Tubular Threaded Joints

Abstract

A threaded joint (1) having a longitudinal axis (x), wherein a first tubular component (C1) and a second tubular component (C2) are threaded together, a first axial length BSL between a female internal stop surface (23) and a female external stop surface (21) is greater than a second axial length PSL between a male internal stop surface (13) and a male external stop surface (11), and the first axial length BSL and the second axial length PSL form a gap (30) between the male external stop surface (11) and the female external stop surface (21), the gap (30) being closeable by contact between the male external stop surface (11) and the female external stop surface (21) when an axial compressive load is applied.

Description

[Technical field]

[0001] The present invention relates to the field of tubular threaded joints, in particular metallic tubular threaded joints used in the oil and gas, energy or storage industries, in particular in hydrocarbon well applications, hydrocarbon transportation, carbon capture or geothermal energy. [Background technology]

[0002] By "threaded joint" is meant here an assembly consisting of substantially tubular components screwed together. The tubular components may be tubes or any other type of connection part commonly used in the field of the invention, such as sleeves. Such metal tubular parts preferably have an elastic limit of 450 MPa or more.

[0003] Each tubular component has an end provided with a male or female threaded region intended to be screwed onto a corresponding end of a similar component. When assembled in this manner, the threaded tubular components form what is known as a joint or connection.

[0004] These joints are subjected to a wide variety of stresses, including tensile stress or axial compression, internal or external fluid pressure, and bending or torsion, which may be combined and of varying strengths. Flow must be ensured despite these stresses and despite harsh workplace conditions.

[0005] In recent years, the demands of operators in the field of the invention have changed, so that operators increasingly demand threaded joints with better resistance to all these stresses, especially when the stress loads applied to the joint exceed the elastic limits of said joint.

[0006] To address this requirement, the prior art describes in patent EP 3572612 a tubular threaded joint comprising a tubular female end extending from the body of a first tubular member and a tubular male end extending from the body of a second tubular member. This joint has two stepped threads, between which a first stop is arranged. The joint further comprises a second stop formed by a male free end and a female inner shoulder. The threads of the tubular components forming this joint have load flanks and stub flanks with exactly the same pitch. A disadvantage of such joints is that there is residual axial play in the load flank and / or the stub flank of the thread. If such joints are subjected to high mechanical stresses, there is a high risk that this axial play will cause leakage. Due to this axial play, the grease that is applied during the joining, especially to limit the risk of leakage, is stored in the gap formed between the load flank and the stub flank. Thus, when such a joint switches from a first tensile stress state to a second compressive stress state, the gaps that were open in the first stress state are closed, thereby reopening the gaps between the flanks of the threads that were in contact in the first stress state but are no longer in contact in the second stress state. Such switching from one stress state to another causes the migration of grease from the gaps that were open in the first stress state of the joint to the gaps that are formed when the joint switches to the second stress state. Due to such migration of grease in the threads, the load flank and the stub flank are alternately spaced apart from each other and then in direct contact and vice versa, depending on the stress state of the joint. The fact that the flanks of the threads are periodically in direct contact significantly increases the risk of seizure, which significantly reduces the life of the joint. As a result, such joints have to be replaced more frequently, which makes maintenance more complicated for the operator and generates additional operating costs. Summary of the Invention [Problem to be solved by the invention]

[0007] In order to overcome the above-mentioned drawbacks, the first object of the present invention is to improve the resistance of the threaded joint to mechanical stress while significantly reducing the risk of seizure in the threaded joint.Furthermore, the second object of the present invention is to reduce the operating costs caused by the use of the threaded joint while simplifying the on-site operation. [Means for solving the problem]

[0008] The present invention therefore provides a threaded joint having a longitudinal axis x, said joint comprising a first tubular component and a second tubular component, said first tubular component and said second tubular component being threadedly connected to one another, said first component comprising a first tube and a male element arranged at one end of said first tube, said male element continuing from said first tube to a male internal stop surface of said male element, said male element having a male external stop surface, a first male threaded section having at least a self-locking variable width thread profile, said male internal stop surface, a second tube and a female element arranged at one end of said second tube, said female element continuing from said second tube to a female external stop surface of said female element, said female element having a female internal stop surface, a first female threaded section having at least a self-locking variable width thread profile, and a first axial length BSL between the female internal stop surface and the female external stop surface. The female external stop surface is larger than a second axial length PSL between the male internal stop surface and the male external stop surface, and the first axial length BSL and the second axial length PSL are such that a gap is formed between the male external stop surface and the female external stop surface, said gap being closeable by contact between the male external stop surface and the female external stop surface when an axial compressive load is applied.

