GB2231281A

GB2231281A - Oil pollution control

Info

Publication number: GB2231281A
Application number: GB9008476A
Authority: GB
Inventors: Hugh Robert Asquith Fish
Original assignee: Individual
Current assignee: Individual
Priority date: 1989-04-12
Filing date: 1990-04-12
Publication date: 1990-11-14
Also published as: GB9008476D0

Abstract

A pollution control device comprises a rectangular sheet 4 having buoyancy devices 6 along a central longitudinal zone and weights 5 on its edges. When the sheet 4 is deployed over an oil slick 7, for example, from a raft 3 towed behind a towing vessel 1, the weighted edges sink, entrapping the oil 7 within the sheet between the downwardly folded edges and the buoyant central zone, whereupon the entrapped oil can be recovered with the sheet. The sheet is of textile material pervious to air but not oil. Raft 3 is of catamaran construction. Weights 5 may be replaced by a single weight attached by lines to points on the sheet periphery. <IMAGE>

Description

OIL POLLUTION CONTROL This invention relates to pollution control and, more particularly, to containing and recovering oil and other pollutants floating on water.

Current methods of reducing the environmental impact of large oil spill accidents include the use of containment booms, spraying with detergent, incineration in situ, and separation with skimmers. One problem with oil spills is that the oil rapidly spreads thinly over the water. Whilst encircling with floating booms should control the spread and stop the oil slick from beaching, booms tend to leak underneath, and surface winds and currents make them difficult to hold. Vast lengths of boom are often required to encircle a slick, and the booms need to be enormously strong, and are therefore very heavy and expensive. Frequently, there are not enough booms available in an emergency.

The present invention consists in an oil pollution control device comprising a sheet or blanket for containing oil or other pollutants floating on water, in which the sheet has a central zone which is adapted to float, and a periphery which is weighted so as to sink whereby, when the sheet is deployed in a flat and extended condition over a floating pollutant, the periphery of the sheet sinks into the water and folds downwardly about the central floating zone to entrap the pollutant within the folded sheet and under the floating zone of the sheet.

The sheet or blanket should be lightweight and may be circular, rectangular or square in plan, with small dense weights about its periphery or having means connecting its periphery to a central weight in the manner of a parachute. The sheets may be deployed from boats, hovercraft or aircraft, such as helicopters, in such a way that they are deposited flat over an area of floating pollutant. They may have aerodynamic characteristics so that, when they are unfurled from a transporting vessel, they spread out evenly behind the vessel in a horizontal streaming mode.

When deployed, the edges of the sheets settle in the water around the central buoyancy, retaining the floating pollutant in the resulting shroud. The sheet may be made of strips or segments of different materials, to give the best characteristics in both the horizontal streaming mode, the settling mode, and the shroud mode. The placement and distribution of edge weights may be augmented by secondary weights and buoyancy spots over the area of the sheet to assist in deployment behaviour. The resulting shroud has only a small area at surface level and is easy to hold in position in the water and control and, eventually, collect together with similar shrouds, if convenient, to be lifted onto a barge or towed away for incineration and disposal.

Tests have indicated that the best shape for such a sheet is an elongated rectangle having a row of buoyancy aids or devices disposed generally along a longitudinal centre zone of the sheet and a weighted periphery. Preferably, it has at least its longitudinal edges weighted so as to sink and entrap pollutants between opposite longitudinal portions folded downwardly about the central floating zone.

The sheet may be made from nylon, silk or other textile material. The material may be porous to air, but not to oil, so that any air trapped as the sheet is deployed on the surface may escape.

Conveniently, a multiplicity of weights are attached at intervals about the periphery of the sheet.

Additional weights may be distributed over the area of the sheet to assist in deployment behaviour. Alternatively, there may be a central weight attached by lines to spaced positions about the edge of the sheet in the manner of a parachute.

The sheet is conveniently deployed from a raft towed by a towing vessel. The vessel is preferably a trawler or vessel of similar size. To facilitate deployment from the raft, the sheet may be supported in a suitably folded condition on the raft, for example, in a zig-zag or pleated configuration. Thus, when one end is released onto the surface, the sheet may be dragged from the raft, unfolding gradually onto the surface of the water as the raft is towed over the pollutants to be collected.

The sheet may be of any suitable size. For example, where a square sheet is utilised it may be 40m square. Where it is of the preferred rectangular shape, it may be about 10m wide and 50m long. Up to 100 of such sheets may be deployed for an average size oil spill.

