Patent Description:
In this specification, a cofferdam means an enclosure with an open part configured to sealingly engage a submerged wall so as to define a cavity between the enclosure and the wall. Such cofferdams may be used for example to repair a damaged region on the hull of a ship without the need for dry docking.

In a typical procedure, a diver is sent down to weld threaded studs onto the hull plating and then to attach the cofferdam to the bolts. The stud bolts are removed by the diver on completion of the repair. In some cases the cofferdam is welded directly to the external hull plating by a diver. However, underwater welding can cause localised cracking of the hull due to the rapid cooling of the weld.

Once engaged against the submerged hull, water may be pumped or drained out of the cavity so that work can be done on the exposed hull. The pressure of the water on the outside of the cofferdam helps to maintain the cofferdam sealingly in position against the hull to exclude water from the dry cavity. However, if studs are not welded to the hull before placing the cofferdam, it can be difficult to position the cofferdam in the correct location and keep it there while it is connected to the hull, e.g. by pumping out the water so as to energise the seal. Documents <CIT>, <CIT>, <CIT> & <CIT> constitute relevant prior art.

The present invention provides in various aspects, an apparatus and a method for installing a cofferdam on a wet side of a submerged wall of a structure, and an installation including the structure and the apparatus, as defined in the claims.

The apparatus includes a connection body defining an aperture, which is sealingly fixed to the dry side of the submerged wall to surround an opening formed through the wall in fluid communication with the aperture. The apparatus further includes a flexible line, and a line puller which is mounted in an interior space of the structure and operated to retract the line through the opening and the aperture. A line puller pressure barrier is sealingly connected to the connection body to prevent water from flowing through the opening and the aperture into the interior space during operation of the line puller. The line is connected to the cofferdam to pull the cofferdam against the wet side of the wall when the line is retracted. After sealingly engaging the cofferdam against the wet side of the wall, water is removed from the temporary cavity defined between the cofferdam and the wall. Further in accordance with the method, a pressure barrier is sealing connected to the connection body to prevent water from flowing through the opening and the aperture into the interior space while forming the opening.

By carefully positioning the connection body, optionally two or more such connection bodies on the dry side of the wall, each in a position corresponding to the point of attachment of the respective line to the cofferdam, the cofferdam may easily be guided to the correct position and then urged against the hull to form a seal, working from inside the ship or other structure. Optionally, each line may be connected to an alignment pin which extends from the cofferdam and is received in the respective opening and aperture to further ensure that the cofferdam is located and retained in the desired position.

Further features and advantages will be appreciated from the illustrative embodiment of the invention which will now be described, purely by way of example and without limitation to the scope of the claims, and with reference to the accompanying drawings, in which:.

Reference numerals appearing in more than one of the figures indicate the same or corresponding parts in each of them.

Referring to <FIG>, the apparatus includes at least one connection body <NUM> defining an aperture <NUM>, and at least one line puller <NUM> which, as shown, may be formed as a winch assembly. The or each line puller is provided with a respective line puller pressure barrier <NUM>, which, as illustrated, may form a casing of the line puller or winch assembly. The apparatus further includes a cofferdam <NUM> and at least one flexible line <NUM>; each line connects the cofferdam to a respective line puller, as illustrated in <FIG>.

Preferably the apparatus further includes, for each connection body <NUM>, a respective valve <NUM> which is operable to selectively open and close a valve orifice <NUM>, e.g. by translating, rotating or otherwise moving a valve element <NUM> which is received in the valve body <NUM>. In the use position of the valve, the valve orifice <NUM> is sealingly connected in fluid communication with the opening <NUM> via the flowpath <NUM> of the connection body <NUM>. The valve may be configured as a gate valve, with the valve element configured as a sliding gate in the valve body. The valve <NUM> is connected sealingly to the connection body <NUM> and serves to connect the line puller, e.g. winch assembly <NUM> to the connection body <NUM>. The valve <NUM> may be sealingly and releasably connected to the connection body, e.g. via bolted flanges as shown, or by any other suitable fixing arrangement as known in the art.

