Intermediate sealing for ultradeep water applications

Abstract

A sealing arrangement and a method for testing the integrity of a sealing arrangement of a flexible pipe are disclosed. The method includes locating a first annular sealing element and a second annular sealing element in a joint between two elements of a flexible pipe, with a region of the joint therebetween; and pressurizing the region between the first sealing element and the second sealing element through a port extending towards the region to a predetermined pressure of 0.2 MP or greater.

Claims

1. A method for testing the integrity of a sealing arrangement of a flexible pipe, comprising: locating a first annular sealing element and a second annular sealing element in a joint between two elements of a flexible pipe, with a region of the joint therebetween; and pressurising the region between the first sealing element and the second sealing element through a port extending towards the region to a predetermined pressure of about 0.2 MPa or greater, and wherein the first and second sealing elements are sealing rings each having a cross-section comprising a wedge-like portion, and wherein the first and second sealing elements are oriented in the same axial direction such that the wedge-like portion of each sealing element faces an open mouth of an end fitting assembly into which an end of a flexible pipe body of the flexible pipe is located.

2. A method as claimed claim 1 wherein the first sealing element has a diameter equal to the second sealing element.

3. A method as claimed in claim 1 wherein the two elements of the flexible pipe are a first collar member and a second collar member.

4. A method as claimed in claim 1 wherein the first and second sealing elements are provided adjacent to and radially outwards of a polymer sealing layer of the flexible pipe body.

5. A method as claimed in claim 1 further comprising the step of energising the first and second sealing elements by urging one or both of the two elements of the flexible pipe towards the other element.

6. A method as claimed in claim 1 wherein the predetermined pressure is about 0.2 to 50 MPa.

7. A method as claimed in claim 1 further comprising locating a third annular sealing element and a fourth annular sealing element in a joint between two elements of a flexible pipe, with a region of the joint therebetween; and pressurising the region between the third sealing element and the fourth sealing element through a port extending towards the region to a predetermined pressure of 5 MPa or greater.

8. An assembly for ensuring the integrity of a sealing arrangement of a flexible pipe, comprising: a first annular sealing element and a second annular sealing element in a joint between two elements of a flexible pipe, with a region of the joint therebetween; and a port extending towards a region between the first sealing element and the second sealing element for pressurising the region between the first sealing element and the second sealing element, wherein the first and second sealing elements are sealing rings each having a cross-section comprising a wedge-like portion, and wherein the first and second sealing elements are oriented in the same axial direction such that the wedge-like portion of each sealing element faces an open mouth of an end fitting assembly into which an end of a flexible pipe body of the flexible pipe is located.

9. An assembly as claimed in claim 8 wherein the first and second sealing elements are swaged into position.

10. An assembly as claimed in claim 8 wherein the two elements of the flexible pipe are a first collar member and an end fitting body.

11. An assembly as claimed in claim 8 wherein the two elements of the flexible pipe are a first collar member and a second collar member.

Description

(1) Embodiments of the invention are further described hereinafter with reference to the accompanying drawings, in which:

(2) FIG. 1 illustrates a flexible pipe body;

(3) FIG. 2 illustrates a riser assembly;

(4) FIG. 3 illustrates an end fitting;

(5) FIG. 4 illustrates a variation on the end fitting design;

(6) FIG. 5 illustrates a portion of an end fitting assembly;

(7) FIG. 6 illustrates the portion of FIG. 5 during assembly;

(8) FIG. 7 illustrates the portion of FIG. 5 after further assembly.

(9) In the drawings like reference numerals refer to like parts.

(10) FIG. 5 illustrates a cross-section of a portion of a sealing arrangement of an end fitting. The assembly includes a first collar member 508 and a second collar member 510 provided to terminate an intermediate sealing layer 512 of the pipe body. The intermediate sealing layer may be provided radially outwards of a pressure armour layer 514 and used to seal the pressure armour layer.

(11) The assembly also includes intermediate sealing rings 516, 518 for blocking a potential leak pathway along the radially outer face of the intermediate sealing layer 512 and the first collar member 508. The first sealing ring is provided between the first collar member and the second collar member, and over a portion of the intermediate sealing layer 512. The second sealing ring is provided at an opposite side of the second collar member 510 and over a portion of the intermediate sealing layer 512. As such, in this example the first and second sealing rings have the same diameter (and radius). Between the sealing rings 516, 518 is a test port 524 provided in the second collar member 510, extending as a passageway from a radially outer surface of the second collar member to a radially inner surface of the collar member.

(12) The first and second sealing rings are orientated in the same direction, which assists with their installation and energisation (their energisation is discussed in more detail below). That is, each sealing ring faces the same axial direction (with the wedge-like portion facing to the right in the cross-section of FIG. 5). This allows the two seals to be treated similarly when performing a swaging action on the seals to energise the seals. For example, a single axial motion in one direction may be used to energise both seals. In addition, the same orientation of both seals allows a simple installation technique to be used and provides a more reliable seal as stresses in the polymer barrier layer between the sealing rings during energisation are not acting against the sealing forces.

(13) In addition, the assembly includes two pairs of O-rings 520, 521, 522, 523 to help block a potential leak pathway along the edges of the first collar member 508. The O-rings are coaxial and provided along surfaces 526, 528 of the first collar member 508 that extend around circumferential axes of the flexible pipe. In this example, the O-rings 520 and 521 have the same diameter, and the O-rings 522 and 523 have the same diameter. Between the O-rings 520, 521 is a test port 530 provided in the first collar member 508, extending as a passageway from a radially outer surface of the first collar member to a radially inner surface of the collar member. Between the O-rings 522, 523 is a test port 532 provided in the first collar member 508, extending as a passageway from a radially outer surface of the first collar member to a radially inner surface of the collar member.

