Threaded Tubular Fittings

Abstract

A tubular coupling (1) including a first tubular part (2) and a second tubular part (3), each tubular part (2, 3) having a thread (8) and a sealing surface (9, 7, 13, 15), the thread (8, 14) having a varying thread width, the threads (8, 14) interlocking in an assembled state of the tubular coupling (1), the sealing surfaces (7, 9, 13, 15) in sealing contact in the assembled state of the tubular coupling (1), the tubular coupling (1) having a reference mark (26) having an optimum relative position between the tubular parts (2, 3), the optimum relative position corresponding to a nominal optimum relative position with a correction applied, the correction being a function of a characteristic of one of the first tubular part (2) and the second tubular part (3) on which the reference mark is provided, and a target torque of the tubular coupling (1).

Description

[Technical Field]

[0001] The present invention relates to the field of threaded joints for tubular components used in applications such as drilling, hydrocarbon well extraction, oil and gas transportation, fluid storage, as well as in the field of geothermal energy or CO2 capture. [Background technology]

[0002] Threaded couplings for tubular components, such as those used in hydrocarbon well production strings, comprise a pair of tubular components sealingly joined together for the purpose of transporting oil, gas, or other fluids. Each of these joined tubular components has a threaded end, which is formed on the inner surface of the tubular component in the case of a female (or "box") threaded end, or on the outer surface of the tubular component in the case of a male (or "pin") threaded end. The threaded ends are complementary to each other, allowing the tubular components to be mated and threadedly joined together.

[0003] The tubular components of a threaded joint are assembled under predetermined stress conditions to meet the tightening and sealing requirements imposed by the conditions of use, and when so assembled, the tubular components form what is called a joint or fitting in the assembled state.

[0004] Furthermore, during use, these threaded joints may be subjected to axial tensile and / or compressive stresses, internal and / or external fluid pressure, bending or torsion, etc., which may act in combination with varying strengths. The tightening ability of these threaded joints must be ensured despite the above stresses and harsh working conditions in the field.

[0005] Threaded joints must also be able to be screwed and unscrewed multiple times without compromising their performance, especially without seizing. After unscrewing, these parts can be reused under different working conditions.

[0006] Patent document US20070158943 describes a threaded joint with a self-locking thread having teeth with varying widths, i.e., interference between the flanks of the thread teeth. The threaded joint described in this document also has a metal-to-metal sealing surface. Such a joint can achieve both high torque and good sealing properties.

[0007] As stated in the document, it is important that the two tubular parts constituting a joint have a controlled relative position to ensure a good working relationship between the sealing surfaces and therefore a good sealing performance of the joint. In particular, it is important that the threading of the two tubular parts is such that there is sufficient interference between the two sealing surfaces to ensure a seal of the joint, while preventing excessive interference that could cause seizure and / or damage to the sealing surfaces.

[0008] To ensure the correct relative positioning of the tubular components that make up the joint, the joint described in Patent Document US20070158943 further includes complementary stop surfaces on the tubular components. These stop surfaces abut to ensure the correct relative positioning of the tubular components that make up the joint. However, these stop surfaces occupy a large radial space, limiting the space available for other elements of the tubular components. Furthermore, these stop surfaces may create stress concentration areas, impairing the proper functioning of the joint. Therefore, these stop surfaces are not always fully satisfactory for ensuring the correct relative positioning of tubular components in joints with threads that have variable widths and dedicated sealing surfaces. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] US20070158943 Summary of the Invention [Problem to be solved by the invention]

[0010] To avoid the use of stop surfaces, it is also known to provide a reference mark, for example a visual reference mark, on one of the tubular components of a fitting. Typically, the tubular component is threaded until a target tightening torque (hereinafter referred to as "target torque") is reached, which corresponds to the torque that will be obtained when the threaded fitting is in an assembled state. If, in the assembled state of the fitting, the end of the tubular component that does not have a visual reference mark coincides with the visual reference mark, the fitting is deemed to have satisfactory operating characteristics and is therefore approved. Conversely, if, in the assembled state of the fitting, the end of the tubular component that does not have a visual reference mark does not coincide with the visual reference mark, the threaded fitting is deemed to have unsatisfactory operating characteristics and is therefore rejected.

[0011] The visual reference mark is placed on one of the tubular components of the fitting based on a nominal position of the reference mark. The nominal position of the reference mark is determined, along with other parameters of the fitting, by dimensions defined in the fitting and tubular component specifications. More specifically, the reference point is defined by a nominal optimum relative position between the tubular components and a nominal axial position tolerance on either side of the nominal optimum relative position.

[0012] However, like other parameters of fittings and tubular components, the nominal position of the reference mark is subject to manufacturing tolerances. Typically, the nominal optimum relative position and nominal axial position tolerance are accompanied by manufacturing tolerances for its location on the tubular component. Additionally, other structural features of the tubular components are subject to manufacturing tolerances, which also introduces uncertainty into the exact relative position of the tubular components with respect to the reference marks when the fitting is in an assembled state.

