PROVIDED IN A MARINE VESSEL OR INSTALLING SAID POD HOUSING IN SAID SEATING

TECHNICAL FIELD

The present invention relates to a method of dismounting a pod housing, which has a lower body suspended from a marine vessel by an intermediate portion, preferably in the form of a stay serving as a rudder, from a seating provided in a marine vessel, or installing said pod housing in said seating, the pod housing and the seating forming a pod unit.

BACKGROUND ART

A pod unit including a pod housing and a seating for the pod housing is a large and heavy unit, often in the range 200-400 tons. An exemplary pod is disclosed in US

6,783,409 B2 and US 6,935,907 B2, both of which are included herein by reference.

The pod housing comprises a lower body for the accommodation of a propulsion unit, an intermediate portion suspending the lower body and providing interconnection, e.g. for air ducts, and an upper portion, which is attached (normally rotatably) to the ship via a seating, e.g. fixedly connected to a steering engine, with a gear ring to be fixed at the base.

It is a very time consuming operation to dismount/mount a pod unit, which is a drawback due to the fact that each day of still stand implies enormous cost for the ship owner. Many different principles for mounting dismounting are known, some of which will be described in the following and also some related known methods related to thrusters of similar size. What is common for all known methods is that they are either more time consuming than desired and/or too costly. US 7,549,903 B2 discloses a method and an auxiliary device in connection with disassembly and/or assembly of a tunnel thruster unit by use of the auxiliary device to guide the thruster unit and its movement during disassembly/assembly inside the tunnel. Thereafter the thruster unit is led away through the tunnel. The auxiliary device is removably fixed at the thruster unit before final disassembly, such that the auxiliary device controls the movement during disassembly/assembly, mainly by compressive forces. A traditional kind of lifting arrangement is used to mount dismount the thruster to/from its operational position. Floating marine vessels often contain multiple thrusters arranged to extend from the bottom of the vessel's hull. As disclosed in US 7,641,526, for example, azimuthing thrusters can be extended between a deployed position and retracted position. These thrusters can be affixed to canisters, which can be removable and movable as modular units. The movable and removable canisters can support at least one platform for holding personnel and can be between about 3 meters to about 30 meters in height, have an inner diameter between about 2.5 meters to about 7 meters, and they are movable between a deployed position and a retracted position. This modular design is stated to provide a great advantage in the ease with which the thrusters can be removed for maintenance, but suffers in a cost view point.

Another arrangement for fitting a thruster to an opening in a bottom structure of an offshore platform, for example, and for dismantling the thruster therefrom is disclosed in US 4,696,650. To enable the assembly to be fitted and dismantled from outside the shell structure and beneath the surface of the water on which the craft floats without requiring the assistance of a diver there are used a plurality of lines, which can be connected to lifting devices in the offshore platform and passed out through a corresponding number of line openings located in the shell structure on one side of the assembly mounting opening, so that the ends of the lines can be connected to the line attachments on the thruster. These line attachments are so arranged on the mounting flange of the thruster, that when the thruster is mounted and the mounting flange connected to the shell structure, they are located in the line openings and are accessible from inside the shell structure, thereby enabling the lines and the line attachments to be mutually connected from inside the offshore platform. The line attachments are provided with seal apparatus, which, when the thruster is mounted in position, close to the line openings, while on the inside of the shell structure adjacent each line opening there is provided a sealing chamber which surrounds the line opening and which is provided with a sealing lead-through for the line. As is evident such an arrangement requires a number of parts integrated in the shell structure, which may not be possible or at least not desired in relation to ships.

A thruster that is steerable through 360 degrees about a vertical axis but can be removed and replaced underwater is disclosed in US 4,634,389. The thruster unit can be supported from the vessel by means of a first single lifting wire that passes through a guide tube and is secured to a bracket attached to the lower portion of the thruster unit or alternatively to a bracket attached to the thruster unit. A mounting frame is attached to a nozzle radially outside of the propeller and is pivoted to the side or the bottom of the vessel. A second lifting wire is shackled to the frame. Mounting bolts that hold the thruster unit in place are then released, and the thruster unit is swung downwardly under the guidance of the frame and controlled by the first lift wire until the thruster unit is clear of the ship's side. The first lift wire is then disconnected and the thruster unit is lifted from the water. A disadvantage with this method is that it requires a large water depth, implying the drawback that in many places there is a need to perform the operation at position a large distance from a harbor area. A further principle is disclosed in US 6,564,736 B2, disclosing a device for installing and/or removing a steerable propulsion pod for a ship having two of said steerable propulsion pods, each pod comprising a lower body suspended from the ship by a stay. The device comprises a cradle for receiving the pod to be moved, which cradle is situated between two arms of a buoyant beam. One end of each arm is rigidly secured to the cradle, the other end of a first arm is provided with a coupling hinged about a horizontal pin for coupling it to the stay of the other pod in place on the ship, and the other end of the second arm is provided with a coupling hinged about a horizontal pin and about a vertical pin for coupling the second arm to an auxiliary vessel. This latter principle suffers from certain drawbacks, e.g. that the mounting/dismounting cradle device is rather bulky and also costly.

