Method and arrangement for attachment and/or disassembly/assembly of a tunnel thruster

A method and an assembly/disassembly arrangement for a tunnel thruster unit includes a thruster unit and a tunnel, a first attachment arrangement for fitting of said thruster unit to the tunnel and at least one further attachment arrangement for safe fitting of the thruster unit in the tunnel. A further attachment arrangement is in the form of a first interface device fixedly attached to and protruding from attached to the inside of the tunnel wall and a second interface device fixedly attached to the thruster unit.

TECHNICAL FIELD

The present invention relates to a method and an assembly/disassembly arrangement for a tunnel thruster unit, comprising a thruster unit and a tunnel, a first attachment arrangement for fitting of said thruster unit to said tunnel and at least one further attachment arrangement for safe fitting of said thruster unit in said tunnel, wherein further attachment arrangement is in the form of a first interface device attached to the inside of the tunnel wall and a second interface device fixedly attached to said thruster unit.

PRIOR ART

A tunnel thruster is a propeller unit mounted in a tunnel to achieve a lateral thrust in order to steer a ship or a platform. In order to facilitate, the term “thruster unit” will in the following be used to denote the actual propeller unit for such a tunnel thruster. Some complications exist when disassembling or assembling such a tunnel thruster. One complication is the limited space defined by the tunnel, leading to difficulties in the disassembly/assembly and that the thruster unit is easily damaged during disassembly/assembly due to narrow margins between the propeller ends and the tunnel wall. Yet another difficulty is caused by the drive shaft of the thruster unit having to project beyond its point of attachment in the tunnel, whereby the height of the thruster unit will be considerably much larger than the diameters of the propeller and tunnel. This is because it is desired, in order to achieve a good thruster capacity, to have a tunnel diameter that is as close as possible to the propeller diameter.

Traditionally, essentially according to the principles of U.S. Pat. No. 3,002,486, U.S. Pat. No. 4,036,163 and U.S. Pat. No. 4,696,650, blocks and tackles are used to move the thruster unit during assembly/disassembly. It is realised that in the limited space offered by the tunnel for the mechanician to work in, it may be difficult by such a method to achieve appropriately controlled guiding.

It is realised that the complications mentioned above mean that traditionally it is avoided to perform such operations below the water surface, since underwater assembly constitutes an additional complication, and therefore that such operations are traditionally made in a dry dock, which is very costly, quite often meaning a cost of at least 200,000 Euro per day, excluding downtime costs for the ship.

From WO 2005/100151 there is known a method and arrangement for attachment and disassembly/assembly respectively of a tunnel thruster which solves many of the above mentioned problems. However, despite the fact that this novel solution provides numerous advantages compared to traditional prior art there still remain complications that may lead to time consuming steps and/or extra cost in connection with assembly and/or disassembly respectively.

BRIEF SUMMARY OF THE INVENTION

It is an object of the present invention to eliminate or at least minimize the above mentioned problems, which is achieved by means of an arrangement according to the pending claims and method in connection therewith respectively.

Thanks to the new arrangement and method many advantages are achieved, which among other things means that in a preferred embodiment disassembly/assembly of a tunnel thruster can be made under water in a manner that is cost and time saving and which may provide increased security.

DETAILED DESCRIPTION

FIG. 1shows a vertical cross-sectional view transversally through a tunnel4having cylindrical inner walls3intended for flow of water by means of tunnel thruster unit2. In a traditional manner the thruster unit2is attached with its upper end within a mounting flange31in the upper portion of the tunnel4. Further it is shown that the thruster unit2is attached also at a lower portion106,107thereof. A plate102, is securely attached to a bottom part of the housing of the thruster unit2, by means of the appropriate fixings, e.g. welds, and/or bolts. This plate102, extend horizontally in a transverse direction in relation to the longitudinal extension of the tunnel4. At the same level, and within potentially the same plane, plates100,104are also fixedly attached to the inner wall3of the tunnel. As best seen inFIG. 3the length of the plates102, and100,104respectively are such that a gap t exists between the opposing edges of the plates, when the thruster unit2is in position for attachment. This gap t may be created by means of cutting it, i.e. having the plates100,102and104, respectively forming an integral plate section prior to cutting them apart whereby the gap t is formed. Indeed this will normally be the case in connection with after installation of an arrangement according to the invention, because in many installations that kind of a supporting plate is used, i.e. bolted to the thruster unit2and welded in to the tunnel3. However, also in connection with new installations one may use the same kind of principle to form a gap t. An advantage of using such a gap t is that it may make it easier to attach the intermediate plate102to the unit2into position, since the two gaps t on each side will provide a play.

