Pipe laying apparatus

A tubular installation apparatus (1) including a lay tower (2) mounted to a support structure (4). The lay tower (2) is configured to lower a tubular section along a firing line (L) extending along the lay tower (2). A magazine (3) is removably mounted to the lay tower (2) and configured to be pre-loaded with a plurality of tubular sections. A feed mechanism (23, 25) is configured to feed one or more tubular sections from the magazine (3) to the firing line (L) of the lay tower (2) for connection to the end of a catenary.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a national stage application under 35 U.S.C. 371 of PCT Application No. PCT/GB2019/050561 having an international filing date of 28 Feb. 2019, which designated the United States, which PCT application claimed the benefit of Great Britain Application No. 1805198.7, filed 29 Mar. 2018, each of which are incorporated herein by reference in their entirety.

This invention relates generally to pipe laying apparatus. More specifically, although not exclusively, this invention relates to a tubular installation apparatus for laying tubular sections in a pipelay process and a method of laying one or more tubular sections using a tubular installation apparatus.

Laying pipelines or tubulars, generally formed from tubular sections, is a common operation when constructing an offshore development, for example an oil and gas production facility. These pipelines are used to provide a means of communication with such a development, for example, to provide power, telecommunications or to deliver or receive fluids.

Traditionally, pipe laying operations are carried out by large, dedicated pipe laying vessels with permanently installed pipe laying systems, for example lay towers. These vessels are capable of laying pipelines in demanding, deep water environments where the stresses on the pipe laying equipment are large. Further, such pipe laying vessels are often deployed in locations best suited to their capabilities, for example near deep-water fields.

The conventional pipe laying process and apparatus for carrying out such a process makes the cost of development of marginal fields prohibitive. It also makes the development of fields located in shallower waters, for example parts of the North Sea, costly as generally a dedicated vessel must be hired that has capabilities far beyond what is required. The dedicated vessel may also have to travel some distance from its usual deep water location, the transit time increasing the mobilisation cost.

All offshore developments have a finite lifespan and/or may develop faults or failures that require intervention. In the case of subsea pipelines, the end of the useful life requires decommissioning of the infrastructure. This involves recovering subsea pipelines (pipe recovery) and cables from the seabed and bringing them back to shore for recycling. The decommissioning of subsea pipelines and of offshore infrastructure in general is becoming a progressively more pressing issue as existing assets age.

The current methods involved in pipeline decommissioning involve cutting a pipeline into sections and lifting each of the sections onto a specialist vessel using subsea craneage. This is a time and cost intensive process due to the requirement for specialist equipment. There is also a negative impact on the development of marginal fields in that a prospective operator or developer will foresee, and may be deterred by, the significant costs at the decommissioning stage of the project.

Furthermore, vessels for use in pipe laying or pipe recovery operations generally come equipped with dedicated on-board cranes or handling systems for lifting equipment on or off the vessel and/or to assist in carrying out the pipe laying or pipe recovery process.

Unfortunately, vessels with such dedicated craneage or handling systems cost more to operate and are less available than vessels without such equipment. However, vessels without such systems are limited in that they require dedicated quayside or dockside craneage to allow loading or unloading of the vessel. This reduces the availability of ports which may pose a problem when working in remote or less developed parts of the world. Extensive travel to allow loading or unloading of the vessel will increase the time and cost of a project.

The aforementioned problem is particularly acute in the case of a pipe laying or pipe recovery process where the supply of tubular sections must be restocked or recovered tubular sections must be offloaded on a regular basis.

It is therefore a first non-exclusive object of the invention to provide a tubular installation apparatus, a tubular recovery apparatus or a tubular handling apparatus that overcomes, or at least mitigates the drawbacks of the prior art.

Accordingly, a first aspect of the invention provides an apparatus comprising a tower, e.g. a lay tower, for lowering a tubular section along a firing line extending along the tower, a storage module mounted to the tower for receiving or configured to receive or be pre-loaded with a plurality of tubular sections and a feed mechanism for feeding tubular sections from the storage module to the firing line of the tower for connection to the end of a length of pipe, length of tubular, string, cable, umbilical or catenary.

The provision of a storage module pre-loaded with tubular sections fed automatically to the firing line enables the catenary to be extended more quickly and efficiently. The apparatus eradicates the need for a dedicated vessel crane or loading arm to lift tubular sections into the lay tower. Efficiency can be further increased by pre-loading storage modules on the deck ready for attachment to the lay tower. Such an apparatus can reduce the cost associated with pipe laying and is particularly advantageous in marginal and/or small fields.

The apparatus may be a tubular installation apparatus, e.g. for laying one or more tubular sections, for example in a pipelay process. The storage module may comprise or be a supply module.

In embodiments, the storage module is or may comprise a magazine, cartridge or cassette. The magazine, cartridge or cassette may have one or more receptacles for receiving (or distributing) tubular sections.

It will be understood that, hereinafter, any reference to magazine is also reference to cartridge or cassette unless stated otherwise.

The magazine may comprise a carousel. The magazine may be removably mounted to the tower. The magazine may comprise a one or more, e.g. a plurality of, receptacles or receiving areas (hereinafter receptacles) about its periphery, e.g. spaced or equispaced about its periphery. The magazine may be rotatably mounted to the tower and/or configured to selectively rotate, be selectively rotated, index or be indexed to one of a plurality of positons, e.g. when attached to the tower.

The magazine may be configured to selectively rotate, be selectively rotated, index or be indexed to align the or at least one or each receptacle with the firing line. The magazine may be configured to selectively rotate, be selectively rotated, index or be indexed based on or corresponding to the location of the or at least one or each receptacle.

The magazine may be substantially cylindrical or comprise a cylinder or a cylindrical or cylinder shaped body. The one or more receptacles may each comprise a radial slot. The one or more receptacles may be arranged around the circumference of the cylinder or body. The or each slot may be arranged to contain or receive one or more tubular sections.

The magazine may comprise a cuboid or substantially cuboid shaped body and the receptacles may be located on one or more or each of the sides of the cuboid or cuboid shaped body.

Two or more of the slots may be configured to contain or receive a different number of tubular sections. One or more of the slots may be configured to contain a number, e.g. a first number, of tubular sections and/or one or more of the slots may be configured to contain a different number, e.g. a second number different from the first number, of tubular sections.

