Removal fluid

Abstract

An apparatus and method for purging fluid from an annular region of a flexible pipe, a method for purging gas from an annular region of a flexible pipe during recovery of an underwater flexible pipe, and an apparatus for limiting fluid pressure in an annular region of a flexible pipe are disclosed. The apparatus for purging fluid from an annular region of a flexible pipe comprises: a first end fitting connected to an end region of a section of a flexible pipe body and comprising a fluid communication region fluidly connected to the annular region of the flexible pipe body; a first purge valve spaced from the first end fitting, the first purge valve including a first valve inlet and a first valve outlet, the first valve outlet being selectively fluidly connectable to the first valve inlet; and a lumen extending between the fluid outlet of the first end fitting and the first valve inlet and in fluid communication with the fluid outlet of the first end fitting and the first valve inlet, the fluid outlet of the first end fitting being fluidly connectable to the fluid communication region.

Description

[0001] The present invention relates to a method and apparatus for purging fluid from an annular region of a flexible pipe. In particular, but not exclusively, the present invention relates to purging gas that has accumulated in an annular region of a flexible pipe to a location associated with a lower local ambient pressure than the location at which the flexible pipe is located during use or recovery of a pipeline comprising a plurality of flexible pipes arranged in an end-to-end configuration.

[0002] Flexible pipes are widely used in offshore applications in the oil and gas industry for transporting oil, gas, water or other fluids from one location to another. Flexible pipes are particularly useful in connecting a sea level support structure and a subsea location, which can be deep underwater, such as 1000 meters or more, where the pipe can act as a riser. Flexible pipes are typically formed as an assembly of a flexible pipe body and one or more end fittings. The flexible pipe body can have an internal diameter of typically up to about 0.6 meters (e.g. the diameter can be in the range of 0.05m up to 0.6m). Due to the location of the flexible pipe, these are exposed to a range of challenging conditions which can have high pressure, sea water, high tensile strain and corrosive environments. As a result, the flexible pipe body is constructed from a number of concentric polymer, metal and / or composite layers. For example, the pipe body can comprise polymer and metal layers, or polymer and composite layers, or polymer, metal and composite layers. The layers can be formed from a single piece such as an extruded tube, or by helically winding one or more wires at a desired pitch, or by joining together a plurality of discrete rings arranged concentrically side by side. Depending on the layers of the flexible pipe used and the type of flexible pipe, some of the pipe layers can be bonded together or remain unbonded. The polymer layers generally provide a seal against ingress of fluids and the metal layer structure rigidity.

[0003] Some flexible pipes have been used in deep water (less than 3,300 feet (1,005.84 meters) and ultra-deep water (greater than 3,300 feet) developments. There is an increasing demand for oil exploration at increasingly greater depths (e.g., over 8,202 feet (2,500 meters)), where environmental factors become increasingly extreme. For example, in such deep water and ultra-deep water environments, the ocean floor temperature increases the risk of production fluid cooling to a temperature that can cause the pipe to plug. In practice, flexible pipes have traditionally been designed to operate at operating temperatures of -30°C to +130°C, and pipe bodies for even more extreme temperatures are being developed. The increased depth also increases the pressure associated with the environment in which the flexible pipe must operate. For example, it can be necessary for the flexible pipe to operate with external pressures acting on the pipe in the range of 0.1 MPa to 30 MPa. Likewise, the transport of oil, gas, or water can well produce high pressures acting on the flexible pipe from the inside, e.g., internal pressures acting on the pipe from wellbore fluids in the range of zero to 140 MPa. Thus, there is an increased need for high levels of performance and environmental toughness of certain layers of the flexible pipe body, such as the pipe carcass layer or pressure armor layer or tensile armor layer. It is noted that for completeness, flexible pipes can also be used in shallow water applications (e.g., depths less than about 500 meters) or even in shore (onshore) applications.

[0004] The innermost layer of the flexible pipe body typically includes an inner sheath, which can be an extruded, non-porous polymer layer that confines wellbore fluids to its inner circumference, and typically includes a carcass, i.e., a helically wound interlocking metal structure that forms the innermost layer. The carcass prevents collapse of the inner liner and also protects the liner from abrasive particles. When a carcass layer is present in the flexible pipe body, the inner sheath is referred to as a barrier layer. When a carcass layer is not present in the flexible pipe body, the inner sheath is referred to as a liner.

[0005] The outermost layer of the flexible pipe is an outer sheath, i.e., an extruded, non-porous polymer layer that protects the structural elements of the pipe from the environment surrounding the flexible pipe and prevents seawater ingress.

[0006] For some flexible pipes that include an intermediate polymer layer, the flexible pipe body can include a plurality of annuli. For many flexible pipes, only an outer polymer layer and an inner polymer layer are included. The annular space of such a flexible pipe is the region between the innermost fluid containment layer and the outermost fluid containment layer. The innermost layer in the annular region is a pressure armour layer made from helically wound flat metallic wire arranged at a lay angle close to 90°. Adjacent windings in the pressure armour layer interlock to control the gap between the coils. The pressure armour is designed to withstand hoop stresses in the pipe wall that are caused by wellbore fluid pressure. Paired tensile armour layers are also located in the annular space and these are cross-wound radially outward of the pressure armour layer. The tensile armour layers are typically made from slightly flattened rectangular metallic wire arranged at a lay angle of about 30° to 55°. The tensile armour layers support the weight of all the internal pipe layers and transmit the resulting tensile stresses to the sea level support structure. The annular space can also have other layers such as anti-abrasion and anti-birdcage tapes, and thermal insulation. Thus, carbon steel wire in the annular space is typically a feature of flexible pipes for subsea environments.

[0007] Traditionally, in end fittings, the flexible pipe body is terminated by sealing and fixing the ends of the polymer or composite layers and fixing any pressure armour coils and fixing tensile armour wires. Thus, the annular space extending along the flexible pipe body section extends into the region within the end fitting. In a configuration where two flexible pipes are joined end to end to form a pipeline, there is no fluid connection between the annular space in one flexible pipe and the annular space in the other flexible pipe.

[0008] The annular space of a flexible pipe body is typically free of fluid (other than a small amount of lubricant used sometimes during manufacture) when delivered. That is, the annular space of a flexible pipe is not expected to contain a significant amount of gas or liquid when the flexible pipe is laid in, for example, a subsea installation during installation. Over time after installation, the annular space of a flexible pipe tends to fill with fluid. This is due to gas and possibly liquid diffusing from the sea water into the annular space through the outer sheath due to factors such as pressure, temperature, outer sheath material, outer sheath thickness, etc. Sometimes, due to the above factors, gas and liquid can likewise or alternatively diffuse from the wellbore fluid into the annular space through the inner sheath (typically a barrier layer or liner). This is particularly true when the wellbore fluid contains a high proportion of certain gases, and can be particularly problematic for flexible pipes of a pipeline that is geographically close to the wellhead.

[0009] Accordingly, the annulus of a flexible pipe that has been resting on the seabed for some time can accumulate annulus gas to a high pressure. If the pressure of the annulus gas is allowed to increase unregulated, the pressure of the annulus gas on the inside of the outer sheath can exceed the hydrostatic pressure of the seawater on the outside of the outer sheath, to the extent that the outer sheath bursts (the actual annulus overpressure relative to the external hydrostatic pressure can vary depending on the construction of the outer sheath layer of the pipe and whether or not there is any reinforcement material on or incorporated into the layer). To mitigate this problem, a minimum of two, and usually three, pressure relief valves are typically installed in each end fitting of a flexible pipe, as specified by the API 17J standard for unbonded flexible pipes. Accordingly, when the annulus fluid pressure exceeds a threshold value above the hydrostatic seawater pressure (typically 2 to 3 bar), the valve opens and "purges" to release the pressure in the annulus. The valve therefore acts as a purge valve and helps to prevent the outer sheath from bursting due to the pressure in the annulus. The maximum flow rate of the valve, the relief pressure of the valve and other such parameters can be selected to limit the ingress of seawater into the annulus during purging.

[0010] At some time, it can be necessary to recover a flexible pipe that has been installed in a subsea environment. For example, when the flexible pipe is no longer in use; to redeploy the flexible pipe in another location; to perform a modification; or the like. During recovery, the flexible pipe body is pulled upwards from its installed position and wound onto reels on a pipe-laying support vessel (PLSV) or otherwise raised. As discussed above, if the flexible pipe has been laid in a subsea environment for some time, the annulus of the flexible pipe can contain gas and / or liquid under pressure. As the flexible pipe is raised from its underwater installed position towards the water surface, the hydrostatic pressure on the outside of the outer sheath of the flexible pipe will decrease at a rate of approximately 1 bar (0.1 Mpa) per 10 m of water depth, whereas the annulus gas pressure does not change with water depth. Accordingly, as the flexible pipe body is raised, the hydrostatic pressure on the outside of the outer sheath can decrease relative to the annulus pressure on the inside of the outer sheath. As described above, when the annulus pressure exceeds a threshold value above the hydrostatic pressure, the valves in the end fittings of the flexible pipe will open to release the excess pressure. If the flexible pipe is raised towards the water surface at a faster rate than the valves can release the excess pressure, the outer sheath of the outer sheath of the flexible pipe can burst due to the excess annulus pressure.

[0011] Typically, the rate of pipe recovery during the period in which the pipe is recovered into the PLSV is limited by the ability of pressure relief valves in the end fittings of the flexible pipe to reduce the annulus pressure. Sometimes, if required, the pipe recovery rate can be set to a fixed safe value to allow time for the valves in the end fittings to reduce the annulus pressure. At other times, a camera on a remotely operated vehicle (ROV) can be used to inform when to reduce the pipe recovery rate by monitoring for gas bubbles when the valves in the end fittings open. Such pipe recovery rates are typically chosen conservatively with a large margin of error, as there can be a large variation in the annulus pressure when above a purge threshold, and there can be uncertainty as to how many pressure relief valves open and therefore how much volume of gas is released, affecting the time required to safely reduce the annulus pressure. As a result, pipe recovery can be an overly slow process, which increases cost and downtime relative to a desired speed.

[0012] Furthermore, when recovering a pipeline including such flexible pipes from an underwater environment, such as a subsea environment, there is a risk of damaging the flexible pipe. If the pipeline is recovered too quickly, the outer sheath of the flexible pipe can burst due to the pressure of the fluid, such as gas, that has accumulated in the annulus region of the flexible pipe and the reduced ambient pressure (pressure associated with the water column of the underwater environment) as the flexible pipe is pulled upwards towards the surface of the underwater environment. The increased pressure difference between the annulus region at the depth of the flexible pipe, which can be an instantaneous depth that changes as the pipe is recovered, and the local environment can cause the flexible pipe to rupture. As a result, it is often necessary to allow a region of the flexible pipe to rest at a particular depth during recovery of the pipeline to allow the fluid accumulated in the annulus region of the flexible pipe to be purged (or vented to the environment). This can significantly increase the time taken to recover a pipeline including multiple flexible pipes, and can increase the costs associated therewith.

[0013] It is an object of the present invention to at least partially alleviate one or more of the above-mentioned problems.

[0014] It is an object of certain embodiments of the present invention to provide an improved purge arrangement for purging fluid that has accumulated in the annulus region of a flexible pipe.

[0015] It is an object of certain embodiments of the present invention to provide a method and apparatus for purging fluid accumulated in the annulus region of a flexible pipe in advance during recovery of a pipeline including multiple flexible pipes.

[0016] It is an object of certain embodiments of the present invention to determine or limit the pressure of fluid accumulated in the annulus region of a flexible pipe in use.

[0017] It is an object of certain embodiments of the present invention to vary or coordinate the pressure at which fluid accumulated in the annulus region of a flexible pipe is purged to the environment for multiple flexible pipes in a pipeline.

