Assembly of an end-fitting and an unbonded flexible pipe

Abstract

An end-fitting and an unbonded flexible pipe, where the unbonded flexible pipe includes from the inside and out an internal pressure sheath, at least one armor layer and an outer sheath, the end-fitting further includes a sealing element. The sealing element includes a seal casing concentrically arranged around the internal pressure sheath, the seal casing includes a recess in which a first sealing element is concentrically arranged around the internal pressure sheath such that the surface of the first sealing element at least forms a line contact with the internal pressure sheath, and a second sealing element is concentrically arranged around the internal pressure sheath in the recess such that the surface of the second sealing element at least form a line contact with the surface of the seal casing and form a line contact with the surface of the first sealing element.

Claims

1. An assembly of an end-fitting and an unbonded flexible pipe, said unbonded flexible pipe comprises from the inside and out an internal pressure sheath, at least one armor layer and an outer sheath, said layers of the flexible pipe being terminated in said end-fitting, and said end-fitting further comprises a sealing arrangement, wherein said sealing arrangement comprises a seal casing concentrically arranged around the internal pressure sheath, said seal casing comprises a recess in which at least a first ring shaped sealing element is concentrically arranged around the internal pressure sheath to provide that the surface of the first ring shaped sealing element forms at least a line contact with the internal pressure sheath, and a second ring shaped sealing element is concentrically arranged around the internal pressure sheath in said recess to provide that the surface of the second ring shaped sealing element forms at least a line contact with the surface of the seal casing and forms a line contact with the surface of the first ring shaped sealing element and wherein the hardness of the first ring shaped sealing element is different from the hardness of the second ring shaped sealing element; and the Shore D hardness of the first ring shaped sealing element is in the range of 40 to 70 measured according to ASTM 2240; and the Shore A hardness of the second ring shaped sealing element is in the range of 80 IRHD to 100 IRHD measured according to ISO 48N.

2. An assembly according to claim 1, wherein the second ring shaped sealing element has a higher elastic strain limit than the first ring shaped sealing element.

3. An assembly according to claim 1, wherein the seal casing comprises a third ring shaped sealing element concentrically arranged around the internal pressure sheath in said recess to provide that the surface of the third ring shaped sealing element forms at least a line contact with the surface of the seal casing and forms a line contact with the surface of the first ring shaped sealing element.

4. An assembly according to claim 3, wherein third ring shaped sealing element corresponds to the second ring shaped sealing element.

5. An assembly according to claim 1, wherein the surface of the first ring shaped sealing element comprises a groove concentrically arranged around the internal pressure sheath.

6. An assembly according to claim 5, wherein the groove houses a fourth ring shaped sealing element, said fourth ring shaped sealing element forms at least a line contact with the internal pressure sheath and a contact with the surface of the first ring shaped sealing element.

7. An assembly according to claim 1, wherein the Shore D hardness of the first ring shaped sealing element is in the range of 45 to 65 measured according to ASTM 2240.

8. An assembly according to claim 1, wherein the Shore A hardness of the second ring shaped sealing element is in the range of 82 IRHD to 98 IRHD measured according to ISO 48N.

9. An assembly according to claim 1, wherein the second ring shaped sealing element is made from a cross-linked polymer material.

10. An assembly according to claim 9, wherein the first ring shaped sealing element is made from a polymer material, and wherein a degree of crosslinking of the polymer material of the first ring shaped sealing element is at least 10 times lower than the degree of crosslinking of the second ring shaped sealing element.

11. An assembly according to claim 1, wherein the first ring shaped sealing element is made from a thermoplastic polymer material.

12. An assembly according to claim 1, wherein the first ring shaped sealing element is made from a thermoplastic polymer material reinforced with particles, flakes or fibres.

13. An assembly according to claim 1, wherein the first ring shaped sealing element is made from polytetrafluoroethylene (PTFE), thermoplastic elastomer (PTE), perfluoroalkoxy alkane (PFA), poly(fluorenyle ethynylene) (PFE), polyurethane (PU), ultra high molecular weight polyethylene (UHMWPE) or polyetheretherketone (PEEK).

14. An assembly according to claim 1, wherein the second ring shaped sealing element is made from one or more elastomers as defined by ASTM D1418.

15. An assembly according to claim 1, wherein at least one of the first ring shaped sealing element and the second ring shaped sealing element is made from fluoro-containing polymer material.