As shown in <FIG>, the apparatus may be provided in the form of a kit of parts, optionally including various further components such as a penetrator tool <NUM> and/or a plug deployment tool <NUM>, which may be connected to the connection body <NUM>, preferably interchangeably, and preferably via the valve <NUM> - which is to say, the valve <NUM> is preferably interposed between the connection body <NUM> and the penetrator tool or plug deployment tool. A respective plug <NUM> and/or cap <NUM> may be sealingly engagable with each respective connection body <NUM> to exclude water from the connection body, which may thus form a permanent installation after completing the repair and removing the cofferdam. The plug and/or cap may be releasable so that the connection body can be used again with the rest of the apparatus for a future repair.

The connection body <NUM> defines a flowpath <NUM> which opens through apertures <NUM> and <NUM> at opposite, outer and inner ends of the connection body. By the outer end is meant that end of the connection body that is connected in use to the submerged wall <NUM> of the structure <NUM>.

The connection body <NUM> may be internally threaded <NUM>, e.g. at the inner end aperture <NUM> as shown, to receive an externally threaded plug <NUM>, and may include a generally cylindrical wall <NUM> that surrounds the flowpath <NUM>. A flange <NUM> may be formed at the inner end of the wall <NUM> for connecting components of the apparatus to the connection body <NUM>. Such components may include a cap <NUM> which is bolted to the flange; alternatively or additionally, the inner end of the wall <NUM> could be externally threaded to receive an internally threaded cap.

These and other features of the connection body and various optional components of the apparatus may be generally as taught in <CIT> to the present applicant.

Referring to <FIG>, the structure <NUM> may be a floating structure such as a ship which is supported in a body of water <NUM>, e.g. the sea. The submerged wall <NUM> may form the hull of the ship, and excludes the body of water <NUM> on the wet side <NUM> of the wall from the interior space <NUM> within the structure. The interior space <NUM> is bounded by a dry side <NUM> of the wall opposite its wet side <NUM>.

Referring to <FIG>, each connection body <NUM> is fixed sealingly to the dry side <NUM> of the wall <NUM> in the desired use position to form an installation. As shown in <FIG>, the installation may include two or more connection bodies <NUM> which are sealingly fixed in spaced relation to the dry side <NUM> of the wall <NUM> for use with two or more respective line pullers <NUM> as further explained below. The or each connection body <NUM> may be made from steel or other metal and may be permanently connected, e.g. welded to the wall <NUM>, which may be made from steel plate. Other means of connection may be employed, for example, brazing or mechanical fastening.

After fixing each connection body <NUM>, it may be tested for pressure tightness, for example, as described in <CIT>. A valve <NUM> may then be connected to the connection body <NUM> (<FIG>).

Referring to <FIG> and <FIG>, the penetrator tool <NUM> includes a cutter <NUM> mounted on a tool body <NUM> which is sealingly and releasably connected to the valve <NUM>, e.g. via a bolted flange as shown. The tool <NUM> is operable in the use position of the connection body to advance and retract the cutter <NUM> through the open valve orifice <NUM> and the flowpath <NUM> and aperture <NUM> of the connection body <NUM>.

The cutter <NUM> may be mounted on a driveshaft <NUM> that can be engaged by a drive tool <NUM> to drive the cutter in rotation. The driveshaft <NUM> may be rotatably mounted in an axially movable outer shaft <NUM> which is rotated by a handle <NUM> to advance the cutter <NUM> as it rotates.

After advancing the cutter <NUM> to engage the wall <NUM> the cutter <NUM> is operated (driven in rotation and progressively further advanced) within the connection body <NUM> to cut an opening <NUM> through the wall <NUM>, as shown in <FIG>. The detached coupon may be captured and retracted with the cutter.

The opening <NUM> is formed within the aperture <NUM> of the connection body so that it is surrounded by the connection body <NUM>. That is to say, the opening <NUM> is in fluid communication with the aperture <NUM> and flowpath <NUM> so that it opens into the connection body <NUM> at the aperture <NUM>, and forms a flowpath opening through, and extending between, the wet and dry sides of the wall <NUM>.