From US 4,696,650 there is known another method, wherein all lifting points are arranged on the same portion, i.e. onto a mounting flange, and where the lifting device is not anchored at a fixed part of the vessel/seating, but with a separate lifting device, which leads to a bulky and inflexible arrangement.

From JP 2005280486 there is known a further method, wherein the lifting point is in a sort of "cradle", i.e. not as a portion of the pod housing and further wherein lifting is performed in a complex manner.

Further there is known a method where lifting bars are used to lift the pod unit.

However, also this prior art method suffers from disadvantages.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a method of dismounting a pod housing, which has a lower body suspended from a marine vessel by an intermediate part of the pod housing, from a seating provided in a marine vessel or installing said pod housing in said seating, which method may be less time consuming than earlier methods.

In accordance with the present invention, this object is achieved by the use of a method as defined in claim 1.

In the present context, a "wire rope" preferably consists of several strands laid (or 'twisted') together like a helix. Further each strand preferably is likewise made of steel wires laid together like a helix.

In comparison to a prior art method where rods are used for lifting lowering the pod, the time for a pod change may be reduced with up to about 10-12 h, according to the preferred mode of the invention, thanks to the flexibility of the wire ropes. This time gain is achieved in that the propeller can be "pumped off ^* simultaneously with the installation of the lifting tackle. When using rods, this is impossible, since the pod may not be swung aside after pumping off the propeller and therefore the lifting arrangement may not be installed until after. Further, the wire ropes or wire rope groups used are easier to handle due to being less heavy and less bulky than lifting rods earlier used in prior art.

The basics of the invention may provide time gains, both when use in dry surroundings, e.g. a dry dock, but also when use in wet surroundings, e.g. when the marine vessel is carried by the sea.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the invention will be described in more detail with reference to preferred embodiments and the appended drawings.

Fig. 1 is a perspective view of a preferred embodiment of a pod unit having a pod housing, which has a lower body (hereinafter called machine housing) suspended from a marine vessel by a stay serving as a rudder, a propeller at a front end (hereinafter also called second portion) of the machine housing and a seating for permitting azimuthal rotation of the pod housing in relation to the marine vessel.

Fig. 2 is a perspective view of the pod unit of Fig. 1 with the propeller removed and a first lifting beam inserted through a horizontal through hole provided in an aft portion (hereinafter also called first portion) of the stay of the pod housing and extending out from the sides thereof to provide a first pair of lifting points.

Fig. 3 is a perspective view of the first lifting beam used in Fig. 2.

Fig. 4 is a perspective view of the pod unit of Fig. 2 with a second pair of lifting points formed by two lifting ears fixed in identical locations by screws to opposite sides of the front portion of the pod housing.

Fig. 5 is a perspective view of the lifting ears used in Fig. 4.

Fig. 6 is a perspective view of the pod unit of Fig. 4 with a reinforcement plate mounted on top of the seating.

Fig. 7 is a perspective view of the reinforcement plate used in Fig. 6.

Fig. 8 is a perspective view of the pod unit of Fig. 6 with an upper end of each of four wire ropes, or groups of wire ropes, anchored to the reinforcement plate, and a strand jack climbing each one of said four wire ropes or groups of wire ropes.

Fig. 9 is a perspective view of the pod unit of Fig. 8 with a slotted plate mounted on top of each of the two aft strand jacks.

Fig. 10 is a perspective view of the slotted plate used in Fig. 6.

Fig. 1 1 is a close-up perspective view of the top of one of the two aft strand jacks in

Fig. 9.

Fig. 12 is a perspective view of the pod unit of Fig. 9 with a second lifting beam

carried at its ends by the two front strand jacks.