16. An assembly according to claim 1, wherein the recess in the seal casing has a rectangular cross-section.

17. An assembly according to claim 1, wherein the seal casing has a substantially U-shaped cross-section.

18. A method of applying a seal casing in an assembly of an end-fitting and an unbonded flexible pipe, where said unbonded flexible pipe comprises from the inside and out an internal pressure sheath, at least one armor layer and an outer sheath, said layers of the flexible pipe being terminated in said end-fitting, wherein the seal casing is arranged concentrically around the internal pressure sheath, said seal casing comprises a recess in which at least a first ring shaped sealing element is concentrically arranged around the internal pressure sheath such that the surface of the first ring shaped sealing element is arranged to form at least a line contact with the internal pressure sheath, and a second ring shaped sealing element is arranged concentrically around the internal pressure sheath in said recess to provide that the surface of the second ring shaped sealing element forms at least a line contact with the surface of the seal casing and form a line contact with the surface of the first ring shaped sealing element and wherein the hardness of the first ring shaped sealing element is different from the hardness of the second ring shaped sealing element; and the Shore D hardness of the first ring shaped sealing element is in the range of 40 to 70 measured according to ASTM 2240; and the Shore A hardness of the second ring shaped sealing element is in the range of 80 IRHD to 100 IRHD measured according to ISO 48N.

19. The method according to claim 18, wherein the first ring shaped sealing element and/or the second ring shaped sealing element is/are manufactured from fluoro-containing polymer material.

Description

DETAILED DESCRIPTION OF THE INVENTION

(1) The invention will now be described in further details with reference to embodiments shown in the drawing in which:

(2) FIG. 1 shows an assembly of an end-fitting and a pipe;

(3) FIG. 2 shows a cross section of an assembly according to the invention;

(4) FIG. 3 shows further details of the seal casing;

(5) FIG. 4 shows an embodiment of the seal casing;

(6) FIG. 5 shows an embodiment of the seal casing;

(7) FIG. 6 shows an embodiment of the seal casing;

(8) FIG. 7 shows an embodiment of the seal casing; and

(9) FIG. 8 shows an embodiment of the seal casing.

(10) The figures are not accurate in every detail but only sketches intended to show the principles of the invention. Details which are not a part of the invention may have been omitted. In the figures the same reference numbers are used for the same parts.

(11) FIG. 1 illustrates an assembly 1 comprising an end-fitting 2 and an unbonded flexible pipe 3.

(12) The end-fitting 2 comprises a body part 4, a channel 5 and a flange 6 for connection to a connector or another end-fitting. The flange 6 comprises holes 7 for bolts which may be used for connecting the end-fitting to other equipment.

(13) The unbonded flexible pipe 3 comprises, from the inside and out, a carcass 10, an internal pressure sheath 11, a tensile armour 12 and an outer sheath 13. The internal pressure sheath 11 is made from polyethylene and the outer sheath 13 is made from polyamide. The carcass 10 is made from stainless steel and the tensile armor 12 is made from carbon steel.

(14) FIG. 2 shows a cross section of the assembly of FIG. 1. As it can be seen the end-fitting 2 comprises an inner casing 21 and an outer casing 22. The layers of the flexible pipe are terminated in the end-fitting. The carcass 10 is terminated by means of a carcass ring 24. The internal pressure sheath 11 is attached to the end-fitting by attachment means 25 and a sealing is provided by the seal casing 30. The tensile armor 12 is terminated in fixation chamber and fixed by means of epoxy.

(15) The outer sheath 13 is attached to the outer casing 22 of the end-fitting.

(16) It should be understood that the FIGS. 1 and 2 shows a rather simple configuration of an assemble of an end-fitting and an unbonded flexible pipe. An unbonded flexible pipe may comprise several layers, such as from the inside and out a carcass, an internal pressure sheath, one or two pressure armors, one or two tensile armors and an outer sheath.

(17) In FIGS. 1 and 2 a simpler configuration has been chosen to emphasize the invention.

(18) FIG. 3 shows details of the seal casing 30 mounted in the end-fitting 2. The seal casing 30 comprises a recess 31 in which a first sealing element 41 and a second sealing element 42 are located. The recess 31 provides the seal casing 30 with a substantially U-shaped cross-section. The seal casing 30 is attached to the end-fitting by bolt 32. In the interface 33 between the end-fitting 2 and seal casing 30 a seal ring 34 is provided.

(19) The seal casing 30 and the sealing elements 41, 42 are ring shaped to be concentric around the internal pressure sheath 11, i.e. they share the same centre axis. The seal casing 30 is contacting the internal pressure sheath 11 without providing any substantial pressure on the internal pressure sheath 11.

