DK202000911A1

DK202000911A1 - An assembly

Info

Publication number: DK202000911A1
Application number: DKPA202000911A
Authority: DK
Inventors: Glud Thimgaard Jimmi
Original assignee: Glud Thimgaard Jimmi
Priority date: 2020-08-12
Filing date: 2020-08-12
Publication date: 2020-09-02

Abstract

Herein is disclosed an assembly comprising a pipe and a termination end fixed to layers of the pipe. The pipe have a multi-layered permeation barrier arrangement located around an inner sealing layer, an armor layer surrounding the multilayered permeation barrier arrangement and a outer sealing layer surrounding the armor layer. The termination end comprises a sealing means, which comprises a casing concentrically arranged around the multi-layered permeation barrier arrangement, said casing comprises a recess in which at least one sealing element is concentrically arranged around the multi-layered permeation barrier arrangement.

Description

DK 2020 00911 A1 1

AN ASSEMBLY

FIELD OF THE INVENTION The present invention relates to an assembly comprising an end-fitting and an unbonded flexible pipe, where the end-fitting comprises sealing means in connection with a permeation barrier arrangement, said sealing means comprise a seal casing and at least one sealing element.

BACKGROUND OF THE INVENTION A way to safeguard the integrity of unbonded flexible pipes conveying corrosive fluids at elevated pressures and temperatures is by mitigating the permeation of chemically aggressive fluid constituents into the pipe annulus thus preventing the carbon steel armor located in the annulus from being exposed to severe corrosion failure modes, as for example Stress Corrosion Cracking (SCC) failure mode caused by high concentrations of CO2. One permeation mitigating principle is to apply a multi-layered permeation barrier arrangement on the outside of the pressure sheath. However, it has been found that if the multi-layered permeation barrier arrangement is not sealed efficiently in the end fitting, the permeated fluid constituents may circumvent (skip) the multi-layered permeation barrier arrangement by traveling through “gap spirals” formed between wound strip(s) and/or band(s) forming the layers of the multi- layered permeation barrier arrangement and pass into the end fitting and then re- enter the pipe annulus via one or more spiral gap between strip(s) and/or band(s) of an outermost layer of the multi-layered permeation barrier arrangement thus making all the individual, layers including intermediate barrier layers of the multi- layered permeation barrier arrangement ineffective.

OBJECT OF THE INVENTION It is the object of the present invention to provide reliable and cost-effective sealing means in the end-fitting of unbonded flexible pipes, comprising means to reduce the risk of and preferably prevent fluid constituents from entering into the annulus. In an embodiment, it is an object to prevent fluid constituents that has entered into the end-fitting via spiral gaps within a wound, multi-layered permeation

DK 2020 00911 A1 2 barrier arrangement located outside the pressure sheath, from flowing backwards into the pipe annulus via a gab spiral of the multi-layered permeation barrier arrangement, such as via a gap spiral in an outermost layer of the multi-layered permeation barrier arrangement.

In an embodiment, it is an object to prevent fluid constituents from entering into the end-fitting via spiral gaps within a wound, multi-layered permeation barrier arrangement located outside the pressure sheath. The term "spiral gap” is used to mean a spiral shaped gap formed by non-overlapping windings of strip(s)/band(s) of a layer of the multi-layered permeation barrier arrangement. To ensure high flexibility such windings of the strip(s)/band(s) are advantageously helically non- overlapping windings comprising a gap between adjacent windings, which gap will form a spiral shaped gap. This spiral gap is also referred to as a gap spiral groove. In an embodiment, it is an object to provide a robust and reliable mechanical termination of a wound, multi-layered permeation barrier in the end-fitting.

SUMMARY OF THE INVENTION Elements of the invention and embodiments thereof are defined in the claims.

The invention and preferred embodiments will now be described with reference to the examples shown in the figures.

The assembly comprises an unbonded flexible pipe comprising from the inside and out a polymeric pressure sheath (50), at least one armor layer (81, 82, 83) and an outer sheath (90). The pressure sheath (50) and the outer sheath (90) forms an annulus in which at least one or more of the armor layers (81, 82, 83) are located. The pressure sheath (50) defines a bore for transporting of fluids, such as corrosive fluids, e.g. fluids with high concentration of CO.