Fig. 13 is a perspective view of the second lifting beam used in Fig. 12 and having a vertical slot for receiving an associated one of wire rope groups while permitting the second lifting beam to move up and down the wire ropes or wire rope groups.

Fig. 14 is a close-up perspective view of one of the slotted ends of the second lifting beam attached to its associated carrying strand jack in Fig. 12.

Fig. 15 is a perspective view of a bolt extending over the slotted end in Fig. 14 for preventing the wire rope or wire rope group extending through the slot from leaving the slot.

Fig. 16 is a perspective view of a locking pin used in Fig. 14 extending through a traverse bore at an end of the bolt for keeping the bolt in its intended position in the first lifting beam, the locking pin having a straight shank and attached to one end thereof a curved spring member for keeping the locking pin in its intended position in the bolt. Fig. 17 is a perspective view of the pod unit of Fig. 12 when the two aft strand jacks have climbed up sufficiently to support the ends of the first lifting beam. Fig. 18 is a close-up perspective view of the top of one of the two aft strand jacks and the end of the first lifting beam carried thereby in Fig. 17.

Fig. 19 is a close-up perspective view similar to Fig. 17 and illustrates how the end of the first lifting beam is anchored to the top of the strand jack.

Fig. 20 is a perspective view of an arched clamp used in Fig. 19.

Fig. 21 is a perspective view of bolt similar to that of Fig. 15 but used in Fig. 19. Fig. 22 is a perspective view of a locking pin similar to that of Fig. 16 but used in

Fig. 19.

Fig. 23 is a perspective view of a two-legged locking member used in Fig. 19.

Fig. 24 is a perspective view of the pod unit of Fig. 17 with two identical additional wire ropes, one end of which is shackled to an associated one of the two lifting ears and the other end is shackled to the center of the second lifting beam.

Fig. 25 is a perspective view of a shackle used in Fig. 24.

Fig. 26 is a perspective view of the pod unit of Fig. 24 after loosening of screws attaching the pod housing to the seating and lowering the pod housing to a cradle (not shown.

MODE(S) FOR CARRYING OUT THE INVENTION

The pod outboard unit 1 shown in Fig. 1 comprises a pod housing 2, which has a machine housing 3 suspended from a marine vessel (not shown) by a stay 4 serving as a rudder, a propeller 5 at a front end (hereinafter also called second portion) of the machine housing 3 and a seating 6 for providing sufficient structural strength to the pod unit in relation to the hull and normally for permitting azimuthal rotation of the pod housing 2 in relation to the marine vessel. There also exist fixed pod housings, e.g. one fixed in a group of three pod units, and as will become evident in the following the invention also may be used for fixed pod housings. Further it is evident that the invention is applicable irrespective if a pre produced seating 6 (a s shown) is used or if a the seating is of the kind constructed in situ, i.e. the hull being used to form the outer surface of the seating. The example pod unit 1 as shown in the figures is of a relatively wide size, implying a weight of the pod housing 2 and propeller 5 of about 200 tons. Hence it is a large unit approximately five meters high from the bottom of the machine housing 3 to the seating 6. To dismount the pod housing 2 from the seating 6, the propeller 5 is normally first taken off (not needed if spare propeller exists) in order to allow free passage for the later mooring of the pod housing 2. The propeller 5 then needs to be taken off at a swung out position. Accordingly prior to demounting, the pod housing 2 is swung, e.g. about 45 degrees, and in this position the propeller 5 is dismounted. As is well known per see the dismounting operation of the propeller is time consuming due to its complex fitting on to the shaft. Thanks to the invention, and the use of flexible lifting wires the lifting arrangement may be installed simultaneously with the demounting of the propeller. Accordingly at the same time as the propeller 5 slowly is being demounted, the following installation steps may be formed as will be described with reference to figure 2 etc. A first pair of lifting points 7, one on each side of an aft (hereinafter also called first portion) portion of the stay 4 of the pod housing 2 is provided, but only one of the first lifting points 7 is shown in Fig. 2. In the preferred embodiment shown in Figs. 2 and 3, the first pair of lifting points 7 is formed by two opposite ends of a first lifting beam 8 inserted through a horizontal through hole 9 shown in Fig. 1 and provided in an aft portion of the stay 4 of the pod housing 2 and extending out from the sides thereof. Each end of the lifting beam 8 has a vertical slot 10 for receiving an associated one of an aft wire rope or a wire rope group 11 while permitting the lifting beam to move up and down the aft wire ropes or wire rope groups 1 1. The open slots 10 make it possible to insert the first wire ropes or wire rope groups 11 sideways.

