MXPA99010634A - Stress reduction groove for tubular connection - Google Patents

Abstract

A stress reduction groove for tubular connections which relates to a threaded pipe connection, and includes a box member, a pin member, and a continuous groove formed in the thread of one of the members. The box member has a tapered, internal, generally dovetail-shaped thread with stab flanks, load flanks, roots, and crests. The internal thread has a beginning and an end and increases in width in one direction. The pin member also has a tapered, external, generally dovetail-shaped thread with stab flanks, load flanks, roots, and crests. The external thread increases in width in the other direction so that the complementary flanks of the respective threads move into engagement during rotational make-up of the connection and form sealing surfaces that resist the flow of fluids between the threads upon rotational make-up of the connection. A section of one of the internal and external threads has the continuous groove formed in the roots thereof. The groove extends from either the beginning or the end of the one thread to a point between the beginning and end of the one thread, thereby reducing the pressure that develops between the sealing surfaces during rotational make-up in a thread lubricant applied to the threads.

Description

TENSION REDUCTION SLOT FOR CONNECTION TUBULAR This application claims the benefit of the filing of the Provisional Patent Application of E.U.A., No. 60 / 047,159, filed on May 20, 1997.

Field of the Invention The present invention involves threaded tubular seals, which can be used in the drilling and production of oil and gas wells, such as in pipes, liners, linear tubes and drill pipes, commonly known, collectively, as tubular products of oil fields. More particularly, the invention relates to a tubular joint for connecting male members (bolts) and female members (boxes).

BACKGROUND OF THE INVENTION The use of threaded tubular connections to join flow conduits in an end-to-end relationship and thus form a continuous flow path to transport the fluid under pressure is well known. Oilfield tubular products all use threaded connections to connect adjacent sections of conduits or pipes. Examples of such threaded end connections, designed for use in petroleum field tubular products are described in U.S. Patent Nos. 2,239,942, 2,992,019, 3,359,013, RE 30,647, and RE 34,467, all of which were assigned to the successor in the present invention. In US Pat. No. RE 30,647 to Blose, a particular thread form is disclosed for a tubular connection, which supplies a strong splice, while controlling stress and stress on the connected bolt and box members within acceptable levels. The bolt member is equipped with at least one external thread, generally in the form of an assembly, whose width increases in one direction along the bolt, while the box member is equipped with at least one corresponding internal thread, generally in the form of an assembly, whose width increases in the other direction. In this manner, the coincident set of helical threads provides a wedge-type coupling of the opposite flanks of bolt and box, which limit the extent of relative rotation between the bolt and box members and define a compensating condition that can be forced complete the connection. In this thread structure, the flank support angles as well as the thread width can be used to control the stress and stress preload conditions induced in the bolt and box members for a given construction torsion. Thus, the adjustment of the thread structure to a particular application or use, the connection or tubular joint is limited by the properties of the selected materials. During the construction of a threaded connection, according to the teachings of the Blose redirecting patent, it has been observed that thread lubricants, both liquid and paste, may become temporarily trapped in the helical or hollow glaze, formed between the roots and ridges of the respective threads of the bolt member and box. The trapped lubricant (also known as the lubricating component of the threads) can, under certain circumstances, produce a torque reading between the relatively sliding bolt and box threads, indicative of the twist in the construction condition, thus providing a false indication that the joint __ has been completely formed. Next, the thread lubricant, temporarily trapped, can escape through the helical gap, between the roots and ridges, reducing the stress and stress of the preload, to such an extent that the level of anticipated performance or strength of the joint is not they can be achieved. U.S. Patent No. RE 34,467 to Reeves discloses an improvement to the thread structure described in the Blose reissue patent. Specifically, the potential for false joint torque readings, which result from the thread lubricant trapped in the gap between the roots and crests of the threads is resolved. The confidence of the torsion readings developed by the forced construction of the connection is necessary to ensure that the stress preload and deformation conditions of the design actually exist in the connection. The Reeves redirection patent reveals a thread structure in which the box and bolt threads are tapered, in addition to having thread widths that increase in the opposite directions, so the roots, ridges and flanks of the threads move in coupling as the joint is compensated The threads are designed particularly so that roots and complementary ridges move in coupling before the flanks of both the forces and the opposing loads move in engagement, whereby the volume of the lubricant in the gap between the roots and ridges is substantially reduced. In this way, most of the thread lubricant is displaced to the helical clearance between the opposing load flanks and forms a long, very thin ribbon, which has little effect, if any, on the proper construction for connection or ability that the surfaces of the thread form seals, as they move together. Due to the imperfections in the machined thread surfaces that form the seal, such as those described in Reeves' redirecting patent, the thread lubricant can become insulated between the sealing surfaces within the tubular connection. Once the rotation between the bolt and thread members has advanced until the thread lubricant completely fills the insulated volume between the bolt and box members, the additional rotation will produce an increase in the lubricant pressure. This increased pressure can result in higher, tangential (loop) and radial stresses in the connection, particularly in severe cold environments, such as in the North Sea, which will cause the lubricant to harden and become more viscous.