[0018] It is an object of certain embodiments of the invention to purge fluid from an annulus of a flexible pipe in an underwater environment at a local ambient pressure lower than the pressure provided by a water column at the location where the flexible pipe is arranged in the water column.

[0019] It is an object of certain embodiments of the invention to fluidly connect an annulus of a flexible pipe arranged in an underwater environment with a region of the underwater environment that is shallower relative to the location of the flexible pipe itself.

[0020] It is an object of certain embodiments of the invention to provide a buoyant module comprising or supporting a purge valve that is fluidly connectable to an annulus of a flexible pipe arranged in an underwater environment below (at a deeper immersion depth) the buoyant module and anchored to the flexible pipe.

[0021] It is an object of certain embodiments of the invention to support a purge valve that is fluidly connectable to an annulus of a first flexible pipe (e.g. on an end fitting of the first flexible pipe) to a further flexible pipe (e.g. on an end fitting of the further flexible pipe) optionally located at a shallower immersion depth in an underwater environment than the first flexible pipe.

[0022] According to a first aspect of the invention, there is provided an apparatus for purging fluid from an annulus of a flexible pipe, comprising: a first end fitting connected to an end region of a section of a flexible pipe body and comprising a fluid communication region fluidly connected to an annulus of the flexible pipe body; a first purge valve spaced apart from the first end fitting, the first purge valve comprising a first valve inlet and a first valve outlet selectively fluidly connectable to the first valve inlet; and a tube cavity extending between and in fluid communication with a fluid outlet of the first end fitting and the first valve inlet, the fluid outlet of the first end fitting being fluidly connectable to the fluid communication region.

[0023] Suitably, the first purge valve is spaced apart above the fluid outlet by a distance optionally greater than 2 meters.

[0024] Suitably, the apparatus further comprises a hose element comprising the tube cavity disposed outside the flexible pipe body and the first end fitting.

[0025] Suitably, the apparatus further comprises a further purge valve comprising a further valve inlet and a further valve outlet, the further valve outlet comprising the fluid outlet and being selectively fluidly connectable to the further valve inlet, such that the further purge valve selectively fluidly connects the fluid communication region and the tube cavity.

[0026] Suitably, the further purge valve is supported on the main body of the first end fitting.

[0027] Suitably, the apparatus further comprises a first flexible pipe comprising the first end fitting and the section of flexible pipe main body, the first flexible pipe being disposed in a pipeline, the pipeline comprising a plurality of flexible pipes, each flexible pipe being disposed in an end-to-end configuration with an adjacent flexible pipe of the plurality of flexible pipes, the adjacent flexible pipes being connected together via respective end fittings of the adjacent flexible pipes; and the first purge valve being supported on a further end fitting of a further flexible pipe, or on a further section of flexible pipe main body of a further flexible pipe.

[0028] Suitably, the further end fitting is disposed above the first end fitting.

[0029] Suitably, the further end fitting is disposed proximal to a flexible pipe recovery device relative to the first end fitting, the flexible pipe recovery device optionally being a winch device.

[0030] Suitably, the first purge valve is connected to the further end fitting via an adapter element, the adapter element being securable to the further end fitting.

[0031] Suitably, the apparatus further comprises a buoyancy control element comprising a buoyant body, the buoyant body supporting the first purge valve.

[0032] Suitably, the apparatus further comprises a rigid frame member in the buoyant body, the rigid frame member providing support for a housing of the first purge valve.

[0033] Suitably, the apparatus further comprises a connection element securable to the rigid frame member for connecting the rigid frame member to the section of flexible pipe main body, wherein a hose element comprising the lumen is secured in the unshown configuration.

[0034] Suitably, the lumen extends through a plurality of hose elements and an anchoring element for anchoring the buoyancy control element to the section of flexible pipe main body, a first hose element and a further hose element of the plurality of hose elements being separated by the anchoring element.

[0035] Suitably, the first end fitting is located in a sub-aqueous environment, and the first purge valve is located at a shallower depth than the first end fitting in the sub-aqueous environment, the sub-aqueous environment comprising a water column.

[0036] Suitably, the local pressure at the first valve outlet is a local ambient pressure provided by the water column at the depth of submersion of the valve outlet.

[0037] Suitably, the first purge valve is configured to fluidly connect the first valve inlet and the first valve outlet when a pressure at the first valve inlet provided by fluid in the lumen exceeds a local pressure at the first valve outlet by a first predetermined pressure.

[0038] Suitably, the first purge valve is configured to fluidly disconnect the first valve inlet and the first valve outlet when a pressure difference between the pressure at the first valve inlet provided by fluid in the lumen and the local pressure at the first valve outlet is less than a first predetermined pressure difference.

[0039] Suitably, the further purge valve is configured to fluidly connect the further valve inlet and the further valve outlet when a pressure at the further valve inlet provided by fluid in the annular region exceeds a pressure at the further valve outlet by a further predetermined pressure, and to fluidly disconnect the further valve inlet and the further valve outlet when a pressure difference between the pressure at the further valve inlet and the pressure at the further valve outlet is less than a further predetermined pressure difference.

[0040] According to a second aspect of the application, there is provided a method of purging fluid from an annular region of a flexible pipe, comprising the steps of: passing fluid from an annular region of a flexible pipe comprising at least one end fitting, through a fluid outlet of the end fitting, the fluid outlet being fluidly connectable to the annular region, and into a lumen in fluid communication with the fluid outlet; passing the fluid through the lumen and to a first valve inlet of a first purge valve, the first purge valve comprising a first valve outlet selectively fluidly connectable to the first valve inlet; fluidly connecting the first valve inlet and the first valve outlet when a pressure at the first valve inlet provided by the fluid exceeds a local pressure at the first valve outlet by a first predetermined pressure; and passing the fluid from the first valve inlet out of the first valve outlet, thereby purging fluid from the annular region.

[0041] Suitably, the method further comprises the steps of: providing the fluid at a further fluid inlet of a further purge valve supported on the end fitting and comprising a further valve outlet comprising the fluid outlet, the further valve outlet being selectively fluidly connectable to the further fluid inlet, prior to passing the fluid through the fluid outlet; and fluidly connecting the further valve inlet and the further valve outlet when a pressure at the further valve inlet provided by the fluid exceeds a pressure at the further valve outlet by a further predetermined pressure.

[0042] Suitably, the method further comprises the step of arranging the first purge valve in a subsea environment comprising a water column such that the local pressure at the first valve outlet is a local ambient pressure provided by the water column at a depth of submersion of the first valve outlet.

[0043] Suitably, the method further comprises the step of arranging the end fitting in a subsea environment and at a depth that is deeper than the depth of submersion of the first valve outlet, such that the first valve inlet and the first valve outlet are selectively fluidly connectable in response to a pressure differential between the pressure in the annulus provided by the fluid and the local ambient pressure at the depth of submersion of the first valve outlet.

[0044] Suitably, the method further comprises the step of urging the first purge valve in an upward direction via a buoyancy provided by a buoyancy control element, such that the first purge valve is located above the flexible pipe, the buoyancy control element comprising a buoyant body that supports the first purge valve.

[0045] According to a third aspect of the present application, there is provided a method of purging fluid from an annulus of a flexible pipe during recovery of the flexible pipe, comprising the steps of urging an end region of the flexible pipe towards a floating platform at a flexible pipe recovery speed, thereby to raise the flexible pipe through the water; and as the flexible pipe is raised, purging fluid from the annulus of the flexible pipe via a fluid communication path through a first purge valve when a pressure at a first valve inlet of the first purge valve provided by the fluid from the annulus exceeds a water pressure at a depth of submersion of a first valve outlet of the first purge valve, the first purge valve being spaced apart from and disposed above the flexible pipe, the fluid communication path extending between the annulus and the first purge valve.

[0046] According to a fourth aspect of the application, there is provided an apparatus for limiting fluid pressure in an annular region of a flexible pipe, comprising: a flexible pipe comprising an end fitting at an end region of a section of the flexible pipe body and disposed in a subsea environment comprising a water column, the end fitting comprising a fluid communication region fluidly connected to an annular region of the flexible pipe; a first purge valve spaced apart from and disposed above the flexible pipe, the first purge valve comprising a first valve inlet and a first valve outlet, the first valve outlet being selectively fluidly connectable to the first valve inlet; and a lumen extending between and fluidly connecting the first valve inlet and a fluid outlet of the end fitting, the fluid outlet of the end fitting being fluidly connectable to the fluid communication region; wherein the first purge valve is configured to fluidly connect the first valve inlet and the first valve outlet to selectively purge fluid from the annular region and thereby limit fluid pressure in the annular region when the pressure at the first valve inlet provided by fluid from the annular region exceeds the local ambient pressure at the first valve outlet by a first predetermined pressure.

[0047] Suitably, the first purge valve is disposed in the subsea environment such that the local ambient pressure at the first valve outlet is the water pressure provided by the water column at the depth of submersion of the first valve outlet.

[0048] Certain embodiments of the application enable reduced downtime when recovering a pipeline from a subsea environment due to a need to allow fluid to be expelled from an annular region of one or more flexible pipes of the pipeline.

[0049] Certain embodiments of the application enable reduced risk of damage to a flexible pipe (e.g. burst (rupture of an outer sheath of the pipe)) due to pressure associated with fluid accumulated in the annular region of the pipe.

[0050] Certain embodiments of the application provide a purge valve that is fluidly connectable to an annular region of a flexible pipe via an external fluid pipe or other such fluid communication passage and is disposed at a shallow depth of submersion in a subsea environment relative to the flexible pipe itself.

[0051] Certain embodiments of the application enable increased rate of expulsion / purging of fluid from an annular region of a submerged flexible pipe.

[0052] Certain embodiments of the application enable pre-purging of fluid from an annular region of a flexible pipe during recovery of the flexible pipe from a subsea environment.

[0053] Some embodiments of the invention provide a fluid communication path between the annulus of a first flexible pipe and a purge valve on a further flexible pipe (e.g. on an end fitting of the further flexible pipe).

[0054] Some embodiments of the invention provide a fluid communication path between a purge valve and the annulus of a flexible pipe, the purge valve being supported on a buoyancy module. Optionally, the buoyancy module can have a selectable buoyancy to raise or lower the module and associated purge valve as required.

[0055] Some embodiments of the invention reduce the fluid pressure required in the annulus of a flexible pipe to purge fluid from the annulus into an underwater environment at a particular depth of submersion of the flexible pipe.

[0056] Some embodiments of the invention provide an annulus gas passage from an end of one flexible pipe section to an end of another flexible pipe section, the annulus gas passage passing through a section of thermoplastic composite pipe, the section being impermeable to the passage of annulus gas internally to the pipe wall (i.e. through the annulus).

[0057] Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:

[0058] Figure 1 A flexible pipe body is illustrated;

[0059] Figure 2 Some uses of the flexible pipe as a pipeline and pipe recovery are illustrated;

[0060] Figure 3 An end of the flexible pipe is illustrated, the flexible pipe body terminating in an end fitting at the end;

[0061] Figure 4 A portion of an end fitting including a purge valve is illustrated;

[0062] Figure 5a How a purge valve can be arranged on an end fitting of a flexible pipe is illustrated;

[0063] Figure 5b A purge valve is illustrated in more detail in cross-section;

[0064] Figure 6 How a purge valve fluidly connectable to the annulus of a first flexible pipe can be supported on an end fitting of a further flexible pipe, the further flexible pipe being closer to the surface of a subsea environment relative to the first flexible pipe;

[0065] Figure 7aA first example of how a purge valve, which is fluidly connectable to an annular region of a first flexible pipe, can be supported on an end fitting of a further flexible pipe is illustrated;

[0066] Figure 7b A further example of how a purge valve, which is fluidly connectable to an annular region of a first flexible pipe, can be supported on an end fitting of a further flexible pipe is illustrated;

[0067] Figure 7c A further example of how a purge valve, which is fluidly connectable to an annular region of a first flexible pipe, can be supported on an end fitting of a further flexible pipe is illustrated;

[0068] Figure 8a How a purge valve can be arranged on a buoyant module floating above a flexible pipe comprising an annular region to which the purge valve is fluidly connectable is illustrated;

[0069] Figure 8b How a purge valve can be arranged on a buoyant module floating above a flexible pipe comprising an annular region to which the purge valve is fluidly connectable is illustrated in more detail;

[0070] Figure 9a A first buoyant module on which a purge valve is arranged is illustrated;

[0071] Figure 9b A further buoyant module on which a purge valve is arranged is illustrated;

[0072] Figure 10a A first arrangement for anchoring a buoyant module to a flexible pipe on which a purge valve is arranged is illustrated;

[0073] Figure 10b A further arrangement for anchoring a buoyant module to a flexible pipe on which a purge valve is arranged is illustrated;

[0074] Figure 11 How a buoyant module comprising a purge valve can be arranged in and on the surface of an underwater environment is illustrated;

[0075] Figure 12 How a purge valve arranged on an end fitting and connected to an external fluid pipe can prevent an overflow of an annular region of a flexible pipe if the external fluid pipe is damaged in use is illustrated;

[0076] Figure 13 Cross-sectional views of different purge valves are illustrated; and

[0077] Figure 14 A cross-sectional view of a further purge valve is illustrated.

