GB2250240A - Oil or other spillage containment - Google Patents

Abstract

A method of containing oil or like spillage floating on the surface of the sea or other waterway is by means of a disposable self inflating boom assembly which is launched into the sea. Inflation of the assembly via control valves and supply lines is from a gas supply module, and both are launched from within a mobile assembly or container on a ship, platform, helicopter or by parachute from an aeroplane. Gas may be supplied from compressed gas cylinders, or by chemical reaction on contact with water, or from an air compressor or blower. Various arrangements of boom are described including having a membrane to create separately inflatable compartments, having at least one lower skirt, and using two adjacent boom assemblies. When the containment operation is completed the boom is recovered from the sea, cleaned and disposed of.

Description

OIL SPILLAGE AND OTHER CONTAINMENT.

OBJECT.

This process relates to the control and recovery of oil spillage or other containment on the surface of the sea or other waterways.

When there is a spillage of oil fran a marine or shore based source the first priority is to contain the spillage and then to remove the oil fran the surface of the water as quickly as possible.

Present methods are costly, take too long to operate and cause unnecessary darrage to the environment due to the delay.

The proposed method is faster and more efficient thereby reducing this damage. It is also more cost effective due to the fact that most of the oil recovered is a saleable product after treatment due to the speedy containment and recovery. The costs of a clean up operation and also insurance premiums are also substantially reduced.

The design philosophy and concept can be compared to that of fire fighting and control where there is an immediate response with user friendly auxiliary automatic and or manual equipment in-situ, with a mobile back- up, which could be sea and / or airborne for a speedier response.

METHOD.

The oil spillage floating on the surface of the water is prevented fran spreading and is contained by means of a floating bean assembly as shown in Drawings 1 / 7 to 7 / 7 together with "General Descriptions And Features" on page 7 and "Reference Numbers And Descriptions" on page 8.

Air to inflate the boam assembly is supplied fran cylinders of compressed air 14, via pressure control valve assembly 13, flexible air supply lines and couplings 11, through air supply passages 4, non return valves 3, and into buoyancy compartments 1 as shown in Drawings No.2 / 7 "Process Diagram Of System" and 4 / 7 "Boan And Air Supply Storage / Launch Assy.

The boom assemblies are fabricated in optimum lengths with suitable end connections 19, and are attached to the adjoining assemblies in such a manner so as to form a continuous floating flexible boom together with the ends of the hawsers ( if required ) to a length sufficient to contain the oil spillage.

A hawser assembly if required which is separate and attached at intervals and/or a reinforced skirt of at least one tensile load bearing merrSer integral with the skirt would be used to take the tensile loads imposed on the boan.

The boom assemblies are stowed away inside an outer container 16, as shown in Fig 12, 13 and 14 or on a reel as shown on Fig 15, in such a manner that if an oil spillage occurs the assemblies complete with air supply can be speedily launched and floated.

The boom assembly launcher would be located at a convenient position to launch fram the deck of a tanker, dingy or other vessel, oil platform, shore installation, helicopter etc.

The launching procedure from a ship for instance would be to position the launcher at the stern, turn on the air supply and operate the quick release mechanism to detach the air supply module from the boom assembly stowage locker. The module slides and / or is pushed by the inflating boom assembly over the stern where it falls and floats in the sea. The boom assembly which is being inflated expands out of the locker and is ejected or pulled into the sea due to the movement of the vessel the connecting air hoses being of sufficient length to facilitate this operation.

The air supply passages along the boom assemblies are pre-formed during manufacture so that they spring back to there original shape at or below internal atmospheric pressure when unpacked so that the air supply passages assist and offer the least possible resistance to the flow of air through them in order that the loss of pressure head over long distances be kept to a minimum and also that the air supply passages provide a fast initial buoyancy prior to train compartments being inflated thus enabling the boan to be laid as quickly as possible.

This process is repeated as required, the next launcher being suitably positioned to facilitate the relevant connections between boon assemblies being trade prior to launch until the operation is completed.

