Unbonded flexible pipe

Abstract

The invention relates to an unbonded flexible pipe with a longitudinal axis and which comprises from inside outwards a carcass formed by metal windings with gaps between neighboring windings, at least one covering tape and an inner sealing sheath of a polymer extruded onto the covering tape. The covering tape is helically wound with a winding direction defining a tape length direction and a tape width direction perpendicular to the tape length direction. The covering tape comprises lengthwise continuous filament yarns arranged in the tape length direction of the covering tape. The covering tape has a thickness direction perpendicular to the tape length direction. The warp yarns have a thickness determined in the thickness direction of the covering tape of about 100 μm or less, such as of about 50 μm or less, such as from about 5 to about 25 μm.

Claims

1. An unbonded flexible pipe having a longitudinal axis and comprising from inside outwards a carcass formed by metal windings with gaps between neighbouring windings, at least one covering tape and an inner sealing sheath of a polymer extruded onto the covering tape, wherein the covering tape is helically wound with a winding direction defining a tape length direction and a tape width direction perpendicular to the tape length direction, the covering tape comprises lengthwise continuous filament yarns (warp yarns) arranged in the tape length direction of the covering tape, said covering tape has a thickness direction perpendicular to the tape length direction and the tape width direction, said warp yarns have a thickness determined in the thickness direction of the covering tape of about 100 μm or less.

2. The unbonded flexible pipe of claim 1, wherein the warp yarns have a coarseness of about 500 tex (g/km) or less.

3. The unbonded flexible pipe of claim 1, wherein the warp yarns comprise twisted bundles of filaments.

4. The unbonded flexible pipe of claim 1, wherein the warp yarns comprises untwisted bundles of filaments.

5. The unbonded flexible pipe of claim 1, wherein the warp yarns comprise filaments with a thickness of from about 1 to about 30 μm.

6. The unbonded flexible pipe of claim 1, wherein the warp yarns comprise filaments with a coarseness of about 200 tex or less.

7. The unbonded flexible pipe of claim 1, wherein the warp yarns are woven with crossing weft yarns, suitable arranged with an angle of from about 35 degrees to about 165 degrees to the warp yarns.

8. The unbonded flexible pipe of claim 1, wherein the warp yarns are woven with crossing weft yarns, the weft yarns are continuous weft yarns, having a thickness determined in the thickness direction of the covering tape of 100 μm or less.

9. The unbonded flexible pipe of claim 1, wherein the warp yarns are woven with crossing weft yarns, the weft yarns comprise filaments with a thickness of from about 1 to about 30 μm.

10. The unbonded flexible pipe of claim 1, wherein the warp yarns are woven with crossing weft yarns, the weft yarns comprise filaments with a coarseness of about 500 tex (g/km) or less.

11. The unbonded flexible pipe of claim 1, wherein the warp yarns are woven with crossing weft yarns, the warp yarns have a coarseness which is at least as high as the coarseness of the weft yarns.

12. The unbonded flexible pipe of claim 1, wherein the warp yarns are woven with crossing weft yarns, the warp yarns have a coarseness which is higher than the coarseness of the weft yarns, and at least about 10 tex higher than the coarseness of the weft yarns.

13. The unbonded flexible pipe of claim 1, wherein the covering tape comprises per 5 cm.sup.2 (determined as 5 cm in length direction×5 cm in width direction) a number of warp yarns and a number of weft yarns, wherein the number of warp yarns is larger than the number of weft yarns.

14. The unbonded flexible pipe of claim 1, wherein the covering tape comprises per 5 cm.sup.2 (determined as 5 cm in length direction×5 cm in width direction) a number of warp yarns and a number of weft yarns, wherein the number of warp yarns is from about 20 to about 100 and the number of weft yarns is from about 5 to about 50.

15. The unbonded flexible pipe of claim 1, wherein the warp yarns are woven with crossing weft yarns, the warp yarns and/or the weft yarns are impregnated with a thermoplastic resin, the thermoplastic resin impregnating the warp yarns and/or the weft yarns has a melting point of about 200° C. or less.

16. The unbonded flexible pipe of claim 1, wherein the covering tape has a longitudinal tensile strength in its length direction and a width tensile strength in its width direction, wherein its longitudinal tensile strength is higher than the width tensile strength.

17. The unbonded flexible pipe of claim 1, wherein the covering tape has a longitudinal tensile strength in its length direction and a width tensile strength in its width direction, the longitudinal tensile strength is at least about 500 N/5 cm.

18. The unbonded flexible pipe of claim 1, wherein the covering tape has a longitudinal tensile strength in its length direction and a width tensile strength in its width direction, the width tensile strength is up to about 2500 N/5 cm.

19. The unbonded flexible pipe of claim 1, wherein the covering tape is helically wound with an angle to the longitudinal axis of the pipe of about 40 degree or more.

20. The unbonded flexible pipe of claim 1, wherein the pipe comprises a plurality of covering tapes wound upon each other between the carcass and the inner sealing sheath, comprising at least 3 covering tapes.

21. The unbonded flexible pipe of claim 3, wherein the twisted bundles of filaments are impregnated with a resin.

22. The unbonded flexible pipe of claim 4, wherein the untwisted bundles of filaments are impregnated with a resin.

Description

BRIEF DESCRIPTION OF DRAWINGS AND EXAMPLES

(1) The invention will be explained more fully below in connection with a preferred embodiment and with reference to the drawings in which:

(2) FIG. 1 is a schematic side view of an unbonded flexible pipe of the invention.

