GB2066687A

GB2066687A - Oil skimming vessel

Info

Publication number: GB2066687A
Application number: GB8040961A
Authority: GB
Original assignee: BP PLC
Current assignee: BP PLC
Priority date: 1980-01-02
Filing date: 1980-12-22
Publication date: 1981-07-15
Also published as: GB2066687B

Abstract

A craft for removing oil from the surface of water has a flap 7, 8 over which the surface layer enters the hull and a pump to eject water subsequently separated from oil within the hull, thus inducing the flow of oil and water over the flap. The flap articulated, comprising a first non-buoyant section 7 pivoted at one end to the hull and a second buoyant section 8 pivoted to the other end of the non-buoyant section and having a free floating end. A winch 10 has chains 9 connected to section 7 for adjusting it to suit wave conditions. <IMAGE>

Description

SPECIFICATION Apparatus for removing floating oil from the surface of oil polluted water The present invention relates to an apparatus suit able for removing floating oil and other material from the surface of oil polluted water.

British Patent Specification 1530342 discloses and claims a craft capable of floating on oil polluted water having an opening through which surface water and oil can enter a compartment within the craft over a float controlled hinged or articulated flap lying in the direction of flow of the surface water and oil, said flap being arranged to allow flow into the compartment but to prevent free flow in the opposite direction, the float control of the flap lying within the compartment, the position of the free edge of the flap being determined by the level of the water and oil in the compartment, so arranged that in use the position of the free edge of the float controlled flap will preferentially allow surface water and oil to flow into the compartment, and the craft having means to eject water separated from oil from the compart ment to the body of water on which the craft floats, by means of a pump or pumps capable of inducing a flow of water and oil into the craft and ejecting water out of the craft.

We have now discovered that by suitably modify ing the flap it is possible to achieve greater control over the recovery of oil floating on the surface of water.

Thus, according to the present invention, a craft suitable for removing oil from the surface of water having an opening through which surface oil and water can enter a compartment within the craft over a flap lying in the direction of flow of the water and oil, the flap being arranged to allow flow into the compartment but to prevent free flow in the opposite direction, the craft having means to eject water, separated from the oil, from the compartment to the body of water on which the craft floats by means of a pump or pumps capable of inducing a flow of water and oil into the craft and ejecting water out of the craft is characterised in that the flap is an articulated flap comprising a first non-buoyant section pivoted at one end to the craft at the base of the opening and a second buoyant section pivoted at one end to the other end of the non-buoyant section and having a free floating end, the non-buoyant section being suf ficiently heavy to counteract the buoyancy of the buoyant section and having control means attached thereto to position the end of the non-buoyant sec tion to which the buoyant section is pivoted, the pos ition of the free end of the buoyant section being -determined by the level of oil and water in the com partment and so arranged that in use the position of the free end of the buoyant section of the flap allows surface water and oil to flow into the compartment, the total length of the flap being at least equal to the distance between the bottom of the opening, to which the flap is pivoted, and the water-line of the craft.

The length of the non-buoyant section of the flap is preferably almost, but not quite, equal to the distance between the bottom of the opening and the water-line of the craft.

The non-buoyant section is sufficiently heavy to counteract the buoyancy of the buoyant section and so, unless a means of controlling the position of the non-buoyant section is provided, it will not rotate about its pivot with the opening until the end attached to the buoyant section reaches its lowest attainable position. Suitable control means include chains, wires or ropes suspended from a winch mounted on the craft and attached to the nonbuoyant section, preferably at or near the pivoted joint to the buoyant section.

The length of buoyant section plus the length of the non-buoyant section is at least equal to the distance between the bottom of the opening and the water-line of the craft so that when the level of water inside the craft is equal to the water level outside the craft, i.e. no water is being pumped out of the craft, then the flap will, when in a vertical position, reach or rise above the water surface thus preventing the flow of oil and water out of the craft.

The pivoted joints between the opening and the non-buoyant section of the flap and between the buoyant section and the non-buoyant section of the flap may be in the form of hinges.

The craft is suitably a barge having the opening at its front end. The craft has a compartment in which water and oil flowing through the opening over the articulated flap is collected. In addition the craft suitably contains storage tanks for recovered oil and ballast tanks which can be filled with water or oil in order to control the depth of the craft in water either when it is in operation or when it is moving either undertow or under its own power.

The compartment within the craft for the water and oil may be covered or open. Craft having covered compartments can be made by adapting oil tankers using the existing tanks and modifying the bow section to make the opening.

Baffles may be provided within the compartment in the craft to receive the water and oil flowing over the flap. If the baffles are suitably positioned, they can facilitate the separation of oil and water entering the compartment.

A pump or pumps are preferably provided within the craft to eject water separated within the compartment back into the body of water on which the craft floats. Suitably these pumps withdraw water from the bottom of the compartment and their outflow is arranged to discharge back into the body of water on which the craft floats so that there is minimum back pressure on the pumps in operation.

When the craft is in use on oil polluted water the control means may be adjusted until the nonbuoyant section is at the required position and the buoyant section floats with its free floating end at or nearthe surface of the water. The operation of the pumps results in a fall in the level of water within the craft and the free end of the buoyant section of the flap falls correspondingly. This creates a weirwhich induces the flow of oil and waterthrough the opening and into the compartment of the craft.

A change in the position of the non-buoyant section will result in a change in the angle at which the buoyant section floats. By changing the position of the non-buoyant section, the effective depth of the opening of the craft may be varied infinitely between a maximum and minimum. Thus, the depth of oil and water skimmed by the craft may be varied to suit the prevailing conditions, e.g. the turbulence of the water surface and the nature of the oil, for increased recovery.