[0078] In the drawings, like reference numerals refer to like parts.

[0079] Throughout the specification, reference will be made to flexible pipe. It will be appreciated that certain embodiments of the present application are applicable to various flexible pipes. For example, certain embodiments of the present application can be used in connection with flexible pipe bodies and associated end fittings of the type manufactured in accordance with API 17J. Such flexible pipes are commonly referred to as unbonded flexible pipes. Other embodiments are associated with other types of flexible pipes.

[0080] It will be appreciated that the exemplified flexible pipe is an assembly of a portion of a flexible pipe body and one or more end fittings, respective ends of the pipe body being terminated in each of the one or more end fittings. Figure 1 It is exemplified how the pipe body 100 is formed from a combination of layered materials that form a pressure containing conduit. Although Figure 1 A number of specific layers are exemplified, it will be appreciated that certain embodiments of the present application are broadly applicable to coaxial pipe body structures comprising two or more layers made from a variety of possible materials. The pipe body can comprise one or more layers comprising a composite material, thereby forming a tubular composite layer. It will also be noted that the layer thicknesses are shown for illustrative purposes only. As used herein, the term "composite material" is used to broadly refer to a material formed from two or more different materials, for example a material formed from a matrix material and reinforcing fibers.

[0081] Thus, a tubular composite layer is a layer having a generally tubular shape formed from a composite material. Alternatively, a tubular composite layer is a layer having a generally tubular shape formed from a plurality of components, one or more of the plurality of components being formed from a composite material. The layer or any element of the composite layer can be manufactured via an extrusion, pultrusion or deposition process, or via a winding process in which adjacent coils of a tape having a composite structure in and of themselves are consolidated together with adjacent coils. Regardless of the manufacturing technique used, the composite material can optionally comprise a matrix or body of a material having a first property in which is embedded a further element having a different physical property. That is, elongate fibers that are aligned to some extent or smaller fibers that are randomly oriented can be disposed into a body, or spheres or other regularly or irregularly shaped particles can be embedded into a matrix material, or a combination of more than one of the foregoing. Suitably, the matrix material is a thermoplastic material, suitably 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 fibers made from one or more of glass, ceramic, basalt, carbon, carbon nanotubes, polyester, nylon, aramid, steel, nickel alloys, titanium alloys, aluminum alloys, etc. or fillers made from glass, ceramic, carbon, metals, buckyballs, metal silicates, carbides, carbonates, oxides, etc.

[0082] Figure 1The exemplified pipe body 100 includes an inner pressure sheath 110 which acts as a fluid retention layer and includes a polymer layer which ensures internal fluid integrity. This layer provides a boundary for any conveyed fluid. It will be appreciated that this layer can itself comprise a plurality of sub-layers. It will be appreciated that the inner pressure sheath is commonly referred to by those skilled in the art as a barrier layer when a carcass layer 120 is utilised. In operations without such a carcass (so-called smooth bore operations), the inner pressure sheath can be referred to as a liner. Figure 1 The barrier layer 110 is exemplified.

[0083] It is noted that the carcass layer 120 is a pressure resistant layer which provides an interlocking construction which can act as an innermost layer to fully or partially prevent the inner pressure sheath 110 from collapsing due to pipe decompression, external pressure and tensile armour pressure and mechanical break load. The carcass is a pressure resistant layer. It will be appreciated that certain embodiments of the present application are therefore suitable for 'rough bore' applications (with a carcass). Suitably, the carcass layer is a metal layer. Suitably, the carcass layer is formed from stainless steel, corrosion resistant nickel alloys or the like. Suitably, the carcass layer is formed from a composite material, a polymer or other material or combination of materials and components. The carcass layer is typically positioned radially within the barrier layer.

[0084] The carcass layer is a 'layer' in the sense that the radially innermost and outermost surfaces arise at a single manufacturing node in a single pass. The single manufacturing node can comprise a plurality of strip handling segments which are brought axially close together such that the segments effectively are a single node. The node suitably extends over an axial distance of less than 2.5m. Suitably, the node has a length of 1 m or less.

[0085] The pipe body includes a pressure armour layer 130 which is a pressure resistant layer which provides a structural layer which increases the resistance of the flexible pipe to internal and external pressure and mechanical break load. The layer also structurally supports the inner pressure sheath. Suitably, as Figure 1 The pressure armour layer is exemplified as being formed as a tubular layer. Suitably, for a non-bonded flexible pipe, the pressure armour layer is comprised of an interlocking construction of wires having a lay angle close to 90°. Suitably, in this case, the pressure armour layer is a metal layer. Suitably, the pressure armour layer is formed from carbon steel, aluminium alloys, stainless steel or the like. Suitably, the pressure armour layer is formed from a pultruded composite interlocking layer. Suitably, the pressure armour layer is formed from a composite material formed by extrusion or pultrusion or deposition. The pressure armour layer is positioned radially outward of the underlying barrier layer.

[0086] The example flexible pipe body also includes a first tensile armour layer 140 and a second tensile armour layer 150. Each tensile armour layer serves to maintain tensile load and, optionally, also internal pressure. Suitably, for some flexible pipes, the tensile armour wire is metal (e.g. steel, stainless steel or titanium, etc.). For some composite flexible pipes, the tensile armour wire can be a polymer composite tape (e.g. provided with a thermoplastic, such as nylon, a matrix composite material or a thermoset material, such as epoxy, a matrix composite material). For unbonded flexible pipes, the tensile armour layer is formed from a plurality of wires (to impart strength to the layer), positioned over the inner layer and helically wound along the length of the pipe at a lay angle typically between about 10° to 55°. Suitably, the tensile armour layer is wound in pairs in opposite directions. Suitably, the tensile armour layer is a metal layer. Suitably, the tensile armour layer is formed from carbon steel, stainless steel, titanium alloy, aluminium alloy, etc. Suitably, the tensile armour layer has a microstructure comprised of oriented lamellae. Suitably, the tensile armour layer is formed from a composite material, a polymer or other material or combination of materials.

[0087] Suitably, the flexible pipe body includes an optional tape layer 160 which helps contain the layers below and to some extent prevent abrasion between adjacent layers. The tape layer can optionally be a polymer or composite material or combination of materials and also optionally includes a tubular composite layer. The tape layer can be used to help prevent metal on metal contact to help prevent abrasion. A tape layer over the tensile armour can also help prevent "cageing" of the tensile armour wires.

[0088] The flexible pipe body also includes an optional insulation layer 165 and an outer sheath 170 which includes a polymer layer for protecting the pipe from penetration, corrosion, abrasion and mechanical damage by seawater and other external environments. Any thermal insulation layer helps limit heat loss through the pipe wall to the surrounding environment. The annular space 180 is the region associated with the space between the inner pressure sheath 110 and the outer sheath 170. In other words, the annular space 180 is the space between the inner pressure sheath 110 and the outer sheath 170. Figure 1 In the example flexible pipe body, the pressure armour layer 130, the first tensile armour layer 140, the further tensile armour layer 150, the optional tape layer 160 and the optional insulation layer 165 are located in the annular region 180. It will be appreciated that in some embodiments the annular region 180 can contain Figure 1 Any or none of the layers present in the example flexible pipe body.

[0089] Each flexible pipe includes at least one portion of the pipe body 100 (referred to as a section or segment) and an end fitting positioned at at least one end of the flexible pipe. A respective end fitting can be used to terminate each end of the flexible pipe body. The end fitting provides a mechanical means of forming a transition between the flexible pipe body and a connector. For example, as Figure 1The different pipe layers shown terminate in end fittings, such that load is transferred between the flexible pipe and the connector.

[0090] Figure 2 A pipe 200 suitable for transporting production fluids such as oil and / or gas and / or water from a subsea location 221 to a pipe-lay support vessel (PLSV) 222 is illustrated. In Figure 2 In some examples, the PLSV can be a ship. For example, in Figure 2 In some examples, the subsea location 221 comprises a subsea flowline 225. The flexible flowline 225 comprises a flexible pipe that is all or partially resting on or buried under a seabed 230 and used for static applications. In some alternatives, the PLSV can be provided by a platform. In other alternatives, the PLSV can be provided by a floating platform. The pipe 200 is an assembly. That is, a plurality of flexible pipes 240 extend between the PLSV 222 to the seabed. The pipe 200 shown has six flexible pipes 2401, 2402, 2403, 2404, 2405, and 2406. In the pipe 200, adjacent flexible pipes 240 are joined by securing their end fittings together in an end-to-end configuration. It will be appreciated that in other examples, the pipe 200 can alternatively have any number of a plurality of flexible pipes 240, such as two, three, four, five, or more flexible pipes. It will be appreciated that a pipe can comprise a plurality of flexible pipes.

[0091] It will be appreciated that some segments of a pipe assembly can comprise a thermoplastic composite pipe, i.e., a pipe having a structure made at least partially of composite material. Optionally, a pipe assembly comprising a thermoplastic composite pipe can be referred to as a thermoplastic composite pipe. Optionally, a thermoplastic composite pipe can comprise a plurality of layers of adhesive tape to provide a pipe with a desired wall thickness and strength (axially and with respect to internal pressure). Optionally, a thermoplastic composite pipe can comprise additional thermoplastic tubular (typically extruded) layers radially inside and / or outside of the composite material. Optionally, the thermoplastic tubular layers are bonded to the composite material layers of the thermoplastic composite pipe. Some thermoplastic composite pipes can not have an annular space in which permeated gas can accumulate and permeate through to the end fitting. Optionally, some thermoplastic composite pipes can be at least partially free of an annular space, and thus can not have the option to through-connect the annular space of a flexible pipe on either side of a segment of thermoplastic composite pipe, thereby not being able to release higher annulus pressure in one flexible pipe segment or another flexible pipe segment to lower annulus pressure in the other flexible pipe segment via a fluid connection. Certain embodiments of the present invention can overcome this limitation, providing an annulus gas pathway from the end of one flexible pipe segment to the end of another flexible pipe segment, through a segment of thermoplastic composite pipe through which annulus gas cannot be transmitted internally to the pipe wall (i.e., through the annular space).

[0092] In early use, some pipes may have been used as risers, while others may have been used as flow lines. For example, it should be understood that different types of risers exist, as is well known to those skilled in the art. Certain embodiments of the invention can be used with the recycling of any type of riser, such as freely suspended risers (free-suspension catenary risers), partially constrained risers (buoys, chains), fully constrained risers, or risers enclosed in a pipe (I-pipe or J-pipe). Some (though not all) examples of such configurations can be found in API 17J. Recyclable portions of flexible pipes may also have been pre-used as crosspipes.

