ESCAPE CHUTE
Background to the Invention
The invention relates to escape chutes .
The invention is particularly applicable to situations where there is a need for mass evacuation in an emergency from a multiple-occupancy work station such as an offshore oil- drilling rig . Recent well-publicised disasters in this field have highlighted the need , currently unfulfilled , to solve this problem . The conventional life rafts do not solve it and their drawbacks have again been graphically illustrated by the television and press coverage of (for example ) the
" Piper Alpha" rig explosion and its aftermath .
Summary of the Invention
In its broadest aspect the invention provides an escape chute assembly , intended for use as a mass evacuation unit through which a succession of workers can escape in an emergency from a multiple-occupancy work station (for example an offshore oil-drilling rig ) and comprising a linked succession of open- ended pipes ; each of which pipes is large enough internally for a worker to slide through ; and all of w hich pipes are so linked as to define , in use , an elongate open-ended tunnel down which the escapees slide , and from which the escapees exit , under the force of gravity ; the pipes being so shaped , sized and linked that in use ( a ) they fit one within another
to define a tunnel which has a substantially continuous interior , and ( b ) at least some of them articulate to allow the exit region of the tunnel to arch towards the horizontal .
Preferably the pipes telescope and the assembly incorporates or is used in conjunction with, a means (other than the pipe- linking njeans ) for telescoping them.
Advantageously the assembly may incorporate , or be designed to be used in conjunction with, means to vary the degree by which and/or the direction in which the exit region of the tunnel arches in use.
Where the assembly is incorporated into, or intended for use on, a multi-deck work station (for example an offshore oil-drilling rig ) then the in-use combination of work station and escape chute assembly preferably incorporates "between decks" interfitting-pipe tunnels each comprising a linked suc¬ cession of open-ended pipes and each intended for use as an emergency worker-escape unit to allow workers to reach the main escape chute assembly from the upper decks of the work station.
In the case just outlined , one (or more than one , if a plurality are provided ) of such between-decks tunnels may incorporate pipe sections which articulate to allow the exit region of the tunnel to be directed appropriately onto or adjacent a specified region of the work station.
Any escape chute assembly which embodies the invention and which is intended for use on a water-surrounded work station (again, by way of example , an offshore oil-drilling rig ) may incorporate buoyancy aiding means at or adjacent the exit region of the tunnel .
An assembly in the case just outlined may also incorporate trailing lines and /or individual floats which the escapees can grasp and cling to until they are rescued from the water .
Brief Description of the Drawings
The invention will now be described, by way of example only , with reference to the accompanying drawings , in which:
Figure 1 shows an escape chute assembly according to the invention, the chute being shown in an extended , "in use" condition;
Figure 2 is a more detailed view of part of the chute shown in figure 1 ;
Figure 3 shows a modified form of chute assembly , the chute being shown in a retracted condition;
Figure 4 is a side view of a rig (for example an offshore oil-drilling rig ) structure on which two escape chutes , each according to the invention, are mounted;
Figure 5 shows part of an escape chute assembly which incorp¬ orates "between decks" interfitting-pipe tunnels , each intended for use as an emergency worker-escape unit to allow workers to reach the main escape chute assembly from the upper decks of the work station;
Figure 6 shows an alternative mounting arrangement for an escape chute;
Figure 7 shows two escape chutes mounted on a supp- ort running between the two rig structures , the support com¬ prising a gantry and being mounted at each opposite end on the rig structures by known mounting means ;
Figures 8-10 show a buoyancy aid which may be used in conjun¬ ction with the escape chute; and
Figure 11 shows a life-raft buoyancy* aid .
Description of the Preferred Embodiment
The chute assembly shown in figure 1 is mounted on an access support platform 1 which is situated beneath the accommodation modules of a multiple occupancy work station for example , an offshore oil-drilling rig or . gas rig . The decking floor of the accommodation modules includes a trap door , which provides access from the accommodation modules to the platform
1.
The platform 1 includes a circular aperture, in which an open ended pipe 2 is mounted. The means mounting the pipe in the aperture are provided by an inwardly directed flange (known per se ) formed around the periphery of the aperture, and a ring ( known) • - which is supported on the flange, and is so sized and shaped as to be rotatably mounted within the aperture. The ring includes two diametrically opposed lugs 3 , in each of which a hole 4 is formed . Two diametrically opposed bosses 5 project radially outward from a flange 6 formed in the top of the pipe 2 , each boss 5 fitting within one hole 4.
The arrangement is such that the pipe 2 is mounted within the aperture of the platform 1 via a "gimbal-type" mounting which allows the pipe 2 to pivot within the aperture in any direction with a limited degree of articulation.
Referring to figure 2 , which shows a portion of the pipe
2 beneath the flange 6 , the pipe 2 includes a central flange
7 , and is tapered from top to bottom . The shape of the pipe 2 is such that the pipe 2 is a telescoping fit within the
first of a succession of open ended pipes 8. A flange 9 is formed in the top end region of each pipe 8 , and each pipe 8 tapers from top to bottom in such a way as to enable adjac¬ ent pipes 8 to telescope together .
