Protector for protecting the threaded pin of a pipe

Abstract

Protector 1 for protecting a threaded pin of a pipe for exploration and production of a hydrocarbon well. The protector 1 extends along a longitudinal axis from an open end 3 to a closed end 4, and comprises: • - a thread 20 for engaging the threaded pin, and • - a pin nose stop surface 16 provided at the closed end 4. The thread 20 starts and ends closer to a cross section plane intersecting the protector 1 halfway between the open end 3 and the closed end 4 than to the pin nose stop surface 16.

Description

[0001] Protector for protecting the threaded pin of a pipe

[0002] The present invention relates to a protector for protecting the threaded pin of a pipe, as well as a threaded pin assembled with said protector.

[0003] Such protector finds utility in the protection of a threaded pin of a pipe used in a threaded connection for the exploration and production of a hydrocarbon well. The protector protects the threaded pin against impacts and corrosion.

[0004] A protector for protecting the threaded pin of a pipe for exploration and production of a hydrocarbon well generally comprises an open end, a closed end opposite to the open end, and a thread located between the open end and the closed end. The open end is configured to receive the threaded pin of a pipe. The thread allows to mount the protector onto the threaded pin upon rotation of the protector with respect to the pin in a rotation direction, and to dismount the protector from the threaded pin by rotating the protector with respect to the pin in an opposite rotation direction.

[0005] Pipes for exploration and production of hydrocarbon wells, which are typically made of steel, are often stored in a yard where they are subjected to an outside environment. Depending on weather conditions, the outside temperature can vary wherein the material of the protectors and of the pipe can reach temperatures of -40 to 40 degrees Celsius.

[0006] A problem of existing threaded pin protectors is, that it can be difficult to dismount the protector from the threaded pin of a pipe, in particular in colder environments.

[0007] Attempts have been made to make it easier to dismount the protector from the pin of the threaded pipe.

[0008] For instance, it is possible to apply a lubricating dope on the pipe thread before assembling the protector with the threaded pin. The lubricating dope provides protection against corrosion, and makes it easier to dismount the protector. However, there remains a need to improve the dismounting process. It is an object of the present invention to provide an improved, or at least alternative, protector for protecting the threaded pin of a pipe wherein it is easier to dismount the protector from the threaded pin of the pipe, in particular in a cold environment.

[0009] The object is achieved in a first aspect of the present invention with a protector for protecting a threaded pin of a pipe for exploration and production of a hydrocarbon well, wherein the protector extends along a longitudinal axis from an open end to a closed end, the protector comprising: a thread for engaging the threaded pin, and a pin nose stop surface provided at the closed end, wherein the thread starts and ends closer to a cross section plane intersecting the protector halfway between the open end and the closed end than to the pin nose stop surface.

[0010] With a protector wherein the thread starts and ends closer to a cross section plane, which cross section plane intersects the protector halfway between the open end and the closed end, than to the pin nose stop surface, it is easier to dismount the protector from a threaded pin, in particular in colder environments, as less torque may be required to dismount the protector from the threaded pin.

[0011] As explained above, pipes for exploration and production of hydrocarbon wells are typically made of steel. Protectors, on the other hand, are generally made of a polymeric material, such as HDPE (High-Density polyethylene), or polypropylene. When studying the behaviour of protectors during the dismounting process, the inventors found that this difference in material plays an important role in the dismounting process.

[0012] In particular, the thermal expansion coefficient of the material of the protector can be much greater than the thermal expansion coefficient of the material of the threaded pin. This can cause that, as temperature decreases, the protector shrinks more than the pin onto which it is mounted. This behaviour may increase contact forces that need to be overcome when applying torque to rotationally dismount the protector from the threaded pin.

[0013] Continuing along this train of thought, the inventors analysed the general construction of the protector, wherein they realized that the closed end of the protector is generally much less flexible than the open end of the protector. By providing the protector thread at a distance from the pin nose stop surface, and therewith from the closed end, contact forces as a result of shrinkage of the protector with respect to the threaded pin can be diverted away from the closed end. This way, contact forces are mainly exerted at a distance from the closed end of the protector, in particular where the protector is more flexible. As such, shrinkage of the material of the protector has a smaller effect on the amount of torque required to unscrew the protector from the threaded pin. Accordingly, it is with the present invention easier to dismount the protector from the threaded pin.

[0014] In addition, as contact forces as a result of shrinkage may be reduced, the protector may experience less wear when being disassembled. As such, the present invention may provide a more sustainable protector.

[0015] With a cold environment may be meant a temperature lower than the temperature at which the protector has been mounted to a threaded pin of a pipe. In particular, with a cold environment may be meant a temperature of 0 to -40 degrees Celsius.