Then, a second pair of lifting points 12 (forward lifting eyers), one on each side at the propeller end of the machine housing 3 of the pod housing 2 is provided, but only one of the forward lifting points 12 is shown in Fig. 4. In the preferred embodiment shown in Figs. 4 and 5, each lifting point of the front second pair is formed by a lifting hig 12 having a shank 13 and at one end thereof an integral mounting flange 14 with a plurality of through bores for screws, not shown, for attaching the lifting lug 12 in horizontal position to the machine housing 3 by means of the screws. The other, free, end of the shank 13 has vertical side portions cut away to leave a central flat portion 15, which has a horizontal through bore 16 parallel to the longitudinal axis of the machine housing 3.

To reinforce the seating 6, a reinforcement plate 17 is then attached on top thereof as shown in Fig. 6. In Fig. 7, these reinforcement plates 17 are positioned actually in relation to holes 60 in the seating (see Fig. 4) intended for a passage of the lifting devices (herein lifting wires, as will be described more in detail below). The

reinforcement plate 17 is shown having three locating pins 18 intended to center the reinforcement plate 17 in relation to the larger holes 60 in the top surface of the seating 6 so as to place the reinforcement plate 17 precisely in the intended position on top of the seating 6. Accordingly the diameter of the hole 170 of the reinforcement plate 17 is smaller than the diameter of the holes 60 in the seating 6. Thanks to the use of this reinforcement which may be achieved in other ways (e.g. integrated in the seating in conjunction with its production), the seating may be used to bear the load during lifting, which provides considerable advantages.

When the marine vessel is in a dry dock, a hoist (e.g. air or manual, not shown) is installed on the machine room ceiling for pulling up aft wire ropes or wire rope groups 11 and front wire ropes or wire rope groups 19 from the dock to the machine room, one rope or rope group for each lifting point 7, 12. The length of each wire rope/group is preferably in the range of 5-15 meters, more preferred in a range 8-12 meters, but of course depending on the size of the ship/pod housing 2/seating 6, etc. Normally it is preferred to use a group of wires, then also to adapt the number of wires to the need of load to be handled. In this regard it is to be noted that the lifting points 7, 2 are positioned such that considerably different load may be taken by the different wire groups. In the shown embodiment, the wire groups to be used in connection with the first pair of lifting points 7 are positioned relatively close to the center of gravity of the pod housing 2 and will therefore take a larger portion of the total load than the wire groups at the second pair of lifting points 12. According to the preferred embodiment about 60-90 % of the load is handled by the wire rope /group 1 1 used with the first pair of lifting points 7. As a consequence, as in preferred embodiment where the same kind of strands in each wire rope/group is been used, two- four times as many wires/strands may be used in connection with the first lifting point 7 compared to those at the second pair of lifting points 12.

As shown in Fig. 8, an anchoring member 20 is attached to the upper end of each wire rope or wire rope group 1 1, 19, the anchoring members 20 are screwed tight against the reinforcement plate 17. Each anchoring members 20 is arranged with a corresponding number of vertical through holes (not shown) as the number of wires ropes in each group to arrange for safely keeping the ropes at desired distances in relation to each other corresponding to their position within the strand jack. These holes have a conical configuration to provide easy and safe anchoring of each rope/wire by means of interlocking wedge members (not shown). Strand jacks 21 are mounted on the wire ropes or wire rope groups 1 1, 19, and the strand jacks 21 to climb the wire ropes or wire rope groups 11, 19 a distance as shown in Fig. 8. Strand jacks are well known and constitute no part of the present invention. As an example, a hydraulic strand jack comprises a tubular double-walled cylinder for passage of the wire rope or wire rope group 1 1, 19 axially there through, a tubular double-acting piston located in the cylinder and having a piston rod extending out of the cylinder, and active able and deactive able locking members at the free end of the piston rod and at the opposite end of the cylinder. These locking members can be a sturdy plate having a central conical hole with a cone angel of about 14 degrees, and for locking the strand jack to the wire rope or wire rope group 1 1, 19, a conical wedge member having a central longitudinal bore for the passage of the wire rope or wire rope group 1 1, 19 there through and split radially into three identical parts is placed in the conical hole. When one end of the strand jack is locked by wedge action against the wire rope or wire rope group 1 1 , 19, the conical wedge member at the other end may be brought out of gripping engagement with the wire rope or wire rope group 19, so that the strand jack can expend or contract dependent on which side of the piston in the cylinder the hydraulic medium is fed to. When the piston has reached one of its end positions or any desired position there between, the conical wedge member is moved to lock its associated end of the strand jack to the wire rope or wire rope group 1 1, 19, whereafter the conical wedge member at the other end of the strand jack may loosen its locking grip, and the strand jack may be made to expand or contract to climb up or down the wire rope or wire rope group 1 1 , 19. In this way, a strand jack mounted on a fixed wire rope or wire rope group 1 1, 19 will be able to lift or lower a load when climbing up or down, respectively, and if the strand jack is fixed and the wire rope or wire rope group 11, 19 is movable, it will lift a load by pulling up the wire rope or wire rope group 1 1 , 19 and lower it by slacking the wire rope or wire rope group 1 1, 19.