The lengths of these boom assemblies would appear to be limited (apart fran the manufacturing and logistic considerations) mainly by the quantity and pressure drop of the air supply over long distances, therefore, provided these requirements are satisfied, continuous assemblies of considerable length seem practical.

This would enable an oil tanker, for instance, which is losing its cargo due to a collision to be self sufficient in containing a large oil spillage within a floating boom wall until recovery. See Fig 16.

This would be achieved by launching air supply modules followed by the beans which are attached to each other fram the launch assemblies located on the stern deck whilst the tanker turns and encircles the oil spillage decelerating to suit until the spillage is enclosed within a continuous boom wall.

It ray be that at least one air compressor or blower and or dingy complete with launchers is used in conjunction with such an operation Fig 17 shows an oil spillage being carried by the current and spreading.

Two vessels attach the ends of there respective boom assemblies to each other and sail as shown laying and attaching the boom assemblies to each other until ideally the full width of the oil spillage is enclosed. The two vessels sail very slowly against the current and around the spillage until eventually the oil spillage is enclosed within the boom wall assembly. By slowly decreasing the area inside the bocan enclosure a considerable depth of oil would be achieved for the oil recovery operation.

In this instance the boom assembly is used as a trawl with the corresponding increase in loads which are taken up by the tensile reinforcement of the skirt and / or the hawser.

Fran a cost and practical point of view the launchers are constructed on a module principle, are self contained and able to fulfil the projected requirements of the size of Ship, platform or other installation.

NOTES ON MANUFACTURE, STORAGE AND USE.

A fail / safe design concept has been used in the buoyancy assembly design in order that the required reliability is achieved using cheaper materials and construction methods whilst meeting the expected quality control and insurance requirements, this is achieved by :1.Having at least two prime sources of air supply so that with the complete failure of all except one supply the buoyancy system is safe.

2.Having at least two secondary air supplies so that with the failure of all except one the buoyancy system is safe.

3.A central membrane dividing each buoyancy compartment so that if one side fails the other side inflates with the membrane replacing the failed side thus making the compartment safe.

4.If at least any two consecutive buoyancy pockets fail the adjoining boan wall will maintain the booms effective height and the skirts effective depth.

5.The entire assembly is sufficiently flexible so as to rise and fall with the waves and swell and maintain sufficient boom height and skirt depth in order to prevent oil passing over or under the bean.

6.The assembly is able to stretch to absorb stresses imposed with the ebb and flow of local currents.

The dimensions and loading of the boom assemblies are to a large extent empirical but if used solely for containment purposes where the boom drifts with the currents and is sufficiently flexible so as to offer the minirurn resistance to the forces of the sea ther. a boom of minimum height with sufficient skirt depth would be sufficient to contain major oil spills.

Irrespective of the relative densities and movements of the oil and water a state near to equilibrium will exist between both sides of the boom the difference in densities being compensated for by the higher level of the oil inside the boom and the movement met with minimal resistance due to the light weight flexible boom assembly.

For an example approx. 3,000 metre long x 0.15metre above mean sea level low pressure inflatable bean assemblies with 0.6 metre reinforced skirt below ( appro. 1,000 metres length per 1.5 cu.metre volume.) together with four standard compressed air cylinders of 9.3 cu. metre air capacity each for initial buoyancy could be accommodated in an approx. 6.0 cu.metre storage capacity launch assembly.

The material of construction for the boom would be 0.3mum thick E.V.A.

copolymer for instance, but cheaper inflatable grade two ply laminate materials 0.3mn or 0.2mn thick in fluorescent colours which are quality proven in the manufacture of chlldren's life preservers for an instance should suffice.

Figs 1 to 7 showdifferent types of boom sections together with relative details but the profile and construction is not restricted to these and other shapes can be evolved. For instance several inflatable tubes surrounding a central tube with or without non return valves may be found to be effective.

Fig 6 which is a twin boom structure each connected at the bottom by a conmon skirt forming a small reservoir may be preferred due to its increased safety factor and also its ability to support a suction line between its buoyancy compartments during the oil recovery operation later. It may also be constructed with ballast compartments under which could be filled with water from above or a pump if required.