(14) To provide a good seal, a sealing ring should be energised by a swaging action. This involves the two adjacent elements, in the case of the sealing ring 516, the first collar member 508 and second collar member 510, being brought together (in either direction or simultaneously) until further movement is restricted. Then, the adjacent elements are brought closer together, which is likely to deform the wedge-like portion of the sealing ring 536 and urge the wedge-like portion into a close sealing configuration with the pipe layer below (intermediate sheath 512). The pipe layer may also deform somewhat.

(15) As shown in FIG. 6, to energise the sealing rings 516, 518, a swaging tool 534 is used, which is forced in a direction from right to left in the figure shown. Of course the collar members could alternatively be forced towards a stationary swaging tool, or all elements urged simultaneously together. This action energises both sealing rings as described above. The swaging tool may then be removed to provide access to the test port 524.

(16) With the sealing rings in place and forming a seal, the test port 524 may be used to test the integrity of the sealing rings. In a testing mode, a fluid (e.g. water or air) may be introduced into the port 524 to pressurise the region between the two sealing rings. The pressure introduced may aptly be 2 MPa, or more. The pressure may be predetermined to simulate the hydrostatic pressure experienced under the sea in use. As such, the fluid may be introduced via port 524 and the fluid pressurised to a level that has been predetermined in accordance with the requirements of use of the pipe in service. Certain arrangements may warrant testing to 5 MPa, or 10 MPa, or 20 MPa, or 30 MPa, or 40 MPa or up to 50 MPa, for example.

(17) With this arrangement, the joints between the sealing rings 516, 518 and the intermediate sealing layer 512 will receive pressurised fluid. Upon reaching a pressurized state, this region should not see a fall in pressure over the test period, due to the first and second sealing rings 516, 518. The region may be pressurised for a predetermined period, for example 5 minutes, or up to 2 hours or more. The period of testing will become less useful if pressure is held for many hours, as fluid may begin to permeate the polymer sheath 512. The pressure of the fluid under pressure is monitored over a test period. If the apparatus gives no indication of a leakage or failure, as signified by a drop in pressure, then the integrity of the seal 516 may be confirmed.

(18) In addition to this test, a similar type of pressure test may be performed to test the pair of O-rings 520,521 using the test port 530. Furthermore, a similar type of pressure test may be performed to test the pair of O-rings 522, 523 using the test port 532. This test on the O-rings effectively provides proof of integrity of those seals not only during the assembly process, but also when the pipe is pressurised, as their location and configuration ensures the performance of the seal is not diminished or lost as a result of the elastic behaviour of threaded fasteners holding a connection together, as would have been the case with previous designs.

(19) Aptly, the O-ring pairs may be tested to a pressure of around 0.2 MPa.

(20) Upon testing of the sealing ring 516 and O-rings 520, 521, 522, 523 with a positive result (i.e. the seals maintain their integrity under the applied pressure), the pressure may be removed, the ports closed, and the flexible pipe construction may be completed ready for use. The sealing ring 518 becomes effectively redundant, its only use being as part of the testing arrangement.

(21) FIG. 7 shows the arrangement after the additional parts of the end fitting have been applied, including an end fitting jacket 538 and a gas venting passageway 540. The remainder of the end fitting arrangement (not shown) may be provided in a known manner.

(22) Various modifications to the detailed designs as described above are possible. For example, rather than a swaging tool, other arrangements may be used to energise the sealing rings. For example, a bolt may be used that is driven into the second collar member towards the first collar member and tightened to a degree that swages the sealing rings.

(23) The sealing arrangement need not be designed to test an intermediate seal. A similar arrangement may be used to test a seal adjacent an outer collar member against an end fitting jacket, for example. Various layers and combinations of layers may be used, depending upon the required conditions of the flexible pipe.

(24) With the above-described arrangement, it is possible to test the reliability of a sealing element to be used in a flexible pipe to be used at great depths under the sea, such as 1000 m or more and/or operating at high pressure. It is particularly useful to be able to have a high degree of confidence in the performance of a sealing element, because it is impossible to replace a faulty sealing element after deployment into the sea without completely re-terminating the pipe, which involves removing the pipe from its in-use location, removing the end fitting including the faulty sealing element, and re-fitting a new end fitting arrangement, before reuse of the pipe is possible.

(25) By forming a chamber between a first and second sealing element, high pressure can be applied to test the integrity of at least one of the sealing elements required, yet without subjecting the remainder of the pipe to that high pressure. As such, the high pressure is applied only at the point of the pipe to be tested.

(26) With the above-described invention, a sealing element may be tested during construction of a flexible pipe to ensure its sealing integrity prior to deployment of the flexible pipe.

(27) For certain flexible pipe body arrangements, it is useful to provide a sealing layer (an intermediate seal) over the pressure armour layer. Then the pressure armour layer and a carcass layer may both be used to give pressure resistance to the pipe. With this invention, it can be assured that the pressure armour layer will not be flooded by hydrostatic pressure from the surrounding sea. As such, the performance of the pressure armour layers can be relied upon as part of the pressure (pipe collapse) resisting layers for ultradeep water applications.

(28) It will be clear to a person skilled in the art that features described in relation to any of the embodiments described above can be applicable interchangeably between the different embodiments. The embodiments described above are examples to illustrate various features of the invention.

(29) Throughout the description and claims of this specification, the words comprise and contain and variations of them mean including but not limited to, and they are not intended to (and do not) exclude other moieties, additives, components, integers or steps. Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

(30) Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

(31) The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.