TECHNICAL FIELD

The present invention relates to a method of inspecting and/or maintaining a marine vessel, particularly, but not exclusively, isolating a sea chest thereof; and associated apparatus.

BACKGROUND

Marine vessels, such as ships, floating platforms and the like, often have water intakes, which may be for cooling, such as engine cooling, or for other processes on the vessel or associated with the vessel.

Floating offshore installations (FOIs) include oil drilling platforms and similar structures which are intended for permanent or semipermanent deployment at a fixed location in the sea. Like ships, FOIs and other wholly or partially submersible structures are critically dependent for safe operation on the pressure integrity of their hull or outer shell. However, both ships and FOIs typically have many fluid penetrations of the hull below the waterline for intakes through which large volumes of water can flow for engine cooling, ballasting, and other purposes via large diameter pipes and valve gear (i.e. valves and associated apparatus) within the hull. In ships, these pipes normally terminate in compartments known as seachests which form recesses in the hull with inlets thereto protected by gratings installed flush with the hull surface.

The interior surfaces of the seachests, other hull fluid penetrations and their connected pipework and valve gear where fitted define flooded cavities in fluid communication with the sea, so their interior (wetted) surfaces are protected where possible by specialised surface coatings to combat corrosion. Nevertheless, the walls of the pipework, seachests and other parts of these flooded cavities remain vulnerable to a range of failure conditions including corrosion, erosion or obstruction by particulates, mechanical failure of stressed or moving parts, and colonisation by marine organisms which can completely block pipework if allowed to proliferate.

Provided the region to be inspected is close to the exterior surface of the hull, visual inspection may be carried out by means of a diver. Means may be provided whereby a diver may more easily manipulate heavy gratings or other closures from outside the vessel, as taught for example by J P50-155795U and JP50-155796U. The diver may then enter the seachest and visually inspect or photograph any valve gear which is visible through the suction and discharge openings.

It may be an object of one or more aspects, examples, embodiments, or claims of the present disclosure to at least mitigate or ameliorate one or more problems associated with the prior art.

SUMMARY

According to an aspect of the invention, there is provided an isolation method. The method may comprise a method of isolating an inlet. The inlet may be to a cavity, chamber, or compartment of a vessel. The inlet may be to a sea chest. The inlet may be in or through the hull of the vessel. The vessel may comprise a marine vessel, such as one or more of: a ship, FOI; wholly or partially submersible structure; Floating Production, Storage and Offloading unit (FPSO); Mobile Offshore Drilling Unit; or Accommodation Vessel.

The method may comprise sealing the inlet with an isolation apparatus. The method may comprise transporting the isolation apparatus through a body of water, such as adjacent the vessel, typically in which the vessel floats and/or is submerged. The method may comprise an in-water method. For example, the method may comprise a wet isolation method, whereby the vessel remains in-situ or at sea (e.g. not dry- docked). The method may comprise positioning the isolation apparatus over the inlet. The method may comprise positioning the isolation apparatus to cover the inlet. The method may comprise covering the inlet with the isolation apparatus to seal the inlet.

The method may comprise a diverless method. The method may be performed without a presence of a diver. The method may be entirely performed without any requirement for a diver. The transportation of the isolation apparatus through the body of water may be performed without a diver. The positioning of the isolation apparatus over the inlet may be performed without a diver. The method may comprise an unmanned method. The method may comprise a remotely-controlled method. The method may comprise control from a remote location, such as from on-board the vessel or from a second vessel (e.g. a maintenance boat or the like) adjacent the vessel with the inlet to be isolated. In at least one example, the method may comprise a method of isolating a sea chest of a marine vessel, the method comprising: sealing an inlet to the sea chest with an isolation apparatus; wherein the isolation apparatus is both transported through a body of water adjacent the vessel and positioned to cover the inlet using a diverless operation.

Transporting the isolation apparatus through the body of water may comprise lowering the isolation apparatus, such as from at or near surface. For example, the isolation apparatus may be lowered from a topside of the vessel, such as from a rigging, derrick, crane, winch or deck of the vessel. Alternatively, the isolation apparatus may be lowered from another vessel, such as a boat or the like adjacent the vessel with the inlet to be isolated.

The isolation apparatus may be lowered at least partially under gravity. For example, the isolation apparatus may comprise a negative buoyancy. The isolation apparatus may be sufficiently negatively buoyant so as to maintain a tension in an elongate member. The elongate member may comprise one or more of wire/s, rope/s, cable/s or the like. The method may comprise suspending the isolation apparatus, such as suspending the isolation apparatus in the body of water with the elongate member at a depth corresponding to the intake. The method may comprise lowering the isolation apparatus using free suspension, with the isolation apparatus being propelled downwards under its own gravity, without requiring additional pulling or pushing force/s.