Connection assemblies required to attach the end of one boom to the next will be constructed in such a manner so that they are easily attached and make a strong sealed joint.

The air supply control system will include at least one pressure relief control valve as and where required.

The number of compressed air cylinders will be at least one but their number and size will be governed by the length of boom, with the resulting volume and rate of air supply required.

It may be that a boom assembly whose section is constructed to minimum practical dimersions and thickness of material with greater flexibility and with a load bearing reinforced skirt ( in order that a separate hawser is not required ) is to be preferred so that the maximwzn length of boom can be stored inside the Air Supply / Launch Assembly. Air fan type blower(s) or cczpressor(s) may be used to supplement or replace the air supply after the initial buoyancy of the boom is completed located on board ship or on air supply module complete with power supply.

A helicopter could be used when it would descend to a rirr;rm safe height above the sea, launch the air supply module into the water followed by the boom which would be pulled out of its container and inflated as the helicopter travelled along the periphery of the oil spillage.

An aircraft could also be used. The boom and air supply storage / launch assembly could be stored ( with an inflatable dingy if required inside of a shock absorbent buoyancy capsule, or similar, attached to a parachute and dropped from the aircraft into the sea in the vicinity of the oil spillage where the containment process as previously described would be put into operation.

At least one other vessel would be used if required to facilitate a more efficient and speedy operation.

Fig 8 process diagram of system shows a typical single boom assembly attached to adjoining assemblies complete with air supply Fig 9 and 10 shows diagramMtic sections for the fabrication of a typical single boom assembly ( no ballast compartment ).

When an oil spillage recovery operation has been completed the boom assembly is taken on beard a recovery boat where it is deflated, cut up, cleaned, packaged and suitably disposed of.

Fig 18. Shows an inflated twin boom assembly ( with reservoir in a folded position ) similar to Fig 6 but with a larger reservoir between.

Fig 19. Due to the rise and fall of the surface of the sea, oil and water enters the reservoir through the surface inlet holes 10, and is held captive inside the reservoir by the non-return valves when the sea surface level falls. This creates a pressure head inside the folded reservoir due to the difference in levels between the outside and inside of the reservoir which increases the volume inside causing the reservoir to unfold as the mixture separates with the water sinking to the bottom and returning to the sea through water outlet holes 10A. The surface level of the oil inside the reservoir rises above the level outside due to its lower density until the resulting pressure head inside closes the non-return valves.

Inlet and outlet holes located in botch sides can be used to collect spillage from either side, or inlet holes on the spillage side and outlet holes on the opposite side may Drovide slight propulsion, or with or without outlet holes only and used for storage.

Fig 20. Shows the buoyancy compartments inflated by gas generated by the reaction created when a suitable chetnical canes into contact with the sea. This is achieved by enclosing metered quantities of the chemical inside pockets located against the buoyancy compartments. The chemicals when dry are inert and may be in the form of a powder, amalgam, capsule, liquid, prill, flat strip or painted onto the inside surface of the pockets. Each pocket has an opening complete with non-return valves on the outside and inside surfaces so that the direction of flow is inwards.

For storage purposes the entire boom assembly is vacuum dried, packed and hermetically sealed inside an outer water proof cover, suitably protected against impact and stored inside a weather proof storage container.

To activate the system the seal is broken and the boom assembly is launched into the sea. Sea water enters into the pockets where it reacts with the chemical agent generating a gas whose volume and pressure increases thus closing the inlets fram the sea and operir.g the inlets to the buoyancy compartments through which the gas enters inflating the compartments. Pressure relief may be required.

A water permeable outer cover to the pocket may be used in piace of a non-return valve which would be constructed using present day state of the art technology where water passes through a fabric but in doing so the elements of the fabric expand making the cover impervious to the ingress of further water from the outside and also to the escape of the gas generated at low pressure from inside the pocket which is used to inflate the buoyancy compartment via a non-return valve. When the pressure of the surplus gas generated inside the pocket increases to some empirical value beyond that which the outer cover is able to resist these gasses escape to atmosphere through the now porous surface of the outer cover to atmosphere until the pressure falls to that which the fabric is able to resist when the escape of gasses cease.

