GB2052282A

GB2052282A - Oil skimmer vessel

Info

Publication number: GB2052282A
Application number: GB7919812A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1979-06-07
Filing date: 1979-06-07
Publication date: 1981-01-28
Also published as: GB2052282B

Abstract

A craft of catamaran type for skimming oil from the surface of water comprises a pair of hulls (1,2) having a body (3) of smaller draught therebetween, a generally flat bottom surface of the body being perforated to allow the oil and water to flow into the interior of the body. The hulls (1,2) are each divided into a plurality of compartments by transverse bulkheads (11) having apertures (12) in their lower portions. The interior of body (3) communicates with the foremost compartment in each hull. A suction pump (9) in the aft of the body (3) causes the oil and water to flow from fore to aft through the compartments in each hull (1,2) the oil being skimmed from the water during its passage through the bulkhead apertures (12) and accumulating in the compartments. Water ejected from the rearmost compartments may be fed to ejector means (14) to impart forward motion to the craft. <IMAGE>

Description

SPECIFICATION Oil skimming craft This invention relates to a craftforskimming pollutants from the surface of a liquid, and more particularly to such a craft for skimming oil or other floating hydrocarbons from the surface of a lake, sea or river.

Surface pollution of a liquid by oil or other floating hydrocarbons is usually treated by chemical means: however, the solvents used for such treatment are often harmful to aquatic life. It is an object of the present invention to overcome this problem by providing a craft which removes the pollutant by a skimming action rather than by chemical treatment.

According to the present invention there is provided a craft for skimming pollutants from the surface of a liquid, comprising two hulls each of which contains a plurality of transverse apertured bulkheads forming a plurality of intercommunicating compartments, a hollow body disposed between the hulls and having a smaller draught than the hulls, the hollow body including a generally flat bottom surface at least a portion of which is perforated such that a mixture of said pollutant and said liquid can enter the body therethrough in use, the interior of the hollow body communicating with the foremost compartment in each hull with respect to the direction of travel of the craft, and suction means arranged to apply a suction effect to the rearmost compartment in each hull, such that said mixture of pollutant and liquid is drawn in use from said foremost to said rearmost compartment through the remainder of the compartments in each hull, whereby the pollutant is skimmed from the liquid by the apertures in the bulkheads and accumulates in said compartments.

In a particular example of the invention, mutually facing side portions of the hulls and the bottom surface of the hollow body form a passage through which the pollutant (e.g. oil) and the liquid (e.g.

water) are channelled as the craft travels forwardly.

The pressure of the water acting on the bottom surface of the hollow body forces the water and oil through the perforations in the latter at a pressure which is proportional to the draught of said bottom surface. From the interior of the hollow body, the water and oil are sucked successively through the compartments in each hull and apertures in lower portions of the bulkheads act to skim the oil from the water, the oil becoming accumulated in the upper regions of the compartments.

By this skimming action, water which is practically oil-free reaches the rearmost compartment in each hull. This water is then pumped to an immersed ejector in the bow portion of the craft where it is expelled rearwardly into the aforementioned passage. The water is thus recycled through the passage, enabling any oil remaining therein to be removed. Such rearward expulsion also imparts a slow forward propulsion to the craft and increases the flow through the passage. Propulsion units can be provided in the sterns of the hulls to ensure motion of the craft at normal speeds.

An embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure l is an underneath sectional plan view of a craft according to the present invention, the section being taken along the line I-I in Figure 4; Figure 2 is a longitudinal sectional view of the craft taken along the line ll-ll in Figure 1; Figure 3 is a longitudinal sectional view of the craft taken along the line Ill-Ill in Figure 1; Figure 4 is a sectional end view of the craft taken along the line IV-IV in Figure 1; Figure 5 is a longitudinal sectional view of part of a modified form of craft, also according to the present invention; and Figure 6 is a top plan view of the bows of the craft illustrating in particular two extension flaps.

The oil skimming craft shown in the drawings is in the form of a catamaran and comprises two parallel, laterally spaced apart hulls or floats 1 and 2 which are bridged and interconnected by a flat-bottomed central body 3 of lesser draught than the hulls. The hulls are located relatively close to each other and, together with a perforated bottom surface 4 of the central body 3, form a narrow passage 5. For an optimum skimming effect, the draught of the central body should be approximately 10 to 30 cm. below the full load line of the hulls 1 and 2.

