Login| Sign Up| Help| Contact|

Patent Searching and Data


Title:
CARCASS, TAPE AND METHOD OF MANUFACTURE
Document Type and Number:
WIPO Patent Application WO/2019/048823
Kind Code:
A1
Abstract:
Disclosed herein is an elongate tape element that has a cross section comprising a substantially planar region, associated with a primary plane, that extends from a first bent edge region of the cross section. The elongate tape element also has a corrugated region that extends from a respective end region of the planar region to a remaining edge region of the cross section. The corrugated region comprises a first deep corrugation and at least one further deep corrugation.

Inventors:
KIRTON, Peter John (Wellstream House, Wincomblee RoadWalker Riverside, Newcastle upon Tyne Tyne and Wear NE6 3PF, NE6 3PF, GB)
Application Number:
GB2018/052370
Publication Date:
March 14, 2019
Filing Date:
August 21, 2018
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
GE OIL & GAS UK LIMITED (2 High Street, Nailsea, Bristol BS48 1BS, BS48 1BS, GB)
International Classes:
F16L11/08; F16L11/16
Foreign References:
EP0905427A21999-03-31
US6024135A2000-02-15
FR2535010A11984-04-27
US6668867B22003-12-30
Attorney, Agent or Firm:
SECERNA LLP (The Catalyst, Baird Lane Heslington East, York North Yorkshire YO10 5GA, YO10 5GA, GB)
Download PDF:
Claims:
CLAIMS:

1 . An elongate tape element, having a cross section comprising:

a substantially planar region, associated with a primary plane, extending from a first bent edge region of the cross section; and

a corrugated region that extends from a respective end region of the planar region to a remaining edge region of the cross section; wherein

the corrugated region comprises a first deep corrugation and at least one further deep corrugation and the first deep corrugation extends from said a respective end region of the planar region to a peak region, in an imaginary plane that is spaced apart from, and substantially parallel with, the primary plane by a total thickness distance corresponding to a total thickness of said a cross section and back to a position substantially in a further imaginary plane that is parallel to the primary plane and spaced apart from the primary plane by a tape thickness distance corresponding to a thickness of the tape element.

2. The elongate tape element as claimed in claim 1 , further comprising:

said at least one further deep corrugation extends from said a position to a peak region in said imaginary plane and back to a spaced apart position substantially in the further imaginary plane and spaced apart from said a position.

3. The elongate tape element as claimed in claims 1 or 2, further comprising:

said first bent edge region is turned substantially perpendicular to the primary plane and towards a first direction.

4. The elongate tape element as claimed in claim 3, further comprising:

said a remaining edge region is turned substantially perpendicular to the primary plane and in a second direction substantially opposite to the first direction or said a remaining edge region is substantially perpendicular to the primary plane and points in said first direction.

5. The elongate tape element as claimed in any preceding claim, further comprising:

a peak region of the first deep corrugation comprises a flat region or a curved region having an apex.

6. The elongate tape element as claimed in any one of claims 1 to 5, further comprising: a peak region of the further deep corrugation comprises a curved region having an apex.

7. The elongate tape element as claimed in any preceding claim, further comprising:

said first bent edge region comprises a curved portion of the cross section.

8. The elongate tape element as claimed in any one of claims 1 to 6, further comprising:

said first bent edge region comprises a folded dog leg portion of the cross section.

9. The elongate tape element as claimed in any preceding claim, further comprising:

said corrugated region comprises at least four substantially full thickness portions of the cross section that each extend straight in a parallel spaced apart relationship perpendicular to said primary plane.

10. The elongate tape element as claimed in any preceding claim, further comprising:

each deep corrugation extends more than 80% of a total thickness of the cross section.

1 1 . The elongate tape element as claimed in claim 10 wherein each deep corrugation extends more than 95% of the total thickness.

12. The elongate tape element as claimed in any preceding claim, further comprising:

the tape element has a uniform thickness throughout the entire cross section.

13. The elongate tape element as claimed in any preceding claim, further comprising:

the elongate tape element is helically windable and has a cross section whereby adjacent windings are self-interlocking.

14. The elongate tape element as claimed in claim 13, further comprising:

the elongate tape element is windable to form a flexible tubular layer whereby the substantially planar region of each winding is locatable on a radially inner most location and peak regions of the corrugated region of each winding are locatable on a radially outer most location.

15. The elongate tape element as claimed in any preceding claim, further comprising: the further deep corrugation comprises a generally sinusoidal profile.

16. The elongate tape element as claimed in any one of claims 1 to 14, further comprising:

the further deep corrugation comprises a profile including a substantially semicircular peak and spaced apart substantially straight portions each extending from a respective end of the semi-circular peak in a direction substantially perpendicular to the primary plane.