A separate container for the chemicals may be used, suitably located and connected to the buoyancy compartments.

This system may be self sufficient or used to provide initial buoyancy in conjunction with other systems.

A process using a mixture of gas generating chemicals and blown foam (Phenol Fonnaldehyde or other) generating chemicals could be used for buoyancy inside the pockets and or buoyancy compartments.

Fig 23. Shows the average relative velocities in section of a typical sez current where V1 the velocity of the spillage on the surface of the sea is less than that of V2 the velocity against the skirt due to the velocity of a sea current decreasing relative to its depth.

These differences in average velocities, though small, causes a small average uniformly distributed dynamic pressure to be exerted along the entire length of the skirt assembly acting against the surface current causing the boon to move upstream against the flow of the spillage with a small relative velocity of V1 - V2 = V3 approx.

The possible adverse effect of forces which can be exerted by the wind and current on V3 will be partly cancelled out due to the spillage also being effected by these forces and also reduced by the high resistance offered by the submerged skirt assemblies and the low resistance offered by the low profile boom buoyancy above the surface of the sea.

Fig 24. Shows a self filling ballast compartment the principle of which is that due to the differential pressures imposed by the water against the openings due to vertical and lateral movement trznsnitted by the movement of the buoyancy compartments above to the ballast compartments below, water enters the ballast compartment when the dynamic pressure exerted by the movement of the sea increases and is retained by the non-return valve when the pressure decreases. This cycle is repeated until the volume and pressure of water inside the ballast compartment keeps the non-return valve closed. The position and number of these water inlets is empirical and may be located anywhere around ballast compartments to suit.

This type of ballast compartment can form part of the structure of any boom assembly to suit.

Ballast compartments can also be filled through water supply passages 21A from reservoir above or pumped water supply passages 21B as shown in Fig 6.

CXY.XCLUSION.

The choice of equipment will be governed by the possible spillage quantities to be catered for, type of transport or installation in wnich the equipment will be located, environment and other considerations will govern type, size, length of boom and method of inflation which is best suited for a particular situation.It may be that a chemically generated gas inflated boom assembly of rninirni sectional area and thickness of material and rtaxrmum length with self filling ballast, packed concertina wise and hermetically sealed which occupies the least volume and weight and can be laid at great speed is best suited when using a helicopter Chemically generated gas, inflation may be used initially then air or other gas from scme other source may be used to maintain buoyancy.

Any combination of the stated methods of boan, buoyancy, ballast, gas and water construction, supply and operation may be used to suit requirements.

OIL SPILLAGE CONTAINMENT.

DRNINGS Nos. 1 TO 7. GENERAL DESCRIPTIONS AND FEATURES.

DRAWING No 1 / 7.

FIG No. 1. SECTION OF BOOM 2. ELEVATION "B-B" OF BOOM.

3. PLAN "A-A" OF BOOM.

4. SECTION OF DAMAGED SHOWING FAIL-SAFE PRINCIPLE.

5. SECTION OF BO. - EXAMPLE "A". WITH SINGLE SKIRT.

5A. SECTION OF TWIN BOCK WITH BALLAST BETWEEN TWIN SKIRTS.

6. SECTION OF TWIN BOCH. - EXULE "B".

7. ELEVATION "C-C" OF TWIN BOCK.

DRYING No. 2 L 7.

8. PROCESS DIAGRAM OF SYSTEM.

DRAWRING No. 3 / 7 9. SECTIONAL ELEVATION OF BOOM.

10. DIAGRAMMATIC SECTION OF BOOM (TYPICAL MAMPLE FOR FABRICATION).

11. SECTION OF BOOM (FOLDED FLAT FOR STORAGE).

DRINGNo. 4/7.

12. BOCM AND AIR SUPPLY STORAGE / LAUNCH ASSY. TYPE "A".

( FOLDED CONCERTINA FASHION ) ELEVATION.