Transporting the isolation apparatus through the body of water may comprise raising the isolation apparatus. The method may comprise raising the isolation apparatus through the body of water, such as to surface, after completion of the isolation operation or completion of associated operation/s. The method may comprise pulling or reeling in the elongate member to at least partially raise the isolation apparatus, such as to raise to at or near the surface.

The method may comprise controlling a position, such as a depth, of the isolation apparatus in the body of water. The method may comprise controlling the position of the isolation apparatus by controlling the elongate member, such as by monitoring and controlling a payout length of the elongate member. The method may comprise progressively paying out a sufficient length of the elongate member such as to allow the isolation apparatus to descend to a depth corresponding approximately to a depth of the inlet. For example, the method may comprise controlling a winch or the like so as to progressively lower the isolation apparatus to a depth approximately corresponding to a depth of the inlet. The method may comprise controlling a payout length to be slightly longer than that required to position the isolation apparatus at the depth corresponding to the inlet. The method may comprise maintaining the depth of the isolation apparatus. The method may comprise maintaining the depth of the isolation apparatus by controlling the payout length of the elongate member. The method may comprise arresting payout of the elongate member so as to maintain the depth of the isolation apparatus. Additionally, or alternatively, the method may comprise allowing a margin or play in the depth of the isolation apparatus, such as by not rigidly fixing the elongate member when the isolation apparatus reaches the depth corresponding approximately to the inlet. The method may comprise providing an excess of elongate member payout length.

The method may comprise adjusting or fine-tuning the depth of the isolation apparatus to correspond to that exactly suitable for isolating the inlet. The method may comprise using the ROV to position the isolation apparatus at an exact correct depth. The exact correct depth may have a smaller error margin than the approximate depth

corresponding to that of the inlet. The method may comprise providing the isolation apparatus and/or the ROV and/or the connection therebetween with a scope for adapting the depth of the isolation apparatus to match that of the inlet. For example, the method may comprise providing the connected ROV and isolation apparatus with an ability for at least some self-alignment with the inlet.

The method may comprise transporting and positioning the isolation apparatus using a combination of general lowering under suspension without an ROV and fine positioning with a ROV connected to the isolation apparatus.

The method may comprise connecting a Remotely Operated Vehicle (ROV) to the isolation apparatus. Connecting the ROV to the isolation apparatus may comprise attaching the ROV to the isolation apparatus. The method may comprise attaching the ROV to the isolation apparatus by one or more of: an inter-engaging coupling means; gripping; magnetic coupling means; a fastener/s. The method may comprise connecting the ROV to the isolation apparatus whilst both are in the water. The method may comprise connecting the ROV to the isolation apparatus when the isolation apparatus and ROV are both at a depth of at least: respectively 1 metre; 2metres, 5metres, 10 metres. The method may comprise connecting the ROV to the isolation apparatus after the isolation apparatus has been lowered to the approximate depth of the inlet. Alternatively, the method may comprise connecting the ROV to the isolation apparatus at or near the surface of the body of water.

The method may comprise connecting the ROV to the isolation apparatus by manoeuvring the ROV, such as by manoeuvring the ROV apparatus such that an engagement member of the ROV apparatus engages a corresponding engagement member of the isolation apparatus. The method may comprise only mechanically connecting the ROV to the isolation apparatus, such as without electrical or optical connections or the like. The engagement member/s may be configured to allow manipulation of the isolation apparatus by the ROV, once connected.

The method may comprise controlling the ROV based upon visual feedback, such as from one or more cameras of the ROV. In at least some examples, the method may comprise controlling the ROV with at least some autonomy, such as where the ROV performs at least portions of one or more manoeuvres or operations autonomously.

The method may comprise utilising the ROV to manoeuvre the isolation apparatus via the ROV’s connection to the isolation apparatus. The method may comprise remotely controlling the ROV to remotely control the isolation apparatus.

The method may comprise controlling an orientation of the isolation apparatus. The method may comprise controlling a general orientation of the isolation apparatus. The method may comprise controlling the general orientation of the isolation apparatus by providing the isolation apparatus with a particular centre of gravity. The method may comprise providing the isolation apparatus with a balanced buoyancy corresponding to a desired orientation of the isolation apparatus.

In at least some examples, the desired orientation of the isolation apparatus may be generally vertical, such that the isolation apparatus is generally oriented for covering a generally vertical inlet, such as in a wall of a generally vertical hull. According to at least some example methods, the buoyancy of the isolation apparatus may be adjusted and/or predefined so as to correspond to the desired orientation. For example, where the inlet to be isolated is at an angle of inclination to the vertical, the isolation apparatus may be configured to have a buoyancy whereby the isolation apparatus is predisposed or biased to adopt at least a similar approximate angle of inclination to the vertical.