The flowpath <NUM> of the connection body is in fluid communication with the body of water <NUM> via the opening <NUM> and aperture <NUM>, while the connection body <NUM> by its sealing connection to the wall <NUM> retains the fluid pressure of the water within the flowpath <NUM>.

The penetrator tool <NUM> further includes a pressure barrier, which as shown may be formed by the tool body <NUM> which sealingly engages the shaft assembly <NUM>, <NUM>. The pressure barrier is sealing connected in use to the connection body <NUM>, preferably via the valve <NUM>, and is configured to prevent water from flowing from the body of water <NUM>, through the opening <NUM> and the aperture <NUM> into the interior space <NUM> during operation of the penetrator tool to form the opening <NUM>.

After forming the opening <NUM>, the cutter <NUM> is withdrawn on the shaft assembly <NUM>, <NUM> and then the valve <NUM> is closed to retain the fluid pressure of the body of water <NUM> before removing the penetrator tool <NUM> from the valve <NUM> (<FIG>).

In its use position, each connection body <NUM> thus surrounds a respective opening <NUM> formed through the wall <NUM> in fluid communication with the respective aperture <NUM>, so that by providing two or more connection bodies <NUM>, two or more line pullers <NUM> can be mounted in the interior space <NUM>.

Referring to <FIG>, the apparatus further includes a cofferdam <NUM> which is sealingly engagable in use against the wet side <NUM> of the submerged wall <NUM> to define, and exclude water from, a temporary cavity <NUM> between the cofferdam <NUM> and the wet side <NUM> of the wall.

The cofferdam <NUM> defines an enclosure with an open side <NUM> surrounded by a sealing surface <NUM> that engages the wall <NUM> in use. The sealing surface may comprise a resilient sealing material, e.g. rubber. The enclosure is configured to resist external fluid pressure when drained of water so that the dry cavity <NUM> provides a working space within which the wet side <NUM> of the wall is exposed so that damage to the wall <NUM> can be repaired. The cofferdam <NUM> may be supported buoyantly or via a cable <NUM> while it is pulled and/or lowered into position in the body of water <NUM> alongside the structure <NUM>. A hose <NUM> may be provided for extracting water from the cavity <NUM> or re-filling the cavity <NUM> with water after the work is finished.

In order to obtain a satisfactory seal on an uneven hull surface, the sealing surface <NUM> may be formed on an assembly of two bodies of resilient sealing material (e.g. elastomer, e.g. rubber or neoprene) of different hardnesses. It is found that a particularly effective seal may be obtained by arranging a relatively harder one of the bodies between the wall of the cofferdam and the softer one of the bodies, so that the softer one of the bodies forms the sealing surface <NUM> which engages the hull of the ship or other structure. The two bodies may be assembled together by adhesive.

One or more alignment pins <NUM> may extend from the cofferdam. A distal end of each alignment pin <NUM> is attached or attachable to a distal end of a respective flexible line <NUM>. This connection could be provided by a connector at the distal end of the alignment pin, which could be a solid pin; alternatively for example, if the alignment pin is tubular, then the connection to the distal end could be accomplished by passing the distal end (i.e. the distal end portion) of the line <NUM> through the tublar alignment pin and then connecting the line to the cofferdam inwardly of the pin <NUM>. Each pin <NUM> may be rigidly fixed to the cofferdam <NUM>. Where as shown more than one pin <NUM> is provided, the pins <NUM> may extend in parallel relation.

Each alignment pin <NUM> may extend outwardly away from the open side <NUM> of the cofferdam <NUM>, beyond a plane (which may be flat or curved, e.g. as shown) in which the sealing surface <NUM> lies. The plane is defined by the wet side <NUM> of the wall <NUM> in the use position of the cofferdam <NUM>; in use, each pin <NUM> may thus extend through a respective opening <NUM> and into the aperture <NUM> and flowpath <NUM> of the respective connection body <NUM> as shown in <FIG> and <FIG> and further described below.