As shown inFIGS. 1-3clamping means101,103are used to fixedly attach the plates100,102,104, to each other. Each clamping means101,103, seeFIG. 3, comprises an upper half101A and a lower half101B which are clamped together by means of an appropriate numbers of bolts101D, wherein the extension1of the clamping means101is large enough to provide a very secure and stable attachment,103, It follows, that in the plane of the plates the width1substantially exceeds the gap t, preferably in the range of 10-50× the width t of the gap. However, it is well understood that there is no actual need for a gap t between the plates100,102,104, by means of the clamping devices101,103. Also in the other direction, i.e. parallel with the extension of the tunnel, the clamping devices101,103, have a substantial length, indeed preferably larger than the extension in the extension1in the transversal direction thereof. A plurality of bolts101D (seeFIG. 2) are positioned in a first row passing through holes in the plate105, (seeFIG. 3, showing an enlargement of one side along III-III inFIG. 2) attached to the unit2and a second row of bolts through another row of holes in clamping device103and the plates101attached to the tunnel3. Accordingly a very rigid attachment is achieved. Moreover the arrangement of the attachment is such that it is easily fitted also under difficult conditions and being such that once the number of bolts have been tightened the desired positioning of the thruster2is achieved.

FIG. 4shows, in a side view, a cross-section of a tunnel4inside which a thruster unit2is to be mounted. The thruster unit2comprises a propeller journalled in a gear mounting/housing, which in turn has a fitting23for attachment to a flange31inside the tunnel4, as is known per se. The tunnel4is delimited by a cylindrical wall3in the side of which said flange31is positioned in the middle and at the top.

FIG. 4shows an initial phase of an assembly of such a thruster unit2, wherein a watertight mounting hood5is (as is known per se) fitted on top of the position of fitting of the axle journal of the thruster unit2. In the most left hand part ofFIG. 4the thruster unit2is shown in a position outside of the tunnel4, i.e. before it is actually moved into the tunnel. In accordance with what is described in WO 2005/100151 (which is hereby introduced by way of reference) the thruster unit2is arranged with an auxiliary transportation device1, to enable easy and secure movement of the thruster unit2within the tunnel4. Preferably the plate102has been removed from the thruster unit2, prior to mounting of the transportation device (e.g. prior to demounting from the tunnel) to facilitate easier fixing of the transportation device1. In this position the thruster unit2with the auxiliary device1is moved into the correct position by means of any suitable, e.g. traditional, lifting equipment (not shown) via a wire205. In order to be able to easy find the correct position of the unit2for introduction into the tunnel4, the auxiliary device1is preferably arranged with a first part of sensor arrangement300,301, that is cooperating with matching second part302on an installation arrangement20. This sensor arrangement301,302allows for exact positioning of the thruster unit2before movement into the tunnel4, whereby cumbersome adjustments may be eliminated, which otherwise very often are needed. The sensor arrangement301,302may be of a traditional kind that allows for positioning the thruster unit2with the auxiliary device1in an desired position. Thereafter the unit1,2may easily be pulled into the tunnel4by means of wire204. As shown inFIG. 4(left hand side) such a wire204may either be attached to the thruster unit2or alternatively the wire204′ may be attached to the exterior device1. A pulling unit203attached to the installation arrangement20may thereafter easily pull the wire204to move the unit1,2into a desired attachment position within the tunnel4. Once in that position a further wire7is attached to the unit1,2, which wire7by means of a lifting device50is used to move the thruster unit2in contact with the mounting flange31, and subsequent fixing thereto.

InFIG. 6there is shown a cross-sectional view from above as indicated inFIG. 5. BothFIGS. 5 and 6show the installation arrangement20as a hole, seen from two different positions. As can be noted the installation arrangement20is attached to the fixed mounting plates100,104(also named first interface device), which later are to be fixed to the thruster unit2, by means of fixing devices206,207. Securely (e.g. by welds) attached to said fixing devices206,207there extend arm portions200,201, symmetrically in relation to the centre of the tunnel, inclined upwardly an angle α and also inclined slightly inwardly to converge in the direction towards a centre line of the tunnel4. A crossbar202is fixedly attached to the other ends of each arm200,201. The crossbar extends transversally in the tunnel having its longitudinal centre substantially coplanar with a horizontal, central plane of the tunnel4. Substantially coaxial with the centre line of the tunnel4there is fixedly attached to the crossbar202a pulling device203. Also, substantially coaxial with the centre line of the tunnel4the crossbar202is arranged with a through hole205for passage of the wire204leading into the pulling device203, which is arranged with a mechanism, that is known per se, that may step-wise pull the wire into the tunnel4(seeFIG. 9). As is known per se, the pulling device203uses two grabbing units233,234working intermittently, to stepwise hold and pull the cable204respectively. The rear grabbing device234is used to pull the wire204, by means of moving the outer telescopic part232of the pulling device203by the use of hydraulic cylinders230. The functioning of the rear grabbing part234is such that as soon as the telescopic part232starts moving it will grip onto the wire204and pull it together with the movement of the telescopic part232. Once fully extended, the telescopic part232will be reversed, inwardly, whereby the rear grabbing part234loses its grip and instead the front holding part233will grab on to the wire204to not let it move in the direction of the movement of the telescopic part232. Accordingly a safe and secure movement of the thruster unit1,2may be achieved.

