Unbonded flexible pipe for transporting fluid

Abstract

The invention relates to an unbonded flexible pipe (1) for transporting fluids. The flexible pipe comprises a pressure sheath (2), at least one pressure armor layer (3) comprising helically wound elongate elements (7,8,16,18) surrounding the pressure sheath, at least one tensile armor layer (4), and an outer sheath (5). Each of the at least one pressure armor layer comprises at least two elements which are shaped and arranged so that, when seen in cross-sectional view in an imaginary plane perpendicular to a longitudinal winding direction of the elements, at least two of the elements each comprises at least two mutually interconnected plane regions located with at least two different distances from a longitudinal axis of the flexible pipe. The elements form an interlocking engagement with each other and are configured to allow for a limited and predefined possible movement relative to each other in the longitudinal direction of the flexible pipe.

Description

[0001] P85185PC01

[0002] 1

[0003] UNBONDED FLEXIBLE PIPE FOR TRANSPORTING FLUID

[0004] FIELD OF THE INVENTION

[0005] The present invention relates to an unbonded flexible pipe for transporting fluid, e.g. for use within the oil and gas industry. In particular, it relates to an unbonded flexible pipe comprising a least one pressure armor layer with helically wound elongate elements that are configured to allow for a limited and predefined possible movement relative to each other in a longitudinal direction of the flexible pipe.

[0006] BACKGROUND OF THE INVENTION

[0007] Unbonded flexible pipes according to the present invention are typically used in a subsea installation within the oil and gas industry. They are for example described in the standard "Recommended Practice for Flexible Pipe", ANSI / API 17B, fifth edition, May 2014, and the standard "Specification for Unbonded Flexible Pipe", ANSI / API 17J, fourth edition, May 2014. Such pipes usually comprise an inner liner, also often called a pressure sheath or an inner sheath, which forms a barrier against the outflow of the fluid which is conveyed in the bore of the pipe, and one or more armoring layers. Often the pipe further comprises an outer protection layer, referred to as an outer sheath in the following, which provides mechanical protection of the armor layers. The outer sheath may be a sealing layer sealing against ingress of seawater. In certain unbonded flexible pipes, one or more intermediate sealing layers are arranged between the armor layers. The sheaths are typically made from polymer material.

[0008] In general, flexible pipes are expected to have a lifetime of at least 20 years in operation. Examples of unbonded flexible pipes are e.g. disclosed in US 6,978,806; US 7,124,780; US 6,769,454 and US 6,363,974.

[0009] In this text, the term "unbonded" means that at least two of the layers including the armoring layers and polymer layers are not bonded to each other. In practice, the known pipe normally comprises at least two armoring layers located outside the pressure sheath and optionally an armor structure located inside the pressure P85185PC01

[0010] 2 sheath; this armor structure is normally referred to as a carcass. These armoring layers comprise or consist of multiple elongated armoring elements that are not bonded to each other directly or indirectly via other layers along the pipe. Thereby the pipe becomes bendable and sufficiently flexible to roll up for transportation.

[0011] In an unbonded flexible pipe as described, the possible movement of the different elements relative to each other is necessary to ensure that the pipe has the flexibility that is required during storage, handling and use. The pressure armor layer is often made by winding one or more metal strips which have been preshaped into a form that allows for the final mutual shapes of subsequent windings. However, there is a risk that forces or torques applied during handling or use result in too large gaps forming between the windings, thereby potentially reducing the integrity of the pipe. This risk can be lowered by winding metal profiles that form a stronger interlocking, thereby reducing the risk of undesired large deformations. However, such metal profiles can be difficult to handle and may require special equipment for the manufacturing.

[0012] OBJECT OF THE INVENTION

[0013] It is an object of the present invention to provide an unbonded flexible pipe in which the risk of too large gaps arising between windings of the at least one pressure armor layer during storage, handling, or use of the pipe is eliminated or low.

[0014] It is another object of the present invention to provide an unbonded flexible pipe with which the method of manufacturing the at least one pressure armor layer is less complex than for at least some prior art pipes.

