US3796281A

US3796281A - Apparatus for use in escaping from high structures

Info

Publication number: US3796281A
Application number: US00283280A
Authority: US
Inventors: T Dowling
Original assignee: Mobell Marine Development Co Ltd; RFD Co Ltd
Current assignee: Mobell Marine Development Co Ltd; RFD Co Ltd
Priority date: 1971-08-26
Filing date: 1972-08-24
Publication date: 1974-03-12
Anticipated expiration: 1991-03-12

Abstract

Apparatus for use in escaping from a high structure at sea, the apparatus comprising a buoyant member which, when positioned under water, provides a source of potential energy, an outhaul cable, and bowsing brake means which are operative to retain the outhaul cable, against the influence of the buoyant member, in an inoperative position in which the outhaul cable passes into the sea beside the structure, release of the bowsing brake means causing the outhaul cable to be drawn by the buoyant member away from the structure for escape purposes.

Description

United States Patent 1 Dowling [451 Mar. 12, 1974 1 APPARATUS FOR USE IN ESCAPING FROM HIGH STRUCTURES Thomas Barrow Dowling, Emsworth, England [73] Assignees: RFD-GQ Limited, Surrey; Mobell Marine Development Company Limited, l-lavant, Hampshire, both of, England [22] Filed: Aug. 24, 1972 [21] App]. No.: 283,280

[75] Inventor:

[30] Foreign Application Priority Data Aug. 26, 1971 Great Britain 40133/71 Mar. 20, 1972 Great Britain 12827/72 s21 U.S. Cl 182/48, 182/191, 9/14 [51] Int. Cl. B636 9/22 [58] Field of Search 182/191, 192, 193, 189, 182/190, 230, 48, 50; 9/14 [56] References Cited UNITED STATES PATENTS 102,878 Street 9/14 276,090 4/1883 Sperry 182/50 829,179 8/1906 Stevens... 9/14 838,690 12/1906 Dalton 9/14 Primary Examiner-Reinaldo P. Machado Attorney, Agent, or FirmWatson, Cole, Grindle & Watson w [5 7] ABSTRACT Apparatus for use in escaping from a high structure at sea, the apparatus comprising a buoyant member which, when positioned under water, provides a source of potential energy, an outhaul cable, and bowsing brake means which are operative to retain the outhaul cable, against the influence of the buoyant member, in an inoperative position in which the outhaul cable passes into the sea beside the structure, release of the bowsing brake means causing the outhaul cable to be drawn by the buoyant member away from the structure for escape purposes.

16 Claims, 8 Drawing Figures PATENTED IIAR I 2 I974 SHEET 1 [IF 7 PATENIEB m 12 m4 SHEET 2 [IF 7 PAT-ENTEU IIAR l 2 I974 SHEET 7 OF 7 APPARATUS FOR USE IN ESCAPING FROM HIGH STRUCTURES This invention relates to apparatus for use in escaping from high structures at sea such as off-shore drilling rigs or terminals.

When it is wished to evacuate an off-shore drilling rig in emergency conditions the crew may man unpowered self-inflating (orrigid) escape craft and then, in theory at least, drift clear of the rig. However, in severe weather conditions, and particularly if the tide happens to be running against the wind, drifting clear may not always be possible.

An alternative means of escape sometimes used is the powered rigid craft which is manned on the rig and then lowered into thesea. However, such craft are expensive and, apart from the fact that their power may not be sufficient to take them clear of the rig in particularly severe weather or current conditions, they have the disadvantage that if lowered on the windward or up current side, they may be carried against or into the rig, suffering severe buffeting and perhaps damage with the risk of becoming trapped in the rig structure. It will be appreciated in this respect that it may not always be possible, say in the event of fire for example, to elect I to escape from the leeward or down current side of the rig.

In our co-pending Application No. 24407/69, now British patent No. 1,297,771, there is disclosed apparatus for use in escaping from a high structure at sea and employing a falling weight and a cable which extends downwardly and generally outwardly from the structure to remote anchoring means on the sea bed. It has been found that this arrangement is satisfactory in certain situations but that it is not always satisfactory where obstruction of the falling weight is difficult to overcome and where the evacuees must be moved quickly from the structure to a distance of about 250 feet to 400 feet therefrom. It is particularly desirable that escape can be made to a distance of this magnitude from gas or oil drilling rigs in which the danger of fire and explosion is always present. An object of the present invention is to provide escape apparatus in which evacuees can be moved a substantial distance away from the structure in cases of emergency.