[0013] Specifically, due to tolerances in thread manufacturing, interference in the target tightening torque, and tolerances in the location of the sealing faces, it is possible that even when the target tightening torque is reached and the end of the tubular component without a reference mark is aligned with the reference mark, the sealing faces may not be positioned correctly to ensure a good seal in the fitting. That is, even when the sealing faces are not correctly aligned with each other, manufacturing tolerances that cause the position of the reference mark to correspond to the end of the tubular component without a reference mark can result in an unsatisfactory assembled fitting being approved. This inaccurate relative alignment of the sealing faces can result in insufficient or excessive interference between the sealing faces, which can lead to poor sealing, seizure, or even damage to the sealing faces.

[0014] Conversely, even if the sealing faces are correctly positioned, the free end of the tubular part that does not have the reference mark may not coincide with the reference mark when the target tightening torque is reached. In other words, manufacturing tolerances may cause the reference mark to not coincide with the end of the tubular part that does not have the reference mark, which may result in a satisfactory assembly being rejected.

[0015] Thus, there is a need for a fitting that reliably provides high torque and good sealing. [Means for solving the problem]

[0016] The idea behind the present invention is to provide a joint that reliably provides high torque and good sealing. In particular, the idea behind the present invention is to precisely and reliably position a reference mark for relative positioning between two tubular parts of the joint. The idea behind the present invention is therefore to precisely and reliably position a reference mark for relative positioning between the tubular parts, taking into account the structural elements of the threaded joint. The idea behind the present invention is also to determine the position of the reference mark using the characteristics of the actual joint and the tubular parts.

[0017] To this end, the present invention provides a tubular joint comprising a first tubular part and a second tubular part, the first tubular component includes a first thread and a first sealing surface, the first thread having a varying face width; the second tubular part includes a second thread and a second sealing surface, the second thread having a varying face width; the first thread and the second thread mesh together in an assembled state of the tubular joint, and the first seal surface and the second seal surface are in sealing contact in the assembled state of the tubular joint; one of the first tubular part and the second tubular part includes a reference mark, the reference mark having an optimum relative position between the first tubular part and the second tubular part; the optimum relative position of the reference mark is a corrected optimum relative position, the corrected optimum relative position corresponds to a nominal optimum relative position with a correction applied, the correction being a function of a characteristic of one of the first tubular part and the second tubular part on which the reference mark is provided and a target torque of the tubular joint.

[0018] A thread having a varying face width is one in which the width of the teeth increases in the axial direction of the tubular part from the free end of the part toward the main body of the part. The face width is the same for successive teeth, excluding incomplete teeth, as measured at the same height, e.g., the level of the crest width of the tooth. The variation in face width is achieved by a difference in thread pitch between the flanks of the tooth, e.g., by making the thread pitch on the stub flank of the tooth greater than the thread pitch on the load flank.

[0019] These features ensure that the reference marks that control the relative positions of the first and second tubular components in the assembled state of the fitting are located with sufficient precision on the corresponding tubular components, and in particular, the positions of these reference marks are determined by the actual characteristics of the tubular components and the tubular fitting, and not by theoretical positions that do not take into account manufacturing tolerances of both the reference marks and other characteristics of the tubular components and the fitting.

[0020] Therefore, the reference marks arranged according to the above characteristics can ensure proper optimal relative positioning of the first tubular part and the second tubular part. In particular, the reference marks arranged according to the above characteristics can ensure satisfactory relative positioning of the first sealing surface and the second sealing surface, and can ensure good sealing of the joint in the assembled state. Furthermore, proper positioning of the reference marks and therefore the sealing surfaces can prevent damage due to excessive interference between the sealing surfaces.

[0021] This corrected, optimal relative positioning also prevents over-insertion of the male tubular component into the female tubular component, which can cause seizing of the tubular fitting. Furthermore, such over-insertion can cause the ends of the male tubular component to rotate radially inward, potentially obstructing the passage of a control tool ("drift").

[0022] Such a reference point with a corrected optimal relative position can also ensure satisfactory screwing of the first tubular part and the second tubular part without following a screw curve. Specifically, it is possible to ensure that the tubular joint is in a good assembled state by simply screwing the tubular part without a reference mark until the distal end of the tubular part reaches the relative position at the reference mark.

[0023] The joints according to the invention are advantageously able to withstand high levels of tension and compression forces in a simple and reliable manner, and such joints do not require the presence of stop surfaces to withstand high levels of tension and compression forces. DETAILED DESCRIPTION OF THE INVENTION

[0024] According to embodiments of the present invention, such a tubular coupling may comprise one or more of the following features, either alone or in combination:

[0025] According to one embodiment, the correction is made based on the outer diameter of one of the first and second tubular parts provided with a reference mark.

[0026] According to one embodiment, the correction is made based on the radial thickness of one of the first and second tubular parts provided with a reference mark.