As the craft travels along the surface of an oil-polluted body of water, the water and the polluting hydrocarbon floating on its surface are channelled between the stems of the hulls and into the aforementioned passage 5. The pressure of water acting upon the bottom surface 4 causes the oil and some of the water to pass through the perforations in the surface 4.

As is shown to advantage in Figures 3 and 4, the perforations take the form of six gratings which are arranged in two lines of three, each grating forming the bottom of a respective skimming or suction tank 6. The gratings can be flat and iie flush with the bottom surface 4 (as shown in Figures 3 and 4), or can have a hydrofoil profile and project below the bottom surface 4 (as shown in Figure 5). Each tank 6 is of pyramidal shape, and the tanks in each line have their tops connected in series by a respective suction pipe 7.

Each of the hulls 1 and 2 contains an airtight hold 10 which is divided into a plurality of compartments by transverse bulkheads 11. The foremost compartment in each hull has disposed therein an outlet from the suction pipe 7 associated with the adjacent row of tanks 6. The rearmost compartment in each hull is connected by a respective pipe 8 to the suction side of a pump 9 installed in the stern of the body 3. An aperture 12 is provided in each bulkhead 11,sothatthe compartments in each hull all intercommunicate. The suction effect applied by the pump 9 to the rearmost compartment is thus transmitted through the remaining compartments in each hull and through the respective suction pipe 7 to the respective suction tanks 6.

Each aperture 12 is provided in a lower side portion of its respective bulkhead 11,the apertures 12 in successive bulkheads being transversely stag gered. Owing to this dispostion of the apertures 12, the suction pump 9 causes the oil and water to flow from the tanks 6 through the pipes 7 into the foremost compartment in each hull and thence in an undulating path from stem to stern through the successive compartments, as indicated by arrows in Figure 1, before it is sucked through the pipes 8 into the pump 9. The delivery side of the pump 9 is connected to two pipes 13 which run atop the hulls respectively and which terminate respectively at either end of an immersed ejector 14 which bridges the bows of the two hulls 1 and 2.

During its flow through the hulls, the water has the oil skimmed therefrom by the upper edges of the apertures 12, so that separation of the oil from the water is accomplished in sequence between successive compartments. Therefore, oil will accumulate first in the foremost compartment in each hull (more particularly, in an upper region thereof above the upper edge of the respective aperture 12) and, once this region is filled with oil, any successively inflowing oil will spill through the aperture and flow into the upper region of the next compartment, and so on, so that practically clear water will enter the intake ofthe suction pipe 8 in each hull.

The oil accumulated in the compartments can be evacuated therefrom through valves provided in the ceiling of the respective hold by any known and therefore not illustrated means. Once the oil skimming cycle has been completed and the oil has been removed from the holds, the craft is ready to resume its operation.

During forward motion of the craft, a deadwater zone will form astern of it, into which are drawn oily wastes which flow around the exterior of the craft.

This zone can be cleared by any conventional oil suction system (not shown).

As already mentioned, practically oil-free water should be present at the intake of each pipe 8, and this water is conveyed by the pipes 13 to the ejector 14. A row of ports is provided in a rear edge of the ejector, through which the water from the pipes 13 is expelled rearwardly of the craft and into the passage 5, thereby imparting slow hydraulic propulsion to the craft. The ejector 14 is rotatable about its axis so that the direction in which the water is expelled can be adjusted. Any residual oil which has not been separated from the water during its flow through the compartments is thereby recycled into the craft for a further skimming treatment.

Normal propulsion of the craft is provided by conventional propulsion units 15 installed in the sterns of the hulls.

As shown at 16 in Figure 5, to improve the skimming efficiency of the craft, the gratings form ing the bottoms of the suction tanks 6 can be given a hydrofoil profile and can project below the bottom surface 4 of the central body 3. This has the effect of increasing the liquid pressure upon the gratings and consequently the liquid volume passing therethrough.

The suction effect of the tanks 6 can be further increased by making the trailing edges of the gratings 16 of truncated and perforated configuration.

