OA20835A - Inspection and/or maintenance method and associated apparatus - Google Patents

Abstract

A method of isolating a sea chest of a marine vessel. The method comprises sealing an inlet to the sea chest with an isolation apparatus. The isolation apparatus is both transported through a body of water adjacent the vessel and positioned to cover the inlet using a diverless operation.

Description

INSPECTION AND/OR MAINTENANCE METHOD AND ASSOCIATED APPARATUS

TECHNICAL FIELD

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

BACKGROUND

Marine vessels, such as ships, floating platfonns and the like, often hâve 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 (FOls) include oil drilling platforms and similar structures which are intended for permanent or semipennanent deployment at a ftxed location in the sea. Like ships, FOls and other wholly or partially submersible structures are critically dépendent for saie operation on the pressure integrity of their bull or outer shell. However, both ships and FOls typically hâve many fluid pénétrations 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 pénétrations 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 vulnérable to a range of failure conditions including corrosion, érosion 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 région 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 P5O-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, ex amples, embodiments, or daims of the présent disclosure to at least mitigate or ameliorate one or more problems associated with the prior art.

SUMMARY

According to an aspect of the invention, therc 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 sealîng 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 inwater 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 posîtioning the isolation apparatus over the inlet. The method may comprise posîtioning 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 posîtioning ofthe 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: sealîng 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 posîtioned to cover the inlet using a diverless operation.

Transport ing 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, crâne, winch or deck of the vessel. Altematively, 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 partial! y under gravity. For ex amp le, the isolation apparatus may comprise a négative buoyancy. The isolation apparatus may be suffi ci en tly 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 suspendîng 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 progressive! y paying out a suffi ci ent 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 ex ample, 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. Addîtionally, or altematively, the method may comprise allowing a margin or play in the depth ofthe isolation apparatus, such as by not rîgidly 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 adjlisting or fme-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 hâve a smaller error margin than the approximate depth corresponding to that ofthe 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 wîthout an ROV and fine positioning with a ROV connected to the isolation apparatus.

The method may comprise connecting a Remotely Opérâted Vehîcle (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 Imetre; 2metres, 5metres, 10 métrés. 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.

Altematively, 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 b y 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 wîthout 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 caméras 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 providîng the isolation apparatus with a particular centre of gravîty. The method may comprise provîding 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 înlet, 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 hâve a buoyancy whereby the isolation apparatus is predisposed or biased to adopt at least a sîmilar 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 hâve a smaller error margin than the approximate angle of inclination corresponding to that of the inlet. The method may comprise provîding 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 selfalignment 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 b y 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 différent!al 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 intérim 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 intérim 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 intérim attachment means. The intérim attachment means may comprise a lesser attachment force than the final attachment means. The intérim 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 intérim attachment means may provide an additîonal attachment force to supplément the final attachment means. The intérim 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 locatecl 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 si de of the inlet. For example, the method may comprise at least parti ally drainîng 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 maîntaining a seabs 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, pausîng 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 inadéquate 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 fïrst sealing portion of the pair being located înside 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 fïrst 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 maîntaining 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 maîntaining the device from within the marine vessel. The method may comprise disconnecting the device whîlst 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 extemal 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 usîng a single ROV for ail 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 intérim released configuration of the isolation apparatus, such as with the isolation apparatus attached with the intérim attachment means, but not the final attachaient means. Detaching the isolation apparat us may comprise detaching or at least reducîng the attachaient means. Detaching the isolation apparatus may comprise removing or reducîng a pressure differential across the isolation apparatus. The method may comprise filling or re-filling the sea chest to increase pressure on an internai side of the mlet 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 fiuid 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 ai 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 altematively 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 ch ests. The method may comprise sequentially isolating the plurality of sea ch ests. The method may comprise isolating the plurality of sea chests with a single ROV. Altematively the method may comprise operatîng 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 retrievîng 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 altematively, the plurality of sea chests may be provided on a plurality of manne vcssels, such as a plurality of marine vcsscls 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 équivalent or at least substantially équivalent, 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 présent invention that the method has one or more of: enhanced safety; and/or reduced cost in préparation 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 (Le. valves and associated apparatus) within the bull, which may terminale 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 waming of the extent of internai corrosion or other mechanical damage which could be expected to lead to failure in the months or years following the test. For example, FOls 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 vulnérable régions within the flooded cavities may be strongly preferred. Such visual inspection may be enabled by the presentlydisclosed 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 métré diameter or even more) and so removal of valve gear and sections of pipework is often impractîcal, particularly since access to the dry side of the walls of the tlooded cavities is very restricted in the confmed spaces of the hull or shell of a ship or FOL Despi te the large size of much of the pipework, it may be extremely diffîcult to access by remotel y operated vehicles (ROVs), not least because a failed or trapped ROV woukl become an obstruction. ROVs are not conventionally used for anything that pénétrâtes 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 dîsclosed 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 ex ample, the method may comprise provicling the second seal between the isolation apparatus and the coaming of the inlet.