As a next step illustrated in Fig. 9, a mounting plate 22 shown in Fig 10 is fixed by screws to an upper end wall of each of the two aft strand jacks 21. The mounting plate has a slot 23, which corresponds to the slot 10 in the first lifting beam 8 and is mounted with the slot opening facing away from the stay 4, so that the two slots coincide. Fig. 1 1 is a perspective view of the upper end of the strand jack 21 with the attached mounting plate 22 on an enlarged scale.

Thereafter, as shown in Fig. 12, a second lifting beam 24 shown in Fig. 13, which has a center and two opposite ends, is fixed by screws to an upper end wall of each of the two front strand jacks 21. The second lifting beam 24 may be lifted in place by a fork lift, for example. The underside of the lifting beam 24 may be provided with two feet 44, possibly adjustable, for protecting the lifting ears 12. Each end of the second lifting beam has a vertical slot 25 formed between two vertical triangular walls 26 for receiving an associated one of the front wire ropes or wire rope groups 19 while permitting the second lifting beam 24 to move up and down the front wire ropes or wire rope groups 19. The open slots 25 make it possible to insert the front wire ropes or wire rope groups 19 sideways. Fig. 14 is a perspective view of the upper end of the strand jack 21 with the attached end of the second lifting beam 24 on an enlarged scale. A through bore is provided in each of the two vertical triangular walls 26 for insertion of a bolt 27 there through for preventing the front wire rope or wire rope group 19 extending through the slot from leaving the slot. The bolt 27 is shown in Fig. 15 and has a locking pin 29 shown in Fig. 16 extending through a traverse bore 28 at an end of the bolt 27 for keeping the bolt in its intended position. The locking pin 29 has a straight shank 30 and attached to one end thereof a curved spring member 31 for keeping the locking pin 29 in its intended position in the bolt 27. It is evident that the skilled person will know of other locking devices that may be used, to fulfil the same function.

Next, as shown in Fig. 17, the pair of aft strand jacks 21 is made climb up the aft wire ropes or wire rope groups 1 1 until a light load from the ends of the first lifting beam 8 is carried by the aft strand jacks 21. Fig. 18 is a view on an enlarged scale of a lifting beam end carried by an aft strand jack. For securing an end of the first lifting beam 8 to the top of one of the aft strand jacks 21 as shown in Fig. 19, first a locking member 32 in shape of a sleeve 33 having two parallel longitudinally extending legs 34 is slipped on to the end of the first lifting beam 8. This locking member 32 prevents the pod housing 2 from sliding sideways on the first lifting beam 8. The free ends of the legs 34 are provided with a bore 35. Then, two arched clamps 36 are slipped on to the end of the first lifting beam 8, radially inside of the locking member legs 34, and the arched clamps are fastened by the same screws that secure the mounting plate 22 to the upper end wall of the aft strand jack 21. Thereafter, a bolt 37 is inserted through the bores 35 in the legs 34 and corresponding bores in the very end of the end of the first lifting beam 8 for preventing the front wire rope or wire rope group 11 extending through the slot from leaving the slot. The bolt 37 is shown in Fig. 21 and has a locking pin 39 shown in Fig. 22 extending through a traverse bore 38 at an end of the bolt 37 for keeping the bok in its intended position. The locking pin 39 has a straight shank 40 and attached to one end thereof a curved spring member 41 for keeping the locking pin 39 in its intended position in the boh 27. It is evident that the skilled person will know of other locking devices that may be used, to fulfil the same function. Fig. 24 shows that as a final step before demounting the pod housing 2 from the seating 6, two identical additional wire ropes 42 are connected at one end by shackles 43 to an associated one of the two lifting ears 12 and at the other end to the center of the second lifting beam 24. The shackle 43 used is shown in Fig. 25. Then, the pair of front strand jacks 19 is made climb up the front wire ropes or wire rope groups 19 until the two identical additional wire ropes 42 are tensioned and a light load from the ends of the second lifting beam 24 and exceeding the combined weight of the second lifting beam 24 and the two identical additional wire ropes 42 is carried by the front strand jacks 21. Now the four strand jacks 21 press the pod housing 2 lightly against the steering cone 6, and the screws that keep the pod housing 2 attached to the seating 6 can be loosened and removed, so that the strand jacks 21 can start climbing down the wire ropes or wire rope groups 11, 19 synchronously to lower the pod housing 2 as shown in Fig. 26. The pod housing 2 is lowered until it rests safely in a cradle or the like, not shown, which takes it away. When the weight of the pod housing 2 exerts no force on the strand jacks 21 and the wire rope or wire rope groups 1 1, 19, the shackles 43 can be disconnected from the lifting ears 12, the bolts 27 and locking pins 29 removed from the front lifting beam 24, and the screws connecting the ends of the front lifting beam 24 to the pair of front strand jacks 21 loosened and removed. Then, the front lifting beam 24 is lifted away, e.g. by a fork lift. Similarly, with reference to Fig. 19, it is possible to remove bolts 37 and locking pins 39 and also the arched clamps 36 and the locking members 32 from the aft lifting beam 8, so that also the aft strand jacks 21 can be lowered out of contact with the aft lifting beam 8. To mount a new pod housing to the steering cone, the above steps are reversed and executed in reverse order.

