Internal thread structure of oil pipe

Abstract

The invention discloses an oil pipe internal thread structure which comprises a first thread part arranged in the middle of the inner side of an oil pipe, and second thread parts are arranged on the two sides of the first thread part. An inclined surface is formed at the thread end part of the first thread part, and an internal thread crest conical surface is formed at the thread end part of the second thread part; a gap is formed between the inclined surface and the crest conical surface of the internal thread; the inner diameter of the first thread part is gradually increased from the center line to the two ends of the first thread part. When the oil pipe makes contact with the metal surface, the second thread parts can be in direct contact connection with the fixed metal surface, a certain gap is formed between the second thread parts and the metal surface, and the phenomenon of thread gluing after contact is avoided. Therefore, according to the structure disclosed by the invention, the problem of contact stress concentration in the oil pipe can be solved, normal connection and use of the oil pipe are not influenced, thread openings are reduced, and the service life of the oil pipe is prolonged.

Description

Technical Field

[0001] The invention belongs to the technical field of oil pipe connection and relates to an internal thread structure of an oil pipe. Background Art

[0002] Oil pipes are the second largest category of pipe products after casing. A large number of oil pipes are used in oil fields every year. During the use of oil pipes, it is found that the thread galling phenomenon is relatively serious.

[0003] Galling is a type of cold welding that occurs between contacting metal surfaces. It is divided into mild galling, moderate galling, severe galling and extremely severe galling. The geometry and performance of the threads will not be affected after repair of the first two types, while the threads will tear and cannot be repaired due to the latter two types. According to research and relevant literature surveys, contact stress is the main cause of thread galling, and the contact stress of the internal thread is relatively large at both ends of the thread. According to finite element calculations, the maximum position is at the root of the last tooth of the small end that meshes with the external thread. The contact stress is too large, causing thread galling and shortening the service life of the oil pipe. Summary of the invention

[0004] The purpose of the present invention is to solve the problem that the thread galling phenomenon of the oil pipe in the prior art is relatively serious, causing damage to the thread structure, the thread structure cannot be repaired, and the service life of the thread is shortened.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] An internal thread structure of an oil pipe comprises a first threaded portion provided in the middle of an inner side of the oil pipe, and second threaded portions are provided on both sides of the first threaded portion;

[0007] The thread end of the first thread portion forms an inclined surface, and the thread end of the second thread portion forms an internal thread top conical surface;

[0008] There is a gap between the inclined surface and the internal thread top cone surface;

[0009] The inner diameter of the first threaded portion gradually increases toward both ends along the center line thereof.

[0010] A further improvement of the present invention is:

[0011] The tooth profile height of the second thread portion is greater than the tooth profile height of the first thread portion.

[0012] A turning depth slope is formed at a connection point where the first thread portion and the second thread portion are close to each other.

[0013] The vertical plane at the center of the oil pipe is the center plane of the coupling;

[0014] The angle between the turning depth slope and the center plane of the coupling is greater than 0° and less than 90°.

[0015] A chamfer is formed between the turning depth inclined surface and the end portion close to the inclined surface.

[0016] The radius of the chamfer is 0.2 mm-2 mm.

[0017] The clearance between the inclined surface and the internal thread top cone surface meets the following requirements: 0.5*h s <w<h s +0.5mm

[0018] Among them, h s It represents the height of the thread of the first threaded portion; w represents the gap between the inclined surface and the cone surface of the internal thread top.

[0019] The first threaded portions are symmetrically distributed on both sides of a center plane of the coupling inside the oil pipe.

[0020] The distance from one end of the inclined surface close to the second threaded portion to the pipe end tightening plane is greater than or equal to 4 thread pitches and less than or equal to 5 thread pitches.

[0021] The end surface of each thread tooth of the first threaded portion is a plane.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The present invention discloses an internal thread structure of an oil pipe, wherein a first thread portion and a second thread portion are provided inside the oil pipe, and a gap exists between the inclined surface and the cone surface of the internal thread top, thereby ensuring that the inner diameter of the oil pipe corresponding to the second thread portion is larger than the inner diameter of the oil pipe corresponding to the first thread portion. When the oil pipe contacts a metal surface, the second thread portion will be directly contacted and connected with the fixed metal surface, and a certain gap will be formed between the second thread portion and the metal surface, thereby avoiding the phenomenon of thread sticking after contact. Since the main stress points of the oil pipe are at the second thread portions near the two ends during connection, the structure disclosed by the present invention can solve the problem of contact stress concentration inside the oil pipe, and also does not affect the normal connection and use of the oil pipe, thereby reducing the occurrence of thread sticking and extending the service life of the oil pipe.