[0016] The protector has a longitudinal axis. The threaded pin has a pin longitudinal axis. When the protector is mounted to the threaded pin, the pin longitudinal axis and the longitudinal axis of the protector are coaxial.

[0017] The protector comprises two longitudinal ends. In particular, the protector comprises a (longitudinal) open end, and a (longitudinal) closed end opposite to the open end.

[0018] The pin nose stop surface may be annular. In particular, the pin nose stop surface surrounds the longitudinal axis. The annular pin nose stop surface faces towards the open end.

[0019] Within the context of the present disclosure, the term “radial” may refer to a direction perpendicular to the longitudinal axis.

[0020] Within the context of the present disclosure, the term “axial” may mean: in the direction of, or along, the longitudinal axis. The protector can have a (substantially) cylindrical shape. In particular, the protector may have a rectangular shape when seen in longitudinal section through the longitudinal axis.

[0021] The protector can comprise a circumferential wall. The circumferential wall has an outer circumferential wall surface, and an inner circumferential wall surface. In particular, the protector may comprise a tubular portion comprising the circumferential wall. The circumferential wall has a wall thickness measured in radial direction with respect to the longitudinal axis, when seen in a longitudinal section plane through the longitudinal axis, between the outer circumferential wall surface and the inner circumferential wall surface. Wall thickness at the thread may be measured in radial direction between the root of the thread and the outer circumferential wall surface.

[0022] The (helical) thread is located between the open end and the closed end of the protector. In particular, the thread is provided at the inner circumferential wall surface. As such, the thread is an internal thread. The thread of the protector is configured to rotationally engage a(n external) pin thread of a threaded pin, which pin thread is provided at an outer circumferential surface of the pin.

[0023] The thread comprises a thread start, and a thread end. The thread start may be located, in longitudinal direction along the longitudinal axis, closer to the pin nose stop surface than the thread end. The thread start is located at a longitudinal thread start distance from the pin nose stop surface, and the thread end is located at a longitudinal thread end distance from the pin nose stop surface. In particular, the longitudinal thread start distance is smaller than the longitudinal thread end distance.

[0024] The thread of the protector (or protector thread) may be tapered so as to reduce in inner diameter from the open end to the closed end. The thread of the pin of the pipe may be tapered so as to increase in outer diameter from a terminal end of the pin to a pipe body end of the pin. The protector thread and the pin thread extend along a protector thread taper angle and a pin thread taper angle, respectively. Preferably, the thread taper angle of the protector thread is equal to the thread taper angle of the thread of the pin (or pin thread). The thread taper angle of the thread of the protector may be taken between the longitudinal axis of the protector and a plane extending through the thread pitch diameter of the protector thread. Similarly, the thread taper angle of the thread of the pin may be taken between the longitudinal axis of the pin (and pipe) and a plane extending through the thread pitch diameter of the pin thread.

[0025] Within the context of the present disclosure, the cross section plane may be a virtual cross section plane. The cross section plane may extend perpendicular to the longitudinal axis.

[0026] Embodiments in accordance with the first aspect, and a second aspect, of the present invention are described in the following.

[0027] In an embodiment in accordance with the first aspect of the present invention, the thread is a longest (helical) thread. In particular, the longest thread starts and ends closer to a cross section plane intersecting the protector halfway between the open end and the closed end than to the pin nose stop surface.

[0028] With a longest thread may be meant that the thread has a greater helical thread length than any other thread comprised by the protector.

[0029] In an embodiment in accordance with the first aspect of the present invention, the (protector) thread includes at least three thread turns. The at least three thread turns may be complete thread turns. With a complete thread turn may be meant that the thread turns are fully formed thread turns.

[0030] As is convention in the technical field, a “thread turn” may refer to a turn of a thread extending 360 degrees along the circumference of the protector or pin.

[0031] In an embodiment in accordance with the first aspect of the present invention, the (protector) thread includes at most five thread turns. In particular, the thread includes at most five complete thread turns.

[0032] A protector with at least three thread turns and at most five thread turns may be easy to rotationally dismount, in particular at lower temperatures, wherein the thread provides sufficient support to pass a standardized stripping test.

[0033] In an embodiment in accordance with the first aspect of the present invention, the (protector) thread extends along a tapered thread pitch diameter. In an embodiment in accordance with the first aspect of the present invention, the open end comprises an annular longitudinal end surface. The annular longitudinal end surface faces away from the closed end. The annular longitudinal end surface may extend (substantially) perpendicular with respect to the longitudinal axis of the protector.

[0034] In particular, the open end may comprise an annular rim that defines an opening for inserting the threaded pin into the protector. The annular rim may comprise the annular longitudinal end surface.