17. The elongate tape element as claimed in any preceding claim, further comprising:

a radius of curvature of a bend between the first bent edge region and the substantially planar region is less than 4t, where t is a uniform thickness of the tape element and where the radius is determined on an outer surface of said a bend.

18. The elongate tape element as claimed in claim 17 wherein the radius of curvature is less than 2t.

19. The elongate tape element as claimed in any preceding claim, further comprising:

a radius of curvature of a further bend between the substantially planar region and the first deep corrugation is less than 4t, where t is a uniform thickness of the tape element and where the radius is determined on an outer surface of said a further bend.

20. The elongate tape element as claimed in claim 19 wherein the radius of curvature is less than 2t.

21 . Flexible pipe body, comprising:

a collapse resistant layer provided by a plurality of self-interlocked windings of an elongate tape element having a cross section comprising a substantially planar region, associated with a primary plane, extending from a first bent edge region of the cross section, and a corrugated region that extends from a respective end region of the planar region to a remaining edge region of the cross section, wherein the corrugated region comprises a first deep corrugation and at least one further deep corrugation and the first deep corrugation extends from said a respective end region of the planar region to a peak region, in an imaginary plane that is spaced apart from, and substantially parallel with, the primary plane by a total thickness distance corresponding to a total thickness of said a cross section and back to a position substantially in a further imaginary plane that is parallel to the primary plane and spaced apart from the primary plane by a tape thickness corresponding to a thickness of the tape element.

22. The flexible pipe body as claimed in claim 21 , further comprising:

said at least one further deep corrugation extends from said a position to a peak region in said imaginary plane and back to a spaced apart position substantially in the further imaginary plane and spaced apart from said a position.

23. The flexible pipe body as claimed in claims 21 or 22, further comprising:

said first bent edge region is turned substantially perpendicular to the primary plane and towards a first direction.

24. The flexible pipe body as claimed in any one of claims 21 to 23, further comprising:

said a remaining edge region is turned substantially perpendicular to the primary plane and in a second direction substantially opposite to the first direction.

25. The flexible pipe body as claimed in any one of claims 21 to 24, further comprising:

a fluid retaining layer over the collapse resistant layer.

26. The flexible pipe body as claimed in claim 25, further comprising:

a pressure armour layer over the fluid retaining layer;

at least one tensile armour layer; and

an outer sheath.

Description:
CARCASS, TAPE AND METHOD OF MANUFACTURE

The present invention relates to a flexible pipe and a windable tape that can be wound to form a carcass layer of the flexible pipe. In particular, but not exclusively, the present invention relates to a carcass layer having a smooth inner surface as well as an increased collapse resistance relative to conventional carcass layers.

Traditionally flexible pipe is utilised to transport production fluids, such as oil and/or gas and/or water, from one location to another. Flexible pipe is particularly useful in connecting a sub-sea location (which may be deep underwater, say 1000 metres or more) to a sea level location. The pipe may have an internal diameter of typically up to around 0.6 metres (e.g. diameters may range from 0.05 m up to 0.6 m). A flexible pipe is generally formed as an assembly of flexible pipe body and one or more end fittings. The pipe body is typically formed as a combination of layered materials that form a pressure-containing conduit. The pipe structure allows large deflections without causing bending stresses that impair the pipe's functionality over its lifetime. There are different types of flexible pipe such as unbonded flexible pipe which is manufactured in accordance with API 17J or composite type flexible pipe or the like. The pipe body is generally built up as a combined structure including polymer layers and/or composite layers and/or metallic layers. For example, pipe body may include polymer and metal layers, or polymer and composite layers, or polymer, metal and composite layers. Layers may be formed from a single piece such as an extruded tube or by helically winding one or more tapes at a desired pitch or by connecting together multiple discrete hoops that are arranged concentrically side-by-side. Depending upon the layers of the flexible pipe used and the type of flexible pipe some of the pipe layers may be bonded together or remain unbonded.

