Purging fluid

Abstract

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

Description

[0001] PURGING FLUID

[0002] The present invention relates to a method and apparatus for purging fluid in an annulus region of a flexible pipe. In particular, but not exclusively, the present invention relates to, during use or retrieval of a pipeline including a number of flexible pipes disposed in an end-to-end configuration, purging gas that has accumulated in an annulus region of a flexible pipe to a position in an environment associated with a lower local environmental pressure than the position at which the flexible pipe is located.

[0003] Flexible pipes are widely used in the oil and gas industry in offshore applications for the transportation of oil, gas, water, or other fluids from one location to another. Flexible pipe is particularly useful in connecting sea-level supporting structures and subsea locations (which may be deep underwater, say 1000 metres or more), where the pipe may act as a riser. A flexible pipe is generally formed as an assembly of flexible pipe body and one or more end fittings. Flexible pipe body may have an internal diameter of typically up to around 0.6 metres (e.g. diameters may range from 0.05 m up to 0.6 m). Due to their location, flexible pipes are exposed to a range of challenging conditions that may have high pressures, seawater, high tensile strain, and corrosive environments. Flexible pipe body is therefore composed of several concentric polymeric, metallic, and / or composite layers. For example, pipe body may include polymer and metal layers, or polymer and composite layers, or polymer, metal and composite layers. Layers may be formed from a single piece such as an extruded tube or by helically winding one or more wires at a desired pitch or by connecting together multiple discrete hoops that are arranged concentrically side-by-side. Depending upon the layers of the flexible pipe used and the type of flexible pipe some of the pipe layers may be bonded together or remain unbonded. The polymeric layers generally provide sealing from fluid ingress and the metallic layers structural rigidity.

[0004] Some flexible pipes have been used for deep water (less than 3,300 feet (1 ,005.84 metres)) and ultra-deep water (greater than 3,300 feet) developments. It is the increasing demand for oil which is causing exploration to occur at greater and greater depths (for example in excess of 8202 feet (2500 metres)) where environmental factors are more extreme. For example, in such deep and ultra-deep water environments, ocean floor temperature increases the risk of production fluids cooling to a temperature that may lead to pipe blockage. In practice, flexible pipes are conventionally designed to perform at operating temperatures of -30°C to +130°C and pipe body are being developed for even more extreme temperatures. Increased depths also increase the pressure associated with the environment in which the flexible pipe must operate. For example, a flexible pipe may be required to operate with external pressures ranging from 0.1 MPa to 30 MPa acting on the pipe. Equally, transporting oil, gas or water may well give rise to high pressures acting on the flexible pipe from within, for example with internal pressures ranging from zero to 140 MPa from bore fluid acting on the pipe. As a result, the need for high levels of performance and environmental resilience from certain layers such as a pipe carcass or a pressure armour or a tensile armour layer of the flexible pipe body is increased. It is noted for the sake of completeness that flexible pipe may also be used for shallow water applications (for example less than around 500 metres depth) or even for shore (overland) applications.

[0005] The innermost layers of flexible pipe body often include an inner sheath which can be an extruded non-porous polymer layer that confines a bore fluid to its internal circumference, and often a carcass, a spirally wound interlocking metal structure which forms the very innermost layer. The carcass prevents the 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.

[0006] The outermost layer of a flexible pipe is the outer sheath, an extruded non-porous polymer layer that protects the pipe’s structural elements from the environment around the flexible pipe and prevents the ingress of seawater.

[0007] For some flexible pipes that include intermediate polymer layers flexible pipe body may include multiple annuli. For many flexible pipes though only an outer and an inner polymer layer is included. An annulus of such a flexible pipe is a region between the innermost fluid containing layer and the outermost fluid containing layer. The innermost layers in the annulus region are pressure armour layers, which are made of helically wound flattened metallic wires arranged at a lay angle close to 90°. Neighbouring wound wires in the pressure armour layer interlock to control the gap between windings. Pressure armour is designed to withstand hoop stress in the pipe wall, which is caused by the bore fluid pressure. Pairs of tensile armour layers are also located in the annulus, and these are cross-wound radially outside the pressure armour layer. Tensile armour layers are often made of slightly flattened rectangular metallic wires arranged at a lay angle of about 30 - 55°. Tensile armour layers support the weight of all internal pipe layers and transfer the resulting tensile stress to the sea-level supporting structures. The annulus may also have other layers such as anti-wear and anti-birdcaging tapes, and thermally insulating layers. Carbon steel wires in the annulus are thus often a feature of flexible pipes for subsea environments.

[0008] Conventionally in the end fitting, flexible pipe body is typically terminated by sealing and securing ends of polymer or composite layers and securing any pressure armour windings and securing the tensile armour wires. The annulus which extends along the flexible pipe body segment thus extends into a region within the end fitting. In configurations where two flexible pipes are joined end-to-end to form a pipeline there is no fluid connection between the annulus in one flexible pipe and the annulus in the other flexible pipe.

[0009] The annulus of flexible pipe body is usually void of fluid upon delivery, with the exception sometimes of small amounts of lubrication used during the manufacturing process. That is to say, when a flexible pipe is laid for example subsea during installation, the annulus of the flexible pipe is not intended to contain quantities of gas or liquid. Over time after installation, the annulus of the flexible pipe tends to fill up with fluid. This is due to gases and possibly liquids diffusing from seawater through the outer sheath into the annulus due to factors such as pressure, temperature, outer sheath material, outer sheath thickness, and the like. Sometimes gases and liquids may likewise or alternatively diffuse from the bore fluid through the inner sheath (often a barrier layer or liner) into the annulus due to the above factors. This can be particularly the case when bore fluids contain high proportions of certain gasses and may be particularly an issue for a flexible pipe of a pipeline geographically close to a well head.

[0010] Consequentially, the annulus of a flexible pipe that has been sat subsea for a period of time may build up annulus gases to a high pressure. Were the annulus gases allowed to increase in pressure unrestricted, the pressure of annulus gases on the inside of the outer sheath could exceed the hydrostatic pressure of seawater on the outside of the outer sheath to such a degree that the outer sheath bursts (the actual annulus over-pressure, with respect to the external hydrostatic pressure, may vary depending on the structure of the outer sheath layer of the pipe and whether there is any reinforcement over or incorporated in that layer). To mitigate this problem, a minimum of two, and typically three pressure release valves are often installed in each end fittings of flexible pipes, as prescribed by the API 17J standard for unbonded flexible pipe. Thus, when annulus fluid pressure exceeds a threshold above hydrostatic seawater pressure (typically 2-3 bar), the valve opens and “purges” to relieve the pressure in the annulus. The valve therefore acts as a purge valve and helps to prevent the outer sheath from bursting due to pressure in the annulus. The maximum flow rate of the valve, the release pressure of the valve, and other such parameters may be chosen to limit seawater ingress to the annulus during purging.

[0011] At some point it may be necessary to retrieve flexible pipes that have been installed in a subsea environment. For example, when the flexible pipes are no longer being used; to redeploy the flexible pipe in another location; perform modifications, or the like. During the retrieval process, flexible pipe body is pulled up from its installation location and reeled into a reel on a Pipe Lay Support Vessel (PLSV) or is otherwise lifted. As discussed above, if the flexible pipes have been lying in a subsea environment for a period of time, the annulus of the flexible pipes may contain gases and / or liquids under pressure. As a flexible pipe is raised from its installation location underwater towards surface level, hydrostatic pressure on the outside of the outer sheath of the flexible pipe will decrease at roughly 1 bar (O.IMpa) per 10m reduction in water depth, whilst annulus gas pressure is unchanged by water depth. Therefore, as the flexible pipe body is raised, the hydrostatic pressure on the outside of the outer sheath may decrease relative to the annulus pressure on the inside of the outer sheath. As described above, when the annulus pressure exceeds a threshold above the hydrostatic pressure, valves in the end fitting of the flexible pipe will open to release excess pressure. If the flexible pipe is raised towards surface level faster than the valves can release excess pressure, the outer sheath of the flexible pipe outer sheath may burst due to the excess annulus pressure.

[0012] Conventionally, a rate of retrieval during pipe retrieval to the PLSV is limited by the capacity of the pressure release valves in the end fitting of a flexible pipe to reduce annulus pressure. Sometimes, pipe retrieval rate may be set at a fixed safe value to give the valves time to reduce annulus pressure, if needed. At other times, a camera on a Remotely Operated Vehicle (ROV) might be used to inform when to reduce the pipe retrieval rate when valves in the end fitting are open by monitoring for bubbles. Such pipe retrieval rates are often chosen conservatively with a large margin for error, as annulus pressure, when above the threshold for purging, may vary considerably, and there may be uncertainty over how many of the pressure release valves are open and hence what volume of gas is being released, thus affecting the time required for annulus pressure to be safely reduced. As a result, pipe retrieval can be an unduly slow process which increases costs and down time relative to desired speeds. Furthermore, there is a risk of damage to a flexible pipe when retrieving a pipeline that includes such flexible pipes from an underwater environment, for example a subsea environment. If a pipeline is retrieved too fast, the outer sheath of a flexible pipe can burst due to the pressure of fluid (for example gas) that has accumulated in the annulus region of a flexible pipe and the reduced environmental pressure (pressure associated with the water column of an underwater environment) as the flexible pipe is pulled up towards the surface of the underwater environment. The increasing pressure differential between the annulus region and the local environment at a depth of the flexible pipe (which may be an instantaneous depth that constantly varies as the pipe is retrieved) can cause a flexible pipe to rupture. It is thus often necessary to allow regions of flexible pipes to rest at particular depths during retrieval of a pipeline to allow the fluids accumulated in the annulus region of a flexible pipe to be purged (or to vent into the environment). This can significantly increase the time taken to retrieve a pipeline including a number of flexible pipes and can increase costs associated therewith.

[0013] It is an aim of the present invention to at least partly mitigate one or more of the above- mentioned problems.

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

[0015] It is an aim of certain embodiments of the present invention to provide a method and apparatus for early purging of fluids accumulated in an annulus region of a flexible pipe during retrieval of a pipeline that includes a plurality of flexible pipes.

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

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

[0018] It is an aim of certain embodiments of the present invention to purge fluid from an annulus region of a flexible pipe in an underwater environment at a lower local environmental pressure than the pressure provided by a water column at a position in the water column at which said flexible pipe is arranged. It is an aim of certain embodiments of the present invention to fluidly connect an annulus region of a flexible pipe disposed in an underwater environment with a shallower region of an underwater environment relative to the position of the flexible pipe itself.

[0019] It is an aim of certain embodiments of the present invention to provide a buoyancy module that includes or supports a purge valve that is fluidly connectable to an annulus region of a flexible pipe that is arranged below (at a deeper submerged depth) that the buoyancy module in an underwater environment, and to which the buoyancy module is anchored.