[0035] In an embodiment in accordance with the first aspect of the present invention, the cross section plane intersects the protector halfway between the annular longitudinal end surface and the pin nose stop surface. In this embodiment, the thread starts and ends closer to a cross section plane intersecting the protector halfway between the annular longitudinal end surface of the open end and the pin nose stop surface of the closed end than to the pin nose stop surface.

[0036] In an embodiment in accordance with the first aspect of the present invention, the thread starts and ends closer to the cross section plane intersecting the protector halfway between the open end and the closed end than to the annular longitudinal end surface. Hence, in this embodiment, the thread starts and ends closer to a cross section plane intersecting the protector halfway between the open end and the closed end than to: the pin nose stop surface, and the annular longitudinal end surface.

[0037] In an embodiment in accordance with the first aspect of the present invention, the thread starts at a longitudinal thread start distance from the pin nose stop surface, wherein the longitudinal thread start distance is at least one third of a longitudinal interior length defined between the annular longitudinal end surface and the pin nose stop surface.

[0038] In an embodiment in accordance with the first aspect of the present invention, the protector comprises a second thread. The second thread may be closer to the open end, in particular closer to the annular longitudinal end surface, than the first thread. The second thread may be further from the cross section plane than the first thread. The second thread may comprise at least one, and / or at most one, (complete) thread turn. In other words, the second thread may comprise only one (complete) thread turn, or only a single (complete) thread turn.

[0039] In embodiments where the protector comprises more than one thread, the thread that starts and ends closer to the cross section plane than to the pin nose stop surface may be referred to as a first (or primary) thread, and another thread may be referred to as a second (or secondary) thread. Yet another thread may be referred to as a third (or tertiary) thread.

[0040] In an embodiment of the present invention, the second thread comprises a second thread start, and a second thread end. The second thread start may be located closer to the pin nose stop surface than the second thread end. The second thread start is located at a longitudinal second thread start distance from the pin nose stop surface, and the second thread end is located at a longitudinal second thread end distance from the pin nose stop surface. As such, the second thread starts at a longitudinal second thread start distance from the pin nose stop surface, and ends at a longitudinal second thread end distance from the pin nose stop surface. The second longitudinal thread start distance and the second longitudinal thread end distance may be greater than the first longitudinal thread start distance and the first longitudinal thread end distance, respectively. In particular, the second longitudinal thread start distance is smaller than the second longitudinal thread end distance. The second thread start is located at a distance from the first thread end.

[0041] As will be appreciated from the discussion above, the first thread and the second thread may form two discrete (separate) threads. The first thread and second thread may be spaced apart on the inner circumferential wall surface in the axial direction.

[0042] The second thread helps to prevent water from reaching the thread of the pin, in particular the thread of the pin that engages the first thread of the protector.

[0043] In an embodiment in accordance with the first aspect of the present invention, the first thread extends along a first thread pitch diameter and the second thread extends along a second thread pitch diameter, wherein a plane aligned with the first thread pitch diameter coincides with a plane aligned with the second thread pitch diameter.

[0044] In an embodiment in accordance with the first aspect of the present invention, the first thread starts at a longitudinal thread start distance from the pin nose stop surface, wherein the longitudinal thread start distance is at least one third of a longitudinal length between the thread end of the second thread and the pin nose stop surface.

[0045] In an embodiment in accordance with the first aspect of the present invention, the protector further comprises a circumferential wall with a first circumferential wall portion located (in longitudinal direction) between the (first) thread and the pin nose stop surface, and wherein the circumferential wall has a greater wall thickness at the thread than at the first circumferential wall portion. The wall thickness at the first circumferential wall portion may be between 40% and 60% of the wall thickness at the thread. As mentioned above, wall thickness at the thread may be measured in radial direction between the root of the thread and the outer circumferential wall surface. The first circumferential wall portion may have an inner diameter that is greater than a root diameter of the first thread.

[0046] In an embodiment in accordance with the present invention the protector further comprises a circumferential wall with a first circumferential wall portion located (in longitudinal direction) between the (first) thread and the pin nose stop surface, wherein a first annular groove is provided in the first circumferential wall portion. In particular, the circumferential wall comprises an inner circumferential surface, wherein the first annular groove is provided in the inner circumferential surface of the circumferential wall. In particular, the first annular groove has in longitudinal direction along the longitudinal axis a first annular groove width and in a direction around the longitudinal axis a first annular groove length. The first annular groove may define a first radially extending boundary surface extending towards the (first) thread. The first radially extending boundary surface may extend perpendicular with respect to the longitudinal axis.

[0047] In an embodiment in accordance with the first aspect of the present invention, the first annular groove has a first annular groove inner surface, wherein the first annular groove inner surface is in radial direction with respect to the longitudinal axis further from the longitudinal axis than the (first) thread.