When water is not being removed from the com partment the liquid level therein rises and the free floating edge of the buoyant section of the flap also rises thus preventing the free flow of water and oil out of the craft, i.e. it shuts off the opening in the craft.

Oil separating in the compartment can be pumped into storage tanks within the craft. As stated above, such separated oil can be fed to the ballasttanks which control the buoyancy of the craft. As the separated oil is pumped into the tanks water can be expelled from the bottom of the tanks and thus there is little change of buoyancy in the craft as a whole as the collection process proceeds.

A single articulated flap may extend across the opening of the craft, but with large craft it is preferable to have a series of flaps effectively covering the whole opening. This gives rise to increased efficiency when the craft is operated under rough conditions and enables the craft to continue in operation even if one flap is damaged and has to be locked in a closed position. When more than a single flap is used corresponding vertical baffles may be provided within the compartment to prevent unnecessary mixing of oil and water therein. These may be perforated and need not extend eitherthe whole length or depth of the compartment.

An advantage of craft according to the present invention is that not only can they remove and retain oil from the surface of water, but also they can remove and retain other materials, e.g. flotsam such as wood. When such flotsam approaches the flap its weight forces the flap to open and it can pass over into the compartment. Once over the flap the latter immediately takes up its previous position and prevents excess surface water flowing into the compartment.

The invention is illustrated with reference to Figures 1 and 2 of the accompanying drawings which are schematic representations of a barge fitted with an articulated flap for removing oil floating on the surface of water.

The side walls (1 ) of the barge enclose a central compartment (2) which is bounded at the rear by the stern (3) of the barge and at the front by a bow section (4). The top edge of the bow section (4) forms a sill (5) at the base of an opening (11) in the barge.

The sill (5) is designed to be below the water surface (6) when the barge is in operation, so that oil and water may pass through the opening (11) into the compartment (2). An articulated flap is hinged to the sill (5) at the base of the opening (11).

The flap comprises a first non-buoyant section (7) hinged at one end to the sill (5) and a second buoyant section (8) hinged at one end to the other end of the non-buoyant section and having a free floating end. The non-buoyant section (7) is suffi ciently heavy to counteract the buoyancy of the buoyant section (8). Chains (9) suspended from a winch (10) mounted on the deck of the barge are attached to the non-buoyant section (7) near to the hinged joint to the buoyant section (8).

In Figure 1, the solid lines depict the position of the flap in the "fully down" position, with the non buoyant section (7) substantially horizontal giving the maximum depth ofthe opening (11). Broken lines depict the position of the flap in an intermediate position and in the "fully up" position with the non-buoyant section (7) substantially vertical, giving the minimum depth of the opening (11). Preferably means (not shown) are provided either within the hinging mechanism with the sill (5) or in the form of mechanical obstructions, to prevent the nonbuoyant section rotating beyond the vertical or horizontal positions shown.

When the vessel is in use the position of the nonbuoyant section is selected to give an effective depth of the opening (11) best suited to the prevailing conditions, such as the turbulence of the water surface and the nature of the oil. The buoyant section (8) floats with its free floating end at or near the water surface. Water separated from oil is withdrawn from near to the bottom of the compartment (2) by pumps (not shown) and discharged back into the body of water on which the craft floats. Operation of the pumps results in a fall in the level of the water within the compartment (2) and the free floating end of the buoyant section falls correspondingly. This creates a weir and induces the flow of oil and water into the compartment (2).

The length of the non-buoyant section (7) is almost, but not quite, equal to the distance between the sill (5) and the expected water level (6) outside the craft and so even when the non-buoyant section (7) is substantially vertical, water and oil may flow into the device. The total length of the flap is greater than the distance between the sill (5) and water level (6). Thus, when the water level inside the compartment (2) rises, the buoyant section rotates about the hinged joint with the non-buoyant section, until the buoyant section rises above the water surface and closes the opening (11 ) preventing the free flow of oil and water out of the compartment (2). Preferably means (not shown E are provided to prevent the buoyant section rotating past the vertical, i.e. the angle between the non-buoyant section (7) and the buoyant section (8)is preferably greater than or equal to 90 .

Claims

1. A craft suitable for removing oil from the sur: face of water having an opening through which surface oil and water can enter a compartment within the craft over a flap lying in the direction of flow of i the water and oil, the flap being arranged to allow flow into the compartment but to prevent free flow in the opposite direction, the craft having means to eject water, separated from the oil, from the com partmentto the body of water on which the craft floats by means of a pump or pumps capable of inducing a flow of oil and water into the craft and ejecting water out of the craft is characterised in that the flap is an articulated flap comprising a first non buoyant section pivoted at one end to the craft at the base of the opening and a second buoyant section pivoted at one end to the other end of the nonbuoyant section and having a free floating end, the non-buoyant section being sufficiently heavy to counteract the buoyancy of the buoyant section and having control means attached thereto to position the end of the non-buoyant section, to which the buoyant section is pivoted, the position of the free end of the buoyant section being determined by the level of oil and water in the compartment and so arranged that in use the position of the free end of the buoyant section of the flap allows surface water and oil to flow into the compartment, the total length of the flap being greater at least equal to the distance between the bottom of the opening, to which the flap is pivoted, and the water-line of the craft.

2. A craft according to claim 1 in which the length of the non-buoyant section is almost, but not quite, equal to the distance between the bottom of the opening and the water-line of the craft.

3. A craft according to either of claims 1 or 2 in which the control means for the non-buoyant section of the flap comprises a winch mounted on the craft and connected by chains, wires or ropes to the nonbuoyant section of the flap at or near to the pivoted joint with the buoyant section.