GB2123353A - A survival cabin for use at an offshore vessel - Google Patents

Abstract

A survival cabin for an offshore vessel includes a buoyant capsule (10), which normally hangs in a davit (30) at least partly outside a side of the vessel. The davit comprises a basically Z- shaped arm structure (35) which is pivotably supported at a considerable distance below the deck (32) of the platform, and carries the capsule at a single point. The davit is operated by a brake (42), which permits the folding- out of the davit to a position, where the capsule reaches a maximum distance from the side of the vessel. The davit pivoting is controlled by a hydraulic piston or pump brake. An accumulator in the hydraulic circuit raises the arm after release of the capsule. The capsule has a false bottom with holes to allow water inflow thus dampening impact with the water after a free drop, and it has an auto-pilot governing an azimuth propeller, which will bring the capsule away from a damaged vessel in a preselected direction. <IMAGE>

Description

SPECIFICATION A survival cabin for use at an offshore vessel The vessels used for drilling purposes, or for housing the operating crews at offshore oil fields, are subjected to casuality risks, including structural collapse due to material defects or collisions which result in capsizing, as well as explosions and fires.

It is desirable to provide survival means, where the crew is better protected than in conventional lifeboats. On many occasions it is not necessary to abandon the vessel immediately, but there ought to be some safe place to which the crew can retire, be counted-in, and in proper order decide if and when they are to leave the vessel.

Using todays technique the crew will statistically have only a 50% chance of survival if they use a conventional lifeboat. This may easily be smashed against the columns of the vessel, it may turn over when reaching the surface of the sea and be filled with water, and it may be difficult to start the engine due to unfavourable surroundings.

The object of the present invention is to provide a survival capsule including means for launching the same at a safe distance from the columns of the vessel. The capsule shall be provided with means so it is automatically removed from the vessel in a predetermined direction, it shall, by itself, float away from the vessel if this should sink, and it shall be disengaged from a single point of support, so there are no problems in synchronously disengaging several supports. The capsule shall furthermore be so strong that it, in case of need, can drop down from its support.

A survival cabin according to the invention comprises a buoyant capsule, as well as a davit for normally carrying the capsule at least partly outside a side of the vessel and being accessible from the deck thereof and is characterized in that the davit comprises an arm structure, which is pivotably attached to the vessel at a considerable distance below its deck and carries the capsule at a single point, and that the davit is governed by a braking system, which, when released, permits an unfolding of the davit to a position where the capsule reaches a maximum distance from the side of the vessel, and then automatically releases the capsule.

The capsule is preferably provided with dampening means permitting a free drop from considerable height. The dampening means may comprise a space located outside the watertight bottom structure of the capsule, and said space being defined by a bottom plating provided with a number of openings permitting the entrance of water.

The capsule is advantageously enclosed by a deformable fender of steel plate and the abovewater structure of the capsule is preferably covered by a heat insulating layer.

The arm structure is preferably located that much below and inside of the center of gravity of the capsule, that an automatic lowering of the same is brought about as soon as the brake is released.

The distal end of the arm structure is advantageously formed as a shallow hook, which carries the capsule in an open link.

The link is preferably mounted at the cabin by means of an explosive bolt, or other rapid-release device permitting manual actuation.

Means connected to the brake are preferably adapted to automatically lift the arm structure as soon as the capsule is released.

The capsule is preferably provided with a pulling azimuth propeller, as well as with an auto-pilot operating the same, and being programmable to steerthe capsule in a desired direction away from the vessel.

The invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 schematically shows a longitudinal section through the capsule, Figure 2 is a cross-section through the same, the left half being a section along line Ila - Ila and the right half being a section along line llb - llb in Figure 1, Figure 3 shows, in a somewhat reduced scale, a side view of the capsule hanging in its davit, Figure 4 shows the capsule and the davit as viewed from above, Figure 5 shows a side view of the davit, illustrating its mode of operation, and Figures 6 and 7 show two alternative means for braking the movements of the davit.

The survival cabin 10 shown in Figures 1 and 2 is intended for use at an offshore drilling rig, and includes a buoyant capsule with two decks 11, 12 for accomodating crew members having access to the capsule by way of a centrally located tower 13. The crew members lie, or rest in inclined positions in suitably formed chairs 14 - shown in the right half of the capsule only.

The tower 13 is provided with a number of doors 15, which permit a rapid transfer from the vessel to the capsule, and which will be closed when all members are inside the capsule. The abovewaterline part of the capsule - which when the capsule hangs in its davit will at least partly project above the deck of the vessel - is covered by a heat insulating layer 16, and a deformable fender 17 of steel plate encloses the capsule to protect the same from collision damages.