[0015] It is another object of the present invention to provide an unbonded flexible pipe with which the method of manufacturing the at least one pressure armor layer is less time consuming than for at least some prior art pipes.

[0016] It is another object of the present invention to provide an unbonded flexible pipe comprising at least one pressure armor layer comprising strips from sheet P85185PC01

[0017] 3 material that require less manufacturing steps compared to traditionally used profiled armour layers.

[0018] It is another object of the present invention to provide an unbonded flexible pipe comprising at least one pressure armor layer wherein the method of producing the at least one pressure armor layer does not comprise the use of traditionally used metal profiles.

[0019] It is a further object of the present invention to provide an alternative to the prior art.

[0020] In particular, it may be seen as an object of the present invention to provide an unbonded flexible pipe that solves the above-mentioned problems of the prior art.

[0021] SUMMARY OF THE INVENTION

[0022] Thus, the above-described object and several other objects are intended to be obtained in a first aspect of the invention by providing an unbonded flexible pipe for transporting fluids, the flexible pipe comprising:

[0023] - a pressure sheath extending in a longitudinal direction of the flexible pipe and being configured to carry a flow of fluid there-through during use,

[0024] - at least one pressure armor layer comprising helically wound elongate elements surrounding the pressure sheath,

[0025] - at least one tensile armor layer surrounding the at least one pressure armor layer, and

[0026] - an outer sheath surrounding the at least one tensile armor layer, wherein each of the at least one pressure armor layer comprises at least two elements which are shaped and arranged so that when seen in cross-sectional view in an imaginary plane perpendicular to a longitudinal winding direction of the elements:

[0027] - at least two of the elements each comprises at least two mutually interconnected plane regions located with at least two different distances from a longitudinal axis of the flexible pipe, and P85185PC01

[0028] 4

[0029] - the elements form an interlocking engagement with each other and are configured to allow for a limited and predefined possible movement relative to each other in the longitudinal direction of the flexible pipe.

[0030] The possible movement of the elements relative to each other is necessary to ensure that the pipe has the flexibility that is required during storage, handling and use. Thus, the movement will be in response to a force or torque being applied with a force component in the longitudinal direction of the flexible pipe. The predefined possible movement will depend on the shape and dimensions of the elements as well as the whole pipe. One of the design parameters when determining the design of the at least one pressure armor layer will therefore include defining the possible movement which ensures that the pipe is as flexible as required while still ensuring that no gap of critical size occurs between the elements. Such gaps could be critical for the functionality or structural integrity of the pipe.

[0031] The flexible pipe is preferably designed to fulfil the design criteria with respect to the minimum bending radius according to ISO 13628-2:2006(E).

[0032] The feature that "the elements form an interlocking engagement with each other" in combination with the related features making this possible could also be referred to as "the elements being complementary shaped".

[0033] The flexible pipe may comprise more layers and components than those mentioned above, such as a carcass and end fittings.

[0034] In some embodiments of the invention, each of the at least one pressure armor layer comprises four elements which are shaped and arranged so that when seen in cross-sectional view in the imaginary plane perpendicular to the longitudinal winding direction of the elements:

[0035] - a first element comprises first side regions and a first central region all regions extending laterally in a plane parallel to the longitudinal direction of the flexible pipe, the first central region being interconnected with the first side regions via first connecting regions, wherein the first central region is closer to the pressure sheath than the first side regions are, P85185PC01

[0036] 5

[0037] - a second element comprises second side regions and a second central region all regions extending laterally in a plane parallel to the longitudinal direction of the flexible pipe, the second central region being interconnected with the second side regions via second connecting regions, wherein the second side regions are closer to the pressure sheath than the second central region is, and wherein the second element is wound around the first element,

[0038] - a third element is plane and arranged in an inward space between a neighbouring layer and the first side regions of two subsequent windings of the first element, and

[0039] - a fourth element is plane and arranged in an outward space between a neighbouring layer and the second side regions of two subsequent windings of the second element,

[0040] - a first total width of neighbouring first side regions of two subsequent windings of the first element is smaller than a width of the second central region of the second element, and

[0041] - a second total width of neighbouring second side regions of two subsequent windings of the second element is smaller than a width of the first central region of the first element.