Some flexible pipe has been used for deep water (less than 3,300 feet (1 ,005.84 metres)) and ultra-deep water (greater than 3,300 feet) developments. It is the increasing demand for oil which is causing exploration to occur at greater and greater depths (for example in excess of 8202 feet (2500 metres)) where environmental factors are more extreme. For example in such deep and ultra-deep water environments ocean floor temperature increases the risk of production fluids cooling to a temperature that may lead to pipe blockage. In practice flexible pipe conventionally is designed to perform at operating temperatures of -30°C to +130°C, and is being developed for even more extreme temperatures. Increased depths also increase the pressure associated with the environment in which the flexible pipe must operate. For example, a flexible pipe may be required to operate with external pressures ranging from 0.1 MPa to 30 MPa acting on the pipe. Equally, transporting oil, gas or water may well give rise to high pressures acting on the flexible pipe from within, for example with internal pressures ranging from zero to 140 MPa from bore fluid acting on the pipe. As a result the need for high levels of performance from certain layers such as a pipe carcass or a pressure armour or a tensile armour layer of the flexible pipe body is increased. It is noted for the sake of completeness that flexible pipe may also be used for shallow water applications (for example less than around 500 metres depth) or even for shore (overland) applications. Carcass layers formed from interlocking windings of a variety of elongate tape elements are known. For example US9562633 and US6668867 both disclose carcass layers formed from windings of a respective carcass tape.

A problem faced conventionally is that in order to enable a flexible pipe including a carcass layer (a so-called rough-bore flexible pipe) to flex the carcass windings must be allowed to move with respect to each other to some extent but must not be allowed to become unduly separated. As a result the windings have conventionally had a cross section that produces inset regions or gaps on a radially inner surface. Fluid flowing directly along a bore of the flexible pipe in use interacts with such gaps and this creates the now well-known problem of vortex induced vibration (VIV), or flow induced pulsations (FLIP)

Another problem faced conventionally is that a key function of the carcass layer, that is to say providing crush and/or collapse resistance to the flexible pipe, has been somewhat limited by available conventional carcass winding designs.

It is an aim of the present invention to at least partly mitigate the above-mentioned problems.

It is an aim of certain embodiments of the present invention to provide a carcass layer, and a flexible pipe including such a layer, that is not prone to VIV problems and which also has improved collapse resistance relative to many conventional carcass layer designs.

It is an aim of certain embodiments of the present invention to provide a self-interlocking profile for carcass windings that presents a relatively smooth inner surface when the windings are wound to form a flexible tubular layer for a flexible pipe. - -

It is an aim of certain embodiments of the present invention to provide an elongate tape element that can be wound to form a carcass layer but which can have a uniform thickness that is thicker than is used in many other conventional carcass layers. The extra thickness reduces a risk of parts of the profile pivoting radially inwards in use about a potential fracture point.

It is an aim of certain embodiments of the present invention to provide a carcass layer in which adjacent windings of a carcass tape can move together and apart by a relatively great distance without becoming separated to thereby provide a flexible tubular structure.

It is an aim of certain embodiments of the present invention to provide an elongate tape that can be wound to provide a carcass layer of a rough-bore or flexible pipe whereby the cross section of the tape enables the tape to be wound with less twisting risk than with conventional solutions.

It is an aim of certain embodiments of the present invention to provide an elongate tape that can be wound to provide a carcass layer of a rough-bore flexible pipe whereby the cross section of the tape is uniform meaning that the windable tape itself can be formed from a relatively efficient manufacturing technique from an initially flat strip folded in a number of desired locations. According to a first aspect of the present invention there is provided a substantially planar region, associated with a primary plane, extending from a first bent edge region of the cross section; and a corrugated region that extends from a respective end region of the planar region to a remaining edge region of the cross section; wherein the corrugated region comprises a first deep corrugation and at least one further deep corrugation.

Aptly the first deep corrugation extends from said a respective end region of the planar region to a peak region, in an imaginary plane that is spaced apart from, and substantially parallel with, the primary plane by a total thickness distance corresponding to a total thickness of said a cross section and back to a position substantially in a further imaginary plane that is parallel to the primary plane and spaced apart from the primary plane by a tape thickness distance corresponding to a thickness of the tape element.

Aptly said at least one further deep corrugation extends from said a position to a peak region in said imaginary plane and back to a spaced apart position substantially in the further imaginary plane and spaced apart from said a position. - -

Aptly said first bent edge region is turned substantially perpendicular to the primary plane and towards a first direction.

Aptly said a remaining edge region is turned substantially perpendicular to the primary plane and in a second direction substantially opposite to the first direction or said a remaining edge region is substantially perpendicular to the primary plane and points in said first direction.

Aptly a peak region of the first deep corrugation comprises a flat region or a curved region having an apex.

Aptly a peak region of the further deep corrugation comprises a curved region having an apex.

Aptly said first bent edge region comprises a curved portion of the cross section.

Aptly said first bent edge region comprises a folded dog leg portion of the cross section.

Aptly said corrugated region comprises at least four substantially full thickness portions of the cross section that each extend straight in a parallel spaced apart relationship perpendicular to said primary plane.

Aptly each deep corrugation extends more than 80% of a total thickness of the cross section.

Aptly the elongate tape element as claimed in claim 1 1 wherein each deep corrugation extends more than 95% of the total thickness.