According to one aspect of the invention, apparatus for use in escaping from a high structure comprises buoyant actuating means which, when positioned under water, provide a source of potential energy, an outhaul cable, and bowsing brake mans which are operative to retain the outhaul cable, against the influence of the buoyant actuating means, in an inoperative position in which the outhaul cable passes into the sea beside the structure, release of the bowsing brake means causing the outhaul cable to be drawn by the buoyant actuating means away from the structure for escape purposes. The term cable is to be construed herein as including rope.

Preferably, the buoyant actuating means comprise a buoyant member connected to a heavy clump of material for location on the sea bed at a point remote from the structure so that, on release of the bowsing brake, the submerged buoyant member rises toward the surface of the sea and draws the outhaul cable both upwardly and away from the structure. The outhaul cable may be a simple escapewire connected at respective ends to the structure and to the actuating means, or

may alternatively be in the form of a painter line secured to an escape craft which is initially lowered into the water by a separate lowering line which is automatically released when the craft reaches the water. The influence of the buoyant member draws the craft clear of the rig on descent and on release continues to draw it along the surface. The length of outhaul cable drawn in may be accommodated around blocks attached on the one hand to the clump and on the other hand to the buoyant member, the number of turns of the outhaul cable aroundthe blocks determining both the proportion of the buoyancy force which is available to draw in the outhaul cable and the velocity ratio between the drawing in movement of the outhaul cable and the movement of the buoyant member away from the clump. A further clump may be provided for positioning on the sea bed beyond the first-mentioned clump, a restraining line being used for interconnecting the buoyant member and the further clump so that the buoyant member executes an upward arcuate path about the further clump as center when the bowsing brake means are released.

The buoyant member may have a region filled with a foamed material, the region being disposed above a downwardly depending skirt which surrounds the associated operating block and which may be packed with light grease which inhibits the growth of weed and barnacles by virtue of its lubricating action when the apparatus is worked through. The skirt may have a slot through which the outhaul cable passes and also a guidance block around which the outhaul cable passes in its path between the slot and the actuating blocks.

According to another aspect of the invention, there is provided a high structure at sea associated with apparatus for escaping from thestructure, the apparatus comprising buoyant actuating means which are located under water at a point remote from the structure and which provide a source of potential energy, an outhaul cable, and bowsing brake means which are operative to retain the outhaul cable, against the influence of the buoyant actuating means, in an inoperative position in which the outhaul cable passes into the sea beside the structure, release of the bowsing brake means causing the outhaul cable to be drawn by the buoyant actuating means away from the structure for escape purposes.

The invention will now be further described with reference to the accompanying drawings which show, by way of example, five forms of apparatus in accordance with the invention and associated with off-shore drilling rigs. In the drawings:

FIG. 1 is a diagrammatic side elevation of the first form of apparatus, with the inoperative condition being shown in full lines and the operative condition in broken lines, and intermediate position being shown in dotted lines;

FIGS. 2 to 4 are views similar to that of FIG. 1, but respectively illustrating the second, third and fourth forms of apparatus;

FIG. 5 is a diagrammatic side elevation of the fifth form of apparatus, the inoperative condition being shown in full lines and a slackened condition in dotted lines;

FIGS. 6 and 7 are views, on an enlarged scale, of portions of FIG. 5; and

FIG. 8 is a view similar to that of FIG. 5, but showing the fifth form of apparatus at successive stages during operation.

In 'FIG. 1, the apparatus is shown mounted in position on one side of the drilling rig which comprises two vertically spaced horizontal platforms 1, la and an inclined stanchion 2 supported in the sea bed 3. The apparatus comprises a bowsing brake 4 mounted on the platform 1 and a bowsing cable 5 which passes around a block 6 ,rigidly'attached to the stanchion 2 below sea level. The end of the bowsing cable 5 remote from the brake 4 carries a running block 7 around which passes a metal outhaul cable forming a painter line 8. One end of the painter line 8 is secured to an escape craft 9 and chorage point on the clump 16 and the underside of the buoyant member- 12. The buoyant member l2 has a rigid outer'casing and is filled with an expanded foamed material so that in the inoperative position of the apparatus shown in .full lines in FIG. 1, upward movement of the member 12 is restrained by the bowsing brake 4 and bowsing cable 5.,It will be realized that the bowsing cable 5 retains the painter line 8 in a position against the drilling rig to prevent the painter line 8 becoming entangled with vessels and that in this position the line 8 enters the sea substantially vertically. I