[0027] According to one embodiment, the correction is based on the thread pitch of one of the first and second tubular parts provided with a reference mark. According to one embodiment, this thread pitch is the thread pitch of the stub flank of the thread belonging to one of the first and second tubular parts including the reference mark. According to one embodiment, this thread pitch is the thread pitch of the load flank of the thread belonging to one of the first and second tubular parts including the reference mark.

[0028] According to one embodiment, the correction is based on a target torque of the tubular joint.

[0029] Preferably, the correction is performed according to the following formula:

number

[0030] According to one embodiment, the first screw has a plurality of first teeth, the width of which along the longitudinal axis of the tubular joint increases in a first direction in the axial direction of the tubular joint.

[0031] According to one embodiment, the second thread has a plurality of second teeth, the width of which along the longitudinal axis of the tubular joint increases in a second direction in the axial direction of the tubular joint, and the first direction is opposite to the second direction.

[0032] Preferably, the first direction is from the distal end of the first tubular part towards the main body of the first tubular part, and the second direction is from the distal end of the second tubular part towards the main body of the second tubular part.

[0033] According to one embodiment, the corrected optimum relative position of the reference marks defines an optimum axial position of the distal end of the other of the first and second tubular parts, in other words, the reference marks define, based on the corrected optimum relative position of one tubular part, where the distal end of the other tubular part should stop in order to obtain a satisfactory tubular joint in the assembled state.

[0034] According to one embodiment, the tubular fitting comprises a lower tolerance zone.

[0035] Such a lower tolerance zone can define a range of relative positions between the tubular components within which a loss of interference between the sealing surfaces is acceptable without significantly impairing the proper functioning of the tubular coupling. For example, a loss of interference between the first and second sealing surfaces of approximately 30% compared to the nominal interference may be considered acceptable in the assembled state of the tubular coupling, i.e., at the target torque. In such a case, a tubular coupling having an interference between the first and second sealing surfaces of at least 70% in the assembled state may be considered acceptable. This acceptable interference loss can be adjusted depending on the circumstances, such as the shape of the first and / or second sealing surfaces, the presence or absence of other seals in the tubular coupling, the expected operating conditions, and other factors.

[0036] According to one embodiment, the lower tolerance zone is determined on the one hand by the corrected optimum relative position of the reference mark and on the other hand by a corrected lower limit value, said lower tolerance zone extending from the corrected optimum relative position in the direction of the distal end of one of the first tubular part (2) and the second tubular part (3) comprising the reference mark by a distance corresponding to said corrected lower limit value.

[0037] This lower limit can be defined in a variety of ways. For example, this lower limit can be defined arbitrarily based on statistics regarding lower limits that are considered acceptable. Preferably, this lower limit is determined as a function of the interference between the first and second sealing surfaces. Ideally, this lower limit is determined based on the interference between the first and second sealing surfaces, on the one hand, and the interference between the first and second threads, on the other hand.

[0038] According to one embodiment, the corrected lower limit is calculated using the following formula:

number

[0039] In the case of a flat sealing surface, the inclination angle ST1 or ST2 of such a flat sealing surface corresponds to the angle formed between the flat sealing surface and the longitudinal axis of the tubular joint, whereas in the case of a toric sealing surface, the inclination angle of the toric sealing surface corresponds to the angle formed by a line connecting the junction of the toric sealing surface and the portions of the tubular component axially located on either side of the toric sealing surface.

[0040] According to one embodiment, the corrected lower limit value is equal to the minimum value of the first lower limit value and the second lower limit value, and the first lower limit value and the second lower limit value are expressed by the following formula:

number

[0041] By taking into account the interference between the sealing surfaces on the one hand and the interference between the threads on the other hand, such a lower limit value can be determined very accurately, and it is precisely guaranteed that when, in the assembled state of the tubular joint, the distal end of the tubular part that does not include the reference mark is radially aligned with the reference mark between the corrected optimum relative position and the lower tolerance zone, the interference between the sealing surfaces is minimized.

[0042] In tubular fittings in which the threads have crests and / or roots that are inclined relative to the longitudinal axis of the fitting, the inclination angle of the threads corresponds to the inclination of the crests and / or roots. In addition, in tubular joints in which the thread teeth have crests and roots parallel to the longitudinal axis of the tubular joint, the inclination angle of the threads corresponds to the inclination angle of a line passing through the same points on the roots or crests of successive teeth, and in defining this inclination angle, teeth with singular points, such as incomplete teeth, for which it is not possible to define a corresponding point on this line, are to be ignored.

[0043] According to one embodiment, the tubular fitting further comprises an upper tolerance zone.

[0044] The upper tolerance limits define the relative position of the tubular components and prevent damage caused by excessive interference between the sealing surfaces. Furthermore, the upper tolerance limits prevent inward deformation of the tubular fitting due to excessive threading of the tubular components, which can prevent the passage of a control tool (so-called "drift").

