WO1990008691A1

WO1990008691A1 - Buoyancy and stability apparatus

Info

Publication number: WO1990008691A1
Application number: PCT/GB1990/000127
Authority: WO
Inventors: Michael Charles Short
Original assignee: Seabass (Gb) Limited
Priority date: 1989-01-30
Filing date: 1990-01-26
Publication date: 1990-08-09
Also published as: AU5027290A; GB8901989D0; GB2228902A; GB9001848D0

Abstract

Buoyancy and stability apparatus for a ship, comprising at least one inflatable buoyancy bag (22) associated or associable with the hull (1) of a ship and at least partially housed or housable within a cover (23) which, in use of the apparatus, is movable from a closed, bag-housing position as a consequence of at least partial inflation of said least one bag (22) to permit total inflation thereof.

Description

BUOYANCY AND STABILITY APPARATUS DESCRIPTION

This invention relates to buoyancy and stability apparatus for ships, boats, yachts, helicopters or other vessels or craft, hereinafter collectively re- ferred to as "ships", whereby the fuselage of a heli¬ copter or the main body structure of another vessel or craft will be referred to as a "hull" as in the regular case for a ship, boat or yacht.

One of the main aims of the present invention is to provide buoyancy apparatus capable of enabling a leaking or unstable ship to be brought to safety, for instance, into harbour, without sinking, another object of the invention being to provide stability apparatus both to arrest the capsize of a ship and to enable the stability of a ship to be restored or maintained in adverse weather conditions.

In our Patent No. 2184401 there is disclosed and claimed buoyancy and stability apparatus for a ship comprising inflatable buoyancy bags which, when in¬ flated, are disposed outboard of the hull of the ship and which are gas inflatable, under emergency con¬ ditions, using valves whose working dimensions are optimised to minimise the inflation time and change in gas temperature on expansion of the gas through the valves into the bags.

In emergency situations at sea, particularly where the capsizing of a ship is imminent, speed in inflating the buoyancy bags is of the essence. Known marine apparatus for providing and maintaining buoyancy and/or stability of a ship using, say, inflatable bags , take significantly longer than the time taken for a ship to capsize for such bags to become inflated. Thus , such known apparatus cannot inflate quickly enough to prevent capsize of the ship.

The buoyancy and stability apparatus described and claimed in our above-mentioned patent, enables the buoyancy bags to be inflated within seconds , rather than minutes, thereby substantially reducing the in¬ flation time down to, say, under 2 seconds, thereby preventing capsize which can occur under certain con- ditions , in less than 20 seconds.

In an embodiment described in that patent, the uninflated buoyancy bags are located within recesses in the outboard side of the hull of a ship which are closed by a protective cover substantially flush with the hull and secured thereto by suitable quick release means.

Such quick release means may comprise explosive bolts which are activated either manually or auto¬ matically immediately prior to inflation of the buoy¬ ancy bags. Such an arrangement can be quite cumber¬ some, in that it represents a further system which has to be actuated before the cover is detached from the hull and the buoyancy bags can be inflated.

Further, such an arrangement is expensive to provide and requires maintenance and servicing, thereby in¬ creasing the associated costs involved.

it is an object of the present invention to over¬ come, or at least substantially reduce, the disadvan¬ tages associated with the known buoyancy and stability apparatii discussed above.

Accordingly, one aspect of the invention provides buoyancy and stability apparatus for a ship (as herein¬ before defined), comprising at least one inflatable buoyancy bag associated or associable with the hull of the ship and at least partially housed or housable within a cover which, in use of the apparatus, is movable from a closed, bag-housing position as a conse¬ quence of at least partial inflation of said at least one bag to permit total inflation thereof.