A person skilled in the art easily realizes that the steps described above can be modified to be carried out when the marine vessel is carried by the sea instead of being in a dry dock. The main difference is that the strand jacks, if they not are waterproof, can be kept dry by mounting them above the seating, preferably on top of the (reinforcement of) the seating. Then, the wire ropes or wire rope groups do not have their upper ends fixed to the seating but instead their lower ends are fixed at least indirectly to the lifting points. Thus, when operating, the strand jacks pull the wire ropes or wire rope groups and any possible loads carried by them upward, or lower them and their possible load. In a preferred mode the pod housing 2 may be provided with a detachable buoyancy jacket (not shown) to reduce its weight under water, which will require less load to be carried by the lifting arrangement. In a preferred embodiment this "wet method" is carried out in connection with a platform (not shown) positioned on the bottom of the see for placing of the pod housing 2 in connection with the mounting/dismounting. The invention is not to be seen as limited by the embodiments described above, but can be varied within the scope of the appended claims, as will become readily apparent to the person skilled in the art, for instance, it evident that the design of the lifting devices may vary substantially, e.g. using other kind of lifting means instead of beams and/or ears, providing the same basic function. Moreover the number of lifting points (i.e. wire rope groups if a plurality of wire ropes are used may vary depending on different needs/desires, e.g. be reduced to three lifting points if one common lifting point is used at one end, and still obtaining the advantages provided by the basic principles of the invention. Further it is evident that in the "wet mode" the "lifting jacket" can be arranged with the lifting points, supplementing the lifting points in the pod housing or indeed eliminating any need of lifting points in the pod housing. Further it is evident that the principles of the invention is not limited by the example described above with reference to the naming of "aft" and "front" devices/portions respectively, but that the principle is applicable irrespective of how the pod is to be used, i.e. that definitions related to first and second portion/s may be either aft/front or vice-versa, depending on use/application. Moreover it is within the scope of the invention to use other fixed parts of the ship, than the seating, to take the load from/anchor the wires during

mounting/dismounting of the pod housing. Further, it is to be understood that a lifting point may also be construed as a "non fixed" point in relation to the pod housing, e.g. contacting points between the pod housing and a lifting jacket. Another evident modification is to use the invention in connection with mounting/dismounting a thruster (i.e. having no motor in the lower body portion, but merely a transmission), and accordingly the expression "pod housing" must be given a broad interpretation also including thruster housings. In analogy therewith it is evident that the invention is applicable also if the "intermediate portion" is in any other kind than a stay. Moreover it is evident that the method according to the invention may advantageously also be used in connection with exchange of different parts, e.g. the slewing bearing of a POD (or a thruster), i.e. by dismounting the POD in accordance with the invention and then holding it while exchanging the desired part (or parts), which enables substantial time gain compared to conventional methods.