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Title:
ARRANGEMENT FOR COLLECTING OIL SPILL
Document Type and Number:
WIPO Patent Application WO/1992/019818
Kind Code:
A1
Abstract:
Arrangement for collecting oil spill and the like from a water surface with waves (A), comprising a relatively elongate channel formed by two side confining surfaces (1B, 2B) which diverge from each other outwardly from a narrow inner end (10B) towards a wider mouth (111-212) which is adapted to generally face against the wave incident direction (A). At least one of the two side confining surfaces (1B, 2B) along a substantial portion of the length (10B, 1AB) has its upper edge adapted to be regulated with such a height (freeboard) with respect to the water surface that waves rolling into the channel will wash over the upper edge of the side confining surface(s) with their wave crests. There is provided a collecting tank (3, 5) in association with the side confining surface (1B, 2B) concerned, for collecting water and oil and the like being washed over said upper edge.

Inventors:
Mehlum
Even, Lovhaugen
Odd
Application Number:
PCT/NO1992/000075
Publication Date:
November 12, 1992
Filing Date:
April 14, 1992
Export Citation:
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Assignee:
Norwave A.
Mehlum, Even Lovhaugen Odd
International Classes:
E02B15/04; E02B15/10; (IPC1-7): E02B15/04
Foreign References:
SE433637B1984-06-04
NO148196B1983-05-16
GB2182260A1987-05-13
DE3006360A11981-08-27
DE3728937A11989-03-09
US3757953A1973-09-11
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Claims:
C l a i s
1. Arrangement for collecting oil spill and the like from a water surface with waves (A) , comprising a comparatively elongate channel formed by two side confining surfaces (IB, 2B, 15A, 15B) which in general diverge from each other from a narrow, open or closed inner end (10B, 150) towards a wider mouth (111212), c h a r a c t e r i z e d in that at least one of the two side confining surfaces (IB, 2B, 15A, 15B) along a portion of its length (10B1AB) has its upper edge (IBC) adapted to be adjusted at such a height (freeboard) in relation to the water surface that waves (AX, AY) which from the mouth (111 212) roll into the channel will wash over the upper edge (IBC) of the side confining surface(s) with their wave crests, the mouth being adapted to generally face against the wave incident direction (A), and that a collecting tank (3, 5, 30) is provided in association with the side confining surface(s) (IB, 2B, 15A, 15B) concerned, for collecting water and oil and the like which is washed over said upper edge (IBC) .
2. Arrangement according to claim 1, c h a r a c t e r i z e d therein that it is moveable, such as by towing by means of one or more vessels (21, 22, 31, 32) , in particular against the wave incident direction (A) .
3. Arrangement according to claim 1 or 2, c h a r a c t e r i z e d therein that at a location in front of the mouth it is provided with a wave generating unit (19) adapted to generate waves in said wave incident direction (A).
4. Arrangement according to claim 1, 2, or 3, c h a r a c t e r i z e d in that the shape of the channel as seen in the horizontal and vertical planes, as well as the weir level (freeboard) of the channel are adjustable, such as by moving the individual units of which the side confining surfaces and the bottom are composed, or by ballasting the channel in the longitudinal and lateral directions in order thereby to optimize the efficiency of the oil collection under different and varying operational and wave conditions.
5. Arrangement according to any one of claims 1 4, c h a r a c t e r i z e d in that the collecting tanks (3, 5, 30, 60) are adapted to be open at the bottom during collec¬ tion of oil spill and the like.
6. Arrangement according to any one of claims 1 5, c h a r a c t e r i z e d in that the collecting tanks (3, 5) are provided with generally vertical bulkheads or separation walls so as to form individual compartments (5A, B, C) having a certain limited mutual liquid communication, for damping down liquid movements in the collecting tanks.
7. Arrangement according to any one of claims 1 6, c h a r a c t e r i z e d in that said two side confining surfaces are formed by two barge or boat hulls (1, 2) being interconnected (100A, B) along a portion (10) of mutually adjacent hull sides, whereby said mouth is formed between forward bow parts (111, 212) of the two hulls, and one or both hulls (1, 2) is utilized as a collecting tank (3, 5).
8. Arrangement according to any one of claims 1 6, c h a r a c t e r i z e d in that the two side confining surfaces (15A, 15B) are formed by a separate channel unit (15) composed of sections or walls, and that the collecting tank is formed by at least one separate tank unit (30) which preferably detachably is adapted to be coupled to the channel unit (15) .
9. Arrangement according to any one of claims 1 8, c h a r a c t e r i z e d in that each collecting tank (3, 5, 30, 60) has a sufficient depth and area for an efficient separation between oil and water to take place as a conse¬ quence of the buoyancy of the oil, in spite of surface move¬ ments arising inter alia by water and oil and the like being washed over said upper edge (IBC, 15A, 15B) .
10. Arrangement according to any one of claims 1 9, having an open inner end of the channel, c h a r a c t e r i z e d by having a free throughrunning water passage (110) rearwardly from said narrow inner end (10B) of the elongate channel.
Description:
ARRANGEMENT FOR COLLECTING OIL SPILL