The pipe 2 and the pipes 8 are large enough internally for a worker to slide through . Thus, with the chute assembly extended in the way shown in figure 1 , the pipe 2 and the pipes 8 define an elongate tunnel down which , in use , escapees slide . The tube 2 and each of the tubes 8 is formed as a fibreglass moulding comprising alternating layers of fibreglass and a suitable fire resistant laminating resin, for example a resin confirming to BS 476 Part 7 1971. Such a resin is currently sold in the UK under the trading style NORPOL 84- 73 by Jotun Polymer . Each flange 9 is formed by moulding the fibreglass of its respective pipe 8 around a steel band, one of which is shown as a detail on figure 1. The flanges 6 and 7 are formed in a similar way.
The steel bands provide extra structural rigidity for the pipes , and also provide mounting points for a number of attach- ments which project from the steel bands , but are not en¬ cased in the fibreglass of the pipes .
Two such attachments for the pipes 8 are a pair of double eyelets 10 which provide mounting points for two chains 11 or 12 which link together adjacent pipes 8. In figure 1 , the chains 11 and 12 are shown as a series of individual lengths, each length linking an adjacent pair of pipes . Alternatively , the chains 11 and 12 could be formed as two continuous lengths of chain, each linking all of the pipes 8. The chain 11 links the first of the pipes 8 to the pipe 2 in a similar way .
The flange 7 , and each flange 9 , also includes a second pair of attachments 13 which are diametrically opposed , and each of which defines a conduit .
A cable 14 is wound around a winch 15 mounted on the platform 1 , and passes over a pulley 16 and through the conduits defined by the attachments 13 on one side of the chute assembly, the attachments 13 acting as cable runners . One end of the cable 14 is secured to a lug 17 formed on a exit pipe 18 which fits telescopically over the lowest of the succession of pipes 8. A second length of cable runs along the opposite side of the assembly in the same way.
The pipes 2 , 8 and 18 are so shaped as to permit a certain degree of relative articulation between two adjacent pipes, the combined effects of which articulation is to enable the exit region - -of the tunnel , the region adjacent the tube 18 , to be curved towards the horizontal . Two buoyancy floats 19 are mounted on the underside of the exit tube 18, and where the chute is to be used on, for example , an offshore drilling rig, serve to support the exit tube 18 on the water surface. The floats 19 thus serve to maintain the curved shape of the tunnel , and help the exit tube 18 to follow the move¬ ment of the water surface in heavy seas ; as does the articu¬ lation. The top of the exit tube 18 stops short of the bottom so as to define a lower lip 20 on the tube 18. This arrangement makes it easier for an evacuee to pull himself out of the end of the exit tube 18 by gripping its side walls , whilst the lip 20 provides some support for escapees already in the water .
The chute assembly can be retracted by operating the winch 15 to reel in the cables 14, pulling the exit pipe 18 towards the pipe 2 , and thus causing adjacent pipes to telescope tog¬ ether . The winch 15 may be manually operated using a system of handles and gears as known . Alternatively , the winch
15 may be an electrically , hydraulically or pneumatically operated winch .
The winch 15 includes a locking mechanism (. known ) for maintaining the chute assembly in a retracted condition (figure 3 ) . The winch 15 also includes a release mechanism ( known ) which is operable to launch the chute from a retracted into an extended condition. Operation of the release mechanism causes the winch 15 to free— wheel as the pipes 8 and 18 drop under the influence of gravity, unwinding the cables 14 in the process .
A protective cowl 21 is mounted above the aperture in the platform 1. The cowl 21 serves to protect the mounting means for the pipe 2 against the elements , and may facilitate location of the aperture in the platform 1 in any emergency.
The chute assembly shown in figure 3 differs from that shown in figure 1 in that there are no buoyancy floats on the exit pipe 18. In this case, the means arching the exit region of the tunnel towards the horizontal are provided by a cable 22 which is attached to the pipe 18 via linking cables 23. The cable 22 is wound around a tension drum 24 which with the chute assembly in an extended condition, appropriately tensions the cable 22 causing it to pull the exit pipe 18 in to the position corresponding to the required shape of the exit region of the tunnel . The tension drum 24 may be movably mounted on the platform 1 in such a way that the degree by which and/or the direction in which the exit region of the tunnel arch is in use may be varied by appropriately moving the tension drum on the platform 1 .
The chute assemblies shown in figure 4 also use cables to maintain the required arch shapes of the exit region of their respective tunnels . In these case , however , the cable is direct- ly anchored to a fixed structure, and a waterproof sleeve 8A surrounds the pipes constituting the exit region, corrugating as necessary w hen the tunnel is winched up .
It should also be noted that the upper pipes of each of these chute assemblies are longer than the pipes positioned near¬ er the exit pipe . Consequently, the portion of the chute defin¬ ed by the upper pipes is relatively inflexible , enabling the chute to be held clear of the rig structure , whilst the portion of the chute defined by the lower pipes is relatively flexible allowing the desired degree of curvature of the exit region of the tunnel to be obtained .
Another way of supporting the tunnel in the required shape is to pivotally connect a rigid boom to one of the pipes near the exit region of the tunnel , and to part of the rig structure .