[0045] According to one embodiment, the upper tolerance zone is determined on the one hand by the corrected optimum relative position of the reference mark and on the other hand by an upper limit value, and the upper tolerance zone extends from the corrected optimum relative position by a distance corresponding to the upper limit value in the direction away from the free end of one of the first tubular part (2) and the second tubular part (3) that is provided with the reference mark.

[0046] This upper limit can be defined in a variety of ways. For example, this upper limit can be defined arbitrarily based on statistics regarding upper limits that are considered acceptable. Preferably, this upper limit is determined as a function of the interference between the first and second sealing surfaces. Ideally, this upper limit is determined based on the interference between the first and second sealing surfaces, on the one hand, and the interference between the first and second threads, on the other hand.

[0047] According to one embodiment, the upper limit is determined by the following formula:

number

[0048] According to one embodiment, the upper limit is equal to the minimum of a first upper limit and a second upper limit, which are expressed by the following formula:

number

[0049] According to one embodiment, the first tubular part has a plurality of first sealing surfaces and the second tubular part has a plurality of second sealing surfaces.

[0050] In the case where multiple sealing surfaces are provided on each of the tubular components, the lower and upper limits are defined for each sealing area of ​​the tubular joint as described above. This sealing area is formed by the interaction of either the first sealing surface or the second sealing surface. The lower tolerance zone is defined by the corrected optimum relative position and the smallest lower limit value among the set of lower limits. Similarly, the upper tolerance zone is defined by the corrected optimum relative position and the smallest upper limit value among the set of upper limits. The invention will be better understood, and other objects, details, features and advantages will become more apparent, from the following description of various specific embodiments thereof, given by way of non-limiting example, with reference to the accompanying drawings, in which: [Brief explanation of the drawings]

[0051] [Figure 1] FIG. 1 is a cross-sectional view of a tubular coupling according to one embodiment of the present invention. [Figure 2] FIG. 2 is a schematic representation of an area of ​​the tubular joint shown in FIG. 1 that includes reference marks for relative positioning of the tubular components. [Figure 3] FIG. 3 shows a schematic representation of a first variant of the tubular coupling shown in FIG. 1, in which the region of the variant includes reference marks for the relative positioning of the tubular parts. [Figure 4] FIG. 4 shows a schematic representation of a second variant of the tubular coupling shown in FIG. 1, in which the region of the variant includes reference marks for the relative positioning of the tubular parts.

[0052] In the following description, as well as in the drawings and claims, axis X corresponds to the axis of rotation of the tubular parts in the assembled state of the tubular coupling, and this axis X is also defined as the axis of the tubular coupling. By convention, "radial" denotes a direction perpendicular to axis X, and "axial" denotes a direction parallel to axis X.

[0053] The terms "outer" and "inner" are used to define the relative positions of elements with respect to axis X. Elements closer to axis X are referred to as inner or radially inner, whereas elements located at the axial periphery are referred to as outer or radially outer.

[0054] The extraction of oil, gas, and other resources requires the joining of many pairs of pipes to form strings within the well. These pipes are subjected to many stresses during installation and operation and therefore have a standardized shape to avoid damage to the surrounding environment and leakage.

[0055] 1 shows a cross-sectional view of a tubular coupling 1 according to one embodiment of the present invention. The tubular coupling 1 is formed by assembling a first tubular part 2 and a second tubular part 3.

[0056] The first tubular part 2 comprises a first main body 4 and a first connecting portion 5. The first connecting portion 5 is formed on the outer surface of the first tubular part 2, and such first tubular part 2 is called a "male" (or "pin") part. The first connecting portion 5 comprises, from the first main body 4 to the first free end 6 of the first tubular part 2, a first outer sealing surface 7, a first thread 8, a first inner sealing surface 9, and the first free end 6, in that order.

[0057] Similarly, the second tubular part 3 comprises a second main body 10 and a second connecting portion 11. The second connecting portion 11 is formed on the inner surface of the second tubular part 3, and such a second tubular part 3 is called a "female" (or "box") part. The second connecting portion 11 comprises, from the second main body 10 towards the second free end 12 of the second tubular part 3, a second inner sealing surface 13, a second thread 14, a second outer sealing surface 15, and the second free end 12, in that order.

[0058] 1, the first screw 8 has a plurality of first teeth 16. Each of the first teeth 16 has a shape in which the tooth width, when viewed at the same radial height in a direction parallel to the axis X, varies along the direction of the axis X. More specifically, the tooth width of each of the first teeth 16 increases along a first direction from the first free end 6 toward the first main body 4.

[0059] Each first tooth 16 has a first bottom 17, a first stub side 18, a first top 19, and a first load side 20. The first stub side 18 faces the first free end 6, and the first load side 20 faces the first main body 4.

[0060] Similarly, the second thread 14 has a plurality of second teeth 21 with varying face widths, the second teeth 21 increasing in width along a second direction from the second free end 12 toward the second main body 10. The first and second directions are opposite to each other relative to the axis X. Similarly, the second teeth 21 have a second bottom 22, a second stub side 23 (toward the second free end 12), a second top 24, and a second load side 25 (toward the second main body 10).