(3) FIG. 2 is a schematic side view of another unbonded flexible pipe of the invention.

(4) The figures are schematic and simplified for clarity and they show only details which are essential to the understanding of the invention, while other details are left out. Throughout the same reference numerals are used for identical or corresponding parts.

(5) The flexible pipe shown in FIG. 1 comprises from inside and out a carcass 2, a helically wound covering tape 3, an inner sealing sheath 5, a pressure armor layer 4, two cross wound tensile armor layers 7a, 7b and an outer sheath 1.

(6) Whereas the unbonded flexible pipe of the invention must have the carcass 2, the helically wound covering tape 3 and the inner sealing sheath 5, the layers on the outer side of the inner sealing sheath 5 are not necessarily required and one or more of these layers may be omitted. In the same way the unbonded flexible pipe may have further layers as described above.

(7) The inner sealing sheath 5 is advantageously of poly ethylene (HDPE), cross linked polyethylene (PEX), Polyvinyldifluorid (PVDF) or polyamide (PA) and has the purpose of preventing outflow of the fluid transferred in the bore of the pipe, indicated with the arrow. The carcass 2 is normally of metal and has the main purpose of reinforcing the pipe against collapse. The carcass 6 is not liquid tight. The helically wound covering tape 3 is as described above. As shown the helically wound covering tape 3 is helically wound with a relatively low winding angle to the longitudinal axis of the unbonded flexible pipe as indicated with the reference number 6.

(8) The pressure armor layer 4 is often of helically wound armor element(s) of metal or composite material or combinations, which is wound with an angle to the axis of the pipe of about 65 degrees or more e. g. about 85 degrees. The pressure armor layer 4 is not liquid tight.

(9) The cross wound tensile armor layers 7a, 7b are wound from elongate armor elements. The two armor layers with opposite winding directions are normally referred to as being cross wound. The outer sheath 1 can be a liquid tight outer sealing sheath protecting the armor layer mechanically and protect against ingress of sea water or it can be a liquid pervious outer sheath merely providing mechanical protection. Where the outer sheath 1 is liquid pervious it is often desired that the unbonded flexible pipe comprises an intermediate sealing sheath covering the pressure armor layer 4, in particular where the pressure armor layer 4 is of or comprises metal. The unbonded flexible pipe advantageously comprises anti-friction layers between the armor layers 4, 7a, 7b. The anti-friction layers are usually not liquid tight and may for example be in the form of a wound tape.

(10) FIG. 2 shows a variation of the flexible armored pipe shown in FIG. 1 comprising from inside and out a carcass 12, a helically wound covering tape 13, an inner sealing sheath 15, a pressure armor layer 14, two cross wound tensile armor layers 17a, 17b and an outer sheath 11. The helically wound covering tape 13 is helically wound with a relatively high winding angle to the longitudinal axis of the unbonded flexible pipe as indicated with the reference number 16.

EXAMPLE

Example 1

(11) An unbonded flexible pipe with an inner diameter of about 20 cm and comprising a plurality of layers is prepared. The layers of the unbonded flexible pipe are as shown in table 1 in the listed order from inside and out of the unbonded flexible pipe.

(12) TABLE-US-00001 TABLE 1 A carcass The carcass is made from strips of a steel. The strips are folded and interlocked as shown in “Recommended Practice for Flexible Pipe”, ANSI/API 17 B, fourth Edition, July 2008, FIG. 7, e). The Steel is stainless steel is Nicrofer ® marketed by ThyssenKrupp VDM Gmbh A covering layer The covering layer is provided by 3 layers of helically wound covering tapes (winding degree is 55; overlap is 15 cm), with a width of 40 cm and a thickness of 0.1 mm. The covering tapes comprise warp yarns and perpendicular weft yarns of basalt filaments impregnated with polyethylene. An inner sealing The inner sealing sheath is an extruded sheath polyvinylidene difluoride, Solef ® PVDF with a thickness of about 6 mm. A pressure armor The pressure armor is provided by helically wound layer and interlocked, elongate C shaped profiles of carbon steel. An anti-friction The anti-friction layer is provided by thin, helically layer wound polymer tapes. A first tensile The first tensile armor layer is provided by helically armor layer wound wires of carbon steel. An anti-friction The anti-friction layer is provided by thin, helically layer wound polymer tapes. A second tensile The second tensile armor layer is provided by armor layer helically wound wires of carbon steel. A holding tape The anti-friction layer (anti-bird-cage layer) is of helically wound aramide fibers with a high winding degree >80 to the longitudinal axis. An outer sheath The outer sheath is a liquid impermeable extruded layer of polyamide PA11 with a thickness of about 6 mm.

Example 2

(13) As example 1, but where the covering layer is provided by 4 layers of helically wound covering tapes (winding degree is 40; overlap is 25 cm), with a width of 50 cm and a thickness of 0.09 mm. The covering tapes comprise warp yarns and weft yarns of thermoset polyester filaments impregnated with thermoplastic polyester. The weft yarns have an angle of 75 degrees to the warp yarns.

Example 3

(14) As example 1, but where the covering layer is provided by 4 layers of helically wound covering tapes (winding degree is 50; overlap is 20 cm), with a width of 50 cm and a thickness of 0.08 mm. The covering tapes comprise warp yarns of carbon filaments impregnated with polypropylene and weft yarns of aramide filaments impregnated polypropylene. The weft yarns have an angle of 45 degrees to the warp yarns.

(15) Some preferred embodiments have been shown in the foregoing, but it should be stressed that the invention is not limited to these, but may be embodied in other ways within the subject-matter defined in the following claims.