InFIGS. 6,7and8it is shown in detail that each fixing device206,207comprises a lower plate206A and an upper plate206B, that by means of bolts208can be securely fixed onto the fixed attachment plates100,104. As depicted preferably the attachment plates100,104are arranged with through passages100A,104A to allow for flexible positioning/clamping of the fixing devices206,207by means of the bolts208. Further, it is to be noted that the transversal extension w of the fixing devices206,207is less than the transversal extension W of the attachment plate100,104. Thanks to this the fixing devices206,207will not extend into the zone where the gap t is arranged between the thruster unit2and the attachment plates100,104. Accordingly the installation arrangement20is designed such that it does not disturb the movement and/or positioning of the thruster unit2into its correct mounting position, partly by not presenting any hindering protruding portions and also by having the crossbar202for the pulling device203arranged a substantial distance L away from the position of the centre of the thruster unit2in its fitted mode.

InFIG. 10it is shown in a schematic manner a cross-sectional side view of a hood5mounted on top of the attachment flange31of the tunnel wall3as is known per se, the hood5is used to seal the passage up through the tunnel wall3, to allow for fitting of the thruster unit2, and its attachment flange23without water flowing into the interior of the ship.FIG. 10further shows that there is a lifting unit50, to lift the wire7attached to the shaft journal of the thruster unit2. As indicated in this preferred embodiment exactly the same kind of principle, as is shown inFIG. 9, is used for the lifting device50as for the pulling device203, i.e. a hydraulic self grabbing pulling device by means of which an easy lifting is achieved.

InFIG. 11there is shown a schematic side view of a sliding device1as mentioned above, which has been arranged with a hydraulic subsystem170, which herein is merely schematically indicated. The hydraulic subsystem170comprises a plurality of hydraulic cylinders, preferably water hydraulic, that are used to move and adjustably position the base17for attachment to the thruster unit2. By means of an arrangement as shown inFIG. 11, a plurality of advantages may be achieved in some applications. For instance in connection with fitting of a thruster unit2wherein the tunnel34is not straight lined, but comprises curved portions, there may exist a need for changing the position of the thruster unit2during movement passed said curved portion. Thanks to the adjustable hydraulic subsystem170such adjustments may be achieved. Furthermore, the subsystem170may indeed in some installations be used instead of a lifting device50. As mentioned, in the preferred embodiment water hydraulics are used containing a plurality of differently positioned/inclined piston cylinder units controlled by a valve controlling unit171. Preferably the pressure pump (not shown) for powering the hydraulic unit170is positioned on the ship (or a supporting vessel), connected to the hydraulic unit170by appropriate flexible tubing. A working pressure of about 8-12 Mpa, maximum water flow of about 5-10 liters/minute and a volume of about 40-80 liter is appropriate, for most applications. The valve controlling unit171may in many installations preferably be of a pneumatic kind, but also remotely controlled wire/tubeless control arrangements may be used. Preferably the hydraulic unit170provides lateral tilt, cross-directional tilt, raise/lowering, sideways movement and rotation.

The invention is not limited to what has been described above but may be varied within the scope of the claims. It is also realised that even if the assembly as described advantageously can take place underwater, it is obvious that in certain situations the method and the auxiliary device can be used also at dry or semidry conditions. For instance it is evident to the skilled person that other structures than plates may be used to achieve the desired support between the interfaces and the tunnel3and thruster unit2respectively. Moreover it is evident that a gap t is not necessary, but that for instance, instead of parallelly extending opposing surfaces on each side of the interfaces, V-shaped (seen from above) dividing interface may be used, positioned such that the diverging side thereof opens up in the direction into the tunnel3from where the thruster unit2will be moved into its position for attachment. Further it is evident that in some embodiments the plate102may be left attached to the thruster unit2, during demounting/transportation/repair, wherein the interface between the transportation device1and the thruster unit2is appropriately adapted thereto.