The method may comprise adjusting or fine-tuning the orientation of the isolation apparatus to correspond to that exactly suitable for isolating the inlet. The method may comprise using the ROV to position the isolation apparatus at an exact correct orientation. The exact correct orientation may have a smaller error margin than the approximate angle of inclination corresponding to that of the inlet. The method may comprise providing the isolation apparatus and/or the ROV and/or the connection therebetween with a scope for adapting the orientation of the isolation apparatus to match that of the inlet. For example, the method may comprise providing the connected ROV and isolation apparatus with an ability for at least some self-alignment with the inlet.

The method may comprise blocking the inlet. The method may comprise blocking the inlet by the sealingly covering inlet with the isolation apparatus. The method may comprise blocking the inlet by positioning the isolation apparatus over the inlet. The method may comprise positioning a blocking member of the isolation apparatus over the inlet by remotely controlling the isolation apparatus’ position with the ROV. The method may comprise pressing the isolation apparatus against the inlet. For example, the method may comprise propelling the isolation apparatus against the inlet using the ROV. The method may comprise attaching the isolation apparatus to the vessel. The method may comprise utilising one or more attachment means of the isolation apparatus to attach the isolation apparatus. The attachment means may comprise one or more of: magnet/s; fluid pressure; underpressure; hydrostatic pressure; a pressure differential across the isolation apparatus. The method may comprise temporarily attaching the isolation apparatus to the vessel. The method may comprise attaching the isolation apparatus to the vessel with a final attachment. Optionally, the method may comprise attaching the isolation apparatus to the vessel with an interim

attachment, prior to the final attachment. The method may comprise temporarily attaching the isolation apparatus to the vessel in a process involving at least two steps: the first step comprising the interim attachment; and the second step comprising the final attachment. The final attachment may be for performing operations, such as with the inlet sealingly blocked. At least the first step may be performed using the interim attachment means. The interim attachment means may comprise a lesser attachment force than the final attachment means. The interim and/or final attachment means may comprise a magnetic attraction force, such as provided between one or more magnetic member/s of the isolation apparatus and a portion of the vessel, such as a portion of one or more of: the hull; the inlet; a coaming; an inlet grating. The interim attachment means may provide an additional attachment force to supplement the final attachment means. The interim and/or final attachment means may comprise a fluid pressure. In at least some examples, the final attachment means comprises a hydrostatic fluid pressure provided by the body of water acting on an exterior portion of the isolation apparatus, the exterior portion of the isolation apparatus being located on, or defined by, a portion/s of the isolation apparatus away from the sealing member of the isolation apparatus. The method may comprise reducing a pressure on an interior side of the inlet. For example, the method may comprise at least partially draining the sea chest inwards of the inlet. At least partially draining the sea chest may generate a relative underpressure in the sea chest, such that a hydrostatic pressure of the body of water exterior of the isolation apparatus biases the isolation apparatus against the inlet, thereby activating and/or maintaining a seal/s of the isolation apparatus. The method may comprise monitoring sealing during the draining of the sea chest, such as to monitor the integrity of the seal during draining. For example, the method may comprise at least partially draining, pausing or monitoring for a period of time to assess whether there is any ingress of water into the sea chest via the inlet/s. Such ingress may be indicative of inadequate sealing. Accordingly, the method may comprise re positioning the isolation apparatus, with the ROV, to adjust the seal/s.

The method may comprise providing a double seal of the inlet. The method may comprise providing a double seal with the isolation apparatus. The isolation apparatus may comprise at least a pair of sealing portions, the pair of sealing portions being radially arranged, that is to say a first sealing portion of the pair being located inside a second sealing portion. The sealing portion may extend around a perimeter of the isolation apparatus and/or the inlet. Each of the sealing portions may be configured to extend around a perimeter of the inlet. The method may comprise providing at least a pair of seals each extending around perimeter portions of the inlet. The method may comprise positioning the first sealing portion of the isolation apparatus against a corresponding portion of the inlet. The corresponding portion of the inlet may comprise a portion associated with a perimeter of a grating, grille or the like of the inlet. The method may comprise positioning the second sealing portion of the isolation apparatus against another corresponding portion of the inlet. The another corresponding portion of the inlet may comprise a coaming, projection, rim or the like. For example, the method may comprise providing the second seal between the isolation apparatus and the coaming of the inlet.