[0009] The gap formed between the male and female external stop surfaces serves to reduce the compressive forces applied to the flanks of the thread when the applied compressive load exceeds the elastic limit of the joint. Thus, when the tubular components are screwed together and an axial compressive load is applied, the male and female external stop surfaces come into contact when the axial compressive load exceeds the elastic limit of the thread. By this means, the compressive load is immediately distributed on the one hand on the relief surfaces of the thread and on the other hand on the surfaces of the male and female external stoppers. Such a distribution of loads serves to maintain the fluid-tightness provided by the threading. Such a structure of the male and female elements therefore provides a joint that functions better under compression, especially beyond its elastic limit.

[0010] The inside diameter of the fitting decreases axially from the outer stop surface to the inner stop surface. Thus, the outer stop surface is necessarily higher than the surface of the intermediate stop, which is necessarily higher than the inner stop surface. As a result, the fact that the stop contact occurs between the outer stop surfaces provides a larger stop contact surface and therefore a larger torque capacity compared to fittings in which the stop contact occurs at an inner or intermediate shoulder. In other words, the fact that the stop contact occurs between the outer stop surfaces allows the fitting to withstand a larger axial compressive load compared to stop contact at an inner or intermediate shoulder.

[0011] Self-locking variable width threads, such as those used in the present invention, prevent the formation of gaps in the threads of the joint. Thus, when the first and second tubular components are screwed together and no axial compressive load is applied, the integrity of the joint, in particular its fluid-tightness, is entirely provided by the torque generated by the contact between the load relief and stub relief of the thread of the first tubular component, on the one hand, and the load relief and stub relief of the thread of the second tubular component, on the other hand. As a result, in such joints, it is not necessary to use grease to ensure fluid-tightness, which reduces the amount of grease used and therefore reduces the operating costs. Moreover, since there is no axial play between the threads, the risk of seizing during changes in the stress state, for example when switching from a traction state to a compression state, is almost zero, as a result of which the service life of such joints is significantly increased.

[0012] According to one embodiment, the male element comprises a male outer seat extending from the male outer stop surface to the male threads.

[0013] According to one embodiment, the male external stop surface is inclined by an angle α to a first axis y, said first axis y being perpendicular to the longitudinal axis x, and the female external stop surface is inclined by an angle β to a second axis y", said second axis y" being perpendicular to the longitudinal axis x, and said angles α and β are such that the male external stop surface and the female external stop surface are substantially parallel. In other words, angles α and β are substantially equal.

[0014] These features mean that regardless of the values ​​of angles α and β, the male and female exterior stop surfaces will always face each other, thereby maximizing the contact area between them and helping to improve the performance of the joint under compression.

[0015] For clarity, all values ​​given for angle α in this application are the angle measured in a counterclockwise direction between the male exterior stop surface and axis y. Similarly, all values ​​given for angle β are the angle measured in a counterclockwise direction between the female exterior stop surface and axis y″.

[0016] According to one embodiment, the axis y and the male external stop surface are coaxial cables and the axis y″ and the female external stop surface are coaxial cables. The angles α and β thus formed are either zero angles or linear angles. A zero angle is an angle having a value of 0° and a linear angle is an angle having a value of 180°.

[0017] According to one embodiment, the angles α and β are both 0° or 180°.

[0018] According to one embodiment, the angles α and β are 0°≦α≦30° and 0°≦β≦30°. Above 30°, when an axial compressive load is applied to the joint, the lip starts to bend and there is a risk of the lip breaking.

[0019] According to one embodiment, the angles α and β are such that 0°≦α≦10° and 0°≦β≦10°.

[0020] According to one embodiment, the angles α and β are 0°≦α≦5° and 0°≦β≦5°.

[0021] When the joint is subjected to an axial compressive load, especially when said load exceeds the elastic limit of said joint, the end of the female element tends to experience mechanical forces directed radially towards the outside of the tube. This phenomenon tends to reduce the contact area between the male and female external stop faces, which tends to deteriorate the compression performance of the joint. Such an angle inclination value of the male and female external stop faces allows the forces to be directed radially towards the inside of the tube, thereby avoiding this phenomenon.