The sealing portion/s of the isolation apparatus may be résilient. In ai least some examples, one or more sealing portion/s of the isolation apparatus are déformable 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 déformable so as to accommodate a range of înlets. For example, the first and/or second sealing portion/s may be sufficiently déformable to accommodate a variation in heîghts of coamming or projection/s adjacent a grating or grille of an intake. The portion/s may be elastically déformable. 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 fl nid path for water from the body of water to pass into the sea ch est, 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 ch est 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. Altematively, the aperture may be configured for single operation, such as for selectively opening from an initially closcd 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 si de 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 extemal 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, predefmed 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 négative buoyancy. For example, the isolation apparatus may comprise a négative 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 attachaient to the marine vessel, such as to a métal inlet, coaming, grating or the like.

The isolation apparatus may comprise a suspension point attachaient member, such as a fastener or the like for attachaient to an elongate member for suspension of the isolation apparatus. Accordingly, the isolation apparatus may be suspended via an elongate member.

Accord in g to a further aspect, there is provided a system comprising a pl Lirai ity 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 control 1er, 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-transi tory.

Any controller or controilers 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 unît or electronic controller or alternatively different functions of the controller may be embodied in, or hosted în, different control units or controilers. As used herein the terrn “controller” or “control unit” will be understood to include both a single control unit or controller and a plurality of control units or controilers 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 controilers 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 mtended that the varions aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the daims and/or in the following description and drawings, and in particular the mdividual features thereof, may be taken independently or in any combination. That is, ali embodiments and/or features of any embodîment 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 dépend 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 varions 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 optionai 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). Optionai 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 fonctions are also within the présent disclosure.

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

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

Ît may be an aim of certain embodiments of the présent disclosure to solve, mitigate or obviate, at least parti y, at least one of the problems and/or disadvantages associât ed with the prior art. Certain embodiments may aim to provide at least one of the advantages described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

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

Figure 1 shows a schematic diagram of a method accordîng 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 ofthe isolation apparatus of Figure 3;

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

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

Figure 7 shows a depiction ofthe isolation apparatus ofFigure 5 attached to an inlet.

DETAILED DESCRIPTION

Referring first to Figure l, there is shown a general method 2 of isolating a sea chest according to the présent disclosure. The method comprises transporting 4 an isolation apparatus through water. The method then comprises posîtioning 6 the isolation apparatus to cover an inlet. Optionally, the method comprises cleaning 8 the inlet prior to posîtioning 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 expensîve and dîfficult to carry out in bad weather. Accordingly, the présent 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 hydrostatîc 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 sealîng 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 connccts with the specialised blankîng plate and positions it over the sea chest inlet grids and within coaming thus forming a double seal.

4. The blankîng plate is held in position by magnets located on the blankîng plate cffccting double seal.

5. The process is repeated, if the sea chest has multiple inlet grids, until ail 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 replaccd creating hydrostatic pressure differential to hold the blanking plate(s) in position.

7. The sea chest inlet seal is confïrmed by noting no further draining required, after which the détective valve is removed for remédiai 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 opérâtes 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 huit 14 of the marine vessel 10, generally flush with the extemal 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 defming 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

Ί 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 control led remotel y, such as from on board the marine vessel. The ROV can be contre lied using feedback from an onboard caméra, 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 confîgured for a round or cîrcular sea chest inlet, the isolation apparatus 120 havîng 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 ail 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, utilismg its slightly négative buoyancy. Once lowered to the approximaîe 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 finnly secured over the inlet 12 by reducing pressure within the sea chest, such as by draining the sea chest (e.g. with pumps internai 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 iimer inlet perimeter within the coaming 12. It will be appreciated that the résilient 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 heîght 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 internai valve with in the sea ch est 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, 1 34. Accordingly, the ROV 50 can reconnect to the isolation apparatus 20, 120, by re-inserting the hooks 48, 49 înto 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 ch ests. 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 ail of the isolation apparatuses need hâve such a bleed valve 26, 126. Where ambient fluid pressure has been restored to the sea chest, ail 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 blankîng 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 présent 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 storihg a program or programs that, when executed, implement embodiments of the présent 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 machîne-readable storage storing such a program. Still further, embodiments of the présent 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.

