Joining metal fittings to a polymer composite pipe

Abstract

A fitting is attached to a composite pipe by inserting a tubular root portion of the fitting into an end of the pipe and then tensioning longitudinally-extending tensile elements distributed around the fitting. This moves an outer wedge component of the fitting longitudinally relative to the pipe to force an opposed inner wedge formation radially inwardly toward the roof portion, clamping the fitting to the pipe. The fitting may be an end fitting to enable the pipe to be joined to another pipe or conduit, or may be an in-line fitting used to join two lengths of pipe end-to-end.

Claims

1. A rigid pipe of composite material in combination with a fitting for the pipe, the fitting comprising: at least one tubular root portion; an outer wedge component that is movable longitudinally relative to the root portion to force an opposed inner wedge formation radially inwardly toward the root portion to clamp the composite pipe between the inner wedge formation and the root portion, wherein the inner wedge formation is integral with the pipe; and at least two longitudinally extending tensile elements that act in tension on the outer wedge component to effect said for longitudinal movement; wherein the tensile elements extend along respective passageways that extend longitudinally through the outer wedge component and the inner wedge formation.

2. The combination of claim 1, wherein the inner wedge formation extends circumferentially around, and is spaced radially from, the root portion to define an annular clamping gap that, in use, accommodates a wall of the pipe.

3. The combination of claim 1, wherein the tensile elements comprise one or more rods, bolts, studs or straps, or any combination thereof.

4. The combination of claim 1, wherein at least one of the tensile elements comprises a tensioner or fastening that is offset proximally with respect to, and located on an outer proximally tapering side of, the outer wedge component.

5. The combination of claim 1, wherein the passageways also extend longitudinally through a flange that extends radially in a plane offset longitudinally from the root portion.

6. The combination of claim 1, wherein the outer wedge component is a sleeve that encircles the root portion.

7. The combination of claim 1, being an end fitting having a joint formation that is disposed distally with respect to the root portion.

8. The combination of claim 7, wherein each tensile element acts between anchorages disposed respectively on the outer wedge component and on a stem portion that extends distally from the root portion.

9. The combination of claim 7, wherein the passageways also extend longitudinally through a flange that extends radially in a plane offset longitudinally from the root portion, comprising an integral tubular stem component that defines the root portion at a proximal end, the joint formation at a distal end and the flange extending radially outwardly between those ends.

10. The combination of claim 9, wherein the flange locates the inner wedge formation against longitudinal movement.

11. The combination of claim 9, wherein each tensile element extends between the outer wedge component and the flange.

12. The combination of claim 1, wherein the composite pipe is fitted with the fitting.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

(1) To explain the prior art background, reference has already been made to FIGS. 1 and 2 of the drawings, in which:

(2) FIG. 1 is a perspective view of a composite tube fora composite pipeline as known in the prior art; and

(3) FIG. 2 is a view in longitudinal section of an end joined to a composite tube, as also known in the prior art.

(4) In order that the invention may be more readily understood, reference will now be made, by way of example, to the remainder of the accompanying drawings, in which:

(5) FIG. 3 is a side view in longitudinal section of an end fitting joined to a composite tube in a first embodiment of the invention;

(6) FIG. 4 is a side view in longitudinal section of an end fitting joined to a composite tube in a second embodiment of the invention;

(7) FIG. 5 is a side view in longitudinal section of a joint joining two composite tubes in a third embodiment of the invention; and

(8) FIG. 6 is a side view in longitudinal section of a joint joining two composite tubes in a fourth embodiment of the invention.

(9) FIG. 7 is a side view in longitudinal section of an end fitting joined to a composite tube in a fifth embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

(10) FIG. 3 shows a first embodiment of the invention in the form of a steel end fitting 50 for a composite pipe 52. The pipe 52 shown in FIG. 3 further comprises a composite tube 54.

(11) As in the prior art arrangement shown in FIG. 2, the end fitting 50 comprises an elongate tubular stem 56, a wedge system 58 that serves as an inner wedge formation and a tubular frusto-conical sleeve 60 that serves as an outer wedge component. Thus, the sleeve 60 surrounds and cooperates with the wedge system 58 to lock the end fitting 50 to the tube 54.

(12) Again, the stem 66 is an integral steel forging that rotationally symmetrical about a central longitudinal axis 28 and that has a substantially constant internal diameter along its full length. In this example, however, a joint formation exemplified by the coupling flange 32 of FIG. 2 has been omitted from the stem 56.

(13) Similarly, the stem 55 has a tubular root portion 62 at a proximal end for engaging the composite tube 54 to secure the end fitting 50 to the tube 54. The root portion 62 is an interference fit within a distal end portion of the tube 54. The root portion 62 may be sealed to the surrounding tube 54 by a series of circumferential gaskets as shown in FIG. 2, although such gaskets have been omitted from FIG. 3.