[0042] In the description of such embodiments, reference is made to the shape of the elements in the imaginary plane perpendicular to the longitudinal winding direction of the elements. The extension of regions of the elements are described in that plane as will be illustrated in more detail in relation to the figures. The elements have a much longer extension in the winding direction.

[0043] The neighbouring layer partly deliming the inward space in which the third element is arranged may e.g. be the pressure sheath. In embodiments comprising more than one pressure armor layer, the neighbouring layer may be such a pressure armor layer. It may also be another type of layer providing additional properties to the flexible pipe. P85185PC01

[0044] 6

[0045] The neighbouring layer partly deliming the outward space in which the fourth element is arranged may e.g. be the at least one tensile armor layer. In embodiments comprising more than one pressure armor layer, the neighbouring layer may be such a pressure armor layer. It may also be another type of layer providing additional properties to the flexible pipe.

[0046] In the embodiments of the invention in which each pressure armor layer comprises four layers as just described, the first total width may be 2-20% smaller than the width of the second central region, such as 5-10% smaller, such as 7-8% smaller, such as 7.7% smaller.

[0047] In the embodiments of the invention in which each pressure armor layer comprises four layers as just described, the second total width may be 2-20% smaller than the width of the first central region, such as 5-10% smaller, such as 7-8% smaller, such as 7.7% smaller.

[0048] The size of the first total width and the second total width will be determined during the design process so that it is ensured that the maximum possible bending of the pipe is obtained without risking undesired gaps between the elements.

[0049] In any of the embodiments of the invention, the elements may have the same or substantially the same thickness. Hereby is meant that the thickness is the same except for possible minor variations caused by the manufacturing tolerances or by local deformation due to bending of the flexible pipe. The use of elements with the same or substantially the same thickness can be a manner of ensuring that the pressure armor layer has plane outer and inner overall surfaces as will be shown in the figures. Hereby the pipe may obtain a high degree of flexibility, because the different layers of the pipe can slide relative to each other.

[0050] In alternative embodiments of the invention, the elements may have different thicknesses. This may still result in the pressure armor layer having plane outer and inner overall surfaces as will be illustrated in the figures. Different thicknesses may also be used to provide a stronger interlocking or an easier shaping process. This may e.g. be relevant if the different metal strips used for a specific design of P85185PC01

[0051] 7 the pressure armor layer are available in different thicknesses from the supplier and can be used without the need for changing the thickness before use.

[0052] The thickness of the elements may be 1-10 mm, such as 2-5 mm, such as 2-3 mm.

[0053] In embodiments of the invention, wherein each pressure armor layer comprises four layers as described above, the width of the first element and of the second element may be 30-200 mm, such as 40-150 mm, such as 40-100mm, such as 45-55 mm. The width is measured in the plane in which the configuration of the layers is described.

[0054] In embodiments of the invention, wherein each pressure armor layer comprises four layers as described above, the cross-sectional shape and dimensions of the first and second elements may be the same except for opposite radial orientations of the first and second side regions with respect to the first and second central regions, respectively. By "radial orientation" reference is made to orientations perpendicular to the longitudinal axis of the flexible pipe. Hereby an optimal compromise is obtained between as large a possible movement as possible and as low a risk as possible of the pressure sheath deforming into gaps of unacceptable size between the elements. Furthermore, it has been found during the development of the present invention that by such designs, the performance of the winding machine used for the manufacturing of the flexible pipe is as stable as possible, because the loading can be balanced around the axis of rotation during the winding.

[0055] In embodiments of the invention, wherein each pressure armor layer comprises four layers as described above, a width of the third element may be larger than a largest possible gap between the first side regions of two subsequent windings of the first element when they are separated to form a first gap. Hereby the gap will always be covered by the third element.