The feed mechanism may be operable or configured to feed one or more tubular sections from the magazine to or toward the firing line. Additionally or alternatively, the feed mechanism may be operable or configured to feed one or more tubular sections from the firing line to or toward the magazine.

In embodiments, the or a feed mechanism may be configured to rotate, for example selectively rotate, or index the magazine, e.g. relative to the tower. The feed mechanism may comprise a drive mechanism configured to rotate or index the magazine. The feed or drive mechanism and the magazine may comprise cooperating gears, which may be configured to inter-engage so as to describe a geared drive mechanism.

The feed mechanism may comprise or be a pipe clamp. The feed mechanism or pipe clamp may comprise a pipe retrieval position, e.g. in which it is configured to extend into the storage module to retrieve a tubular section from the storage module. The feed mechanism or pipe clamp may comprise a firing line position, e.g. in which the or an axis of the feed mechanism or pipe clamp is on or collinear with the firing line and/or axis of the tower. The feed mechanism or pipe clamp may comprise a retracted position, e.g. in which the feed mechanism or pipe clamp is positioned away from the firing line and/or axis of the tower. The feed mechanism or pipe clamp may be movable between two or more of the retrieval position, firing line position and/or retracted position.

The pipe clamp may be movable along all or part of the tower, for example between a feed position, e.g. in which it is aligned with the supply module, and a hand-off position or take-up position. The pipe clamp may be movable or positionable to a lowered position, e.g. for connecting a tubular section to a catenary. The lowered position may be between the feed position and hand-off or take-up position.

The tower may comprise one or more, e.g. a pair of, mounting pins for mounting the magazine. The mounting pins may comprise a pair of spaced and/or opposed mounting pins, which may be arranged to coincide with the centreline of the magazine. The magazine may be configured to rotate or be rotated, e.g. about its centreline, when mounted to the tower.

The magazine may be releasably or removably mounted or releasably or removably attached to the tower, for example by a latch which may be a hydraulic latch. The latch may be located or installed on the tower and/or may cooperate with a keeper, strike or other feature on or of the magazine. Alternatively, the latch may be located or installed on the magazine and/or may cooperate with a keeper, strike or other feature on or of the tower. The latch may comprise the mounting pins.

The magazine may comprise a retaining means, for example a retainer, retaining or retention mechanism, for retaining or securing the one or more tubular sections in or within the magazine. The retaining means may comprise one or more retractable pins, which may be configured to extend at least partially across one or more or each of the receptacles of the magazine.

At least part of the tower may be movable, for example between a deployed or laying position (hereinafter deployed position), e.g. for laying tubular sections, and a loading position, e.g. for loading or mounting a magazine onto the tower. At least part of the tower may be pivotable, for example between the deployed position and the loading position. At least part of the tower may be movable or pivotable by an actuator, which may be hydraulic.

In the deployed position, the tower may describe, define and/or be aligned with the firing line. In the loading position, the tower may be misaligned or out of alignment with or at an angle, e.g. a non-zero or oblique or right angle, relative to the deployed position or the firing line. In the loading position, the tower may be aligned with a loading substrate, which may comprise a loading shuttle or loading trolley (hereinafter loading shuttle), e.g. for loading and/or unloading a magazine. The apparatus may comprise the loading substrate. In the loading position, at least part of the tower may be substantially horizontal and/or aligned with a magazine, which may be on or mounted to the loading substrate or shuttle.

In some embodiments, the apparatus may comprise the or a loading shuttle, which may be operable or configured to transfer or transport one or more magazines. The loading shuttle may be operable or configured to transfer or transport one or more magazines between a storage location, for example remote from the tower, and a loading location, for example proximal to the tower. When the apparatus is in the loading position and the loading shuttle is in the loading location, one or more magazines on or mounted to the loading shuttle may be positioned such that they can be mounted or loaded to the tower.

The apparatus may comprise a support structure or support to which the tower may be mounted, e.g. movably or pivotally mounted. The support structure may comprise a substrate, e.g. the loading substrate. The tower may comprise a hang-off clamp. The hang-off clamp may be mounted or connected to the support structure. The hang-off clamp may be fixed or secured relative to the support structure and/or immovable relative thereto. Alternatively, the hang-off clamp may be movably mounted to the support structure and/or pivotable relative thereto, for example to change the orientation or direction of the firing line. The direction or orientation of the firing line may be changed in order to align it with a stinger or guide.

In embodiments, the firing line of the tower may be aligned or substantially coaxial with the axis of the hang-off clamp, for example when the tower is in the deployed position. The tower and the hang-off clamp may together describe or define the or a firing line of the apparatus when so aligned or coaxial. The hang-off clamp may comprise a hydraulic clamp, for example a tubular or pipe clamp.

The support structure may comprise or be in the form of a skid or pallet, for example to which the tower may be mounted, for example movably or pivotably mounted. The support structure may comprise one or more lifting points, for example for connection to a crane or other lifting apparatus. The support structure may comprise a grillage structure. The support structure may comprise a guide, track or rail (hereinafter track) for receiving a loading shuttle.

The tower may comprise an attachment or joining means or mechanism, e.g. for attaching or joining or securing a tubular section fed into the firing line to the end of a catenary. The attachment or joining means may comprise a welding means, mechanism or apparatus, for example a welder, or a pipe-thread tightener. A catenary, for example a free end thereof, may be suspended or suspendable by the hang-off clamp.

Additionally or alternatively, the tower may comprise a cutting or separating means or mechanism, e.g. for separating or decoupling a length of tubular from a catenary.

The apparatus or tower may comprise a recovery tower or a lay tower capable of pulling, recovering and/or retrieving a tubular section, e.g. from the firing line and/or from the end of a length of pipe, length of tubular, string, cable, umbilical or catenary. The storage module may be for receiving or configured to be loaded with a plurality of recovered tubular sections and a feed mechanism for retrieving, transferring or feeding tubular sections from the firing line of the tower to the storage module.

A further aspect of the invention provides an apparatus comprising a tower, e.g. a recovery tower, for pulling, recovering and/or retrieving a tubular section from a firing line extending along the tower, a storage module mounted to the tower for receiving or configured to be loaded with a plurality of recovered tubular sections and a feed mechanism for retrieving, transferring or feeding tubular sections from the firing line of the tower to the storage module.