Within the capsule there is a powerful engine 18, and a large starting battery 19. The engine drives a hydraulic pump 20 as well as an electric generator.

There are simple toilet facilities, and as the capsule in the case of a oil fire or bad weather may have to be hermetically closed, there must be means for purifying the air, and possibly also for adding 02.

The capsule is furthermore provided with an antenna 21 for sending emergency signals and carrying a high-intensity blinker.

The capsule hangs in an open link 22 in the davit to be described more in detail herebelow. The aim is that the capsule shall be automatically disengaged from the davit, when this has been swung out to a certain position, or if the vessel should sink very rapidly.

There are however also means to release the capsule from inside thereof, for instance by a manually activated explosive bolt.

The capsule must be able to withstand a free drop, also from its normal position of suspension, and is therefore provided with means for dampening the impact upon the water surface.

The lower deck 11 serves as the watertight bottom of the capsule, and below this deck there is a void space 23 outwardly defined by a false bottom 24. A number of water passages 25 are formed in this bottom. This will serve as a bumper and the passages will impart a turbulent movement in the water flowing into the space, which aids in taking up the impact. A certain deformation of the false bottom may also be caused.

An important factor in a salvage operation is that the capsule can be rapidly moved away from a sinking or burning vessel. The capsule is provided with a 360-rotatable, so called pulling azimuth propeller 26, preferably of the shrouded type and designed to pull the capsule.

The capsule is provided with a manually operated device 27 for governing the propeller, but has also an auto-pilot 28. This can be programmed so it will automatically steer the capsule away from the vessel in a predetermined direction.

The diesel engine 18 will be started as soon as any member of the crew has entered the capsule, the auto-pilot is always connected to the propeller for operation in a predetermined direction, and as soon as the capsule disengages from the davit, the hydraulic driving means for the propeller is activated. That the propeller is pulling instead of pushing means that the steering away from the scene of a disaster will be easier.

Figures 3 and 4 show how the capsule 10 hangs in a davit 30, which is mounted at one side of the vessel. This includes a box-like deck structure 31, which is carried by columns (not shown) and resting upon pontoons. The deck structure may include several tween decks, and comprises localities for the crew, stores, work-shop and the like. The weather deck is denoted by 32, the side plating is denoted by 33, and the bottom plating of the box structure is denoted by 34.

The davit 30 comprises a triangular arm structure 35, which is pivotably supported in the bottom plating of the box structure, and has sufficient height to hold the tower of the capsule at a suitable level in relation to the weather deck of the vessel. Shelters or portions of deck houses (not shown) may facilitate communication between the vessel and the capsule.

Figure 5 shows an end view of the davit and the capsule. The arm structure is basically Z-shaped, and includes two central beams 36 of about the same length as the height of the deck box structure 31, as well as two lower beams 37, which are attached to pivots 38 fitted below the bottom plating of the box structure. The lower beams have such a length, that an imaginary line 39 from the axis of pivots 38 through the point of gravity of the capsule will be inclined ensuring an automatic folding-out of the davit as soon as it is released.

The upper ends of the two beams 36 are interconnected and are continued by a single beam 40, which in a normal, rest position extends upwardly/outwardly from the weather deck of the vessel, and is terminated by a shallow hook 41, which carries the open link 22 mentioned in connection with Figure 1.

The capsule will thus be suspended at a single point only, and can easily be disengaged from the hook 41. As is indicated by broken lines in Figure 5, the davit will fold down to a position, where the central beams 36 are approximately horizontal, whereupon the link 22 will automatically slide off the hook. Should the vessel sink, the link will be automatically, lifted off the hook by the buoyant capsule.

The folding-down movement of the davit is determined by a braking means, which in Figure 5 is generally denoted by 42. Two alternative embodiments of braking means will be described in connection with Figures 6 and 7.

By providing a considerable length at the central arms 36 the capsule will be brought a distance away from the vessel, and due to the shape of the lower beams the capsule will have been lowered further downwards at the movement of disengaging from the davit.

Normally the capsule shall disengage from the davit when it still hangs a distance above the water level 43.

A first embodiment 42a of a davit braking means is shown in Figure 6. As is mentioned above the davit 30 is designed so it will automatically fold outwards as soon as the brake is released.

The davit is guided by at least one wire 45, which is led over sheaves 46,47 mounted at the cylinder and at the piston rod, respectively, of a hydraulic piston ram 48. This has a sufficient stroke and/or the wire is led a number of turns over the sheaves to permit the davit to perform the folding-out movement indicated in Figure 5.