Preferably, the cover for the or each inflatable bag is substantially rigid but is capable of flexing to a certain degree when a sufficiently large force is applied thereto. A suitable material for this purpose is a substantially rigid plastics material, such as, a glass or ara id fibre reinforced plastics material, or any other suitable material, moulded to the required shape for the cover, depending upon the shape of the ship with which the buoyancy and stability apparatus is associated. In this manner, when the buoyancy bag is rapidly inflated within, say, 2 seconds, using helium gas, the outward force exerted upon the cover by such inflation is sufficient to flex the cover to release it from associated mount¬ ing means on the ship's hull, such that it can move from its closed, bag-housing position, as will be described in more detail hereinbelow, thereby allowing full inflation of the buoyancy bag(s).

In an alternative embodiment, the cover may be releasably secured to the associated mounting means by shear bolts which, when sufficient force is applied to the cover upon rapid inflation of the buoyancy bag, the bolts shear and the cover is immediately released from the ship's hull, to permit the bags to inflate completely. The cover may be completely released from the associated hull or pivoted about say, hinges, in being moved from its closed to an open position as a consequence of at least partial bag inflation. Further, such release, pivoting or other movement from the closed position of the cover may be commenced by initial, partial inflation of the bag, in that the bag is arranged to actuate, say, means for causing or permitting the cover to move from its closed position. Such means may comprise explosive bolts , or other releasable securing means , which are actuable as a consequence of at least partial inflation of the bag(s) to cause release of the cover and consequential movement thereof from its closed position.

In a preferred embodiment of the inventive ap- paratus, a plurality of inflatable buoyancy bags are disposed on each side of the hull of the ship, at predetermined positions. Each bag is provided with one or more outer elongate webs which are clamped between specially designed, elongate clamping aws, preferably serrated, which, in turn, are attachable to a frame work secured to the hull outboard thereof by any suitable means.

Each bag is also provided with at least one gas inlet which is communicable, via a suitable valve, to a reservoir, preferably situated inboard the hull, wherein gas, for instance, helium, for inflating the bag is stored at a high pressure, in this case, up to 25,000 p.s.i., which pressure enables the buoyancy bag to be inflated extremely rapidly in less than 2 seconds and, in certain circumstances, in 0.6 seconds or less.

Another aspect of the invention provides an in- flatable buoyancy bag constructed from a plurality of panels of a flexible plastics material, wherein the edges of each panel are secured to the same inner or outer edge surfaces of adjacent panels.

In order that the invention may be more fully understood, embodiments of buoyancy and stability apparatus in accordance therewith will now be described by way of example and with reference to the accompany- ing drawings in which:

Figure 1 is a side elevation of a framework to which an inflatable buoyancy bag can be secured;

Figures 2A and 2B are respective side and front end elevations of an elongate, serrated clamping jaw for the buoyancy bag;

Figures 3A, 3B and 3C are respective side and front elevations of another elongate, serrated clamping jaw for the inflatable buoyancy bag;

Figure 4 is a side elevation, in section, of the buoyancy and stability apparatus attached to the hull of a ship;

Figures 5 and 6 are respective rear and end ele¬ vations, the latter being in section, of the buoyancy bag, when inflated;

Figures 7A and 7B are respective side and partial views of a cover of the apparatus;

Figure 8 is a plan view of a ship with 9 inflatable buoyancy bags associated therewith; Figure 9 is a side elevation of the view of the ship shown in Figure 8;

Figure 10 is a graph of respective righting lever curves for intact stability for a ship fitting with and without the inventive apparatus; and

Figure 11 is a graph of respective righting lever curves for damage stability for a ship fitting with and without the inventive apparatus.

Referring firstly to Figures 1 to 4 of the accom¬ panying drawings , secured to the outboard of the hull 1 (Figure 4) of a ship with which the inventive buoy- ancy and stability apparatus is associated, is a gen¬ erally rectangular framework to (Figure 1) comprising two, longer horizontal upper and lower members, 3, 4 and two, shorter vertical members 5, 6. As the framework 2, these four members 3 to 6 are secured in any suitable manner, for instance, by welding, to the outboard of the ship's hull 1 in a desired position with respect thereto, with the horizontal members 3, 4 extending in the fore and aft direction of the ship at or adjacent the waterline thereof. The framework members 3 to 6, as well as any components associated therewith, are made of steel, aluminium alloy or any other suitable strong material, preferably galvanised or otherwise salt water corrosion protected.