Having a storage module into which recovered tubular sections can be loaded without having to pull up, decouple and lay down individual tubular sections from the firing line to the deck or other area simplifies the pipe recovery process and enables a catenary to be decommissioned more quickly and efficiently. The apparatus eradicates the need for a dedicated subsea craneage to lift a catenary into the recovery tower. Efficiency can be further increased by having a plurality of empty storage modules on the deck ready for attachment to the recovery tower. Having storage modules filled with recovered tubular sections also eases the offloading of the recovered tubular sections from the vessel. Such an apparatus can reduce the cost associated with pipe decommissioning.

The apparatus may be a tubular recovery apparatus, e.g. for pulling or recovering one or more tubular sections from the end of a length of pipe, length of tubular, string, cable, umbilical or catenary (hereinafter catenary), for example in a decommissioning process.

When the tower is configured to recover or retrieve a tubular section, the aforementioned tower deployed position may comprise or function as a pulling position, e.g. for recovering tubular sections. Similarly, when the tower is configured to recover or retrieve a tubular section, the aforementioned tower loading position may comprise or function as an unloading position, e.g. for unloading a magazine from the tower. All features described above in relation to the tower and its movement between the deployed and loading positions apply to movement of the recovery tower between its deployed or pulling position and its unloading position.

When the tower is configured to recover or retrieve a tubular section, the aforementioned feed mechanism pipe retrieval position may comprise or function as a pipe loading position, e.g. in which it is configured to load a tubular section into the storage module. All features described above in relation to the feed mechanism and its movement between the pipe retrieval, firing line and retracted positions apply to movement thereof between its pipe loading, firing line and retracted positions.

The tower may comprise a hoisting means, for example a hoist or hoisting mechanism, which may be for lifting objects or operable to lift, in use, objects. The tower may be movable, for example between a first position, e.g. at which the hoisting means is on a first side of the tower, and a second position, e.g. at which the hoisting means is on a second side of the tower.

A further aspect of the invention provides an apparatus comprising a tower, e.g. a lay tower or recovery tower, and a hoisting means, e.g. a hoist or hoisting mechanism for lifting objects, wherein the tower is movable between a first position, configuration or orientation, e.g. at which the hoisting means is on a first side of the tower, and a second position, configuration or orientation, e.g. at which the hoisting means is on a second side of the tower.

The provision of a lay tower or recovery tower capable of operating as a handling apparatus eradicates the need for a dedicated vessel crane, which can reduce the cost of a pipe laying process, pipe recovery process or general vessel hire. Additionally, such an apparatus can increase the availability and flexibility of a vessel in that dedicated quayside craneage is not necessary. Therefore, smaller or more remote ports are available to a vessel the with the apparatus. As pipe laying or pipe recovery operations often take place in remote places, having such an apparatus is advantageous in that extensive travel to find a suitable port or quay may not be required, saving time and cost.

The apparatus may be a tubular handling apparatus, e.g. for moving, raising, lowering and/or handling one or more tubular sections, supply modules or objects from one location to another.

The second side may be opposed or opposite, e.g. diametrically opposed or opposite, the first side. The second side may be beside, e.g. orthogonal to, the first side. The tower may be movable, e.g. pivotable, between the first position, configuration or orientation (hereinafter position), the second position and a third position, e.g. in which the tower describes the or a firing line. The third position may be between the first and second positions. The tower may be movable, e.g. pivotable, between the first position and the second position via or through the third position.

The tower may describe an acute angle with the or a support structure, for example to which the tower is mounted, in the first position and/or may describe an obtuse angle therewith in the second position.

The tower may be mounted to the support structure by or via a linkage, for example an articulated linkage. The linkage may comprise an extendable member, for example a telescopic member. The extendable member may comprise an actuation means, such as an actuator that may be hydraulic or pneumatic, for example a hydraulic or pneumatic cylinder. The extendable member may be configured to actuate and/or move or pivot the tower, for example between the first position and second position and/or between the deployed position and the loading position. The third position may comprise or correspond to the deployed position.

The linkage may comprise a member, e.g. a first member, that may be connected between or may interconnect the extendable member and the support structure. The linkage may comprise a further member, e.g. a second member, that may be connected between, or may interconnect, the first member and the tower.

The tower may comprise or be a J-lay tower. Alternatively, the tower may be compatible with any of J-lay, S-lay, reel-lay and/or flex lay processes.

The hoist may comprise a winch. Alternatively, the hoist may comprise one or more sheaves and/or a block and tackle. The hoist may comprise a travelling pipe clamp, which may be configured to travel along the firing line. In some embodiments, the or a hoist may be arranged to suspend and lower a catenary along the firing line. Additionally or alternatively, the or a hoist may be arranged to pull or recover a tubular section along the firing line.

The tubular installation apparatus and/or tubular recovery apparatus may be configured into the tubular handling apparatus.

According to another aspect of the invention there is provided a storage module for use with an apparatus, e.g. as described above, the supply module may comprise a magazine having one or more receptacles for receiving tubular sections and/or may be mountable to a tower, e.g. a lay tower or recovery tower.

According to another aspect of the invention there is provided a vessel or barge comprising an apparatus, e.g. as described above.

According to another aspect of the invention there is provided a method of laying one or more tubular sections, the method comprising feeding a tubular section into a firing line extending along a tower, e.g. lay tower, from a storage module mounted thereto and pre-loaded with a plurality of tubular sections.

The method may comprise feeding the tubular section into the firing line for connection to the end of a length of pipe, length of tubular, string or catenary (hereinafter catenary).

The method may comprise mounting or removing a storage module. The method may comprise mounting a pre-loaded storage module and/or removing an empty, vacant or unloaded or at least partially empty, vacant or unloaded storage module.

The method may comprise positioning, configuring or moving the tower into a loading position e.g. for loading or mounting a magazine onto the tower, e.g. prior to mounting the pre-loaded magazine or at least partially vacant magazine. The method may comprise moving the tower from the loading position to a deployed position, e.g. for laying tubular sections or pulling tubular sections, with the magazine mounted.

The method may comprise attaching, connecting, joining or securing a tubular section fed into the firing line to the end of a catenary. The method may comprise connecting a tubular section by means of a mechanical connection. The method may comprise screwing a tubular section to the end of a catenary. Alternatively, the method may comprise welding a tubular section to the end of a catenary.

The method may comprise lowering the catenary with the attached tubular section and/or feeding a further tubular section from the magazine to the firing line of the tower. The method may comprise lowering the catenary using a hoist or a travelling pipe clamp.