The method may comprise blocking the inlet to enable operations within the sea chest. The operations may comprise isolating the sea chest. The operations may comprise at least partially draining the sea chest. The operations may comprise draining the sea chest to below a level of an inlet or intake line, such as where a device may be inspected and/or replaced. The method may comprise inspecting and/or maintaining a device associated with the sea chest. The device may comprise a valve, such as associated with an intake from the sea chest. The method may comprise inspecting and/or maintaining the device from within the marine vessel. The method may comprise disconnecting the device whilst the sea chest is isolated by the isolation apparatus/es. The method may comprise removing or breaking an intake seal, such as of a valve device, associated with the sea chest. Removing or breaking the intake seal may be enabled in situ, with the marine vessel in water, by the seal, or double seal, provided by the isolation apparatus/es. Accordingly, the method may comprise providing access to portions of the sea chest from within the marine vessel, the isolation apparatus/es providing a barrier to ingress of water from the body of water during such access. The access may enable the inspection and/or maintenance of the sea chest and/or associated apparatus. In at least some examples, such maintenance comprises the replacement of the intake valve associated with the sea chest.

The method may comprise cleaning the inlet. The method may comprise cleaning the inlet with a diverless operation. The method may comprise cleaning the inlet with the ROV. The method may comprise cleaning the inlet with the ROV before the ROV is connected to the isolation apparatus. The method may comprise cleaning the inlet with one or more of: mechanical cleaning; cavitation blasting; jetting; brushing. The method may comprise cleaning an external portion of the inlet to enable the isolation apparatus to attach to the external portion of the inlet. The method may comprise cleaning the inlet before the isolation apparatus is attached to the inlet.

The method may comprise disconnecting the isolation apparatus from the ROV (or vice versa). The method may comprise disconnecting the isolation apparatus from the ROV after the isolation apparatus is attached to the inlet. The method may comprise disconnecting the isolation apparatus from the ROV after the isolation apparatus is preliminarily attached to the inlet. The method may comprise disconnecting the isolation apparatus from the ROV after the isolation apparatus is finally attached to the inlet.

The method may comprise deploying a plurality of isolation apparatuses.

The method may comprise positioning each of the plurality of isolation apparatuses with the ROV. The method may comprise positioning each of the plurality of isolation apparatuses with a same ROV, such as using a single ROV for all of the plurality of isolation apparatuses. The method may comprise sequentially positioning each of the plurality of isolation apparatuses. Alternatively, the method may comprise using a plurality of ROVs. Each of the plurality of isolation apparatuses may be lowered from surface on a respective elongate member.

The method may comprise reconnecting the ROV to the isolation apparatus (or vice versa).

The method may comprise detaching the isolation apparatus from the inlet. The method may comprise releasing at least the final attachment means. Detaching the isolation apparatus may comprise releasing the final attachment means to an interim released configuration of the isolation apparatus, such as with the isolation apparatus attached with the interim attachment means, but not the final attachment means.

Detaching the isolation apparatus may comprise detaching or at least reducing the attachment means. Detaching the isolation apparatus may comprise removing or reducing a pressure differential across the isolation apparatus. The method may comprise filling or re-filling the sea chest to increase pressure on an internal side of the inlet and isolation apparatus. The method may comprise providing a fluid path for water from the body of water to pass into the sea chest. The method may comprise providing the fluid path at or through the isolation apparatus. The method may comprise opening an aperture in the or an (e.g. another) isolation apparatus to provide at least one fluid path for water from the body of water through at least one inlet into the sea chest. The aperture may comprise a valve, such as a bleed valve. The method may comprise opening and/or further opening the aperture with the ROV. Additionally, or alternatively the method may comprise filling the sea chest from within the vessel, such as by using a discharge outlet into the sea chest to pump out fluid from the marine vessel. In at least some examples, the method may comprise opening the aperture with the ROV whilst the ROV is disconnected from the isolation apparatus. For example, the method may comprise sequentially: positioning the isolation apparatus with the ROV, attaching the isolation apparatus to the inlet, disconnecting the ROV from the isolation apparatus; performing operations with the isolation apparatus attached to the inlet; opening the aperture with the ROV; reconnecting the ROV to the isolation apparatus. The method may comprise opening the aperture with the ROV’s engagement member. In other examples, the method may comprise opening the aperture with the ROV whilst the ROV is connected to the isolation apparatus. The ROV may comprise an aperture engagement member in addition to the engagement member for connecting to the isolation apparatus.

The method may comprise isolating a plurality of sea chests. The method may comprise sequentially isolating the plurality of sea chests. The method may comprise isolating the plurality of sea chests with a single ROV. Alternatively the method may comprise operating a plurality of ROVs to isolate the plurality of sea chests. The method may comprise isolating the plurality of sea chests with a single isolation apparatus, such as sequentially isolating each of the sea chests after the previous sea chest has been isolated and then re-filled and the single isolation apparatus detached. Similarly, where one or more of the plurality of sea chests comprises multiple inlets to the sea chest, then the method may comprise isolating each of the sea chests with a single set of isolation apparatuses. Accordingly, the method may comprise sequentially or progressively isolating a plurality of sea chest inlets with a single isolation apparatus. The method may comprise isolating the plurality of sea chest inlets with the single isolation apparatus without retrieving the isolation apparatus entirely to surface between the respective isolations of the plurality of sea chest inlets. The plurality of sea chests may be provided on a single marine vessel. Additionally, or alternatively, the plurality of sea chests may be provided on a plurality of marine vessels, such as a plurality of marine vessels located or moored in close proximity to each other.