[0093] Figure 3 An example is shown of the first ( ) arranged in a back-to-back configuration. Figure 3 The leftmost end fitting 3001 and the rightmost end fitting 3002 are shown. The first end fitting 3001 terminates at a corresponding end of a first section of the flexible tube body 1001, while the other end fitting 3002 terminates at a corresponding end of a different section of the flexible tube body 1002. It should be understood that yet another end fitting may terminate at the remaining end of the first section of the flexible tube body 1001 or the remaining end of a different section of the flexible tube body 1002. The end fittings 3001 and 3002 are connected together via corresponding connector flanges 3101 and 3102. These are connected via bolts ( Figure 3 (Not shown) Bolted together and having matching sealing ring grooves on opposite flange surfaces.

[0094] Each end fitting 300 also includes a central flange 320 spaced from the connector flange 310 via a neck region 330. An outer sheath 340 is secured to the central flange, and an outer collar 350 is secured to the sheath 340 and seals against the outer surface of the outer sheath 170 of the flexible tube body 100 via at least one sealing ring. The radially innermost surface of the sheath 340 is spaced from the radially outer surface of the generally cylindrical but slightly flared end of the elongated end fitting body 360 of the end fitting. An opening 365 of the end fitting body faces an associated segment of the flexible tube body. A stretch armored wire terminates in a tapered space between the outer housing and the end fitting body. Suitably, epoxy resin is located in the tapered space to bury the end of the stretch armored wire. The end fittings 300 are associated with a central longitudinal axis AA, and when the end fittings are arranged in a back-to-back configuration, the central longitudinal axis of each end fitting is aligned along a common line. During use, the produced fluid is delivered along the orifices provided by the barrier layer or lining of the flexible tube body and the inner surface of each end fitting 300.

[0095] Figure 3The illustrated end fittings 3001, 3002 also each include a respective purge valve 3701, 3702. It will be appreciated that the purge valves are fluidly connected to the annular region of each respective flexible pipe via a respective internal tube 3801, 3802 which is not filled with epoxy resin and thus provides a fluid communication path of the end fitting extending between the respective purge valve and the annular region of the flexible pipe.

[0096] Figure 4 An end fitting 400 of a flexible pipe 401 and a portion of a flexible pipe body 100 are illustrated in more detail. The flexible pipe 401 comprises the end fitting 400 and the flexible pipe body 100. The flexible pipe body 100 comprises, from innermost to outermost: an inner pressure sheath 110 (or fluid retention layer), an annular region 180 and an outer sheath 170. It will be appreciated that, Figure 4 The flexible pipe body 100 in Figure 4 has a smooth bore, however, it will be appreciated that a rough bore flexible pipe body can alternatively be utilised. The annular region 180 comprises a pressure armour layer 130, a first tensile armour layer 140 and a further tensile armour layer 150. It will be appreciated that other layers can be present in the annular region 180. For example, as Figure 3 The end fitting 400 is illustrated as being generally cylindrical in shape.

[0097] Figure 4 The end fitting 400 is illustrated as being generally cylindrical in shape. Figure 4 The purge valve 410 in Figure 4 is recessed into the body of the end fitting 400, however, it will be appreciated that the purge valve 400 can protrude from or can be supported on the end fitting 400. It will be appreciated that the purge valve 410 can be referred to as a purge outlet or a drain valve. It will be appreciated that, Figure 4 The purge valve 410 in Figure 4 is in a front end drain configuration, however, it will be appreciated that any other suitable configuration can alternatively be utilised, such as a side drain, in which the purge valve 410 is connected to the jacket, for example, at a similar location to the epoxy fill port 420. Figure 4 The annulus gas from the annular region 180 can be shown as how it is passed to the purge valve via an internal tubing 415 which is a drain tubing. The internal tubing 415 is a fluid communication passage which connects the inlet of the purge valve to the annular region of the flexible pipe. Suitably, no drain tubing is utilised, but rather a different fluid communication passage between the purge valve and the annular region is utilised. The drain tubing 415 is a stainless steel tubing which connects the annular region 180 to the purge valve 410. The drain tubing 415 is surrounded by hardened epoxy resin in an epoxy housing 416 which is a cavity in the end fitting in which the tensile armour wires are terminated. It will be appreciated that the drain tubing 415 can alternatively be made of any alloy, composite, polymer, etc.

[0098] The end fitting 400 has two filling ports: a first filling port 420 and a second filling port 422 sealed with epoxy resin. It should be understood that the filling ports 420 and 422 can be made of different materials (such as any polymer). Sometimes, it should be understood that there may be one filling port in the end fitting. In other examples, there may be more than two filling ports in the end fitting. It should be understood that one or more epoxy resin filling ports can be used to supply epoxy resin into the epoxy resin housing to secure the stretch armored wire in the end fitting.

[0099] The flexible tube body 100 is attached to the end fitting 400 by separating the layers of the flexible tube body 100 at its end portions and securing these layers to the end fitting 320. An inner pressure sheath 110 terminates in a first clamping region 430 and is held in place by a friction fit. The inner pressure sheath 110 is clamped in the first clamping region 430 between a first half and a second half of the end fitting 400. This prevents fluid leakage from the inside of the inner pressure sheath 110 into the annular region 180. The pressure armor layer 130 terminates separately from the remaining layers in the annular region 180. An outer sheath 170 terminates in a further clamping region 440 and is held in place by a friction fit. This prevents fluid leakage from the outside of the outer sheath 170 into the annular region 180. Therefore, the annular region 180 is sealed to prevent fluid from entering from both sides. The epoxy resin housing 416 in the end fitting 400 fills the open space, within which the layer of the annular region 180 is terminated. The epoxy resin housing 416 is filled by pumping epoxy resin into the first filling port 420. Excess epoxy resin is removed through the second filling port 422.

[0100] Figure 5a This illustrates how the purge valve 505 can be positioned on the end fitting 510 of the flexible tube 512. For example... Figure 5a As illustrated, the purge valve 505 is disposed in the outer region of the central flange 515 of the end fitting 510. It should be understood that the purge valve is fluidly connected to a cavity disposed between the housing and body of the end fitting. It should be understood that the cavity is a region of the end fitting where one or more layers of the stretched armored wire may terminate. It should be understood that the cavity is an example of a fluid communication region that is in fluid communication with the annular region of the flexible tube 512. It should be understood that the purge valve 505 may be located at any other suitable location on the end fitting 510 (or flexible tube) as long as it is fluidly connected to the annular space of the flexible tube 512 (optionally via the fluid communication region of the end fitting 510). Although Figure 5aOnly one purge valve 505 is illustrated, but it should be understood that multiple purge valves (e.g., two, three, four, five or more purge valves) may be arranged on the end fitting 510.

[0101] Figure 5b More detailed examples Figure 5a The purge valve 505. (For example...) Figure 5b As shown, the purge valve 5b includes a valve housing 550, which includes a channel 555 in which a slidable member 560 is disposed. The end of the slidable member 560 includes a piston head 565, which rests against a valve seat 570 of the housing 550 when the purge valve 505 is arranged in the closed configuration. It should be understood that when the valve 550 is arranged in the closed configuration, the piston head 565 and the valve seat 570 form a fluid seal, thereby preventing fluid communication between the inlet 572 and the outlet 574 of the valve 505. It should be understood that the inlet 572 or the valve 505 is fluidly connected to the fluid communication area of ​​the end fitting 510, and therefore also fluidly connected to the annular area of ​​the flexible tube.

[0102] like Figure 5b As shown, the purge valve 505 also includes a spring 580. It should be understood that the spring is an example of a biasing element. Figure 5b As shown, spring 580 is connected to piston head 565 and also to an area of ​​housing 550. It should be understood that spring 580 is in an extended or stretched state such that it biases the slidable member toward the fluid inlet 572 of valve 505, thereby pushing piston head 565 into a sealing engagement with valve seat 570. Therefore, spring 580 helps to push the purge valve into a closed configuration, in which the fluid inlet 572 and fluid outlet 574 are disconnected from the fluid connection. When used in a subsea environment, the upper surface of piston head 565 (the surface closest to the fluid outlet 574 of valve 505) is exposed to the local environment of seawater. Therefore, piston head 565 is exposed to local environmental pressure A, which is the pressure of seawater at the immersion depth of outlet 574 of purge valve 505. It should be understood that the local environmental pressure is therefore the pressure of the water column at the immersion depth of outlet 574. Therefore, this local environmental pressure A helps to further induce purge valve 505 into the closed configuration.

[0103] like Figure 5bIt is also illustrated that the inlet 572 of the purge valve is exposed to the internal pressure B associated with the annular space of the flexible pipe. As noted above, this is because the inlet 572 is in fluid communication with the annular region via the fluid communication region of the end fitting 510. Thus, the fluid pressure in the annular region of the flexible pipe is exerted on the remaining end of the slidable member 560, which is the end closest to the fluid inlet 572 and opposite the piston head 565. It will be appreciated that the pressure at the fluid inlet 572 is the fluid pressure provided by the fluid flowing from the bore of the flexible pipe into the annular region in use. Suitably, this fluid is gaseous.

[0104] When the fluid pressure B at the fluid inlet 572 exceeds the local ambient pressure A by a predetermined amount, the fluid pressure urges the slidable member towards the fluid outlet 574 of the valve 505, thereby urging the valve 505 to an open configuration. It will be appreciated that this action fluidly connects the inlet 572 and the outlet 574 of the valve 505. Thus, the valve is responsive to the pressure differential across the valve, and selectively connects the inlet and the outlet in response to this pressure differential. It will thus be appreciated that the purge valve can be manufactured to open at a predetermined or substantially predetermined pressure differential provided by the first pressure at the inlet and the further pressure at the outlet. For example, this can be achieved by utilising a spring having a particular stiffness or elasticity. It will thus be appreciated that the valve 505 can be designed to purge gas from the annular region of the flexible pipe before the pressure provided by the gas in the annular region reaches a point at which there is a risk of damage to the pipe, for example due to bursting of the outer sheath of the pipe.

[0105] It will be appreciated that the valve design can vary, and can incorporate a plurality of resilient elements, optionally including springs on either side of the valve seat 570, to balance the resistance of the springs to the internal pressure B and the local ambient pressure A. Alternatively, the valve can be constructed with a single spring on the outside of the valve seat 570, which acts in compression, with the ability to adjust the degree of compression and thus the overpressure required to open the valve.

[0106] Alternatively, any other suitable purge valve can be utilised.

[0107] Figure 6 It is illustrated how a purge valve 602, which is able to fluidly connect to the annular region of a first flexible pipe 604, can be supported on an end fitting of a further flexible pipe 606. Figure 6 It is illustrated that a portion of the pipeline 608. As Figure 6 It is illustrated that at least some of the pipelines 608 are arranged in a subsea environment 610. The pipeline includes a first flexible pipe 604 and a further flexible pipe 606. As Figure 6 It is shown that the first flexible pipe 604 and the further flexible pipe 606 are arranged in the subsea environment 610 underwater. Figure 6This illustration demonstrates how a first flexible tube 604, compared to another flexible tube 606, can be positioned at a greater depth in a seabed environment. Specifically, the other flexible tube 606 is positioned closer to the surface of the water column than the first flexible tube 604. It should be understood that the pipeline can be a riser, etc., and that the first flexible tube may be positioned at a greater depth underwater than the other flexible tube throughout the pipeline's lifespan. It should also be understood that the pipeline may be partially or entirely positioned on the seabed, and therefore the other flexible tube may only be positioned intermittently at a shallower depth than the first flexible tube, for example, during pipeline retrieval operations where the pipeline is hauled to the surface position. It should be understood that the other flexible tube is positioned closer to or near the surface of the water column (at or near sea level) at its pipe termination point. It should be understood that the pipeline comprises multiple flexible tubes arranged end-to-end and abutted via corresponding end fittings.