A multi-layered permeation barrier arrangement (60) is located on the outside of and optionally in contact with the pressure sheath (50). The multi-layered permeation barrier arrangement comprises or consists of alternating stacked layers of wound metallic strips (40) and polymeric bands (30), such as rubber bands and/or polymer bands. Each of the respective layers of the multi-layered permeation barrier arrangement comprises at least one helically wound metallic strip (40) and/or polymeric band (30) and/or a layered combination of metallic

DK 2020 00911 A1 3 strips (40) and/or polymeric bands (30). The multi-layered permeation barrier arrangement is located between the pressure sheath and the one or more armor layers, such as an innermost armor layer.

A galvanic barrier layer (70) may be located between the multi-layered permeation barrier arrangement and the innermost armor layer to separate dissimilar metallic materials e.g. of the armorlayer and the metal strips of the multi-layered permeation barrier arrangement.

Upon pressurizing the flexible pipe bore the alternating stacked strips and bands of the multi-layered permeation barrier arrangement increase their contactpressure and thereby function as a fluid tight barrier preventing permeated fluid constituents from the pipe bore to enter into the area in the pipe annulus containing the armor layer(s). The present permeation barrier sealing solution in the end-fitting comprisesadditional sealing means that comprise a casing (10) concentrically arranged around the multi-layered permeation barrier arrangement (60), said casing comprises a recess in which at least one sealing element (20) is concentrically arranged around the permeation barrier layer such that the inner surface of the at least one sealing element forms at least a line contact with the multi-layeredpermeation barrier arrangement.

Thereby a safe sealing may be provided between an outermost layer of the multi-layered permeation barrier arrangement and the sealing element (20). It should be noted that the assembly may comprise two or more sealing elements and optionally two or more casings.

The line contact preferably extend fully around the circumference of the multi-layered permeationbarrier arrangement.

The sealing element (20) is advantageously of elastomeric and/or thermoplastic material(s). The sealing element(s) may be compressed onto the outermost barrier layer by way of a mechanical arrangement arranged to apply force to thesealing element (20) e.g. via activation means (110), e.g. using bolts.

In a preferred embodiment, the sealing element(s) may be arranged to simultaneously close(s) a gap spiral groove of the outermost layer of the multi-layered permeation barrier arrangement... Thereby, any fluid constituents that have accumulated in the end-fitting are prevented from entering the pipe annulusspace by passing backwards through such gap spiral groove..

DK 2020 00911 A1 4 To mitigate the ingress of fluid constituents into the end-fitting via one or more gap spirals of the multi-layered permeation barrier arrangement e.g. during in- service operation of the pipe, the gap spirals one or more, such in each strip/band layer may be closed/filled with a sealing material 13a, 13b in the end-fitting, as for example using a polymer casting such as epoxy during end fitting assembly. The spiral gap filling material is advantageously characterized by having high mechanical and chemical robustness over time, e.g. low long-term creep and low polymer swelling properties. In an embodiment, the spiral gaps may be closed by inserting “filler strips” of elastomeric and/or thermoplastic material during the end fitting assembly, e.g. PVDF material of 1x2 mm cross-section and 0.5-1.0 m length.

Optionally, the area of the end-fitting in front of the sealing element(s) 20 (i.e. away from the entrance of the pipe into the end-fitting) may be connected to a vent system where any fluid constituents may be released to the surrounding ambient environment via vent ports. Thereby, the build-up of unfavourable pressure within parts of the end fitting structure may be avoided.

Claims

DK 2020 00911 A1 CLAIMS

1. An assembly comprising an end-fitting and an unbonded flexible pipe, said unbonded flexible pipe comprises a plurality of layers comprising an internal 5 pressure sheath, at least one armor layer and an outer sheath, and wherein a multi-layered permeation barrier arrangement is located between the pressure sheath and the at least one armor layer, said multi-layered permeation barrier arrangement comprises alternating stacked layers of wound metallic strips and/or polymeric (e.g. rubber bands and/or polymer bands), said layers of the flexible pipe being terminated and fixed in said end-fitting, and said end-flitting comprises sealing means, wherein said sealing means comprises a casing concentrically arranged around the multi-layered permeation barrier arrangement, said casing comprises a recess in which at least one sealing element is concentrically arranged around the multi-layered permeation barrier arrangement, such that an inner surface of the at least one sealing element at least forms a line contact with the multi-layered permeation barrier arrangement.