In addition to being connected to the upper end of the painter line 8, the escape craft 9 is'also attached to a lowering line 11 by means ofwhich it can be lowered 'in a controlled manner on to the surface of the sea indicated at 18. When it is desired to utilize the apparatus to evacuate personnel from the rig, the'craft 9 is lowered on the surface of the sea (in the manner described in the aforementioned British patent) and the bowsing brake 4 is released, thus causing the bowsing cable 5 to run out under the lifting effect of'the buoyant member 12 which rises inv an arcuate path centered onthe' triangulated yoke 19 on the underside of the member l2, acts to prevent twisting between'the two blocks 10 andl3. i 1

In the remaining FIGS. 2 to 8, components similar to those of FIG. 1 have been given the same reference numerals. In the apparatus shown in FIG. 2, the action of the buoyant member 12 is supplemented by a hanging weight 20 attached to one end of the'painte'rline 8 which passes from the escape craft 9 around the bowsing block 7, around a block 22 attachedon the underside-of the buoyant member 12,- and thence around fixed

blocks

23, 24 and 25 secured to the rig. The buoyant member 12 ag'ain executes anarcuatepath about a fixed clump 16 by means of a restraining linel7 to the fully operative condition shown in broken lines in FIG/2. The apparatus shown in FIG- 2 is particularly suitable where the depth of water is too shallow to allow the buoyantmember 12 sufficient depth to operate satisfactorily in the manner of the apparatus ofFIG. 1. In each of the first andsecond forms of apparatus described, further escape c'raft9' can be secured to the painter line' 8' at'successive intervals (say 90' feet) so that'a series of escape craft are pulled 'out by" the buoyantmemberl2. I

FIG. 3 shows a simplified form of apparatus in which the bowsing block 7 normally restrains an outhaul cable in the form of an escape line 26 connected between a fixed point 27 high up on the rig and a heavy clump l5-located on the sea bed 3. When'the bowsing brake 4 is released, the escape line 26 moves tothe position shownin broken lines by'virtue of upward arcu ate movement of the buoyancy member 12, the re.

clump 16, the restraining line 17 acting in the manner of a radius arm during this, lifting movement. As the craft 9 descends, the tension resultingbfrom the influence of the submerged buoyant member 12 draws the craft 9 outwards from a vertical descent as indicated by the dotted line position in FIG. 1. Once floating, the lowering line .11 is automatically released from the craft 9, and the painter line 8 continues to draw the craft 9 away from the rig.

The length of painter line 8 taken inis accommodated between the two blocks 10 and 13 until, in the position indicated in broken lines, the escape craft 9 has been pulled by the line 8 to its maximum distance from the rig. This position of maximum displacement from the rig is defined either by restraint imposed by the bowsing brake 4, by the buoyant member 12 having reached a position of equilibrium or by a stop on the painter line 8 engaging the running'block 10. In the example shown in FIG. 1, there are three runs of the painter line 8 between the two blocks 10 and 13. It will be realized that the painter line 8 can be wound around the blocks 10 and 13 a greaternumber of times to give more runs in situations where the depth of water is less or where a smaller drawing-inforce on the painter line 8 is acceptable. The bar 14, together with a rigid.

straining line 17 again actingas a radius arm. The appa-' ratus of FIG. 4 enables lateconiers to'be evacuated by means of controlled descent devices andalso can be used to lower an inflatable liferaft. v

For certain deep sea situations it is envisaged that the apparatus of FIG. v4 might be useful. In FIG. 4, the painter line 8 extends downwardly from the escape craft 9, around the bowsing block 7 and is attached at a fixed point on the. stanchion 2. The bowsing block7 is connected by a short interconnecting line 28 to the underside of the buoyant memberl2 which is also connected'to a heavy clump (not shown)f-by means of the restraining line 17. On release of the bowling brake 4, the buoyant member 12 moves through the intermediate position'shown in dotted lines to the limit position shown in broken lines, the painter line 8 drawing the escape craft 9 outwardly from the rig along the surface of the water. I

In FIG. 5, the apparatus again comprises the bowsing brake (or'winch) 4 mounted on the lower platform 1 and a bowsing cable 5 which passes-around a block 6 rigidly attached tothe stanchion'2 below sea level. The end of the bowsing cable firemote from the brake 4 carries a running block .7 around which passes anouthaul cable 8. The cable- 5 may be of metal or may be in the form of a rope which provides more give or stretch and so reduces the forces imposed by strong cross tides on the block 6 and buoyant member 1-2. As shown more clearly in FIG 6, the lower platform 32 also carries a raftwinch 30 which controls a winch wire 32 passing over a running block 33 depending from the upper platform 1a. The wire 32 terminates in a connection 34 to which one end of the outhaul cable 8 is also attached. The connection 34 also provides the upper anchorage point of the lowering line 11, the lower end of which is attached to the inflatable escape craft 9 by means of a releasable hook 35.