[0108] like Figure 6 As shown, the first end flexible tube includes a first end fitting 612 disposed at the first end of the flexible tube. It should be understood that the flexible tube body 614 of the first flexible tube 604 is terminated in the first end fitting 612. It should be understood that, although not shown, the remaining end of the flexible tube body 614 of the first flexible tube 604 may also be terminated in the end fitting. Figure 6 This helps to illustrate how the connector flange 615 of the first end fitting 612 is connected to the connector flange 616 of the adjacent end fitting 618 of the adjacent flexible tube 620.

[0109] Figure 6 The diagram illustrates how an additional flexible tube 606 includes an additional end fitting 622, into which an additional tube body 624 of the additional flexible tube 606 is terminated. It should be understood that the additional flexible tube 606 may be an adjacent flexible tube 620, and the additional end fitting 622 may be located at the end of the additional flexible tube 620, opposite the end of the adjacent end fitting 618. Alternatively, one, two, three, or more flexible tubes may be disposed between the first flexible tube 604 and the additional flexible tube 606, and connected in an end-to-end configuration.

[0110] like Figure 6 As illustrated, the first purge valve 602 is supported on a separate end fitting 622. Figure 6 The first purge valve 602 is mounted on an additional end fitting 622 via an adapter 625. It should be understood that the adapter allows the first purge valve to be retrofitted to existing piping. It should be understood that the first purge valve 602 can also be supported on the additional end fitting 622 without an adapter. It should be understood that the first purge valve 602 can be similar to [reference needed]. Figure 5bThe purge valve 505 described, however, has the inlet 626 of the first purge valve 602 not fluidly connected to the annular region of the further flexible tube 606. Rather, as shown, Figure 6 the inlet 626 of the first purge valve 602 is fluidly connected to an external fluid tube or hose element 628 (which is external to the pipe 608). That is, the external tube 628 is fluidly connected to the inlet 626 of the valve 602. It will be appreciated that the external tube 628 is an example of a lumen. It will be appreciated that the external tube is an example of a hose element. It will be appreciated that the lumen can comprise a plurality of hose elements or external fluid tubes. It will be appreciated that the external tube 628 can be made of a flexible material. It will be appreciated that the external tube can be made of a rigid material. It will be appreciated that the external tube can be made of a polymeric material. It will be appreciated that the external tube is substantially leak-proof. The purge valve 602 can be an end connector which prevents biological contamination and / or clogging of the end of the external tube 628.

[0111] As shown in Figure 6 the external tube (which can be an example of a hose element) 628 extends along the length of the pipe 608 but is external to the pipe 608 between the inlet 626 of the first purge valve 602 and a further purge valve 630 supported on the first end fitting 604. Figure 6 The further purge valve 630 is substantially the same as the purge valve 505 described with reference to Figure 5b and is supported on the first end fitting 604 in substantially the same way. Suitably, any other suitable valve can be used instead. Suitably, the external tube 628 is connected directly to the first end fitting 612 (without passing via any further purge valve) and is in fluid communication with the annular space of the first flexible tube 604.

[0112] Thus, Figure 6 how the external tube 628 is connected between the first end fitting 612 and the further end fitting 622 via the respective purge valves 630, 602 at the respective ends of the tube 628 is illustrated. Thus, it will be appreciated how the annular region of the first flexible tube 604 can be selectively fluidly connected to the internal region (i.e. fluid communication region) of the external tube 628 via the further purge valve 630. It will be appreciated that the internal region of the external passage 628 is selectively connectable to the outlet 632 of the first purge valve 602 via the first purge valve 602. It will be appreciated that the first purge valve outlet 632 is exposed to the local environment and thus to the water pressure at the depth of submersion of the first purge valve outlet. Optionally, the first purge valve 602 can be fluidly connected to yet another flexible tube segment annular space via a fluid connection passage which can be connected inside a flange-to-flange end fitting connection between adjacent segments of flexible tube and through it, allowing higher pressure annulus fluid to flow through to a lower pressure annular space.

[0113] When the annulus pressure provided by the fluid in the annular region of the first flexible pipe exceeds the pressure associated with the inner region of the outer pipe 628 by a predetermined amount of pressure (that is, when the pressure differential across the further purge valve 630 exceeds the predetermined pressure differential), the further purge valve 630 will be urged, via the fluid pressure in the annular region of the first flexible pipe, into an open configuration in which the annular region of the first flexible pipe 604 and the inner region of the outer pipe 628 are fluidly connected. It will be appreciated that the inner region of the outer pipe can be a bore of the pipe, which bore can be a lumen. It will be appreciated that when the pressure provided by the fluid in the annular region of the first flexible pipe 604 does not exceed the pressure associated with the inner region of the outer pipe 628 by the predetermined amount, the further purge valve 630 remains in, or is urged (via the biasing element of the further purge valve and the pressure in the outer pipe) into, a closed configuration in which the fluid inlet and outlet of the further purge valve are fluidly disconnected. It will be appreciated that the excess pressure associated with opening the further purge valve 630 can be suitably selected or set to be close to zero, i.e. the pressure from the annular region of the first flexible pipe 604 can readily equilibrate with the pressure in the inner region of the outer pipe 628 without any significant pressure differential being present. In the event of damage to the outer pipe 628 or failure of the first purge valve 602, external water pressure will cause the further purge valve 630 to close and seal, thereby preventing water ingress into the annular space of the first flexible pipe 604.

[0114] It will be appreciated that, in the arrangement shown, Figure 6 In the arrangement shown, the further end fitting 622 is located at a shallower depth than the first end fitting 612, and therefore, the first purge valve 602 is located at a shallower depth than the further purge valve 630. It will therefore be appreciated that the local ambient pressure due to the water column is lower at the location at which the first end fitting (and therefore the further purge valve) is located. It will therefore be appreciated that, when the purge valve is provided at a shallower depth of submersion, the fluid in the annular region of the flexible pipe can be purged at a lower pressure. This is because the lower fluid pressure in the annular region of the flexible pipe will exceed the local ambient pressure at a shallower depth of submersion by a predetermined amount relative to a deeper depth of submersion.

[0115] Figure 6It is illustrated how gas from the annular region of the first flexible pipe can be vented at the location of the first purge valve due to the connection between the first purge valve 602 and the annular region of the first flexible pipe 604 via the external fluid pipe 628. It will be appreciated that during a pipe recovery operation when the pipe is being pulled in, the gas present in the annular region of the first flexible pipe can be purged via the first purge valve before the first flexible pipe has reached a location in the water column and is therefore urged into an open configuration, at which location the local ambient pressure is sufficiently low such that the annulus pressure (provided by the fluid in the annular region) can exceed the ambient by a predetermined amount. Thus, during recovery of the pipe, the flexible pipe can start to purge fluid earlier relative to what would otherwise occur in a conventional situation.

[0116] Figure 6 It is also illustrated how the first end fitting and the further end fitting can comprise a further purge valve 690 which is not connected to any external pipe and thus purges gas / fluid from the annular region of the flexible pipe when the pressure provided by the fluid exceeds the local ambient pressure at the depth of immersion of the further purge valve by a predetermined amount.

[0117] Figure 7a It is illustrated how the first purge valve 702 which is fluidically connectable to the annular region of the first flexible pipe can be supported on the end fitting 704 of the further flexible pipe 706. Figure 7a It is illustrated how the further end fitting 706 can comprise a valve support region 708. It will be appreciated that the valve support region can be integrally formed with the end fitting component (e.g. the outer cover / jacket or intermediate flange of the end fitting body). Alternatively, the valve support region 78 can be a separate unit which is connected to the end fitting. It will be appreciated that this can be achieved via bolting or the like. As Figure 7a It is illustrated that the valve support region comprises a rear opening for receiving an external pipe 712 which optionally extends from the first purge valve to the end fitting of the first flexible pipe via a further purge valve as Figure 6

[0118] Figure 7b It is illustrated how the first purge valve 702 which is fluidically connectable to the annular region of the first flexible pipe can be supported on the end fitting 704 of the further flexible pipe 706. Figure 7b It is illustrated how an adapter 740 which houses the first purge valve can be secured to the further end fitting. It will be appreciated that the adapter is a separate unit relative to the end fitting component. It will be appreciated that the adapter can be retrofitted to the end fitting, e.g. via use of an ROV or the like, which end fitting can already be deployed in a subsea environment.

[0119] Figure 7c ​An example is shown of how a first purge valve 702, which is fluidly connected to an annular region of a first flexible tube, can be supported on an end fitting 704 of a second flexible tube 706. Figure 7c An example is illustrated of how the additional end may include a channel 760 for receiving a tube extending from the inlet of the first purge valve to the first end fitting. Optionally, the remaining end of the tube connects to the outlet of an additional purge valve supported on the end fitting of the first flexible tube. It should be understood that, in addition to the channel extending through the additional end fitting, the tube extends from the additional end fitting to the first flexible member outside the conduit, in which the first flexible tube and the additional flexible tube are arranged.

[0120] Figure 8a and Figure 8b An example is shown of how a buoyancy module 802, including or supporting a purge valve 804, can be fluidly connected to the annular region of a flexible tube 806 of a conduit 808. For example... Figure 8a As shown, pipe 808 is at least partially disposed in seabed environment 810. Suitably, pipe 808 can be disposed in any underwater environment. Although Figure 6 The embodiment shows a first purge valve 602 supported on a separate end fitting 622, but here the purge valve 804 is supported on the buoyancy module 802, however, for connection to the first flexible tube 806 via the first end fitting of the first flexible tube ( Figure 6 The arrangement of the annular space (604) can be similar, wherein an additional purge valve (630) protects the annular space of the first flexible pipe from water ingress. As shown in Figure 8, the pipe 808 extends from the pipe end 812 at the surface 814 (sea level) of the seabed environment. It should be understood that the pipe end 812 can be a platform (e.g., a floating platform) or a vessel (e.g., a ship). Figure 8a The diagram illustrates how conduit 808 comprises multiple flexible tubes 806, each flexible tube including a segment of flexible tube body 816. It should be understood that each flexible tube 806 of conduit 808 is connected end-to-end to at least one adjacent flexible tube 806 via a corresponding end fitting 818. That is, a first flexible tube 806 of conduit 808 is connected to another flexible tube 806 of conduit 808 via a first end fitting 818 of the first flexible tube 806 and another end fitting 818 of another flexible tube 806, the first end fitting and the other end fitting 818 being connected via corresponding connector flanges of the end fittings (appropriately, via bolts). As shown in the figure, Figure 8a Pipeline 808 extends from pipe end 812 to seabed 820 and extends along the area of ​​seabed 820.

[0121] Figure 8a This illustrates how the external fluid conduit 822 can be attached to various end fittings 818 throughout the piping system.Figure 8a In the system, the outer tube is connected to an end fitting 818 of each flexible tube 806 of the conduit 808. Alternatively, it should be understood that any number of outer tubes can be connected to any number of end fittings. It should be understood that the outer tube 822 is connected to the corresponding end fitting 818 so as to enable fluid connection to the annular region of the flexible tube 806 including that particular end fitting 818. Figure 8a The tube 822 shown is a flexible tube made of polymer material and is movable to a certain extent in a localized environment. Suitably, the tube may be made of any other suitable material or one or more. Suitably, the tube is rigid. It should be understood that the outer tube 822 is connected to an end fitting 818, which is closest to the pipe end joint 812 in each flexible tube 806. Suitably, the outer tube 822 may be connected to any other end fitting 818 or at any other location in each flexible tube 806, provided that the outer tube 822 is fluidly connected to the annular region of the flexible tube 806.

[0122] like Figure 8a As shown, the outer tube 822 can extend to a corresponding buoyancy module 802, which floats above the flexible tube to which the tube 822 is connected. It should be understood that the buoyancy module contains a buoyancy substance (e.g., air or various low-density fluids) to enable the buoyancy module to float above the corresponding flexible tube. It should be understood that each buoyancy module includes or supports a purge valve 804. It should be understood that the purge valve 804 is related to... Figure 5b The purge valves described are substantially the same. Alternatively, any other suitable purge valve may be used. It should be understood that the fluid outlet of purge valve 804 is opened to the seabed environment 810 in which the buoyancy module 802 is arranged.

