An end-to-end connection method for pipelines with an internal corrosion-resistant layer

Abstract

The present invention provides an end-to-end connection method for a pipeline with an inner corrosion-resistant layer, which relates to the technical field of oil casing pipes and can overcome the problems of reverse torque loosening, misalignment of shoulder faces or insufficient make-up torque at the field end during the end-to-end threaded connection of pipelines with corrosion-resistant layers, and realizes the precise and effective connection of the pipe string and the integrity of corrosion prevention; for a bimetallic pipe body with a corrosion-resistant alloy as the inner layer, a corrosion-resistant alloy layer is provided on the pipe body end face; external threads are machined on the ends of the pipeline with an inner corrosion-resistant layer and the fitting nipple, and internal threads are symmetrically machined at both ends of the coupling; the first end of the coupling is connected to the fitting nipple and screwed in until it reaches the positioning position of the fitting nipple; anti-loosening fastening and anti-galling oil casing pipe thread grease is applied to the external threads of the first section of the pipeline and it is connected to the second end of the coupling and screwed in until it contacts the fitting nipple; the fitting nipple is removed; anti-galling oil casing pipe thread grease is applied to the external threads of the second section of the pipeline and it is connected to the first end of the coupling and screwed in until it contacts the end of the first section of the pipeline with an inner corrosion-resistant layer.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and casing pipes, and in particular to an end-to-end connection method for oil and casing pipes with an inner corrosion-resistant layer. Background Art

[0002] Due to the harsh corrosion service environment of oil and gas fields, uniform corrosion and pitting perforation failures frequently occur on the inner wall of tubing. Some tubing even corrodes and perforates within a few months. According to the H2S partial pressure, CO2 partial pressure, Cl- mass concentration, temperature, pressure, and liquid flow conditions in the environment, in the order of increasing corrosion resistance, the corrosion-resistant alloy materials that can be selected are low-carbon alloy steel, martensitic stainless steel, duplex stainless steel, iron-nickel corrosion-resistant alloy, and nickel-based corrosion-resistant alloy. For high-temperature and high-pressure natural gas fields containing H2S, CO2, and Cl- simultaneously in northeastern Sichuan, Tarim, etc. in Sichuan, martensitic stainless steel pipes (super 13Cr) and nickel-based corrosion-resistant alloy pipes (825, G3) are currently mostly selected. However, stress corrosion cracking failures of super 13Cr tubing also occur frequently; while pure nickel-based corrosion-resistant alloy tubing is very expensive and the cost is too high, making it difficult to promote and use. Bimetallic composite tubing can greatly reduce the cost of corrosion-resistant tubing, organically combining the high strength of the outer carbon steel and the anti-corrosion performance of the inner corrosion-resistant alloy, improving performance and reducing costs, and has been widely used.

[0003] Although the pipeline with an inner corrosion-resistant layer effectively solves the corrosion problem, the threaded connection part still has the problem of easy corrosion. How to solve the corrosion problem of the threaded connection part and achieve the anti-corrosion of the entire pipe string is an urgent problem to be solved currently. Using the opposed-thread type, the inner wall anti-corrosion of the pipe string is carried out through the contact between the corrosion-resistant inner layers of the bimetallic pipes, and there are the following problems: one is whether the two connected metal pipes can be effectively contacted; the second is that the frictional force generated on the opposed surface may cause the threaded connection on the other side to become loose; the third is that due to the interference of the external thread at the factory end, the external thread at the field end cannot be screwed in place and the make-up torque is insufficient.

[0004] Therefore, it is necessary to study an end-to-end connection method for oil and casing pipes with an inner corrosion-resistant layer to address the deficiencies of the existing technology and solve or mitigate one or more of the above problems. Summary of the Invention

[0005] In view of this, the present invention provides an end-to-end connection method for oil and casing pipes with an inner corrosion-resistant layer, which can overcome the problems of reverse torque loosening, improper butting of shoulder surfaces, or insufficient make-up torque at the field end that may occur during the threaded connection of the opposed-thread type pipeline with an inner corrosion-resistant layer in the prior art, realize the precise and effective connection of the pipeline string with an inner corrosion-resistant layer, achieve the precision between the pipelines with an inner corrosion-resistant layer, realize the precise and effective connection of the pipeline string with an inner corrosion-resistant layer, and achieve the integrity of the anti-corrosion of the bimetallic pipe string, ensuring the corrosion resistance of the entire pipe string.