[0048] In an embodiment in accordance with the first aspect of the present invention, the first circumferential wall portion adjoins the closed end at the pin nose stop surface. In an embodiment in accordance with the first aspect of the present invention, the first annular groove has in longitudinal direction along the longitudinal axis a first annular groove width of at most 4 mm.

[0049] An advantage of embodiments with a first circumferential wall portion is, that flexibility at the first circumferential wall portion may be increased, wherein contact forces as a result of shrinkage of the material of the protector are reduced at the first thread.

[0050] In an embodiment in accordance with the first aspect of the present invention, the protector further comprises a circumferential wall with a second circumferential wall portion located (in longitudinal direction) between the (first) thread and the open end, wherein the circumferential wall has a greater wall thickness at the thread than at the second circumferential wall portion. The wall thickness at the second circumferential wall portion may be 40% to 60% of the wall thickness at the thread. The second circumferential wall portion may have an inner diameter that is greater than a root diameter of the first thread.

[0051] In an embodiment in accordance with the first aspect of the present invention, the protector further comprises a circumferential wall with a second circumferential wall portion located (in longitudinal direction) between the (first) thread and the open end, wherein a second annular groove is provided in the second circumferential wall portion. In particular, the circumferential wall comprises an inner circumferential surface, wherein the second annular groove is provided in the inner circumferential wall surface. In particular, the second annular groove has in longitudinal direction along the longitudinal axis a second annular groove width and in a direction around the longitudinal axis a second annular groove length. The second annular groove may define a second radially extending boundary surface extending towards the (first) thread. The second radially extending boundary surface may extend perpendicular with respect to the longitudinal axis.

[0052] The second annular groove may further define a third radially extending boundary surface (in longitudinal direction) opposite the second radially extending boundary surface. The third radially extending boundary surface extends towards the inner circumferential surface. In embodiments with a second thread, the third radially extending boundary surface extends towards the second thread. The second radially extending boundary surface may extend perpendicular to the longitudinal axis. In an embodiment in accordance with the first aspect of the present invention, the second annular groove has a second annular groove inner surface, wherein the second annular groove inner surface is in radial direction with respect to the longitudinal axis further from the longitudinal axis than the (first) thread.

[0053] The first annular groove and / or second annular groove may be machined in the inner circumferential wall surface of the circumferential wall. Alternatively, the first annular groove and / or the second annular groove may be formed by injection moulding.

[0054] In an embodiment in accordance with the first aspect of the present invention, the second annular groove has in longitudinal direction along the longitudinal axis a second annular groove width of at most 4 mm.

[0055] Embodiments with a first and / or second circumferential wall portion may further reduce contact forces as a result of shrinkage of the material of the protector at the (first and / or second) thread.

[0056] In an embodiment in accordance with the first aspect of the present invention, the protector is made of a thermoplastic polymer, in particular HDPE. In particular, the thermoplastic polymer is reinforced with glass fiber. The protector may be injection moulded.

[0057] In an embodiment in accordance with the first aspect of the present invention, the pin nose stop surface comprises an inner circumferential edge and an outer circumferential edge, wherein the inner circumferential edge is in longitudinal direction along the longitudinal axis closer to the open end than the outer circumferential edge. The pin nose stop surface may be straight when seen in the longitudinal section through the longitudinal axis. As such, the pin nose stop surface may extend conically.

[0058] In an embodiment in accordance with the first aspect of the present invention, the pin nose stop surface extends along a pin nose stop surface angle taken between the longitudinal axis and the pin nose stop surface of 80 degrees.

[0059] An advantage of the above two embodiments is, that shrinkage of the material of the protector in radial direction (towards the longitudinal axis) tends to reduce contact between the pin nose stop surface and the pin nose. In an embodiment in accordance with the first aspect of the present invention, the first thread is an integral part of the protector. In particular, the first thread is integrally formed with the circumferential wall.

[0060] In an embodiment in accordance with the first aspect of the present invention, the second thread is an integral part of the protector. In particular, the second thread is integrally formed with the circumferential wall.

[0061] In an embodiment in accordance with the first aspect of the present invention, the protector has an inner diameter at the open end of larger than 245 mm.

[0062] In an embodiment in accordance with the first aspect of the present invention, the protector may have a cylindrical shape.

[0063] Larger protectors tend to shrink more in absolute size than smaller protectors. For protectors having a(n inner) diameter larger than 245 mm, reducing contact forces as a result of shrinkage is particularly relevant.

[0064] In a second aspect of the present invention there is provided a threaded pin of a pipe for exploration and production of a hydrocarbon well, comprising a protector in accordance with the first aspect of the present invention.