Vertical flaps 17 are hinged to the stems of the hulls 1 and 2, as shown in Figure 6. When rotated forwardly and fixed in the divergent positions shown in this figure, the flaps 17 considerably increase the area of the inlet into the passage 5, with the effect that a much larger surface layer of oil-polluted water is channelled into said passage for treatment by the craft. The flaps 17 have the same curvature as the external tanks of the bow to which they are hinged, so that in their retracted positions they lie flush with the bows and do not increase the resistance of the craft. These flaps can be rotated and fastened into their operative and inoperative positions by any suitable manual or mechanical means (not shown).

As shown in Figure 5, illuminated spyholes 18 are provided in the walls of the suction tanks 6, and enable the quality and quantity of the oil/water mixture flowing through the tanks to be observed.

These two factors can be controlled by adjusting the speed of the craft andíor the speed of the pump 9, or by varying the number of the suction tanks in operation by meansofshut-offvalves (not shown) inserted in the connections between the tops of the tank 6 and the respective pipes 7.

The optimum width of the passage 5 has been found to be approximately one quarter of the total breadth of the craft. The capacity of the pump is approximately 500 m3 per hour. The craft can be easily modified to operate on dry land, between low tides, sandy beaches and coral reefs.

Claims

1. A craft for skimming pollutants from the surface of a liquid, comprising two hulls each of which contains a plurality of transverse apertured bulkheads forming a plurality of intercommunicating compartments, a hollow body disposed between the hulls and having a smaller draught than the hulls, the hollow body including a generally flat bottom surface at least a portion of which is perforated such that a mixture of said pollutant and said liquid can enter the body therethrough in use, the interior of the hollow body communicating with the foremost compartment in each hull with respect to the direction of travel of the craft, and suction means arranged to apply a suction effect to the rearmost compartment in each hull, such that said mixture of pollutant and liquid is drawn in use from said foremost to said rearmost compartment through the remainder of the compartments in each hull, whereby the pollutant is skimmed from the liquid by the apertures in the bulkheads and accumulates in said compartments.

2. A craft as claimed in claim 1, wherein at least one suction tank is provided in the hollow body and is connected to said foremost compartments by pipe means, the or each suction tank having a bottom wall which is constituted by a respective perforated portion of said bottom surface of the hollow body.

3. A craft as claimed in claim 1 or 2, wherein the apertures in successive bulkheads are mutually staggered transversely of the respective hull.

4. A craft as claimed in claim 1,2 or 3, wherein the apertures are provided in lower side portions of each bulkhead.

5. A craft as claimed in any preceding claim, wherein mutually facing side portions of the hulls and said bottom surface of the hollow body together form a passage through which the pollutant and the liquid is channelled during forward travel of the craft.

6. A craft as claimed in claim 5, wherein the width of the passage is approximately one quarter of the distance between outwardly-facing side surfaces of the hulls.

7. A craft as claimed in any preceding claim wherein the or each perforated portion of the hollow body bottom surface is in the form of a grating which is of hydrofoil profile having a truncated trailing edge and which projects below the remainder of the bottom surface of the hollow body.

8. A craft as claimed in any preceding claim wherein the suction means comprises a pump disposed at an aft end of the hollow body and pipes connected between said rearmost compartments and a suction side of the pump.

9. A craft as claimed in any preceding claim, further comprising ejector means arranged to receive said liquid from the rearmost compartment and to eject said liquid rearwardly of the craft, the ejector means being immersed in use so that said ejection of the liquid imparts a forward motion to the craft.

10. A craft as claimed in claim 9 when appended to claim 8, wherein the ejector means is connected to a delivery side of said pump so as to receive said liquid therefrom.

11. A craft as claimed in claim 9 when appended to claim 5, wherein the ejector means bridges the bows of the hulls and is arranged to eject said liquid into said passage.

12. A craft as claimed in claim 9, 10 or 11, wherein the ejector means is composed of a member having a row of ports in a rearwardly-facing portion thereof through which said liquid is ejected in use, the member being rotatable relative to the hulls to vary the direction of said ejection.

13. A craft as claimed in any preceding claim, wherein a pair of flaps are hinged respectively to stems of the hulls and are movable between positions in which they are generally flush with the respective hulls and positions in which they extend rearwardly of and diverge from the hulls.

14. A craft for skimming pollutants from the surface of a liquid, substantially as hereinbefore described with reference to Figures 1 to 4 and 6, or Figures 1 to 4 and 6 as modified by Figure 5 of the accompanying drawings.