Aptly the tape element has a uniform thickness throughout the entire cross section.

Aptly the elongate tape element is helically windable and has a cross section whereby adjacent windings are self-interlocking.

Aptly the elongate tape element is windable to form a flexible tubular layer whereby the substantially planar region of each winding is locatable on a radially inner most location and peak regions of the corrugated region of each winding are locatable on a radially outer most location. - -

Aptly the further deep corrugation comprises a generally sinusoidal profile.

Aptly the further deep corrugation comprises a profile including a substantially semi-circular peak and spaced apart substantially straight portions each extending from a respective end of the semi-circular peak in a direction substantially perpendicular to the primary plane.

Aptly a radius curvature of a bend between the first bent edge region and the substantially planar region is less than 4t, where t is a uniform thickness of the tape element where the radius is determined on an outer surface of said a bend.

Aptly the elongate tape element as claimed in claim 18 wherein the radius of curvature is less than 2t.

Aptly a radius the substantially planar region and the first deep corrugation is less than 4t, where t is a uniform thickness of the tape element and where the radius is determined on an out surface of said a further bend.

Aptly the elongate tape element as claimed in claim 20 wherein the radius of curvature is less than 2t.

According to a second aspect of the present invention there is provided a collapse resistant layer provided by a plurality of self-interlocked windings of an elongate tape element having a cross section comprising a substantially planar region, associated with a primary plane, extending from a first bent edge region of the cross section, and a corrugated region that extends from a respective end region of the planar region to a remaining edge region of the cross section, wherein the corrugated region comprises a first deep corrugation and at least one further deep corrugation.

Aptly the first deep corrugation extends from said a respective end region of the planar region to a peak region, in an imaginary plane that is spaced apart from, and substantially parallel with, the primary plane by a total thickness distance corresponding to a total thickness of said a cross section and back to a position substantially in a further imaginary plane that is parallel to the primary plane and spaced apart from the primary plane by a tape thickness corresponding to a thickness of the tape element. - -

Aptly said at least one further deep corrugation extends from said a position to a peak region in said imaginary plane and back to a spaced apart position substantially in the further imaginary plane and spaced apart from said a position. Aptly said first bent edge region is turned substantially perpendicular to the primary plane and towards a first direction.

Aptly said a remaining edge region is turned substantially perpendicular to the primary plane and in a second direction substantially opposite to the first direction

Aptly a fluid retaining layer over the collapse resistant layer.

Aptly a pressure armour layer over the fluid retaining layer; at least one tensile armour layer; and an outer sheath.

Certain embodiments of the present invention provide a windable tape that can be helically wound to create a carcass layer for a flexible pipe that provides a high degree of collapse resistance and/or presents a smooth surface for fluid to flow against. Certain embodiments of the present invention provide an increased verticality in carcass windings. That is to say provide an increased number of verticals (portions of the wound tape aligned on a radius of the pipe) per unit width of each carcass winding.

Certain embodiments of the present invention provide a tape element that has a cross section including corrugations to provide collapse resistance and a flat region that extends over and thereby shields, or at least partially fills some or all of the troughs of the corrugations in an adjacent winding when the tape element is wound to form a tubular layer, to thereby prevent those troughs shedding vortices. Certain embodiments of the present invention provide a flexible pipe usable in ultra-deep locations where collapse pressures are highly significant.

Certain embodiments of the present invention provide opportunities to reduce pipe diameter and thus reduce overall mass of a pipe relative to conventional flexible pipe. Certain embodiments of the present invention provide an elongate tape which can be initially formed from a flat strip and merely folded at predetermined locations to produce a profiled elongate tape that can be thereafter wound helically to form a carcass layer for a flexible pipe.

Certain embodiments of the present invention will now be described hereinafter, by way of example only, with reference to the accompanying drawings in which:

Figure 1 illustrates the flexible pipe body;

Figure 2 illustrates uses of a flexible pipe;

Figure 3 illustrates adjacent windings of an elongate tape element forming a carcass layer in a flexible pipe;

Figure 4 illustrates a cross section of the elongate tape element shown in Figure 3 in more detail;

Figure 5 illustrates an alternative embodiment of a carcass layer formed from windings having a different cross section;

Figure 6 illustrates a comparison of two adjacent windings of a conventional carcass tape and two adjacent windings of the elongate tape shown in Figure 5; Figure 7 illustrates a still further alternative embodiment of a tape element having an alternative cross section; and

Figure 8 illustrates a still further alternative embodiment of a tape element that is windable to form a carcass layer.

In the drawings like reference numerals refer to like parts.