[0006] The present invention provides an end-to-end connection method for oil casing pipes with an inner corrosion-resistant layer, which realizes the connection between the pipes to be connected with the inner corrosion-resistant layer in an end-to-end manner. The steps of the assembly method include:

[0007] During factory processing and assembly:

[0008] S1. Process external threads on the ends of the two pipes to be connected and on the assembly short section for positioning, and symmetrically process internal threads on the inner walls of both ends of the connection coupling.

[0009] S2. First, thread-connect the first end of the connection coupling with the assembly short section, and the thread screwing position reaches the positioning position of the assembly short section.

[0010] S3. Apply anti-loosening fastening oil casing thread grease and anti-sticking thread grease for oil casing on the external thread of the first pipe section in segments, and thread-connect it with the second end of the connection coupling, and screw it in until the end face of the coupling contacts the assembly short section.

[0011] During on-site construction and assembly:

[0012] S4. Remove the assembly short section.

[0013] S5. Apply anti-sticking thread grease for oil casing on the external thread of the second pipe section, and thread-connect it with the first end of the connection coupling, and screw it in until it contacts the first pipe section.

[0014] The purpose of applying anti-loosening fastening oil casing thread grease in step S3 is to fix the threaded connection at the factory end and prevent the threaded connection that has been connected at this end from being loosened by the counterclockwise rotation of the threads due to the reaction torque generated by the end face contact when screwing on the site (i.e., screwing on the first end of the connection coupling and the second pipe section).

[0015] In the aspect and any possible implementation manner as described above, a further implementation manner is provided. A positioning shoulder is provided on the outer surface of the assembly short section, and the outer diameter at the positioning shoulder is greater than the outer diameter of the external thread of the assembly short section.

[0016] In step S2, the assembly short section is screwed in until the end face of the first end of the connection coupling contacts the positioning shoulder.

[0017] In the aspect and any possible implementation manner as described above, a further implementation manner is provided. The external threads on the two pipe sections are provided in a frustum shape.

[0018] Correspondingly, the external threads of the assembly short section are the same as the frustum-shaped external threads of the two pipe sections, and both match the internal threads of the connection coupling.

[0019] For the aspects and any possible implementation manners described above, a further implementation manner is provided. The distance between the threaded end face of the fitting nipple and the positioning shoulder is equal to half of the length of the connecting coupling. This length setting is to ensure that the pipe threads at both the first end and the second end are screwed onto half of the coupling, thereby solving the problems of incomplete butting and insufficient make-up torque at the field end.

[0020] For the aspects and any possible implementation manners described above, a further implementation manner is provided. Both of the two pipeline segments to be connected include an outer metal pipe and an inner metal pipe;

[0021] The inner metal pipe at the end to be connected protrudes 3 mm - 6 mm compared with the outer metal pipe, and a corrosion-resistant metal layer is welded to the protruding part of the inner metal pipe;

[0022] The corrosion-resistant metal layer is connected to the ends of both the inner metal pipe and the outer metal pipe at the same time.

[0023] For the aspects and any possible implementation manners described above, a further implementation manner is provided. The material of the corrosion-resistant metal layer is fused with both the outer metal pipe and the inner metal pipe.

[0024] For the aspects and any possible implementation manners described above, a further implementation manner is provided. The pipeline cross-section thickness difference generated by the frustum is ≥2 mm, and the axial length is ≤4 mm.

[0025] For the aspects and any possible implementation manners described above, a further implementation manner is provided. The contact between the first end face of the connecting coupling and the positioning shoulder specifically means that the gap between the first end face of the connecting coupling and the positioning shoulder of the fitting nipple is ≤0.01 mm.

