EP0082161B1

EP0082161B1 - Arrangement for launching a rescue vessel

Info

Publication number: EP0082161B1
Application number: EP82901862A
Authority: EP
Inventors: Ola Kristoffer Dalsbo
Original assignee: Individual
Current assignee: Individual
Priority date: 1981-06-24
Filing date: 1982-06-23
Publication date: 1986-01-22
Also published as: NO812152L; NO149990C; DK80083A; DE3268652D1; JPS58500990A; NO149990B; SU1256697A3; DK80083D0; EP0082161A1; IE830234L; FI75313C; FI75313B; WO1983000036A1; BR8207765A; FI830594A0

Abstract

Arrangement for launching a rescue vessel from an offshore platform or a vessel. A launching of the rescue vessel as far as possible from the carrying structure and with the bow turned away from this is desirable. It has a first, inner boom (11) carried pivotable around an axis (14) positioned substantially horizontally and perpendicularly to the length axis of the inner boom (11), and an outer boom (12) pivotably carried by the inner boom (11), with a pivoting axis (21) being substantially perpendicular to both booms length axis. The carrying wires (24, 25) are suspended from the outer boom.

Description

The invention relates to an arrangement for launching a rescue vessel from a ship or an offshore platform, wherein the rescue vessel is suspended under a boom with one or more hoist carried wires. More specifically, the invention relates to an arrangement of the kind described in the introductory part of claim 1.
For such an arrangement to function properly, it has to fulfill various requirements. The launching should be possible from a dead ship or platform as the power supply may be failing in an emergency state. It thus has to function without external supply of power, i.e. by means of the energy available in the arrangement itself.
Further it should be possible to launch the rescue vessel from a heeling ship or platform. It should move the rescue vessel as far away from the side of the ship or platform as possible and preferably turn the rescue vessel with the bow away from the ship or platform. The release should be simple to have the rescue vessel launched without assistance from any other than the operator responsible for the launching. The arrangement should not require unnecessary valuable space, and should preferably be a unit which can be mounted on existing platforms and ships.
In No-A-132.309 there is described a device for launching a rescue vessel with a boom which at its free end is carrying about a horizontal, transverse axis a tubeformed column for entering the vessel. This arrangement is unable to turn the rescue vessel with the bow away from the carrying structure, e.g. an oil drilling platform.
According to the invention these objects may be achieved by an arrangement for launching rescue vessels as stated in the characterizing part of claim 1. With this arrangement, the rescue vessel will not only be launched in a relatively large distance from the platform or ship, but will also have the bow turned away from the hull. By adjustment of the first boom, the launching may be adapted to various degrees of heeling, to have the rescue vessel always launched from a horizontal boom.
In the subclaims 2-10, various advantageous features of the arrangement according to the main claim are stated. These features will contribute to the favorable properties of the arrangement. This will be further described with reference to an example of an embodiment shown in the drawings:

Figs. 1 and 2 show a front view and a view respectively of an arrangement according to the invention carrying a life-boat, Figs. 3 and 4 show an upper plan view and an end view respectively of the arrangement with the inner boom lowered,
Figs. 5 and 6 shows an upper plan view and an end view of the arrangement of Fig. 1, with both booms lowered respectively turned in operative position for launching, while
Fig. 3 shows an embodiment of a hydraulic circuit suitable for controlling and operating the arrangement in the shown embodiment structure.