[0020] It is an aim of certain embodiments of the present invention to support a purge valve that is fluidly connectable to an annulus region of a first flexible pipe on a further flexible pipe (for example on an end fitting of a further flexible pipe) that optionally is located at a shallower submerged depth off an underwater environment than the first flexible pipe.

[0021] According to a first aspect of the present invention there is provided apparatus for purging fluid from an annulus region of a flexible pipe, comprising: a first end fitting connected to an end region of a segment of flexible pipe body and comprising a fluid communication region that is fluidly connected to an annulus region of the flexible pipe body; a first purge valve that is spaced apart from the first end fitting comprising a first valve inlet and a first valve outlet that is selectively fluidly connectable to the first valve inlet; and a lumen extending between and in fluid communication with, a fluid outlet of the first end fitting that is fluidly connectable to the fluid communication region, and the first valve inlet.

[0022] Aptly the first purge valve is spaced apart above the fluid outlet optionally by a distance of more than 2 meters.

[0023] Aptly the apparatus further comprises a hose element comprising the lumen disposed outside of the flexible pipe body and the first end fitting.

[0024] Aptly the apparatus further comprises a further purge valve comprising a further valve inlet and a further valve outlet that comprises the fluid outlet and is selectively fluidly connectable to the further valve inlet so that the further purge valve selectively fluidly connects the fluid communication region and the lumen. Aptly the further purge valve is supported on a body of the first end fitting.

[0025] Aptly the apparatus further comprises a first flexible pipe comprising the first end fitting and the segment of flexible pipe body, the first flexible pipe being disposed in a pipeline that comprises a plurality of flexible pipes each 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 is supported on a further end fitting of a further flexible pipe, or is supported on a further segment of flexible pipe body of a further flexible pipe.

[0026] Aptly the further end fitting is disposed above the first end fitting.

[0027] Aptly the further end fitting is disposed proximate to a flexible pipe retrieval device, that optionally is a winching device, relative to the first end fitting.

[0028] Aptly the first purge valve is connected to the further end fitting via an adaptor element that is securable to the further end fitting.

[0029] Aptly the apparatus further comprises a buoyancy control element that comprises a buoyancy body that supports the first purge valve.

[0030] Aptly the apparatus further comprises a rigid frame member in the buoyancy body that provides support for a housing of the first purge valve.

[0031] Aptly the apparatus further comprises a connecting element securable to the rigid frame member for connecting the rigid frame member to the segment for flexible pipe body wherein a hose element that comprises the lumen is secured in a non-taught configuration.

[0032] Aptly the lumen extends through a plurality of hose elements and an anchoring element for anchoring the buoyancy control element to the segment of flexible pipe body, a first and further hose element of the plurality of hose elements being separated by the anchoring element.

[0033] Aptly the first end fitting is located in an underwater environment and the first purge valve is located in the underwater environment at a shallower depth than first the end fitting, the underwater environment comprising a water column. Aptly a local pressure at the first valve outlet is a local environmental pressure provided by the water column at a submerged depth of the valve outlet.

[0034] Aptly 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 a fluid in the lumen exceeds a local pressure at the first valve outlet by a first predetermined pressure.

[0035] Aptly the first purge valve is configured to fluidly disconnect the first valve inlet and the first valve outlet when a pressure differential between pressure at the first valve inlet provided by a fluid in the lumen, and a local pressure at the first valve outlet is less than a first predetermined pressure differential.

[0036] Aptly 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 a fluid in the annulus 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 differential between the pressure at the further valve inlet and the further valve outlet is less than a further predetermined pressure differential.

[0037] According to a second aspect of the present invention there is provided a method of purging fluid from an annulus region of a flexible pipe, comprising the steps of: communicating fluid from an annulus region of a flexible pipe that comprises at least one end fitting, through a fluid outlet of the end fitting, the fluid outlet being fluidly connectable to the annulus region, and into a lumen that is in fluid communication with the fluid outlet; communicating the fluid through the lumen and to a first valve inlet of a first purge valve comprising a first valve outlet that is selectively fluidly connectable to the first valve inlet; 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, fluidly connecting the first valve inlet and the first valve outlet; and; communicating the fluid from the first valve inlet out of the first valve outlet thereby purging fluid from the annulus region.

[0038] Aptly the method further comprises the steps of, prior to transporting the fluid through the fluid outlet, providing the fluid at a further fluid inlet of a further purge valve that is supported on the end fitting and comprises a further valve outlet, comprising the fluid outlet, that is selectively fluidly connectable to the further fluid inlet; and 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, fluidly connecting the further valve inlet and further valve outlet.

[0039] Aptly the method further comprises the steps of arranging the first purge valve in an underwater environment that comprises a water column so that that the local pressure at the first valve outlet is a local environmental pressure provided by the water column at a submerged depth of the first valve outlet.

[0040] Aptly the method further comprises the steps of arranging the end fitting in an underwater environment and at a depth that is deeper than the submerged depth of the first valve outlet so that the first valve inlet and the first valve outlet are selectively fluidly connectable responsive to a pressure differential between a pressure in the annulus region provided by the fluid and the local environmental pressure at the submerged depth of the first valve outlet.

[0041] Aptly the method further comprises the steps of, via a buoyancy force provided by buoyancy control element comprising a buoyancy body that supports the first purge valve, urging the first purge valve in an upward direction so that that the first purge valve is located above the flexible pipe.

[0042] According to a third aspect of the present invention there is provided a method of purging fluid from an annulus region of an underwater flexible pipe during retrieval of said flexible pipe, comprising the steps of: urging an end region of a flexible pipe towards a floating platform at a flexible pipe retrieval velocity thereby lifting the flexible pipe through water; and as the flexible pipe is lifted, purging fluid from an annulus region of the flexible pipe through a first purge valve that is spaced apart from and disposed above the flexible pipe via a fluid communication pathway that extends between the annulus region and the first purge valve, when a pressure, provided by fluid from the annulus region, at a first valve inlet of the first purge valve exceeds a water pressure at a submerged depth of a first valve outlet of the first purge valve.

[0043] According to a fourth aspect of the present invention there is provided apparatus for limiting pressure of fluid in an annulus region of a flexible pipe, comprising: a flexible pipe comprising an end fitting at an end region of a segment of flexible pipe body and disposed in an underwater environment that comprises a water column, the end fitting comprising a fluid communication region that is fluidly connected to an annulus region of the flexible pipe; a first purge valve spaced apart from and disposed above the flexible pipe comprising a first valve inlet and a first valve outlet that is selectively fluidly connectable to the first valve inlet; and a lumen extending between, and fluidly connected to, the first valve inlet and a fluid outlet of the end fitting that is 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 when a pressure at the first valve inlet, provided by fluid from the annulus region, exceeds a local environmental pressure at the first valve outlet by a first predetermined pressure to selectively purge fluid from the annulus region and thereby limit the pressure of fluid in the annulus region.

[0044] Aptly the first purge valve is disposed in the underwater environment so that the local environmental pressure at the first valve outlet is a water pressure provided by the water column at a submerged depth of the first valve outlet.

[0045] Certain embodiments of the present invention provide reduced downtime when retrieving a pipeline from an underwater environment due to a need to allow fluids to vent out of an annulus region of one or more flexible pipes of said pipeline.

[0046] Certain embodiments of the present invention provide reduced risk of flexible pipe damage, for example bursting (rupture of an outer sheath of said pipe), due to pressures associated with fluid accumulated in the annulus region of said pipe.

[0047] Certain embodiments of the present invention provide a purge valve that is fluidly connectable to an annulus region of a flexible pipe via an external fluid tube or other such fluid communication passageway, and is disposed at a shallow submerged depth of an underwater environment relative to the flexible pipe itself.

[0048] Certain embodiments of the present invention provide an increased rate of fluid venting / purging from an annulus region of a submerged flexible pipe.

[0049] Certain embodiments of the present invention provide pre-emptive purging of fluid from an annulus region of a flexible pipe during retrieval of a flexible pipe from an underwater environment. Certain embodiments of the present invention provide a fluid communication passageway between an annulus region of a first flexible pipe and a purge valve located on a further flexible pipe, for example on an end fitting of the further flexible pipe.

[0050] Certain embodiments of the present invention provide a fluid communication passageway between a purge valve supported on a buoyancy module and an annulus region of a flexible pipe. Optionally the buoyancy module can have a selectable buoyancy to raise or lower the module and the associated purge valve according to need.

[0051] Certain embodiments of the present invention reduce the pressure of a fluid in an annulus region of a flexible pipe necessary to purge fluid from said annulus region into the environment at a particular submerged depth of said flexible pipe in an underwater environment.

[0052] Certain embodiments of the present invention provide an annulus gas passageway from the end of one flexible pipe section to an end of another flexible pipe section, past a section of thermoplastic composite pipe through which no annulus gas can be transmitted internally to the pipe wall (i.e. through an annulus).

[0053] Embodiments of the present invention will now be described hereinafter, by way of example only, with reference to the accompanying drawings in which:

[0054] Figure 1 illustrates flexible pipe body;

[0055] Figure 2 illustrates certain uses of flexible pipes as a pipeline and pipe retrieval;

[0056] Figure 3 illustrates an end of a flexible pipe where flexible pipe body is terminated in an end fitting;

[0057] Figure 4 illustrates a portion of an end fitting that includes a purge valve;

[0058] Figure 5a illustrates how a purge valve can be arranged on an end fitting of a flexible pipe;

[0059] Figure 5b illustrates a purge valve in more detail and in cross section; Figure 6 illustrates how a purge valve that is fluidly connectable to an annulus region of a first flexible pipe can be supported on an end fitting of a further flexible pipe that is located more proximate to the surface of a subsea environment relative to the first flexible pipe;

[0060] Figure 7a illustrates a first example of how a purge valve that is fluidly connectable to an annulus region of a first flexible pipe can be supported on an end fitting of a further flexible Pipe;

[0061] Figure 7b illustrates a further example of how a purge valve that is fluidly connectable to an annulus region of a first flexible pipe can be supported on an end fitting of a further flexible Pipe;

[0062] Figure 7c illustrates a still further example of how a purge valve that is fluidly connectable to an annulus region of a first flexible pipe can be supported on an end fitting of a further flexible Pipe;

[0063] Figure 8a illustrates how a purge valve can be arranged on a buoyancy module that floats above a flexible pipe that includes an annulus region to which the purge valve is fluidly connectable;

[0064] Figure 8b illustrates how a purge valve can be arranged on a buoyancy module in more detail;

[0065] Figure 9a illustrates a first buoyancy module on which a purge valve is arranged;

[0066] Figure 9b illustrates a further buoyancy module on which a purge valve is arranged;

[0067] Figure 10a illustrates a first arrangement for anchoring a buoyancy module, on which a purge valve is arranged, to a flexible pipe;

[0068] Figure 10b illustrates a further arrangement for anchoring a buoyancy module, on which a purge valve is arranged, to a flexible pipe;

[0069] Figure 11 illustrates how buoyancy modules that include purge valves can be arranged in an underwater environment and on the surface of an underwater environment; Figure 12 illustrates how a purge valve arranged on an end fitting and connected to an external fluid tube can prevent flooding of an annulus region of a flexible pipe if the external fluid tube is damaged in use;

[0070] Figure 13 illustrates a different purge valve in cross section; and

[0071] Figure 14 illustrates a cross sectional view of another purge valve.

