WO2014062113A1

WO2014062113A1 - A device for a floatable craft and a proceeding

Info

Publication number: WO2014062113A1
Application number: PCT/SE2013/051150
Authority: WO
Inventors: Martin Svensson
Original assignee: Stena Rederi Ab
Priority date: 2012-10-16
Filing date: 2013-10-02
Publication date: 2014-04-24
Also published as: SE1251168A1; GB2520908A; GB201506382D0

Abstract

The invention relates to a device (1 ) for a floatable craft (2), which comprises water jet nozzles (30, 40, 50, 60) arranged to eject water below the water line of the craft. According to the invention two or more water jet nozzles (30, 40, 50, 60), with opposite each other directed water jets (5-8) of equal sizes, and which are arranged to function as fins and dampers in order to reduce the motions of the craft (2) in the degrees of freedom of the craft (2), are supported by a unit (3) supported by the craft (2), or which are permanently built into the hull (20) of the craft below the water line (4) of the craft. Said opposite each other directed water jets (5-8) are arranged to make it possible to reduce the degrees of freedom of the craft. The invention also relates to a proceeding for this purpose.

Description

A device for a floatable craft and a proceeding The present invention relates to a device for a floatable craft, which comprises water jet nozzles arranged to eject water below the water line of the craft.

For a floatable craft inter alia Dynamic Positioning (DP) and anchoring systems are used in order to make it possible to keep the craft in a not moving position. Depending on the assignment of the craft various demands are made on keeping the craft in a not moving position or, vice versa, demands on maximal allowed motion. The motions of the craft depend among other things on environmental loads, waves, winds and currents, and of the design of the craft and the relative direction between environmental loads and the craft.

A floating craft moves in six degrees of freedom, which are described below:

· Heaving, which is the motion of the craft in the

vertical direction.

• Rolling laterally around an axis along the craft

through the centre of gravity.

• Pitching, which is rolling in the longitudinal

direction through an axis straight through the centre of gravity. In heavier sea it is called stamping .

• Surging, which means uneven motion caused by the

alternating deceleration and acceleration of the waves in the longitudinal direction of the ship.

• Swaying or oscillation, which includes lateral

motion backwards and forwards .

RECORD COPY-TRANSLATION

(Rule 12,4) • Yawing laterally around a vertical axis through the centre of gravity.

If the motions described above could be reduced, it would be possible to achieve a higher degree of utilization of the craft.

The purpose of a device known by

JP 61200087 A is to solve the problem in connection with rolling of a craft, i.e. one degree of freedom only, when the craft is rolling sideways around an axis along the craft and thereby through the centre of gravity.

By means of nozzles (6; 14; 18) water is ejected, so that vortexes 8 are formed, and which have an effect on the portions 5 of the craft in order to reduce the rolling moment on them. Thus, this is a technique which does not make it possible to get the craft to take a definite position when desired, so that the craft is not moved to undesired places or is subjected to other unwanted motions in the water.

Thereby, no water jets in pairs are used, which are directed towards one another and which have equal sizes in order to function as fins and dampers and to achieve said reduction of all six degrees of freedom.

A further device known by US 3,742,893A only exhibits water jet propulsion for a ship.

Especially in relation to a craft adapted to be used for example in connection with the offshore drilling for oil or other works at sea, there is a problem to get the craft in question to take a not moving and definite position, so that the drilling etc. is not nega- tively effected at the risk of damage to the drilling equipment, among other things.

The main object of the present invention is, therefore, in the first place to find a solution of said problem among other things, and which works with simple, well-tried means, quickly and effectively.

Said object is reached by means of a device according to the present invention, in that water is ejected in different directions at the same time.

Thereby, the motions of the ship are reduced.

Such a device according to the present invention is mainly characterized in that two or more water jet nozzles, with towards one another directed water jets of equal sizes, and which are arranged to function as fins and dampers in order to reduce the motions of the craft in the degrees of freedom of the craft, which are supported by a unit supported by the craft, or which are permanently built into the hull of the craft below the water line of the craft, are provided to make it possible to reduce the degrees of freedom of the craft by means of said water jets.

The invention also relates to a proceeding for a floatable craft in order to get the craft in ques- tion to take a not moving and definite position by means of a device for this purpose.

Such a proceeding according to the invention is mainly characterized in that in pairs towards one another directed water jets are ejected at the same time from water jet nozzles, which are provided on the craft below its water line in desired directions, so that motions in the degrees of freedom of the craft are reduced by means of said water jets.

The invention is described in the follow- ing with reference to the accompanying drawings, in which

Fig. 1 is a sectional view of the hull of the lower portion of a craft, Fig. 2 schematically illustrates the invention and its function, seen from above, and

Fig. 3 schematically illustrates the underside of a craft and the invention in perspective, obliguely from below.

A device 1 according to the present invention for a floatable craft 2 comprises a unit 3, which is supported by the craft 2 below the water line 4 of the craft. Said unit 3 is provided in order to make it possible to eject water jets 5-8 in desired directions 9-12. Thereby, it is possible to reduce motions in the degrees of freedom of the craft by means of said water j ets 5-8.

By means of said water jets 5-8 the motions of a craft are reduced in all said six degrees of freedom, i.e. heaving, rolling, pitching, surging, swaying and yawing.