[0123] It should be understood that Figure 8a The outer tube 822 in the middle is in accordance with the reference. Figure 6 A similar manner as described is used to connect the outer tube 822 to the end fitting 818 of the corresponding flexible tube 806 via an additional purge valve. Therefore, the outer tube 822 can be selectively fluidly connected to the annular region of the corresponding flexible tube 806 to which it is connected. It should be understood that the additional purge valve may be substantially similar to the one described above. Figure 5bA purge valve is described. It should be appreciated that the additional purge valve is designed to be in a closed configuration (where the inlet and outlet of the additional purge valve are disconnected from fluidly connecting) without an external force, and is designed to be pushed into an open configuration when the pressure at the fluid inlet of the additional purge valve exceeds the pressure at the fluid outlet of the additional purge valve by a predetermined pressure. This predetermined pressure can be determined at the time of manufacture of the purge valve. It should be appreciated that prior to the additional purge valve purging annulus fluid into the outer pipe due to the pressure provided by the fluid in the annular region of the flexible pipe, the inner region of the outer pipe 628 (i.e. the bore of the outer pipe) contains air or another environmental fluid that can have entered the outer pipe during manufacture or during securing of the pipe and purge valve to the respective flexible pipe. However, it should be appreciated that after the additional purge valve is pushed into an open configuration due to the pressure in the annular space of the flexible pipe exceeding the pressure in the outer pipe provided by the fluid in the outer pipe, the outer pipe will instead contain fluid from the annular space. It should therefore be appreciated how the additional purge valve can purge fluid into the outer pipe, which is optionally gas that has permeated through the inner pipe of the flexible pipe into the annular region of the pipe.

[0124] It should be appreciated that the local environmental pressure at the floating position of each buoyancy module 802 is less than the local environmental pressure at the position of the flexible pipe 806 to which the buoyancy module is connected. It should therefore be appreciated how fluid can be purged from the outer pipe into the seafloor environment at a lower pressure at the immersion depth of the fluid outlet of a purge valve supported on a buoyancy module compared to a purge valve that is open to the environment at the immersion depth of an end fitting to which the outer pipe is connected. It should therefore be appreciated that as more fluid from the annular space is discharged into the outer pipe via the additional purge valve, the annulus fluid that has entered the outer pipe via the additional purge valve can provide a pressure that exceeds the local environmental pressure provided by the water column at the immersion depth of the fluid outlet of the purge valve (supported on a buoyancy module).

[0125] It should be appreciated that the fluid outlet of the additional purge valve supported on the respective end fitting and connected to the outer pipe is not exposed to the local environment, and thus the position of the valve (in the closed or open configuration) is responsive to the pressure in the annular region of the flexible pipe and the pressure in the outer pipe. It should be appreciated that the end fitting 818 can comprise (or support) one or more additional purge valves that are exposed to the local environment.

[0126] It should be appreciated that if the additional purge valve is not included in the end fitting, fluid from the annular space flows freely into the outer pipe. The outer pipe will therefore be at substantially the same pressure as the annular region of the flexible piece to which the outer pipe is connected. It should be appreciated that the higher the purge valve is provided in the water column, the lower the fluid pressure in the annular space, which will result in the purge valve purging / discharging fluid into the environment.

[0127] It will be appreciated that in Figure 8a In the arrangement shown, the outer tube is able to withstand the buoyancy provided by the buoyancy module. That is, the outer tube is sufficiently strong to act as a tether to tether the buoyancy module to the flexible pipe.

[0128] Figure 8b A buoyancy module 802 including / supporting a purge valve 804 is illustrated in more detail. As Figure 8b shown, the buoyancy module 802 includes a body 850 that houses a buoyant fluid (e.g. air). It will be appreciated that the buoyant fluid is a low density fluid. The purge valve 804 is arranged radially within the body 850. It will be appreciated that the body 850 is substantially annular and the purge valve 802 is arranged in a central cavity of the body 850. Suitably, the purge valve 804 can be located at any other suitable location on the body 850. As Figure 8b shown, the purge valve includes a fluid inlet 860 and a fluid outlet 870. The fluid outlet is connected to the outer tube 822. It will be appreciated that the fluid inlet 860 is fluidly connected to / communicates with an inner region or passage of the outer tube 822, which is a fluid communication passageway of the outer tube 822. It will be appreciated that the outer tube is an example of a lumen. Figure 8b It is shown how the fluid outlet 870 of the purge valve is open to the environment that is the subsea environment 810. It will therefore be appreciated how the fluid outlet 870 is exposed to the local ambient pressure provided by the water column (of the subsea environment 810) at the depth of submersion of the fluid outlet 870. It will therefore be appreciated how the fluid inlet 860 and the fluid outlet 870 are able to selectively connect in response to the pressure provided by the fluid in the inner region / passage of the outer tube 822 and the local ambient pressure at the depth of submersion of the fluid outlet 870.

[0129] Figure 9a Another buoyancy module 902 including or supporting a purge valve 904 is illustrated. It will be appreciated that Figure 9a the buoyancy module operates in substantially the same way as described with reference to Figure 8a and Figure 8b the buoyancy module 802. Figure 9a The buoyancy module 902 operates in substantially the same way as described with reference to Figure 8a and Figure 8bThe described buoyancy module 802 is substantially identical. The buoyancy module 904 includes a body 906 that includes a buoyancy material, e.g., a buoyancy fluid, such as air. The body 906 is substantially annular, and includes a central cavity 908 that extends through the body 906, and in which the purge valve 904 is disposed. It will be appreciated that the purge valve 904 includes a fluid inlet 910 that is connected to an outer tube 912, and a fluid outlet 914 that is exposed to the local environment (and thus to the pressure of the water column at the depth of submersion of the fluid outlet 914 in the environment). It will be appreciated that, Figure 9a The purge valve 904 of FIG. 9 is substantially identical to the purge valve described with reference to Figure 5a and Figure 5b It will be appreciated that any other suitable purge valve can be used instead, as appropriate.

[0130] Figure 9a It is illustrated how the buoyancy module 902 includes a frame element 916, or a framework, that extends partially through the body 906 of the buoyancy module 902 (and through the cavity 908). The frame element 916 is made of a metallic material. Optionally, any other suitable material can be used to make the frame element. Figure 9a It is illustrated how the purge valve 904 is supported on the frame element 916.

[0131] It will be appreciated that, Figure 9a It is illustrated how the outer tube 912 anchors the buoyancy module to the flexible pipe. Thus, the outer tube 912 is suitable for anchoring the buoyancy module 902, and can withstand the buoyancy provided by the buoyancy material in the buoyancy module 902. Suitably, the outer tube 912 is made of a polymeric material. Suitably, the outer tube 912 is made of a metallic material. Suitably, the buoyancy module 912 is made of a rigid material. Optionally, the buoyancy module is made of a flexible material.

[0132] Figure 9b It is illustrated yet another buoyancy module 950. It will be appreciated that, Figure 9b The buoyancy module 950 of FIG. 9 is similar to the buoyancy module 902 described with reference to Figure 9a Thus, the buoyancy module includes an annular body that contains a buoyancy material and includes an inner cavity in which a purge valve 956 is disposed. The purge valve 956 is supported on a frame element that extends through a cavity 954 of the body 952. Figure 9b It is also illustrated how the purge valve 956 includes a fluid inlet 960 that is connected to an outer fluid tube 962, and a fluid outlet 964 that is exposed to the local environment.

[0133] However, Figure 9b The buoyancy module 950 of FIG. 9 is tethered / anchored to the flexible pipe via an anchoring element 966 (or tethering element) that is not the outer tube 962.Figure 9b The frame element 958 is illustrated as including two protruding portions 968, each protruding from a bottom surface of the body 952 on an opposite side of the body 952 (as viewed from a perspective view). Figure 9b Figure 9b The respective end portions 970 of the anchoring elements 966 are each connected to the protruding portions 968 of the frame element 958. It will be appreciated that the anchoring elements 966 can loop around a region of the flexible pipe (as described in further detail with reference to Figure 10b The frame element 958 is illustrated as including two protruding portions 968, each protruding from a bottom surface of the body 952 on an opposite side of the body 952 (as viewed from a perspective view). Figure 9b The substantially parallel portions of the looped anchoring element 966 extend through the eyelets of the tethering elements 972, as illustrated.

[0134] Figure 10a The anchoring arrangement illustrated is useful for the buoyancy modules described with reference to Figure 10a , Figure 8a , Figure 8b or Figure 9a It will be appreciated that the anchoring arrangement illustrated can be used for the buoyancy modules described with reference to Figure 10a The end of the outer pipe is connected to the anchoring element 1006, as illustrated. It will be appreciated that the anchoring element is an example of a tethering element or anchoring arrangement. The anchoring element 1006 includes an anchoring block 1008 and an anchoring band or line or chain or the like 1010, as illustrated. Figure 10a Each end of the band or line or chain or the like is connected to (and terminates at) the anchoring block 1008, as illustrated. Figure 10a The anchoring arrangement illustrated is useful for the buoyancy modules described with reference to Figure 10a The anchoring arrangement illustrated is useful for the buoyancy modules described with reference to

[0135] Figure 10a A further outer pipe 1014 is illustrated as being connected between the anchoring block 1006 and a further purge valve 1016, which is supported on an end fitting 1018 of the flexible pipe 1002. It will be appreciated that the further purge valve 1016 is fluidly connectable to an annular region of the flexible pipe 1002. The further purge valve 1016 is fluidly connected to the annular region of the flexible pipe 1002 via the further outer pipe 1014, as illustrated. Figure 5a and Figure 5b ​The purge valve discussed is substantially the same; however, it should be understood that any other suitable purge valve may be used alternatively. Appropriately, no additional purge valve is included, and an additional outer tube 1014 is directly connected to the end fitting 1018 and fluidly connected to the annular region of the flexible tube 1002. It should be understood that the outer tube 1004 and the additional outer tube 1014 are fluidly connected via an anchor block 1008. That is, the anchor block 1008 includes a fluid communication passage that fluidly connects the outer tube 1004 and the additional outer tube 1014. Therefore, the outer tube 1004 can fluidly contact the annular region of the flexible tube 1002 via the anchor block 1008, the additional outer tube 1014, and the additional purge valve 1016 (and also via the fluid communication region of the end fitting 1018 fluidly connected to the inlet of the additional purge valve 1016).

[0136] Alternatively, it should be understood that outer tube 1004 and additional outer tube 1014 may be a single outer tube extending through or supported on anchor block 1008.

[0137] like Figure 10a As shown, the flexible tube 1002 is arranged on the seabed 1020 of the seabed environment 1022.

[0138] Figure 10b This illustrates how a buoyancy module, including a purge valve, can be anchored to a flexible tube 1050 via an anchoring element 1052 separate from the outer tube 1054. It should be understood that... Figure 10b The illustrated anchoring arrangement can be used to... Figure 9b The buoyancy module is anchored to the flexible tube 1050. Figure 10b This illustrates how the outer tube 1054 connects to an additional purge valve 1056 supported on the end fitting 1058 of the flexible tube 1050. It should be understood that the additional purge valve 1056 is related to the reference... Figure 5a and Figure 5b The purge valves described are substantially the same. Alternatively, any other suitable purge valve may be used. It should be understood that the additional purge valve is fluidly connected to the annular region of the flexible tube 1050. It should be understood that the outer tube 1054 is fluidly connected to the annular region of the flexible tube via an additional purge valve 1056. Alternatively, no additional purge valve is provided between the end fitting 1058 and the outer tube 1054, and the outer tube is always fluidly connected to the annular region of the flexible tube 1050. It should be understood that the remaining end of the outer tube 1054 is connected to a purge valve that is supported on or included in the buoyancy module, which is anchored to the flexible tube 1050.