[0061] FIG. 1 shows the tubular coupling 1 in an assembled state. This assembled state is obtained by threading a first tubular part 2 and a second tubular part 3 together. During this threading, the first teeth 16 mesh with the second teeth 21. More specifically, in the assembled state, the first teeth 16 and the second teeth 21 mesh with interference. Therefore, in the assembled state, the first stub side surface 18 interferes with the second stub side surface 23, and the first load side surface 20 interferes with the second load side surface 25.

[0062] Similarly, in the assembled state, the first inner seal surface 9 and the second inner seal surface 13 are in interference contact with each other to ensure the sealing performance of the tubular joint 1, particularly the sealing performance against the fluid flowing inside the tubular joint 1. The first outer seal surface 7 and the second outer seal surface 15 are also in interference contact with each other to ensure the sealing performance against the fluid flowing outside the tubular joint 1.

[0063] To ensure the correct relative positioning of the first tubular part 2 and the second tubular part 3 in the assembled state, and in particular the correct relative positioning of the sealing surfaces 7, 9, 13 and 15, reference marks 26 are provided on the first tubular part 2. More specifically, as shown in Figure 2, the reference marks 26 are provided on the outer surface of the first main body 4.

[0064] The reference mark 26 comprises a nominal optimum relative position, i.e. a theoretical position (hereinafter referred to as the nominal position) defined in the manufacturing specifications of the first tubular part 2. This nominal position defines the relative position between the first tubular part 2 and the second tubular part 3, in particular between the second free end 12 and the first tubular part 2, in which the various elements of the first tubular part 2 and the second tubular part 3, in particular the sealing surfaces 7, 9, 13 and 15, are arranged for optimal functioning of the tubular fitting 1.

[0065] Furthermore, the reference mark 26 includes a nominal lower limit and a nominal upper limit, which define an allowable range of relative positions of the tubular components 2 and 3, defined on either side of the nominal position. If, in the assembled state of the fitting, the second free end 12 is radially aligned within these ranges of relative positions, it is theoretically guaranteed that the tubular fitting 1 will function at an allowable level, although not entirely optimal. For example, these nominal lower and upper limits may define the allowable interference loss of the sealing surfaces 7, 9, 13, and 15, or conversely, the maximum allowable interference for the optimum interference.

[0066] However, the reliability of this reference mark 26 is dependent on the manufacturing tolerances of the first tubular part 2 and the second tubular part 3. In particular, the manufacturing tolerances of the threads 8 and 14 affect the degree of interference between the side surfaces 18, 20, 23, and 25, and therefore the relative positions of the first tubular part 2 and the second tubular part 3, thereby affecting the reference mark 26. The nominal position, nominal upper limit, and nominal lower limit defining the reference mark 26 are themselves subject to manufacturing tolerances. Furthermore, the sealing surfaces 7, 9, 13, and 15 are also subject to manufacturing tolerances. Therefore, there is uncertainty regarding the reliability of the reference mark 26 in indicating the proper relative positions of the sealing surfaces 7, 9, 13, and 15.

[0067] Manufacturing tolerances may affect reference mark 26 such that tubular fitting 1 is approved even though sealing surfaces 7, 9, 13, and 15 would not otherwise operate acceptably, because second free end 12 is positioned radially in line with reference mark 26. Conversely, manufacturing tolerances may affect reference mark 26 such that tubular fitting 1 is rejected even though sealing surfaces 7, 9, 13, and 15 would otherwise operate acceptably.

[0068] To avoid this, the reference marks 26 according to the present invention are positioned based on the actual parameters of the first tubular part 2 and the second tubular part 3. Typically, the reference marks 26 are positioned on the first tubular part 2 according to these parameters after manufacture of the first tubular part 2 and the second tubular part 3. These parameters are measured, calculated, or obtained by other means. Therefore, the parameters related to either tubular part 2 or 3 used in the following equations are the actual parameters of that tubular part 2 or 3, e.g., parameters measured after manufacture. On the other hand, the parameters related to the tubular fitting 1, such as the target torque CC, the percentage of interference in the seal SI, or the interference Ti between the first thread 8 and the second thread 14, are nominal, i.e., theoretical, values ​​for the tubular fitting 1. These nominal values ​​are values ​​at the target torque when interference is present.

[0069] In particular, a corrected optimum relative position 27 is defined. The reference mark 26 is provided on the first tubular part based on this corrected optimum relative position 27 (hereinafter referred to as the corrected position 27), rather than based on the nominal position. This corrected position 27 is defined not only as a function of the nominal position as defined in the specification, but also as a function of the outer diameter OD of the first tubular part 2, the thickness Wt of the first tubular part 2, and the thread pitch PdF of the first thread 8. The outer diameter OD, the thickness Wt, and the thread pitch PdF are measured, calculated, or obtained by other means after manufacture of the first tubular part 2, and are therefore actual parameters of the first tubular part.