[0056] In embodiments of the invention, wherein each pressure armor layer comprises four layers as described above, a width of the fourth element may be larger than a largest possible second gap between the second side regions of two subsequent P85185PC01

[0057] 8 windings of the second element when they are separated to form a gap. Hereby the gap will always be covered by the fourth element.

[0058] Separation of two subsequent windings to form a gap will typically be due to tensional forces being applied in the longitudinal direction of the flexible pipe during storage, handling or use. Such tensional forces may e.g. be in the form of uniaxial tension or bending.

[0059] In embodiments of the invention, wherein each pressure armor layer comprises four layers as described above, the first connecting regions of the first element may be shaped and dimensioned so that inwardly facing surfaces of the first side regions are flush with an outwardly facing surface of the first central region, and wherein the second connecting regions of the second element are shaped and dimensioned so that outwardly facing surfaces of the second side regions are flush with an inwardly facing surface of the second central region. By "inwardly" is meant with respect to the flexible pipe, i.e. in a direction towards the longitudinal axis of the flexible pipe. An example of such an embodiment will be shown in the figures.

[0060] In some embodiments of the invention, the at least one pressure armor layer comprises two or more pressure armor layers arranged on top of each other. This can be obtained by passing the flexible pipe through the winding machine twice. There could also be more than two layers.

[0061] In some embodiments of the invention, at least some of the elements are provided with through-going holes or slits forming gas passages that allow for escape of gas through the at least one pressure armor layer. Such gas passages can be used to avoid that a critically high pressure is build-up inside the flexible pipe. Whether or not it is necessary to provide all the elements with such through- going holes or slits depends on the shape and arrangement of the elements as the gas may also escape via passages between neighbouring elements.

[0062] In a second aspect, the invention relates to a method of manufacturing an unbonded flexible pipe according to the first aspect of the invention, the method comprising the following steps: P85185PC01

[0063] 9

[0064] - providing the pressure sheath,

[0065] - winding the elements of one of the at least one pressure armor layer simultaneously around the pressure sheath,

[0066] - optionally winding another pressure armor layer around the previously wound pressure armor layer,

[0067] - winding the at least one tensile armor layer around the at least one pressure armor layer, and

[0068] - extruding an outer sheath so that it covers the at least one tensile armor layer.

[0069] In some embodiments of the invention, each step of winding a pressure armor layer comprises providing at least two of the elements with a shape configured to form the interlocking engagement, before they are wound around the pressure sheath or the previously wound pressure armor layer.

[0070] The first and second aspects of the present invention may be combined. Thus, any of the features, alternatives and advantages described in relation to the first aspect of the invention may also apply to the second aspect of the invention. These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.

[0071] BRIEF DESCRIPTION OF THE FIGURES

[0072] The unbonded flexible pipe according to the invention will now be described in more detail with regard to the accompanying figures. The figures show one way of implementing the present invention and is not to be construed as being limiting to other possible embodiments falling within the scope of the attached claim set.

[0073] Figure 1 schematically shows a prior art unbonded flexible pipe for transporting fluids.

[0074] Figure 2 schematically shows a pressure armor layer of an embodiment of the invention.

[0075] Figure 3 schematically shows a pressure armor layer of another embodiment of the invention. P85185PC01

[0076] 10

[0077] Figures 4.a-4.b schematically show a pressure armor layer of another embodiment of the invention.

[0078] Figures 5.a-5.c schematically show the pressure armor layer of figure 4 in three different configurations.

[0079] Figures 6. a and 6.b schematically show two different examples of a pressure armor layer, wherein the thickness of the third and fourth elements are identical but differs from the thickness of the first and second elements.

[0080] Figure 7 schematically shows a pressure armor layer of an embodiment of a flexible pipe according to the invention, wherein all the elements have different cross-sectional geometries.

[0081] Figure 8 schematically shows a pressure armor layer of an embodiment of a flexible pipe according to the invention, wherein the widths of the side regions of both the first element and the second element are different.

[0082] Figure 9 schematically shows two pressure armor layers of figure 4. a arranged on top of each other.

[0083] Figure 10 schematically shows an example in which a third element is provided with through-going holes.

[0084] Figure 11 is a flow diagram of a method according to the second aspect of the invention.