The outward ends of the hydraulic ram cylinder are connected to a hydraulic circuit 49 including a remote-controlled starting valve 50 and an adjustable throttle valve 51.

Normally the piston of ram 48 rests in its pushedout position so the sheaves 46,47 will be located at a maximum distance away from each other. The starting valve 50 is closed, and prevents fluid flow in the hydraulic circuit 49.

When valve 50 is opened the davit starts to swing outwards, and puts a tension to wire 45. The sheaves 46, 47 will then be forced towards each other at a rate determined by the flow through the throttle valve 51. the magnitude of the folding out movement will, as mentioned above, be determined by the length of the wire 45.

The hydraulic circuit 49 includes an accumulator 52 connected between the throttle valve 51, and the plus-side of the ram. When the piston is forced inwards fluid will flow through the throttle valve 51, and part of the fluid will be stored in the accumulator 52.

When the davit has reached its maximum folding out position, and the capsule has been disengaged the load upon the davit is reduced. The fluid stored in the accumulator will then force the piston of the ram 48 outwardly, which means that the davit arm will be lifted somewhat. In its manner the risk of a collision between the davit and the free-floating capsule is reduced.

The modified embodiment 42b of a braking means shown in Figure 7 comprises basically the same components as in Figure 6, and the same reference numerals are used whenever possible.

The hydraulic circuit 49 here includes a hydraulic machine 53, operable as a pump, instead of the hydraulic ram 48. One end of wire 45 is attached to the davit, and is led over a number of sheaves 54-56 rotatable about stationary axes. The opposite end of the wire is wound upon a drum 57, which drives the pump 53 by way of a shaft 58.

When the davit folds out the drum 57 and the pump 53 will be rotated, and the flow of pumped fluid through the throttle valve 51 will determine the velocity of the davit movement. The accumulator 52 will act in the same manner as described in connection with the previous embodiment, i.e. when the capsule is released it will force fluid through the hydraulic machine 53, which then will act as a motor, rotating the drum 57 in a direction opposite to the previous un-winding movement.

The embodiments above described and shown in the drawings are to be regarded as examples only, and the components forming parts thereof may be varied in many ways within the scope of the appended claims.

The size of the capsules may be selected so it can receive 60 - 150 men. Normally the capsule should be dimensioned to take care of the full crew of the vessel, and preferably there are two capsules mounted in different places upon the vessel. The capsule may be partly recessed into the deck box structure, directly communicating with the interior thereof.

Claims (11)

1. A survival cabin for use at an offshore vessel and comprising a buoyant capsule, as well as a davit for normally carrying the capsule at least partly outside a side of the vessel and being accessible from the deck thereof, characterized in that the davit comprises an arm structure which is pivotably attached to the vessel at a considerable distance below its deck and carries the capsule at a single point, and that the davit is governed by a braking system which, when released, permits an unfolding of the davit to a position where the capsule reaches a maximum distance from the side of the vessel, and then automatically releases the capsule.

2. A survival cabin as claimed in claim 1,wherein the capsule is provided with dampening means permitting a free drop from considerable height.

3. A survival cabin as claimed in claim 2, wherein the dampening means comprises a space located outside a watertight bottom structure of the capsule, said space being defined by a bottom plating provided with a number of openings permitting the entrance of water.

4. A survival cabin as claimed in any one of the preceding claims, wherein the capsule is enclosed by a deformable fender of steel plate.

5. A survival cabin as claimed in any one of the preceding claims, wherein the above-water structure of the capsule is covered by a heat insulating layer.

6. A survival cabin as claimed in any one of the preceding claims, wherein the pivot of the arm structure is located that much below and inside of the center of gravity of the capsule, that an automatic lowering of the same is brought about as soon as the brake is released.

7. A survival cabin as claimed in claim 6, wherein the distal end of the arm structure is formed as a shallow hook, which carries the capsule is an open link.

8. A survival cabin as claimed in claim 7, wherein the link is mounted at the cabin by means of an explosive bolt, or other rapid-release device permitting manual actuation.

9. A survival cabin as claimed in any one of the preceding claims, comprising means connected to the braking system and adapted automatically to lift the arm structure as soon as the capsule is released.

10. A survival cabin as claimed in any one of the preceding claims, wherein the capsule is provided with a pulling azimuth propeller, as well as with an auto-pilot operating the same, and being programmable to steer the capsule in a desired direction away from the vessel.

11. A survival cabin for use at an offshore vessel substantially as hereinbefore described with reference to and as shown in the accompanying drawings.