[0070] The corrected position 27 is also positioned as a function of the target torque CC of the tubular joint 1 .

[0071] In this way, a positioning correction for the optimum relative position is calculated for the reference mark, which correction is given by the following formula:

number

[0072] The tolerance threshold ST can be determined in various ways. Preferably, this tolerance threshold ST can be determined arbitrarily, for example to a value of 96,000, which is adapted to all joints according to the invention. The tolerance threshold ST can also be calculated by analyzing the inclination angle and thread pitch of the threads, in particular the "wedge ratio", i.e. the difference between the thread pitch of the stub flank and the thread pitch of the load flank.

[0073] From this formula, the shift distance from the nominal position can be obtained, and therefore, by applying the resulting correction value to the nominal position, the corrected position 27 is obtained, i.e. the position where the reference mark 26 on the first tubular part 2 is located.

[0074] This correction allows for an accurate and reliable placement of the reference mark 26. In particular, the corrected position 27 takes into account the manufacturing tolerances of the first tubular part 2 and the tubular fitting 1, and corresponds to a relative position of the second free end 12 with respect to the reference mark 26 such that the sealing surfaces 7, 9, 13, and 15 are indeed properly positioned to ensure the sealing of the tubular fitting 1.

[0075] Additionally, the reference mark 26 located based on the corrected position 27 includes a corrected lower limit value 28 and a corrected upper limit value 29, which can be determined in a variety of ways.

[0076] For example, the corrected lower limit 28 and / or the corrected upper limit 29 may be determined by the nominal lower limit and / or the nominal upper limit, respectively, in which case the reference mark 26 includes the upper and lower tolerance zones determined by the corrected position 27 and these nominal limits.

[0077] Alternatively, the corrected lower limit value 28 and / or the corrected upper limit value 29 may be determined based on statistics of the tolerance limits.

[0078] Preferably, as well as the corrected position 27, the corrected lower limit value 28 and / or the corrected upper limit value 29 are also determined based on the actual structural parameters of the tubular joint 1 in order to further improve the reliability and accuracy of the reference mark 26.

[0079] In this manner, the corrected lower limit value 28 is advantageously determined as a function of the desired minimum interference between the sealing faces 7, 9, 13, and 15. Similarly, the corrected upper limit value 29 is advantageously corrected as a function of the desired interference between the sealing faces 7, 9, 13, and 15.

[0080] Ideally, the lower limit is determined not only as a function of the desired minimum interference between sealing faces 7, 9, 13, and 15, but also as a function of the interference between threads 8 and 14. Similarly, the corrected upper limit 29 is ideally determined not only as a function of the desired minimum interference between sealing faces 7, 9, 13, and 15, but also as a function of the interference between threads 8 and 14.

[0081] In a joint having multiple seals, such as that shown in Figure 1, a corrected lower limit is determined for each seal, resulting in multiple corrected lower limit values. The corrected lower limit value used to define reference point 26 is the smallest corrected lower limit value of the multiple corrected lower limit values. Similarly, a corrected upper limit is calculated for each seal, and the corrected upper limit value used to define reference point 26 is the smallest corrected upper limit value of the multiple corrected upper limit values ​​obtained as a function of the multiple seals.

[0082] Therefore, in the case of a tubular joint such as that shown in FIG. 1 , which has an inner seal integrally formed by a first inner seal surface 9 and a second inner seal surface 13, and an outer seal integrally formed by a first outer seal surface 7 and a second outer seal surface 15, a corrected limit value is determined for the inner seal, and a corrected limit value is also determined for the outer seal. The corrected lower limit value 28 of the reference mark 26 is the smallest corrected lower limit value determined for the inner seal and the outer seal. Similarly, the corrected upper limit value 29 of the reference mark 26 is the smallest corrected upper limit value determined for the inner seal and the outer seal.

[0083] Below, the locations of the corrected lower limit and the corrected upper limit are generally described for the seal area, but the following description is applicable to each of the different seals.

[0084] According to one embodiment that takes into account the actual interference between the seal faces, the corrected lower limit 28 is calculated using the following formula:

number

[0085] Such a corrected lower limit 28 takes into account the effect that the desired and actual interference between the sealing surfaces has on approving or rejecting the tubular fitting 1 .

[0086] In the case of a flat sealing surface, the inclination angle of the flat sealing surface corresponds to the angle formed between the flat sealing surface and the axis X of the tubular joint 1 .

[0087] In the case of a toric sealing surface, the inclination angle of the toric sealing surface corresponds to the angle formed by a line connecting the points where the toric sealing surface joins with the respective axially located tubular component portions.

[0088] The allowable interference loss between the sealing surfaces may be determined based on the shape of the sealing surfaces, the performance required of the tubular coupling 1, or other reasons. If the interference loss between the sealing surfaces is, for example, 30%, this means that the corrected lower limit value ensures at least 70% interference.

[0089] Similarly, the upper limit is determined by the following formula:

number

[0090] The maximum allowable interference between the sealing surfaces may be determined based on the shape of the sealing surfaces, the performance required of the tubular joint 1, or other reasons. The maximum allowable interference between the sealing surfaces is, for example, 40%.