This invention relates to an arrangement for collecting oil spill and the like from a water surface with waves.

There are numerous proposals concerning means for col- lecting oil spill, but they all have in common that bad weather with waves makes the equipment more or less in¬ efficient or even completely useless. Examples of such known equipment may be found in Norwegian patent 148.196, German patent 3.728.937, Swedish patent 433.637, and US patent 3.757.953. The two patent specifications first mentioned above relate to a vessel structure having hull parts being mutually displaceable for collecting oil spill therebetween. The actual collecting of the oil layer from the water surface is quite subordinate in both patent specifications. Swedish patent 433.637 and US patent 3.757.953 however, are directed to arrangements for collecting oil spill from the sea sur¬ face. Both proposals comprise a weir adapted to extend transversally to the relative direction of movement between the equipment and an oil slick, with the weir somewhat sub- merged under the water surface. It is obvious that these solutions will be completely useless when waves of signifi¬ cance occur where it is desired to collect oil.

Moreover, reference can be made to British patent publi¬ cation 2.182.260 which shows an oil collecting arrangement comprising a relatively elongate channel formed by two side confining surfaces which in general diverge from each other from a narrow inner end towards a wider mouth. A pre-con¬ dition with the arrangement is movement through the water in order to obtain a relative water flow inwards through the channel. Also here waves will represent a problem.

In contrast to the previously known proposals, the present invention is directed to a solution which positively takes advantage of waves existing on the surface, for the attainment of an effecient oil collecting function. In this connection reference is also made to Norwegian patent 149.898 which in principle can be considered to utilize wave move¬ ments in a manner corresponding to a large degree to the

consepts behind this invention. This earlier Norwegian patent, however, is directed to the utilization of wave energy for power production and is primarily concerned with permanent, land based plants for this purpose. On this background the novel and specific features of the collecting arrangement according to the present invention in the first place consist therein that at least one of the two side confining surfaces along a portion of its length has its upper edge adapted to be adjusted to such a height (free- board) in relation to the water surface that waves which from the mouth propogate into the channel will wash over the upper edge of the side confining surface(s) with their wave crests, said mouth being adapted to generally face against the wave incident direction (A) , and that a collecting tank is provi- ded in association with the side confining surface(s) con¬ cerned for collecting water and oil or the like which has washed over said upper edge.

Practical embodiments of the arrangement according to the invention can be in the form of specifically designed vessels or combinations of vessel hulls which form the parti¬ cularly shaped channel as stated above. The channel and the collecting tank can also be designed as separate structures being specifically adapted for their respective functions. The structures can be based on conventional, rigid materials, such as metal or plastic plates etc. However, they can also be built completely or in part of relatively soft material, for example rubber or plastic material sheeting. The shape rigidity of such structures can be provided for by building the units with double walls, bracing the structure with tubes of plastic sheeting etc. and to fill such tubes, double walls or the like with air or a liquid under pressure, which makes it possible to attain the desired rigidity. A suitable relationship between, for example, air and water in such fillings can at the same time be used for obtaining the desired buoyancy in water of the structure or the units thereof, whereby varying ballast can additionally be utilized for adjusting the height of the above mentioned upper edge or weir, i.e. freeboard, in relation to the water surface.