By means of at least two, but preferably more, water jet nozzles 30, 40, 50, 60, which are located under the craft 2 and which are directed for example along 13 and across 14 the craft 2, diametrically opposite to one another, distributed along the periphery, the desired result to reduce the motions of the craft by ejecting water jets 5-8 in desired directions 9-12 is achieved. Said water jets 5-8 are directed towards one another and are of equal sizes. Thereby, they are arranged to function as fins and dampers in order to reduce the motions of the craft 2 in the degrees of freedom of the craft 2.

For a craft 2 already built, i.e. an already existing craft 2, the invention may comprise one or more units 3 in the form of so called "damping cases", which is/are placed under the craft 2, suitably easy to dismount. The attachment may be performed in any suitable known way, for example by welding, bolting, adhesive means, etc. Thus, the water jet nozzles 30, 40, 50, 60 in guestion are located and supported in one and the same, preferably box-shaped unit 3, which can be attached to the bottom 15 of the craft and which preferably is dismount- able. Suitably, said unit 3 is sguare-shaped or has another shape with an even number of substantially

vertical sides 16-19, at which the water jet nozzles 30, 40, 50, 60 are provided.

For a craft 2 under construction the invention, and its technigue to provide the water jets 5-8 in desired directions 9-12 by means of the water jet nozzles 30, 40, 50, 60 in guestion, can suitably be arranged to be permanently built into the hull 20 of the craft 2 below the water line 4 of the craft.

Thereby, several groups of water jet nozzles 30, 40, 50, 60 can be provided along 13 the craft 2 at a mutual distance from one another. For the operation of said water jet nozzles 30, 40, 50, 60 one or more pumps can be provided in the craft 2 or in a said separate box- shaped unit 3. Thereby, the surrounding sea water can be used to be ejected from the unit 3 or from the craft 2 in two or more towards one another directed water jets 5-8. The water jets 5-8 have egual sizes in order not to generate a net force, which in itself strives to move the craft 2. Then the water jets 5-8 function as fins, and these act as dampers and reduce the motions of the craft 2.

Further, more than one nozzle 30, 40, 50, 60 can be directed in the same direction 9-12, and said nozzles 30, 40, 50, 60 are provided at the same level seen when the craft 2 is located normally in the water 23.

Finally, it can be mentioned that the nozzles 30, 40, 50, 60 in question are stationary or movable laterally 14 and/or vertically 24.

The function and the nature of the invention should have been clearly evident from the above description and the illustrations of the drawings.

Of course, the invention is not limited to the embodiments described above and illustrated in the accompanying drawings. Modifications are possible, especially as far as the nature of the different parts is concerned, or by using equivalent technique, without departing from the scope of the invention as it is defined in the patent claims .

Claims

PATENT CLAIMS

1. Device (1) for a floatable craft

which comprises water jet nozzles (30, 40, 50, 60) arranged to eject water below the water line of the craft, characterized in that two or more water jet nozzles

(30, 40, 50, 60), with towards one another directed water jets (5-8) of equal sizes, and which are arranged to function as fins and dampers in order to reduce the motions of the craft (2) in the degrees of freedom of the craft (2), which are supported by a unit (3) supported by the craft (2), or which are permanently built into the hull (20) of the craft below the water line (4) of the craft, are provided to make it possible to reduce the degrees of freedom of the craft by means of said water jets (5-8) .

2. Device according to Claim 1, characterized in that at least two, but preferably more, water jet nozzles (30, 40, 50, 60) are provided under the craft (2) in order to make it possible to eject water jets (5-8) in desired directions (9-12) at the same time.

3. Device according to anyone of the preced- ing Claims, characterized in that the water jet nozzles (30, 40, 50, 60) in question are provided in one and the same, preferably box-shaped and/or dismountable unit (3) which can be attached to the bottom (15) of the craft.

4. Device according to Claim 3, characterized in that said unit (3) is square-shaped or has another shape with substantially vertical sides (16-19), at which the water jet nozzles (30, 40, 50, 60) are provided.

5. Device according to anyone of the preced- ing Claims, characterized in that several groups of water jet nozzles (30, 40, 50, 60) are provided along the craft

(2) at a mutual distance from one another.

6. Device according to anyone of the preced- ing Claims, characterized in that one or more pumps (22) are provided in the craft (2) or in a said separate unit

(3) .

7. Device according to anyone of the preced- ing Claims, characterized in that more than one water jet nozzle (30, 40, 50, 60) are provided at the same level, seen when the craft (2) is located normally in the water (23) .

8. Device according to anyone of the preceding Claims, characterized in that said water jet nozzles (30, 40, 50, 60) are provided at the same level, seen when the craft (2) is located normally in the water (23) .

9. Device according to anyone of the Claims

7-8, characterized in that the water jet nozzles (30, 40, 50, 60) in guestion are stationary or movable laterally (14) and/or vertically (24).

10. Proceeding for a floatable craft (2) in order to get the craft (2) in guestion to take a not moving and definite position by means of a device (1) for this purpose according to anyone of the preceding Claims, characterized in that in pairs towards one another directed water jets (5-8) are ejected at the same time from water jet nozzles (30, 40, 50, 60), which are provided on the craft below its water line (4), in desired directions (9-12), so that motions in the degrees of freedom of the craft are reduced by means of said water jets (5-8) .