Each alignment pin <NUM> may be connected to the cofferdam <NUM> within the cavity <NUM> so that it extends outwardly through the opening or open side <NUM> of the cofferdam. In this configuration, the flowpath <NUM> of each connection body <NUM> will communicate in use with the cavity <NUM>. Alternatively or additionally, one or more alignment pins <NUM> could be arranged around the cofferdam outside the cavity <NUM>, each to be received in a connection body <NUM> which remains in fluid communication with the body of water <NUM> outside the cavity <NUM> in the use position of the cofferdam.

Referring again to <FIG>, each line puller pressure barrier <NUM> is sealingly, and preferably releasably connected in use to a respective one of the connection bodies <NUM>, preferably via the respective valve <NUM>. Each line puller <NUM> is mounted in the interior space <NUM>, which may be accomplished by supporting the line puller <NUM> on the respective line puller pressure barrier <NUM> which in turn is mounted on the connection body <NUM>, preferably via the valve <NUM>.

The valve orifice <NUM> can then be opened so that the line <NUM> can be passed through the opening <NUM> and the aperture <NUM> and through the valve orifice <NUM> to connect the cofferdam <NUM> to the line puller <NUM>. The line puller <NUM> can then be operated to retract the line through the opening <NUM> and the aperture <NUM> via the valve orifice <NUM>.

The line puller pressure barrier retains (withstands) fluid pressure from the body of water <NUM> outside the structure to prevent water from flowing through the opening <NUM> and the aperture <NUM> into the interior space <NUM> during operation of the respective line puller <NUM>.

Thus, in use, each line <NUM> extends from the respective line puller <NUM> to the cofferdam <NUM>, through a respective opening <NUM>, through the flowpath <NUM> and apertures <NUM>, <NUM> of the respective one of the connection bodies <NUM>, and (where a valve <NUM> is provided) also through the open valve orifice <NUM>.

The distal end of the line <NUM> is connected to the cofferdam <NUM>, optionally at the distal end of the respective alignment pin <NUM> as shown. Where two or more line pullers are used, their respective lines <NUM> are connected at respective, spaced locations on the cofferdam <NUM> corresponding to the positions of the respective connection bodies <NUM> on the wall <NUM>. The connection bodies may be spaced apart vertically and/or horizontally so as to accurately locate the cofferdam <NUM> in its use position.

Each line puller <NUM> is operated in its use position to retract the respective line <NUM> through the respective opening <NUM> and the aperture <NUM> to pull the cofferdam towards and against the wet side <NUM> of the wall <NUM>, as shown in <FIG> and <FIG>. The pulling force of the lines <NUM> sealingly engages the cofferdam <NUM> against the wet side <NUM> of the wall <NUM> to define, and exclude water from, the temporary cavity <NUM> between the cofferdam <NUM> and the wet side <NUM> of the wall <NUM>.

Once the cofferdam is in its use position, the water can be removed from the temporary cavity <NUM> to leave it dry as shown in <FIG>. The water may be drained from the cavity <NUM> via a respective one of the connection bodies <NUM> (e.g. via valve <NUM>) or extracted through the hose <NUM>. In use, after the cofferdam has been drained of water, a limited volume of water (e.g. a few litres per hour) may continue to flow past the seal into the cofferdam, but may be drained away via the lowermost connection body (e.g. via valve <NUM>) to keep the cofferdam dry.

Once the cofferdam <NUM> is drained of water, the damaged region of the wall <NUM> (e.g. the ship's hull) can be cut out to provide an opening through which a worker can access the cavity <NUM> from inside the structure <NUM> to work on the wet side <NUM> of the wall <NUM>. The external cut edges formed during installation of the pressure ports can then be made good and the damaged area of the hull prepared for the repair. Finally, the repair plate can be inserted into the aperture and welded into place from inside the interior space <NUM> of the structure, e.g. inside the ship.

Alternatively the cavity <NUM> could be accessed from outside the structure <NUM>, e.g. via an external access passage, as known in the art.