Throughout this description, reference will be made to a flexible pipe. It is to be appreciated that certain embodiments of the present invention are applicable to use with a wide variety of flexible pipe. For example certain embodiments of the present invention can be used with respect to flexible pipe and associated end fittings of the type which is manufactured - - according to API 17J. Such flexible pipe is often referred to as unbonded flexible pipe. Other embodiments are associated with other types of flexible pipe.

Turning to Figure 1 it will be understood that the illustrated flexible pipe is an assembly of a portion of pipe body and one or more end fittings (not shown in Figure 1 ) in each of which a respective end of the pipe body is terminated. Figure 1 illustrates how pipe body 100 is formed from a combination of layered materials that form a pressure-containing conduit. As noted above although a number of particular layers are illustrated in Figure 1 , it is to be understood that certain embodiments of the present invention are broadly applicable to coaxial pipe body structures including two or more layers manufactured from a variety of possible materials. The pipe body may include one or more layers comprising composite materials, forming a tubular composite layer. It is to be further noted that the layer thicknesses are shown for illustrative purposes only. As used herein, the term "composite" is used to broadly refer to a material that is formed from two or more different materials, for example a material formed from a matrix material and reinforcement fibres.

A tubular composite layer is thus a layer having a generally tubular shape formed of composite material. Alternatively a tubular composite layer is a layer having a generally tubular shape formed from multiple components one or more of which is formed of a composite material. The layer or any element of the composite layer may be manufactured via an extrusion, pultrusion or deposition process or, by a winding process in which adjacent windings of tape which themselves have a composite structure are consolidated together with adjacent windings. The composite material, regardless of manufacturing technique used, may optionally include a matrix or body of material having a first characteristic in which further elements having different physical characteristics are embedded. That is to say elongate fibres which are aligned to some extent or smaller fibres randomly orientated can be set into a main body or spheres or other regular or irregular shaped particles can be embedded in a matrix material, or a combination of more than one of the above. Aptly the matrix material is a thermoplastic material, aptly the thermoplastic material is polyethylene or polypropylene or nylon or PVC or PVDF or PFA or PEEK or PTFE or alloys of such materials with reinforcing fibres manufactured from one or more of glass, ceramic, basalt, carbon, carbon nanotubes, polyester, nylon, aramid, steel, nickel alloy, titanium alloy, aluminium alloy or the like or fillers manufactured from glass, ceramic, carbon, basalt, metals, buckminsterfullerenes, metal silicates, carbides, carbonates, oxides or the like. - -

The pipe body 100 illustrated in Figure 1 includes an internal pressure sheath 1 10 which acts as a fluid retaining layer and comprises a polymer layer that ensures internal fluid integrity. The layer has an inner surface that provides a boundary for any conveyed fluid. It is to be understood that this layer may itself comprise a number of sub-layers. It will be appreciated that when a carcass layer 120 is utilised the internal pressure sheath is often referred to by those skilled in the art as a barrier layer. In operation without such a carcass (so-called smooth bore operation) the internal pressure sheath may be referred to as a liner. A barrier layer 1 10 is illustrated in Figure 1 . It is noted that a carcass layer 120 is a pressure resistant layer that provides an interlocked construction that can be used as the innermost layer to prevent, totally or partially, collapse of the internal pressure sheath 1 10 due to pipe decompression, external pressure, and tensile armour pressure and mechanical crushing loads. The carcass is thus a collapse resistant layer. It will be appreciated that certain embodiments of the present invention are thus applicable to 'rough bore' applications (with a carcass). Aptly the carcass layer is a metallic layer. Aptly the carcass layer is formed from stainless steel, corrosion resistant nickel alloy or the like. Aptly the carcass layer is formed from a composite, polymer, or other material, or a combination of materials and components. A carcass layer is radially positioned within the barrier layer.

A pressure armour layer 130 is a pressure resistant layer that provides a structural layer that increases the resistance of the flexible pipe to internal and external pressure and mechanical crushing loads. The layer also structurally supports the internal pressure sheath. Aptly as illustrated in Figure 1 the pressure armour layer is formed as a tubular layer. Aptly for unbonded type flexible pipe the pressure armour layer consists of an interlocked construction of wires with a lay angle close to 90°. Aptly the lay angle is between 80° and 90° to the axis of the pipe body. Aptly in this case the pressure armour layer is a metallic layer. Aptly the pressure armour layer is formed from carbon steel, aluminium alloy or the like. Aptly the pressure armour layer is formed from a pultruded composite interlocking layer. Aptly the pressure armour layer is formed from a composite formed by extrusion or pultrusion or deposition or winding, followed by consolidation. A pressure armour layer is positioned radially outside an underlying barrier layer and may be unbonded or bonded to the barrier layer. Bonding with the underlying layer can be achieved through similarity of materials and consolidation or through suitable chemical means. - -