The arrangement of the shown embodiment comprises an inner boom 11 and an outer boom 12. The booms 11 and 12 are pivotable joined as described further below.
The inner boom 11 is carried by a mounting structure 13, to be pivotable around a horizontal axis 14 or an axis which can be placed in a horizontal position and which extends along the hull of the carrying ship. The mounting structure 13 may be a part of the ship or of an offshore platform.
The inner boom 11 is preferably bifurcated or provided with two legs 15, each being pivotably linked to a lug 16 with a bolt 17, the lugs 16 being a part of the mounting structure 13.
The inner boom 11 is further connected to the mounting structure 13 by a hydraulic cylinder 18, being linked to an attachment 19 at the free end of the inner boom 11 and an attachment 20 at the mounting structure 13. The control of the cylinder 18 with its piston is described further below. On extension of the cylinder, the inner boom 11 is pivoted from an upper position close to the mounting structure to a lower, protruding position as shown in Fig. 4.
The second boom 12 is linked to the inner boom 11 to be pivotable around an axis 21 at the free end of the inner boom, generally perpendicularly to the length axis of both booms 11 and 12, and the axis 21 is also situated in a plane perpendicularly to the axis 14.
The outer boom 12 is pivotable between an inner position (Figs. 1 and 3), wherein it has its length axis generally perpendicularly to the inner boom 11, and an outer position (Figs. 5 and 6) wherein the axis of the booms 11 and 12 extends in the same direction. This pivoting movement is effected by means of a power cylinder 22 which is linked between the booms 11 and 12 outside the pivoting axis 21. The control of the power cylinder 22 will be further described below.
The inner boom 11 may suitably be constructed as a box to have space available for the control gear described below, while the outer boom suitably is a truss beam or another suitable kind of beam.
The outer boom 12 carries a rescue vessel 23 by means of two wires 24 and 25. The wires 24 and 25 are attached to the vessel in a manner known per se. The wires run from the vessel over an inner lead sheave 26 and an outer lead sheave 27 respectively, and from these onto a double winch drum 28 arranged on the inner boom 11, in the shown embodiment between the legs 15. The sheaves 26 and 27 are attached to the outer boom 12 to allow pivoting of the rescue vessel 23 from the position shown in Fig. 1 wherein the wires 24 and 25 are extending substantially parallel to the inner boom 11, and to another end position as shown in Fig. 6, being situated substantially 90° to the first. The importance of this will appear from the descriptions below.
The wires 24 and 25 are carried by a double sheave 29 arranged adjacent to the axis 21 linking the booms 11 and 12.
In its inner position, the rescue vessel 24 will have its axis generally parallel to the side of the carrying structure 13 or part of it, which the lugs 16 are attached to.

Launching

The launching of the rescue vessel 23 is effected in three phases:

From the start/position shown in Figs. 1 and 2, the inner boom 11 is turned away from the carrying structure 13 and into the lower position shown in Figs. 3 and 4. In this position, the inner boom 11 should be generally horizontal, even if the carrying vessel or platform is heeling. The attainment of this end position is effected by means of the control gear described below.

Subsequent to the pivoting down of the inner boom 11, the pivoting of the outer boom 12 starts, the axis 21 being substantially vertically or inclined outwardly in the upper part. At the end of the pivoting movement, the booms 11 and 12 extend in the same direction. This is shown in Figs. 5 and 6.
As the third and final phase of the lowering, the rescue vessel 23 is lowered by releasing the wires 24 and 25. It is convenient to design the attachment of the wires 24 and 25 to be automatically released as the rescue vessel hits the sea.
As will appear from the description of the control system below, the lowering can be effected without external power supply and a high degree of self control. This means that the lowering in high emergency can be effected quickly and safely, without risk for failure due to human errors or insufficiency, e.g. due to reduced consciousness, lack of training etc.