[0022] According to one embodiment, the gap has an axial length of 0.10 mm to 1.75 mm. Preferably, the gap has an axial length of 0.10 mm to 0.82 mm, more preferably 0.10 mm to 0.63 mm. Ideally, the gap has an axial length of 0.10 mm to 0.50 mm. This allows to close the gap, thereby optimizing the compressive strength according to the compression capabilities related to the field of the invention.

[0023] Preferably, the gap has an axial length as follows: BSL × (0.5%) / 4≦gap(30)≦BSL × 0.7% (BSL is in mm). The minimum value reduces the compressive force applied to the flanks of the threads when the applied compressive load exceeds the elastic limit of the joint from 25% of the compressive capacity of the joint according to the invention. The maximum value reduces the compressive force applied to the flanks of the threads when the applied compressive load reaches 100% of the compressive capacity of the joint according to the invention.

[0024] (definition) In the present application, "threading" refers to the connection of tubular components to one another to form a joint suitable for use in the field of the present application. By way of example, the properties of a joint required for use in the field of the present invention may include fluid-tightness.

[0025] "Axial length" means the length extending and measured along the longitudinal axis x.

[0026] For clarity, the means for measuring the first axial length BSL and the second axial length PSL are given below. Thus, the first axial length BSL can be measured from the first female inner radial end to the second female inner radial end. The distance between the points radially projected on the axis x is then measured. Similarly, the second axial length PSL can be measured from the first male inner radial end to the second male inner radial end. Thus, the distance between the points radially projected on the axis x is also measured.

[0027] "Self-locking thread" means that the thread width of the male thread increases axially in a first direction and the thread width of the female thread increases axially in a second direction, said second direction being opposite to the first direction. The width of a self-locking thread such as that used in the present invention may vary axially, i.e. along the longitudinal axis x, and / or radially, i.e. along an axis perpendicular to the longitudinal axis x. If the thread width varies radially, the thread has a dovetail profile.

[0028] In a "wedge" thread cutting, the threaded portion has different pitch values ​​for the load relief and the stub relief, and thus the face width of the helix in this type of thread cutting increases with each turn of the helix from one end to the other, and the hollow defined between the turns of the helix decreases with each turn of the helix.

[0029] It should be noted that according to the present invention, the stop surfaces may, but do not necessarily, make stop contact when the joint is in the threaded condition.

[0030] The invention can be more clearly understood in the following detailed description of some particular embodiments of the invention, given by way of non-limiting example only, with reference to the accompanying drawings, in which further objects, details, features and advantages will be more clearly presented.

[0031] However, it should be understood that the application is not limited to the arrangement, structure, features, embodiments and precise appearance shown. The drawings are not to scale and are not intended to limit the claims to the embodiments shown in these drawings. Thus, where features recited in a claim follow by reference, it should be understood that said reference is provided solely to aid in the understanding of the claim and in no way limits the scope of said claim. [Brief description of the drawings]

[0032] [Figure 1]FIG. 1 is a schematic longitudinal cross-sectional view of a threaded joint in which two tubular components are threaded together (threading not shown) according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic enlarged view of detail A of the threaded joint according to the invention in FIG. 1 (threading not shown). [Diagram 3] FIG. 3 is a schematic enlarged view of a variant of detail A of a threaded joint (threading not shown) according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] FIG. 1 shows a longitudinal section of a threaded joint 1 according to an embodiment of the invention, comprising a first tubular component C1 and a second tubular component C2 threaded to one another.

[0034] The first tubular component C1 comprises a first tube 10 and a male element 15. The male element 15 is arranged at one end of the first tube 10. The male element 15 is directly adjacent to the first tube 10. The male element 15 extends axially from a male external stop surface 11 to a male internal stop surface 13. From the male external stop surface 11, the male element 15 comprises successively a male external seat 14, an external threaded portion 12 with a self-locking variable width thread profile (not shown) and a male internal stop surface 13. The threading is not described in detail in this patent application, but the skilled person may refer to patent EP2999841 which describes a self-locking threading that can be used in any embodiment of the present invention.

[0035] The male outer stop surface 11 extends radially between a first male outer radial end 16 and a first male inner radial end 18. The first male inner radial end 18 may be a fillet having a radius of curvature between 0.1 mm and 5.0 mm that connects the male outer stop surface 11 and the male outer sheet 14.