[0024] Furthermore, in the present invention, a chamfer is formed between the turning depth inclined surface and the end portion close to the inclined surface, so as to avoid damage to the metal parts to be connected during connection and installation. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0026] Figure 1 It is a structural schematic diagram of the present invention;

[0027] Figure 2 It is a partial enlarged view of the present invention;

[0028] Figure 3 This is a schematic structural diagram of the outer diameter of the first oil pipe in an embodiment of the present invention;

[0029] Figure 4 Schematic diagram of the structure of the second type of oil pipe outer diameter in an embodiment of the present invention.

[0030] Among them: 1-coupling center plane; 2-pipe end machine tightening plane; 3-inclined surface; 4-internal thread top cone surface; 5-turning depth inclined surface. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0032] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0034] In the description of the embodiments of the present invention, it should be noted that if the terms "upper", "lower", "horizontal", "inner", etc. indicate an orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the invention is usually placed when in use, it is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0035] In addition, if the term "horizontal" appears, it does not mean that the component must be absolutely horizontal, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", which does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0036] In the description of the embodiments of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0037] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0038] See also Figures 1 to 4 The embodiment of the present invention discloses an internal thread structure of an oil pipe to solve the problem of thread sticking. The thread sticking is caused by excessive local contact stress on the tooth surface, resulting in plastic deformation.

[0039] During the process of making up the oil pipe, after the oil pipe is tightened by hand and machine, finite element calculation is performed. The maximum stress of the internal thread is at its small end, at the root of the last tooth that meshes with the external thread. The present invention solves this problem by adding an inclined surface with the same thread taper to the internal thread.

[0040] include:

[0041] Coupling center plane 1; pipe end machine tightening plane 2; inclined surface 3; internal thread top cone surface 4 and turning depth inclined surface 5;

[0042] Example 1

[0043] The present embodiment discloses an internal thread structure of an oil pipe, comprising a first threaded portion opened in the middle of the inner side of the oil pipe, and second threaded portions opened on both sides of the first threaded portion; a bevel 3 is formed at the end of the thread of the first threaded portion, and an internal thread top cone surface 4 is formed at the end of the thread of the second threaded portion; a gap exists between the bevel 3 and the internal thread top cone surface 4; the inner diameter of the first threaded portion gradually increases along its center line toward both ends.

[0044] In this embodiment, a first threaded portion and a second threaded portion are provided inside the oil pipe, and a gap is provided between the inclined surface and the cone surface of the internal thread top, thereby ensuring that the inner diameter of the oil pipe corresponding to the second threaded portion is larger than the inner diameter of the oil pipe corresponding to the first threaded portion. When the oil pipe contacts the metal surface, the second threaded portion will be directly contacted and connected with the fixed metal surface, and a certain gap will be formed between the second threaded portion and the metal surface to avoid the phenomenon of thread sticking after contact. Since the main stress points of the oil pipe are at the second threaded portions near the two ends during connection, the structure disclosed in the present invention can solve the problem of contact stress concentration inside the oil pipe without affecting the normal connection and use of the oil pipe, thereby reducing the occurrence of thread sticking and extending the service life of the oil pipe.

[0045] Example 2

[0046] The present embodiment discloses an internal thread structure of an oil pipe, comprising a first threaded portion opened in the middle of the inner side of the oil pipe, and second threaded portions opened on both sides of the first threaded portion; the thread ends of the first threaded portion form an inclined surface 3, and the thread ends of the second threaded portion form an internal thread top cone surface 4; there is a gap between the inclined surface 3 and the internal thread top cone surface 4; the inner diameter of the first threaded portion gradually increases toward both ends along its center line, the tooth profile height of the second threaded portion is greater than the tooth profile height of the first threaded portion, and the second threaded portion is mainly used for fixed connection with the metal parts to be connected.

[0047] Example 3

[0048] The present embodiment discloses an internal thread structure of an oil pipe, comprising a first threaded portion opened in the middle of the inner side of the oil pipe, and second threaded portions opened on both sides of the first threaded portion; a bevel 3 is formed at the end of the thread of the first threaded portion, and an internal thread top cone 4 is formed at the end of the thread of the second threaded portion; a gap exists between the bevel 3 and the internal thread top cone 4; the inner diameter of the first threaded portion gradually increases toward both ends along its center line, and a turning depth bevel 5 is formed between the end of the bevel 3 close to the second threaded portion and the end close to the second threaded portion.

[0049] The gap between the inclined surface 3 and the internal thread top cone surface 4 in this embodiment is the vertical height of the turning depth inclined surface 5.

[0050] In this embodiment, the turning depth slope 5 is a slope, which takes the end of the first thread tooth adjacent to the second thread part as the starting point, and the two adjacent thread tooth ends are connected to form the inclined turning depth slope 5.