[0065] It will be clear to the skilled person that the second aspect of the present invention may include features relating to the first aspect of any combination of the above-described embodiments of the first aspect of the present invention.

[0066] For a better understanding of the present invention, and to show how the same may be put into effect, reference will now be made, by way of example only, to the accompanying drawings in which:

[0067] Figure 1A - 1 E show partial longitudinal section views of various protectors;

[0068] Figure 2 shows a partial longitudinal section view of another protector; and

[0069] Figure 3 shows a break out torque turns graph of further protectors. Figures 1 A - 1 E show partial longitudinal section views of various protectors for protecting a threaded pin of a pipe for exploration and production of a hydrocarbon well. The protectors 1 , each having a generally cylindrical shape, comprise a longitudinal axis 2, a (longitudinal) open end 3, and a (longitudinal) closed end 4. The closed end 4 is, in a longitudinal direction 5 along the longitudinal axis 2, located opposite to the open end 3.

[0070] The protectors 1 are formed of a single piece of material. In particular, the material is a thermoplastic, preferably HDPE.

[0071] The protectors 1 comprise a tubular portion 6, and a cover 7. The tubular portion 6 is integrally formed with the cover 7. The tubular portion 6 extends from the open end 3 up to the closed end 4. The protector 1 , in particular the tubular portion 6, includes an annular rim 8 that defines an opening 9 for receiving a threaded pin (not shown). The annular rim 8 has an annular longitudinal end surface 10. The annular longitudinal end surface 10 faces away from the closed end 4.

[0072] The tubular portion 6 comprises a circumferential wall 11 . The circumferential wall 11 has an outer circumferential wall surface 12, and an inner circumferential wall surface 13. The circumferential wall 11 has a wall thickness 14 measured in radial direction 15 between the outer circumferential wall surface 12 and the inner circumferential wall surface 13. The outer circumferential wall surface 12 has a single diameter. The inner circumferential wall surface 13 is tapered, wherein inner circumferential wall surface 13 has a larger diameter at the open end 3 than at closed end 4.

[0073] The closed end 4 comprises the cover 7, and a pin nose stop surface 16. Even though the cover 7 is depicted in Figures 1 A - 1 E as extending perpendicular to the longitudinal axis 2, the cover 7 can have parts extending in longitudinal direction 5 along the longitudinal axis 2 (as shown in Figure 2).

[0074] A longitudinal interior length 17 for receiving a threaded pin in the protector 1 is defined between the annular longitudinal end surface 10 and the pin nose stop surface 16.

[0075] The closed end 4 further comprises an annular bumper 18. The annular bumper 18 extends from the cover 7 along the longitudinal axis 2 away from the pin nose stop surface 16. The bumper 18 is provided at an outer circumference 19 of the closed end 4. The bumper 18 can safeguard the cover 7 (and threaded pin) from impacts. In the shown embodiments, the bumper 11 is integrally formed with the cover 7.

[0076] The pin nose stop surface 16 is configured to stop the threaded pin of the pipe as the threaded pin is screwed together with the protector 1 . However, it should be appreciated that the threaded pin does not necessarily contact the pin nose stop surface 16 when the protector 1 is mounted to the threaded pin. There can be an axial gap between the pin nose stop surface 16 and the threaded pin when the protector 1 has been assembled with the threaded pin.

[0077] The protector 1 comprises a thread 20 between the open end 3 and the closed end 4. The thread 20 comprises (complete) thread turns 21 . The thread 20 is located in the tubular portion 6, in particular at the inner circumferential wall surface 13 of the tubular portion 6. As such, the thread 20 can engage a thread provided on an outer surface of a pin.

[0078] The thread 20 is located closer to the longitudinal open end 3 than the pin nose stop surface 16. Also, the pin nose stop surface 16 extends in radial direction 15 closer to the longitudinal axis 2 than the thread 20.

[0079] The thread 20 has a thread start 22 located at a longitudinal thread start distance 23 from the pin nose stop surface 16, and a thread end 24 located at a longitudinal thread end distance 25 from the pin nose stop surface 16. The thread start 22 is located closer to the pin nose stop surface 16 than the thread end 24.

[0080] In the embodiment of Figure 1 A, the thread 20 starts at a small longitudinal thread start distance 23 from the pin nose stop surface 16, and the thread 20 ends close to the annular longitudinal end surface 10.

[0081] In the embodiments of Figures 1 B, 1 C, and 1 E, longitudinal thread start distance 23 is greater than in the embodiment of Figure 1 A. In particular, in each of the embodiments of Figure 1 B, 1 C, and 1 E, the thread 20 starts and ends closer to a cross section plane 26 intersecting the protector 1 halfway between the open end 3 and the closed end 4 than to the pin nose stop surface 16. Differently put; the thread 20 has a thread start 22 and a thread end 24, wherein the thread start 22 and the thread end 24 are closer to a cross section plane 26 intersecting the protector 1 halfway between the open end 3 and the closed end 4 than to the pin nose stop surface 16. In particular, the thread 20 is a longest thread 20 of the protector 1 .