[0072] In the drawings like reference numerals refer to like parts.

[0073] Throughout this description, reference will be made to a flexible pipe. It is to be appreciated that certain embodiments of the present invention are applicable to use with a wide variety of flexible pipe. For example, certain embodiments of the present invention can be used with respect to flexible pipe body and associated end fittings of the type which is manufactured according to API 17J. Such flexible pipe is often referred to as unbonded flexible pipe. Other embodiments are associated with other types of flexible pipe.

[0074] It will be understood that the illustrated flexible pipes are an assembly of a portion of flexible pipe body and one or more end fittings in each of which a respective end of the pipe body is terminated. Figure 1 illustrates how pipe body 100 is formed from a combination of layered materials that form a pressure-containing conduit. Although a number of particular layers are illustrated in Figure 1 , it is to be understood that certain embodiments of the present invention are broadly applicable to coaxial pipe body structures including two or more layers manufactured from a variety of possible materials. The pipe body may include one or more layers comprising composite materials, forming a tubular composite layer. It is to be further noted that the layer thicknesses are shown for illustrative purposes only. As used herein, the term “composite” is used to broadly refer to a material that is formed from two or more different materials, for example a material formed from a matrix material and reinforcement fibres.

[0075] A tubular composite layer is thus a layer having a generally tubular shape formed of composite material. Alternatively, a tubular composite layer is a layer having a generally tubular shape formed from multiple components one or more of which is formed of a composite material. The layer or any element of the composite layer may be manufactured via an extrusion, pultrusion or deposition process, or by a winding process in which adjacent windings of tape which themselves have a composite structure are consolidated together with adjacent windings. The composite material, regardless of manufacturing technique used, may optionally include a matrix or body of material having a first characteristic in which further elements having different physical characteristics are embedded. That is to say elongate fibres which are aligned to some extent or smaller fibres randomly orientated can be set into a main body or spheres or other regular or irregular shaped particles can be embedded in a matrix material, or a combination of more than one of the above. Aptly the matrix material is a thermoplastic material, aptly the thermoplastic material is polyethylene or polypropylene or nylon or PVC or PVDF or PFA or PEEK or PTFE or alloys of such materials with reinforcing fibres manufactured from one or more of glass, ceramic, basalt, carbon, carbon nanotubes, polyester, nylon, aramid, steel, nickel alloy, titanium alloy, aluminium alloy or the like or fillers manufactured from glass, ceramic, carbon, metals, buckminsterfullerenes, metal silicates, carbides, carbonates, oxides or the like.

[0076] The pipe body 100 illustrated in Figure 1 includes an internal pressure sheath 110 which acts as a fluid retaining layer and comprises a polymer layer that ensures internal fluid integrity. The layer provides a boundary for any conveyed fluid. It is to be understood that this layer may itself comprise a number of sub-layers. It will be appreciated that when a carcass layer 120 is utilised the internal pressure sheath is often referred to by those skilled in the art as a barrier layer. In operation without such a carcass (so-called smooth bore operation) the internal pressure sheath may be referred to as a liner. A barrier layer 110 is illustrated in Figure 1.

[0077] It is noted that a carcass layer 120 is a pressure resistant layer that provides an interlocked construction that can be used as the innermost layer to prevent, totally or partially, collapse of the internal pressure sheath 110 due to pipe decompression, external pressure, and tensile armour pressure and mechanical crushing loads. The carcass is a crush resistant layer. It will be appreciated that certain embodiments of the present invention are thus applicable to ‘rough bore’ applications (with a carcass). Aptly the carcass layer is a metallic layer. Aptly the carcass layer is formed from stainless steel, corrosion resistant nickel alloy or the like. Aptly the carcass layer is formed from a composite, polymer, or other material, or a combination of materials and components. The carcass layer is usually radially positioned within the barrier layer.

[0078] The carcass layer is a “layer” in the sense that a radially innermost and outermost surface are created in single pass at a single manufacturing node. The single manufacturing node may include multiple tape handling sections axially close together so that they are effectively a single node. The node aptly extends over an axial distance of less than 2.5m. Aptly the node has a length of 1m or less.

[0079] The pipe body includes a pressure armour layer 130 that is a pressure resistant layer that provides a structural layer that increases the resistance of the flexible pipe to internal and external pressure and mechanical crushing loads. The layer also structurally supports the internal pressure sheath. Aptly as illustrated in Figure 1 the pressure armour layer is formed as a tubular layer. Aptly for unbonded type flexible pipe the pressure armour layer consists of an interlocked construction of wires with a lay angle close to 90°. Aptly in this case the pressure armour layer is a metallic layer. Aptly the pressure armour layer is formed from carbon steel, aluminium alloy, stainless steel or the like. Aptly the pressure armour layer is formed from a pultruded composite interlocking layer. Aptly the pressure armour layer is formed from a composite formed by extrusion or pultrusion or deposition. A pressure armour layer is positioned radially outside an underlying barrier layer.

[0080] The flexible pipe body illustrated also includes a first tensile armour layer 140 and second tensile armour layer 150. Each tensile armour layer is used to sustain tensile loads and optionally also internal pressure. Aptly for some flexible pipes the tensile armour windings are metal (for example steel, stainless steel or titanium or the like). For some composite flexible pipes the tensile armour windings may be polymer composite tape windings (for example provided with either thermoplastic, for instance nylon, matrix composite or thermoset, for instance epoxy, matrix composite). For unbonded flexible pipe the tensile armour layer is formed from a plurality of wires (to impart strength to the layer) that are located over an inner layer and are helically wound along the length of the pipe at a lay angle typically between about 10° to 55°. Aptly the tensile armour layers are counter-wound in pairs. Aptly the tensile armour layers are metallic layers. Aptly the tensile armour layers are formed from carbon steel, stainless steel, titanium alloy, aluminium alloy or the like. Aptly the tensile armour layers have a microstructure that consists of orientated lamellae. Aptly the tensile armour layers are formed from a composite, polymer, or other material, or a combination of materials.

[0081] Aptly the flexible pipe body includes optional layers of tape 160 which help contain underlying layers and to some extent prevent abrasion between adjacent layers. A tape layer may optionally be a polymer or composite or a combination of materials, also optionally comprising a tubular composite layer. Tape layers can be used to help prevent metal-to-metal contact to help prevent wear. Tape layers over tensile armours can also help prevent “birdcaging” of the tensile armour wires.

[0082] The flexible pipe body also includes optional layers of insulation 165 and an outer sheath 170, which comprises a polymer layer used to protect the pipe against penetration of seawater and other external environments, corrosion, abrasion and mechanical damage. Any thermal insulation layer helps limit heat loss through the pipe wall to the surrounding environment. An annulus 180 is a region associated with the space between the internal pressure sheath 110 and the outer sheath 170. In other words, in the flexible pipe body illustrated in Figure 1 , the pressure armour layer 130, the first tensile armour layer 140, the further tensile armour layer 150, the optional layers of tape 160, and the optional layers of insulation 165 are located in the annulus region 180. It will be appreciated that in some embodiments, the annulus region 180 may contain any or none of the layers present in the flexible pipe body illustrated in Figure 1.

[0083] Each flexible pipe comprises at least one portion, referred to as a segment or section, of pipe body 100 together with an end fitting located at least one end of the flexible pipe. A respective end fitting may be used to terminate each end of the flexible pipe body. An end fitting provides a mechanical device which forms the transition between the flexible pipe body and a connector. The different pipe layers as shown, for example, in Figure 1 are terminated in the end fitting in such a way as to transfer the load between the flexible pipe and the connector.

[0084] Figure 2 illustrates a pipeline 200 suitable for transporting production fluid such as oil and / or gas and / or water from a sub-sea location 221 to a Pipe Lay Support Vessel (PLSV) 222. In Figure 2, the PLSV may be a ship. For example, in Figure 2 the sub-sea location 221 includes a sub-sea flow line 225. The flexible flow line 225 comprises a flexible pipe, wholly or in part, resting on the sea floor 230 or buried below the sea floor and used in a static application. In some alternatives, the PLSV may be provided by a platform. In other alternatives the PLSV may be provided by a floating platform. The pipeline 200 is an assembly. That is to say a plurality of flexible pipes 240 extending between the PLSV 222 to the sea floor. The pipeline shown 200 has six flexible pipes, 240i, 2402, 240s, 2404, 240s, and 240e. In the pipeline 200, neighbouring 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 pipeline 200 may alternatively have any multiple number of flexible pipes 240 such as two, three, four, five or more flexible pipes. It will be appreciated that a pipeline may include a plurality of flexible pipes.

[0085] It will be understood that some sections of the pipeline assembly may comprise thermoplastic composite pipe, i.e. a pipe with a structure at least partly made from a composite material. Optionally the pipeline assembly including thermoplastic composite pipe may be referred to a thermoplastic composite pipeline. Optionally thermoplastic composite pipe may include a plurality of bonded tape layers to provide a pipe of the desired wall thickness and strength (axially and in relation to internal pressure). Optionally the thermoplastic composite pipe may 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 layer of the thermoplastic composite pipe. Some thermoplastic composite pipelines may not have an annulus in which and through which permeated gas can accumulate and percolate to an end fitting. Optionally some thermoplastic composite pipeline may not have an annulus at least in part, so there may be no option to through-connect the annuli of flexible pipes either side of the thermoplastic composite pipe section in order to relieve a higher annulus pressure in one or other flexible pipe section via a fluid connection to a lower annulus pressure in another flexible pipe section. Certain embodiments of the present invention may overcome this limitation, providing an annulus gas passageway from the end of one flexible pipe section to an end of another flexible pipe section, past a section of thermoplastic composite pipe through which no annulus gas can be transmitted internally to the pipe wall (i.e. through an annulus).

[0086] In earlier use some of the pipeline may have been used as a riser and some as a flowline. For example it will be appreciated that there are different types of riser, as is well-known by those skilled in the art. Certain embodiments of the present invention may be used with retrieval of any type of riser, such as a freely suspended (free-hanging, catenary riser), a riser restrained to some extent (buoys, chains), totally restrained riser or enclosed in a tube (I or J tubes). Some, though not all, examples of such configurations can be found in API 17J. Portions of flexible pipe that can be retrieved can also previously have been utilised as a jumper.

[0087] Figure 3 illustrates a first (left-most in Figure 3) end fitting 300i and a further (right-most) end fitting 3002 arranged in a back-to-back arrangement. The first end fitting 300i terminates a respective end of a first segment of flexible pipe body 100i and the further end fitting 3002 terminates a respective end of a further segment of flexible pipe body IOO2. It will be understood that a still further end fitting may terminate a remaining end of the first segment of flexible pipe body 100i or a remaining end of the further segment of flexible pipe body IOO2. The end fittings 300i, 3002 are connected together via respective connector flanges 3101 , 3102. These are bolted together via bolts (not shown in Figure 3) and have matching seal ring grooves on opposing flange faces.