SUMMARY OF THE INVENTION Advantages of the invention may include one or more of the following: a thread lubricant relief path is provided, which can be formed into tubular products from existing oil fields, without the need to trim the threads . A threaded pipe connection is provided, which has a box member and a bolt member. The box member has an internal, tapered thread, generally in the form of an assembly, with stress flanks, load flanks, roots and ridges. The internal threads have a beginning and an end and increase in width in one direction. Likewise, the bolt member has tapered, external, generally in the form of an assembly, with flanks of stress, load flanks, roots and ridges. The external threads increase in width in the other direction, so that the complementary flanks of the respective threads move in engagement during the rotational construction of the connection and form sealing surfaces that resist the flow of fluids between the threads. A continuous groove is formed in the roots of the section of one of the internal or external threads. The groove extends from either the beginning or the end of a thread to a point between the beginning and the end of that thread, thus reducing the pressure that develops between the sealing surfaces during rotational construction in a thread lubricant, applied to the same. A continuous groove can be formed in the roots of a section of each internal and external thread. The slot extends from either the beginning or the end of each thread to a point between the start and the end of another thread, thus reducing the pressure that develops between the sealing surfaces, during the rotational construction in a thread lubricant applied to the same.

The present invention provides a remedy to prevent undue accumulation of lubricant pressure in the thread between the bolt and box members by providing a path through which the lubricant can be discharged. In some embodiments, the present invention provides such discharge resources along a portion of the length of the thread, whereby the remaining length of the thread can be used to create a pressure seal. A lubricant relief path of the thread is provided, which does not change its configuration or size with the wear of the tubular connection.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a side view, partially in section, of an external thread structure of the bolt member of the prior art; Figure 2 is a side view, partially in section, of a tubular gasket of the prior art; Figure 3 is an enlarged cross-section of a prior art tubular joint at the coupling point, between a crest of the bolt member and a root of the box member, - Figure 4 is an enlarged cross-section of a member bolt, according to one embodiment of the present invention; and Figure 5 is an enlarged cross-section of a tubular seal, according to an embodiment of the present invention. -77 Description of the Preferred Modes With reference to the drawings, in which similar reference characters are used for similar parts throughout the various views, Figures 1, 2 and 3 illustrate a wedge-type thread connection, or tube, which usually carries the reference number 10, according to the Reeves Reissue patent. As shown in Figure 2, the connection 10 includes a bolt member 11 and a box member 12. The box member 12 has a threaded, tapered, internal structure 14, generally in the form of an assembly, formed and adapted for coupling with an external, complementary, tapered thread structure 15, generally in the form of an assembly, formed in the bolt member 11, to mechanically secure the box and bolt members in a reasonable manner. The internal thread 14 of the box member 12 is formed with stress flanks 18, load flanks 16, roots 20 and ridges 24, and increases in width progressively at a uniform rate in one direction, substantially over the entire helical length of the thread 14. The external thread 15 of the bolt member 11 is formed with stress flanks 19, load flanks 17, roots 21 and ridges 25, and increases in width progressively at a uniform rate in the other direction, substantially over the entire helical length of thread 15. Thread widths, which grow opposite, and taper of threads 14 and 15, cause flanks, roots and complementary crests of the respective threads to move in forced coupling during the construction of rotation of the connection and form sealing surfaces that resist the flow of fluids between the threads.