[0085] DETAILED DESCRIPTION OF AN EMBODIMENT

[0086] Figure 1 schematically shows a prior art unbonded flexible pipe 1 for transporting fluids. The flexible pipe comprises a pressure sheath 2 extending in a longitudinal direction of the flexible pipe 1 and being configured to carry a flow of fluid therethrough during use, a pressure armor layer 3 comprising helically wound elongate elements surrounding the pressure sheath 2, two tensile armor layers 4 P85185PC01

[0087] 11 surrounding the pressure armor layer 3, and an outer sheath 5 surrounding the tensile armor layers 4. The illustrated embodiment further comprises a carcass 6 arranged inside the pressure sheath 2 for providing further strength to the pipe 1.

[0088] Figure 2 schematically shows a pressure armor layer 3 of an embodiment of the invention. The illustrated pressure armor layer 3 is seen in cross-sectional view in an imaginary plane perpendicular to a longitudinal winding direction of the elements. This plane will also be used for illustration of the designs in most of the following figures without this being specifically mentioned. Furthermore, in most of the figures, the different regions of the elements are shown as being bent with sharp corners. This is for ease of illustration only whereas the real elements will preferably be interconnected with rounded regions. The actual radius of curvature of the rounded regions will depend on the thickness of the elements and on the method of shaping of the originally plane metal strips used to form the elements into the final shape. The illustrated pressure armor layer 3 in figure 2 comprises two elements 7,8 which each comprises mutually interconnected plane regions 9 located with two different distances from a longitudinal axis of the flexible pipe. In the figure, a first element 7 comprises five regions 9 and a second element 8 comprises four regions 9. The elements 7,8 form an interlocking engagement with each other and are configured to allow for a limited and predefined possible movement relative to each other in the longitudinal direction of the flexible pipe 1.

[0089] Figure 3 schematically shows a pressure armor layer 3 of another embodiment of the invention. In this embodiment both the first element 7 and the second element 8 comprise four plane regions 9 arranged at two different distances from a longitudinal axis of the flexible pipe 1. Other numbers of regions are also covered by the scope of protection, and examples of different configurations will be shown in the following figures. In figure 3, only a part of the leftmost second element 8 is shown.

[0090] Figures 4.a-4.b schematically show a pressure armor layer 3 of another embodiment of the invention. In this embodiment, the pressure armor layer 3 comprises four elements 7,8,16,18 which are referred to as first, second, third, and fourth elements, respectively, in the following. Figure 4. a shows the operating condition of the pressure armor layer, and figure 4.b shows an exploded view. In P85185PC01

[0091] 12 the same way as for the previous figures, the shape and arrangement of these elements are described seen in cross-sectional view in the imaginary plane perpendicular to the longitudinal winding direction of the elements. The first element 7 comprises first side regions 10 and a first central region 11, all regions extending laterally in a plane parallel to the longitudinal direction of the flexible pipe. The first central region 11 is interconnected with the first side regions 10 via first connecting regions 12, and the first central region 11 is closer to the pressure sheath 2 (see figure 1) than the first side regions 10 are. The second element 8 comprises second side regions 13 and a second central region 14, all regions extending laterally in a plane parallel to the longitudinal direction of the flexible pipe. The second central region 14 is interconnected with the second side regions 13 via second connecting regions 15. The second side regions 13 are closer to the pressure sheath 2 than the second central region 14 is, and the second element 8 is wound around the first element 7. The third element 16 is plane and arranged in an inward space 17 between the neighbouring layer, such as the pressure sheath 2, and the first side regions 10 of two subsequent windings of the first element 7. The fourth element 18 is plane and arranged in an outward space 19 between a neighbouring layer, such as the at least one tensile armor layer 4, and the second side regions 13 of two subsequent windings of the second element 8. In the embodiment in figures 4.a-4.b, the first connecting regions 12 of the first element 7 are shaped and dimensioned so that inwardly facing surfaces of the first side regions 10 are flush with an outwardly facing surface of the first central region 11. Furthermore, the second connecting regions 15 of the second element 8 are shaped and dimensioned so that outwardly facing surfaces of the second side regions 13 are flush with an inwardly facing surface of the second central region 14.