The horizontal and vertical members 3 to 6 of the framework 2 are each provided with outwardly ex¬ tending, threaded stubds 7 receivable in correspon¬ dingly-spaced, circular holes 8 in an elongate clamp¬ ing jaw 9 (Figures 2a and 2B) whose clamping surface 10 is serrated longitudinally. Associable with the clamping jaw 9 is another elongate clamping jaw 11 (Figures 3A to 3C) whose clamping surface .12 is also serrated longitudinally. Through holes 13 in the other clamping jaw 11 are arranged to register with respective through holes 8 in the first-mentioned clamping- jaw 9, when the two jaws 9, 11 are secured together by means of nuts 14 (Figure 4) threaded on to respective threaded studs 7 of the framework members 3 to 6 and correspond- ing in-register holes 15, 16 (Figures 2A, 2B and Fig¬ ures 3A to 3C) and an associated retaining screw 17 the former hole 15 being suitably threaded.

The material from which the elongate clamping jaws 9, 11, and associated components, are manufac¬ tured is marine grade aluminium alloy suitably heat treated and salt sealed to prevent, or at least sub¬ stantially reduce, corrosion thereof.

Between the clamping jaws 9, 11 is clamped a web 21 of an inflatable buoyancy bag 22 (Figure 4) disposed adjacent the ship's hull 1 in an uninflated condition and housed within a cover 23.

This cover 23 is substantially rigid, having been moulded from a glass or arimid reinforced plastics material and is of a shape suitable for the working environment of the ship, in this case, generally rec¬ tangular. Also, it is profiled, such that, when it is secured in position, as shown in Figure 4, it pre¬ sents a hydrodynamic outer configuration.

At least one end of the cover 23, and preferably at the forward end thereof, may be a deflector (not shown) which enhances the streamline effect of the hydrodynamic profile of the cover 23. Such a deflec- tor(s) may either remain in position after inflation of the bag 22, in which case, it is secured to the hull 1, or be jettisoned with the cover 23 at such inflation.

The clamping jaw 11, on the outer surface thereof, is provided with a downwardly inclined projection 18 having a generally U-shaped slot 19 extending along the lower free edge thereof. Into this slot, along all four sides of the framework 2, are fitting the respective edges 24 of the streamlined plastics cover 23, a resilient bead 25 being located between those edges 24 and the closed, upper end of the slot 19, as shown in Figure 4. In one embodiment, the edges 24 of the cover 23 are effectively a snap-fit into the respective slots 19. However, in another embodi¬ ment, the cover edges 24 are provided with U-shaped recesses 26 which are alignable with corresponding screw holes 20 provided in the effective side arms of the U-shaped slot 19 in the downwardly inclined projection 18 of the clamping jaw 11, as shown in Figures 3A to 3C and Figure 7B. The associated bolts are not shown in the drawings.

In this other embodiment, an associated locating collar (also not shown) may be provided for each bolt, whereby the arrangement is such that, in use, the bolt/collar combination with the slot 19 and holes 20 is sufficient to absorb shocks or other loadings which may otherwise tend to cause longitudinal movement of the cover- 23.