Ail of the features disclosed in this spécification (including any accompanying daims, abstract and drawings), and/or ail ofthe steps ofany 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 présent 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 varions modifications may be made thereto without departing from the scope of the disclosure. For ex ample, it will be apprecîated that although shown here with generally square or circulât 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 spécification (including any accompanying daims, abstract and drawings), may be replaced by alternative features serving the same, équivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic sériés of équivalent or similar features.

The invention is not restricted to the details of any fbregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this spécification (including any accompanying daims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed. The daims should not be construed to cover merdy the foregoing embodiments, but also any embodiments which fall within the scope of the daims.

Claims (25)

1. A method of isolating a sea chest of a marine vessel, the method comprising: transporting an isolation apparatus through a body of water adjacent the vessel; positioning the isolation apparatus to cover an inlet to the sea chest;

sealing the inlet to the sea chest with the isolation apparatus, wherein the isolation apparatus is both transported through the body of water and positioned to cover the inlet using a diverless operation.

2. The method of claim 1, wherein the transporting the isolation apparatus through the body of water comprises lowering the isolation apparatus by suspension from an elongate member to a depth corresponding to the inlet.

3. The method of claim 1 or 2, wherein the method comprises positioning the isolation apparatus to cover the inlet using a ROV.

4. The method of claim 3, wherein the method comprises connecting the ROV to the isolation apparatus after the isolation apparatus has been transported through the body of water.

5. The method of any preceding claim, wherein the method comprises forming a double seal at the inlet with the isolation apparatus.

6. The method of claim 5, wherein the method comprises forming the double seal with a pair of concentrically arranged sealing portions of the isolation apparatus.

7. The method of claim 6, wherein the method comprises forming a seal against a coaming associated with the inlet using an outer sealing portion of the pair of sealing portions.

8. The method of any preceding claim, wherein the method comprises generally orienting the isolating apparatus by providing the isolating apparatus with a balanced buoyancy to generally orient the isolating apparatus at an inclination generally simîlar to that of the inlet.

9. The method of any preceding claim, wherein the method comprises at least initially attaching the isolation apparatus to the inlet using an intérim attachment means.

10. The method of any preceding claim, wherein the method comprises attaching the isolation apparatus to the inlet by creating a pressure dîfferential across the isolation apparatus.

11. The method of claim 10, wherein the pressure dîfferential is created across the isolation apparatus by draining the sea chest.

12. The method of either of daims 10 or 11, comprising detaching the isolation apparatus from the inlet, detacliment from the inlet comprising removing the pressure dîfferential across the isolation apparatus.

13, The method of claim 12, comprising activating a bleed valve in the isolation apparatus to balance the pressure across the isolation apparatus.

14. The method of any preceding claim, comprising detaching an ROV from the isolation apparatus whilst the isolation apparatus is in position to cover the inlet.

15. The method of any preceding claim comprising deploying a plurality of isolation apparatuses to isolate a plurality of sea chest inlets simultaneously.

16. The method of claim 15, comprising isolating the plurality of inlets with a single ROV.

17. An isolation apparatus for isolating a sea chest of a marine vessel, the isolation apparatus comprising a blanking plate and being configured for the method of any preceding claim.

18. The isolation apparatus of claim 17, wherein the apparatus is configured to be lowered by suspension from an elongate member to a depth corresponding to an inlet of the sea chest; and configured to be connected to a ROV when at the depth corresponding to the inlet.

19. The isolation apparatus of claim 17 or 18, wherein the apparatus comprises at least a pair of sealing portions for sealingly engaging the inlet to provide a double seal.

20. The isolation apparatus of claim 19, wherein the pair of sealing portions are radially arranged on a first sîde of the blanking plate, with a first sealing portion of the pair being located inside a second sealing portion, each of tire sealing portions being configured to ex tend around a perimeter of the inlet.

21. The isolation apparatus of claim 20, wherein first sealing portion is configured to Seal against a perimeter of a grating, grille or the like of the inlet; and the second sealing portion is configured to seal against a coaming, projection, rim or the like.

22. The isolation apparatus ofany of daims 1 7 to 21, wherein the isolation apparatus comprises a bleed valve to sclectivdy provide a fl nid path for water from the body of water to pass into the sea chest.

23. The isolation apparatus of any of daims 17 to 22, wherein the isolation apparatus is configured to be at least partially self-orienting, the isolation apparatus comprising a particular, predefmed centre of gravity so as to provide the isolation apparatus with a desired orientation.

24, The isolation apparatus of any of daims 17 to 23, wherein the isolation apparatus comprises one or more magnets for attachaient to the marine vessel.

25. A system comprising a plurality of the apparatus of any of daims 17 to 24.