[0088] Each end fitting 300 further includes a central flange 320 spaced apart from the connector flange 310 via a neck region 330. An outer jacket 340 is secured to the central flange and an outer collar 350 is secured to the jacket 340 and seals against an outer surface of an outer sheath 170 of the flexible pipe body 100 via at least one seal ring. A radially innermost surface of the jacket 340 is spaced apart from a radially outer surface of a generally cylindrical but slightly flared outwards end of an elongate end fitting body 360 of the end fitting. An open mouth 365 of the end fitting body faces associated the segment of flexible pipe body. Tensile armour wires are terminated in the tapered space between the outer casing and the end fitting body. Aptly epoxy is located in the tapered space to entomb the ends of the tensile armour wires. The end fitting 300 is associated with a central longitudinal axis A-A and the central longitudinal axis of each end fitting is aligned along a common line when the end fittings are arranged in a back-to-back configuration. During use production fluids are transported along a bore provided by the barrier layer or liner of the flexible pipe body and the inner surface of each end fitting 300.

[0089] The end fittings 300i , 3002 illustrated in Figure 3 also each include a respective purge valves 370i, 3702. It will be appreciated the purge valves are fluidly connected to the annulus region of each respective flexible pipe via respective internal tubes 380i, 3802 that are not filled with epoxy and thus provide a fluid communication pathway of the end fittings that extends between respective purge valves and annulus regions of the flexible pipes.

[0090] Figure 4 illustrates a portion of an end fitting 400 and flexible pipe body 100 of a flexible pipe 401 in more detail. The flexible pipe 401 includes the end fitting 400 and flexible pipe body 100. Flexible pipe body 100 includes, from innermost to outermost: the internal pressure sheath 110 (or fluid retaining layer), the annulus region 180, and the outer sheath 170. It will be appreciated that the flexible pipe body 100 in Figure 4 has a smooth bore however it will be understood that a rough bore flexible pipe body may instead be utilised. The annulus region 180 includes the pressure armour layer 130, the first tensile armour layer 140, and the further tensile armour layer 150. It will be appreciated that other layers may be present in the annulus region 180. The end fitting 400 is broadly cylindrical in shape, as illustrated, for example, in Figure 3.

[0091] Figure 4 illustrates how the end fitting 400 includes a purge valve 410. 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 may protrude out of the end fitting 400 or may be supported on the end fitting 400. It will be appreciated that the purge valve 410 may be referred to as a purge outlet or a vent valve. It will be appreciated that the purge valve 410 of Figure 4 is in a front-end venting system configuration however it will be appreciated that any other suitable configuration may instead be utilised, such as side venting, where the purge valve 410 connects, for instance, to the jacket at a similar position to epoxy fill port 420. Figure 4 shows how annulus gasses from the annulus region 180 can pass to the purge valve via internal tubing 415 that is vent tubing. The internal tubing 415 is a fluid communication passageway that connects an inlet of the purge valve to an annulus region of a flexible pipe. Aptly no vent tubing is utilised and a different fluid communication passageway between the purge valve and the annulus region is instead utilised. The vent tubing 415 is a stainless-steel tubing which connects the annulus region 180 to the purge valve 410. The vent tubing 415 is surrounded by hardened epoxy in an epoxy housing 416 that is a cavity in the end fitting where tensile armour wires are terminated. It will be appreciated that the vent tubing 415 may alternatively be made from any alloy, composite, polymer, or the like.

[0092] The end fitting 400 has two fill ports: a first fill port 420 and a second fill port 422 that are sealed with epoxy. It will be appreciated that the filled ports 420, 422 may be made from a different material such as any polymer, or the like. It will be appreciated sometimes, there may be one fill port in the end fitting. In other examples, there may be more than two fill ports in the end fitting. It will be appreciated that one or more of the epoxy fill ports can be utilised to provide epoxy into the epoxy housing to secure the tensile armour wires in the end fitting.

[0093] Flexible pipe body 100 is attached to the end fitting 320 by separating the layers of flexible pipe body 100 at an end portion of flexible pipe body and securing the layers to the end fitting 400. The internal pressure sheath 110 is terminated and is held in place by a friction fit in a first gripping region 430. The internal pressure sheath 110 is gripped in the first gripping region 430 between a first half of the end fitting 400 and a further half of the end fitting 400. Therefore, fluid is prevented from leaking from the inside of the internal pressure sheath 110 into the annulus region 180. The pressure armour layer 130 is terminated separately from the remainder of the layers in the annulus region 180. The outer sheath 170 is terminated and is held in place by a friction fit in a further gripping region 440. Consequently, fluid is prevented from leaking from the outside of the outer sheath 170 into the annulus region 180. The annulus region 180 is therefore sealed from fluid ingress on both sides. The epoxy housing 416 in the end fitting 400 fills open space inside which the layers of the annulus region 180 are terminated. The epoxy housing 416 is filled by pumping epoxy into the first fill port 420 . Excess epoxy is purged through the second fill port 422.

[0094] Figure 5a illustrates how a purge valve 505 can be arranged on an end fitting 510 of a flexible pipe 512. As illustrated in Figure 5a, the purge valve 505 is arranged at an outer region of the central flange 515 of the end fitting 510. It will be understood that the purge valve is fluidly connectable to a cavity disposed between the outer casing and main body of the end fitting. It will be appreciated that the cavity is a region of the end fitting in which one or more layers of tensile armour wires may be terminated. It will be appreciated that the cavity is an example of a fluid communication region that is in fluid communication with an annulus region of a flexible pipe 512. It will be appreciated that the purge valve 505 may be located at any other suitable position of the end fitting 510 (or of the flexible pipe) so long as the purge valve 505 is fluidly connectable to the annulus of the flexile pipe 512 (optionally via the fluid communication region of the end fitting 510). While Figure 5a only illustrates one purge valve 505, it will be appreciated that a plurality of purge valves (for example two, three, four, five, or more purge valves) may be arranged on an end fitting 510.

[0095] Figure 5b illustrates the purge valve 505 of Figure 5a in more detail. As shown in Figure 5b, the purge valve 5b includes a valve housing 550 that includes a channel 555 in which a slidable member 560 is disposed. An end of the slidable member 560 incudes a piston head 565 which, when the purge valve 505 is arranged in a closed configuration, sits against a valve seat 570 of the housing 550. It will be appreciated that when the valve 550 is disposed in a closed configuration the piston head 565 and the valve seat 570 form a fluid seal to thereby prevent fluid communication between an inlet 572 and an outlet 574 of the valve 505. It will be appreciated that the inlet 572 or the valve 505 is fluidly connected to the fluid communication region of the end fitting 510 and thus is also fluidly connected to the annulus region of the flexible pipe.

[0096] As shown in Figure 5b, the purge valve 505 also includes a spring 580. It will be appreciated that the spring is an example of a biasing element. As is shown in Figure 5b, the spring 580 is connected to the piston head 565 and also to a region of the housing 550. It will be appreciated that the spring 580 is in an extended or stretched out state so that the spring 580 biases the slidable member towards the fluid inlet 572 of the valve 505 and thereby urges the piston head 565 into sealing engagement with the valve seat 570. The spring 580 thus helps urge the purge valve into a closed configuration where the fluid inlet 572 and fluid outlet 574 are fluidly disconnected. In use in a subsea environment, the upper surface of the piston head 565 (the surface that is most proximate to the fluid outlet 574 of the valve 505) is exposed to a local environment that is seawater. The piston head 565 is thus exposed to a local environmental pressure A that is a pressure of the seawater at a submerged depth of the outlet 574 of the purge valve 505. It will be appreciated that the local environmental pressure is thus a pressure of the water column at the submerged depth of outlet 574. This local environmental pressure A thus helps further urge the purge valve 505 into a closed configuration.

[0097] As is also illustrated in Figure 5b, the inlet 572 of the purge valve is exposed to an internal pressure B associated with the annulus of the flexible pipe. As indicated above, this is because the inlet 572 is in fluid communication with the annulus region via a fluid communication region of the end fitting 510. Thus, a fluid pressure in the annulus region of the flexible pipe is incident on a remaining end of the slidable member 560 that is the end most proximate to the fluid inlet 572 and opposite to the piston head 565. It will be appreciated the pressure at the fluid inlet 572 is a fluid pressure provided by fluid that has bled into the annulus region from the bore of the flexible pipe in use. Aptly this fluid is gaseous.

[0098] When the fluid pressure B at the fluid inlet 572 exceeds the local environmental pressure A by a predetermined amount, the fluid pressure urges the slidable member towards the fluid outlet 574 of the valve 505 to thereby urge the valve 505 into an open configuration. It will be appreciated that this action fluidly connects the inlet 572 and outlet 574 of the valve 505. The valve is thus responsive to a pressure differential across the valve and selectively connects the inlet and outlet responsive to this pressure differential. It will be thus understood that the purge valve can be manufactured to open at a predetermined or substantially predetermined pressure differential provided by a first pressure at the inlet and a further pressure at the outlet. For example, this could be achieved by utilising a spring of particular stiffness or elasticity. It will thus be appreciated that the valve 505 can be designed to purge gas from the annulus region of a flexible pipe before the pressure provided by gas in the annulus region reaches a point which risks damage to the pipe, for example due to bursting of the outer sheath of the Pipe. It will be understood that valve designs may vary and multiple spring elements may be incorporated, optionally including springs either side of the valve seat 570, to balance the resistance of the spring to internal pressure B with the local environment pressure A. Alternatively the valve may be configured with a single spring on the outer side of the valve seat 570 acting in compression with an ability to adjust the degree of compression and so the over-pressure required to open the valve.

[0099] Alternatively, any other suitable purge valve could be utilised.

[0100] Figure 6 illustrates how a purge valve 602 which is fluidly connectable to an annulus region of a first flexible pipe 604 can be supported on an end fitting of a further flexible pipe 606. Figure 6 illustrates a portion of a pipeline 608. As illustrated in Figure 6, at least some of the pipeline 608 is arranged in a subsea environment 610. The pipeline includes a first flexible pipe 604 and a further flexible pipe 606. As shown in Figure 6 the first flexible pipe 604 and the further flexible pipe 606 are arranged underwater in the subsea environment 610. Figure 6 illustrates how the first flexible pipe 604 is arranged at a depth in the subsea environment that is greater than the further flexible pipe 606. That is to say that the further flexible pipe 606 is arranged closer to the surface of the water column (of the sea) than the first flexible pipe 604. It will be appreciated that the pipeline may be a riser and the like and the first flexible pipe may be arranged deeper underwater than the further flexible pipe throughout the lifetime of the pipeline. It will also be appreciated that the pipeline may be partially or wholly arranged on the seabed and thus the further flexible pipe may only intermittently be arranged at a shallower depth than the first flexible pipe, for example during a pipeline retrieval operation where the pipeline is winched up to a surface location. It will be appreciated that the further flexible pipe is arranged more proximate to a pipeline termination point at or near the surface of the water column (at or near sea level). It will be understood that the pipeline includes a plurality of flexible pipes arranged in an end-to-end configuration and adjoined via respective end fittings of the flexible pipes.