The bolt member 11 or the box member 12 defines the longitudinal axis 13 of the construction connection 10. The roots and ridges of the box and bolt members are flat and parallel to the longitudinal axis of the connection and have a sufficient width to prevent any permanent deformation of the threads when the connection is made. As used herein, and as will conventionally be understood, when the tubular joints are connected in a vertical position, such as when the pipeline is formed to descend into the hole of the well, the term "load flank" designates the surface of side wall of a thread facing away from the other end of the respective bolt or box member, on which the thread is formed. The term "stress flank" designates the lateral wall surface of the thread facing the other end of the respective bolt or box member, and supports the weight of the upper tubular member during the initial formation of the joint. An angle alpha is formed between the wall 18 of the stress flank and the root wall 20 of the thread structure 14. The angle alpha is also formed between the wall 19 of the stress flank and the load wall 21 of the structure thread 15. The flank wall 16 and the root wall 20 of the thread 14, like the flank wall 17 and the root wall 21 of the thread 15, form a second beta angle., The alpha and beta angles they are preferably acute angles, for supplying threads in the form of an assembly. However, it should be understood that the semi-assembled shape thread can be provided by defining one of the angles, alpha or beta, of ninety (90) degrees, thus making an appropriate flank wall perpendicular or normal to the longitudinal axis 13 of the connection 10. The roots 21 and ridges 25 in the bolt member 11 are dimensioned to eliminate the radial clearance with the complementary ridges 24 and the roots 20 of the box member 12, during the formation of the connection 10. In other words, the The thread roots and threaded crests 25 of the bolt member 11 enter an interference contact with the corresponding thread surfaces of the box member 12, in the manual tightening of the joint. Removal of the radial clearance between the respective roots and ridges of the threads 14 and 15 substantially reduces the likelihood of creating chambers between the roots and ridges during formation. These chambers can temporarily trap the thread lubricant or contaminate it and produce false torsion readings, which indicate that the joint has formed, meaning that the flanks are in engagement, just as there is root / ridge coupling. However, in practice, it has been found that imperfections in the machining of the threads 14 and 15 can produce regions in which the thread lubricant becomes insulated between the sealing surfaces in the connection. For example, a preferred embodiment described in the Reeves redirection patent considers the engagement of the stress flanks as the bolt is inserted into the box, followed by the engagement of the corresponding roots and ridges in the hand-tightened position, achieved by the rotation of the bolt 11 relative to the box 12. The lubricant component of the pipe thread can become insulated between the coupling regions at the root / peak interface in the manual tightened position, and thus can not flow into the clear that ~ exists between the load flanks at that moment. The continuous rotation of the bolt 11 relative to the case 12, reduces the volume of the lubricant in the trapped regions, due to the plastic deformation of the thread surfaces, and causes an increase in the lubricant pressure of the thread. The increased pressure in the isolated regions results in a tension and stress preload greater than that attempted for the optimal preload conditions in the connection 10. One embodiment of the present invention is shown in Figures 4 and 5., according to the wedge thread described in Reeves' reissue patent. Reference characters similar to those used in Figures 1-3, increased by 100 in magnitude, are used in Figures 4 and 5 to simplify and shorten the written description. An important feature of the present invention is exemplified by the slot 130, which provides a path through which the thread lubricant can be discharged or prevent the buildup of excessive pressure in regions where the lubricant has become trapped between the external thread 114 and the bolt 111 and the internal thread 115 and the box 112. Forming the connection is enhanced, the excess lubricant of the thread is compressed in the slot and ejected from the connection, enabling the construction of the preload condition of tension and appropriate stress in the tubular connection. The slot 130 may be a round bottom groove, formed in the roots of the thread 114 of the bolt member, as shown in Figure 5, and may be of a depth between 0.381 and 0.508 mm. The slot 130 can also be formed at the intersection of the root and load flank, as seen in Figure 4, or similarly formed in any of these ways on the thread 115 of the box member with similar results. The use of a round bottom groove, machined at the root 121 of the bolt member 111, minimizes the stress concentration in the groove, which in turn reduces the peak stress in the groove and maximizes the strength of fatigue of the connection 110. The locations and configurations of the slot 130 in Figures 4 and 5 are shown for illustrative purposes only; those skilled in the art will recognize that slot 130 can take any configuration and be arranged in any location, as may be appropriate for a particular application, without departing from the spirit and scope of this invention. The slot 130 is machined in a section of the external thread 114 in a continuous manner, but, in some embodiments, it is formed only over a limited portion (not shown) of the thread. Thus, the groove is only of a length extending from either the beginning or the end of the thread to a point between the start and the end of the thread, providing a limited path to discharge excessive lubricant pressure from the thread that It develops between the sealing surfaces during the construction of rotation. Because the pressure reduction path can be employed over a limited portion of the thread, the remaining portion of the thread length can be used to form an internal or external pressure seal, for example in the manner described by the manufacturer. Threaded tubular connection of the Reeves redirection patent. Those skilled in the art will appreciate that the present invention is equally applicable to threaded connections in which there is a slight gap between complementary roots and ridges, as described in the Blose redirecting patent. In such thread structures, for example, those with 0.0762 mm gaps (0.1524 mm in total for both connection sides), up to 0.1524 mm (0.3048 mm in total) the thread lubricant can by itself form a seal under high pressure, which resists the flow of fluids through the connection. When tubular joints are exposed to severe cold environments, such as in the North Sea and Canada, during the winter months, the thread lubricant becomes somewhat incompressible and very difficult to move from the gaps between the members bolt and box. When the lubricant is unable to flow freely, it is subjected to increased pressure by the construction of joint rotation. The use of the pressure reduction slot 130 provides a path for exhausting the highly pressurized lubricant, ensuring that the stresses and stresses resulting from the forced construction of the connection do not substantially exceed the designed preload condition.