[0036] The male inner stop surface 13 extends radially between a second male outer radial end 17 and a second male inner radial end 19. The second male outer radial end 17 and the second male inner radial end 19 have respective radii of curvature and may each be deburred or rounded immediately adjacent the male inner stop surface 13.

[0037] The male outer seat 14 extends from the first male inner radial end 18 to the beginning of the male threaded portion 12. The male outer seat 14 has an unthreaded surface which may have a cylindrical or frusto-conical shape. In FIG. 1, the male outer seat 14 has a cylindrical unthreaded surface which is perpendicular to the male outer stop surface 11, in other words the unthreaded surface of the male outer seat 14 and the male outer stop surface 11 are perpendicular.

[0038] The male threads 12 are conical, e.g., having a cone half angle of 0.5°-5°, preferably 1°-3°. The male threads 12 are disposed on the exterior of the male element and extend from a male outer seat 14 to a second male outer radial end 17. The threads (not shown) of the threads 12 have a self-locking, variable width thread profile, such as a "wedge" thread.

[0039] The second tubular component C2 comprises a second tube 20 and a female element 25. The female element 25 is disposed at one end of the second tube 20. The female element 25 is directly adjacent to the second tube 20. The female element 25 extends axially from a female external stop surface 21 to a female internal stop surface 23. From the female external stop surface 21, the female element 25 comprises, in succession, a female lip 24, a threaded portion 12 having a self-locking variable width thread profile (not shown), a female internal seat 28 and the female internal stop surface 23.

[0040] The female external stop surface 21 and the male external stop surface 11 are arranged opposite each other to define a gap 30. In Figure 1, the gap 30 has an axial length of 0.43 mm.

[0041] The female outer stop surface 21 extends radially between a first female outer radial end 29 and a first female inner radial end 26. The first female inner radial end 26 may be deburred or rounded and has a radius of curvature between 0.1 mm and 5.0 mm and is directly adjacent to the female outer stop surface 21.

[0042] The female internal stop surface 23 faces the male internal stop surface 13 and is spaced therefrom at an axial distance of, for example, 2 mm to 15 mm. The female internal stop surface 23 extends from the second female internal radial end 27 to the female internal seat 28. The female internal stop surface 23 may be straight or may be rounded to form a fillet. In FIG. 1, the female internal stop surface 23 forms a fillet with a radius of curvature of, for example, 0.2 mm to 6.0 mm, preferably 0.5 mm to 1.5 mm.

[0043] The female lip 24 has an inner surface 31 that faces the male outer seat 14. The inner surface 31 is an unthreaded surface and has a cylindrical shape. The inner surface 31 extends from the first female radially inner end 26 to a distal thread relief surface 32 of the female threaded portion 22.

[0044] The conicity of the female threads 22 is substantially equal to the conicity of the male threads 12. The female threads 22 are disposed within the female element 25 and extend from a female internal seat 28 to a distal thread relief 32. The threads (not shown) of the threads 22 have a self-locking, variable width thread profile, such as a "wedge" thread.

[0045] The female inner seat 28 is immediately adjacent the fillet formed by the female inner stop surface 27 and extends to the female threads 22. The female inner seat 28 has an unthreaded surface that may have a cylindrical or frusto-conical shape. In FIG. 1, the female inner seat 28 has a cylindrical unthreaded surface.

[0046] The first axial length BSL extends between the first female radially inner end 26 and the second female radially inner end 27 and is measured axially, so that the distance is measured between radially projected points on the axis x. The first axial length BSL may be between 60 mm and 300 mm, preferably between 100 mm and 250 mm, and even more preferably between 110 mm and 225 mm. In FIG. 1, the first axial length BSL is 217 mm.

[0047] A second axial length PSL extends and is measured axially between the first male inner radial end 18 and the second male inner radial end 19, thus measuring the distance between radially projected points on the axis x. The second axial length PSL may be between 60 mm and 300 mm, preferably between 100 mm and 250 mm, and even more preferably between 110 mm and 225 mm. In FIG. 1, the second axial length PSL is 208 mm.

[0048] FIG. 2 is an enlarged view of detail A of the threaded joint shown diagrammatically in FIG.

