pipe body is connected to the connector described in any one of the preceding inventions.

[0015] The present invention also provides another type of oil pipe, comprising a non-metallic pipe body, one end of which is connected to a male connector as described above, and the other end of which is connected to a female connector as described above.

[0016] The present invention also provides a method for installing a connector, for connecting the connector to the non-metallic body of an oil pipe, comprising the following steps:

[0017] (1) Remove the inner lining layer at the end of the pipe body, and perform circumferential peeling on the outer wall of the end formed after the inner lining layer is removed to form an inner lining layer step.

[0018] (2) Place the tubular locking sleeve over the outside of the tube body, and make the end of the tube body protrude outside the locking sleeve;

[0019] (3) The end of the reinforcing layer is sleeved on the outside of the tubular connector body so that the inner wall of the reinforcing layer is opposite to and in direct contact with the outer wall of the connector body. One end of the connector body is provided with a connecting thread, and at the same time, the inner wall of the inner lining layer step is opposite to and in direct contact with the outer wall of the fourth step provided on the outer wall of the connector body at the end away from the connecting thread.

[0020] (4) Move the locking sleeve to the end of the tube body, so that part of the locking sleeve is fitted on the outer wall of the connector body and this part of the locking sleeve is in contact with the outer wall of the connector body, and part of the locking sleeve is fitted on the outside of the part of the reinforcing layer fitted on the outside of the connector body. Apply radial inward pressure to the locking sleeve around the outer wall of the locking sleeve. The locking sleeve shrinks and deforms under the pressure, and its inner wall presses against the outer wall of the connector body and the outer wall of the reinforcing layer.

[0021] Preferably, the outer wall of the connector body has annular first steps, second steps and third steps arranged sequentially from one end to the other, the diameters of the first step, second step and third step decreasing sequentially, the connecting thread is provided at the end of the connector body with the first step, in step (1), the length of the inner liner peeled off is the same as the length of the third step, in step (4), a part of the inner wall of the locking sleeve is opposite to the outer wall of the second step, and another part is opposite to the outer wall of the third step, after the locking sleeve is deformed by radially inward external pressure, part of its inner wall can be pressed against the outer wall of the second step of the connector body, and another part can press the part of the reinforcing layer located between the inner wall of the locking sleeve and the outer wall of the third step against the outer wall of the third step.

[0022] Preferably, the method further includes step (5), covering the outside of the locking sleeve and the end of the locking sleeve away from the connecting thread where it meets the reinforcing layer with a cylindrical protective layer.

[0023] Preferably, the protective layer is formed by injection molding. During injection molding, the injection material enters the axial groove of the locking sleeve, so that the inner wall of the protective layer formed by the injection material passes through the axial groove and forms a tight bond with the outer wall of the second step; and / or the injection material enters the knurling of the outer wall of the locking sleeve or the annular groove surrounding the outer wall of the locking sleeve.

[0024] The connector for non-metallic oil pipes of the present invention has the following advantages compared with the prior art:

[0025] 1. The connector for non-metallic oil pipes of the present invention uses a locking sleeve to press the reinforcing layer of the pipe body against the outer wall of the connector body, so that the inner wall of the reinforcing layer is directly and tightly fitted to the outer wall of the connector body. The axial force between the connector and the pipe body is borne by the reinforcing layer, which has a greater strength than the inner lining layer and can withstand a greater axial force. Therefore, a more stable connection can be obtained than with traditional connectors. At the same time, the heat resistance of the reinforcing layer is better than that of the inner lining layer, thereby improving the temperature resistance of the connection between the connector and the non-metallic oil pipe.

[0026] 2. The tubing body of the present invention further includes a cylindrical protective layer covering the outside of the locking sleeve and the area where the locking sleeve, away from the connecting thread, contacts the reinforcing layer, while the locking sleeve is pressing against the outer wall of the second step and the reinforcing layer. The protective layer not only protects the locking sleeve and the reinforcing layer, but also prevents external impurities from entering between the locking sleeve and the second step and between the locking sleeve and the reinforcing layer. Attached Figure Description

[0027] Figure 1This is a schematic diagram of the structure of a connector body for a non-metallic oil pipe according to an embodiment of the present invention. The connector body in the figure constitutes the connector body of a male connector, and the connector body in the right figure constitutes the connector body of a female connector.