The flexible pipe body also includes a first tensile armour layer 140 and second tensile armour layer 150. Each tensile armour layer is used to sustain tensile loads and optionally also internal pressure. Aptly for some flexible pipes the tensile armour windings are metal (for example steel, stainless steel or titanium or the like). For some composite flexible pipes the tensile armour windings may be polymer composite tape windings (for example provided with either thermoplastic, for instance nylon, matrix composite or thermoset, for instance epoxy, matrix composite). For unbonded flexible pipe the tensile armour layer is typically formed from a plurality of wires. (To impart strength to the layer) that are located over an inner layer and are helically wound along the length of the pipe at a lay angle typically between about 10° to 55°. Aptly the tensile armour layers are counter-wound in pairs. Aptly the tensile armour layers are metallic layers. Aptly the tensile armour layers are formed from carbon steel, stainless steel, titanium alloy, aluminium alloy or the like. Aptly the tensile armour layers are formed from a composite, polymer, or other material, or a combination of materials.

Aptly the flexible pipe body includes optional layers of tape 160, 170, 180 which help contain underlying layers and to some extent prevent abrasion between adjacent layers. The tape layer may optionally be a polymer or composite or a combination of materials, also optionally comprising a tubular composite layer. Tape layers can be used to help prevent metal-to- metal contact to help prevent wear. Tape layers over tensile armours can also help prevent "birdcaging".

The flexible pipe body also includes optional layers of insulation and/or metal winding or polymer layers or tape layers or layers including special materials such as optical fibres and an outer sheath 190, which comprises a polymer layer used to protect the pipe against penetration of seawater and other external environments, corrosion, abrasion and mechanical damage. Any thermal insulation layer helps limit heat loss through the pipe wall to the surrounding environment and may comprise layers of tape or at least one extruded layer of insulating material.

Each flexible pipe comprises at least one portion, referred to as a segment or section, of pipe body 100 together with an end fitting located at at least one end of the flexible pipe. An end fitting provides a mechanical device which forms the transition between the flexible pipe body and a connector. The different pipe layers as shown, for example, in Figure 1 are terminated in the end fitting in such a way as to transfer the load between the flexible pipe and the connector. - -

Figure 2 illustrates a riser assembly 200 suitable for transporting production fluid such as oil and/or gas and/or water from a sub-sea location 221 to a floating facility 222. For example, in Figure 2 the sub-sea location 221 includes a sub-sea flow line 225. The flexible flow line 225 comprises a flexible pipe, wholly or in part, resting on the sea floor 230 or buried below the sea floor and used in a static application. The floating facility may be provided by a platform and/or buoy or, as illustrated in Figure 2, a ship. The riser assembly 200 is provided as a flexible riser, that is to say a flexible pipe 240 connecting the ship to the sea floor installation. The flexible pipe may be in segments of flexible pipe body with connecting end fittings.

It will be appreciated that there are different types of riser, as is well-known by those skilled in the art. Certain embodiments of the present invention may be used with any type of riser, such as a freely suspended (free-hanging, catenary riser), a riser restrained to some extent (buoys, chains), totally restrained riser or enclosed in a tube (I or J tubes). Some, though not all, examples of such configurations can be found in API 17J. Figure 2 also illustrates how portions of flexible pipe can be utilised as a jumper 250.

Figure 3 illustrates a carcass layer 120 juxtaposed with a fluid retaining barrier layer 1 10 according to an embodiment of the present invention. The carcass layer and barrier layer shown are illustrated partly in cross section. The carcass layer is radially inside the barrier layer. As illustrated in Figure 3 the carcass layer 120 is provided by multiple self-interlocking windings of a carcass tape 300. Four adjacent windings 310i, 2, 3, 4 of the carcass windings are shown by way of example in Figure 3. The tape used to provide the carcass layer 120 is a long tape element. This is formed initially from a long flat strip which is folded according to conventional techniques into the cross section illustrated in Figure 3. Other cross sections can be used as discussed below. Because the carcass tape element is initially formed from a flat strip the tape element has a uniform thickness across its cross section.

As illustrated in Figure 3 the elongate tape element that is helically wound to create the carcass layer 120 has a cross section which includes a substantially planar region 320 which extends from a first edge region 330, which is bent, into a corrugated region 340 that extends from an end region of the planar region 320 to a remaining edge region 350 of the cross section. The corrugated region 340 includes a first deep corrugation 360 and a further deep corrugation 370. - -

A deep corrugation is an undulation that extends for a substantial portion of the whole thickness of the carcass layer. Because the structured elements ("verticals") provided by portions of the tape cross section effectively bridge between a radially inner surface of the barrier layer and a cooperating portion of the tape cross section in an adjacent winding, radial forces (caused by collapse forces in use) are withstood well by the cross section profile.