Referring now to <FIG>, the line puller <NUM> may include a spool <NUM> on which the line <NUM> is stored when retracted. The spool <NUM> including the retracted line may be enclosed within the line puller pressure barrier <NUM>. Thus, the line puller <NUM> may be configured as shown as a winch assembly <NUM> wherein the spool <NUM> is configured as a winch drum and the line puller pressure barrier <NUM> forms the pressure tight, outer casing of the assembly. The outer casing may include a connection flange <NUM> to form a pressure tight, bolted connection to the valve <NUM> as shown.

The line puller pressure barrier <NUM> may include a transparent window <NUM> for observing the operation of the line puller <NUM>. In use, fluid pressure from the body of water <NUM> will cause a quantity of water <NUM> to flow through the opening <NUM>, connection body <NUM> and valve <NUM> into the outer casing after the valve <NUM> is opened, until the outer casing is full; thus, once the cofferdam <NUM> is in position, the window <NUM> may be used to check when the cavity <NUM> has been emptied of water.

As shown, the spool <NUM> may be configured to be driven in rotation mechanically from outside the line puller pressure barrier <NUM>, e.g. by a manual crank handle <NUM> via a driveshaft <NUM> and geartrain <NUM> as shown. The driveshaft <NUM> passes through a pressure seal <NUM> where it enters the outer casing.

The line puller <NUM> may include a guide mechanism <NUM> for guiding the line <NUM> in an axial direction of the spool <NUM> during rotation of the spool. The guide mechanism <NUM> may be operable mechanically from outside the line puller pressure barrier <NUM>, e.g. by a rotating shaft <NUM> which passes through a pressure seal <NUM> where it enters the casing. The shaft <NUM> may rotate a leadscrew <NUM> which in turn drives a captive guide block <NUM> axially along the spool. The line <NUM> passes through the guide block so that by moving the guide block as the spool rotates, the line <NUM> can be wound evenly onto the spool.

Referring also to <FIG> and <FIG>, the line puller <NUM> may include a float <NUM> and a float deployment mechanism, which may be configured as an axially displaceable rod <NUM>.

The float <NUM> is preferably arranged to fit within and move slidingly along inside the flowpath defined by the axially connected opening <NUM>, connection body <NUM>, valve orifice <NUM> and line puller pressure barrier <NUM>; the line puller pressure barrier may include a float cavity <NUM> within which the float <NUM> is received as shown in <FIG> before deployment.

The float <NUM> is attached to a distal end (i.e. distal end portion) of the line <NUM>. For this purpose the float <NUM> may be formed in two halves which are fixed together to enclose the line <NUM> in-between them before connecting the line puller <NUM> and the line puller pressure barrier <NUM> in their use position.

The float deployment mechanism is then operated, e.g. by pushing in the rod <NUM> as shown in <FIG>, to advance the float <NUM> and the distal end of the line <NUM> from the interior space <NUM>, through the opening <NUM> and the flowpath <NUM> and apertures <NUM>, <NUM> of the connection body <NUM>, and via the valve orifice <NUM> if provided, into the body of water <NUM> on the wet side <NUM> of the wall <NUM>.

In this position the float <NUM> may be captured and brought to the surface, e.g. by an underwater, remotely operated vehicle (ROV). Alternatively, the float <NUM> could be configured to draw the line buoyantly to the surface as the line <NUM> is payed out by operation of the line puller. To assist this process, the line <NUM> could include a lighter, lead line (i.e. leading line) which is connected to the distal end of the main line, which in turn will be connected to the cofferdam <NUM> after the float is recovered at the surface of the body of water <NUM> and the main line drawn up after the lead line.

The main line could be a steel cable or could be made from lighter fibres, in which case a lead line may not be required.

The line puller pressure barrier <NUM> is configured to prevent water from flowing through the opening <NUM> and the aperture <NUM>, via the connection body <NUM> into the interior space <NUM> during operation of the float deployment mechanism.

Referring to <FIG> and <FIG>, each line <NUM> is retracted to pull the alignment pin <NUM> into the corresponding opening <NUM> and the aperture <NUM>. In the use position of the cofferdam <NUM>, each alignment pin <NUM> is thus received in the respective opening <NUM> and the aperture <NUM>, within the flowpath <NUM> of the connection body <NUM>, to locate the cofferdam <NUM> on the wet side <NUM> of the wall <NUM>. The line puller <NUM>, e.g. spool or winch mechanism, may be locked to retain the alignment pin <NUM> while the cofferdam is in use.