The method may comprise hanging or suspending the catenary from a hang-off clamp, for example a hydraulic clamp. The method may comprise releasing the hang-off clamp prior to lowering the catenary and re-engaging the hang-off clamp to suspend the catenary prior to attaching a further tubular section.

In some embodiments, once the magazine is at least partially empty or at least partially vacant, the method may comprise moving the tower from the deployed, laying position to the loading position and optionally releasing or unmounting the magazine from the tower.

The method may comprise pivoting the tower, for example by operating a hydraulic actuator.

The method may comprise, when mounting and/or unmounting the magazine, operating a hydraulic latch.

In some embodiments, the method may comprise transferring a loading shuttle with a pre-loaded magazine. The method may comprise transferring the loading shuttle from a storage location, which may be remote from the tower, to a loading location, for example proximal to the tower. The method may comprise transferring the load shuttle prior to mounting the magazine to the tower.

In some embodiments, the method may comprise transferring a loading shuttle with an at least partially vacant or at least partially empty magazine between a storage location and a loading location, e.g. prior to mounting the or a further magazine to the tower and/or after unmounting the magazine from the tower.

The method may comprise transferring a loading shuttle with a magazine that is at least partially full, e.g. from the loading location after unmounting the magazine from the tower. The method may comprise positioning, configuring or moving the tower into a loading position, e.g. prior to mounting the at least partially empty or at least partially vacant magazine. The method may comprise moving the tower from the loading position to a deployed, pulling position, e.g. for recovering tubular sections, with the magazine mounted.

The method may comprise forming a tubular section by decoupling or separating a length of tubular pulled into the firing line of the tower. The method may comprise feeding the tubular section from the firing line into the magazine. The method may comprise pulling a further length of tubular into the firing line of the tower.

The method may comprise, once the magazine of recovered tubular sections is at least partially full, moving the tower from the deployed, pulling position to the loading position and/or removing or unmounting the magazine from the tower.

In some embodiments, moving the tower from the first position to the second position includes or requires moving through a third position, e.g. in which the tower describes a firing line. Moving the tower from the first position to the second position may involve or require pivoting thereof.

The method may comprise pulling, recovering and/or retrieving a tubular section from the firing line into the storage module. The tower may comprise a recovery tower.

According to a further aspect of the invention there is provided a method of recovering one or more tubular sections, the method comprising pulling, recovering and/or retrieving a tubular section from a firing line extending along a recovery tower into a storage module mounted thereto and pre-loaded with a plurality of tubular sections.

The method may comprise separating or decoupling a length of tubular from a catenary, e.g. prior to pulling, recovering and/or retrieving a tubular section from a firing line.

The method may comprise mounting or removing a storage module. The method may comprise removing a loaded or partially loaded storage module and/or mounting an empty, vacant or unloaded or at least partially empty, vacant or unloaded storage module.

The method may comprise the use of an apparatus, e.g. as described above.

According to another aspect of the invention there is provided a method of moving an object using a tower, e.g. a lay tower or recovery tower, having a hoisting means, the method comprising positioning the tower in a first position in which the hoisting means is on a first side of the tower, lifting an object located on the first side of the tower with the hoisting means such that it is suspended and moving the tower from the first position to a second position in which the hoisting means is on a second side of the tower.

In some embodiments, once the tower is in the second position, the object is lowered using the hoist. The hoist may be attached to the object or the object may be attached to the hoist via a lifting cable.

For the avoidance of doubt, any of the features described herein apply equally to any aspect of the invention.

Another aspect of the invention provides a computer program element comprising and/or describing and/or defining a three-dimensional design for use with a simulation means or a three-dimensional additive or subtractive manufacturing means or device, e.g. a three-dimensional printer or CNC machine, the three-dimensional design comprising an embodiment of the supply module described above.

A further aspect of the invention provides a computer program element comprising computer readable program code means for causing a processor to execute a procedure to implement one or more steps of the aforementioned methods. A yet further aspect of the invention provides the computer program element embodied on a computer readable medium. A yet further aspect of the invention provides a computer readable medium having a program stored thereon, where the program is arranged to make a computer execute a procedure to implement one or more steps of the aforementioned method. A yet further aspect of the invention provides a control means or control system or controller comprising the aforementioned computer program element or computer readable medium.

For purposes of this disclosure, and notwithstanding the above, it is to be understood that any controller(s), control units and/or control modules described herein may each comprise a control unit or computational device having one or more electronic processors. The controller may comprise a single control unit or electronic controller or alternatively different functions of the control of the system or apparatus may be embodied in, or hosted in, different control units or controllers or control modules. As used herein, the terms “control unit” and “controller” will be understood to include both a single control unit or controller and a plurality of control units or controllers collectively operating to provide the required control functionality. A set of instructions could be provided which, when executed, cause said controller(s) or control unit(s) or control module(s) to implement the control techniques described herein (including the method(s) described herein). The set of instructions may be embedded in one or more electronic processors, or alternatively, may be provided as software to be executed by one or more electronic processor(s). For example, a first controller may be implemented in software run on one or more electronic processors, and one or more other controllers may also be implemented in software run on or more electronic processors, optionally the same one or more processors as the first controller. It will be appreciated, however, that other arrangements are also useful, and therefore, the present invention is not intended to be limited to any particular arrangement. In any event, the set of instructions described herein may be embedded in a computer-readable storage medium (e.g., a non-transitory storage medium) that may comprise any mechanism for storing information in a form readable by a machine or electronic processors/computational device, including, without limitation: a magnetic storage medium (e.g., floppy diskette); optical storage medium (e.g., CD-ROM); magneto optical storage medium; read only memory (ROM); random access memory (RAM); erasable programmable memory (e.g., EPROM ad EEPROM); flash memory; or electrical or other types of medium for storing such information/instructions.

Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination, unless such features are incompatible. For the avoidance of doubt, the terms “may”, “and/or”, “e.g.”, “for example” and any similar term as used herein should be interpreted as non-limiting such that any feature so-described need not be present. Indeed, any combination of optional features is expressly envisaged without departing from the scope of the invention, whether or not these are expressly claimed. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner.