Attached to the inflatable buoyancy bag 23 is at least one gas inlet 27 (only one shown) which is secured to the ship's hull 1 by means of a flange/ clamping ring/flange nut arrangement indicated generally at 28 in Figure 4. The gas inlet(s) 27 of each bag 23 is/are connected to an associated high pressure gas cylinder 29 via suitable high pressure piping

30, as shown in Figure 8. A control system for the associated valves of the high pressure gas cylinders comprises another gas bottle, guage and interlocked operating valve arrangement indicated generally at

31, which is connected to a multi-branch, in this case a 10-branch, manifold 32 connected, in turn, to each of the high pressure gas cylinder valves 33 via suitable piping 34. The respective internal working diameters of the piping 30 and gas inlet 27, as well as the float or nozzle dimensions of the high pressure gas cylinder valves 33, are such as to minimise the buoyancy bag inflation times and the associated change in gas pressure upon expansion of the gas during bag inflation. Also, these components 27, 29, 30 and 33 are manufactured to withstand very high pressures of, say, -up to 25,000 p.s.i., namely, the pressure required to inflate the buoyancy bags 23 in an emer¬ gency situation in, say, less than 2 seconds.

The valves 33 may be controlled to close when the pressures in the buoyancy bags 23 reach a predeter¬ mined value, thereby leaving excess gas in the cylinders 29 at a higher pressure than that in the bags. Alter¬ natively, the valves 33 may be controlled such that the gas can be effectively "dumped" into the buoyancy bags 23 during rapid inflation thereof, to equalise the pressures in the cylinders 29 and bags 23 at full inflation of the latter. Construction of the buoyancy bags 22 is important, in that it has been found that loss of pressure from an inflated bag is reduced substantially by ensuring that edges of one panel strip 22" from which the bag 22 is formed, are attached by, say, adhesive, welding, stitching or any other suitable means, to the same outer or inner edge surface of adjacent panel strips 22" (Figure 6).

In operation, the buoyancy and stability apparatus is actuated by the control system 31 (Figure 8) which is operable by any suitable ^"means , either automatically or manually. An automatic arrangement may comprise an inclinometer, float or other suitable type of switch operably connected to the control system 31. It is possible to have several such activation means distri¬ buted around various parts of the ship, so that any one may be used the activate the apparatus.

Also, it is possible for the inventive apparatus to be computer controlled being connected to suitable sensors which may comprise inclinometer switches and which detect, for example, the height of the ship in the water, rolling and pitching of the ship and ingress of water and permanent list. The computer may be programmed to activate the apparatus when an emergency condition prevails and may be fitted with a manual override, so that the computer may be over¬ ridden to stop activation of the apparatus, in the event of computer malfunction or a non-detected emer¬ gency.

The overall design of the buoyancy and stability apparatus is such ^"as to interfere as little as possible with the normal running and handling of the ship with which it is associated, when the apparatus is not in use.

Whilst the invention has been described parti- cularly in its application to sea-going ships, it is possible for it also to be applied to aircraft, particularly helicopters which may be ditched in the sea, or to land vehicles such as military vehicles, in respect of which there may be a requirement to cross a stretch of water. A further, important, appli¬ cation of the inventive buoyancy and stability appartus is in relation to roll-on/roll-off ferries where capsize times can be extremely short and, under certain cir¬ cumstances, less than one minute.

Once the apparatus has been activated, the buoy¬ ancy bags 22 are inflated to their full volume as shown in dashed lines in Figures 8 and 9.

Tests carried out upon a tender of 131 tons dis¬ placement using the inventive buoyancy and stability apparatus , as shown in Figures 8 and 9 , have shown significant increases in the vessel's capability to comply with the intact and damage stability criteria set down by the Ministry of Defence standards. Also, the tender vessel's initial stiffness was increased significantly when the inventive apparatus was fitted to it and this, coupled with the additional buoyancy provided, greatly enhanced the available righting energy and ensured ready compliance with GZ area cri¬ teria.

In the apparatus tested, eight inflatable buoyancy bags 22, namely, four each side were used, which in- flated, in unison and substantially instantaneously, that is to say, within two seconds, on port and star¬ board sides of the essel's hull 1.

Additionally, destruction or damage to any given buoy¬ ancy bag 22 did not affect the other bags which remained inflated.