[0092] The pressure armor layer in figures 4.a-4.b is an example of an embodiment in which the cross-sectional shape and dimensions of the first and second elements 7,8 are the same except for opposite radial orientations of the first and second side regions 10,13 with respect to the first and second central regions 11,14, respectively. As shown in the figure, the first and second elements 7,8 are dimensioned and shaped so that a first total width TW1 of neighbouring first side regions 10 of two subsequent windings of the first element 7 is smaller than a width of the second central region 14 of the second element 8, and a second total P85185PC01

[0093] 13 width TW2 of neighbouring second side regions 13 of two subsequent windings of the second element 8 is smaller than a width of the first central region 11 of the first element 7. The first total width TW1 may be 2-20% smaller than the width of the second central region 14, such as 5-10% smaller, such as 7-8% smaller, such as 7.7% smaller. The second total width TW2 may be 2-20% smaller than the width of the first central region 11, such as 5-10% smaller, such as 7-8% smaller, such as 7.7% smaller.

[0094] Figures 5.a-5.c schematically show the pressure armor layer of figures 4.a-4.b and illustrate how the elements 7,8,16,18 form an interlocking engagement with each other and are configured to allow for a limited and predefined possible movement relative to each other in the longitudinal direction of the flexible pipe 1. Figure 5. a shows the elements in a neutral configuration, figure 5.b show the elements in an expanded configuration, and figure 5.c show the elements in a compressed configuration. As seen in figure 5.c, even in the compressed configuration, the first and third elements 7,16 are allowed to slide together relative to the second and fourth elements 8,18 so that there is still some flexibility in the pressure armor layer 3. As seen in figure 5.b, the width of the third element 16 is preferably larger than a largest possible gap between the first side regions 10 of two subsequent windings of the first element 7 when they are separated to form a first gap, and the width of the fourth element 18 is preferably larger than a largest possible second gap between the second side regions 13 of two subsequent windings of the second element 8 when they are separated to form a gap. Hereby it is ensured that the elements are always sufficiently supported to remain in the mutual arrangements even when the gaps are as large as possible. As seen in figure 5.c, the widths of the third and fourth elements 16,18 should on the other hand be small enough to allow for the necessary sliding providing the flexibility to the pipe.

[0095] In the previous figures, the elements have the same or substantially the same thickness. Figures 6. a and 6.b schematically show two different embodiments of a pressure armor layer 3, wherein the thicknesses of the third and fourth elements 16,18 are identical but differs from the thickness of the first and second elements 7,8. In figure 6. a, the third and fourth elements 16,18 are thicker than the first and second elements 7,8, and in figure 6.b, the third and fourth elements 16,18 P85185PC01

[0096] 14 are thinner than the first and second elements 7,8. Apart from the different thicknesses, the elements are shaped as in figure 4. a. In the figures, the different thicknesses of the third and fourth elements may be shown exaggerated in relation to the thicknesses of a real product in order to emphasize this feature. As described above, different thicknesses between the elements may e.g. be used to provide a stronger interlocking or an easier shaping process.

[0097] Figure 7 schematically shows a pressure armor layer of another embodiment of a flexible pipe according to the invention. The pressure armor layer resembles the one in figure 4. a except that all the elements have different cross-sectional geometry.

[0098] Figure 8 schematically shows a pressure armor layer of another embodiment of a flexible pipe according to the invention. The pressure armor layer resembles the one in figure 4. a except that the widths of the side regions of both the first element and the second element are different. This could be referred to as an off- centered configuration, as the third and fourth elements are engaged with different widths of neighbouring first and second elements, respectively.

[0099] In some embodiments of the invention, the at least one pressure armor layer 3 comprises two or more pressure armor layers 3 arranged on top of each other. As an example of such an embodiment, figure 9 shows two pressure armor layers of figure 4. a arranged on top of each other.