[0028] Figure 2 This is a schematic diagram of the locking sleeve for a non-metallic oil pipe connector according to an embodiment of the present invention.

[0029] Figure 3 This is a schematic diagram of the structure of a connector for a non-metallic oil pipe after installation with the pipe body, according to an embodiment of the present invention.

[0030] Figure 4 This is a schematic diagram of the structure of a connector for a non-metallic oil pipe after installation with the pipe body, according to another embodiment of the present invention.

[0031] Figure Labels

[0032] 1. Connector body; 11. First step; 12. Connecting thread; 13. Second step; 14. First protrusion; 15. Third step; 16. Fourth step; 17. Conical surface;

[0033] 2. Locking sleeve; 21. Annular groove; 22. Second protrusion; 23. Axial groove;

[0034] 3 protective layers;

[0035] 4. Pipe body, 41. Reinforcing layer, 42. Inner lining layer, 43. Inner lining layer step. Detailed Implementation

[0036] This invention provides a connector for non-metallic oil pipes, used to connect with the non-metallic body 4 of the oil pipe, such as... Figure 3 and Figure 4 As shown, the non-metallic pipe body 4 of the oil pipe includes a tubular reinforcing layer 41 and a tubular inner liner 42 located within the reinforcing layer 41. The inner liner 42 is tightly bonded to the reinforcing layer 41. The joint includes a joint body 1 and a locking sleeve 2. Figure 1 As shown, the connector body 1 is tubular, and in this embodiment, it is an integral circular tube. The outer diameter of the connector is slightly larger than the inner diameter of the non-metallic tube 4, ensuring the passage of certain tools at the connection point between the connector body 1 and the tube 4 while forming an interference fit. One end of the connector body 1 is provided with a connecting thread 12. Figure 2As shown, the locking sleeve 2 is tubular. The locking sleeve 2 is fitted outside the connector body 1 and is coaxial with the connector body 1. When the connector body 1 and the pipe body 4 of the non-metallic oil pipe are installed, the locking sleeve 2 is deformed by radially inward external pressure. A part of its inner wall can be pressed against the outer wall of the connector body 1 to form a tight fit and fix them together. The other part can press the part of the reinforcing layer 41 located between the inner wall of the locking sleeve 2 and the outer wall of the connector body 1 against the outer wall of the connector body 1 so that the inner wall of the reinforcing layer 41 and the outer wall of the connector body 1 are directly and tightly fitted together.

[0037] With the connector for non-metallic oil pipes of the present invention, the locking sleeve 2 can press the reinforcing layer 41 of the pipe body 4 against the outer wall of the connector body 1, so that the inner wall of the reinforcing layer 41 and the outer wall of the connector body 1 are directly and tightly fitted together. The axial force between the connector and the pipe body 4 is borne by the reinforcing layer 41. The strength of the reinforcing layer 41 is greater than that of the inner lining layer 42, and the axial force it can withstand is also greater than that of the inner lining layer 42. Therefore, a more stable connection relationship can be obtained than that of traditional connectors. At the same time, the heat resistance of the reinforcing layer 41 is also better than that of the inner lining layer, thereby improving the temperature resistance at the connection between the connector body 1 and the pipe body 4 of the non-metallic oil pipe.

[0038] In this invention, the axial direction refers to the axial direction of the cylindrical connector body 1 or the locking sleeve 2, and the radial direction refers to the radial direction of the cylindrical connector body 1 or the locking sleeve 2. The radial external pressure experienced by the locking sleeve 2 can be provided by an existing hydraulic cylinder-driven multi-jaw radial extrusion device, through which the radially arranged extrusion heads synchronously extrude radially, tightening and deforming the locking sleeve 2.