(14) The stem 56 extends distally from the root portion 62 to protrude distally beyond the distal end of the tube 54. Here, like the locking flange of FIG. 2, a tensioning flange 64 extends radially from the protruding end of the stem 56 and exceeds the outer diameter of the tube 54. Similarly, the tensioning flange 64 bears against the distal end of the tube 54.

(15) The sleeve 60 is adapted relative to the prior art sleeve of FIG. 2. In particular, the distal end ring 46 of the sleeve 26 of FIG. 2 is omitted and there is at least one shoulder 66 at the proximal end of the sleeve 60. Preferably, as shown, the radial extent of the shoulder 66 does not exceed the radial extent of the distal end of the sleeve 60.

(16) The tensioning flange 64, the wedge system 58 and the sleeve 60 are penetrated by mutually-aligned bores that together define longitudinally-extending passageways 68. Each passageway 68 extends from a proximal end at the proximal face of the shoulder 66 to a distal end at the distal face of the tensioning flange 64.

(17) One such passageway 68 is shown on the upper side of the tube 54 in FIG. 3. It will be apparent that the passageways 68 extend substantially parallel to the central longitudinal axis 28 of the tube 54. The passageways 66 are equi-angularly spaced around that axis 28.

(18) As shown on the lower side of the tube 54 in FIG. 3, each passageway 68 accommodates a long bolt, stud or threaded rod 70. The rod 70 protrudes longitudinally beyond the proximal face of the shoulder 66 and the distal face of the tensioning flange 64. The rod 70 is then secured and tensioned by lightening nuts 72 on its protruding ends.

(19) There a radial clearance between each rod 70 and the surrounding walls of the associated passageway 68. This clearance is sufficient for the sleeve 60 and the wedge system 58 to move slightly in opposed radial directions with their wedging interaction as they are pulled together by the tensioned rod 70. Thus, due to tension in the rod 70, the sleeve 60 forces the wedge system 58 radially inwardly against the radially outer surface of the tube 54 to squeeze the wall of the tube 54 against the root portion 62 of the stem 56 within. This locks the end fitting 50 to the tube 54 like the prior art arrangement shown in FIG. 2.

(20) It will be evident from FIG. 3 that as the rods 70 act longitudinally in tension, they can extend longitudinally through the tensioning flange 64. This keeps the locking system, compactly, within the outer diameter of the tensioning flange 64 and so avoids adding to the overall diameter of the end fitting 50, unlike the bolts 48 extending through the end ring 46 of the prior art arrangement of FIG. 2.

(21) Elongate elements other than rods 70 may act longitudinally in tension to lock the sleeve 60 around the wedge system 56. For example, straps 74 equi-angularly spaced around the central longitudinal axis 28 of the tube 54 could be used instead, as in the end fitting 76 that is shown in FIG. 4 as a second embodiment of the invention. Here, like numerals are used for like features.

(22) In the end fitting 76 of FIG. 4, the tensioning flange 64 of FIG. 3 is replaced by a support flange 78 that supports and guides the looped straps 74 to hold the straps 74 clear of the wedge system 58. The thin, flat section of the straps 74 makes it possible for the straps 74 to extend around the radially outer side of the support flange 78 without adding substantially to the outer diameter of the end fitting 78.

(23) To enable this, opposed ends of each strap 74 are attached, respectively, to the sleeve 60 and to the part of the stem 58 that protrudes distally from the tube 54. In this example, a distal end of the strap 74 is looped around an anchor formation 80 on the stem 56, on a distal side of the support flange 78. The anchor formation 80 lies within the radial extent of the support flange 78.

(24) Conversely, a proximal end of the strap 74 is engaged with a tensioner 82 that is attached to the sleeve 60. More specifically, the tensioner 82 is received in a bore 84 that extends through a shoulder 66 at the proximal end of the sleeve 60, as shown on the upper side of the tube 54 in FIG. 4.

(25) The tensioner 62 comprises a threaded rod 86 that has an anchor formation 68 at its distal end for engaging the looped proximal end of the strap 74. The strap 74 is tensioned by tightening a nut 90 at the proximal end of the rod 86, which protrudes proximally beyond the shoulder 66.

(26) It would be possible for a tensioner 82 to be at the distal end of the strap 74 instead of at the proximal end of the strap 74 or indeed to be at an intermediate location along the strap 744. However, positioning the tensioner 82 at or near to a proximal end of the strap 74 is advantageously compact because the proximally-tapering outer shape of the sleeve 60 accommodates the tensioner 82 without increasing the overall diameter of the end fitting 78.

(27) In another variant of the second embodiment, the straps 74 could extend along passageways through the support flange 78, the wedge system 58 and the sleeve 60, like the passageways 68 shown in FIG. 3. In another variant, the support flange 78 could be omitted from the arrangement shown in FIG. 4.

(28) Moving on now to the third and fourth embodiments of the invention shown in FIGS. 5 and 6, these embodiments show how the tensioning and locking principles of the first and second embodiments may be applied to joint fittings 92, 94 respectively. The joint fittings 92, 94 lie between successive composite tubes 54 of a pipeline to effect mechanical and fluid coupling between them. Again, like numerals are used for like features.