A concrete clump (shown in detail in FIG. 7) is located on the sea bed 3 at a point remote from the rig, the clump 15 providing an anchorage for an actuating block 13, a further actuating block 10 being attached to the buoyant member 12 which provides a source of potential energy which is utilized to draw the craft 9 away from the rig when the apparatus is operative. The buoyant member 12 has a domed top and a downwardly diverging frusto-conical skirt 36 which terminates in a bell mouth 37. An upper region of the buoyant member 12 is filled with a foamed material 38 to provide buoyancy, light grease (or similar growth inhibiting liquid) 39 being packed into the buoyant member 12 below the foamed material 38. The skirt 36 is formed with a slot 40 through which the outhaul cable 8 passes in its passage to the actuating blocks 10 and 13, the member 12 incorporating a further guidance block 42 around which the outhaul cable 8 passes. The skirt 36 prevents sediment lodging in the blocks 10 and The apparatus is shown in its ready condition in full lines in FIG. 5 and in broken lines in FIG. 6. In this ready condition, the craft 9 is stowed in its uninflated state near the edge of the lower platform 1, the outhaul cable 8 passing downwardly in a substantially vertical direction beside the rig, being held by the running block 7 on the end of the bowsing cable 5. In this condition, the mouth 37 of the buoyant member 12 rests on the clump 15, as shown in FIG. 5.

When it is desired to evacuate the rig, the craft 9 is inflated and the bowsing brake 4 is released so that the outhaul cable 8 is drawn away from the rig as a result of the rising movement of the buoyant member 12, this condition being shown in fulllines in FIG. 6, in FIG. 7 and in full lines in FIG. 8. The raft winch 30 is then operated by lanyard from the craft to pay-out the winch wire 32 to cause the inflated craft 9 to be lowered on to the surface of the sea, as indicated in dotted lines in FIG. 8. The release book 35 is detached so as to separate the lowering line 11 from the craft 9 which is then drawn out along the surface of the sea in a direction away from the rig as the buoyant member 12 rises, the length of outhaul cable 8 taken in being accommodated around the two actuating blocks 10 and 13 as the latter move further apart.

FIG. 8 indicates, in broken lines, the general position of the components when the draft 9 has been drawn a distance of some three hundred feet from the rig by means of the buoyant member 12 which is shown floating on the surface. As the craft 9 is pulled away from the rig by means of the buoyant member 12,-the winch wire 32 is paid out and provides a controlled restraint which ensures that the craft 9 is drawn out at a steady controlled speed. As the apparatus is worked through between its respective limits represented by full lines in FIG. 5 and broken lines in FIG. 8, the light grease 39 accommodated within the buoyant member 12 is distributed along the outhaul cable 8, thereby inhibiting the growth of weed and barnacles. As the body of grease 39 is slightly buoyant, it is retained within the skirt 36 of the buoyant member 12. By passing the outhaul cable 8 around the actuating blocks 10 and 13, a mechanical advantage is achieved which can be increased by increasing the number of loops of the cable 8 around the actuating blocks 10 and 13.

When the apparatus is in the broken line position of FIG. 8, the winch wire 12 can be used as a descent line for latecomers. FIG. 5 shows, in dotted lines, how the apparatus can be eased into a slack condition, in which the outhaul cable 9 and winch wire 32 rest on the sea bed so that they do not represent an obstruction to derrick barge operations, for example.

An important advantage of each of the foregoing forms of apparatus is that the buoyant member 12 (supplemented by the weight 20 in the case of the apparatus of FIG. 2) acts to tension the whole system so that there are no slack lines which can become entangled. Also, the apparatus is less vulnerable to disaster damage because the actuating means (provided by the member 12) is removed from the rig. In each of the described forms of apparatus the craft 9 may be an enclosed escape shell or an open escape raft.

With these forms of apparatus, practice escape drill can be carried out so long as a recovery line is utilized where required, i.e., in the cases where the craft 9 is re- 7 leased and is thenceforward only connected to the painter line 8. Thus, once the recovery line has hauled in the painter line to the ready position, and the painter line has been reconnected to the craft, all that remains is for the bowsing winch (i.e., the brake 4) to be operated until the apparatus is bowsed in again.