For explaining the invention more closely, embodiments thereof shall be described in the following with reference to the drawings, wherein:

Fig. 1 is a schematic plan view showing a first embodiment being based on two vessel hulls and towing by means of a towboat, fig. 2 in elevation shows one of the hulls included in the arrangement of fig. 1, fig. 3 in a similar way as fig. 1 shows a second e bodi- ment based on a more specially designed and com¬ bined vessel structure, fig. 4 shows the arrangement of fig. 3 in elevation, and fig. 5 in cross sectional view shows a specific example of a structure of a collecting tank which can be in- eluded in the arrangement of figs. 3 and 4.

Fig. 1 shows two vessel hulls or barges 1 and 2, which along mutually adjacent after parts 10 are held together by connecting means as indicated at 100A and 100B. During a collecting operation the two hulls 1 and 2 in an inter-con- nected position are towed, for example by two towboats 21 and 22, and a towing arrangement which can comprise lengths of more or less conventional oil booms 11 and 12 being connected to the bows 111 and 212 respectively of the hulls 1 and 2. The booms 11 and 12 act in a usual manner to collect wide oil slicks to a more concentrated form for the actual collecting from the water surface, as will be described below.

The particular collecting effect based on wave movements in the water surface takes place in the inwardly narrowing channel which is delimited by both hull sides IB and 2B from the bow parts 111 and 212 respectively, inwardly to an inner narrow end at the point 10B.

As will appear more specifically from fig. 2, hull 1 (and correspondingly the hull 2) is designed with a lowered portion 1BC along the hull side IB which is adapted to face the hull 2 in the operative position. This lowered portion 1BC forms a threshold or we ^ r which by ballasting of the hull is adapted to be brought into a suitable height (freeboard) above the water surface, so that waves which roll into the channel between the hulls will be able to wash above this

weir 1BC and be collected in tanks 3 and 5 being formed by the respective hulls 1 and 2. The wave incident direction is as indicated with the arrow A in figs. 1 and 2. By suitable manoeuvering the whole tow and the two hulls 1 and 2 which form the collecting channel, are so orientated in relation to the existing wave direction that the waves enter the channel with the direction indicated by the arrow A.

As a specific possibility in the case that natural waves do not occur in the area concerned during a desired collect- ing operation, a wave generating unit 19 can be provided in the tow arrangement. Various known types of such units or wave machines may be used for this purpose. A further possi¬ bility at this point consists in providing for the wave movements desired, by the towboats 21 and 22 themselves, whereby an alternative is to have specifically designed structures associated with their motive propellers.

As described in Norwegian patent 149.898 mentioned above, waves which propagate into such a narrowing channel will build up to a larger wave height until the wave crests wash over the threshold or upper edge of the side confining surfaces which form the channel. An attempt to illustrate this effect is shown in fig. 2, in which the wave crest AY exceeds the weir level of the upper edge 1BC so that oil and perhaps some water at the surface will flow over the weir and into the collecting tank 3 (fig. 1) . The following wave AX in this example has just reached up to the upper edge or weir 1BC with its wave crest. Depending upon the height of the incident waves in relation to the selected weir level or freeboard of the upper edge 1BC, the flowing-over of wave crests apparently can be started already at a more upstream point along the length of the upper edge 1BC between end points 1AB and 10B thereof in figs. 1 and 2 of the drawings. Thus, in this example this lowered weir portion of upper edge 1BC extends along the major part of the length of the hull sides which form the confining surfaces of the channel. In the hull 2 the lowered weir portion comprises a corresponding distance from the forward point 2AB to the mentioned inner narrow end 10B. There is reason to mention, however, that overflow of oil and possibly water into the collecting tank

may be brought about also in water without waves, if the collecting arrangement is being towed as explained above and the weir level is adjusted beneath a certain limit which depends, inter alia, upon the towing speed. As shown at 110 in fig 1 there is a certain small space between the two hull sides, so that there is established a free through water passage rearwards from the above mentioned inner end 10B of the channel. Such a through passage may be an advantage under certain conditions, so that a portion of the water mass in the waves will be able to flow through and so to speak be left behind the two hulls during towing through an area of the sea having oil spill on the surface. A particular lowered weir portion with the upper edge 1BC as described above with reference to fig. 1, is not strictly required in order to obtain the effect aimed at.