[0091] Such a corrected upper limit takes into account the effect that the desired and actual interference between the sealing surfaces has on approving or rejecting the tubular coupling 1 .

[0092] According to a preferred embodiment that takes into account not only the actual interference between the sealing surfaces but also the interference between the threads, the corrected lower limit value is equal to the minimum value of the first corrected lower limit value and the second corrected lower limit value, and the first corrected lower limit value and the second corrected lower limit value are expressed by the following formula:

number

[0093] Such a corrected lower limit value, which takes into account the interference between the sealing surfaces on the one hand and the interference between the threads on the other hand, makes it possible to determine a very accurate corrected lower limit value, which accurately guarantees that a minimum interference is ensured in the assembled state of the tubular coupling 1.

[0094] Similarly, the corrected upper limit value is equal to the minimum value of the first corrected upper limit value and the second corrected upper limit value, and the first corrected upper limit value and the second corrected upper limit value are expressed by the following formula:

number

[0095] In this preferred embodiment, the effects of both the desired and actual interference between the sealing surfaces and the actual interference between the threads are considered to reliably and accurately approve or reject a tubular fitting.

[0096] 1 and 2 show a tubular fitting 1 in which a reference mark 26 is provided on the outer surface of the main body 4 of the first male tubular part 2, and the tubular fitting can be identified depending on the relative position of the second free end 12 to the reference mark 26. However, the invention applies equally to tubular fittings having other configurations.

[0097] Figures 3 and 4 show other configurations, and the above description of the reference mark 26, the corrected position 27, the corrected lower limit 28, and the corrected upper limit 29 applies equally to such other configurations of the tubular coupling 1. In Figures 3 and 4, elements that are the same as or perform the same functions as elements described above with reference to Figures 1 and 2 are given the same reference numerals. In the description of Figures 3 and 4, only elements that differ from the description with reference to Figures 1 and 2 will be described in detail, and elements not described with reference to Figures 3 and 4 are the same as elements already described with reference to Figures 1 and 2.

[0098] 3 shows an example of a tubular fitting 1 that is referred to as "flush," meaning that the outer diameter of the tubular fitting 1 is less than 101% of the outer diameter of the tubular parts 2 and 3 that make it up. In this tubular fitting 1, a reference mark 26 is provided on the outer surface of the first connecting portion 5 of the first tubular part 1. More specifically, the reference mark 26 is provided between the first main body 4 and the first outer sealing surface (not shown).

[0099] 4 shows an example of a tubular connection 1 in which a reference mark 26 is located on the inner surface of the second tubular part 3, i.e., the female tubular part 3. This reference mark 26 allows the tubular connection 1 to be approved or rejected based on the relative position of the reference mark 26 and the first free end 6. Furthermore, the reference mark 26 is located axially on the inner surface of the second connection part 11, between the second main body 10 and the second inner sealing surface 13.

[0100] 1 to 4, only elements relevant to the present invention are described, and the tubular coupling may include other features not described above. For example, the tubular coupling shown in Fig. 1 may include an external groove for collecting grease that may be applied to the tubular parts, and the first tubular part may include a chamfer connecting the surface of the free end of the first tubular part to the inner surface of the first tubular part, etc.

[0101] Although the present invention has been described in the context of the preferred embodiment described with reference to Figures 1 to 4, the invention extends to embodiments not shown.

[0102] For example, the present invention is applicable to integrally coupled or sleeve-coupled joints. In an integrally coupled joint, long tubular components have a male connecting element at a first end and a female connecting element at a second end, and the long tubular components are directly mated and assembled. In a sleeve-coupled joint, a long tubular component has male connecting elements at both ends, and a shorter tubular component, called a coupler, has female connecting elements at both ends, and the two long tubular components are connected by the coupler.

[0103] The joints may be flush or semi-flush. A flush connection is one in which the outer diameter is 101% or less of the outer diameter of the tubular component body. A semi-flush connection is one in which the outer diameter is 110% or less of the outer diameter of the tubular component body.

[0104] Similarly, although the present invention is described in the context of a single thread, it is also applicable to threads having multiple thread regions, for example, multiple-tiered thread regions.

[0105] Additionally, the present invention is applicable to tubular fittings having one or more sealing areas, such as sealing areas on both sides of the threads or a central sealing area.

[0106] The bottom and top of the thread teeth may be parallel to the axis of the tubular fitting or parallel to the inclination of the threads. The teeth may have a dovetail or trapezoidal shape.

[0107] Reference marks can be created in a variety of ways, for example, such reference marks can be created by knurling, machining grooves that form visual reference marks, laser marking, painting, stamping reference marks, etc.

[0108] In the case of a tubular joint in which a plurality of first sealing surfaces and a corresponding plurality of second sealing surfaces are paired to form a plurality of sealing areas, the corrected lower limit value and the corrected upper limit value are respectively the minimum of the lower limit value and the minimum of the upper limit value determined for all sealing areas.