13. END VIEW OF FIG 12 14. PLAN VIEW OF FIG 12.

15. BOOM AND AIR SUPPLY STORAGE / LAUNCH ASSY. TYPE ( WRAPPED AROUND REEL ) ELEVATION.

DRAWIING No. 5 L 7.

16. TYPICAL OIL SPILLAGE FROM TANKER - SELF OPERATED OIL CONTAINMENT OPERATION TO ENCLOSE OIL WITHIN BOOM.

DRAWING No. 6 L 7.

17. TYPICAL OIL SPILLAGE CONTAINMENT OPERATION USING AT LEAST TWO BOATS OR AUXILIARY SHIPS TO ENCLOSE OIL WITHIN BOOM.

DRYING No. 7 L 7.

18. SECTION OF TWIN BOOM SIMILAR TO FIG 6 BUT WITH INCREASED OIL / WATER SEPARATING RESERVOIR BEITWEN - FOLDED FLAT.

19. SECTION SHOWING RESERVOIR OF FIG 18 FULLY OPEN.

20. SECTIONS SHOWING BUOYANCY COMPARTMENI INFLATED BY GAS GENERATED BY REACTION OF CHEMICALS WITH WATER.

21. SECTION SHOWING FOLDED SKIRT OF FIG 18.

22. TYPICAL PART LONGITUDINAL SECT. D-D OF FIG 19.

23. SECTION SHOWING AVERAGE MEAN RELATIVE VELOCITIES OF A TYPICAL SEA CURRENT WHERE ; V1 = VELOCITY OF OIL SPILLAGE ON SURFACE OF SEA.

V2 = AVERAGE EFFECTIVE VELOCITY OF CURNT AGAINST SKIRT.

V3 = RELATIVE UPSTREAM VELOCITY OF BOOM ASSEMBLY AGAINST OIL SPILLAGE EQUATION V1 - V2 = V3 ( APPROX ).

24. SECTION SHOWING SELF FILLING INERTIA BALLAST CAPARTHENT.

OIL SPILLAGE CONTAINMENT.

REFERENCE NUMBERS AND DESCRIPTIONS.

1. Buoyancy Culçartments.

2. Skirt.

2A. Skirts Attached To Each Other To Form Continuous Enclosures.

2B. Continuous Enclosures In Folded Position.

3. Non-Return Valves.( Flap Or Other Type ) 4. Air Supply And Initial Buoyancy Passages. ( Elasticated And Pre-Formed And Or Thin High Strength Material ) 4A. Pocket Containing Gas Generating Chemicals With Non-Return Valve ( Flap Or Other Type ) In Outer Cover.

4B. Pocket Containing Gas Generating Chemicals With Water Permeable Outer Cover.

5. Central Membrane.

6. Reinforcement As Required.

7. Oil Or Other Spillage.

7A. Max & Min Level Of Oil Or Other Spillage Wave.

8. Sea Water.

9. Hawser ( If Required ).

10. Surface Oil Or Other Spillage & Water Inlet Hole Assemblies With Non-Return Valves ( Flap Or Other Type ).

10A. Separated Sea Water Return Outlet Holes. ( With Non Return Valves If Required ).

11. Air Or Other Gas Supply Lines ( Flexible ) And Couplings.

12. Boom Assembly Folded Or Wrapped Around Reel For Storage.

13. Control Assembly For Air Or Other Gas Supply.

14. Compressed Air Or Other Gas Cylinders.

15. Air Or Other Gas Supply Module Assembly Complete With Required Inner Buoyancy With Structures And Outer Casing.

16. Outer Container For Boon Storage ( And Hawser If Required.) 17. Hawser Pulley Guide Assembly (If Required.) 18. Hawser Location Lugs On Skirt (If Required.) 19. Boom Ends Connection Assembly.

19A. Partition Walls ( Folding ) Or 19B. Skirt Walls Attached To Each Other At Intervals Along The Reservoir To Form Separate Watertight Compartments Of Required Volumes.

20. Corrugated Bonding Or Other Bonding Or Welding.

21. Ballast Compartments.

21A. Water Supply Passages From Reservoir Above To Ballast Compartments ( If Required ).