When the side confining surfaces of the channel are formed by vessel hulls as in the example discussed, a quite corres¬ ponding effect may be obtained with such a weir or upper edge fully corresponding to the conventional gunwale on ship hulls, as shown at 1C in fig. 2. This may be approximately rectilinear when considered in the vertical plane, and prefe¬ rably horizontal as in fig. 2, but modifications of this preferred and somewhat idealized arrangement in this respect, may be contemplated. Ballasting of the arrangement and thus the freeboard, possibly with a varying weir level along the length of the side confining surfaces, may be suitable under particular conditions.

Another possibility for variation consists therein that the two hulls 1 and 2 in fig. 1 by means of connections 100A and 100B can be adjusted with their longitudinal axes at different angles in relation to each other, which involves change of the shape of the channel since the ships' sides or side confining surfaces IB and 2B at the same time will change attitude with respect to each other. Thereby the angle of divergence of the channel and the width of the mouth between the bow parts 111 and 212 can be selected.

As already mentioned the two vessel hulls 1 and 2 as such can be utilized for providing collecting tanks 3 and 5 respectively, for oil removed from the water surface. The

hulls can be sub-divided into sections with bulkheads or the like for the purpose of damping down water and oil movement in the tanks, which inter alia enhances a desired separation of water and oil having flowed into the collecting tanks. In fig. 1 with respect to hull 2 there is for example indicated three tank sections 5A, 5B, and 5C, formed by sub-division as explained here. It will be realized that a certain, limited mutual liquid communication should exist between such sub¬ divided sections or compartments. It may be an advantage that the level in each collecting tank is adapted to be approximately the same as the mean level of the surrounding water surface.

Also the adjustment of the side confinement, for example by ballasting, to a desired freeboard of the weir or upper edge portion during oil collecting from waves, is of sig¬ nificance for obtaining as quiet and subdued conditions as possible in the collecting tanks 3 and 5. Since oil in this manner will be lying above the water mass in the tanks, it can be a great advantage to provide openings at the bottom of the collecting tank, so that the water can by and by escape whereas the oil will be retained in the upper part of the collecting tanks. The embodiment of fig. 5 shows in more detail a solution at this point.

Figs. 3 and 4 show an example of another embodiment of an oil collector according to the invention. This comprises a separate channel unit 15 adapted to be coupled to or built into a collecting tank 30, which also constitutes a separate unit being preferably adapted to be detachably connected to the channel unit 15. Thus the combined structure is intended to be built up from sections or walls and so that the channel has either a fixed shape, which is in contrast to the channel in fig. 1, or is adapted to be modified into various configu¬ rations. The design in figs. 3 and 4 are considered to be well suited for construction with soft materials, such as plastic sheeting or the like as mentioned above.

Also the embodiment of figs. 3 and 4 is intended for towing, for example by means of two towboats 31 and 32 with a tow arrangement where there may be involved boom lengths 13 and 14 similar to what has been explained in connection with