Referring now toFIG. 1, there is shown a tubular installation apparatus1according to an embodiment of the invention which includes a lay tower2having a supply module3mounted thereto. The lay tower2is pivotally connected to a support structure4via linkage5configured to pivot the lay tower2. A loading shuttle6is engaged with and configured to traverse the support structure4. A hang-off clamp7is pivotally mounted to the support structure4in this embodiment such that the lay tower2and hang-off clamp7share a common pivot axis.

InFIG. 1, the lay tower2is shown in a deployed position in which it is aligned with the firing line L. The firing line L is described by the axis of the hang-off clamp7. The firing line L describes the line along which tubular sections are laid or pulled. The lay tower2and firing line L are perpendicular to the support structure4in this configuration. The lay tower2is pivotally connected to the support at pivot point21.

Extending from the second end22of the lay tower2in the direction of the pivot point21is an internal pipe clamp23. The internal pipe clamp23has a first or top position shown inFIG. 1and a second or lower position in which it lies proximate or adjacent the hang-off clamp7. The internal pipe clamp23also has an intermediate position between the first position and the second position in which it can engage a tubular section fed into the firing line L. The internal pipe clamp23is movable between the first, intermediate and second positions.

Mounted to and extending from a first side2aof the lay tower2are a pair of spaced, opposed mounts or mounting pins24a,24b. The first mounting pin, or base pin24ais fixed relative to the lay tower2and the second mounting pin24bis movable relative to the lay tower2. The second mounting pin24bis hydraulically actuated in this embodiment. The second mounting pin24bis configured to pivot about the axis of the lay tower2in this embodiment. In some embodiments, the second mounting pin24bis configured to move along the axis of the lay tower2. The pair of opposed mounting pins24a,24bare collinear.

Mounted to and protruding from a second side2bof the lay tower2is a pipe clamp25arranged to close around and grip the outer surface of a tubular section. The pipe clamp25is movable between and can take up any of three positions in the present embodiment. The first position is a firing line position in which the axis of the pipe clamp25is collinear with the firing line L. The second position is a pipe retrieval/loading position in which the pipe clamp25extends into the supply module3such that it can retrieve a tubular section from the supply module3and/or load a tubular section into the supply module3. The third position is a retracted position in which the pipe clamp25is positioned away from the firing line L. The pipe clamp25is configured to traverse all or part of the length of the lay tower2in this embodiment from a feed position as shown inFIG. 1in which it is aligned with the supply module3to a hand-off position or take-up position. Between the feed position and hand-off position is a lowered position which allows a tubular section to be connected to a catenary. In the lowered position a tubular section is brought into abutting relationship with the end of a catenary. In some embodiments, in the hand-off position, the pipe clamp25lies proximate or adjacent the hang-off clamp7. In some embodiments, the hand-off position is the lowered position. The pipe clamp25is a hydraulic pipe clamp in this embodiment.

In the present embodiment, the pipe clamp25provides a feed mechanism arranged to feed a tubular section from the supply module3into the firing line L and/or feed a tubular section from the firing line L into the supply module3. The lay tower2also includes a drive mechanism (not shown) which forms part of the feed mechanism in this embodiment. The drive mechanism is in the form of a geared drive mechanism arranged to rotate the supply module3when mounted to the lay tower2.

The supply module3(as shown in more detail inFIGS. 2 to 4) is in the form of a magazine in this embodiment. The supply module3is rotatably mounted to the lay tower2between the mounting pins24a,24bsuch that the mounting pins24a,24bare aligned with an axis31of the supply module3. The supply module3has an aperture32centred on the axis31and extending the length of the supply module3. When mounted on the lay tower2the mounting pins24a,24bextend into the aperture32of the supply module3.

The supply module3has a circular cross section and a cylinder-shaped body in this embodiment. A first end of the supply module3has a first securing mechanism33athat lies substantially flush with an end of the supply module3. A second securing mechanism33bprotrudes from the other end of the supply module3. Each of the first and second securing mechanisms33a,33bare in in the form of a resiliently biased clamp for facilitating attachment to the lay tower2.

The supply module3has a plurality of receptacles34in the form of radial slots arranged around the circumference of the supply module3in this embodiment. The receptacles34are each configured to receive one or more tubular sections.

The supply module3has a retention mechanism in the form of retractable pins35(FIG. 4) configured to extend partially across each of the plurality of receptacles34.FIG. 4shows the retractable pins35in a deployed condition.

The supply module3has a further retention mechanism in the form of retainer lips (not shown) located at either end of the supply module3. In the case of tubular sections having end fittings or pipe joints having a greater diameter than the tubular section, the end fittings or pipe joints abut and are supported by the retainer lips.

FIG. 2shows an alternative retention mechanism, to that of retractable pins35, in the form of a pair of spaced retention belts135arranged to circumscribe the supply module3.

Referring back toFIG. 1, the support structure4is in the form of a skid in this embodiment and has a first, mounting portion41and a second, loading portion42. The mounting portion41has a greater thickness than the loading portion42. The mounting portion41and loading portion42are formed separately and connected together in this embodiment.

The mounting portion41has a web43extending therefrom and to which the lay tower2is pivotally mounted. The loading portion42has a track44described therein and configured to receive the loading shuttle6. The support structure4has a grillage structure (not shown).

The support structure4has lifting points (not shown) in this embodiment for attachment to an external lifting apparatus.

The linkage5includes a telescopic member51pivotally connected at a first end51ato the first side2aof the lay tower2and pivotally connected at a second end51bto the first end52aof a first member52. A second end52bof the first member52is pivotally connected to the support structure4. A second member53is pivotally connected at a first end53ato the first member52intermediate of its ends52a,52band pivotally connected at a second end53bto the first side2aof the lay tower2. The telescopic member51is hydraulically actuated in this embodiment.

The loading shuttle6engages the track44of the support structure4. The loading shuttle6has wheels61in this embodiment to allow for movement of the shuttle6along the track44. The loading shuttle6also has a pair of spaced load supports62. The loading shuttle6is shown in a loading location63.

The hang-off clamp7is pivotally mounted to the web43of the support structure4at pivot point71. The firing line L extends along the axis of the lay tower2and along the axis of the hang-off clamp7. The axis of the pipe clamp25when in the firing line position, the axis of the lay tower2and the axis of the hang-off clamp7are coaxial when the apparatus1is in the deployed condition. The hang-off clamp7is in the form of a hydraulic pipe clamp similar to pipe clamp25and arranged to close around and grip the outer surface of a tubular section.