2. An assembly according to claim 1, wherein the at least one sealing element is manufactured at least partly from one or more elastomers as defined by ASTM D1418, such as fluoro-elastomer and hydrogenated acrylonitrile butadiene (HNBR).

3. An assembly according to claim 1 or claim 2, wherein the at least one sealing element is manufactured at least partly from a thermoplastic material, such as fluoro-containing polymer material.

4. An assembly according to any one of the preceding claims, wherein the at least one sealing element is manufactured at least partly from a cross-linked polymer material, preferably the degree of crosslinking is at least 50%.

5. An assembly according to any one of the preceding claims, wherein the recess houses at least one elastomeric sealing element and at least one thermoplastic sealing element, said sealing elements form at least a line contact with the permeation barrier layer.

DK 2020 00911 A1 6

6. An assembly according to anyone of the preceding claims, wherein multi- layered permeation barrier arrangement comprises a stepped down section in the end fitting and wherein the sealing means is concentrically arranged around the stepped down section of the multi-layered permeation barrier arrangement, preferably the stepped down section is stepped down by being reduced in number of layers and/or by being reduced in thickness of one or more of the staggered layers relatively to the multi-layered permeation barrier arrangement of the pipe outside the end-fitting.

7. An assembly according to claim 6, wherein the at least one sealing element has at least line contact with two or more of the stacked layers of strips and/or bands simultaneously.

8. An assembly according to anyone of the preceding claims, wherein the Shore A hardness of the sealing element(s), such as the elastomer sealing element(s) is in the range of 40 IRHD to 90 IRHD, such as in the range of 45 IRHD to 80 IRHD, when measured according to ISO 48N.

9. An assembly according to anyone of the preceding claims, wherein the sealing element is fully or partly made from a thermoplastic polymer material reinforced with particles, flakes or fibres.

10. An assembly according to anyone of the preceding claims, wherein the sealing element is manufactured from one or more of polytetrafluoroethylene (PTFE), thermoplastic elastomer (PTE), perfluoroalkoxy alkane (PFA), poly(fluorenyle ethynylene) (PFE), polyurethane (PU), ultra high molecular weight polyethylene (UHMWPE) or polyetheretherketone (PEEK).

11. An assembly according to anyone of the preceding claims, wherein the gap spirals between metal strips and/or between rubber and/or polymer bands in part of the end-fitting are fully or partly filled with a sealing polymer material.

12. An assembly according to anyone of the preceding claims, wherein the gap spirals between metal strips and/or between rubber and/or polymer bands in part ofthe end-fitting are fully or partly filled with an epoxy casting.

DK 2020 00911 A1 7

13. An assembly according to anyone of the preceding claims, wherein the gap spirals between metal strips and between rubber and/or polymer bands in at least a part of the end-fitting are closed with elastomeric or polymeric “filler strips”, such as PVDF filler strips of 1 x 2 mm cross-section and 0.5-1.0 m length.

14. An assembly according to anyone of the preceding claims, wherein the recess in the casing has a substantially rectangular cross-sectional shape.

15. An assembly according to anyone of the preceding claims, wherein the recess in the seal casing has a substantially trapezoid cross-sectional shape.

16. An assembly according to anyone of the preceding claims, wherein the recess in the seal casing has a substantially U-shaped cross-sectional shape.

17. Use of a casing in an assembly of an end-fitting and an unbonded flexible pipe for providing a sealing means, wherein said unbonded flexible pipe comprises from the inside and out an internal pressure sheath, at least one armor layer and an outer sheath, wherein a multi-layered permeation barrier arrangement is located between the pressure sheath and the armor layer, such as an innermost armor layer, wherein the multi-layered permeation barrier arrangement comprises alternating stacked layers of wound metallic strips and/or rubber bands and/or polymer bands, said end-fitting comprises means for terminating said layers of the flexible pipe, and said end-flitting further comprises said sealing means, wherein said sealing means comprises said casing concentrically arranged around the multi-layered permeation barrier arrangement, said casing comprises a recess in which at least one sealing element is concentrically arranged around the multi-layered permeation barrier arrangement, such that an inner surface of the at least one sealing element forms at least a line contact with the permeation barrier layer.