[0039] like Figure 1 As shown, the outer wall of the connector body 1 has annular first steps 11, second steps 13, and third steps 15 arranged sequentially from one end to the other. Adjacent steps are connected together. The diameters of the first steps 11, second steps 13, and third steps 15 decrease sequentially. The connecting thread 12 is provided at the end of the connector body 1 with the first step 11. When the connector body 1 and the pipe body 4 of the non-metallic oil pipe are installed, a portion of the inner wall of the locking sleeve 2 is aligned with the outer wall of the second step 13 and forms a tight fit to fix it together, and another portion is aligned with the outer wall of the third step 15 and forms a tight fit to fix it together. The arrangement of the second steps 13 and the third steps 15 allows the inner wall of the locking sleeve 2 to simultaneously press against the outer wall of the connector body 1 and the outer wall of the reinforcing layer 41 to achieve a fixed connection between the locking sleeve 2, the connector body 1, and the reinforcing layer 41. At the same time, the inner wall of the locking sleeve does not need to be modified in a complex way.

[0040] The inner wall of the connector body 1 at the end away from the connecting thread 12 is provided with a fourth step 16. The outer wall of the end of the inner liner 42 forms an inner liner step 43 that mates with the fourth step 16. When the connector body 1 and the pipe body 4 of the non-metallic oil pipe are installed, the outer wall of the first step 11 and the inner wall of the inner liner step 43 form a tight fit and are fixed together. This structure allows the inner liner 42 and the connector body 1 to also form a tight fit, making the connection between the connector body 1 and the pipe body 4 more secure. Furthermore, the radial expansion of the inner liner 42 of the pipe body 4 when the pressure of the medium inside the pipe body 4 reaches 5MPa or above strengthens the tight fit between the outer wall of the inner liner step 43 and the inner wall of the fourth step 16 of the connector body, enabling the inner liner 42 and the connector body 1 to achieve self-sealing. The higher the medium pressure, the more reliable the seal.

[0041] Designed according to API tubing specifications, taking a 4-inch tubing as an example, based on the structural design requirements of this invention, the outer diameter of the first step 11 of the connector is 127mm, the outer diameter of the second step 13 is 108.6mm, and the outer diameter of the third step 15 is 98.6mm. The length of the second step 13 is 86mm, and the length of the third step 15 is 102mm. The inner diameter of the locking sleeve 22 is 109.5mm, and the outer diameter is 120.2mm. The inner diameter of the inner lining layer 42 of the tubing body 4 is 88.6mm, and the outer diameter is 98.6mm. The reinforcing layer 41 is made of nylon fiber with a thickness of 8mm. The inner lining layer 42 is made of heat-resistant polyethylene (PE-RT), with a continuous working temperature of up to 90 degrees Celsius, which can meet the needs of most downhole oil production operations. Through testing and analysis, the connection between the connector body 1 and the tubing body 4 can withstand an internal pressure of up to 55MPa, meeting the needs of conventional downhole oil production.

[0042] In this embodiment, the connector body 1 is made of a corrosion-resistant alloy material, and the locking sleeve 2 is made of a highly ductile metal material. Figure 1 As shown, the outer walls of the second step 13 and the third step 15 are both provided with multiple annular first protrusions 14. The first protrusions 14 can be boss-shaped or tooth-shaped with pointed tips. Figure 2 As shown, the inner wall of the locking sleeve 2 is provided with multiple annular second protrusions 22, such as... Figure 3 and Figure 4As shown, in the assembled state of the locking sleeve 2, the second protrusion 22 is offset from the first protrusion 14. With the locking sleeve 2 pressing against the reinforcing layer 41, the first protrusion 14 on the outer wall of the third step 15 can apply a radially outward force to the reinforcing layer 41, and the second protrusion 22 on the inner wall of the locking sleeve 2 can apply a radially inward force to the reinforcing layer 41, causing deformation of the reinforcing layer 41. This results in a tighter bond between the reinforcing layer 41 and the inner wall of the locking sleeve 2 and the outer wall of the third step 15. The offset of the first protrusion 14 of the third step 15 from the second protrusion 22 of the locking sleeve 2 causes the reinforcing layer 41 to deform in different directions at different axial positions, thus gripping the reinforcing layer 41 between the first protrusion 14 and the second protrusion 22, further improving the bonding force between the reinforcing layer 41 and the inner wall of the locking sleeve 2 and the outer wall of the third step 15. The first protrusion 14 on the outer wall of the second step 13 intersects with the second protrusion 22 of the locking sleeve 2, which can form an engagement, thereby improving the axial bonding force between the locking sleeve 2 and the connector body 1.