In this aspiration, it is well known that wear develops on the screw surfaces 114 and 155, when the connection is formed and disassembled several times, and such action will gradually allow the additional travel of the bolt member 111 in the member 112 of box and finally will eliminate any radial clear between the roots and corresponding crests. However, such wear will have no detrimental effects on the operation of the slot 130, since the relief path will not substantially change in shape or size with the typical wear in the threaded joint. Also, the fact that the relief path is machined into the threads independently of the threads themselves, makes the present invention very suitable for application to existing tubular products of oil fields with minimum cutting requirements. From the foregoing, it will be seen that this invention is well adapted to obtain all the aforementioned objectives, together with other advantages that are obvious and that are inherent to the described apparatus and structure. It will be understood that certain characteristics and subcombinations are useful and can be used without reference to other characteristics and subcombinations. This is considered by and within the scope of the claims. Because many possible modalities of the invention can be made, without departing from its scope, it will be understood that all of the material herein indicated or shown in the accompanying drawings will be construed as illustrative and not in a limiting sense. For example, although described with respect to a single thread assembly, the present invention can be applied similarly to a tubular connection having more than one thread assembly, such as a two stage thread seal connection. While the present invention has been described with respect to a limited number of preferred embodiments, those skilled in the art will appreciate numerous modifications and variations thereof. The appended claims seek to cover all modifications and variations that are apparent to an ordinary expert in the field.

Claims (22)