In order that the present invention may be more readily understood, reference will now be made to the accompanying drawings, in which: Figure 1 is a side view of a vessel towing a raft carrying a pollution control sheet according to the invention for deployment on a floating oil slick, Figure 2 is a plan view of Figure 1, Figure 3 is an end view of the raft of Figure 1, Figure 4 is a side view of the vessel during initial deployment of the sheet, Figure 5 is a plan view of Figure 3, Figure 6 is a cross-sectional view of Figure 4, Figure 7 is a side view of the vessel at a later stage of deployment of the sheet, Figure 8 is a plan view of Figure 5, and Figure 9 is a cross-sectional view of Figure 5.

Referring to Figures 1, 2 and 3, a towing vessel 1 is attached by tow lines 2 to a deployment raft 3 on which a folded rectangular sheet 4 is supported. The sheet 4 is of a textile material, such as nylon or silk, and is about 50m long and 10m wide. It is weighted at its periphery with small steel balls 5, which are attached at intervals around its edge. It also has buoyancy envelopes 6 disposed at intervals along the region of its longitudinal centre line. The sheet 4 is folded back and forth transversely between each buoyancy envelope 6, in a pleated fashion.

The towing vessel tows the raft into the vicinity of an oil slick 7 which is to be collected. In the example illustrated, the slick 7 is narrow and the raft 3 is a twin hull vessel in which the platform supported between the hulls is able to span the width of the slick.

When the raft 3 reaches a position adjacent one end 10 of the slick 7, the free end 11 of the sheet 4 is released onto the surface of the water behind the raft 3. As shown in Figures 4, 5 and 6, as the vessel moves over the slick 7, the folds of the sheet 4 are successively dragged onto the surface in a flat condition to deploy the sheet over the slick. The weighted edges then begin to sink below the surface. The buoyancy envelopes 6 retain the centre zone of the sheet 4 floating on the surface, and the oil slick 7 is urged into the centre of the sheet 4 under the floating zone as the edges and ends of the sheet fold down to envelope the oil.

When the edges have fully settled (Figures 7, 8 and 9), the sheet 4 is folded downwardly about opposite sides and ends of the floating central zone and forms a shroud entrapping the oil. It may now be removed together with the oil for disposal in any convenient manner.

Whilst a particular embodiment has been described it will be understood that modifications can be made without departing from the scope of the invention as defined by the appended claims. For example, the sheets may be deployed from a ship, using explosives. In this instance, smaller sheets could be provided, say, of the order of 16my. In another mode of deployment, the sheets may be streamed between two ships.

Claims

1. A pollution control device comprising a sheet or blanket for containing oil or other pollutants floating on water and having buoyancy generally at or adjacent a central zone of the sheet and being weighted at or adjacent its edges.

2. A pollution control device as claimed in claim 1, in which the sheet is of rectangular shape in plan, the buoyancy is disposed generally along a longitudinal central zone at least the longitudinal edges of the sheet are weighted.

3. A pollution control device as claimed in claim 1 or 2, in which the sheet is made from nylon, silk or other textile material.

4. A pollution control device as claimed in claim 1, 2 or 3, in which the sheet is made from a material which is porous to air but not to oil.

5. A pollution control device as claimed in any one of the preceding claims, in which the edges are weighted with a multiplicity of weights distributed at intervals about the periphery of the sheet.

6. A pollution control device as claimed in any one of the preceding claims 1 to 4, in which the edges are weighted by means of a central weight attached by lines to spaced positions about the periphery of the sheet.

7. A pollution control device substantially as described herein, with reference to the accompanying drawings.

8. A method of containing and recovering oil or other pollutants floating on water, comprising the steps of: providing at least one sheet or blanket having buoyancy generally at an adjacent or central zone and being weighted at or adjacent its periphery, transporting the sheet(s) to the required site, deploying the sheet(s) in an extended condition over the floating pollutant, at the site, allowing the weighted periphery of the or each deployed sheet to sink and entrap pollutant within the sheet under the floating buoyancy zone, and recovering the sheet(s) with the entrapped pollutant.

9. A method as claimed in claim 8, in which the or each sheet is deployed from a raft towed by a towing vessel.

10. A method as claimed in claim 9, in which the or each sheet is carried on the raft folded in a zig-zag or pleated fashion with the folds or pleats extending transversely to the towing direction, thereby to enable water drag on the sheet to assist deployment of the sheet behind the raft as it is being towed.

11. A method of containing and recovering oil or other pollutants floating on water, substantially as hereinbefore described.