[0026] For the aspects and any possible implementation manners described above, a further implementation manner is provided. The qualified criterion for the external threads of the first pipeline segment and the second pipeline segment when screwing into the connecting coupling is that the make-up torque value reaches the preset value and the torque curve shows a nose-shoulder touch signal. A nose end is machined on the end faces of the external threads of the two pipes respectively. When the end faces of the external threads of the two pipes contact, that is, when the nose ends touch, the make-up torque curve will have a rapid vertical increase, which is used as the nose-shoulder touch signal.

[0027] For the aspects and any possible implementation manners described above, a further implementation manner is provided. After assembly, the outer surface of the corrosion-resistant metal layer does not contact the inner surface of the connecting coupling, forming a hollow cylindrical section inside the coupling. The outer metal pipe of the pipeline with an inner corrosion-resistant layer is not exposed inside this hollow cylindrical section inside the coupling, and only the corrosion-resistant metal layer is exposed to ensure that the non-corrosion-resistant outer metal pipe does not contact the substances such as oil and gas transported inside the pipe.

[0028] Compared with the prior art, one of the above technical solutions has the following advantages or beneficial effects: By precisely controlling the make-up position of the threaded connection at the factory end, the problems of reverse torque loosening and misalignment of shoulder faces that may occur during the on-site pipe string threaded connection assembly are solved;

[0029] Another of the above technical solutions has the following advantages or beneficial effects: Adopting a frustum-shaped structure to form a stable contact pressure on the contact surface of the threaded connection nose end, thereby achieving effective connection and solving the anti-corrosion problem of the threaded connection part;

[0030] Another of the above technical solutions has the following advantages or beneficial effects: By removing part of the outer pipe of the pipeline with an inner corrosion-resistant layer and welding a corrosion-resistant metal layer, the contact surfaces in butt joint are all corrosion-resistant alloys, thereby ensuring the corrosion resistance of the entire pipe string. Here, the contact surfaces in butt joint refer to the contact surfaces between the end faces of two external threaded joints. Because the inner corrosion-resistant alloy layer is relatively thin and chamfers need to be machined, if the end face corrosion-resistant metal surfacing treatment is not carried out, the outer non-corrosion-resistant pipe body may come into contact with the medium transported in the pipe, thus causing corrosion. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0032] Figure 1 It is a schematic diagram of a bimetallic composite oil casing threaded connection structure provided by an embodiment of the present invention.

[0033] Among them, in the figure:

[0034] 1. Pipeline with inner corrosion-resistant layer; 2. Assembly nipple; 3. Coupling; 4. Corrosion-resistant alloy layer; 5. Anti-loosening fastening oil casing thread compound; 6. Anti-galling oil casing thread compound;

[0035] 1-1. Outer matrix of the pipe body; 1-2. Inner matrix of the pipe body; 1-3. External thread of the pipe body; 1-4. Nose shoulder of the external thread of the pipe body;

[0036] 2-1. External thread of the assembly nipple; 2-2. Positioning shoulder of the assembly nipple;

[0037] 3-1. Internal thread of the coupling; 3-2. Inner hollow cylindrical section of the coupling. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0038] In order to better understand the technical solutions of the present invention, the embodiments of the present invention will be described in detail below in conjunction with the drawings.

[0039] It should be clear that the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0040] Aiming at the problem that the threaded connection part of the in-band corrosion-resistant layer pipeline in the prior art is prone to corrosion, the present invention provides an efficient and simple threaded connection structure. By precisely controlling the make-up position of the threaded connection at the factory end, the problems of reverse torque loosening and misalignment of shoulder faces that may occur during the assembly of the pipe string threads in the field are solved, so that a stable contact pressure is formed on the contact surface of the threaded connection nose end, thereby effectively solving the anti-corrosion problem of the threaded connection part and realizing the anti-corrosion of the entire pipe string.

[0041] A bimetallic composite oil and casing threaded connection structure and a factory end assembly method, including a pipeline, a coupling made of ordinary carbon steel, an anti-loosening fastening oil and casing thread grease, an anti-galling oil and casing thread grease, and an assembly nipple; the end of the pipeline is processed with an external thread, and a nose shoulder is processed at the front end of the external thread; the carbon steel coupling is a left-right axially symmetric structure, and internal threads matching the external threads of the pipe body are processed at both ends, and a hollow cylindrical section is processed in the middle of the coupling.