Referring now toFIG. 5, there is shown the apparatus1with the lay tower2in an intermediate position between the deployed position ofFIG. 1and a loading position as shown inFIG. 7. The lay tower2forms an acute angle with the support structure4in this position. The axis of the lay tower2is not aligned with the firing line L as described by the axis of the hang-off clamp7.

With the lay tower2in this position, the telescopic member51is in a greater state of retraction relative to the telescopic member51ofFIG. 1.

Referring now toFIG. 6, there is shown the lay tower2in an alternative deployed position to that ofFIG. 1. As inFIG. 5, the lay tower2forms an acute angle with the support structure4when in this position. Further, the telescopic member51is in a greater state of retraction relative to the telescopic member51in bothFIGS. 1 and 5.

In the configuration ofFIG. 6, the hang-off clamp7has been rotated about pivot point71such that the axis of the lay tower2is coaxial with the axis of the pipe clamp25when in the firing line position and the axis of the hang-off clamp7. In this configuration, the firing line L forms an acute angle with the support structure4.

Referring now toFIG. 7, there is shown the lay tower2in the loading position. In this position, the lay tower2has been rotated about pivot point21with the support structure4such that it lies parallel to the support structure4. In this configuration, the axis of the lay tower2lies perpendicular to the firing line L as described by the axis of the hang-off clamp7.

In this configuration, the loading shuttle6is in the loading location63such that when the lay tower2is in the loading position, the pair of load supports62are positioned to support the supply module3if dismounted from the lay tower2.

Referring now toFIG. 8, there is shown the lay tower2in the loading position as perFIG. 7with the supply module3dismounted and supported by the loading shuttle6. In this case, the second mounting pin24bhas been rotated about the axis of the lay tower2such that it does not obstruct movement of the loading shuttle6along the track44when the supply module3is mounted thereto.

In this configuration, the loading shuttle6has been moved along the track44away from the mounting portion41and such that the first mounting pin24ano longer engages the aperture32of the supply module3. Referring now toFIG. 9there is shown the apparatus1in the configuration ofFIG. 6mounted on a vessel9. The storage location64is shown where supply modules3are stored prior to being transported to the loading location63.

In use, when laying one or more tubular sections, a supply module3having a plurality of tubular sections stored therein is transferred from the storage location64to the loading location63along the track44of the support structure4using the loading shuttle6. During this transfer the retractable pins35of the retention mechanism are deployed such that inadvertent falling of tubular sections from the supply module3is prevented. Alternatively, any other suitable retention mechanism may be deployed.

With the lay tower2in the loading position, the loading shuttle6is moved along the track44until the first mounting pin24aengages the aperture32of the supply module3via the first securing mechanism33a. Once the first mounting pin24ais engaged, the second mounting pin24bis rotated about the axis of the lay tower2so as to engage the aperture32of the supply module3via the second securing mechanism33bsuch that the supply module3is rotatably mounted between the mounting pins24a,24b.

The lay tower2is then pivoted relative to the support structure4by extending the telescopic member51via hydraulic actuation.

The lay tower2is pivoted about pivot point21from the loading position to a deployed position in which the lay tower2axis is collinear with the firing line L described by the hang-off clamp7.

Once in the deployed position, the supply module3is selectively rotated or indexed using the drive mechanism to align one of the receptacles34such that a tubular section can be fed from the receptacle34to the firing line L. Once in the deployed position, the retractable pins35are retracted such that tubular sections can be fed from the supply module3.

Once a receptacle34is aligned, the pipe clamp25in the feed position aligned with the supply module3, is configured into the pipe retrieve/load position such that it can feed a tubular section from the receptacle34.

In embodiments, the retractable pins35associated with a given receptacle34are only retracted when said receptacle34is aligned, all other retractable pins35remaining in a deployed position until their respective receptacle34is aligned.

Once the tubular section is gripped by the pipe clamp25in the pipe retrieve/load position, the pipe clamp25is configured into the firing line position such that the tubular section lies along the firing line L.

The pipe clamp25is then moved along the firing line L to a lowered position so as to lower the tubular section until an end of the tubular section contacts or abuts the end of a catenary suspended by the hang-off clamp7. The tubular section is attached to the end of the catenary by mechanical connection in the present embodiment.

The internal pipe clamp23is then lowered from its first position to its intermediate position so as to engage an interior of the tubular section attached to the end of the catenary.

Once the tubular section is attached and the internal pipe clamp23engaged, the pipe clamp25and the hang-off clamp7are disengaged. The internal pipe clamp23is configured to take up the weight of the catenary and lower the catenary along the firing line L to the second position of the internal pipe clamp23. Prior or during lowering of the catenary, the pipe clamp25is configured into the retracted position and returned to the feed position.

The hang-off clamp7is then re-engaged so as to grip the catenary with the new tubular section attached. The internal pipe clamp23is then returned to its first position.

If a given tubular section is the first to be laid, the hang-off clamp7is in a disengaged condition and the internal pipe clamp23lowers the tubular section through the hang-off clamp7. Once the internal pipe clamp23reaches its second position, the hang-off clamp7grips the tubular section and the internal pipe clamp23disengages and is returned to its first position.

Another tubular section is fed from the same receptacle34as the previous one and the process is repeated. Alternatively, if a given receptacle34is exhausted of tubular sections, the supply module3is selectively rotated or indexed to align another receptacle34such that a further tubular section can be fed into the firing line L and the process is repeated.

Once the supply module3is exhausted or at least partially exhausted, the lay tower2is pivoted about pivot point21relative to the support structure4into the loading position via hydraulic actuation of the extendable member51. The supply module3is supported by an empty loading shuttle6in the loading location63.

The second mounting pin24bis rotated relative to the supply module3such that it lies out of the path of the supply module3on the loading shuttle6when moved along the track44.

The empty or partially empty supply module3is transferred along the track44to the storage location64.

The same or another loading shuttle6with a supply module3having a plurality of tubular sections is transferred from the storage location64to the loading location63where it can be attached to the lay tower2and the process above is repeated.

Although the apparatus1is described as being a tubular installation apparatus1for laying one or more tubulars above, this need not be the case. The apparatus1may be a tubular recovery apparatus used to pull or recover one or more tubulars, in which case the lay tower2becomes a recovery tower2.