The openings <NUM> provide predefined locations for the attachment points of the lines <NUM>, so that by arranging the connection bodies <NUM> in a pattern corresponding to the attachment points of the lines <NUM> to the cofferdam, the cofferdam <NUM> can be readily located on the wet side of the wall without diver assistance. The alignment pins <NUM> provide a firmer connection which further ensures the correct location of the cofferdam <NUM> and further resists forces, e.g. a net buoyancy force, that may be applied to the cofferdam in the plane of the wall <NUM>.

After completing the repair, the cofferdam may be released from the wet side <NUM> of the wall <NUM>, e.g. by unlocking the line puller <NUM> and paying out the line <NUM>. The float deployment mechanism may be adapted to be operable to urge the alignment pins <NUM> out of the openings <NUM>. The cofferdam <NUM> can the be recovered to surface, e.g. on the cable <NUM>, before detaching the line <NUM> from the cofferdam (<FIG>).

The line <NUM> is then removed from the opening <NUM>, the flowpath <NUM> and apertures <NUM>, <NUM> of the connection body, and the valve orifice <NUM>, optionally by retracting it fully into the line puller <NUM>. The valve <NUM> can then be operated to close the valve orifice <NUM> before removing the line puller pressure barrier <NUM> from the valve <NUM>. The flowpath <NUM> and apertures <NUM>, <NUM> of the connection body <NUM> can then be sealed with the plug <NUM>.

Referring to <FIG> and <FIG>, the plug deployment tool <NUM> includes a body <NUM> which is sealingly and releasably connected to the valve <NUM> before opening the valve orifice <NUM> and operating the tool to advance the plug <NUM> through the valve orifice <NUM> and to sealingly engage the plug <NUM> with the connection body <NUM>.

The plug deployment tool <NUM> may be generally as described in <CIT>, including an inner shaft <NUM> which is rotatably received in an outer shaft <NUM> having a plate <NUM> with studs <NUM> which are received in holes <NUM> in the plug. The inner shaft <NUM> is rotated by a knob <NUM> to engage a threaded stud <NUM> in a corresponding threaded hole <NUM> in the plug <NUM> to retain the plug <NUM> in engagement with the studs <NUM>. The shaft assembly <NUM>, <NUM> is pushed axially through the body <NUM> to engage the threaded plug <NUM> via the aperture <NUM> in the flowpath <NUM> of the connection body <NUM> before rotating the outer shaft <NUM> using its handle <NUM> to screw the plug <NUM> into the female thread <NUM> of the connection body <NUM>.

The plug deployment tool <NUM> includes a pressure barrier, which conveniently may be formed by the tool body <NUM> which sealingly retains the shaft assembly <NUM>, <NUM>. The pressure barrier is configured to prevent water from flowing through the opening <NUM> and the flowpath <NUM> and apertures <NUM>, <NUM> of the connection body <NUM>, into the interior space <NUM> during operation of the plug deployment tool <NUM>.

The plug <NUM> may include a sacrificial anode <NUM> which extends into the connection body <NUM> and/or opening <NUM> to protect the fixed assembly from corrosion. Although the anode <NUM> is relatively short as illustrated in <FIG>, it could extend through the opening <NUM> so that an end face of the anode <NUM> lies in or proximate the plane of the wet side <NUM> of the wall <NUM>, to provide protection to the cut surfaces of the wall <NUM> in the opening <NUM>. The plug <NUM> could be engaged in a thread at the outer end of the connection body <NUM> rather than its inner end as shown.

After sealing each connection body <NUM> with a respective plug <NUM>, the valve <NUM> may be removed. A respective cap <NUM> may then be fixed sealingly to each respective connection body <NUM> to cover the plug, e.g. by bolting the cap to the flange <NUM>, to provide a safe and compact installation as shown in <FIG>.