[0042] As a specific embodiment, the outer layer matrix of the pipeline is made of ordinary carbon steel, with a yield strength between 55 ksi and 110 ksi and a thickness between 5.5 and 12.7 mm. The inner layer matrix of the pipeline is a corrosion-resistant alloy material not limited to stainless steel, with a yield strength between 45 ksi and 105 ksi and a thickness between 0.5 and 4.5 mm. The composite method of the pipeline is not limited to hydraulic composite, explosive composite, metallurgical composite, etc.

[0043] The threads at both ends of the pipeline can be API threads or non-API special threads.

[0044] Specifically, the cross-sectional thickness of the nose shoulder at the end face of the pipeline is greater than or equal to 2 mm, and the axial length is less than or equal to 4 mm.

[0045] The outer layer carbon steel matrix layer at the end face of the pipeline is first removed by turning or other machining methods with an axial length greater than or equal to 3 mm, and then a corrosion-resistant alloy layer that is fused with both the outer layer matrix and the inner layer matrix is welded with a certain thickness. The thickness of the welded corrosion-resistant alloy layer is 0.5 - 1.0 mm greater than the thickness of the nose shoulder, and the axial length is flush with the end face of the inner corrosion-resistant alloy matrix.

[0046] The axial length of the corrosion-resistant alloy layer welded to both ends of the pipeline is less than or equal to the length of the external thread nose shoulder.

[0047] The threaded structures at both ends of the pipeline are machined after the corrosion-resistant alloy surfacing of the pipe ends is completed.

[0048] The internal thread of the coupling matches the external thread of the pipeline end face.

[0049] The inner diameter of the inner hollow cylindrical section of the coupling is 0.2 - 0.6 mm larger than the outer diameter of the external thread nose shoulder, and the axial length is 0.2 - 0.3 mm less than the axial length of the external thread nose shoulder.

[0050] The material of the assembly nipple is the same as that of the outer layer matrix material of the pipeline, and the assembly nipple is machined with an external thread structure exactly the same as that of the pipeline end face.

[0051] The assembly nipple is machined with a positioning shoulder, and the outer diameter of the positioning shoulder is greater than or equal to the outer diameter of the coupling.

[0052] The axial length of the assembly nipple from the pipe end to the positioning shoulder is 1 / 2 of the axial length of the coupling.

[0053] For the bimetallic composite oil and casing threaded connection structure and the factory-end assembly method, before the threaded connection between the pipeline and the coupling, the threaded connection between the coupling and the assembly nipple is carried out first.

[0054] For the bimetallic composite oil and casing threaded connection structure and the factory-end assembly method, the control standard for the threaded connection between the coupling and the assembly nipple is that the gap between the coupling end face and the positioning shoulder of the assembly nipple is less than or equal to 0.01 mm.

[0055] For the bimetallic composite oil and casing threaded connection structure and the factory-end assembly method, when the external thread of the pipeline is screwed into the coupling, the anti-seize oil and casing thread grease is evenly applied to 2 / 3 of the length on the nose shoulder side of the threaded section, and the locking oil and casing thread grease is evenly applied to 1 / 3 of the length on the pipe body side of the threaded section. The meanings of the 1 / 3 and 2 / 3 positions refer to that the corresponding thread grease application areas cover the specific positions of 1 / 3 or 2 / 3.

[0056] For the bimetallic composite oil and casing threaded connection structure and the factory-end assembly method, the qualified criterion when the external thread of the pipeline is screwed into the coupling is that the make-up torque value reaches the preset value and the torque curve shows a nose shoulder touch signal.

[0057] For the bimetallic composite oil and casing threaded connection structure and the factory-end assembly method, after the external thread of the pipeline is screwed into the coupling, the assembly nipple is removed, and the factory-end assembly is completed.

[0058] The assembly nipple can be reused multiple times.