[0051] Example 4

[0052] The present embodiment discloses an internal thread structure of an oil pipe, comprising a first threaded portion opened in the middle of the inner side of the oil pipe, and second threaded portions opened on both sides of the first threaded portion; a bevel 3 is formed at the end of the thread of the first threaded portion, and an internal thread top cone 4 is formed at the end of the thread of the second threaded portion; a gap exists between the bevel 3 and the internal thread top cone 4; an inner diameter of the first threaded portion gradually increases toward both ends along its center line, and a turning depth bevel 5 is formed between the end of the bevel 3 close to the second threaded portion and the end close to the second threaded portion, and the vertical plane at the center of the oil pipe is the center plane 1 of the coupling; an angle between the turning depth bevel 5 and the center plane 1 of the coupling is greater than 0° and less than 90°.

[0053] The coupling center plane 1 described in this embodiment is an interface vertically distributed between the inside of the oil pipe and the oil pipe. There is a pipe end tightening plane 2 along the coupling center plane 1 toward the second threaded portion. The API or standard stipulates that the horizontal distance between the coupling center plane 1 and the pipe end tightening plane 2 is 12.7 mm.

[0054] Example 5

[0055] The present embodiment discloses an internal thread structure of an oil pipe, comprising a first threaded portion opened in the middle of the inner side of the oil pipe, and second threaded portions opened on both sides of the first threaded portion; a bevel 3 is formed at the end of the thread of the first threaded portion, and an internal thread top cone 4 is formed at the end of the thread of the second threaded portion; a gap exists between the bevel 3 and the internal thread top cone 4; an inner diameter of the first threaded portion gradually increases toward both ends along its center line, and a turning depth bevel 5 is formed between the end of the bevel 3 close to the second threaded portion and the end close to the second threaded portion, and the vertical plane at the center of the oil pipe is the center plane 1 of the coupling; the angle between the turning depth bevel 5 and the center plane 1 of the coupling is greater than 0° and less than 90°; a chamfer 6 is formed between the turning depth bevel 5 and the end close to the bevel 3.

[0056] The chamfer 6 described in the embodiment of the present invention is that when the junction of the first threaded portion and the second threaded portion is located at the thread, a chamfer 6 is provided at the end face at the thread to avoid damage to the metal parts to be connected during connection and installation.

[0057] Example 6

[0058] The present embodiment discloses an internal thread structure of an oil pipe, comprising a first threaded portion provided in the middle of the inner side of the oil pipe, and second threaded portions provided on both sides of the first threaded portion; a bevel 3 is formed at the end of the thread teeth of the first threaded portion, and an internal thread top cone surface 4 is formed at the end of the thread teeth of the second threaded portion; there is a gap between the bevel 3 and the internal thread top cone surface 4; the inner diameter of the first threaded portion gradually increases toward both ends along the center line thereof, and the gap between the bevel 3 and the internal thread top cone surface 4 satisfies: 0.5*h s <w<h s +0.5mm

[0059] Among them, h s It represents the height of the thread of the first threaded portion; w represents the gap between the inclined surface and the cone surface of the internal thread top.

[0060] Example 7

[0061] The present embodiment discloses an internal thread structure of an oil pipe, comprising a first threaded portion opened in the middle of the inner side of the oil pipe, and second threaded portions opened on both sides of the first threaded portion; the thread ends of the first threaded portion form an inclined surface 3, and the thread ends of the second threaded portion form an internal thread top cone surface 4; there is a gap between the inclined surface 3 and the internal thread top cone surface 4; the inner diameter of the first threaded portion gradually increases toward both ends along its center line, the first threaded portion is symmetrically distributed along both sides of the center plane 1 of the coupling inside the oil pipe, and the second threaded portion is symmetrically distributed along both sides of the first threaded portion.

[0062] Example 8

[0063] The present embodiment discloses an internal thread structure of an oil pipe, comprising a first threaded portion opened in the middle of the inner side of the oil pipe, and second threaded portions opened on both sides of the first threaded portion; a bevel 3 is formed at the end of the thread of the first threaded portion, and an internal thread top cone 4 is formed at the end of the thread of the second threaded portion; a gap exists between the bevel 3 and the internal thread top cone 4; an inner diameter of the first threaded portion gradually increases toward both ends along its center line, and a distance from one end of the bevel 3 close to the second threaded portion to a pipe end tightening plane 2 is greater than or equal to 4 pitches and less than or equal to 5 pitches.