(29) As the joint fittings 92, 94 shown in FIGS. 5 and 6 define the joint between the adjoining tubes 54, there is no need for a specific joint formation such as a weld neck, a thread or the coupling flange as shown in FIG. 2. Instead, a tubular stem 96 extends continuously between the adjoining tubes 54 and defines mutually-opposed root portions that are an interference fit within the mutually-opposed end portions of the respective tubes 54. Again, the stem 96 may be sealed to the surrounding tubes 54 by a series of circumferential gaskets like those shown in FIG. 2, although such gaskets have been omitted from FIGS. 5 and 6.

(30) The end portion of each tube 54 is surrounded by a respective wedge system 58 and sleeve 60. The wedge systems 58 and sleeves 60 of the adjoining tubes 54 are in mirrored relation about the interface between the tubes 54.

(31) It will be apparent that the wedge system 58 and sleeve 60 of FIG. 5 correspond to the same features in FIG. 3. Similarly, the wedge system 56 and sleeve 60 of FIG. 6 correspond to the same features in FIG. 4.

(32) The joint fittings 92, 94 shown in FIGS. 5 and 6 also have a flange 98 that extends radially from the stem 96 at a longitudinally-intermediate location. The flange 98 lies between the mutually-opposed ends of the respective tubes 54, which bear against and sandwich the flange 98 between them. The flange 96 also lies between the mirrored wedge systems 58 of the respective tubes 54.

(33) FIG. 5 shows two variants of the third embodiment, one on the upper side of the tubes 54 and one on the lower side of the tubes 54. Both variants effect wedging interaction and looking between the wedge systems 58 and the surrounding sleeves 80 by virtue of threaded rods 100, 102 that act longitudinally in tension. Like the rods 70 of FIG. 3, the rods 100, 102 extend through passageways defined by aligned bores in the wedge system 58, the sleeve 60 and the flange 98.

(34) In the variant shown on the upper side of FIG. 5, separate rods 100 are engaged in opposed threaded blind holes in the flange 98. The flange 98 therefore acts like the tensioning flange 64 of FIG. 3, reacting against tensile forces in the rods 100 that pull the mirrored sleeves 60 toward each other over the respective wedge systems 58.

(35) In the variant shown on the lower side of FIG. 5, a single rod 102 extends through a through-hole in the flange 98 to cooperate with the sleeves 60 on both sides of the flange 98. Thus, the passageways in the mirrored wedge systems 58 and sleeves 60 align with each other and with the through-hole in the flange 98, which simply supports the middle of the rod 102. In principle, it may be possible to omit the flange 98 in this variant if the rod 102 and the opposed wedge systems 58 may be supported adequately without it.

(36) Turning finally to the fourth embodiment shown in FIG. 6, this shows how wedging interaction and locking between the mirrored wedge systems 58 and the surrounding sleeves 60 is effected by straps 104 that act longitudinally in tension like the straps 74 of FIG. 4. Unlike the straps 74 of FIG. 4, however, the straps 104 extend around the flange 98 to cooperate with the sleeves 60 on both sides of the flange 98.

(37) Thus, both ends of the straps 104 are engaged with tensioners 82 like those shown in FIG. 4, which are similarly anchored to the shoulders 66 of the sleeves 60 for tightening and tensioning the straps 104.

(38) Again, in principle, the straps 104 could extend through longitudinal passageways defined by aligned bores in the flange 98, the wedge systems 58 and the sleeves 60. However, the flange 98 could be omitted from the fourth embodiment if the straps 104 and the opposed wedge systems 58 may be supported adequately without it. Also, it would be possible to tension the straps 104 using a tensioner 82 at only one end, the other end simply being anchored directly to the associated sleeve 60. Alternatively, a tensioner 82 could be disposed centrally on a strap 104 with the ends of the strap 104 both being anchored directly to the respective sleeves 60.

(39) In addition to the variants set out above, any other variations are possible within the inventive concept. For example, end fittings or joint fittings of the invention may be made of various materials such as carbon steel, Super Duplex stainless steel or Inconel. Also, straps could be tensioned by a separate tensioning apparatus, in which case the straps may include fastenings that hold the straps locked in a tensioned state.

(40) It would also be possible for the wall of the tube to be shaped to perform the function of the wedge system that serves as an inner wedge formation, thus having distally-flared shape that provides for wedging interaction with the surrounding sleeve, in effect, this integrates the wedge system with the tube, Such a shape may be formed integrally by locally thickening the wall of the tube to increase its outer diameter progressively, or could instead be defined by a frosto-conical part fixed to the tube. An example of such an arrangement, in which the wedge system is integrated with the tube, is shown in FIG. 7. Aside from the integrated wedge system, the arrangement shoown in FIG. 7 is otherwise identical to the arrangement shown in FIG. 3.