In use, when pulling or recovering one or more tubular sections, an at least part empty or part vacant supply module3is transferred from the storage location64to the loading location63along the track44of the support structure4using the loading shuttle6. During this transfer the retractable pins35of the retention mechanism are deployed if the supply module is part empty such that inadvertent falling of tubular sections from the supply module3is prevented.

With the recovery tower2in the loading position, the loading shuttle6is moved along the track44until the first mounting pin24aengages the aperture32of the supply module3. Once the first mounting pin24ais engaged, the second mounting pin24bis rotated about the axis of the recovery tower2so as to engage the aperture32of the supply module3such that the supply module3is rotatably mounted between the mounting pins24a,24b.

The recovery tower2is then pivoted relative to the support structure4about pivot point21by extending the telescopic member51via hydraulic actuation.

The recovery tower2is pivoted from the loading position to a deployed position in which the recovery tower2axis is collinear with the firing line L described by the axis of the hang-off clamp7.

Once in the deployed position, the supply module3is selectively rotated or indexed using the drive mechanism to align one of the vacant or partially vacant receptacles34such that a tubular section can be fed from the firing line L to the receptacle34. Once in the deployed position, if the supply module is only partially vacant, the retractable pins35are retracted such that tubular sections can be fed to the supply module3.

With the end of a catenary suspended by the hang-off clamp7, the internal pipe clamp23is moved along the firing line L from its first position to its second position. When in the second position, the internal pipe clamp23engages an end of the catenary. With the internal pipe clamp23engaged, the pipe clamp25and the hang-off clamp7are disengaged. The internal pipe clamp23takes the weight of the catenary and is moved along the firing line L toward the first position, pulling the catenary along the firing line.

Once at or near the first position, the hang-off clamp7is re-engaged so as to grip the catenary. A tubular section is decoupled from the catenary by cutting the length of catenary located between the internal pipe clamp23and hang-off clamp7.

With a receptacle34aligned and a tubular section decoupled, the pipe clamp25is configured into the pipe retrieval/load position so as to feed the decoupled tubular section from the firing line L into the receptacle34.

Once a tubular section is fed into the receptacle, the pipe clamp25is configured into the retracted position and the process is repeated. If a given receptacle34is full, the supply module3is selectively rotated or indexed to align another receptacle34such that a further tubular section can be fed from the firing line L and the process is repeated.

Once the supply module3is full or at least partially full, the recovery tower2is pivoted relative to the support structure4into the loading position. The supply module3is supported by an empty loading shuttle6in the loading location63.

The second mounting pin24bis rotated relative to the supply module3such that it lies out of the path of the supply module3on the loading shuttle6when moved along the track44.

The full or partially full supply module3is transferred along the track44to the storage location64.

The same or another loading shuttle6with a vacant or partially vacant supply module3is transferred from the storage location64to the loading location63where it can be attached to the recovery tower2and the process above is repeated.

It will be appreciated by those skilled in the art that several variations to the aforementioned embodiments are envisaged without departing from the scope of the invention. For example, although it is described that the pipe clamp25and hang-off clamp7are arranged to close around and grip the outer surface of a tubular section, this need not be the case. Instead, either or both pipe clamp25and hang-off clamp7may be arranged to close around the outer surface of a tubular section such that an end fitting of a tubular section is supported by the pipe clamp, i.e. the end fitting of the tubular section has a greater diameter than that described by the closed pipe clamp.

Additionally, although the feed mechanism is described as being the pipe clamp25, this need not be the case. Instead, the feed mechanism may be a separate feed mechanism, for example, pair of spaced counter-rotating rollers. Alternatively, the feed mechanism may be in the form of a mechanical arm in the lay tower or recovery tower2or a spring-loaded mechanism located within the supply module3. Additionally, the pipe clamp25may receive a tubular section from the separate feed mechanism and be configured to traverse the lay tower or recovery tower2.

The internal pipe clamp23may be an external pipe clamp configured to at least partially extend over an end of a tubular section.

In embodiments, the pipe clamp25may be used instead of the internal pipe clamp23for lowering or pulling tubular sections along the firing line L. In the case of lowering tubular sections, the pipe clamp25is configured into the pipe retrieve/load position so as to grip a tubular section. The pipe clamp25is then configured into the firing line position such that the tubular section lies along the firing line L. The pipe clamp25is then moved along the firing line L to a lowered position so as to lower the tubular section until an end of the tubular section contacts or abuts the end of a catenary suspended by the hang-off clamp7. The tubular section is attached to the end of the catenary by mechanical connection in the present embodiment. Once the tubular section is attached, with the pipe clamp25still gripping the tubular section, the hang-off clamp7is disengaged and the pipe clamp25is lowered to the hand-off position such that the entire catenary with the attached tubular section is lowered.

The hang-off clamp7is then re-engaged so as to grip the catenary with the new tubular section attached and the pipe clamp25is disengaged and configured into the retracted position. In the retracted position, the pipe clamp25is returned to the feed position.

If a given tubular section is the first to be laid, the hang-off clamp7is in a disengaged condition and the pipe clamp25lowers the tubular section through the hang-off clamp7. Once the pipe clamp25reaches the hand-off position, the hang-off clamp7grips the tubular section and the pipe clamp25disengages, is configured into the retracted position and returns to the feed position.

In the case of pulling tubular sections, with the end of a catenary suspended by the hang-off clamp7, the pipe clamp25is moved along the firing line L from the feed position to the take-up position and is configured into the firing line position. When in the firing line position, the pipe clamp25grips the catenary. With the pipe clamp25engaged, the hang-off clamp7is disengaged and the pipe clamp25is moved along the firing line L toward the feed position, pulling the catenary along the firing line.

Once at or near the feed position, the hang-off clamp7is re-engaged so as to grip the catenary. A tubular section is decoupled from the catenary by cutting the length of catenary located between the pipe clamp25and hang-off clamp7.

With a receptacle34aligned and a tubular section decoupled, the pipe clamp25is configured into the pipe retrieval/load position so as to feed the decoupled tubular section from the firing line L into the receptacle34.

Further, the drive mechanism may be separate to the feed mechanism and instead of being a geared drive it may be belt and pulley type system.

Although the supply module3is described as having a retention mechanism in the form of retractable pins35or retention belts135in combination with pipe lips (not shown), this need not be the case. Instead, the supply module3may have any, all or none of retractable pins35, retention belts135and pipe lips (not shown).

Although the tubular section is described as being attached to the end of the catenary by mechanical connection, this need not be the case. Instead, a tubular section may be attached to the end of the catenary by welding or any other suitable means of connection.