[0043] In this embodiment, the length of the third step 15 is greater than the length of the second step 13, which increases the length of the connection between the reinforcing layer 41 and the connector, thereby increasing the bonding area between the reinforcing layer 41 and the connector and achieving greater bonding force.

[0044] The outer wall of one end of the connector body 1 with the third step 13 forms a conical surface 17 that allows the reinforcing layer 41 to smoothly transition at the end of the third step 15. The smooth transition ensures that the end of the reinforcing layer 41 is in close contact with the third step 15, while preventing large deformation of the reinforcing layer 41 at this point and stress concentration, thereby increasing the resistance of the reinforcing layer 41.

[0045] The outer wall of the locking sleeve 2 is provided with knurling or an annular groove 21 circumferentially surrounding the locking sleeve 2. For example... Figure 2 As shown, the outer wall of the locking sleeve 2 is provided with an annular groove 21. One end of the locking sleeve 2 used to press against the second step 13 is provided with an axial groove 23 parallel to the axial direction of the locking sleeve 2. The axial groove 23 penetrates the outer wall and inner wall of the locking sleeve 2. In this embodiment, the locking sleeve 2 has multiple axial grooves 23, and these multiple axial grooves 23 are evenly arranged along the circumference of the locking sleeve 2. In this embodiment, the axial grooves 23 penetrate the outer wall and inner wall of the locking sleeve 2.

[0046] The connector also includes a cylindrical protective layer 3 covering the outside of the locking sleeve 2 and the area where the end of the locking sleeve 2 away from the connecting thread 12 meets the reinforcing layer 41, while the locking sleeve 2 is pressed against the outer wall of the second step 13 and the reinforcing layer 41. The protective layer 3 not only protects the locking sleeve 2 and the reinforcing layer 41, but also prevents external impurities from entering between the locking sleeve 2 and the second step 13, and between the locking sleeve 2 and the reinforcing layer 41. In this embodiment, the protective layer 3 is injection molded. During injection molding, the injection material enters the axial groove 23, causing the portion of the inner wall of the formed protective layer 3 opposite to the axial groove 23 to bulge inward and pass through the axial groove 23, tightly bonding with the outer wall of the second step 13. This arrangement increases the thickness of the protective layer 3 at the axial groove 23, thus increasing its strength, and also improves the bonding force between the protective layer 3, the locking sleeve 2, and the connector body 1, while simultaneously forming a seal.

[0047] Simultaneously, the injection molding material also enters the annular groove 21 or knurling on the outer wall of the locking sleeve 2, which can improve the bonding strength between the protective layer 3 formed by the injection molding material and the locking sleeve 2. Even if it is torn forcefully, the protective layer 3 is not easy to detach from the locking sleeve 2.

[0048] In this embodiment, the thickness of the portion of the reinforcing layer 41 that is pressed by the locking sleeve 2 is greater than the thickness of the other portions of the reinforcing layer 41, which can increase the axial force that the reinforcing layer 41 can withstand, making the connection between the tube body 4 and the connector more secure.

[0049] The inner layer of the reinforcing layer 41 at the joint is processed by wet winding. Through wet winding, the reinforcing layer 41 at the end of the pipe body 4 is wound layer by layer and bonded to the joint body 1, and then the locking sleeve 2 is fitted.

[0050] like Figure 4 As shown in the left figure, when the connecting thread 12 is formed on the outer wall of the first step 11, the connector constitutes a male connector. In this embodiment, the outer wall of the connector body 1 at one end with the first step 11 gradually increases in the axial direction starting from the end of the connector body 1, and the outer wall of this end is provided with an external thread. Figure 4 As shown in the right figure, the connecting thread 12 is formed on the inner wall of the first step 11, and the connector constitutes a female connector. In this embodiment, the inner wall of the connector body 1 at one end with the first step 11 gradually tapers in the axial direction starting from the end of the connector body 1, and the inner wall of this end is provided with an internal thread.