fig. 1. Of course it is possible to provide the collecting vessel with its own propelling machinery and navigation eq ment, so that it will be self-contained and independent of towboats. The channel unit 15 with its side confining surfaces 15A and 15B can be attached to the tank 30 with suitable attach¬ ment means. As will appear in particular from fig. 4 the channel in this example has a closed bottom 15C which can be located so deep that it has no significant influence on the incident waves. As explained above it is not at all, how¬ ever, necessary for the function desired that there is any bottom in the channel. In the embodiment of figs. 3 and 4 the bottom can be considered to have a function with respect to mechanical strength. As drawn in fig. 1 the channel 15 can be considered to be closed at the inner end 150, but as in the example in fig. 1 this inner end can be provided with an opening for free water through-flow either in a direction downwards and out into the sea or into an adjacent collecting tank. The design of tank 30 kan comprise lattice or frame-like reinforcements 33 and along the upper side pontoons or buoy¬ ant bodies 30A which can be partially or completely filled with water or air, and which by correct ballasting will secure a suitable height of the tank walls and the weir level (freeboard) of the channel 15 connected to it, in relation to the water surface. It can be an advantage to have the chan¬ nel unit 15 itself provided with such buoyant bodies, so that it can be manoeuvered and ballasted without any collecting tank 30 attached thereto. One point of interest in connec- tion with such division into separate units for the channel and the tank respectively, is that the collecting tank when it is filled with oil, can be detached and towed as a separ¬ ate transport operation for example to a plant on shore for receiving oil spill, at the same time as another empty and corresponding tank is coupled to the channel unit. A similar manner of operation can of course be performed with the arrangement of fig. 1.

In fig. 4 there is schematically shown a bottom member 40 of the collecting tank 30, and as mentioned above it is a

practical advantage to provide openings or valves in or at this bottom structure in order to let collected water escape, so that the capacity of the collecting tank can be utilized to the maximum extent for collected oil spill. The separa- tion effect discussed above means that water being discharged is sufficiantly free from oil to make such discharging accep¬ table.

A more concrete example of a design of a collecting tank 60 is shown in fig. 5. This structure is shown in cross- section, which could for example correspond to the rear part of the collecting tank in fig. 3, i.e. rearwardly of the channel 15. The structure in fig. 5 comprises double side walls 41A-42A, and 41B-42B, respectively, which form closed chambers or floats adapted to provide for the required buoya- ncy for the whole tank structure, this being in analogy with the pontoons 30A in figs. 3 and 4.

Moreover the tank in fig. 5 has a bottom 50 which along the side edges has upwardly projecting plate members 51A and 51B inside the double walls mentioned above. By means of suitable attachment devices as shown at 55 the bottom 50 and possibly the plate members 51A and 51B are joined to the remaining tank structure. As indicated with the arrow B water which has been received in the tank 60 can escape to the surrounding sea, whereas a collected oil layer 66 will be lying uppermost in the tank. The water level inside and outside the tank will be approximately the same because of the openings at the bottom. How high in the water the colle¬ cting tank 60 shall float, can be regulated by means of suitable equipment which can let out air from or pump air into the chambres between the double side walls. For ballas¬ ting reasons these chambers can be sub-divided into suitable sections by means of horizontal and/or vertical bulkheads (not shown in the figure) . In view of the intended efficient separation between oil and water, in particular when taking into account possible surface movements due to water and oil being washed into the tank over the above mentioned weir or upper edge (not shown in fig. 5) it is also significant that the collecting tank has a sufficient depth in relation to its surface area. The structure in fig. 5 primarily can be

considered to be composed of rigid materials , for example steel plates and the like, but possibly, with some small modifications, may also be made of soft materials with a fluid filling as discussed above. Both the channel and the collecting tank can be without any bottom at the whole or portions of their basic area. If the tank has a full bottom and separate openings or valves for letting out water, these can be adjustable and completely closeable, so as, for example during transport, to secure that the contents of oil or other pollutants cannot leak out. Other possible modifications of the embodiments shown in the drawings can consist therein that the freeboard or weir level of the important weir edge is adjustable in another way than by means of ballasting of the hull or unit concerned as a whole, for example by displacing corresponding plate parts upwards or downwards in relation to the adjacent structure. As an example of dimensions relating to this weir level or freeboard heights of up to 3-4 meters above mean water level can be mentioned, this being dependant on the height of waves being present.

With an arrangement as described here there is obtained a very high capacity in the collecting function, which means that very large volumes of water can be treated and cleaned with respect to oil spill and the like floating on the sur- face.