(20) FIG. 4 shows an embodiment of the seal casing 30 comprising a first sealing element 41 and a second sealing element 42 in the recess 31.

(21) FIG. 4 illustrates the seal casing 30 in loaded condition, i.e. in a situation where the sealing elements are “energized”. In FIG. 1 a fluid with high pressure is present on the A-side of the seal casing 30 and a fluid with lower pressure is present on the B-side of the seal casing 30.

(22) This has the effect that the sealing elements 41 and 42 are pressed towards the B-side of the recess 31. Moreover, a line contact 51 is formed between the internal pressure sheath 11 and the first sealing element 41. A line contact 52 is also formed between the first sealing element 41 and the second sealing element 42. The second sealing element 42 has a line contact 53 with the surface of the seal casing 30. The second sealing element 42 also has a line contact 53b with the surface of the seal casing 30 at the B-side of the seal casing.

(23) In this particular situation the first sealing element also have a line contact 53a with the surface of the seal casing 30 at the B-side of the seal casing.

(24) As seen, the passage from the A-side to the B-side of the seal casing is efficiently blocked by the energized sealing elements.

(25) FIG. 5 in principle shows the same embodiment, but here the pressure of the fluid on the B-side is higher than the pressure of the fluid on the A-side of the seal casing 30. Thus, the first sealing element 41 and the second sealing element 42 forms line contact with the surface of the seal casing 30 in the recess 31 at the B-side.

(26) The embodiment of FIG. 6 in principle corresponds to the embodiments in FIGS. 4 and 5. However, the first sealing element 41 is provided with a groove in the surface with line contact 51 with the internal pressure sheath 11. The groove 45 may provide improved sealing properties of the first sealing element 41. The embodiment of FIG. 6 is in unloaded condition, i.e. the sealing elements are not energized.

(27) In the embodiment of FIG. 7 the seal casing 30 comprised a third sealing element 43. The third sealing element is placed in the recess 31 in side-to-side configuration with the second sealing element 42, both on top of the first sealing element 41. This embodiment may also improve the sealing properties of the seal casing.

(28) The embodiment of the seal casing 30 shown in FIG. 8 substantially corresponds to the embodiment seen in FIG. 7. The difference between the embodiments is that in FIG. 8 the first sealing element 41 comprises a groove 45 in the surface with line contact 51 with the internal pressure sheath 11. In the groove 45 is mounted a fourth sealing element 44.

(29) The fourth sealing element 44 is preferably made from the same material as the second sealing element 42 and the third sealing element 43.

(30) The embodiment of FIG. 8 also provides excellent sealing properties.

EXAMPLE

(31) A sealing device corresponding to the sealing device shown in FIG. 8 is provided.

(32) The dimensions of the sealing elements are approximately as follows:

(33) The first ring shaped element: cross-section 2.0 cm×1.5 cm

(34) The second ring shaped element: diameter 0.9 cm

(35) The third ring shaped element: diameter 0.9 cm

(36) The fourth ring shaped element: diameter 0.4 cm

(37) The sealing elements are mounted in an end-fitting in a seal casing made from stainless steel and having a recess with dimensions being approximately 2.0 cm×2.2 cm.

(38) The seal casing is adapted to seal around an internal pressure sheath terminated in the end-fitting and having an outer diameter 24 cm. The internal pressure sheath is manufactured from polyethylene, and attached in the end-fitting by conventional attachment means.

(39) The material for the first sealing element is a PTFE having the properties as shown in table 1.

(40) TABLE-US-00001 TABLE 1 Properties of PTFE Property Value Test method Hardness Shore D ~50 ASTM D2240 Specific gravity ~2.13 g/cm.sup.3 ASTM D7922240 Tensile strength ~30 MPa ASTM D4894 Elongation at break ~350% ASTM D4894

(41) In respect of the second sealing element, the third sealing element and fourth sealing element, the same material is chosen. The material is a FKM elastomer having the properties shown in table 2.

(42) TABLE-US-00002 TABLE 2 Properties of FKM elastomer Property Value Test method Hardness Shore A ~90 IRHD ISO 48N Specific gravity ~1.82 g/cm.sup.3 ISO 2781 Tensile strength ~15 MPa ISO 37 Elongation at break ~100% ISO 37

(43) The end-fitting is tested in a factory test equipment with a fluid (rape seed oil) having a pressure of approx. 100 bar and a temperature of approx. 80° C. No leaks are detected after 30 days in the test equipment.