[0051] The present invention provides an oil pipe, comprising a non-metallic pipe body 4, one end of which is connected to a connector as described above, and the other end of which can be connected to other equipment or other connectors.

[0052] The present invention also provides another type of oil pipe, comprising a non-metallic pipe body 4, one end of which is connected to a male connector and the other end of which is connected to a female connector. When it is necessary to connect two sections of pipe body 4 together, the male connector of one pipe body 4 can be connected to the female connector of the other pipe body 4 by means of threads.

[0053] This invention provides a method for installing a connector, used to connect the connector as described above to the non-metallic pipe body 4 of an oil pipe, comprising the following steps:

[0054] (1) Remove the inner lining layer 42 at the end of the pipe body, and perform circumferential peeling on the outer wall of the end formed after the inner lining layer 42 is removed to form an inner lining layer step 43.

[0055] (2) Put the tubular locking sleeve 2 on the outside of the tube body and make the end of the tube body protrude outside the locking sleeve 2.

[0056] (3) The end of the reinforcing layer 41 is sleeved on the outside of the tubular connector body 1 so that the inner wall of the reinforcing layer 41 is opposite to and in direct contact with the outer wall of the connector body 1. One end of the connector body 1 is provided with a connecting thread 12. At the same time, the inner wall of the inner lining step 43 of the inner lining layer 42 is opposite to and in direct contact with the outer wall of the fourth step 16 provided on the outer wall of the connector body 1 at the end away from the connecting thread 12.

[0057] (4) Move the locking sleeve 2 to the end of the tube body, so that part of the locking sleeve 2 is fitted on the outer wall of the connector body 1 and this part of the locking sleeve 2 is in contact with the outer wall of the connector body 1, and part of the locking sleeve 2 is fitted on the outside of the part of the reinforcing layer 41 that is fitted on the outside of the connector body 1. Apply radial inward pressure to the locking sleeve 2 around the outer wall of the locking sleeve 2. The locking sleeve 2 shrinks and deforms under the pressure, and its inner wall presses against the outer wall of the connector body and the outer wall of the reinforcing layer.

[0058] Using the installation method of this invention, the locking sleeve 2 can press the reinforcing layer 41 of the pipe body 4 tightly against the outer wall of the joint body 1. The axial force between the joint and the pipe body 4 is borne by the reinforcing layer 41. The strength of the reinforcing layer 41 is greater than that of the inner lining layer 42, and the axial force it can withstand is also greater than that of the inner lining layer 42. Therefore, a more stable connection relationship can be obtained than with traditional joints. Through testing and analysis, the joint and pipe body 4 can withstand an internal pressure of up to 55 MPa, meeting the requirements of conventional downhole oil production.

[0059] like Figure 1As shown, the outer wall of the connector body has annular first step 11, second step 13 and third step 15 arranged sequentially from one end to the other. The diameters of the first step 11, second step 13 and third step 15 decrease sequentially. The connecting thread 12 is provided at the end of the connector body 1 with the first step 11. In step (1), the length of the inner liner 42 that is peeled off is the same as the length of the third step 15. In step (4), a part of the inner wall of the locking sleeve 2 is opposite to the outer wall of the second step 13, and another part is opposite to the outer wall of the third step 15. After the locking sleeve 2 is deformed by radially inward external pressure, part of its inner wall can be pressed against the outer wall of the second step 13 of the connector body 1, and another part can press the part of the reinforcing layer 41 located between the inner wall of the locking sleeve 51 and the outer wall of the third step 15 against the outer wall of the third step 15.

[0060] When the pressure of the medium inside the pipe body 4 reaches 25MPa or above, the axial expansion of the inner lining 42 causes its end to form a sealing fit with the end wall of the joint body 1 at the end where the third step 15 is provided. Therefore, the inner lining 42 and the joint body 1 can achieve self-sealing, and the greater the medium pressure, the more reliable the seal.