The method may comprise a remote inspection method. The method may comprise an unmanned inspection method. The method may comprise a diverless remote maintenance method. It may be an advantage of the present invention that the method is equivalent or at least substantially equivalent, such as in quality and/or scope, to the method that would be achieved with a diver. The method may comprise not removing or detaching or reconfiguring a device/s associated with the marine vessel. For example, the method may comprise isolating the sea chest without removing or detaching or reconfiguring the coaming and/or grille and/or grating associated with the inlet/s to the sea chest.

It may be an advantage of the present invention that the method has one or more of: enhanced safety; and/or reduced cost in preparation and/or inspection; and/or be a faster method which may increase system availability and/or require fewer personnel and/or reduce downtime; compared to conventional methods.

The method may comprise providing access and/or inspection via large diameter pipes and valve gear (i.e. valves and associated apparatus) within the hull, which may terminate in the sea chest/s. The functional status of any valve gear associated with the sea chest can be ascertained by closing selected ones of the valves and measuring the pressure drop across them. However, this gives only a momentary indication of the functional condition of the valve, and does not provide any warning of the extent of internal corrosion or other mechanical damage which could be expected to lead to failure in the months or years following the test. For example, FOIs are usually inspected at intervals of up to 3 years and so it is important that the inspection identifies incipient failure conditions that may lead to failure during the 3-year period following the test. For this reason, visual inspection of valves and other vulnerable regions within the flooded cavities may be strongly preferred. Such visual inspection may be enabled by the presently-disclosed methods, without requiring any diver/s.

The extent to which visual inspection is possible may be however limited by the extreme difficulty of access to the flooded cavities. Pipework can be very large (up to 1 metre diameter or even more) and so removal of valve gear and sections of pipework is often impractical, particularly since access to the dry side of the walls of the flooded cavities is very restricted in the confined spaces of the hull or shell of a ship or FOI. Despite the large size of much of the pipework, it may be extremely difficult to access by remotely operated vehicles (ROVs), not least because a failed or trapped ROV would become an obstruction. ROVs are not conventionally used for anything that penetrates hull cavities, such as sea chest intakes.

According to an aspect, there is provided an isolation apparatus. The isolation apparatus may be for performing the method of any aspect, example, claim or embodiment disclosed herein. The isolation apparatus may be configured to attach to a sea chest inlet.

The isolation apparatus may comprise an engagement member for engagement with or by a ROV engagement member. The isolation apparatus engagement member may be configured to allow gripping and/or manipulation of the isolation apparatus by the ROV.

The isolation apparatus may comprise a sealing portion for sealingly engaging the inlet. The isolation apparatus may comprise at least a pair of sealing portions for sealingly engaging the inlet. The pair of sealing portions may be radially arranged, that is to say a first sealing portion of the pair being located inside a second sealing portion. The sealing portion may extend around a perimeter of the isolation apparatus. Each of the sealing portions may be configured to extend around a perimeter of the inlet. The first sealing portion of the isolation apparatus may be configured to seal against a corresponding first portion of the inlet. The first corresponding portion of the inlet may comprise a portion associated with a perimeter of a grating, grille or the like of the inlet. The second sealing portion of the isolation apparatus may be configured to seal against a second corresponding portion of the inlet. The second corresponding portion of the inlet may comprise a coaming, projection, rim or the like. For example, the method may comprise providing the second seal between the isolation apparatus and the coaming of the inlet.

The sealing portion/s of the isolation apparatus may be resilient. In at least some examples, one or more sealing portion/s of the isolation apparatus are deformable to adapt to the corresponding portion/s of the inlet against which the isolation apparatus is to seal. The sealing portion/s may be sufficiently deformable so as to accommodate a range of inlets. For example, the first and/or second sealing portion/s may be sufficiently deformable to accommodate a variation in heights of coamming or projection/s adjacent a grating or grille of an intake. The portion/s may be elastically deformable. In at least some examples one or more of the sealing portion/s comprises a neoprene® or the like.

The isolation apparatus may be configured to selectively provide a fluid path for water from the body of water to pass into the sea chest. The isolation apparatus may comprise the fluid path at or through the isolation apparatus, such as via an aperture in the isolation apparatus. The isolation apparatus may be configured to provide at least one fluid path for water from the body of water through at least one sea chest inlet into the sea chest. The aperture may be selectively openable and/or selectively closable. The aperture may be configured to be cycled between open and closed configurations. Alternatively, the aperture may be configured for single operation, such as for selectively opening from an initially closed configuration. The aperture may be then reconfigured, such as at surface, following completion of the inspection and/or maintenance method, or between deployments of a plurality of isolation apparatuses. The aperture may comprise a valve, such as a bleed valve. The aperture may be configured to be opened and/or further opened with the ROV. The aperture may be configured to be closed with the ROV.