The barrier layer 1 10 is shown formed over the radially outer most surface of the carcass layer 120 which is formed by self-interlocked windings of the elongate tape element. The barrier layer 1 10 is illustrated as having slight bulges 380 which extend slightly into gaps between adjacent peaks provided on the radially outer surface of the carcass layer. The bulges 380 help locate the barrier layer with respect to the carcass layer but do not ingress so far as to provide any inhibition to the sliding ability of adjacent windings of the carcass layer which are essential to enable the carcass layer and thus the flexible pipe body to flex. The bulges are shown in an exaggerated way in Figure 3 by way of explanation. The bulges shown are relatively slight in Figure 3 and may be far more exaggerated. These can selectively intrude into or even mostly fill the gaps between corrugations 360, 370.

Figure 4 illustrates the cross section of a single winding of the elongate tape element shown in Figure 3 in more detail. The tape element cross section has a total thickness illustrated by distance T in Figure 4. This distance T is a distance between a primary plane P which is aligned with the radially inner surface of the planar part 320 in the cross section and an imaginary plane I which is substantially parallel with and spaced apart from the primary plane. The imaginary plane I is a plane which contains the peaks 400, 410 of the first deep corrugation 360 and the further deep corrugation 370 respectively (together with any further deep corrugations for other tape profiles).

As illustrated in Figure 4 the cross section of the elongate tape element 300 has a first planar region which is substantially straight which extends from a first end region 330 of the cross section. The end region 330 terminates in a free end 420 of the cross section. This is created by a long edge of the strip that is originally used to create the carcass tape. From the free end, the tape is generally straight then curves smoothly into the planar region 320. From a remaining end of the planar region the cross section starts to curve away from the primary plane P blending in towards a peak 400. It will be appreciated that the portion of the cross section which extends from the primary plane to the first peak 400 of the first deep corrugation extends substantially perpendicular to the primary plane. When wound as a - - winding of a carcass layer the material in the cross section bridging the primary plane P and the imaginary plane I is aligned substantially radially with flexible pipe body and provides a respective structural element acting as a strut to help resist collapse forces. From the peak 400 of the first deep corrugation the cross section of the elongate tape extends back down towards the primary plane up to a further imaginary plane F. This creates another effective structural element as a strut. The further imaginary plane F is substantially parallel with, but spaced apart from, the primary plane P and the imaginary plane I. The further imaginary plane F is spaced apart from the primary plane by a distance t which corresponds to a thickness t which is uniform across the cross section of the elongate tape and corresponds to an initial thickness of the flat strip used to form the tape element. The first deep corrugation extends to a trough 440. A lower surface (in the orientation shown in Figure 4) of the material in the cross section lies in the further imaginary plane F. The trough has a position substantially in the further imaginary plane F. That is to say the lower surface (shown in Figure 4) of the trough 440 is exactly in the further imaginary plane F or very close to it. In use the lower part of the trough abuts with and can run along an upper surface of the planar region of an adjacent winding.

As illustrated in Figure 4 the cross section of the elongate tape element has at least one further deep corrugation. This extends from the position of the trough 440 towards the next peak 410. The next peak 410 has an outer surface which lies in the imaginary plane I which is spaced apart from the primary plane by a distance T corresponding to a total thickness of a cross section of the elongate tape element. The material of the elongate tape which extends between the trough 440 and the peak 410 extends generally perpendicular to the primary plane P and the imaginary plane I. In practice the material is orientated between 90° and 75° from the primary plane. From the peak 410 the further deep corrugation extends towards a further trough 450 where the lower surface of the tape element lies substantially in the further imaginary plane F. The cross section then curves back towards the imaginary plane I terminating in a further free end 460. The free end 460 points in a direction similar to the direction in which the other free end 420 points.