[0059] A bimetallic composite oil and casing thread connection structure and a factory-end assembly method thereof according to the present invention weld a corrosion-resistant alloy layer with a certain thickness at the nose shoulder of the external thread of the pipe body, and isolate the corrosive medium flowing inside the pipe body through the contact pressure of the corrosion-resistant alloy between the nose shoulders. The assembly nipple is made of the same carbon steel material as the bimetallic composite outer layer, has exactly the same thread structure as the external thread of the pipe body, and the assembly nipple is processed with a positioning shoulder. When performing the factory-end assembly of the bimetallic composite oil and casing thread connection, first control the assembly position of the assembly nipple and the coupling through the positioning shoulder on the assembly nipple, and then use anti-galling oil and casing thread grease and locking oil and casing thread grease on different thread segments at the ends of the bimetallic composite oil and casing. Adopt the make-up torque value and the make-up qualification criterion combined with the shoulder contact to accurately control the position of the factory-end oil and casing thread connection, realize the precise assembly and tight fit of the factory-end of the bimetallic composite oil and casing thread connection, effectively solve the problems of reverse torque loosening at the factory end and the shoulder surface not being in place during the assembly of the pipe string thread connection on site, and make the contact surface at the nose end of the thread connection form a stable contact pressure, thereby effectively solving the anti-corrosion problem at the thread connection part and realizing the overall connection and anti-corrosion function of the entire pipe string.

[0060] Example 1:

[0061] The structure of this example is as Figure 1 shown. The bimetallic composite oil and casing thread connection structure includes a pipeline 1, an assembly nipple 2, a coupling 3 made of ordinary carbon steel, a corrosion-resistant alloy layer 4, anti-loosening and fastening oil and casing thread grease 5 and anti-galling oil and casing thread grease 6; the pipeline 1 is composed of an outer matrix 1-1 and an inner matrix 1-2, and the pipe body end is processed with an external thread 1-3 of the pipe body, and the front end of the external thread of the pipe body is processed with a nose shoulder 1-4 of the external thread of the pipe body; the coupling 3 is a left-right axially symmetric structure, and both ends are processed with internal threads 3-1 matching the external thread of the pipe body, and a hollow cylindrical section 3-2 is processed in the middle of the coupling 3; the assembly nipple 2 is an external thread joint with a positioning shoulder 2-2; when the external thread 1-3 of the pipeline end is assembled with the coupling 3, both anti-loosening and fastening oil and casing thread grease 5 and anti-galling oil and casing thread grease 6 need to be used.

[0062] The outer matrix 1-1 of the pipe body is made of ordinary carbon steel, with a yield strength between 55 ksi and 110 ksi and a thickness between 5.5 and 12.7 mm.

[0063] The inner matrix 1-2 of the pipe body is a corrosion-resistant alloy material not limited to stainless steel, with a yield strength between 45 ksi and 105 ksi and a thickness between 0.5 and 4.5 mm.

[0064] The composite method of the pipeline 1 is not limited to hydraulic composite, explosive composite, metallurgical composite, etc.

[0065] The external thread 1-3 of the pipe body can be API thread or non-API special thread.

[0066] The cross-sectional thickness of the nose shoulder 1-4 of the external pipe thread is greater than or equal to 2.5 mm, and the axial length is less than or equal to 6 mm.

[0067] First, the two end faces of the pipeline 1 are processed by turning or other machining methods to remove the outer layer matrix 1-1 of the carbon steel pipe with an axial length greater than or equal to 3 mm. Then, a corrosion-resistant alloy layer 4 that is molten with both the outer layer matrix 1-1 and the inner layer matrix 1-2 of the pipe is welded. The thickness of the welded corrosion-resistant alloy layer 4 is 0.5-1.0 mm greater than the thickness of the external pipe thread nose shoulder 1-4, and the axial length is flush with the end face of the inner corrosion-resistant alloy matrix 1-2.

[0068] The axial length of the corrosion-resistant alloy layer 4 welded to the two end faces of the pipeline is less than or equal to the length of the external thread nose shoulder 1-4.