The isolation apparatus may comprise a blanking plate. The blanking plate may comprise the two sealing portions on a single side of the blanking plate, the single side being for engagement with the intake. An opposite side of the blanking plate may comprise the engagement member/s for connection to the ROV. The opposite side of the blanking plate may comprise an external side, away from the sea chest inlet in use. The opposite side of the blanking plate may comprise access for opening and/or closing the aperture. For example, the opposite side of the blanking plate may comprise an actuator for engagement and operation by an ROV.

The isolation apparatus may be configured to be at least partially self-orienting. The isolation apparatus may comprise a particular, predefined centre of gravity so as to provide the isolation apparatus with a desired orientation. The isolation apparatus may comprise a balanced buoyancy corresponding to the desired orientation of the isolation apparatus. The isolation apparatus may comprise a negative buoyancy. For example, the isolation apparatus may comprise a negative buoyancy so as to allow the isolation apparatus to be lowered through the body of water under gravity.

The isolation apparatus may comprise attachment means, such as one or more magnets for attachment to the marine vessel, such as to a metal inlet, coaming, grating or the like.

The isolation apparatus may comprise a suspension point attachment member, such as a fastener or the like for attachment to an elongate member for suspension of the isolation apparatus. Accordingly, the isolation apparatus may be suspended via an elongate member. According to a further aspect, there is provided a system comprising a plurality of the isolation apparatus of any other aspect, example, claim or embodiment. The system may be configured to sealingly block a plurality of sea chest inlets. The system may be configured to isolate a plurality of sea chests. The system may comprise a ROV. The system may comprise a lifting apparatus, such as a winch or the like. The system may comprise an elongate member.

According to an aspect, there is provided a system comprising a controller, the system arranged to perform a method according to any aspect, claim, embodiment or example of this disclosure.

According to an aspect, there is provided computer software which, when executed by a processing means, is arranged to perform a method according to any aspect, claim, embodiment or example of this disclosure. The computer software may be stored on a computer readable medium. The computer software may be tangibly stored on a computer readable medium. The computer readable medium may be non-transitory.

Any controller or controllers described herein may suitably comprise a control unit or computational device having one or more electronic processors. Thus, the system may comprise a single control unit or electronic controller or alternatively different functions of the controller may be embodied in, or hosted in, different control units or controllers. As used herein the term“controller” or“control unit” will be understood to include both a single control unit or controller and a plurality of control units or controllers collectively operating to provide any stated control functionality. To configure a controller, a suitable set of instructions may be provided which, when executed, cause said control unit or computational device to implement the control techniques specified herein. The set of instructions may suitably be embedded in said one or more electronic processors. Alternatively, the set of instructions may be provided as software saved on one or more memory associated with said controller to be executed on said

computational device. A first controller may be implemented in software run on one or more processors. One or more other controllers may be implemented in software run on one or more processors, optionally the same one or more processors as the first controller. Other suitable arrangements may also be used. 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. 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.

The invention includes one or more corresponding aspects, embodiments or features in isolation or in various combinations whether or not specifically stated (including claimed) in that combination or in isolation. For example, it will readily be appreciated that features recited as optional with respect to the first aspect may be additionally applicable with respect to the other aspects without the need to explicitly and unnecessarily list those various combinations and permutations here (e.g. the apparatus or device of one aspect may comprise features of any other aspect). Optional features as recited in respect of a method may be additionally applicable to an apparatus or device; and vice versa.

In addition, corresponding means for performing one or more of the discussed functions are also within the present disclosure.

The above summary is intended to be merely exemplary and non-limiting.

Various respective aspects and features of the present disclosure are defined in the appended claims.

It may be an aim of certain embodiments of the present disclosure to solve, mitigate or obviate, at least partly, at least one of the problems and/or disadvantages associated with the prior art. Certain embodiments may aim to provide at least one of the advantages described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment of the invention will now be described by way of example only and with reference to the accompanying drawings, in which:

Figure 1 shows a schematic diagram of a method according to a first example; Figure 2 shows a depiction of a sea chest inlet;

Figure 3 shows a schematic view of an example of an isolation apparatus;

Figure 4 shows a side view of the isolation apparatus of Figure 3;

Figure 5 shows a depiction of another example of an isolation apparatus;

Figure 6 shows a schematic view of the isolation apparatus of Figure 3 positioned adjacent a sea chest; and

Figure 7 shows a depiction of the isolation apparatus of Figure 5 attached to an inlet.