The first and second deep corrugation in the cross section shown in Figure 4 have a generally sinusoidal shape. It will be appreciated that according to certain embodiments of the present invention the shape of the deep corrugations is variable and can be purely sinusoidal or can be a more "upright" corrugation with substantially straight portions of the cross section bridging between the imaginary and further imaginary plane with almost semi- - - circular curves forming the peaks and troughs. The portions of the cross section extending in a substantially perpendicular or just off perpendicular arrangement between the peak and troughs provide effective structural elements to help provide collapse resistance to the carcass layer. These structural elements provide "verticals" and in the embodiment shown in Figure 4 four verticals are illustrated in the corrugated region whilst the upturned end region 330 may provide a further vertical whereby the free end 420 will be urged against a lower surface of a respective peak of an adjacent winding to help provide collapse resistance in use. Five verticals per cross section of a winding are thus shown in Figure 4. Figure 5 illustrates an alternative embodiment of an elongate tape that can be utilised to provide a carcass layer 120 by helically winding the tape 500 so that adjacent windings become self-interlocked. The carcass tape 500 illustrated in Figure 5 is similar in many respects to that shown in Figure 4 except that the final deep corrugation extends from a peak 510 to a free end 560. This further deep corrugation does not therefore terminate in a curved trough region but rather relies upon the free end 560 of the tape to provide an abutment surface which will ride on and abut against a radially outer surface of the planar portion of an adjacent winding in use. The free end and the further edge region which includes the free end 560 between the free end 560 and the peak 510 of the further deep corrugation thus provides a respective vertical. Five verticals per cross section are thus illustrated in Figure 5. The verticals run between 90° to 75° to the primary plane.

Figure 6 helps illustrate how adjacent windings of the elongate tape 500 shown in Figure 5 compare to the self-interlocking windings of a conventional carcass tape. A conventional carcass tape having a generally S-shaped cross section is illustrated on the left hand side of Figure 6 whilst a first winding 500 a and second winding 500b of the carcass tape shown in Figure 5 in accordance with an embodiment of the present invention is shown on the right hand side of Figure 6. Figure 6 help illustrate how an upturned (in Figure 6) first edge region 530b of a winding sits in a trough of a first deep corrugation of an adjacent winding. Equally Figure 6 helps illustrate how the remaining edge region 550 a of the further deep corrugation has a free end 560 a which rides along the upper surface of the elongate planar region in an adjacent winding.

Figures 5 and 6 illustrate how relative lateral motion between adjacent windings of the carcass layer are limited by the upstanding first edge region 530 moving to and fro within the trough of the first deep corrugation of an adjacent winding. - -

Figure 7 helps illustrate how, in accordance with an alternative embodiment, the profile of the first deep corrugation can be stretched to provide for greater lateral motion and thus flexing of the carcass layer in use. In more detail Figure 7 helps illustrate a cross section of an elongate tape element 700. The elongate tape element has a cross section having a substantially uniform thickness and includes a first generally planar region 720 having a lower surface in a primary plane associated with the cross section and a corrugated region including a first deep corrugation having a flat top and a further deep corrugation having a generally arcuate top. The flat peak 760 of the first deep corrugation means that an upstanding end region of an adjacent winding that sits within the concave region 770 underneath the flat top can laterally move a greater distance than is possible with the preceding embodiments. This provides greater degrees of motion for lateral movement between adjacent windings.

Figure 8 helps illustrate a still further embodiment of the present invention in which the corrugated region in the cross section of the elongate tape element includes three deep corrugations. It will be appreciated that certain embodiments of the present invention can utilise two, three, four or more deep corrugations with a length of the planar region of the cross section being extended accordingly so as to nest within the space under a first peak (or optionally a second peak) of a first corrugation. A first deep corrugation immediately next to the planar region can have a flat top or arcuate top.

Certain embodiments described above have a uniform thickness t throughout the cross section. A radius of curvature of a bend between a first bent edge region and the substantially planar region is less than 4t where t is a uniform thickness of the tape element and where the radius is determined on an outer surface of the bend. Aptly the radius of curvature is less than 2t.

A radius of curvature of a further bend between the substantially planar region and the first deep corrugation is less than 4t where t is a uniform thickness of the tape element and where the radius is determined on an outer surface of the further bend. Aptly the radius is less than 2t. By providing the bends as "tight" bends that have relatively small radii the gap that is provided between adjacent windings can be kept relatively small so as to help reduce promotion of vortex shedding. Certain embodiments of the present invention thus provide an elongate tape element that can be helically wound so that adjacent windings of the tape element self-interlock. A - - portion of the cross section is relatively straight and smooth and when wound extends under the otherwise open parts of a corrugated region of an adjacent winding. The radially outer surface of the carcass layer includes peaks and troughs which helps an overlying barrier layer locate with respect to the carcass layer. As a result the carcass layer formed by the adjacent windings presents a virtually smooth radially inner surface including very few gaps which could otherwise be a source of vortex shedding. The inclusion of multiple deep corrugations in a remainder of the cross section mean that there are multiple "verticals" in the cross section which effectively bridge across a thickness of the carcass layer to provide excellent collapse resistance to the carcass layer.

Certain embodiments of the present invention have been described having a uniform thickness. Other embodiments may not have such a uniform thickness.

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.

Features, integers, characteristics 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 the features and/or steps are mutually exclusive. The invention is not restricted to any details of any foregoing embodiments. The invention extends to any novel one, or 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.

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.