[0100] As mentioned above, in any of the embodiments of the invention, the elements may be provided with through-going holes or slits forming gas passages that allow for escape of gas through the at least one pressure armor layer 3. Figure 10 schematically shows a simple example in which a third element 16 is provided with through-going holes 20. The size of the holes may differ significantly from what is shown in the figure.

[0101] Figure 11 is a flow diagram showing a method according to the second aspect of the invention, i.e. a method of manufacturing an unbonded flexible pipe 1 according the first aspect of the invention. The method comprises the following steps: P85185PC01

[0102] 15

[0103] A: Providing the pressure sheath 2.

[0104] B: Winding the elements of one of the at least one pressure armor layer 3 simultaneously around the pressure sheath 2.

[0105] C: Optionally winding another pressure armor layer 3 around the previously wound pressure armor layer 3. Since this step is optional, it has been shown with dotted lines.

[0106] D: Winding the at least one tensile armor layer 4 around the at least one pressure armor layer 3.

[0107] E. Extruding an outer sheath 5 so that it covers the at least one tensile armor layer 4.

[0108] As described above, each step of winding a pressure armor layer 3, i.e. steps B and C, may further comprise providing at least two of the elements 7,8,16,18 with a shape configured to form the interlocking engagement, before they are wound around the pressure sheath 2 or the previously wound pressure armor layer 3.

[0109] Although the present invention has been described in connection with the specified embodiments, it should not be construed as being in any way limited to the presented examples. The scope of the present invention is set out by the accompanying claim set. In the context of the claims, the terms "comprising" or "comprises" do not exclude other possible elements or steps. Also, the mentioning of references such as "a" or "an" etc. should not be construed as excluding a plurality. The use of reference signs in the claims with respect to elements indicated in the figures shall also not be construed as limiting the scope of the invention. Furthermore, individual features mentioned in different claims, may possibly be advantageously combined, and the mentioning of these features in different claims does not exclude that a combination of features is not possible and advantageous.

Claims

P85185PC0116CLAIMS1. Unbonded flexible pipe (1) for transporting fluids, the flexible pipe (1) comprising:- a pressure sheath (2) extending in a longitudinal direction of the flexible pipe (1) and being configured to carry a flow of fluid there-through during use,- at least one pressure armor layer (3) comprising helically wound elongate elements (7,8,16,18) surrounding the pressure sheath (2),- at least one tensile armor layer (4) surrounding the at least one pressure armor layer (3), and- an outer sheath (5) surrounding the at least one tensile armor layer (4), wherein each of the at least one pressure armor layer (3) comprises at least two elements (7,8) which are shaped and arranged so that when seen in cross- sectional view in an imaginary plane perpendicular to a longitudinal winding direction of the elements (7,8):- at least two of the elements (7,8) each comprises at least two mutually interconnected plane regions located with at least two different distances from a longitudinal axis of the flexible pipe (1), and- the elements (7,8) form an interlocking engagement with each other and are configured to allow for a limited and predefined possible movement relative to each other in the longitudinal direction of the flexible pipe (1).

2. Unbonded flexible pipe (1) according to claim 1, wherein each of the at least one pressure armor layer (3) comprises four elements (7,8,16,18) which are shaped and arranged so that when seen in cross-sectional view in the imaginary plane perpendicular to the longitudinal winding direction of the elements:- a first element (7) comprises first side regions (10) and a first central region (11) all regions extending laterally in a plane parallel to the longitudinal direction of the flexible pipe (1), the first central region (11) being interconnected with the first side regions (10) via first connecting regions (12), wherein the first central region (11) is closer to the pressure sheath (2) than the first side regions (10) are,- a second element (8) comprises second side regions (13) and a second central region (14) all regions extending laterally in a plane parallel to theP85185PC0117 longitudinal direction of the flexible pipe (1), the second central region (14) being interconnected with the second side regions (13) via second connecting regions (15), wherein the second side regions (13) are closer to the pressure sheath (2) than the second central region (14) is, and wherein the second element (8) is wound around the first element (7),- a third element (16) is plane and arranged in an inward space (17) between a neighbouring layer and the first side regions (10) of two subsequent windings of the first element (7), and- a fourth element (18) is plane and arranged in an outward space (19) between a neighbouring layer and the second side regions (13) of two subsequent windings of the second element (8),- a first total width (TW1) of neighbouring first side regions (10) of two subsequent windings of the first element (7) is smaller than a width of the second central region (14) of the second element (8), and- a second total width (TW2) of neighbouring second side regions (13) of two subsequent windings of the second element (8) is smaller than a width of the first central region (11) of the first element (7).