[0069] The thread structures at both ends of the pipeline are machined after the welding of the corrosion-resistant alloy layer 4 at the pipe ends is completed.

[0070] The material of the coupling is carbon steel, and the yield strength of the strong material is greater than or equal to that of the outer layer matrix 1-1 of the pipeline.

[0071] The internal thread 3-1 of the coupling matches the external thread 1-3 of the pipe.

[0072] The inner diameter of the inner hollow cylindrical section 3-2 of the coupling is 0.2-0.6 mm greater than the outer diameter of the external thread nose shoulder 1-4, and the axial length is 0.2-0.3 mm less than the axial length of the external thread nose shoulder 1-4.

[0073] The material of the assembly nipple 2 is the same as that of the outer layer matrix 1-1 of the pipe, and the external thread 2-1 of the assembly nipple processed at the pipe end is exactly the same as the pipeline end face.

[0074] The assembly nipple 2 is processed with an assembly nipple positioning shoulder 2-2, and the outer diameter of the assembly nipple positioning shoulder 2-2 is greater than or equal to the outer diameter of the coupling 3.

[0075] The axial length of the assembly nipple 2 from the pipe end face to the assembly nipple positioning shoulder 2-2 is 1 / 2 of the axial length of the coupling 3.

[0076] In this embodiment, before the threaded connection between the pipeline 1 and the coupling 3, the threaded connection between the coupling 3 and the assembly nipple 2 is carried out first. The control standard for the threaded connection between the coupling 3 and the assembly nipple 2 is that the clearance between the end face of the coupling and the positioning shoulder 2-2 of the assembly nipple is less than or equal to 0.01 mm. When the external pipe thread 1-3 of the pipeline 1 is screwed into the coupling 3, the anti-seize oil casing thread grease 6 is evenly applied to 2 / 3 of the length of the nose shoulder side of the threaded section, and the anti-loosening fastening oil casing thread grease 5 is evenly applied to 1 / 3 of the length of the pipe body side of the threaded section. The qualified criterion for the external pipe thread 1-3 when screwed into the coupling 3 is that the make-up torque value reaches the preset value and the torque curve shows a nose shoulder touch signal. After the external pipe thread 1-3 is screwed into the coupling 3, the assembly nipple 2 is removed, and the factory end assembly is completed. The assembly nipple 2 can be reused multiple times.

[0077] Before the threaded connection of the pipeline end and the coupling assembly of the present invention, the end face position of the assembly nipple is accurately controlled by the positioning shoulder between the coupling and the assembly nipple. When the factory end of the pipeline is assembled with the coupling, the make-up position and make-up torque of the factory end are accurately controlled by the assembly nipple. During assembly, it is necessary to use both the anti-loosening fastening oil casing thread grease and the anti-seize oil casing thread grease to achieve the connection and stability of the threaded connection at the factory end (the anti-loosening fastening oil casing thread grease 5 is not applied to the on-site assembly end, but only the anti-seize oil casing thread grease is applied to achieve sealing), effectively solving the problems that may occur during the on-site pipe string threaded connection assembly of the threaded connection, such as the anti-torque loosening of the already connected structure at the factory end and the misalignment of the nose shoulders, making the contact surface of the nose end of the threaded connection form a stable contact pressure, thereby ensuring the overall connection and anti-corrosion function of the entire pipe string.

[0078] The above has introduced in detail a method for end-to-end connection of oil casing with an internal corrosion-resistant layer provided by the embodiments of the present application. The description of the above embodiments is only used to help understand the method and its core idea of the present application; at the same time, for those of ordinary skill in the art, according to the idea of the present application, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to the present application.

[0079] It should also be noted that the term "including", "comprising" or any other variant thereof is intended to cover non-exclusive inclusion, so that a commodity or system including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such commodity or system. Without further limitation, the element defined by the statement "including one..." does not exclude the existence of another identical element in the commodity or system including the said element. "Roughly" means within an acceptable error range, and those skilled in the art can solve the said technical problems within a certain error range and basically achieve the said technical effect.