[0101] As shown in Figure 6, the first end flexible pipe includes a first end fitting 612 arranged at a first end of the flexible pipe. It will be appreciated that a flexible pipe body 614 of the first flexible pipe 604 is terminated in the first end fitting 612. It will be appreciated, although not shown, that the remaining end of the flexible pipe body 614 of the first flexible pipe 604 may also be terminated in an end fitting. Figure 6 helps illustrate how a connector flange 615 of the first end fitting 612 is connected to a connector flange 616 of an adjacent end fitting 618 of an adjacent flexible pipe 620.

[0102] Figure 6 shows how the further flexible pipe 606 includes a further end fitting 622 in which a further pipe body 624 of the further flexible pipe 606 is terminated. It will be appreciated that the further flexible pipe 606 may be the adjacent flexible pipe 620 and that the further end fitting 622 may be disposed at a terminal end of the further flexible pipe 620 that is opposite to the end that the adjacent end fitting 618 is located. Alternatively, one, two, three or more still further flexible pipes may be disposed between the first flexible pipe 604 and the further flexible pipe 606 and connected in an end-to-end configuration.

[0103] As is illustrated in Figure 6, a first purge valve 602 is here supported on the further end fitting 622. The first purge valve 602 in Figure 6 is mounted on the further end fitting 622 via an adaptor 625. It will be understood that the adaptor may allow the first purge valve to be retrofitted to existing pipelines. It will be understood that the first purge valve 602 may be supported on the further end fitting 622 without an adaptor. It will be appreciated that the first purge valve 602 may be similar to the purge valve 505 described with respect to Figure 5b however an inlet 626 of the first purge valve 602 is not fluidly connected to an annulus region of the further flexible pipe 606. Instead, as shown in Figure 6, the inlet 626 of the first purge valve 602 is fluidly connected to an external fluid tube or hose element 628 (that is located externally to the pipeline 608). That is to say that the external tube 628 and the inlet 626 of the valve 602 are fluidly connected. 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 a lumen may include a plurality of hose elements or external fluid tubes. It will be appreciated that the external tube 628 may be manufactured from a flexible material. It will be appreciated that the external tube may be manufactured from a rigid material. It will be appreciated that the external tube may be manufactured from a polymeric material. It will be appreciated that the external tube is substantially leak proof. The purge valve 602 may be an end connector that prevents biofouling and / or blockage of the end of the external tube 628.

[0104] As shown in Figure 6, the external tube (that may be an example of a hose element) 628 extends along a length of the pipeline 608, but external to the pipeline 608, between the inlet of 626 of the first purge valve 602 and a further purge valve 630 that is supported on the first end fitting 604. The further purge valve 630 of Figure 6 is substantially the same as, and is supported on the first end fitting 604 in substantially the same way as, the purge valve 505 described with respect to Figure 5b. Aptly any other suitable valve may instead be utilised. Aptly the external tube 628 is connected directly to first end fitting 612 (not via any further purge valve) and is in fluid communication with the annulus of the first flexible pipe 604.

[0105] Figure 6 thus illustrates how the external tube 628 is connected between the first end fitting 612 and the further end fitting 622 via respective purge valves 630, 602 at respective ends of the tube 628. Thus, it will be appreciated how the annulus region of the first flexible pipe 604 is selectively fluidly connectable to the interior region of the external tube 628 (that is a fluid communication region) via the further purge valve 630. It will also be understood that the interior region of the external channel 628 is selectively connectable to an outlet 632 of the first purge valve 602 via the first purge valve 602. It will be understood that the first purge valve outlet 632 is exposed to the local environment and thus water pressure at a submerged depth of the first purge valve outlet. Optionally, the first purge valve 602 may be alternatively or additionally fluidly connected to a still further flexible pipe section annulus via a fluid connection passageway which may be internal to, and connected through, the flange-to-flange end fitting connections between adjacent sections of flexible pipe, thereby allowing higher pressure annulus fluid to pass to through to a lower pressure annulus space.

[0106] When an annulus pressure, that is provided by fluid in the annulus region of the first flexible pipe, exceeds a pressure associated with the inner region of the external tube 628 by a predetermined amount of pressure (that is to say when a pressure differential across the further purge valve 630 exceeds a predetermined pressure differential) the further purge valve 630 will be urged, via the fluid pressure in the annulus region of the first flexible pipe, to an open configuration in which the annulus region of the first flexible pipe 604 and the inner region of the external tube 628 are fluidly connected. It will be understood that the inner region of the external tube may be a bore of the tube that may be a bore of a lumen. It will be appreciated that when a pressure provided by fluid in the annulus region of the first flexible pipe 604 does not exceed a pressure associated with the internal region of the external tube 628 by a predetermined amount, the further purge valve 630 remains in, or is urged into (via a biasing element of the further purge valve alongside a pressure in the external tube), a closed configuration in which a fluid inlet and outlet of the further purge valve are fluidly disconnected. It will be appreciated that the excess pressure associated with opening further purge valve 630 may aptly be selected or set to be near zero, i.e. the pressure from the annulus region of the first flexible pipe 604 may readily equalize with the pressure in the internal region of the external tube 628, without any significant pressure differential needing to be present. In the event of damage to the external tube 628, or failure of the first purge valve 602, the external water pressure would cause the further purge valve 630 to close and seal, thereby preventing ingress of water into the annulus of the first flexible pipe 604.

[0107] It will be appreciated that, in the arrangement shown in Figure 6, the further end fitting 622 is located at a shallower depth than the first end fitting 612 and thus, the first purge valve 602 is located at a shallower depth than the further purge valve 630. It will thus be appreciated that the local environmental pressure due to the water column is lower at the position in which the first end fitting (and thus the further purge valve) is located. It will thus be appreciated that fluid in the annulus region of a flexible pipe can be purged at a lower pressure when a purge valve is disposed at a shallower submerged depth. This is because, a lower pressure of fluid in an annulus region of a flexible pipe would exceed a local environmental pressure at a shallower submerged depth relative to a deeper submerged depth by a predetermined amount.

[0108] Figure 6 illustrates how, due to the connection between the first purge valve 602 and the annulus region of the first flexible pipe 604 via the external fluid tube 628, gasses from the annulus region of the first flexible pipe are vented at the location of the first purge valve. It will be appreciated that, during a pipe retrieval operation when a pipeline is being pulled in, gasses present in the annulus 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 where the local environmental pressure is low enough that the annulus pressure (provided by a fluid in the annulus region) can overcome the said environmental by a predestined amount and thus be urged into an open configuration. Thus, during retrieval of a pipeline, flexible pipes can begin purging fluid early relative to what would otherwise occur conventionally.

[0109] Figure 6 also illustrates how the first and further end fittings may include still further purge valves 690 that are not connected to any external tubes and thus purge gas / fluid from the annulus region of a flexible pipe when a pressure provided by said fluid exceeds the local environmental pressure at a submerged depth of the still further purge valve by a predetermined amount.

[0110] Figure 7a illustrates how a first purge valve 702 that is fluidly connectable to an annulus region of a first flexible pipe can be supported on an end fitting 704 of a further flexible pipe 706. Figure 7a illustrates how the further end fitting 706 may include a valve support region 708. It will be understood that the valve support region may be integrally formed with an end fitting component (for example the outer cover / jacket or the intermediate flange of the end fitting body). Alternatively, the valve support region 78 may be a separate unit that is connected to the end fitting. It will be understood that this may be achieved via bolting or the like. As illustrated in Figure 7a, the valve support region includes a rear opening for accommodating an external tube 712 that extends from the first purge valve to an end fitting of the first flexible pipe, optionally via a further purge valve as is shown in Figure 6.

[0111] Figure 7b illustrates how a first purge valve 702 that is fluidly connectable to an annulus region of a first flexible pipe can be supported on an end fitting 704 of a further flexible pipe 706. Figure 7b illustrates how an adaptor 740 that houses the first purge valve can be secured to the further end fitting. It will be appreciated that the adaptor is a separate unit to the end fitting components. It will be understood that the adaptor can be retrofitted to an end fitting that may already be deployed in a subsea environment, for example via use of an ROV or the like.

[0112] Figure 7c illustrates how a first purge valve 702 that is fluidly connectable to an annulus region of a first flexible pipe can be supported on an end fitting 704 of a further flexible pipe 706. Figure 7c illustrates how the further end can include a channel 760 for accommodating a tube that extends from an inlet of the first purge valve to the first end fitting. Optionally the remaining end of the tube is connected to an outlet of a further purge valve that is supported on an end fitting of the first flexible pipe. It will be understood that, aside from extending through the channel of the further end fitting, the tube extends from the further end fitting to the first flexible external to the pipeline in which the first flexible pipe and the further flexible pipe are arranged.

[0113] Figures 8a and 8b illustrate how a buoyancy module 802 that includes or supports a purge valve 804 can be fluidly connected to an annulus region of a flexible pipe 806 of a pipeline 808. As is shown in Figure 8a, the pipeline 808 as at least partly arranged in a subsea environment 810. Aptly the pipeline 808 may be arranged in any underwater environment. Whereas the embodiment of figure 6 shows the first purge valve 602 supported on the further end fitting 622, here the purge valve 804 is supported on the buoyancy module 802, however the arrangement for connecting to the annulus of the first flexible pipe 806 (604 in Figure 6) may be similar , via the first end fitting of the first flexible pipe with the a further purge valve (630) protecting the annulus of the first flexible pipe from water ingress. As shown in Figure 8, the pipeline 808 extends from a pipeline termination point 812 at the surface 814 of the subsea environment (at sea level). It will be understood that the pipeline termination point 812 may be a platform, for example a floating platform, or a vessel, for example a ship, or the like. Figure 8a shows how the pipeline 808 includes a number of flexible pipes 806 that each include a segment of flexible pipe body 816. It will be understood that each flexible pipe 806 of the pipeline 808 is connected to at least one adjacent flexible pipe 806 in an end-to-end configuration via respective end fittings 818. That is to say a first flexible pipe 806 of the pipeline 808 is connected to a further flexible pipe 806 of the pipeline 808 via a first end fitting 818 of the first flexible pipe 806 and a further end fitting 818 of the further flexible pipe 806, the first and further end fittings 818 being connected via respective connector flanges of the end fittings, aptly via bolting. As shown, the pipeline 808 of Figure 8a extends from the pipeline termination point 812 to the seabed 820 and extends along a region of the seabed 820.