21B. Pumped Water Supply To Ballast Compartments ( If Required ).

22. Quick Release Handle For Air Supply Module.

23. Pivoted Support For Air Supply Module.

24. Buoyancy Packing As Required (Foam, Hollow Balls, Or Similar ).

25. Deck.

26. Reel Assembly.

27. Tanker.

28. Boat, Dinghy Or Auxiliary Ship.

29. Air Compressor Or Fan Type Blower Complete With Power Pack And Or Power Supply.

Claims (37)

CLAIMS.

1. A method of oil spillage and other containment floating on the surface of the sea or other waterway by means of a self inflating boom assembly which is launched into the sea.

2. A method of spillage containment as claimed in claim 1 which is inflated via control valves and supply lines from a floating air or other gas supply module which is launched into the sea followed and connected by hawser (if required) & supply lines to the boom assembly.

3. A method of spillage containment as claimed in claim 1 where the boom is inflated through openings by the gas generated by chemical reaction between metered quantities of a suitable chemical inside of at least one pocket located against each of the buoyancy compartments, or inside a separate container, and the sea water which enters the pocket or container, through openings, the direction of flow being inwards fram the water via non-return valves which may be flap or other type.

4. A method of spillage containment as claimed in claim 3 where the chemicals in the absence of water are inert and may be in the form of powder, amalgam, capsule, mixture, liquid, prill, strip, tablet annular or solid, or painted onto the inside surface or combination of above.

5. A method of spillage containment as claimed in claim 3 where a water permeable fabric outer cover to the pocket may be used where water passes through the fabric but in doing so the elements of the fabric expand making the cover impervious to the escape of the low pressure gas generated inside the pocket but allowing any surplus high pressure gas to escape thus acting also as a pressure relief and may be used in cattination with claim 3.

6. A method of spillage containment as claimed in claim 1 wherein the air supply module assembly, air supply lines and boom assembly (together with a hawser and/or sheet anchor if required) are stored inside a container.

7. A method of spillage containment as claimed in any preceding claim, whereby for storage, all or part of the inflatable boom assembly is vacuum dried, packed and hermetically sealed and the modules and equipment are attached to each other in such a manner so that the whole assembly forms a protected, self contained weather-proof mobile unit.

8 A method of spillage containment as claimed in any preceding claim where a self contained mobile unit can launch a self inflating boom assembly from the deck of a ship, dinghy or other vessel, sea or shore based platform, helicopter or the entire self contained mobile unit can be dropped by parachute from an aircraft,

9. A method of spillage containment as claimed in any preceding claim whereby the inflatable boom is a flexible structure which is able to rise and fall with the waves and swell and maintain sufficient height above and skirt depth below the surface of the sea in order to prevent oil passing over or under the boom.

10. A method of spillage containment as claimed in any preceding claim whereby the boom has at least one skirt attached under in order to create an effective barrier beneath the water.

11. A method of spillage containment as claimed in any preceding claim whereby the boom is divided into separate inflatable compartments along its length in order that it be flexible and that if the outer wall is punctured only that compartment is effected.

12. A method of spillage containment as claimed in any preceding claim where there is at least one central membrane dividing each compartment into two so that if one side of the compartment deflates the opposite side inflates with the central membrane replacing the failed side thus making the compartment safe.

13. A method of spillage containment as claimed in any preceding claim where there is at least one air or gas inlet complete with non-return valve into each side of each buoyancy compartment.

14. A method of spillage containment as claimed in any preceding claim where there is more than one source of air from compressed air cylinders complete with air supply control assembly together with line attachments and buoyancy located inside air supply module assembly.

15. A method of spillage containment as claimed in any preceding claim, where there is at least one air supply passage at each side of the buoyancy compartments so that with the failure of all air supply passages except for one the system is safe.

16. A method of spillage containment as claimed in any preceding claim, so that if at least one buoyancy compartment fails the adjoining boom buoyancy will maintain the booms effective height and the skirts effective depth thus keeping the system safe.