[0082] As can be seen in Figures 1 B - 1 E, the protector 1 can have more than one thread. In the embodiment of Figure 1 B the protector 1 comprises a first (or primary) thread 20, and a second (or secondary) thread 27. In the embodiment of Figure 1 D, the protector further comprises a third (or tertiary) thread 28.

[0083] In each embodiment, the first thread 20 has more thread turns 21 than the second thread 27 and / or the third thread 28. As such, the first thread 20 is the longest thread provided on the protector 1 . The first, second, and third, threads 20, 27, 28 extend along a first thread pitch diameter 29, a second thread pitch diameter 30, and a third thread pitch diameter 31 , respectively. The thread pitch diameters 29, 30, 31 are aligned. In particular, a (virtual) plane extending in alignment with the first thread pitch diameter 29 coincides with the second thread pitch diameter 30 and the third thread pitch diameter 31 .

[0084] The second thread 27 has a second thread start 32, and a second thread end 33. The second thread start 32 is located at a longitudinal second thread start distance 34 from the pin nose stop surface 16. The second thread end 33 is located at a longitudinal second thread end distance 35 from the pin nose stop surface 16. The longitudinal second thread start distance 34 and the longitudinal second thread end distance 35 are greater than the longitudinal first thread start distance 23 and the longitudinal first thread end distance 25.

[0085] The second thread 27 has a single thread turn 21 . As such, the second thread 27 helps to prevent water from reaching the threads 20, 27 while at the second thread there is a small contact area for contacting the threaded pin available. As an alternative to inclusion of the second thread 27, an annular sealing member may be provided, such as an annular cam or an annular element having a radially extending flap. Preferably, the annular sealing member is made of a material that is more flexible than the material of the protector 1 .

[0086] With reference to the embodiment shown in Figure 1 D, the third thread 28 comprises a third thread start 36, and a third thread end 37. The third thread start 36 is located closer to the pin nose stop surface 16 than the third thread end 37. The third thread start 36 is located at a longitudinal third thread start distance 38 from the pin nose stop surface 16. The third thread end 37 is located at a longitudinal third thread end distance 39 from the pin nose stop surface 16. The longitudinal third thread start distance 38 and the longitudinal third thread end distance 39 are smaller than the longitudinal first thread start distance 23.

[0087] In the embodiments shown in Figures 1 D and 1 E, the protector 1 comprises a first circumferential wall portion 40 between the first thread 20 and the pin nose stop surface 16, and a second circumferential wall portion 41 between the first thread 20 and the open end 3. In the first circumferential wall portion 40 a first annular groove 42 is provided. In the second circumferential wall portion 41 a second annular groove 43 is provided. The first annular groove 42 is provided between the longitudinal first thread start 22 and the pin nose stop surface 16. The second annular groove 43 is provided between the longitudinal first thread end 24 and the second thread start 32. The first annular groove 42 has a first annular groove width 44 in longitudinal direction 5 and a first annular groove length (not shown) extending in tangential direction with respect to the longitudinal axis. The first annular groove width is narrow compared with the first annular groove length. The second annular groove 43 has a second annular groove width 45 in longitudinal direction and a second annular groove length (not shown) extending in tangential direction with respect to the longitudinal axis. The second annular groove width is narrow compared with the second annular groove length. The first annular groove width 44 is preferably about 4 mm. The second annular groove width 45 is preferably also about 4 mm.

[0088] The first annular groove 42 defines a first annular groove inner surface 56, a first radially extending boundary surface 57, and a further radially extending boundary surface 58 located in longitudinal direction 5 along the longitudinal axis 2 opposite to the first radially extending boundary surface 57. The first radially extending boundary surface 57 is located adjacent to the first thread 20 and extends in radial direction towards the thread 20. The further radially extending boundary surface 58 is located closer to the closed end 4. In the embodiment of Figure 2, the further radially extending boundary surface 58 is part of the pin nose stop surface 16.

[0089] The second annular groove 43 defines a second annular groove inner surface 59, a second radially extending boundary surface 60, and a third radially extending boundary surface 61 located in longitudinal direction 5 along the longitudinal axis 2 opposite to the second radially extending boundary surface 60. The second radially extending boundary surface 60 is located adjacent to the first thread 20 and extends in radial direction towards the thread 20. The third radially extending boundary surface 61 is located closer to the open end 3. In particular, the third radially extending boundary surface 61 extends in radial direction towards the inner circumferential surface 3 and the second thread 27.