[0114] Figure 8a illustrates how external fluid tubes 822 can be attached to various end fittings 818 throughout the pipeline. In the system of Figure 8a, an external tube is connected to one end fitting 818 of each flexible pipe 806 of the pipeline 808. Alternatively, it will be appreciated that any number of external tubes may be connected to any number of end fittings. It will be appreciated that an external tube 822 is connected to a respective end fitting 818 so as to be fluidly connectable to the annulus region of the flexible pipe 806 that includes that particular end fitting 818. The tubes 822 shown in Figure 8a are flexible tubes that are made from a polymeric material and can move, to a degree, in the local environment. Aptly the tubes may be made from any other suitable material or materials. Aptly the tubes are rigid. It will be appreciated that the external tubes 822 are connected to the end fitting 818 that is closest to the pipeline termination point 812 in each flexible pipe 806. Aptly the external tubes 822 may be connected to any other end fitting 818 or at any other position on each flexible pipe 806 so long as the external tubes 822 are fluidly connectable to the annulus region of the flexible pipe 806.

[0115] As shown in Figure 8a, the external tubes 822 may extend to respective buoyancy modules 802 that float above the flexible pipe to which the tubes 822 are connected. It will be appreciated that the buoyancy modules contain a buoyant substance, for example air or a different low density fluid, to enable the buoyancy modules to float above the respective flexible pipes. It will be appreciated that each buoyancy modules includes or supports a purge valve 804. It will be appreciated that the purge valves 804 are substantially the same as the purge valves described with respect to Figure 5b. Alternatively, any other suitable purge valve may instead be utilised. It will be appreciated that a fluid outlet of the purge valve 804 is open to the subsea environment 810 in which the buoyancy module 802 is arranged.

[0116] It will be understood that the external tubes 822 in Figure 8a are connected to an end fitting 818 of respective flexible pipes 806 via further purge valves in a similar manner as described with respect to Figure 6. Thus, the external tubes 822 are selectively fluidly connectable to the annulus region of the respective flexible pipes 806 to which they are connected. It will be appreciated that the further purge valves may be substantially similar to the purge valve described with respect to Figure 5b. It will be understood that the further purge valves are designed to be in a closed configuration (where the inlet and outlet of the further purge valve are fluidly disconnected) in the absence of external force and are designed to be urged into a open configuration when a pressure at the fluid inlet of the further purge valve exceeds a pressure at the fluid outlet of the further purge valve by a predetermined pressure. The predetermined pressure may be determined in manufacture of the purge valve. It will be understood how, before the further purge valve purges annulus fluid into the external tube due to a pressure provided by the fluid in the annulus region of a flexible pipe, the inner region of the external tube 628 (that is a bore of the eternal tube) contains air or another environmental fluid that may have entered into the external tube during manufacture or during securing the tube and purge valves to a respective flexible pipe. It will be appreciated however that after the further purge valve is urged into an open configuration due to a pressure in the annulus of the flexible pipe, due to fluid in the annulus region of the flexible pipe, exceeding a pressure in the external tube, provided by fluid in the external tube, the external tube will instead contain fluid from the annulus. Thus, it will be appreciated how the further purge valve can purge fluid, that optionally is gas that has permeated through the inner line of a flexible pipe into the annulus region of said pipe, into the external tube.

[0117] It will 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 will thus be appreciated how fluid can be purged from the external tube into the subsea environment at a lower pressure at the submerged depth of the fluid outlet of the purge valve supported on the buoyancy module compared with a purge valve open to the environment located at a submerged depth of the end fitting to which the external tube is connected. Thus, it will be appreciated that annulus fluid that has entered the external tube via the further purge valve can provide a pressure that exceeds a local environmental pressure provided by the water column at a submerged depth of the fluid outlet of the purge valve (supported on the buoyancy module) as more fluid from the annulus is vented into the external tube via the further purge valve.

[0118] It will be understood that a fluid outlet of the further purge valves supported on respective end fittings and connected to the external tube are not exposed to the local environment and thus the position of the valve (being in a closed or open configuration) is responsive to the pressure in the annulus region of the flexible pipe and the pressure in the external tube. It will be understood that the end fittings 818 may include (or support) one or more still further purge valves that are exposed to the local environment.

[0119] It will be appreciated that, if no further purge valve is included in an end fitting, fluid from the annulus is free to flow into the external tube. Thus the external tube will be at substantially the same pressure as the annulus region of a flexible to which the external tube is connected. It will be understood that the higher up in the water column a purge valve is disposed, the lower the pressure of fluid in an annulus will cause the purge valve to purge / vent fluid into the environment.

[0120] It will be appreciated that, the in arrangement shown in Figure 8a, the external tubes are able to withstand the buoyancy force provided by the buoyancy module. That is to say that the external tubes are strong enough to act as a tether to tether the buoyancy module to the flexible pipe.

[0121] Figure 8b illustrates a buoyancy module 802 that include / supports a purge valve 804 in more detail. As shown in Figure 8b, the buoyancy module 802 includes a body 850 that houses a buoyant fluid (for example air). It will be appreciated that the buoyant fluid is a low-density fluid. A 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. Aptly, the purge valve 804 may be located at any other suitable location on the body 850. As shown in Figure 8b, the purge valve includes a fluid inlet 860 and a fluid outlet 870. The fluid outlet is connected to the external tube 822. It will be understood that the fluid inlet 860 is fluidly connected to (in fluid communication with) in inner region or channel of the external tube 822 that is a fluid communication passageway of the external tube 822. It will be appreciated that the external tube is an example of a lumen. Figure 8b shown how the fluid outlet 870 of the purge valve is open to the environment that is a subsea environment 810. It will thus be understood how the fluid outlet 870 is exposed to a local environmental pressure provided by the water column (of the subsea environment 810) at a submerged depth of the fluid outlet 870. It will thus be appreciated how the fluid inlet 860 and the fluid outlet 870 are selectively connectable responsive to a pressure, provided by a fluid, in the inner region / channel of the external tube 822 and a local environmental pressure at the submerged depth of the fluid outlet 870.

[0122] Figure 9a illustrates a further buoyancy module 902 that includes or supports a purge valve 904. It will be understood that the buoyancy module of Figure 9a operates in substantially the same way as described with respect to Figures 8a and 8b. The buoyancy module 902 of Figure 9a is substantially the same as the buoyancy module 802 described with respect to Figures 8a and 8b. The buoyancy module 904 includes a body 906 that includes a buoyant material, for example a buoyant 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 arranged. It will be understood that the purge valve 904 includes a fluid inlet 910 connected to an external tube 912, and a fluid outlet 914 that is exposed to the local environment (and thus a pressure of the water column at a submerged depth of the fluid outlet 914 in the environment). It will be appreciated that the purge valve 904 of Figure 9a is substantially the same as the purge valve described with respect to Figures 5a and 5b. Aptly any other suitable purge valve may instead be utilised.

[0123] Figure 9a illustrates how the buoyancy module 902 includes a frame element 916 or framework that extends partly through the body 906 (and through the cavity 908) of the buoyancy module 902. The frame element 916 is manufactured from a metallic material. Optionally any other suitable material may be utilised to manufacture the frame element. Figure 9a illustrates how the purge valve 904 is supported on the frame element 916.

[0124] It will be appreciated that Figure 9a illustrates an external tube 912 that anchors the buoyancy module to flexible pipe. The external tube 912 is thus suitable for anchoring the buoyancy module 902 and can withstand the buoyancy force provided by the buoyant material in the buoyancy module 902. Aptly the external tube 912 is manufactured from a polymer material. Aptly the external tube 912 is manufactured from a metallic material. Aptly the buoyancy module 912 is manufactured from a rigid material. Optionally the buoyancy module is manufactured from a flexible material. Figure 9b illustrates a still further buoyancy module 950. It will be appreciated that the buoyancy module 950 of Figure 9b is similar to the buoyancy module 902 described with respect to Figure 9a. The buoyancy module thus includes an annular body that contains a buoyant material and includes an inner cavity in which a purge valve 956 is arranged. The purge valve 956 is supported on a frame element that extends through the cavity 954 of the body 952. Figure 9b also illustrates how the purge valve 956 includes a fluid inlet 960 that is connected to an external fluid tube 962, and a fluid outlet 964 that is exposed to the local environment.

[0125] The buoyancy module 950 of Figure 9b however is tethered / anchored to a flexible pipe via an anchoring element 966 (or tethering element) that is not the external tube 962. Figure 9b illustrates how the frame element 958 of Figure 9b includes two protruding portions 968 that each protrude out of a bottom surface (from the perspective view shown in Figure 9b) of the body 952 on opposite sides of the body 952). Respective ends 970 of the anchoring element 966 are each connected to a protruding portion 968 of the frame element 958. It will be appreciated that the anchoring element 966 can be looped round a region of a flexible pipe (as described in further detail with respect to Figure 10b) so that each end 970 of the anchoring element 966 is terminated at, and connected to, the frame element 958 to thereby secure (or anchor) the buoyancy module 950 to a flexible pipe. As shown in Figure 9b, substantially parallel portions of the looped anchoring element 966 extend through an eyelet of a tie element 972.

[0126] Figure 10a helps illustrate how a buoyancy module that includes a purge valve can be anchored to a flexible pipe 1002 via an external fluid tube 1004. It will be appreciated that the anchoring arrangement illustrated in Figure 10a may be utilised for the buoyancy modules described with respect to Figures 8a, 8b or 9a. As shown in Figure 10a a terminal end of the external tube is connected to an anchoring element 1006. It will be appreciated that the anchoring element is an example of a tethering element or an anchoring arrangement. As shown in Figure 10a, the anchoring element 1006 includes an anchoring block 1008 and an anchoring strap or wire or chain or the like 1010. Figure 10a illustrates how each end of the strap or wire or chain or the like is connected to (and terminated at) the anchoring block 1008. Figure 10a helps illustrate how the strap or wire or chain or the like is looped around a region of the flexible pipe body 1012 of the flexible pipe 1002 to thereby secure a buoyancy module, via the external tube 1004, to the flexible pipe 1002. Figure 10a illustrates how a further external tube 1014 is connected between the anchoring block 1006 and a further purge valve 1016 that 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 annulus region of the flexible pipe 1002. The further purge valve 1016 is substantially the same as the purge valve discussed with respect to Figures 5a and 5b however it will be understood that any other suitable purge valve may instead be utilised. Aptly, no further purge valve is included and the further external tube 1014 is directedly connected to the end fitting 1018 and is fluidly connected to the annulus region of the flexible pipe 1002. It will be appreciated that the external tube 1004 and the further external tube 1014 are fluidly connected via the anchoring block 1008. That is to say that the anchoring block 1008 includes a fluid communication passageway that fluidly connects the external tube 1004 and the further external tube 1014. Thus the external tube 1004 is fluidly contactable to the annulus region of the flexible pipe 1002 via the anchoring block 1008, the further external tube 1014 and the further purge valve 1016 (and also via a fluid communication region of the end fitting 1018 that is fluidly connected to an inlet of the further purge valve 1016).