A further important effect of the invention ap¬ paratus observed during the tests was that the signifi¬ cant increase in initial stiffness increased the trans- verse metacentric height to more than six times greater than that without the apparatus fitted to the vessel, due mainly to a two to three times increase in meta¬ centric radius resulting from additional waterplane area. This high initial stiffness coupled with the additional buoyancy resulted in a significant increase in the available righting energy, for example, three to four times greater up to 40 degrees and it was also noticed that such stiffness reduced significantly the heel induced by wind loading, for example, from 5.75° to .97° in a 70 knot wind, or any other applied heeling moment. A comparison of the resulting righting lever curve with the inventive apparatus fitted to the vessel against the curve for the vessel without the apparatus fitted is illustrated in the graph of Figure 10, in respect of intact stability.

As far as damage stability is concerned, the tests revealed an extremely large increase in residual area with the apparatus fitted to the vesseel, such increase being in the order of forty times that without the apparatus. Further, the effect of wind induced loading on heel was observed to be negligible.

The resulting residual righting lever curves for the vessel with and without the inventive apparatus fitted thereto are illustrated in the graph shown in Figure 11, in respect of damage stability.

Righting lever values ^' increase proportionally with the rise in the percentage of reserve buoyancy supplied or available.

Thus, in Figure 10, the curve A represents the righting lever curve for intact stability of the vessel when fitted with the inventive buoyancy and stability apparatus , whereas the curve B represents such a curve for the vessel to which the apparatus is not fitted.

Similarly, Figure 11 shows the righting lever curves for damage stability of the vessel, wherein curve X is that for the vessel fitted with the inventive apparatus and with the total number of buoyancy bags inflated, curve Y is that for the vessel also fitted with the apparatus but only a partial number of the buoyancy bags inflated and curve Z is that for the vessel not fitted with the apparatus at all.

Thus, it can be seen that the buoyany and stability apparatus of the present invention provides a signifi- cant increase in buoyancy and stability of a ship under emergency conditions of list and possible capsize and damage.

Also, the apparatus in accordance with the in- vention may be supplied in kit form, in which case, the framework members 3 to 6 are secured intially to the hull 1 and the remaining apparatus components, which have previously been assembled together, are then offered up to the framework and secured thereto, as a unitary structure. Further, the inflatable buoyancy bags 22 may be arranged in, say, rows which are located at different levels with respect to the bags and/or rows positioned one above the other. This arrangement, which is espe- cially useful for larger ships, provides a prgressive application of the righting lever, albeit within seconds thereby avoiding a sudden and immediate application of such lever to the ship's hull 1.

It is to be understood that various modifications may be made to the invention, as described above without departing from its scope, as defined in the appendant claims.

As indicated above, and although the preferred embodiment described above in relation to the accompany¬ ing drawings employs a "snap-off" cover which is re¬ leased completely from the vessel's hull as a conse¬ quence of bag inflation, the cover may be connected to the hull in other ways, such as, by hinges, whereby it can pivot from its closed to its open position. Also, the inflatable bags may be deflated after use and, thereby, returnable to their ready states within the cover which would, in such an arrangement, be returnable to its closed position, for subsequent use.

Furthermore, the bag(s) may be arranged to actuate suitable means, such as, a switch, for causing or permitting the cover(s) to move from its/their closed position to open position as a consequence of at least partial bag inflation. An alternative may be the use of bag-actuable bolts, such as, explosive bolts, which are actuated by at least partial bag inflation to permit the buoyancy bag(s) to move from closed to open position(s).

Claims

1. Buoyancy and stability apparatus for a ship (as hereinbefore defined), comprising at least one in¬ flatable buoyancy bag associated or associable with the hull of a ship and at least partially housed or housable within a cover which, in use of the apparatus, is movable from a closed, bag-housing position as a consequence of at least partial inflation of said at least one bag to permit total inflation thereof.