[0061] In another embodiment, the installation method of the connector of the present invention further includes step (5), which involves covering the outside of the locking sleeve 2 and the outer portion of the locking sleeve 2 away from the connecting thread 12 where it connects with the reinforcing layer 41 with a cylindrical protective layer 3. This not only protects the locking sleeve 2 and the reinforcing layer 41, but also forms a seal at the connection between the locking sleeve 2 and the reinforcing layer 41, preventing external impurities from entering between the locking sleeve 2 and the second step 11, and between the inner wall of the locking sleeve 2 and the outer wall of the reinforcing layer 41.

[0062] In step (5), the protective layer 3 is formed by injection molding the outer wall of the locking sleeve 2 and the outer wall of the reinforcing layer 41 near the joint. Injection molding can be performed using a conventional injection molding machine. When the end of the tube 4 passes through the joint in the injection molding machine, the machine coats the locking sleeve 2 with heated injection material. After cooling, the injection material forms the protective layer 3. The injection material is polyethylene. During injection molding, the injection material enters the axial groove 23 located at the end of the locking sleeve 2 near the first step 11, and after passing through the axial groove 23, forms a tight bond with the outer wall of the second step 13. This arrangement improves the bonding strength between the protective layer 3, the locking sleeve 2, and the outer wall of the joint body 1. Furthermore, the thickness of the portion of the protective layer 3 opposite the axial groove 23 is greater than other portions, which also improves the strength of this portion.

[0063] In this embodiment, a male connector is installed at one end of the pipe body 4, and a female connector is installed at the other end of the pipe body 4. The installation methods for the male and female connectors are the same.

[0064] 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. Various modifications or equivalent substitutions made by those skilled in the art to the present invention within its spirit and scope of protection also fall within the scope of protection of the present invention.

Claims

1. A joint for a non-metallic oil pipe, the non-metallic pipe body of the oil pipe comprising a tubular reinforcing layer and a tubular inner liner located within the reinforcing layer, the inner liner and the reinforcing layer being tightly bonded together, characterised in that, The joint comprises: a joint body which is tubular, one end of the joint body being provided with a connecting thread; a locking sleeve which is tubular, the locking sleeve being sleeved on the joint body coaxially, in a state where the joint body and the pipe body of the non-metal oil pipe are installed, a part of the inner wall of the locking sleeve is opposite to the outer wall of the joint body and is fixed together by tight fit, another part compresses the part of the reinforcing layer between the inner wall of the locking sleeve and the outer wall of the joint body to the outer wall of the joint body so that the inner wall of the reinforcing layer and the outer wall of the joint body are directly fixed together by tight fit; the outer wall of the joint body has annular first, second and third steps arranged in sequence from one end to the other end, the diameters of the first, second and third steps decrease in sequence, in a state where the joint body and the pipe body of the non-metal oil pipe are installed, a part of the inner wall of the locking sleeve is opposite to the outer wall of the second step and is fixed together by tight fit, another part is opposite to the outer wall of the third step and is fixed together by tight fit, the connecting thread is arranged at the end of the joint body with the first step; the inner wall of the end of the joint body away from the connecting thread is provided with a fourth step, the outer wall of the end of the inner lining layer forms an inner lining step matched with the fourth step, and in a state where the joint body and the pipe body of the non-metal oil pipe are installed, the outer wall of the first step and the inner wall of the inner lining step are fixed together by tight fit; the outer wall of the second step and the outer wall of the third step are each provided with a plurality of annular first protrusions, the inner wall of the locking sleeve is provided with a plurality of annular second protrusions, in a state where the joint body and the pipe body of the non-metal oil pipe are installed, the second protrusions and the first protrusions are staggered; the locking sleeve for compressing one end of the second step is provided with an axial groove parallel to the axial direction of the locking sleeve, the axial groove penetrates the outer wall and the inner wall of the locking sleeve; the joint further comprises a cylindrical protective layer covering the outside of the locking sleeve and the joint between the end of the locking sleeve away from the connecting thread and the reinforcing layer in a state where the locking sleeve compresses the outer wall of the second step and the reinforcing layer.