[0064] Example 9

[0065] The present embodiment discloses an internal thread structure of an oil pipe, comprising a first threaded portion opened in the middle of the inner side of the oil pipe, and second threaded portions opened on both sides of the first threaded portion; the thread ends of the first threaded portion form an inclined surface 3, and the thread ends of the second threaded portion form an internal thread top cone surface 4; there is a gap between the inclined surface 3 and the internal thread top cone surface 4; the inner diameter of the first threaded portion gradually increases along its center line toward both ends, and the end face of each thread of the first threaded portion is a plane.

[0066] The embodiment of the present invention does not limit the end surface structure of each thread of the first threaded portion, as long as there is a gap between the first threaded portion and the metal part to be connected.

[0067] Furthermore, in the embodiments disclosed in the present invention, in application, the pitch and tooth profile height of the first thread and the second thread portion in the oil pipe are in accordance with the thread parameters specified in the API or standards.

[0068] The embodiments of the present invention disclose two specific applications:

[0069] The first one:

[0070] For the inner thread of the non-thickened oil pipe with an outer diameter of 88.9 mm, see Figure 3 :

[0071] The specific limitations of the oil pipe thread disclosed in this embodiment are:

[0072] The distance from the starting point of the turning depth bevel 5 to the tightening plane 2 of the pipe end is 8.78 mm, the angle between the turning depth bevel 5 and the center plane 1 of the coupling is 48°, the distance between the designed bevel 3 and the internal thread top cone surface 4 is 0.78 mm, and the radius of the chamfer 6 is 1 mm.

[0073] Second type:

[0074] Thickened oil pipe internal thread with an outer diameter of 88.9 mm, see Figure 4 :

[0075] In this structure, the distance from the starting point of the turning depth bevel 5 to the tightening plane 2 of the pipe end is 9.53 mm, the angle between the turning depth bevel 5 and the center plane 1 of the coupling is 25°, the distance between the designed bevel 3 and the internal thread top cone surface 4 is 1.82 mm, and the radius of the chamfer 6 is 0.4 mm.

[0076] The internal thread structure of the oil pipe disclosed in the embodiment of the present invention processes a bevel on the small end of the internal thread, so that when the external thread is engaged with it, there is basically no contact between the external thread tooth top and the internal thread tooth root, thereby effectively reducing the problem of stress concentration on the internal thread and alleviating the problem of sticking. According to finite element calculation, the stress at the large end of the external thread after machine tightening is reduced by 17% to 31% compared with the stress of the original structure, which can greatly improve the service life of the oil pipe.

[0077] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An internal thread structure of an oil pipe, characterized in that: It comprises a first threaded portion provided in the middle of the inner side of the oil pipe, and second threaded portions are provided on both sides of the first threaded portion; The thread end of the first thread portion forms an inclined surface (3), and the thread end of the second thread portion forms an internal thread crest conical surface (4); There is a gap between the inclined surface (3) and the internal thread top cone surface (4); The inner diameter of the first threaded portion gradually increases toward both ends along the center line thereof.

2. The internal thread structure of an oil pipe according to claim 1, characterized in that: The tooth profile height of the second thread portion is greater than the tooth profile height of the first thread portion.

3. The internal thread structure of an oil pipe according to claim 1, characterized in that: A turning depth slope (5) is formed at a connection point where the first threaded portion and the second threaded portion are close to each other.

4. The internal thread structure of an oil pipe according to claim 3, characterized in that: The vertical plane at the center of the oil pipe is the center plane of the coupling (1); The angle between the turning depth inclined surface (5) and the coupling center plane (1) is greater than 0° and less than 90°.

5. The internal thread structure of an oil pipe according to claim 3, characterized in that: A chamfer (6) is formed between the end portions of the turning depth inclined surface (5) and the inclined surface (3) that are close to each other.

6. The internal thread structure of an oil pipe according to claim 5, characterized in that: The radius of the chamfer (6) is 0.2 mm-2 mm.

7. The internal thread structure of an oil pipe according to claim 1, characterized in that: The clearance between the inclined surface (3) and the internal thread top cone surface (4) satisfies: 0.5*h s <w<h s +0.5mm Among them, h s represents the height of the thread of the first threaded portion; w represents the gap between the inclined surface (3) and the cone surface (4) of the internal thread top.

8. The internal thread structure of an oil pipe according to claim 1, characterized in that: The first threaded portions are symmetrically distributed on both sides of a coupling center plane (1) inside the oil pipe.

9. The internal thread structure of an oil pipe according to claim 1, characterized in that: The distance between the end of the inclined surface (3) close to the second threaded portion and the pipe end tightening plane (2) is greater than or equal to 4 thread pitches and less than or equal to 5 thread pitches.

10. The internal thread structure of an oil pipe according to claim 1, characterized in that: The end surface of each thread tooth of the first threaded portion is a plane.

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