[0127] Alternatively, it will be appreciated that the external tube 1004 and the further external tube 1014 may be a single external tube that extends through the anchoring block 1008 or is supported on the anchoring block 1008.

[0128] As shown in Figure 10a, the flexible pipe 1002 is arranged on a seabed 1020 of a subsea environment 1022.

[0129] Figure 10b illustrates how a buoyancy module that includes a purge valve can be anchored to a flexible pipe 1050 via an anchoring element 1052 that is separate to an external tube 1054. It will be appreciated that the anchoring arrangement illustrated in Figure 10b may be utilised to anchor the buoyancy module of Figure 9b to a flexible pipe 1050. Figure 10b illustrates how an external tube 1054 is connected to a further purge valve 1056 that is supported on an end fitting 1058 of the flexible pipe 1050. It will be appreciated that the further purge valve 1056 is substantially the same as the purge valve described with respect to Figures 5a and 5b. Alternatively, any other suitable purge valve may be utilised. It will be appreciated that the further purge valve is fluidly connectable to an annulus region of the flexible pipe 1050. It will be appreciated that the external tube 1054 is fluidly connectable to the annulus region of the flexible pipe via the further purge valve 1056. Alternatively, no further purge valve is disposed between the end fitting 1058 and the external tube 1054 and the external tube is always fluidly connected to the annulus region of the flexible pipe 1050. It will be understood that a remaining end of the external tube 1054 is connected to a purge valve that is supported on, or included in, the buoyancy module that is anchored to the flexible pipe 1050.

[0130] As is shown in Figure 10b, a strap or wire or chain or the likel 052 (that is an example of an anchoring element) is looped around a region of flexible pipe body 1060 of the flexible pipe 1050. Figure 10b illustrates how substantially parallel regions of the looped strap or wire or chain or the like 1052 pass through an eyelet of a tie element 1062 to keep the substantially parallel regions of the looped strap or wire or chain or the like 1052 together. It will be appreciated that the ends of the looped strap or wire or chain of the like 1052 are connected to the buoyancy module, for example via a frame of the buoyancy module as shown in Figure 9b, to thereby anchor the buoyancy module to the flexible pipe 1050.

[0131] Figure 10b illustrates how the flexible pipe 1050 is arrange on a seabed 1070 of a subsea environment 1072.

[0132] Figure 11 illustrates a further example of how buoyancy modules 1102 that each include respective purge valves 1104 can be used to purge fluid that has accumulated in an annulus region of a flexible pipe 1106 of a pipeline that is arranged in a subsea environment 1110. It will be appreciated that the arrangement shown in Figure 11 is similar to the arrangement described with respect to Figure 8a. Aptly the environment illustrated in Figure 11 is a substantially shallow subsea environment. Aptly Figure 11 illustrates a deep subsea environment. As shown in Figure 11 , the pipeline 1108 extends from a pipeline termination point located 1114 located at or proximate to the surface 1116 of the subsea environment (at or around sea level) that may be a vessel (for example a ship or the like) or a platform (for example a floating platform or a fixed platform or the like) to the seabed 1118 and extends along a region of the seabed 1118. Figure 11 illustrates how the pipeline 1108 includes a plurality of flexible pipes 1106 that are connected in an end-to-end configuration via respective end fittings 1120 of the flexible pipes 1106. That is to say an end fitting 1120 of a flexible pipe 1106 is connected to an adjacent end fitting of an adjacent flexible pipe.

[0133] Figure 11 illustrates how each buoyancy module 1102 is connected to a respective flexible pipe 1106 via an external fluid tube 1122 that is connected to a fluid inlet of the purge valve 1104 that is supported on the buoyancy module 1102. It will be appreciated that the remaining end of each external tube 1122 is connected to a respective end fitting 1120 of a flexible pipe 1106 via a further purge valve, that is supported on said end fitting, as described with respect to Figures 6 to 10. Aptly, no purge valves are utilised and the remaining end of the tube is connected directly to an end fitting. It will thus be appreciated that each external tube 1122 is selectively fluidly connectable (via the respective further purge valves) to an annulus region of respective flexible pipes 1106 to which the respective buoyancy modules are anchored. As discussed with respect to Figure 8a, the purge valves 1102 include a fluid inlet that is in fluid communication with a respective external tube 1122 (to which the purge valve 1104 is connected), and a fluid outlet that is exposed to the environment and is thus exposed to a local environmental pressure provided by the water column of the environment 1110 at the submerged depth of the fluid outlet. It will be appreciated that the submerged depth of the fluid outlet of each purge valve is located above the flexible pipe due to the buoyancy provided by the respective buoyancy modules. It will be understood, as the local pressure at the position of each purge valve in the water column is lower than the local pressure at a position of a respective flexible pipe 1106 in the water column (due to the shallower depth at which the buoyancy modules 1102 are arranged compared with respective flexible pipes 1106), the purge valves 1104 are able to purge fluid that has accumulated in the annulus when the annulus pressure is lower relative to a similar purge valve that is located at the depth of the flexible pipe 1106. This helps prevent pipe damage due to pressure build up in the annulus region and also allowed for purging of gasses at a faster rate (and sooner) than an equivalent purge valve at a lower submerged depth. If the fluid accumulating in the annulus region of a flexible pipe are corrosive gasses, for example, early and faster venting of fluids from an annulus region of a flexible pipe may help extend pipe lifetime.

[0134] Figure 11 helps illustrate how a first buoyancy module 1102i floats on the surface 1116 of the subsea environment 1110. The external tube 1122 associated with the first buoyancy module is thus long enough to allow the first buoyancy module to reach the surface 1116. It will be understood that the fluid outlet of the purge valve 1104 supported on (or included in) the first buoyancy module 1102i is thus exposed to air at the surface 1116 and is thus exposed to atmospheric pressure instead of a pressure associated with the water column. This helps promote fast purging of annulus fluid in a flexible pipe, at relatively low annulus pressures (when the pressure of fluid in the annulus region exceeds atmospheric pressure by a predetermined threshold pressure).

[0135] Figure 11 helps illustrate how a further buoyancy module 11022 is located at an underwater location in the subsea environment 1110. Figure 11 thus helps illustrate how the purge valve 1104 that is included in (or supported on) the further buoyancy module 11022 purges fluid when a pressure of fluid in the annulus region of the respective flexible pipe 1106 (to which the purge valve 1104 associated with the further buoyancy module 11022) exceeds a water pressure at the depth of the further buoyancy module 11022 by a predetermined threshold pressure.

[0136] Figure 11 also helps illustrate how a pressure of fluid in an annulus region of a flexible can be controlled via purge valves 1104 supported on buoyancy modules 1102. For example, by positioning a buoyancy module (that includes or supports a purge valve) at a shallower or deeper depth of a water column one can decrease or increase the pressure of fluid in an annulus region of a particular flexible pipe 1106 respectively. Thus, by providing an anchoring system of particular length, a fluid pressure in the annulus region of a particular flexible pipe can be determined. Furthermore, it will be appreciated that the pressure of fluid in an annulus region of a particular flexible pipe could be modulated by modulating the height of a buoyancy module 1102 that includes or supports a purge valve 1104. For example, by increasing the height of a buoyancy module 1102 that includes or supports a purge valve 1104 the pressure of fluid in an annulus region of a flexible pipe is maintained at a lower pressure than if a buoyancy module 1102 (including or supporting a purge valve 1102) is at a lower / deeper depth of the water column. This is because the purge valve 1104, when the buoyancy module 1102 is at a shallower position in the water column, will start to purge fluid from the annulus region of a flexible pipe 1106 at a lower annulus pressure relative to a purge valve at a deeper location in the water column. Thus the pressure in the annulus region is maintained at a lower pressure. It will be understood that, by utilising buoyancy modules that include / support purge valves (that are fluidly connectable to respective annulus regions of respective flexible pipes) it is possible to vary the rate of fluid purging from annulus regions different flexible pipes of a pipeline, and also to vary the pressure associated with the annulus regions of each flexible pipe. For example, it may be desirable to purge fluid at a higher rate near well-head locations and the like where corrosive gasses may be more prevalent. It is also possible to account for variations in the depths of flexible pipes in a pipeline (for example due to seabed topography and the like) to purge fluid from annulus regions of a variety of flexible pipes of a pipeline to substantially equilibrate the rate of fluid purging and pressure of fluid in the annulus regions of these flexible pipes.

[0137] Figure 12 illustrates a portion of a pipeline 1202 where an external tube 1204 has broken or burst and thus has flooded. As shown in Figure 12, the pipeline 1202 includes a first flexible pipe 1206 and a further flexible pipe 1208 connected in an end-to-end configuration. The external tube 1204 is connected to a first purge valve 1210 that is supported on an end fitting 1212 of the further flexible pipe 1208. The tube 1204 is also connected to an end fitting 1214 via a further purge valve 1216. It will be understood that an inner channel of the external tube 1204 is selectively fluidly connectable to an annulus region of the fist flexible pipe 1206 via the further purge valve 1216. It will be appreciated that prior to bursting, fluid from the annulus region is purged into the external tube via the further purge valve and subsequently into the environment via the first purge valve 1210. It will be appreciated that the first purge valve may be at a different position in a water column than the first flexible pipe and thus may be associated with a different local environmental pressure (for example a lower environmental pressure) than the end fitting 1214 of the first flexible pipe 1206 as has been discussed with respect to Figures 6 to 11 . When the external tube 1204 bursts, the further purge valve 1216 however is exposed to the local environmental pressure of the water column at the further purge valve and thus the further purge valve prevents water ingress into the first flexible pipe 1206. Thus pipe flooding is prevented by providing a further purge valve 1216 between the external tube 1204 and the end fitting 1214 of the first flexible pipe.

[0138] Figure 12 also illustrates how multiple further external tubes 1240 can be arranged along the length of a pipeline to purge fluid in annulus regions of multiple flexible pipes of a pipeline.

[0139] Figure 13 illustrates a cross sectional view of another purge valve 1304. It will be appreciated that the purge valve 1304 shown in Figure 13 could be utilised in any of the arrangements illustrated in Figures 6 to 12. Figure 13 helps illustrate how the purge valve can be arranged in a closed configuration 1308 and an open configuration 1312. As illustrated in Figure 13, the purge valve includes a fluid inlet 1316 and a fluid outlet 1320. The inlet 1316 and outlet 1320 are disposed on opposite sides of the valve however it will be appreciated that the inlet and outlet may be disposed in any other suitable orientation. Figure 13 also shows how the purge valve 1304 includes a housing 1324 that includes a channel 1328 in which a movable member 1332 is located. It will be understood that the movable member is axially movable in the channel.