[0080] The terms used in the embodiments of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The singular forms "a", "the", and "said" used in the embodiments of the present invention and the appended claims are also intended to include the plural forms unless the context clearly dictates otherwise. In this application, the orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", "inner", "outer", "middle", etc. is based on the orientation or positional relationship shown in the drawings. In addition to being used to represent the orientation or positional relationship, some of the above terms may also be used to represent other meanings. For example, the term "upper" may also be used to represent a certain attachment relationship or connection relationship in some cases. For those of ordinary skill in the art, the specific meanings of these terms in this application can be understood according to specific circumstances. The term "and / or" used herein is merely a description of the association relationship between associated objects, indicating that three relationships may exist. For example, A and / or B may represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this text generally represents an "or" relationship between the associated objects before and after.

Claims

1. A method for end-to-end connection of pipelines with an internal corrosion-resistant layer, which realizes the connection between butt-type pipelines with an internal corrosion-resistant layer, is characterized in that The steps of the connection method include: S1. Process external threads on the ends of the two pipeline segments to be connected and on the assembly nipple for positioning, and symmetrically process internal threads on the inner walls of both ends of the connecting collar; S2. Thread-connect the first end of the connecting collar to the assembly nipple, and the thread screwing-in position reaches the positioning position of the assembly nipple; S3. Apply anti-loosening fastening oil casing thread grease and anti-galling oil casing thread grease in sections on the external thread of the first pipeline segment, and thread-connect it to the second end of the connecting collar, and screw it in until the collar end face contacts the assembly nipple; S4. Remove the assembly nipple; S5. Apply anti-galling oil casing thread grease on the external thread of the second pipeline segment, and thread-connect it to the first end of the connecting collar, and screw it in until it contacts the first pipeline segment; The outer surface of the assembly nipple is provided with a positioning shoulder, and the outer diameter at the positioning shoulder is larger than the outer diameter of the external thread of the assembly nipple; In step S2, the assembly nipple is screwed in until the end face of the first end of the connecting collar contacts the positioning shoulder; The distance between the end face of the threaded end of the assembly nipple and the positioning shoulder is equal to 1 / 2 of the length of the connecting collar.

2. The end-to-end connection method of the pipeline with an internal corrosion-resistant layer according to claim 1, characterized in that The external threads on the two pipeline segments are set to be frustum-shaped; Correspondingly, the external thread of the assembly nipple is the same as the frustum-shaped external threads of the two pipeline segments, and both match the internal thread of the connecting collar.

3. The method for end-to-end connection of pipelines with an inner corrosion-resistant layer according to claim 1, characterized in that, Both of the two pipeline segments to be connected include an outer metal pipe and an inner metal pipe; The inner metal pipe at the end to be connected protrudes 3 mm - 6 mm compared to the outer metal pipe, and a corrosion-resistant metal layer is welded to the protruding part of the inner metal pipe.

4. The method for end-to-end connection of pipelines with an inner corrosion-resistant layer according to claim 3, characterized in that, The material of the corrosion-resistant metal layer is fused with both the outer metal pipe and the inner metal pipe.

5. The method for end-to-end connection of pipelines with an inner corrosion-resistant layer according to claim 2, characterized in that, The pipeline cross-section thickness difference generated by the frustum shape ≥ 2 mm, and the axial length ≤ 4 mm.

6. The method for end-to-end connection of pipelines with an internal corrosion-resistant layer according to claim 1, characterized in that, The contact between the end face of the first end of the connecting collar and the positioning shoulder specifically means: the gap between the end face of the first end of the connecting collar and the positioning shoulder of the assembly nipple ≤ 0.01 mm.

7. The method for end-to-end connection of pipelines with an inner corrosion-resistant layer according to claim 1, characterized in that, The qualified criterion for the external threads of the first pipeline segment and the second pipeline segment when screwing into the connecting collar is: the make-up torque value reaches the preset value and the torque curve shows a nose-shoulder touch signal.

8. The end-to-end connection method of the pipeline with an inner corrosion-resistant layer according to claim 3, characterized in that, After assembly, the outer surface of the corrosion-resistant metal layer does not contact the inner surface of the connecting collar, forming a hollow cylindrical section inside the collar.

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