[0139] like Figure 10b As shown, a band, line, or chain, etc., 1052 (which is an example of an anchoring element) surrounds the area of ​​the flexible tube body 1060 of the flexible tube 1050. Figure 10bThe substantially parallel regions of the endless strap or cord or chain or the like 1052 are shown as passing through the eyelets of the tethering elements 1062 to hold the substantially parallel regions of the endless strap or cord or chain or the like 1052 together. It will be appreciated that the ends of the endless strap or cord or chain or the like 1052 are connected, for example, via a Figure 9b The frame of the buoyancy module is shown as being connected to the buoyancy module, thereby anchoring the buoyancy module to the flexible pipe 1050.

[0140] Figure 10b The flexible pipe 1050 is shown as being arranged on the seabed 1070 of the subsea environment 1072.

[0141] Figure 11 A further example of how the buoyancy modules 1102 can be used to purge fluid that has accumulated in the annular regions of the flexible pipes 1106 of a pipeline arranged in a subsea environment 1110 is shown, each buoyancy module including a respective purge valve 1104. It will be appreciated that, Figure 11 The arrangement shown is similar to that described in relation to Figure 8a The arrangement shown is similar to that described in relation to Figure 11 The environment shown is a substantially shallow subsea environment. It will be appreciated that, Figure 11 A deep subsea environment is shown. As Figure 11 The pipeline 1108 is shown as extending from a pipeline termination point 1114 located at or near the surface 1116 of the subsea environment (at or around sea level) to the seabed 1118 and along a region of the seabed 1118, which can be a vessel (e.g. a ship or the like) or a platform (e.g. a floating platform or a fixed platform or the like). Figure 11 The pipeline 1108 is shown as including a plurality of flexible pipes 1106 connected in an end-to-end configuration via respective end fittings 1120 of the flexible pipes 1106. That is, the end fittings 1120 of the flexible pipes 1106 are connected to adjacent end fittings of adjacent flexible pipes.

[0142] Figure 11 The way in which each buoyancy module 1102 is connected to a respective flexible pipe 1106 via an external fluid pipe 1122 is shown, which is connected to a fluid inlet of a purge valve 1104 supported on the buoyancy module 1102. It will be appreciated that the remaining end of each external pipe 1122 is connected to a respective end fitting 1120 of the flexible pipe 1106 via a further purge valve supported on the end fitting, as described in relation to Figure 6 to Figure 1 0. It will be appreciated that the remaining end of the pipe is directly connected to the end fitting, without the use of a purge valve. Thus, it will be appreciated that each external pipe 1122 is selectively fluidly connectable (via a respective further purge valve) to an annular region of a respective flexible pipe 1106 to which a respective buoyancy module is anchored. As described in relation toFigure 8a As discussed, purge valve 1102 includes a fluid inlet in fluid communication with a respective outer pipe 1122 to which the purge valve 1104 is connected, and a fluid outlet exposed to the environment and thus to the local ambient pressure provided by the water column of the ambient environment 1110 at the depth of immersion of the fluid outlet. It will be appreciated that the depth of immersion of the fluid outlet of each purge valve is above the flexible pipe due to the buoyancy provided by the respective buoyancy module. It will be appreciated that, due to the lower local pressure at the location of each purge valve in the water column than the local pressure at the location of the respective flexible pipe 1106 in the water column (due to the shallower depth at which the buoyancy module 1102 is arranged compared to the respective flexible pipe 1106), the purge valve 1104 is able to purge fluid that has accumulated in the annulus when the annulus pressure is lower relative to a similar purge valve located at the depth of the flexible pipe 1106. This helps to prevent pipe damage due to pressure build-up in the annular region, and also allows for purging of gas at a faster rate (and earlier) than an equivalent purge valve at a lower depth of immersion. For example, if the fluid accumulated in the annular region of the flexible pipe is a corrosive gas, early and faster venting of the fluid from the annular region of the flexible pipe can help to extend the life of the pipe.

[0143] Figure 11 It is helpful to illustrate how the first buoyancy module 11021 floats on the surface 1116 of the subsea environment 1110. Thus, the outer pipe 1122 associated with the first buoyancy module is long enough to allow the first buoyancy module to reach the surface 1116. It will be appreciated that the fluid outlet of the purge valve 1104 supported on (or included in) the first buoyancy module 11021 is thus exposed to air at the surface 1116, and thus to atmospheric pressure rather than pressure associated with the water column. This helps to facilitate rapid purging of annulus fluid in the flexible pipe at relatively low annulus pressure (when the fluid pressure in the annular region exceeds atmospheric pressure by a predetermined threshold pressure).

[0144] Figure 11 It is helpful to illustrate how the further buoyancy module 11022 is located at a subsea location in the subsea environment 1110. Thus, Figure 11 It is helpful to illustrate how the purge valve 1104 included in (or supported on) the further buoyancy module 11022 purges fluid when the fluid pressure in the annular region of the respective flexible pipe 1106 to which the purge valve 1104 associated with the further buoyancy module 11022 is connected exceeds the water pressure at the depth of the further buoyancy module 11022 by a predetermined threshold pressure.

[0145] Figure 11It is also helpful to illustrate how fluid pressure in the annular regions of the flexible members can be controlled via purge valves 1104 supported on the buoyancy modules 1102. For example, by positioning a buoyancy module (which includes or supports a purge valve) at a shallower or deeper depth of the water column, the fluid pressure in the annular region of a particular flexible pipe 1106 can be decreased or increased, respectively. Thus, by providing a particular length of the anchoring system, the fluid pressure in the annular region of a particular flexible pipe can be determined. Further, it should be appreciated that the fluid pressure in the annular region of a particular flexible pipe can be adjusted by adjusting the height of the buoyancy module 1102 that includes or supports the purge valve 1104. For example, by increasing the height of the buoyancy module 1102 that includes or supports the purge valve 1102, the fluid pressure in the annular region of the flexible pipe remains at a lower pressure than when the buoyancy module 1102 (including or supporting the purge valve 1104) is at a lower / deeper depth of the water column. This is because when the buoyancy module 1102 is at a shallower position in the water column, the purge valve 1104 will begin to purge fluid from the annular region of the flexible pipe 1106 at a lower annulus pressure relative to the purge valve at a deeper position in the water column. Thus, the pressure in the annular region remains at a lower pressure. It should be appreciated that by utilizing buoyancy modules that include / support purge valves that are fluidly connectable to respective annular regions of respective flexible pipes, it is possible to vary the rate of fluid purging from the annular regions of different flexible pipes of the pipeline, and it is also possible to vary the pressure associated with the annular regions of each flexible pipe. For example, it can be desirable to purge fluid at a higher rate near wellhead locations where corrosive gases can be more prevalent, etc. Changes in the depth of the flexible pipes in the pipeline (e.g., due to seafloor topography, etc.) can also be taken into account to purge fluid from the annular regions of various flexible pipes of the pipeline to substantially balance the rate of fluid purging and fluid pressure in the annular regions of these flexible pipes.

[0146] Figure 12 A portion of the pipeline 1202 is illustrated in which the outer pipe 1204 has ruptured or burst and is therefore flooded. As Figure 12As shown, the conduit 1202 includes a first flexible tube 1206 and a further flexible tube 1208 connected in an end-to-end configuration. The outer tube 1204 is connected to a first purge valve 1210 that is supported on an end fitting 1212 of the further flexible tube 1208. The tube 1204 is also connected to an end fitting 1214 via a further purge valve 1216. It will be appreciated that the interior passage of the outer tube 1204 can be selectively fluidly connected to the annular region of the first flexible tube 1206 via the further purge valve 1216. It will be appreciated that, prior to burst, fluid from the annular region is purged into the outer tube via the further purge valve and is subsequently purged into the environment via the first purge valve 1210. It will be appreciated that the first purge valve can be located at a different location in the water column from the first flexible tube and, thus, can be associated with a different local ambient pressure (e.g., a lower ambient pressure) than the end fitting 1214 of the first flexible tube 1206, as already discussed with respect to Figure 6 to Figure 11 However, when the outer tube 1204 bursts, the further purge valve 1216 is exposed to the local ambient pressure of the water column at the further purge valve and, thus, the further purge valve prevents water from entering the first flexible tube 1206. Thus, pipe flooding is prevented by providing the further purge valve 1216 between the outer tube 1204 and the end fitting 1214 of the first flexible tube.

[0147] Figure 12 It is also illustrated how a plurality of further outer tubes 1240 can be arranged along the length of the conduit to purge fluid in the annular regions of a plurality of flexible tubes of the conduit.

[0148] Figure 13 A cross-sectional view of another purge valve 1304 is illustrated. It will be appreciated that, Figure 13 The purge valve 1304 shown can be used in any of the arrangements illustrated. Figure 6 to Figure 12 in the illustrated arrangements. Figure 13 It is helpful to illustrate how the purge valve can be arranged in a closed configuration 1308 and an open configuration 1312. As Figure 13 As illustrated, the purge valve includes a fluid inlet 1316 and a fluid outlet 1320. The inlet 1316 and the outlet 1320 are disposed on opposite sides of the valve, however, it will be appreciated that the inlet and the outlet can be disposed in any other suitable orientation. Figure 13 It is also shown how the purge valve 1304 includes a housing 1324 that includes a passage 1328 in which a movable member 1332 resides. It will be appreciated that the movable member is axially movable in the passage.

[0149] It will be appreciated that, in the closed configuration, the purge valve 1304 fluidly disconnects the inlet 1316 from the outlet 1320. It will be appreciated that, in the open configuration, the purge valve 1304 fluidly connects the inlet 1316 and the outlet 1320. As Figure 13As shown, the movable member 1332 includes a piston head 1336 at the end of the movable member 1332 closest to the outlet 1320. The piston head 1336 is positionable to abut a valve seat 1340, which is a portion of the housing that extends radially into the passage 1328. It should be understood that when the piston head is positioned to abut the valve seat, the valve seal and the piston head form a seal, such that the valve is in the closed configuration. It should also be understood that when the piston head is distal to the valve seat (not in contact with the valve seat), fluid can pass around the piston head, and thus the valve is in the open configuration. As Figure 13 As shown, the valve seat includes a tapered region of the passage that tapers radially inward and interfaces with a corresponding tapered radial surface of the piston head. Thus, the interface between the tapered region and the radial surface of the piston head provides the seal. Figure 13 It is also shown how a non-tapered region 1348 of the passage is wider than the piston head, such that in the open configuration, fluid can flow around the piston head, and thus the inlet and outlet are fluidly connected.

[0150] Figure 13 It is also shown how the valve includes a spring 1352 on a spring seat 1356, which is positioned proximate to the fluid inlet 1316. The remaining end of the spring 1352 is connected to the end of the movable member 1332 closest to the fluid inlet 1316. It should be understood that when the valve is in the closed configuration 1304, the spring 1352 is in a partially extended state and thus, the spring acts to bias the movable member toward the fluid inlet, biasing the valve to the closed configuration 1304. Thus, it should be understood that when the spring 1352 is in the open configuration 1308, the spring is further extended and thus acts to bias the movable member 1332 away from the outlet 1320, biasing the valve away from the open configuration. It should be understood that the spring is an example of a biasing element.

[0151] In use, it should be understood that the fluid inlet 1316 can be fluidly connected to an annular region of a flexible tube or to a fluid communication region of a lumen (which can be an outer tube or a hose element) and thus exposed to pressure provided by fluid at said annular region or fluid communication region. It should be understood that the fluid outlet 1320 can be fluidly connected to a local environment (which can be an underwater environment at a particular depth of submersion of the outlet) or to a fluid communication region of a lumen (which can be an outer tube or a hose element). Thus, the outlet 1320 is exposed to pressure provided by said environment (which can be a local ambient pressure provided by a water column at a particular depth of submersion of the outlet) or by fluid in said fluid communication region.