17. A method of spillage containment as claimed in any preceding claim where a fail/safe design concept has been used in the boom buoyancy assembly design which enables the required reliability to be achieved using cheaper materials and construction methods whilst meeting the required quality and insurance requirements.

18. A method of spillage containment as claimed in any preceding claim where the boom assembly is constructed to stretch under minimum loading conditions imposed by the ebb and flow of local currents.

19. A method of spillage containment as claimed in claim 15, wherein each air supply passage is preformed during the manufacturing process so that when unpacked after storage they spring back to there original shape so as to give unrestricted air flow with minium pressure drop when being inflated.

20. A method of spillage containment as claimed in claim 15, where the air supply passages act as the initial buoyancy chambers when the boom assembly is launched in order that the boom be laid at the maximum speed.

21. A method of spillage containment as claimed in any preceding claim where there is at least one flexible reinforcing member in the skirt.

22. A method of spillage containment as claimed in any preceding claim where there can be at least two separate buoyancy cavartment assemblies alongside and attached to the bottom of each other and also at or near to the top of at least one skirt.

23. A method of spillage containment as claimed in any preceding claim ~~where there are two separate boom assemblies alongside and attached to each other by a continuous folded skirt at or near to the bottom of the buoyancy compartments with a space in between into which spillage passes from surface inlet holes located on the oil spillage side or sides the increased volume and pressure from which unfolds the skirt thus forming reservoir and/or ballast compartments.

24. A method of spillage containment as claimed in any preceding claim where there can be at least two separate skirts with space between attached to the underside of a twin boom assembly above the water between the skirts acting as inertia ballast.

25. A method of spillage containment as claimed in any preceding claim where self filling ballast pockets are formed at a suitable depth along the skirt(s) each with a central dividing medbrane if required.

26. A method of spillage containment as claimed in Claim 25, where due to the alternating pressures created by the tidal movement against the face of the flap or other type of non-return valve water enters through dt least one inlet opening located in the wall of each ballast compartment when most of water entering the compartments is retained aside each of the ballast compartments.

27. A method of spillage containment as claimed in claim 23 where the folded reservoir when opened acts as a separator with the water sinking to the bottom and returning to the sea through drain holes leaving the oil or other spillage in the reservoir.

28. A method of spillage containment as claimed in any preceding claim wherein the boom assly ly is packed flat and stored concertina fashion, or wrapped around a reel, or by sane other fashion and stored inside an outer container.

29 A method of spillage containment as claimed in claim 27 where the level inside the reservoir rises as the quantity of separated oil or spillage increases (due to the lower density) until the increasing pressure against the non-return valve stops or restricts the entry of further spillage.

30. A method of spillage containment as claimed in any preceding claim where due to the booms being disposable with minimum loading and life requirements inflatable grade two ply laminate material in fluorescent colours as used and quality proven in the manufacture of children's water wings etc or similar could be used enabling cheap mass produced inflatable booms to be manufactured.

31. A method of spillage containment as claimed in any preceding claim where due to the average velocity of a typical sea current decreasing relative to its depth an average uniformly distributed dynamic pressure is exerted along the entire length cf the skirt assembly acting against the surface current causing the boom assembly to move upstream against the spillage resulting in an increased depth of oil in front of the boom due to this trawl effect.

32. A method of spillage containment as claimed in any preceding claim where due to the low cost and limited life of the boom structures, when an oil recovery operation has been completed the boom is disposable and would be cut up, cleaned, packaged and suitably disposed of.

33. A method of spillage containment as claimed in any preceding claim where the boom can be inflated by at least one supply of cclDressed gas other than air, compressor or fan.

34 A method of spillage containment as claimed in any preceding claim where boom assemblies can be connected to each other to form a continuous assembly.

35. A method of spillage and other containment as claimed in any preceding claim where 2 twin boom assembly can be used in an emergency as a life preserver and containment for survivors in the sea.

36. A method of spillage and other containment as claimed in any preceding claim where the drain holes in the reservoir can be positioned so that the ejected water propels the boom against the spillage.

37. A method of spillage and other containment as substantially hereinbe,fore defined with reference to Figures 1 to 24 of the accompanying drawings.