In summary, a cofferdam <NUM> is guided and installed against a submerged wall <NUM> of a structure <NUM> by one or more flexible lines <NUM>. Each line is retracted, via an opening <NUM> formed in the wall <NUM>, by a line puller <NUM> mounted inside an interior space <NUM> of the structure <NUM> to pull the cofferdam against the wall <NUM>. A connection body <NUM> is sealingly fixed to the dry side <NUM> of the wall <NUM> to enclose the opening <NUM>, and a pressure barrier <NUM> is sealingly connected to the connection body <NUM> to exclude water from the interior space <NUM> during operation of the line puller <NUM>. The line puller <NUM> may be configured as a winch assembly with a casing forming the pressure barrier <NUM>.

In alternative embodiments, instead of separate parts that are releasably connected together, two or more of the apparatus elements could be integrated together as a permanent assembly. For example, the connection body could be permanently associated with a valve body for receiving a moving valve element.

The line puller pressure barrier could be configured other than as a casing of the line puller; for example, it could form a fluid pressure seal through which the line moves slidingly in use.

The line puller, e.g. the spool, could be driven by a motor, e.g. an electric motor, rather than manually. The spool and guide mechanism could be geared together so that they are driven in rotation simultaneously by a common drive mechanism.

A smooth liner or guide could be provided to extend into the opening <NUM>, to line the whole opening or just the upper part of the opening <NUM>, so as to assist the line <NUM> to move through the opening without becoming caught on a sharp outer edge of the opening. The liner or guide could be advanced from the line puller <NUM> into the opening <NUM> and locked in that position, and then subsequently retracted again in a similar way to the rod <NUM>, perhaps after the lead line has been deployed from the spool. It could be arranged behind the float to function as the float deployment mechanism to push the float <NUM> out through the opening <NUM> instead of the rod <NUM>. The alignment pin <NUM> could be arranged to pass into the liner or guide or to displace it inwardly as the cofferdam moves into its use position.

Although it is preferred to provide a valve <NUM> to retain fluid pressure while removing or attaching the different components of the apparatus, it is conceivable that the apparatus could be provided as a permanent assembly, or that the opening <NUM> could be temporarily closed in another way, e.g. by means of a plug inserted from the wet side <NUM> of the wall <NUM>.

Many further adaptations are possible within the scope of the claims.

Claim 1:
An apparatus for installing a cofferdam (<NUM>) on a wet side (<NUM>) of a submerged wall (<NUM>) that excludes a body of water (<NUM>) from an interior space (<NUM>) of a structure (<NUM>), the interior space (<NUM>) being bounded by a dry side (<NUM>) of the wall (<NUM>) opposite the wet side (<NUM>); the apparatus including:
a cofferdam (<NUM>), the cofferdam being sealingly engagable in use against the wet side (<NUM>) of the wall (<NUM>) to define, and exclude water from, a temporary cavity (<NUM>) between the cofferdam (<NUM>) and the wet side (<NUM>) of the wall (<NUM>);
characterised in that the apparatus further comprises a connection body (<NUM>) defining an aperture (<NUM>),
the connection body (<NUM>) being sealingly fixable to the dry side (<NUM>) of the wall (<NUM>) in a use position, to surround an opening (<NUM>) formed through the wall (<NUM>) in fluid communication with the aperture (<NUM>);
a flexible line (<NUM>);
a line puller (<NUM>) operable, when mounted in use in the interior space (<NUM>), to retract the line (<NUM>) through the opening (<NUM>) and the aperture (<NUM>) in the use position of the connection body (<NUM>); and
a line puller pressure barrier (<NUM>), the line puller pressure barrier (<NUM>) being sealingly connected in use to the connection body (<NUM>) to prevent water from flowing through the opening (<NUM>) and the aperture (<NUM>) into the interior space (<NUM>) during operation of the line puller (<NUM>);
the line (<NUM>) being connected in use to the cofferdam (<NUM>) to pull the cofferdam against the wet side (<NUM>) of the wall (<NUM>) when the line (<NUM>) is retracted.