[0109] Although the present invention has been described with reference to some particular embodiments, it is not limited thereto, but includes all technical equivalents of the means described and combinations thereof.

[0110] Use of the verb "comprise" or "comprise" and their conjugations does not exclude the presence of elements or steps other than those listed in a claim.

[0111] In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim.

Claims

1. A tubular coupling (1) comprising a first tubular part (2) and a second tubular part (3), the first tubular part (2) comprises a first thread (8) and a first sealing surface (9, 7), the first thread (8) having a varying face width; the second tubular part (3) comprises a second thread (14) and a second sealing surface (13, 15), the second thread (14) having a varying face width; the first thread (8) and the second thread (14) are in mesh with each other in an assembled state of the tubular joint (1), and the first sealing surfaces (7, 9) and the second sealing surfaces (13, 15) are in sealing contact with each other in the assembled state of the tubular joint (1); one of the first tubular part (2) and the second tubular part (3) is provided with a reference mark (26), the reference mark having an optimum relative position between the first tubular part (2) and the second tubular part (3); the optimum relative position of the reference mark (26) is a corrected optimum relative position (27), the corrected optimum relative position (27) corresponds to a nominal optimum relative position to which a correction has been applied, the correction being a function of a characteristic of one of the first tubular part (2) and the second tubular part (3) on which the reference mark is provided and a target torque of the tubular joint (1).

2. The correction is calculated using the following formula: [Equation 1] 2. The tubular joint (1) according to claim 1, wherein ST is a tolerance threshold, OD is the outer diameter of one of the first tubular part (2) and the second tubular part (3) comprising the reference mark (26), Wt is the thickness of one of the first tubular part (2) and the second tubular part (3) comprising the reference mark (26), CC is the target torque of the tubular joint (1), and PdF is the thread pitch of the thread belonging to one of the first tubular part (2) and the second tubular part (3) comprising the reference mark (26).

3. A tubular coupling (1) according to claim 1 or 2, further comprising a lower tolerance zone.

4. the lower tolerance zone is determined on the one hand by the corrected optimum relative position (27) of the reference mark (26) and on the other hand by a corrected lower limit value (28); 4. A tubular joint (1) according to claim 3, wherein the lower tolerance zone extends from the corrected optimum relative position (27) in the direction of the free end (6, 12) of one of the first tubular part (2) and the second tubular part (3) that has the reference mark (26) by a distance corresponding to the corrected lower limit value (28).

5. The corrected lower limit (28) is expressed by the following formula: [Equation 2] 5. A tubular coupling (1) according to claim 4, wherein SI is the percentage of interference in the seal, R1 is the allowable interference loss, ST1 is the inclination angle of the first sealing surface (7, 9), and ST2 is the inclination angle of the second sealing surface (13, 15).

6. The corrected lower limit value is equal to the minimum value of the first lower limit value and the second lower limit value, and the first lower limit value and the second lower limit value satisfy the following formula: [Equation 3] 6. A tubular coupling (1) according to claim 5, which satisfies the following formula: [where SI is the percentage of interference in the seal, R1 is the allowable tolerance loss, ST1 is the inclination angle of the first sealing face, ST2 is the inclination angle of the second sealing face, TT_deg is the inclination angle of one of the first thread (8) and the second thread (14) on the tubular part comprising the reference mark (26), and Ti is the nominal interference between the first thread and the second thread].

7. A tubular coupling (1) according to any one of claims 1 to 6, further comprising an upper tolerance zone.

8. the upper tolerance zone is determined on the one hand by the corrected optimum relative position (27) of the reference mark (26) and on the other hand by a corrected upper limit value (29); 8. A tubular joint (1) according to claim 7, wherein the upper tolerance zone extends from the corrected optimum relative position (27) in a direction away from a free end (6, 12) of one of the first tubular part (2) and the second tubular part (3) that includes the reference mark (26) by a distance corresponding to the corrected upper limit value (29).

9. The upper limit is determined by the following formula: [Equation 4] 9. A tubular coupling (1) according to claim 8, wherein SI is the percentage of interference in the seal, R2 is the allowable tolerance loss, ST1 is the inclination angle of the first sealing surface (7, 9), and ST2 is the inclination angle of the second sealing surface (13, 15).

10. The corrected upper limit value (29) is equal to the minimum value of the first upper limit value and the second upper limit value, and the first upper limit value and the second upper limit value are expressed by the following formula: [Equation 5] 10. A tubular coupling (1) according to claim 9, which satisfies the formula: [where SI is the percentage of interference in the seal, R2 is the allowable tolerance loss, ST1 is the inclination angle of the first sealing surface (7, 9), ST2 is the inclination angle of the second sealing surface (13, 15), TT_deg is the inclination angle of one of the first thread (8) and the second thread (14) provided on the tubular part comprising the reference mark (26), and Ti is the nominal interference between the first thread and the second thread].

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