[0152] It should be understood that the restoring force (or biasing force) provided by the spring 1352 and the pressure at the outlet (provided by the environment or by the fluid) act to push the valve toward the closed configuration by pushing the movable member 1332 toward the fluid inlet 1316 (thus pushing the piston head 1336 abutting against the valve seat 1340). It should also be understood that the pressure provided by the fluid at the fluid inlet 1316 acts to push the valve toward the open configuration by pushing the movable member toward the fluid outlet (thus pushing the piston head away from the valve seat). Therefore, it should be understood that when the pressure provided by the fluid at the inlet crosses the lower surface of the piston head (from... Figure 13 The force (as shown in the perspective view) exceeds the force supplied by the fluid at the outlet (which may be the ambient fluid) across the top side surface of the piston head (from... Figure 13 The valve is pushed into the open configuration by the force (as shown in the perspective view) and the biasing force provided by the spring. It should also be understood that when fluid is supplied across the lower surface of the piston head (from the...) at the inlet... Figure 13 The force (as shown in the perspective view) is less than that supplied by the fluid at the outlet (which may be the ambient fluid) across the top side surface of the piston head (from... Figure 13 When the force (as shown in the perspective view) and the bias force provided by the spring are applied, the valve remains in the closed configuration. Therefore, it should be understood that the valve design (e.g., spring stiffness and / or piston head geometry) determines how much the fluid pressure at the inlet must exceed the fluid pressure at the outlet to push the valve into the open configuration.

[0153] Figure 14 A cross-sectional view of another purge valve 1404 is shown. It should be understood that... Figure 14 The purge valve 1404 shown can be used Figure 6 to Figure 12 In any of the illustrated arrangements. Figure 14 The purge valve is illustrated in closed configuration 1408 and open configuration 1412.

[0154] It should be understood that Figure 14 The illustrated purge valve 1404 is essentially similar to Figure 13 The valve 1304 is shown. However, as... Figure 14 As shown, the spring seat 1414 on which the spring 1418 rests is the radially outwardly expanding region of the sliding member 1420. The remaining end of the spring 1418 is disposed against the radially inwardly extending end seat 1422 of the valve housing 1426. It should be understood that when the valve is in the closed configuration 1408, the spring 1418 is in a partially compressed state. Therefore, it should be understood that when the valve is in the open configuration 1412, the spring is in a further compressed state. Thus, the spring biases the movable member toward the fluid inlet 1430, and thus biases the valve 1404 toward the closed configuration 1408.

[0155] With referenceFigure 13 Similar to the described valve 1304, when the fluid at the fluid inlet 1430 is below the piston head 1434 (from... Figure 14 When a force is applied to the surface (as shown in the perspective view) that exceeds the force provided by the fluid at fluid outlet 1438 and the biasing force provided by spring 1418, Figure 14 Valve 1404 is pushed into open configuration 1408. Therefore, it should be understood that in order to push the valve into open configuration, the pressure provided by the fluid at inlet 1430 (which may be, for example, fluid from an annular region of a flexible tube) must exceed the pressure at outlet 1438 (which may, for example, exceed the pressure of the local environment) by a predetermined amount (which is determined by the configuration of valve 1408, for example, the stiffness of the spring).

[0156] Throughout the detailed description and claims, the terms "comprising" and "containing," and variations thereof, mean "including but not limited to," and are not intended (and do not) exclude other parts, additives, components, integrals, or steps. Throughout the detailed description and claims, the singular encompasses the plural unless the context requires otherwise. Specifically, where indefinite articles are used, the description should be understood to consider both the plural and the singular unless the context requires otherwise.

[0157] Features, integrals, characteristics, or groups described in connection with a particular aspect, embodiment, or example of the invention should be understood to be applicable to any other aspect, embodiment, or example described herein, unless incompatible therewith. All features disclosed in this specification (including any appended claims, the abstract, and the drawings) and / or all steps of any method or process so disclosed may be combined in any combination, except that at least some of the features and / or steps are mutually exclusive combinations. The invention is not limited to any details of any of the foregoing embodiments. The invention extends to any novel feature or novel combination of features disclosed in this specification (including any appended claims, the abstract, and the drawings), or to any novel step or novel combination of steps of any method or process so disclosed.

[0158] The reader’s attention is drawn to all papers and documents filed concurrently with or prior to this specification in conjunction with this patent application that disclose a public examination of this specification, and the contents of all such papers and documents are incorporated herein by reference.

Claims

1. An apparatus for purging fluid from an annular region of a flexible pipe, the apparatus comprising: a first end fitting connected to an end region of a section of a flexible pipe body and comprising a fluid communication region fluidly connected to an annular region of the flexible pipe body; a first purge valve spaced apart from the first end fitting, the first purge valve comprising a first valve inlet and a first valve outlet, the first valve outlet being selectively fluidly connectable to the first valve inlet; and a pipe cavity extending between and in fluid communication with the fluid outlet of the first end fitting and the first valve inlet, the fluid outlet of the first end fitting being fluidly connectable to the fluid communication region; wherein the first purge valve is positionable spaced apart by a distance greater than 2 metres above the fluid outlet.

2. The apparatus defined in claim 1 further comprising: a hose element comprising the pipe cavity, the pipe cavity being disposed outside the flexible pipe body and the first end fitting.

3. The apparatus defined in claim 1 or claim 2 further comprising: a further purge valve comprising a further valve inlet and a further valve outlet, the further valve outlet comprising the fluid outlet and being selectively fluidly connectable to the further valve inlet such that the further purge valve selectively fluidly connects the fluid communication region with the pipe cavity, the further purge valve being optionally supported on a body of the first end fitting.

4. The apparatus defined in any preceding claim further comprising: a first flexible pipe comprising the first end fitting and the section of flexible pipe body, the first flexible pipe being disposed in a pipeline, the pipeline comprising a plurality of flexible pipes, each flexible pipe being disposed in an end-to-end configuration with an adjacent flexible pipe of the plurality of flexible pipes, the adjacent flexible pipes being connected together via respective end fittings of the adjacent flexible pipes; and the first purge valve being supported on a further end fitting of a further flexible pipe, or on a further section of flexible pipe body of a further flexible pipe, the further end fitting being optionally disposed above the first end fitting.

5. The apparatus defined in claim 4 further comprising: the further end fitting being disposed proximate to a flexible pipe recovery device relative to the first end fitting, the flexible pipe recovery device being optionally a winch device.

6. The apparatus defined in claim 4 or claim 5 further comprising: the first purge valve being connected to the further end fitting via an adaptor element, the adaptor element being securable to the further end fitting.

7. The apparatus defined in any one of claims 1 to 3 further comprising: ​ A buoyancy control element comprising a buoyancy body supporting the first purge valve, the buoyancy control element optionally comprising a rigid frame member providing support for a housing of the first purge valve.

8. The apparatus of claim 7, further comprising: a connection element securable to the rigid frame member for connecting the rigid frame member to the section of flexible pipe body, wherein a hose element comprising the lumen is secured in an unshown configuration.

9. The apparatus of claim 7 or claim 8, further comprising: the lumen extending through a plurality of hose elements and an anchoring element for anchoring the buoyancy control element to the section of flexible pipe body, a first hose element and a further hose element of the plurality of hose elements being separated by the anchoring element.

10. The apparatus of any preceding claim, wherein: the first end fitting is located in a subsea environment comprising a water column, the local pressure at the first valve outlet being optionally a local ambient pressure provided by the water column at the immersion depth of the valve outlet.

11. The apparatus of any preceding claim, further comprising: the first purge valve being configured to fluidly connect the first valve inlet and the first valve outlet when the pressure at the first valve inlet provided by fluid in the lumen exceeds the local pressure at the first valve outlet by a first predetermined pressure, and optionally the first purge valve being configured to fluidly disconnect the first valve inlet and the first valve outlet when the pressure difference between the pressure at the first valve inlet provided by fluid in the lumen and the local pressure at the first valve outlet is less than a first predetermined pressure difference.

12. The apparatus of any of claims 3 to 11, further comprising: the further purge valve being configured to fluidly connect the further valve inlet and the further valve outlet when the pressure at the further valve inlet provided by fluid in the annulus exceeds the pressure at the further valve outlet by a further predetermined pressure, and to fluidly disconnect the further valve inlet and the further valve outlet when the pressure difference between the pressure at the further valve inlet and the pressure at the further valve outlet is less than a further predetermined pressure difference.

13. A method of purging fluid from an annulus of a flexible pipe, the method comprising the steps of: conveying fluid from an annulus of a flexible pipe comprising at least one end fitting through a fluid outlet of the end fitting fluidly connectable to the annulus and into a lumen in fluid communication with the fluid outlet; conveying the fluid through the lumen and to a first valve inlet of a first purge valve, the first purge valve being spaced apart from the first end fitting and including a first valve outlet that is selectively fluidly connectable to the first valve inlet, the first purge valve being spaced apart above the fluid outlet by a distance greater than 2 meters; fluidly connecting the first valve inlet and the first valve outlet when a pressure provided by the fluid at the first valve inlet exceeds a local pressure at the first valve outlet by a first predetermined pressure; and conveying the fluid from the first valve inlet out of the first valve outlet, thereby purging fluid from the annular region.

14. The method of claim 13, further comprising the steps of: providing the fluid at a further fluid inlet of a further purge valve prior to conveying the fluid through the fluid outlet, the further purge valve being supported on the end fitting and including a further valve outlet, the further valve outlet including the fluid outlet, the further valve outlet being selectively fluidly connectable to the further fluid inlet; and fluidly connecting the further valve inlet and the further valve outlet when a pressure provided by the fluid at the further valve inlet exceeds a pressure at the further valve outlet by a further predetermined pressure.

15. The method of claim 13 or 14, further comprising the step of: arranging the first purge valve in a subsea environment including a water column such that the local pressure at the first valve outlet is a local ambient pressure provided by the water column at a depth of submersion of the first valve outlet.

16. The method of any one of claims 13 to 15, further comprising the step of: arranging the end fitting in a subsea environment and at a depth that is deeper than the depth of submersion of the first valve outlet such that the first valve inlet and the first valve outlet are selectively fluidly connectable in response to a pressure differential between a pressure in the annular region provided by the fluid and the local ambient pressure at the depth of submersion of the first valve outlet.

17. The method of any one of claims 13 to 16, further comprising the step of: urging the first purge valve in an upward direction via a buoyancy provided by a buoyancy control element such that the first purge valve is located above the flexible pipe, the buoyancy control element including a buoyant body that supports the first purge valve.

18. An apparatus for limiting fluid pressure in an annular region of a flexible pipe, the apparatus comprising: a flexible pipe including an end fitting at an end region of a section of a flexible pipe body and disposed in a subsea environment including a water column, the end fitting including a fluid communication region fluidly connected to an annular region of the flexible pipe; a first purge valve spaced apart from and disposed above the flexible pipe, the first purge valve including a first valve inlet and a first valve outlet, the first valve outlet being selectively fluidly connectable to the first valve inlet; and a lumen extending between and fluidly connecting the first valve inlet and a fluid outlet of the end fitting, the fluid outlet of the end fitting being fluidly connectable to the fluid communication zone, the first purge valve being spaced apart above the fluid outlet by a distance greater than 2 meters; wherein the first purge valve is configured to fluidly connect the first valve inlet and the first valve outlet to selectively purge fluid from the annular zone when a pressure at the first valve inlet provided by fluid from the annular zone exceeds a local ambient pressure at the first valve outlet by a first predetermined pressure, and thereby limit the fluid pressure in the annular zone.

19. The apparatus of claim 18, further comprising: the first purge valve disposed in the underwater environment such that the local ambient pressure at the first valve outlet is a water pressure provided by the water column at a depth of submersion of the first valve outlet.

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