1. CLAIMS 1. A threaded pipe connection, which comprises: a box member, which has a taper, internal thread, generally in the configuration of an assembly, with stress flanks, load flanks, roots and ridges, this internal thread has a start and end that increase in width in one direction; a bolt member, having a tapered, external thread, generally of an assembled configuration, with stress flanks, load flanks, roots and ridges, this external thread increases in width in the other direction, so the complementary flanks of the respective threads move in engagement, during the construction of rotation of the connection and form sealing surfaces that resist the flow of fluids between the threads in the construction of rotation of the connection; A section of one of the threads, internal and external, has a continuous groove, formed at its roots, which extends from the beginning and end of a thread to a point between the start and end of a thread, to reduce the pressure that develops between the sealing surfaces, during the construction of rotation in a thread lubricant, applied to them.
2. 2. The connection of claim 1, wherein the internal and external threads are tapered, so that the complementary roots and ridges move in engagement during the construction of rotation of the connection and form sealing surfaces that resist the flow of fluids between them. threads
3. 3. The connection of claim 1, wherein the groove is a round bottom groove formed in the roots of a thread.
4. 4. The connection of claim 3, wherein the groove is formed at an intersection of the root and the load flank of a thread.
5. 5. The connection of claim 1, wherein the continuous groove is formed in the roots of the bolt member.
6. 6. The connection of claim 1, wherein the continuous groove is formed in the roots of the box member.
7. 7. The connection of claim 1, wherein the roots and crests of the box and bolt members are planar and parallel to a longitudinal axis of the connection.
8. 8. The connection of claim 1, wherein the roots and crests of the box and bolt members have sufficient width to prevent any permanent deformation of the threads when the connection is made.
9. 9. The connection of claim 1, wherein the roots and ridges are adapted to move in engagement, before both the load flanks and the stress flanks move, in engagement to complete the sealing of the connection.
10. 10. The connection of claim 9, wherein one of the stress flanks and the load flanks move in engagement, as the bolt member moves within the box member, by the relative rotation of the members; the roots and ridges move in coupling during the construction of the rotation of the connection; and the other of the stress flanks and load flanks move in engagement in the rotation construction of the connection.
11. 11. The connection of claim 9, wherein the -flanges of "forces move in engagement as the bolt member moves within the box member, by the relative rotation of the members; the roots and ridges move in engagement during the "rotation construction of the connection; and - the load flanks move in engagement in the construction of rotation of the connection.
12. 12. A method "for relieving stresses from a threaded pipe connection, this method comprises: supplying a box member, having an internal tapered thread, generally in an assembly configuration, with stress flanks, load flanks, roots and ridges This internal thread has a beginning and an end and increases in width in one direction, providing a bolt member, which has an external tapered thread, generally in an assembly configuration, with stress flanks, load flanks, roots and crests, this external thread increases in width in the other direction, so that the complementary flanks of respective threads move in engagement during the construction of rotation of the connection and form sealing surfaces that resist the flow of fluids between the threads in the construction rotation of the connection; and forming a continuous annua on the roots of a section of one of the internal and external threads, extending from one of the beginning and end of a thread to a point between the beginning and the end of a thread, to reduce the pressure that develops between the sealing surfaces, during the construction of rotation in a thread lubricant, applied thereto.
13. 13. The method of claim 12, further comprising: supplying internal and external tapered threads.
14. 14. The method of claim 13, wherein the complementary roots and ridges move in engagement during the construction of rotation of the connection and form sealing surfaces that resist the flow of fluids between the threads.
15. 15. The method of claim 12, wherein the groove is a round bottom groove formed in the roots of a thread.
16. 16. The method of claim 12, further comprising: forming the groove at an intersection of the root and the load flank of a thread.
17. 17. The method of claim 12, wherein the continuous groove is formed in the roots of the bolt member.
18. 18. The method of claim 12, wherein the continuous groove is formed in the roots of the box member.
19. 19. The method of claim 12, further comprising: forming the roots and ridges of the box and pin members flat and parallel to a longitudinal axis of the connection.
20. 20. The method of claim 12, further comprising: forming the roots and ridges of the box and bolt members with sufficient width to prevent any permanent deformation of the threads when the connection is compensated.
21. 21. The method of claim 12, further comprising: adapting the roots and ridges to move in "engagement, before both the load flank and the stress flank move in engagement to complete the sealing of the connection.
22. 22. A method for relieving tension while compensating a threaded connector, this method comprises: supplying a box member, having a tapered, internal thread, generally in an assembly configuration, with stress flanks, load flanks, roots and crests, this internal thread has a beginning and an end and increases in width in one direction; - "- supplying a bolt member, which has a tapered, external thread, generally in an assembly configuration, with stress flanks, load flanks, roots and ridges, this external thread increases in width in the other direction, so that the complementary flanks of the respective threads move in engagement during the construction of rotation of the connection and form sealing surfaces that resist the flow of fluids between the threads in the construction of rotation of the connection, and apply a lubricant of threads on these threads of at least one of the box member and the bolt member, and rotationally coupling the box and bolt members to form the thread lubricant to flow through a slot, formed in the roots of the section of one of the internal and external threads, which extends from one of the beginning and the end of a thread to a point between the beginning and the end of a thread. SUMMARY OF THE INVENTION A stress reduction slot for tubular connections, which relate to a threaded pipe connection, and includes a box member, a bolt member and continuous groove nail formed in the thread of one of the members. The box member has a taper, internal thread, generally of an assembled configuration, with stress flanks, load flanks, roots and ridges. The internal thread has a beginning and an end and increases in width in one direction. The bolt member also has a tapered, external groove, generally in an assembled configuration, with stress flanks, load flanks, roots, and ridges, This external thread increases in width in the other direction, so complementary flanges of the respective threads move in engagement during the construction of rotation of the connection and form sealing surfaces that resist the flow of fluids between the threads in the construction of rotation of the connection. A section of one of the internal and external threads has a continuous groove formed in its roots. The slot extends from either the beginning or the end of a thread to a point between the start and end of another thread, thus reducing the pressure that develops between the sealing surfaces during construction in the thread lubricants applied to the same.