[0140] 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 shown in Figure 13, the movable member 1332 includes a piston head 1336 at an end of the movable member 1332 most proximate to the outlet 1320. The piston head 1336 is locatable to abut against a valve seat 1340 that is a portion of the housing that extends radially into the channel 1328. It will be appreciated that when the piston head is located to abut against the valve seat, the valve seal and the piston head form a seal so that the valve is in a closed configuration. It will also be appreciated that when the piston head is located to be distal to (not in contact with) the valve seat, fluid can pass around the piston head and thus the valve is in an open configuration. As shown in Figure 13, the valve seat includes a tapered region of the channel that is tapered radially inwardly and engages with correspondingly tapered radial surfaces of the piston head. The engagement between the tapered region and the radial surface of the piston head thus provide sealing. Figure 13 also shows how a non-tapered region 1348 of the channel is wider than the piston head so that in the open configuration fluid can flow around the piston head and therefore the inlet and outlet are fluidly connected.

[0141] Figure 13 also shows how the valve includes a spring 1352 located on a spring seat 1356 that is located proximate to the fluid inlet 1316. The remaining end of the spring 1352 is connected to the end of the movable member 1332 most proximate to the fluid inlet 1316. It will be appreciated that the spring 1352 is in a partially extended state when the valve is in a closed configuration 1304 and thus the spring acts to bias the movable member towards the fluid inlet to thereby bias the valve into the closed configuration 1304. It will thus be understood that when the spring 1352 is in an open configuration 1308, the spring is further extended and thus acts to bias the movable member 1332 away from the outlet 1320 thereby basing the valve away from the open configuration. It will be appreciated that the spring is an example of a biasing element.

[0142] In use, it will be appreciated that the fluid inlet 1316 may be fluidly connected to an annulus region of a flexible pipe or to a fluid communication region of a lumen (that may be an external tube or hose element) and is thus exposed to a pressure provided by a fluid at said annulus region or fluid communication region. It will be appreciated that the fluid outlet 1320 may be fluidly connected to a local environment (that may be an underwater environment at a particular submerged depth of the outlet) or to a fluid communication region of a lumen (that may be an external tube or hose element). Thus, the outlet 1320 is exposed to a pressure provided by said environment (that may be a local environmental pressure provided by a water column at a particular submerged depth of the outlet) or by a fluid in said fluid communication region. It will be appreciated that a restoring force (or biasing force) provided by the spring 1352 and the pressure (provided by the environment or by a fluid) at the outlet act to urge the valve towards the closed configuration by urging the movable member 1332 towards the fluid inlet 1316 (thereby urging the piston head 1336 into abutment with the valve seat 1340). It will also be appreciated that the pressure provided by a fluid at the fluid inlet 1316 acts to urge the valve towards the open configuration by urging the movable member towards the fluid outlet (thereby urging the piston head away from the valve seat). It will thus be appreciated that when a force across the underside surface (from the perspective view shown in Figure 13) of the piston head provided by fluid at the inlet exceeds a force across the topside surface (from the perspective view shown in Figure 13) of the piston head provided by fluid (that may be an environmental fluid) at the outlet alongside the biasing force provided by the spring, the valve is urged into an open configuration. It will also be appreciated that when a force across the underside surface (from the perspective view shown in Figure 13) of the piston head provided by fluid at the inlet is less than a force across the topside surface (from the perspective view shown in Figure 13) of the piston head provided by fluid (that may be an environmental fluid) at the outlet alongside the biasing force provided by the spring, the valve remains in a closed configuration. It will therefore be appreciated that valve design (for example spring stiffness and / or piston head geometry) can determine by how much a pressure of fluid at the inlet must exceed a pressure of fluid at the outlet to urge the valve into an open configuration.

[0143] Figure 14 illustrates a cross sectional view of another purge valve 1404. It will be appreciated that the purge valve 1404 shown in Figure 14 could be utilised in any of the arrangements illustrated in Figures 6 to 12. Figure 14 illustrates the purge valve in a closed configuration 1408 and an open configuration 1412.

[0144] It will be understood that the purge valve 1404 illustrated in Figure 14 is substantially similar to the valve 1304 illustrated in Figure 13. However, as shown in Figure 14 the spring seat 1414, upon which the spring 1418 is located, is a radially flared out region of the slidable member 1420. A remaining end of the spring 1418 is disposed against a radially inwardly extending termination seat 1422 of the valve housing 1426. It will be appreciated that when the valve is in the closed configuration 1408 the spring 1418 is in a partially compressed state. It will thus 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 towards the fluid inlet 1430 and thus biases the valve 1404 towards the closed configuration 1408. With similarity to the valve 1304 described with respect to Figure 13, when fluid at the fluid inlet 1430 provides a force across the underside (from the perspective view shown in Figure 14) surface of the piston head 1434 that exceeds force provided by fluid at the fluid outlet 1438 alongside the biasing force provided by the spring 1418, the valve 1404 of Figure 14 is urged into the open configuration 1408. Thus it will be understood how, to urge the valve into an open configuration, a pressure provided by fluid at the inlet 1430 (that may be fluid from the annulus region of a flexible pipe for example) must exceed a pressure at the outlet 1438 (that may for example by a pressure of a local environment) by a predetermined amount (that is determined by the construction of the valve 1408, for example the stiffness of the spring).

[0145] Throughout the description and claims of this specification, the words “comprise” and “contain” and variations of them mean “including but not limited to” and they are not intended to (and do not) exclude other moieties, additives, components, integers or steps. Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

[0146] Features, integers, characteristics or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and / or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of the features and / or steps are mutually exclusive. The invention is not restricted to any details of any foregoing embodiments. The invention extends to any novel one, or novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

[0147] The reader’s attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

Claims

CLAIMS:1 . Apparatus for purging fluid from an annulus region of a flexible pipe, comprising: a first end fitting connected to an end region of a segment of flexible pipe body and comprising a fluid communication region that is fluidly connected to an annulus region of the flexible pipe body; a first purge valve that is spaced apart from the first end fitting comprising a first valve inlet and a first valve outlet that is selectively fluidly connectable to the first valve inlet; and a lumen extending between and in fluid communication with, a fluid outlet of the first end fitting that is fluidly connectable to the fluid communication region, and the first valve inlet; wherein the first purge valve is locatable spaced apart above the fluid outlet by a distance of more than 2 meters.

2. The apparatus as claimed in claim 1 , further comprising: a hose element comprising the lumen disposed outside of the flexible pipe body and the first end fitting.

3. The apparatus as claimed in claim 1 or claim 2, further comprising: a further purge valve comprising a further valve inlet and a further valve outlet that comprises the fluid outlet and is selectively fluidly connectable to the further valve inlet so that the further purge valve selectively fluidly connects the fluid communication region and the lumen, the further purge valve optionally being supported on a body of the first end fitting.

4. The apparatus as claimed in any preceding claim, further comprising: a first flexible pipe comprising the first end fitting and the segment of flexible pipe body, the first flexible pipe being disposed in a pipeline that comprises a plurality of flexible pipes each 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 is supported on a further end fitting of a further flexible pipe, or is supported on a further segment of flexible pipe body of a further flexible pipe, the further end fitting optionally being disposed above the first end fitting.

5. The apparatus as claimed in claim 4, further comprising: the further end fitting is disposed proximate to a flexible pipe retrieval device, that optionally is a winching device, relative to the first end fitting.

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

7. The apparatus as claimed in any one of claims 1 to 3, further comprising: a buoyancy control element that comprises a buoyancy body that supports the first purge valve, the buoyancy control element optionally comprising a rigid frame member that provides support for a housing of the first purge valve.

8. The apparatus as claimed in claim 7, further comprising: a connecting element securable to the rigid frame member for connecting the rigid frame member to the segment for flexible pipe body wherein a hose element that comprises the lumen is secured in a non-taught configuration.

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

10. The apparatus as claimed in any preceding claim, wherein: the first end fitting is located in an underwater environment and the first purge valve is located in the underwater environment at a shallower depth than first the end fitting, the underwater environment comprising a water column, a local pressure at the first valve outlet optionally being a local environmental pressure provided by the water column at a submerged depth of the valve outlet.

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

12. The apparatus as claimed in any one of claims 3 to 11 , further comprising: 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 a fluid in the annulus 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 differential between the pressure at the further valve inlet and the further valve outlet is less than a further predetermined pressure differential.

13. A method of purging fluid from an annulus region of a flexible pipe, comprising the steps of: communicating fluid from an annulus region of a flexible pipe that comprises at least one end fitting, through a fluid outlet of the end fitting, the fluid outlet being fluidly connectable to the annulus region, and into a lumen that is in fluid communication with the fluid outlet; communicating the fluid through the lumen and to a first valve inlet of a first purge valve that is spaced apart from the first end fitting and comprises 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 of more than 2 meters; 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, fluidly connecting the first valve inlet and the first valve outlet; and; communicating the fluid from the first valve inlet out of the first valve outlet thereby purging fluid from the annulus region.

14. The method as claimed in claim 13, further comprising the steps of: prior to transporting the fluid through the fluid outlet, providing the fluid at a further fluid inlet of a further purge valve that is supported on the end fitting and comprises a further valve outlet, comprising the fluid outlet, that is selectively fluidly connectable to the further fluid inlet; andwhen a pressure at the further valve inlet provided by the fluid exceeds a pressure at the further valve outlet by a further predetermined pressure, fluidly connecting the further valve inlet and further valve outlet.

15. The method as claimed in claim 13 or 14, further comprising the steps of: arranging the first purge valve in an underwater environment that comprises a water column so that that the local pressure at the first valve outlet is a local environmental pressure provided by the water column at a submerged depth of the first valve outlet.

16. The method as claimed in any one of claims 13 to 15, further comprising the steps of: arranging the end fitting in an underwater environment and at a depth that is deeper than the submerged depth of the first valve outlet so that the first valve inlet and the first valve outlet are selectively fluidly connectable responsive to a pressure differential between a pressure in the annulus region provided by the fluid and the local environmental pressure at the submerged depth of the first valve outlet.

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

18. Apparatus for limiting pressure of fluid in an annulus region of a flexible pipe, comprising: a flexible pipe comprising an end fitting at an end region of a segment of flexible pipe body and disposed in an underwater environment that comprises a water column, the end fitting comprising a fluid communication region that is fluidly connected to an annulus region of the flexible pipe; a first purge valve spaced apart from and disposed above the flexible pipe comprising a first valve inlet and a first valve outlet that is selectively fluidly connectable to the first valve inlet; and a lumen extending between, and fluidly connected to, the first valve inlet and a fluid outlet of the end fitting that is fluidly connectable to the fluid communication region, the first purge valve being spaced apart above the fluid outlet by a distance of more than 2 meters; whereinthe 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 from the annulus region, exceeds a local environmental pressure at the first valve outlet by a first predetermined pressure to selectively purge fluid from the annulus region and thereby limit the pressure of fluid in the annulus region.

19. The apparatus as claimed in claim 18, further comprising: the first purge valve is disposed in the underwater environment so that the local environmental pressure at the first valve outlet is a water pressure provided by the water column at a submerged depth of the first valve outlet.

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