[0090] As shown in Figures 1 D, 1 E, and 2, the first annular groove inner surface 56 as well as the second annular groove inner surface 59 are cylindrical, wherein the first annular groove inner surface 56 and the second annular groove inner surface 59 are located at a greater diameter than the thread 20.

[0091] In the embodiment of Figure 1 D, the first annular groove 42 is located between the first thread 20 and the third thread 28.

[0092] Each of the protectors of Figures 1 A - 1 E has been tested, wherein the (break-out) torque required to unscrew the protectors 1 from a threaded pin was measured. Each of the tested protectors 1 has an inner diameter at the open end of the protector of about 51 / z” (13,97 cm), and API buttress thread. The protectors were screwed onto a threaded pin of a pipe having a nominal outer diameter of 51 / z” (13,97 cm) and API buttress thread. Each protector was assembled with the threaded pin at room temperature wherein a (make-up) torque of 75 Ib-ft (pound-foot) was applied to mount the protector 1 to the threaded pin. The break-out torque was measured at 0 degrees Celsius.

[0093] The tests resulted in the following break out torques wherein for the:

[0094] - protector of Figure 1 A a break-out torque of 275 Ib-ft was measured;

[0095] - protector of Figure 1 B a break-out torque of 190 Ib-ft was measured;

[0096] - protector of Figure 1 C a break-out torque of 190 Ib-ft was measured;

[0097] - protector of Figure 1 D a break-out torque of 180 Ib-ft was measured; and

[0098] - protector of Figure 1 E a break-out torque of 100 Ib-ft was measured.

[0099] Figure 2 shows a partial longitudinal section view of another protector 1 . The protector 1 has many features in common with the protectors 1 of Figures 1 A - 1 E. Similar reference signs are used to refer to similar parts of the protector 1 .

[0100] The protector 1 , which extends along a longitudinal axis 2, comprises a longitudinal open end 3, and a longitudinal closed end 4, a first thread 20 located between the open end 3 and the closed end 4, and a second thread 27 located between the open end 3 and the first thread 20. The closed end 3 comprises an annular pin nose stop surface 16. Different from the embodiments shown in Figure 1 A - 1 E, the protector 1 of Figure 2 comprises a pin nose stop surface 16 that is non-perpendicular to the longitudinal axis 2 of the protector 1 . In particular, the pin nose stop surface 16 comprises an inner circumferential edge 46 and an outer circumferential edge 47. The inner circumferential edge 46 is in radial direction 15 closer to the longitudinal axis 2 than the outer circumferential edge 47. Further, the inner circumferential edge 46 is in longitudinal direction 48 along the longitudinal axis 2 located closer to the first thread 20 than the outer circumferential edge 47.

[0101] When seen in longitudinal section through the longitudinal axis 2 of the protector 1 , the pin nose stop surface 16 extends along a pin nose stop surface angle 49 of about 80 degrees. The pin nose stop surface angle 49 may be measured between the pin nose stop surface 16 and the longitudinal axis 2. In particular, the pin nose stop surface angle 49 is a smallest angle measured between the pin nose stop surface 16 and the longitudinal axis 2.

[0102] The cover 7 of the protector 1 of Figure 2 comprises a central portion 50 and a cover base portion 51 . The central portion 50 extends in longitudinal direction 48 from the cover base portion 51 to the open end 3. In particular, the central portion 50 extends in longitudinal direction 48 beyond the first thread 20.

[0103] Figure 3 shows a break out torque-turns graph indicating the behaviour of four different protectors 1 while rotationally dismounting the protector from a threaded pin. The tested protectors 1 , which are all made of HDPE, have an inner diameter at the open end of the protector of about 9 5 / 8” (24,45 cm). The protectors were mounted on the threaded pin of a pipe having a nominal outer diameter of 9 5 / 8” (24,45 cm). The graph shows the torque applied (along the Y-axis) over a number of turns (X-axis) to dismount the protectors 1 from their pin. The dismounting process was performed at a temperature of -10 degrees Celsius.

[0104] In the graph, line 52 shows the torque-turn behaviour of a protector as shown in Figure 1 A wherein a solid lubricant was applied to the thread of the pin, line 53 shows the torque-turn behaviour of a protector as shown in Figure 1 A wherein a viscous lubricating dope was applied to the thread of the pin, line 54 shows the torque-turn behaviour of a protector 1 as shown in Figure 2 wherein a viscous lubricating dope was applied to the thread of the pin, and line 55 shows the torque-turn behaviour of the protector of Figure 2 wherein a solid lubricant was applied to the thread of the pin.