The Control System

In Fig. 7 an example of a control system for the embodiment above is shown. The main parts in this system, in addition to a winch motor 30 connected to the drum 28, are the cylinders 18 and 22.
The cylinder 18 is over a release valve 31 connected to a pressure accumulator 32 and an oil reservoir 33. The connection between the release valve 31 and the accumulator 32 respectively the reservoir 33, is controlled by a three-way valve 34 maneuvered by a pendulum. The valve member 35 of the valve 34 is biased toward an end position connecting the cylinder 18 to the accumulator 32 and the oil reservoir 33. The connection to the reservoir 33 is however controlled by a safety valve 36 opening when the pressure of the accumulator 32 exceeds a predetermined level.
The accumulator 32 is connected by the valve 34 operated by the pendulum to the cylinder 22, to effect outward movement of the piston rod 37.
To brake the movement of the rod 38 of the cylinder 18, a choke valve 39 is arranged in the outlet to give a predetermined maximum lowering speed of the inner boom 11 at an expected weight of the rescue vessel 23.
Correspondingly a choke valve 41 is arranged in the outlet pipe 40 of the cylinder 22 to the oil reservoir 33, to limit the speed of pivoting of the outer boom 12.
To avoid return movement of the outer boom 12 when the lowering has started, a one-way valve 43 is arranged in the supply pipe 42 to the cylinder.
The valve 34 is designed to connect the accumulator 32 to the cylinder 22, when the valve member 35 is moved from the shown neutral position into the second end position by a pendulum 44. The pendulum 44 is journalled to effect switching of the valve 34, i.e. closing of the connection between the cylinder 18 and the accumulator 32 and opening of the connection between the accumulator 32 and the cylinder 22 when the inner boom has reached a horizontal position, independent of a heeling of the carrying structure 13.
The pressure side of the winch motor 30 on release of the wires 24 and 25 is connected to the oil reservoir 33 over a valve 45 which is opened when the outer boom 12 has reached its outer position. This may be effected by an activator or a release member 46, in the shown embodiment attached to the piston rod 37 of the cylinder 22. To have the lowering of the rescue vessel 23 controlled it is inserted a choke valve 48 in the outlet pipe 47 of the winch motor 30. During the lowering the winch motor 30 will act as a pump, powered by the force acting on the wires 24 and 25.
The lowering of the rescue vessel 23 thus is started by opening the valve 31 by an operating handle 49. Then the pivoting down of the inner boom 11, the pivoting out of the outer boom 12 and the lowering of the rescue vessel 23 is effected as described above.
Apart from the cylinders 18 and 22, the remaining parts of the control system of Fig. 7 will suitably be arranged in the inner boom 11, e.g. in its box structure. The operating handle 49 is conveniently arranged to be operated from the rescue vessel 23 in its start position as shown in Figs. 1 and 2.
The main advantage of the launching arrangement according to the invention, is firstly that it carries the rescue vessel 23 relatively far away from the carrying structure 13, and secondly that it turns the rescue vessel 23 to have its bow away from the carrying structure 13, ready to move or be towed away from the platform or the vessel. This is a particular advantage in bad weather and unfavourable wind, when the rescue vessel is liable to be thrown against the carrying structure or adjoining parts.
The arrangement described above may be modified in various ways. The most important relates to the design of the inner boom. This may be shortened to reduce its contribution to the outward movement of the rescue vessel 23. The basic principle is that it can move the linkage of the outer boom 12, to have its pivoting axis 21 moved from a position in which the outer boom 12 is locked up into a position close to vertical. It is particularly advantageous to move the inner boom 11 to have the axis 21 pointing outwardly in the upper end, from the platform or vessel. Thus the outer boom will be self pivoting toward the outer position. The accumulator 32 and the cylinder 22 may then be deleted, when this is allowed.
The winch arrangement may alternatively be positioned on the outer boom 12. On launching a rescue raft the winch may be of a modest size and only one wire may be sufficient.
The launching arrangement of the invention brings substantial advantages. It assures a 90° turning of the rescue vessel, to make this ready for movement away from the platform or support vessel. This turning will also make the rescue vessel less inclined to be thrown against the carrying structure.
The arrangement according to the invention allows launching also in a heeling situation and when the carrying structure is out of trim. To cope with the last possibility the inner boom 11 may be linked to be slightly pivotable around a central position, to have its axis 14 horizontal, when the carrying vessel or the platform is out of trim in either direction.
The launching arrangement according to the invention has a substantially larger extension than corresponding arrangements in the prior art. This increases the safety of launching, particularly in bad weather and heeling conditions. The safety is also increased due to the circumstances of launching without external power supply.

Claims

1. Arrangement for launching a rescue vessel from an offshore platform or a vessel, comprising an inner boom (11) carried pivotably around a substantially horizontal axis of support (14), and an outer boom (12) linked to the outer end of the inner boom, the outer boom carrying the vessel by one or more winchborne wires, characterized in that the outer boom (12) is linked with its inner end to the inner boom (¹1), about an axis (21) which is generally perpendicular to the inner boom and to its axis of support and that the inner boom (11) is so arranged as to provide space for operating gear.

2. Arrangement according to claim 1, characterized in that it is provided with a hydraulic cylinder (18), with a choking valve (39) in the outlet, to lower the inner carrying boom (11) around its carrying axis (14).

3. Arrangement according to claim 2, characterized in that the hydraulic cylinder (18) is connected to a pressure accumulator (32) to store a part of the energy released at the lowering of the inner boom (11), to provide energy to pivot the outer boom (12) from an inturned to an outturned position.

4. Arrangement according to claim 3, characterized in that the transfer of pressure fluid from the accumulator (32) to the cylinder (22) is governed by a pendulum operated valve (34) opening for the operation of the cylinder (22) extending its piston rod (37) only when the axis of linkage (21) is in a substantially upright position.

5. Arrangement according to one of the claims 1-4, characterized in that it is provided with means (45, 46) allowing pump operation of the winch motor (30) when the outer boom is in its outer extended position.