Referring now toFIG. 10, there is shown a tubular handling apparatus100according to an embodiment of the invention wherein like features to those of tubular installation apparatus and/or tubular recovery apparatus1are denoted by like references.

The lay tower2is shown in a first position in which it describes an acute angle with the support structure4. A hoist8is located at the second end22end of the lay tower2.

The hoist8extends away from the second side2bof the lay tower2in this embodiment. The hoist8has a top member81having lifting line82of fixed length extending therefrom. At the free end of the lifting line82is a lifting accessory83in the form of a shackle in this embodiment.

A supply module3is located below the lifting line82on a loading shuttle6in the loading location63such that a projected line from the lifting line82bisects the supply module3.

Referring now toFIG. 11, there is shown the tubular handling apparatus100in the same, first position as perFIG. 10but with the supply module3suspended above the support structure4and from the end of the lifting line82. The lifting accessory83is engaged with a lifting point (not shown) located to the centre of the supply module3.

Referring now toFIG. 12, there is shown the tubular handling apparatus100with the supply module3suspended from the end of the lifting line82and in the third position. In the third position the lay tower2extends perpendicularly to the support structure3. The telescopic member51is in a lesser state of retraction than inFIGS. 10 & 11such that the lay tower2is pivoted relative to the support structure4about pivot point21. The supply module3is suspended partly over the support structure4and partly out with it.

The lay tower2has an opening (not shown) through which the supply module3extends in the third position such that part of the supply module is suspended over the support structure4and partly out with it.

Referring now toFIG. 13, there is shown the tubular handling apparatus100mounted on a vessel9. The tubular handling apparatus100is shown with the supply module3suspended from the end of the lifting line82. In this case, the lay tower2is in the second position in which it describes an obtuse angle with the support structure4. The first position and second position are diametrically opposed to one another in the present embodiment.

The telescopic member51is in a lesser state of retraction than inFIGS. 10 to 12and the supply module3is suspended out with the support structure4.

FIG. 13also discloses a dock110with a truck120for receiving the supply module3.

Referring now toFIG. 14, there is shown the tubular handling apparatus100as perFIG. 13mounted to vessel9but with the suspended supply module3rotated 90 degrees relative to that ofFIG. 13.

In use, with the tubular handling apparatus100mounted on a vessel9and with a supply module3located in the loading location63, the lay tower2is configured into the first position in which the hoist8is located above the first side2aof the lay tower2and above the supply module3.

The lifting line82extends from the top member81such that the lifting accessory83can be attached to the supply module3at the lifting point (not shown). The lay tower2is pivoted relative to the support structure4a sufficient amount such that the lifting line82can be attached to the supply module3. Once the supply module3is attached, the lay tower2is pivoted relative to the support structure4so as to lift the supply module3above the support structure4. In the present embodiment, the lifting line82is of a length such that the supply module3is lifted to a sufficient height such that it will clear any lay tower2structure in moving the lay tower2from the first position to the second position.

With the supply module3attached to the lifting line82, the telescopic member51is hydraulically actuated to reduce its state of retraction and pivot the lay tower2relative to the support structure4. Pivoting the lay tower2causes it to move through the third position to the second position. In the second position, the supply module3is suspended over the truck120on the dock110and the hoist8is located above the second side2bof the lay tower2.

In moving from the first position to the second position, the supply module3passes through an opening (not shown) in the lay tower2. Once in the second position, the lay tower2is pivoted a sufficient amount until the supply module3is supported on the trailer of the truck120. The lifting accessory83is then detached from the supply module3.

Although the apparatus100is described as transferring a supply module3from the first side2aof the lay tower2to the second side2bof the lay tower2, this need not be the case. The same process as above may be followed in transferring a supply module3or any other object from the second side2bto the first side2a, for example when loading onto a vessel9.

Although the hoist8is described as having a lifting line82of fixed length extending from a top member81, this need not be the case. Instead the hoist8may comprise a winch. The winch having a drum attached or mounted to the top member and arranged to store a length of lifting line. The lifting line may be payed out from the drum so that it can be attached to the supply module3. Once the supply module3is attached, the hoist8may be operated to draw the lifting line in and lift the supply module3above the support structure4a sufficient amount to clear any lay tower2structure.

Once in the second position, the lifting line may be payed out so as to lower the supply module3.

Alternatively, the hoist8may comprise a winch attached to a vessel9or to the support structure4. The hoist8may have one or more sheaves attached or mounted to the top member and arranged to receive a lifting line from the winch. The lifting line from the winch is passed around the sheaves and attached to the supply module3with the lay tower2in the first position. The lifting line may be drawn into the winch so as to lift the supply module, utilising the mechanical advantage provided by the sheaves.

The supply module3may be transported by operating the winch in concert with movement of the lay tower2from the first position to the second position such that the load remains suspended.

Further, although it is shown that the tubular handling apparatus100is used for lifting and transporting a supply module3, this need not be the case. The tubular handling apparatus100may be used to lift and transport any suitable object.

Although it is shown that the supply module3is lowered on to the trailer of the truck120this need not be the case. Instead, the supply module3may be lowered directly on to the ground or any other supporting surface.

Although the tubular handling apparatus100is described as transporting an object by pivoting the lay tower2from the first position through the third position to the second position by passing the object through an opening in the lay tower2, this need not be the case. Instead, the lay tower2may be rotatable about the axis of the lay tower2with a constant orientation about the pivot axis21.

Further, although the tubular handling apparatus100is described as having a lay tower2, this may also or alternatively be a recovery tower2.

Referring now toFIG. 15, there is shown a tubular installation apparatus, tubular recovery apparatus or tubular handling apparatus1,100in a collapsed position.

In the collapsed position, the telescopic member51is fully retracted, the loading shuttle6is locked in place to prevent movement during lifting and all other movable components are locked or secured to prevent inadvertent movement during lifting. A pair of lifting lines182from an external lifting apparatus (not shown) are connected to the apparatus1,100at spaced lifting points (not shown).

In the collapsed position, the apparatus1,100forms a transportable, modular structure than can be loaded to and/or unloaded from a vessel (not shown).

It will also be appreciated by those skilled in the art that any number of combinations of the aforementioned features and/or those shown in the appended drawings provide clear advantages over the prior art and are therefore within the scope of the invention described herein.