3. Unbonded flexible pipe (1) according to claim 2, wherein the first total width (TW1) is 2-20% smaller than the width of the second central region (14), such as 5-10% smaller, such as 7-8% smaller, such as 7.7% smaller.

4. Unbonded flexible pipe (1) according to claim 2 or 3, wherein the second total width (TW2) is 2-20% smaller than the width of the first central region (11), such as 5-10% smaller, such as 7-8% smaller, such as 7.7% smaller.

5. Unbonded flexible pipe (1) according to any of the preceding claims, wherein the elements (7,8,16,18) have the same or substantially the same thickness.

6. Unbonded flexible pipe (1) according to any of the preceding claims, wherein the thickness of the elements (7,8,16,18) is 1-10 mm, such as 2-5 mm, such asP85185PC01187. Unbonded flexible pipe (1) according to claim 2 or any of claims 3-6 when dependent on claim 2, wherein the width of the first element (7) and of the second element (8) is 30-200 mm, such as 40-150 mm, such as 40-100mm, such as 45-55 mm.

8. Unbonded flexible pipe (1) according to claim 2 or any of claims 3-7 when dependent on claim 2, wherein the cross-sectional shape and dimensions of the first and second elements (7,8) are the same except for opposite radial orientations of the first and second side regions (10,13) with respect to the first and second central regions (11,14), respectively.

9. Unbonded flexible pipe (1) according to claim 2 or any of claims 3-8 when dependent on claim 2, wherein a width of the third element (16) is larger than a largest possible gap between the first side regions (10) of two subsequent windings of the first element (7) when they are separated to form a first gap.

10. Unbonded flexible pipe according to claim 2 or any of claims 3-9 when dependent on claim 2, wherein a width of the fourth element (18) is larger than a largest possible second gap between the second side regions (13) of two subsequent windings of the second element (8) when they are separated to form a gap.

11. Unbonded flexible pipe (1) according to claim 2 or any claims 3-10 when dependent on claim 2, wherein the first connecting regions (12) of the first element (7) are shaped and dimensioned so that inwardly facing surfaces of the first side regions (10) are flush with an outwardly facing surface of the first central region (11), and wherein the second connecting regions (15) of the second element (8) are shaped and dimensioned so that outwardly facing surfaces of the second side regions (13) are flush with an inwardly facing surface of the second central region (14).

12. Unbonded flexible pipe (1) according to any of the preceding claims, wherein the at least one pressure armor layer (3) comprises two or more pressure armor layers arranged on top of each other.P85185PC011913. Unbonded flexible pipe (1) according to any of the preceding claims, wherein at least some of the elements (7,8,16,18) are provided with through-going holes (20) or slits forming gas passages that allow for escape of gas through the at least one pressure armor layer (3).

14. Method of manufacturing an unbonded flexible pipe (1) according to any of the preceding claims, the method comprising the following steps:- providing the pressure sheath (2),- winding the elements (7,8,16,18) of one of the at least one pressure armor layer (3) simultaneously around the pressure sheath (2),- optionally winding another pressure armor layer (3) around the previously wound pressure armor layer (3),- winding the at least one tensile armor layer (4) around the at least one pressure armor layer (3), and- extruding an outer sheath (5) so that it covers the at least one tensile armor layer (4).

15. Method according to claim 14, wherein each step of winding a pressure armor layer (3) comprises providing at least two of the elements (7,8,16,18) with a shape configured to form the interlocking engagement, before they are wound around the pressure sheath (2) or the previously wound pressure armor layer (3).

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