Referring to figure 5 , where the chute assembly is to be used on a work station having a plurality of levels , a number of curved pipes 25 may be provided, each pipe 25 having an entrance 26 and an exit end 27. Each pipe 25 defines a
"between decks" interfitting pipe tunnel through which an escapee may access a level from the deck on the level above. Thus , by travelling through the tubes 25 in succession, escapees can access the platform 1 , and hence the chute, from the higher levels . Alternatively, the "between decks" interfitting pipe tunnels may be defined by a linked succession of open ended pipes similar to the pipes 8, wholly or partially tele¬ scoping , and variable in curvature and/or direction, like the main chute . The "between decks" interfitting pipe tunnels may also be used to evacuate workers from one part of a work station, for example a hellideck, to a safer part of the work station.
Figure 6 shows part of a chute assembly which is adapted to be installed in situations where available space is severely limited . In this case , the winch for the cables 14 has been replaced by two underslung winches 28 , which occupy less above deck space than the winch 15 , and are in fact wholly below -deck .
The inner surfaces of the pipes 2 , 8 , and 18 are smooth , reducing the chances of descending escapees sustaining friction burns on contact with those inner surfaces . However , the inner surfaces may include rubber strips so positioned as to enable a descending escapee to control his rate of descent . The prob¬ lems of friction burns may be further reduced by directing a cascade of water down the inner surfaces.
Figure 7 illustrates chute assemblies mounted between two offshore work stations . In each case , the exit pipe 18 is equipped with a set of trailing floats 30 and an inflatable raft 31, both of which inflate automatically on contact with the water . The chute-carrying gantry is referenced 3QA
The chute assemblies may also be equipped with flares which fire when the assemblies are launched into their extended conditions , and which facilitate location of the exit pipes
18 by rescue services .
The chute assemblies may be required to be used in many instances where all the power supplies on the work stations have failed . The pipes may therefore include a set of photo- luminescent strips on their outer surfaces which also aid in the location of the exit pipe by rescue services .
The buoyancy aids shown in figures 8 , 9 and 10 may be provided in a magazine of suitable kind (not shown) .. mounted beside the entrance to the chute assembly . These buoyancy aids may be used by escapees who have not had time to strap on a normal life jacket . As well as providing support in the water , the buoyancy aids may be used as mats by the escapees to control their rate of descent down the tunnel of the chute assembly.
The aids incorporate the straps enabling them to be tied tog¬ ether (figure 9 ) , and lifting points which allow them to be used as a lifting harness for lifting an escapee from the
water into, for example, a rescue helicopter .
Figures 11 A, 11B and 11C show an arrangement in which a life-raft 32 is fixed to the exit pipe 18 of the escape chute . The raft 32 comprises two preformed . glassf ibre reinforced shells 32A and 32B hinging about a common axis 33. The shells are mirror images about this axis and they come together , as shown, to embrace the end of the exit pipe 18 and to lock releaseably to the pipe by means which are known in • themselves .
Initially, as Figure 11A shows, the raft is locked firmly to the end of pipe 18 and descends with it when the chute as a whole is released . The raft 32 then floats on the water until the first of the escaping workers comes down the chute, through pipe 18 , and is automatically deposited inside the raft 32. He then releases the locking mechanism which allows shell 32A to spring open away from shell 32B about hinge 33 (Figure 11B ) whilst still retaining shell 32B on pipe 18.
When shell 32A has fully opened about hinge 33 ( Figure 11C ) there is defined an elongate life-raft which is configured as a hull with a keel and which is essentially open-topped .
Up to a dozen men, for example , can be accommodated in this raft and an inflatable canopy 34 subsequently raised .
When the raft is full , the means which still lock shell 32B to the end of pipe 18 can be released and the raft is then free to function as a lift-raft independently of the escape chute .
The raft may be a simple drifting hull or it may incorporate means of self-propullsion.
Finally Figures 11D and HE show another form of the inven¬ tion in which a buoyancy aid is attached to the exit pipe 18 of the escape chute . This time the buoyancy aid comprises a preformed glassfibre reinforced plastics pod 35 which , like the life-raft 32 of Figures 11A to 11C , consists of several sections hinged to one another .
A main one of these sections is referenced 36 and embraces the lower half of the pipe 18. It may be formed integrally with the pipe or it may be releaseably secured to it by known means .
Secondary sections 37 and 38 are each hinged to the sides of the main section 36 of the pod 35. When the pod hits the water after the escape chute has been released, the secondary sections 37 and 38 automatically open, hinging about the res- pectively opposite sides of the main pod section 36 as shown in Figure HE to release a flexible self-inflating bag pontoon 39.
The pontoon 39 is so configured as to act as an inflated raft for workers escaping via the chute and exiting the pipe 18 i-nto the raft . The inflated raft 39 can then stay where it is , or alternatively , be released by releasing the main pod section 36 from the pipe 18 via known quick-release means to allow the raft 39 to float away from the escape chute . In that latter instance the pod sections 36 , 37 and 38 may remain attached to the raft or they may be readily releaseable from it if not needed as an inherent part of the stability of the raft itself .