DETAILED DESCRIPTION

Referring first to Figure 1 , there is shown a general method 2 of isolating a sea chest according to the present disclosure. The method comprises transporting 4 an isolation apparatus through water. The method then comprises positioning 6 the isolation apparatus to cover an inlet. Optionally, the method comprises cleaning 8 the inlet prior to positioning 6 the isolation apparatus. As shown, the cleaning 8 may even occur prior to the transportation of the isolation apparatus 4 through the water.

In at least some examples, the method comprises inspection of a sea chest or devices associated with sea chests, such as intake valves or the like. Conventional sea chest inspections are however dangerous for divers and limited in scope, as well as being expensive and difficult to carry out in bad weather. Accordingly, the present disclosure here relates to diverless 9 methods. It is accordingly an object of at least some examples of this disclosure to repair or replace sea chest isolation valves without divers. Benefits can include: Enhanced Safety; Reduced Cost; Reduced POB;

Improved Budget Certainty (e.g. lower weather dependency).

At least some methods use an inspection / maintenance class ROV and topside rigging to insert a specialised blanking plate (Figures 3 and 4) onto a cleaned sea chest inlet grid (Figure 2) thus effecting a double seal. The sea chest is then drained which pulls the blanking plate tight onto the sea chest due to differential hydrostatic pressure. Once the double seal is established the valve can be removed / replaced / repaired and the blanking plate removed by the ROV once water is introduced to the sea chest using a bleed valve on the blanking plate where necessary.

In general, at least some examples here comprise the method of Figure 1 , including the following sequential steps: 1. Clean the sea chest inlet grid and surrounding sealing surfaces, including coamings, using ROV equipped with a cavitation blaster.

2. Lower the blanking plate over side of the vessel in the vicinity of sea chest inlets.

3. The ROV connects with the specialised blanking plate and positions it over the sea chest inlet grids and within coaming thus forming a double seal.

4. The blanking plate is held in position by magnets located on the blanking plate effecting double seal.

5. The process is repeated, if the sea chest has multiple inlet grids, until all the inlets to the sea chest are sealed.

6. The sea chest is drained to below the inlet line where the valve is to be replaced creating hydrostatic pressure differential to hold the blanking plate(s) in position.

7. The sea chest inlet seal is confirmed by noting no further draining required, after which the defective valve is removed for remedial action or replacement. A blind flange is located over the stub pipe while valve replacement work is being prepared and is removed just prior to the new / repaired valve being fitted and tested.

8. The sea chest is then refilled and the ROV operates the blanking plate bleed valve, if necessary, to facilitate sea water entry into the sea chest and thus balance the hydrostatic pressure for removal of blanking plate(s).

9. The blanking plate(s) is retrieved to the surface on the rigging lines.

Figure 2 shows an example of a portion of a marine vessel 10 comprising a sea chest inlet 12. The sea chest inlet 12 is located in the hull 14 of the marine vessel 10, generally flush with the external surface of the hull 14. The inlet 12 comprises a grating 16 to prevent passage of medium and large particles or objects into the sea chest.

Around a periphery of the inlet 12, there is a coaming 18 defining a raised protrusion projecting outwards from the surface of the hull 14 and inlet 12. It will be appreciated that the inlet 12 as shown here has been cleaned by cavitation blasting operated by an ROV (not shown in Figure 2).

Referring now to Figures 3 and 4, there is shown an isolation apparatus 20 in the form of a blanking plate. The blanking plate has the following features as shown in Figures 3 and 4: Double sealing faces 22, 24; Bleed valve 26 to facilitate removal; ROV attachment lugs 28, 30; Magnetic pads 32, 34 to secure temporarily in position while draining the sea chest; and Balanced buoyancy for correct orientation. As shown in Figure 3, the isolation apparatus can be connected to the ROV using the pairs of attachment lugs 28, 30 of the blanking plate with corresponding attachment members in the form of hooks 48, 49 of the ROV 50 (partially shown in Figure 3).

Eyelets 27, 29 for suspension from rigging line are also shown.

It will be appreciated that the isolation apparatus 20 can be manipulated by the ROV via the hooks 48, 49 to move and position the blanking plate over the sea chest inlet. Such manipulation can be controlled remotely, such as from on board the marine vessel. The ROV can be controlled using feedback from an onboard camera, such as indicated in Figure 5. It will be appreciated that the isolation apparatus 120 of Figure 5 is generally similar to that of Figures 3 and 4, except the blanking plate is configured for a round or circular sea chest inlet, the isolation apparatus 120 having a

correspondingly round or circular blanking plate. The isolation apparatus 120 of Figure 5 comprises similar features to the isolation apparatus 20 of Figures 3 and 4, incremented by 100. Accordingly, the isolation apparatus has ROV attachment lugs 128, 130. Description of not all such common features is omitted here for brevity and clarity.