[0105] From Figure 3 it is clear that dismounting the protector 1 in accordance with the design of Figure 1 A may require a relatively large amount of torque over a relatively large number of turns. Line 53 shows that applying a lubricating dope helps to reduce the amount of torque required. However, still a relatively large amount of torque over a large number of turns is required to dismount the protector 1 .

[0106] Looking at the lines 54 and 55, one can see that less torque is required to dismount the protectors from their pins. In addition, it is noted that the maximum amount of torque required to unscrew the protectors is within the first 0,01 turns of the dismounting process. Thereafter, the amount of torque required to further loosen the protectors dissipates rapidly. This behaviour is clearly different from the behaviour expressed by lines 52 and 53, as in the process of unscrewing the protectors of lines 52 and 53 there is a build-up of resistance in the first 0,02 to 0,03 turns.

[0107] As required, detailed embodiments of the present invention have been disclosed in the Figures. However, it is to be understood that the disclosed embodiments are merely exemplary, wherein the invention can be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed structure.

[0108] In particular, the thread 20, 27, 28 of the protector 1 may have a run-in and / or a run-out or a higbee cut at the thread start and / or thread end.

[0109] The terms “a” or “an”, as used herein, are defined as one or more than one. The terms multitude or plurality, as used herein, are defined as two or more than two. The term another, as used herein, is defined as at least a second or more. The terms including and / or having, as used herein, are defined as comprising (i.e. open language, not excluding other elements or steps). Any reference signs in the claims should not be construed as limiting the scope of the claims or the invention. It will be apparent to those skilled in the art that various modifications can be made to the shown protector, and threaded pin with protector, according to the invention without departing from the scope as defined by the claims.

Claims

CLAIMS1 . Protector for protecting a threaded pin of a pipe for exploration and production of a hydrocarbon well, wherein the protector extends along a longitudinal axis from an open end to a closed end, the protector comprising: a thread for engaging the threaded pin, and a pin nose stop surface provided at the closed end, wherein the thread starts and ends closer to a cross section plane intersecting the protector halfway between the open end and the closed end than to the pin nose stop surface.

2. Protector of claim 1 , wherein the open end comprises an annular longitudinal end surface, wherein the thread starts and ends closer to the cross section plane intersecting the protector halfway between the open end and the closed end than to the annular longitudinal end surface.

3. Protector of claim 1 or 2, wherein the open end comprises an annular longitudinal end surface, and the thread starts at a longitudinal thread start distance from the pin nose stop surface, the longitudinal thread start distance being at least one third of an longitudinal interior length defined between the annular longitudinal end surface of the open end and the pin nose stop surface.

4. Protector of any of the preceding claims, wherein the protector comprises a second thread, wherein the second thread is provided closer to the open end than the first thread.

5. Protector of claim 4, wherein the second thread comprises one thread turn.

6. Protector of any of claims 4 or 5, wherein a plane aligned with the thread pitch diameter of the first thread coincides with a plane aligned with the thread pitch diameter of the second thread.

7. Protector of any of claims 4 to 6, wherein the first thread starts at a longitudinal thread start distance from the pin nose stop surface, and wherein the longitudinal thread start distance is at least one third of a longitudinal length between the thread end of the second thread and the pin nose stop surface.

8. Protector of any of the preceding claims, wherein the protector further comprises a circumferential wall with a first circumferential wall portion located between the thread and the pin nose stop surface, and wherein the circumferential wall has a greater wall thickness at the thread than at the first circumferential wall portion.

9. Protector of claim 8, wherein a first annular groove is provided in the first circumferential wall portion.

10. Protector of claim 8 or 9, wherein the circumferential wall includes a second circumferential wall portion located between the thread and the open end, and wherein the circumferential wall has a greater wall thickness at the thread than at the second circumferential wall portion.11 . Protector of claim 10, wherein a second annular groove is provided in the second circumferential wall portion.

12. Protector of any of the preceding claims, wherein the protector is made of a thermoplastic, in particular HDPE, more in particular reinforced with glass fiber.

13. Protector of any of the preceding claims, wherein the pin nose stop surface comprises an inner circumferential edge and an outer circumferential edge, wherein the inner circumferential edge is in longitudinal direction closer to the open end than the outer circumferential edge.

14. Protector of any of the preceding claims, wherein the pin nose stop surface extends along an pin nose stop surface angle taken between the longitudinal axis and the pin nose stop surface of 80 degrees.

15. Protector of any of the preceding claims, wherein the thread is an integral part of the protector.

16. Protector of any of the preceding claims, wherein the protector has an inner diameter at the open end of larger than 245 mm.

17. Threaded pin of a pipe for exploration and production of a hydrocarbon well, comprising a protector in accordance with any of the preceding claims.

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