2. Apparatus according to claim 1, wherein the cover is releasably secured or securable to the associated hull of a ship such that it is completely releasable therefrom on movement from its closed position.

3. Apparatus according to claim 1, wherein the cover is pivotably movable with respect to the associated hull of a ship from its closed position.

4. Apparatus according to claim 2 or 3, wherein the cover is sufficiently rigid to retain itself in its closed position but is sufficiently flexible that, when a sufficient force is applied thereto by said at least partially inflated bag during inflation thereof, the cover is movable from its closed position.

5. Apparatus according to claim 2 or 3, wherein the cover is retained or retainable in its closed position by shear bolts such that, when a sufficient force is applied thereto as a consequence of at least partial inflation of the bag, the bolts are sheared to permit movement of the cover from its closed posi¬ tion.

6. Apparatus according to claim 2 or 3, wherein the cover is retained or retainable in its closed position by explosive bolts which are actuable as a consequence of at least partial inflation of the bag to permit movement of the cover from its closed position.

7. Apparatus according to claim 6, wherein the ex¬ plosive bolts are actuable by switch means operable as a consequence of at least partial inflation of the bag.

8. Apparatus according to any preceding claim, wherein the cover is secured or securable to the asso¬ ciated hull of a ship by means of a framework attached or attachable thereto.

9. Apparatus accordingly to claim 8, wherein the framework includes at least one pair of clamping jaws between which an exterior web portion of said at least one inflatable buoyancy bag is clamped or clampable.

10. Apparatus according to claim 9, wherein the clamp¬ ing jaws are elongate and serrated longitudinally.

11. Apparatus according to claim 8, 9 or 10, when dependent on claim 4, wherein at least one edge of the cover is a snap-fit into a corresponding slot provided in the framework, such that, when a sufficient force is applied to the cover by said at least partially inflated bag during inflation thereof, the cover flexes to cause said at least one edge thereof to be released from the slot, so that the cover can move from its closed position.

12. Apparatus according to any preceding claim, wherein said at least one buoyancy bag is inflatable from a high pressure gas cylinder.

13. Apparatus according to claim 12, wherein said at least one buoyancy bag is connected to the high pressure gas cylinder via a valve and piping whose working dimensions are such as to minimise the bag inflation time and the associated change in gas pressure upon expansion of the inflating gas during bag in- flation.

14. Apparatus according to claim 12 or 13, wherein the components of the bag inflation arrangement are capable of withstanding pressures of up to 25,000 p.s.i.

15. Apparatus according to claim 12, 13 or 14, wherein the inflating gas is arranged to be "dumped" from the cylinder into the bag during rapid inflation thereof, to equalise the pressures in the cylinder and bag at full inflation thereof.

16. Apparatus according to any preceding claim, where¬ in the bag inflation time is less than 2 seconds.

17. Apparatus according to any preceding claim, wherein said at least one buoyancy bag is constructed from panel strips, with the edge of each panel strip attached to the same outer or inner edge surface of an adjacent panel strip.

18. Apparatus according to claim 17, wherein the same outer or inner edge surfaces of adjacent panel strips are attached together by adhesive, welding, stitching or any combination thereof.

19. Apparatus according to any preceding claim, which is actuable by a control system which is operable automatically or manually.

20. Apparatus according to claim 19, wherein the control system is operable by switch means connected thereto.

21. Apparatus according to claim 20, wherein said switch means comprises an inclinometer.

22. Buoyancy and stability apparatus substantially as hereinbefore described with reference to the accom¬ panying drawings.

23. Buoyancy and stability apparatus according to any preceding claim, when supplied as a kit for asso¬ ciation with the hull of a ship.

24. A ship whose hull is associated apparatus .accor¬ ding to any of claims 1 to 22.

25. An inflatable buoyancy bag constructed from a plurality of panels of a flexible material, wherein the edges of each panel are secured to the same inner or outer edge surfaces of adjacent panels.