Reference is now made to Figure 6, where the isolation apparatus 20 can be seen having been lowered on a rigging line 19. It will be appreciated that the isolation apparatus 20 has been lowered under gravity, utilising its slightly negative buoyancy. Once lowered to the approximate depth corresponding to the sea chest inlet 60, the isolation apparatus 20 is connected to the ROV 50 by moving the ROV 50 into engagement of the hooks 48, 49 with the attachment lugs 28, 30. Although shown in Figure 7 with the isolation apparatus 120 of Figure 5, it will be appreciated that in general, once connected to the ROV 50, the isolation apparatus 20, 120 is positioned within the coaming 18, over the inlet 12 to the sea chest. As shown in Figure 7, the ROV 50 can then be detached, with the magnetic pads 32, 34, 132, 134 of the isolation apparatus maintaining the blanking plate at least loosely in position over the inlet 12. The blanking plate can be firmly secured over the inlet 12 by reducing pressure within the sea chest, such as by draining the sea chest (e.g. with pumps internal to the marine vessel). Accordingly, the blanking plate is pushed tightly onto the inlet 12, with the hydrostatic pressure of the body of water (e.g. as visible in Figure 7) forcing the blanking plate seals 22, 24 against the respective coaming 18 and inner inlet perimeter within the coaming 12. It will be appreciated that the resilient deformity of the neoprene® seals 22, 24 allows the blanking plate to provide a double seal against a variety of geometries and arrangements of inlets 12, such as where different height coamings 18 are provided than that shown.

With the blanking plate so secured to sealingly block the inlet 12, operations can be performed within the sea chest. Upon completion of the operations, when it is desired to remove the isolation apparatus 20, 120, the internal valve within the sea chest can be closed (if the sea chest valve has been replaced) or re-closed (if the existing sea chest valve has merely been inspected and/or maintained). The ROV 50 can then activate the bleed valve 26, 126 to allow the sea chest to pressurise. With the removal of a pressure differential across the isolation apparatus 20, 120, the isolation apparatus is only loosely held against the inlet 12 by the magnetic pads 32, 34, 132, 134.

Accordingly, the ROV 50 can reconnect to the isolation apparatus 20, 120, by re inserting the hooks 48, 49 into the respective lugs 28, 30; 128, 130, and detach the isolation apparatus 20, 120 from the inlet 12.

It will be appreciated that selected ones of these processes can de replicated or duplicated as appropriate for additional inlets or additional sea chests. For example, where a sea chest has a pair of inlets, a pair of isolation apparatuses 20, 120 may be deployed over the pair of inlets. In such cases, it may be possible to remove both of the isolation apparatuses 20, 120 with the activation of only a single bleed valve 26, 126. Indeed, not all of the isolation apparatuses need have such a bleed valve 26, 126. Where ambient fluid pressure has been restored to the sea chest, all isolation apparatuses 26, 126 associated with that sea chest can be removed, such as by reconnection to the ROV 50. The ROV 50 may only need to overcome the attachment forces of the magnetic pads 32, 34, 132, 134 to detach the isolation apparatus/es 20, 120.

It will be appreciated that such processes can allow a single ROV 50 to operate multiple isolation apparatuses 20, 120, such that multiple inlets and even multiple sea chests can be isolated using a single ROV, without the ROV repeatedly being required to surface (e.g. to retrieve additional blanking plates).

It will be appreciated that at least some of these processes may be at least computer- assisted. It will be appreciated that embodiments of the present invention can be realised in the form of hardware, software or a combination of hardware and software. Any such software may be stored in the form of volatile or non-volatile storage such as, for example, a storage device like a ROM, whether erasable or rewritable or not, or in the form of memory such as, for example, RAM, memory chips, device or integrated circuits or on an optically or magnetically readable medium such as, for example, a CD, DVD, magnetic disk or magnetic tape. It will be appreciated that the storage devices and storage media are embodiments of machine-readable storage that are suitable for storing a program or programs that, when executed, implement embodiments of the present invention. Accordingly, embodiments provide a program comprising code for implementing a system or method as disclosed in any aspect, example, claim or embodiment of this disclosure, and a machine-readable storage storing such a program. Still further, embodiments of the present disclosure may be conveyed electronically via any medium such as a communication signal carried over a wired or wireless connection and embodiments suitably encompass the same.

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 such features and/or steps are mutually exclusive. The applicant indicates that aspects of the present disclosure may consist of any such individual feature or combination of features. It should be understood that the embodiments described herein are merely exemplary and that various modifications may be made thereto without departing from the scope of the disclosure. For example, it will be appreciated that although shown here with generally square or circular shapes, other shapes of inlets can also be isolated, such as by using a rectangular isolation apparatus to isolate a rectangular inlet.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed. The claims should not be construed to cover merely the foregoing

embodiments, but also any embodiments which fall within the scope of the claims.