2. The joint of claim 1, wherein The length of the third step is greater than the length of the second step.

3. The fitting of claim 1, wherein The outer wall of the end of the joint body provided with the third step forms a conical surface for smooth transition of the reinforcing layer at the end of the third step.

4. The fitting of claim 1, wherein The outer wall of the locking sleeve is provided with knurling or an annular groove surrounding the locking sleeve circumferentially.

5. The fitting of claim 1, wherein The protective layer is formed by injection molding, the part of the inner wall of the protective layer opposite to the axial groove is inwardly convex and tightly combined with the outer wall of the second step after penetrating the axial groove.

6. The fitting of claim 1, wherein The thickness of the part of the reinforcing layer compressed by the locking sleeve is greater than the thickness of other parts of the reinforcing layer.

7. The joint of any of claims 1-6, wherein, When the connecting thread is formed on the outer wall of the first step, the joint constitutes a male joint, and when the connecting thread is formed on the inner wall of the first step, the joint constitutes a female joint.

8. A tubing comprising a non-metallic tubing body, characterized in that, At least one end of the pipe body is connected with the joint as claimed in any one of claims 1-7.

9. A tubing comprising a non-metallic tubing body, characterized in that, One end of the pipe body is connected with the male joint as claimed in claim 7, and the other end of the pipe body is connected with the female joint as claimed in claim 7.

10. A method of installing a fitting for use in conjunction with a non-metallic oil pipe with a fitting according to any one of claims 1 to 7, characterised in that, The method comprises the following steps: (1) peeling off the inner liner layer of the end of the pipe body, and ring-peeling the outer wall of the end formed after the inner liner layer is peeled off to form an inner liner layer step; (2) sleeving the tubular locking sleeve outside the pipe body, and exposing the end of the pipe body outside the locking sleeve; (3) sleeving the end of the reinforcing layer outside the tubular joint body so that the inner wall of the reinforcing layer is opposite to and directly contacts with the outer wall of the joint body, one end of the joint body is provided with a connecting thread, and the inner wall of the inner liner layer step of the inner liner layer is opposite to and directly contacts with the outer wall of a fourth step provided at the end of the joint body away from the connecting thread; (4) moving the locking sleeve to the end of the pipe body, so that a part of the locking sleeve is sleeved outside the outer wall of the joint body and contacts with the outer wall of the joint body, and another part of the locking sleeve is sleeved outside the part of the reinforcing layer sleeved outside the joint body, a radial inward pressure is applied to the locking sleeve around the outer wall of the locking sleeve, the locking sleeve is deformed under the pressure, and the inner wall of the locking sleeve is pressed against the outer wall of the joint body and the outer wall of the reinforcing layer.

11. The method of installing a joint according to claim 10, wherein, The outer wall of the joint body has an annular first step, a second step and a third step arranged in sequence from one end to the other end, the diameters of the first step, the second step and the third step are sequentially reduced, the connecting thread is arranged at the end of the joint body having the first step, in step (1), the length of the inner liner layer peeled off is the same as the length of the third step, in step (4), a part of the inner wall of the locking sleeve is opposite to the outer wall of the second step, and another part of the inner wall of the locking sleeve is opposite to the outer wall of the third step, after the locking sleeve is deformed under the radial inward pressure, the part of the inner wall of the locking sleeve can be pressed against the outer wall of the second step of the joint body, and the other part can press the part of the reinforcing layer between the inner wall of the locking sleeve and the outer wall of the third step against the outer wall of the third step.

12. The method of installing a joint according to claim 11, wherein, The method further comprises step (5) of wrapping a tubular protective layer at the joint between the locking sleeve and the reinforcing layer away from the connecting thread.

13. The method of installing a joint according to claim 12, wherein, The protective layer is formed by injection molding, when the injection molding is performed, the injection molding material enters the axial groove of the locking sleeve, so that the part of the inner wall of the protective layer formed by the injection molding material opposite to the axial groove passes through the axial groove and is tightly combined with the outer wall of the second step; and / or the injection molding material enters the knurl of the outer wall of the locking sleeve or the annular groove around the outer wall of the locking sleeve.

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