[0049] The gap 30 is defined by the male external stop surface 11 and the female external stop surface 21. The male external stop surface 11 and the female external stop surface 21 are parallel. According to the embodiment shown in FIG. 2, which corresponds to the embodiment of FIG. 1, the male external stop surface 11 and the female external stop surface 21 are perpendicular to the longitudinal axis x of the threaded joint 1. In other words, according to this embodiment, the male external stop surface 11 forms an angle α with the axis y, which is a straight angle or a zero angle. Similarly, the female external stop surface 21 forms an angle β with the axis y'', which is a straight angle or a zero angle, and the axes y and y'' are both perpendicular to the longitudinal axis x. Thus, the gap 30 formed between the male external stop surface 11 and the female external stop surface 21 has an axial length of 0.10 mm to 1.75 mm. In the embodiment shown in FIG. 2, the gap 30 has an axial length of 0.43 mm.

[0050] FIG. 3 is an enlarged view of a variant of detail A shown diagrammatically in FIG. 2. According to this variant, the male external stop surface 11 is inclined by an angle α to the axis y, and the female external stop surface 21 is inclined by an angle β to the axis y″. Axes y and y″ are both perpendicular to the longitudinal axis x. The angle α may be between 0.1° and 30°, preferably between 0.1° and 10°, and even more preferably between 0.1° and 5°. The angle β may be between 0.1° and 30°, preferably between 0.1° and 10°, and even more preferably between 0.1° and 5°. In the embodiment of FIG. 3, the angles α and β are both 15°. The gap 30 formed between the male external stop surface 11 and the female external stop surface 21 thus has an axial length of between 0.10 mm and 1.75 mm. In the embodiment shown in FIG. 3, the gap 30 has an axial length of 0.43 mm.

Claims

1. A threaded joint (1) having a longitudinal axis (x), said joint comprising a first tubular component (C1) and a second tubular component (C2), said first tubular component (C1) and said second tubular component (C2) being threadedly fastened to one another; - said first component (C1) comprises a first tube (10) and a male element (15) arranged at one end of said first tube (10); The male element (15) is inserted from the first tube (10) into the male element: a male outer stop surface (11); at least a first male threaded portion (12) having a self-locking variable width thread profile; Male internal stop surface (13) Continuously equipped with said second constituent element (C2) comprises a second tube (20) and a female element (25) arranged at one end of said second tube (20); The female element (25) is connected to the second tube (20) via the female element: That is, a female internal stop surface (23); At least a first female threaded portion (22) having a self-locking variable width thread profile, a female lip (24), and a female external stop surface (21). 21, a first axial length BSL between the female internal stop surface (23) and the female external stop surface (21) is greater than a second axial length PSL between the male internal stop surface (13) and the male external stop surface (11); The first axial length BSL and the second axial length PSL are set so that a gap (30) is formed between the male external stop surface (11) and the female external stop surface (21), and the gap (30) can be closed by contact between the male external stop surface (11) and the female external stop surface (21) when an axial compressive load is applied. Threaded joint (1).

2. 2. A tubular fitting (1) according to claim 1, characterized in that the male external stop surface (11) is inclined by an angle α to a first axis (y), which is perpendicular to the longitudinal axis (x), and the female external stop surface (21) is inclined by an angle β to a second axis (y), which is perpendicular to the longitudinal axis (x), and the angles α and β are such that the male external stop surface (11) and the female external stop surface (21) are substantially parallel.

3. 3. A tubular joint (1) according to claim 2, characterized in that the angles α and β are in the range 0°≦α≦30° and 0°≦β≦30°.

4. 3. A tubular joint (1) according to claim 2, characterized in that the angles α and β are in the range 0°≦α≦10° and 0°≦β≦10°.

5. 3. A tubular joint (1) according to claim 2, characterized in that the angles α and β are in the range 0°≦α≦5° and 0°≦β≦5°.

6. 3. A tubular joint (1) according to claim 2, characterized in that the angles α and β are both 0°.

7. A tubular coupling (1) according to any one of the preceding claims, characterised in that the gap (30) has an axial length of between 0.10 mm and 0.82 mm.

8. A tubular joint (1) according to any one of the preceding claims, characterized in that the gap (30) has an axial length such that: BSL x 0.5% / 4 ≤ Gap (30) ≤ BSL x 0.7% Here, BSL is in mm.

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