WHAT IS CLAIMED IS:

1. Apparatus for use in escaping from a high structure at sea, the apparatus comprising buoyant actuating means which, when positioned under water, provide a source of potential energy, an outhaul cable, and bowsing brake means which. are operative to retain the outhaul cable, against the influence of the buoyant actuating means, in an inoperative position in which the outhaul cable passes into the sea beside the structure, release of the bowsing brake means causing the outhaul cable to be drawn by the buoyant actuating means away from the structure for escape purposes.

2. Apparatus according to claim 1, wherein the buoyant actuating means comprise a buoyant member which is less dense than water.

3. Apparatus according to claim 2, wherein the buoyant member is attached to a heavy clump of material for location on the sea bed at a point remote from the structure.

4. Apparatus according to claim 3, wherein the buoyant member carries a block and the clump carries a further block whereby the outhaul cable can be passed around the two bocks a chosen number of times in dependence upon the required mechanical advantage.

5. Apparatus according to claim 4, wherein the buoyant member has a domed top accommodating a foamed material which imparts buoyancy, and a flared skirt portion terminating in a lower flared mouth which rests upon the clump in the inoperative position.

6. Apparatus according to claim 5,.wherein the skirt portion is packed with grease which surrounds the block carried by the buoyant member.

7. Apparatus according to claim 3, wherein the clump is supplemented by a further clump of heavy material to the buoyant member and is arranged so that as the buoyant member rises, the buoyantmember executes an arcuate path centered on said further clump.

8. A high structure at sea associated with apparatus for escape from the structure, the apparatus comprising buoyant actuating means which are. located under water at a point remote from the structure and which provide a source of potential energy, an outhaul cable, and bowsing brake means which are operative to retain the outhaul cable, against the influence of the buoyant actuating means, in an inoperative position in which the outhaul cable passes into the sea beside the structure, release of the bowsing brake means causing the outhaul cable to be drawn by the buoyant actuating means away from the structure for escape purposes.

9. A high structure according to claim 8, wherein the buoyant actuating means comprise a buoyant member attached to a clump of heavy material position on the sea bed at said point remote from the structure, release of the bowsing brake means causing the buoyant member to rise from the clump and draw the outhaul cable to the operative position.

10. A high structure according to claim 9, wherein the outhaul cable passes around a block secured to the buoyant member, an end of the outhaul cable being anchored to the clump.

11. A high structure according to claim 10, wherein the outhaul cable passes around said block and a further block secured to the clump a desired number of time dependent on the required mechanical advantage.

12. A high structure according to claim 8, wherein the outhaul cable is a painter line secured to an escape craft.

13. A high structure according to claim 12, wherein the apparatus includes a winch wire which is connected to the escape craft and is paid out from the structure to provide a controlled restraint from the craft against the pull exerted by the painter line.

14. A high structure according to claim 9, wherein a further clump is located on the sea bed at a point further from the structure than the first-mentioned clump, the buoyant member being connected to the further clump by a restraining line which undergoes arcuate movement in the manner of a radius arm about the further clump as center as the buoyant member rises.

15. A high structure according to claim 8, wherein the outhaul cable is an escape wire connected at respective ends to the structure and to the actuating means.

16. A high structure according to claim 8, wherein the outhaul cable passes around a running block attached to the end of a bowsing cable of the bowsing brake means, the end of the outhaul cable being anchored to the structure and the running block being attached to the buoyant member.

Claims

1. Apparatus for use in escaping from a high structure at sea, the apparatus comprising buoyant actuating means which, when pOsitioned under water, provide a source of potential energy, an outhaul cable, and bowsing brake means which are operative to retain the outhaul cable, against the influence of the buoyant actuating means, in an inoperative position in which the outhaul cable passes into the sea beside the structure, release of the bowsing brake means causing the outhaul cable to be drawn by the buoyant actuating means away from the structure for escape purposes.

6. Apparatus according to claim 5, wherein the skirt portion is packed with grease which surrounds the block carried by the buoyant member.

8. A high structure at sea associated with apparatus for escape from the structure, the apparatus comprising buoyant actuating means which are located under water at a point remote from the structure and which provide a source of potential energy, an outhaul cable, and bowsing brake means which are operative to retain the outhaul cable, against the influence of the buoyant actuating means, in an inoperative position in which the outhaul cable passes into the sea beside the structure, release of the bowsing brake means causing the outhaul cable to be drawn by the buoyant actuating means away from the structure for escape purposes.