GB2046236A - Agitator for oil pollution dispersal - Google Patents

Abstract

An agitator for oil pollution dispersal comprises a net (17) mounted between forward and aft support frames (18 and 19) which is towed through the water behind a spray boom (11). Stowing lines (24) passing through the forward frame (18), woven through the net (17) and secured to the aft frame (19) assist in deployment and recovery; when drawn in the stowing lines (24) bring the aft and forward frames (18 and 19) together with the net (17) folded between them. <IMAGE>

Description

SPECIFICATION Improvements in or relating to oil pollution dispersants This invention relates to oil pollution dispersant agitators, that is to say devices for break ing-up the surface of oil carrying water to assist the action of previously sprayed on dispersants.

Oil pollution dispersant agitators are known, usually being towed aft of a spray boom extending transversely of the oil dispersent vessel and through which oil dispersant is sprayed onto the oil carrying water. Conventional agitators which are also referred to as surface breakers comprise slatted boards towed with the boards parallel to the spray boom and at right angles to the direction of motion of the vessel. The surface breaker boards have an inherent buoyancy and are usually operated in sets of two or three units lashed together to provide an overall width of about 1 2 feet. Each surface breaker board unit comprises five or seven spaced apart parallel boards supported between two end beams which lie in line with the direction of motion of the vessel and by which the units are towed.

The conventional surface breaker boards are cumbersome to handle and take up a lot of space in the working area on board the vessel. Furthermore delivery and recovery of the surface breaker boards is a slow and laboursome task which is expensive in manpower; it is also necessary for the vessel to heave to during recovery.

It is an object of the present invention to provide an oil pollution dispersant agitator which is light, compact and easy to handle and which is efficient in use.

According to the present invention an oil pollution dispersent agitator for towing behind a spray boom comprises a net secured along its forward region to a forward support frame by which in use it is towed through the water.

Preferably the net is also secured along its aft edge to an aft support frame. Forward and aft support frames may conveniently be in the form of buoyant tubing eg aluminium tubes sealed at their ends. The forward support frame tube is preferably of larger cross-section than the aft support frame tube.

The forward support frame may be secured to the spray boom by two towing lines each set a short distance in from the ends of the tube.

In one embodiment of the invention means are provided for stowing the net, the means being capable of bringing together the forward and aft support frames. The means preferably, comprise at least two recovery lines extending in use from the spray boom and secured to the aft support frame, the lines passing weft-like through the deployed net such that movement of the lines relative to the forward frame draws the aft frame towards the forward frame with the net folded therebetween. Conveniently the lines extend slidably through passageways in the forward support frame. The recovery lines in use pass through pulley blocks secured to the spray boom whereby deployment and stowing of the net can be effected from onboard the spraying vessel.Furthermore during recovery continued drawing in of the recovery lines after the aft support frame has been brought into contact with the forward support frame draws the stowed assembly of net and frames towards the spray boom from where it can be easily recovered.

The net of the invention can be of varying dimensions to suit particular circumstances although a net of approximately 1 3 feet width and 9 feet length having a 4 inch square mesh has been found particularly effective.

An embodiment of the invention will now be described by way of example only with reference to the accompanying drawing which shows in plan view an oil pollution dispersant agitator of the invention.

The agitator which is referred to generally as 10 is shown in a deployed condition aft of a spray boom 11 extended transversely of a spraying vessel 1 2. The spray boom 11 is of conventional construction and design in that it is pivotally mounted at 1 3 to enable it to be swung from being in line with the spraying vessel 1 2 to the position shown transverse of the spraying vessel 1 2. In the operational position it is retained by forward and aft guy members 14 and 1 5 and is retained parallel to the plane of the deck by means of a topping lift guy 1 6 secured to a vertical mast member (not shown) located adjacent the pivot mounting 13.

The agitator 10 comprises a net 17, a forward support frame tube 1 8 threaded through the forward row of the mesh and an aft support frame tube 1 9 similarly threaded through the aft row of mesh. The tubes 1 8 and 1 9 are sealed at their outer ends to render them buoyant. The net 1 7 is secured to the forward and aft support frame tubes 1 8 and 1 9 by means of securing lugs 20 located near the end of each tube member.

Main towing lines 21 having thimble eyed ends connect with lugs 22 and 23 on the forward support frame 1 8 and spray boom 11 respectively. In board of the main towing lines 21 are recovery lines 24 which pass through sealed passageways 25 in the forward support frame 1 8 from where they are threaded weftlike through the net 1 7 and secured to lugs 26 on the aft securing frame 19. Forward of the agitator 10 the recovery lines 24 pass through pulley blocks 27 mounted on the spray boom 11 after which they are fed to a block tackle on the mast (not shown).

Operation of the agitator 10 is controlled essentially by the recovery lines 24. The agitator 10 is stowed with the recovery lines 24 taut and the forward and aft support frames 1 8 and 1 9 brought together. The assembly of the net 1 7 and forward and aft support frames 1 8 and 1 9 is then positioned adjacent the spray boom 11 and maintained in this position by the recovery lines 24. With the towing lines 21 connected the spray boom 11 is swung out into its operative position and the various guy lines 14, 1 5 and 1 6 secured.

The recovery lines 24 are then let out to initially lower the assembly to the water line.

With forward motion of the spraying vessel 1 2 the drag of the agitator 10 in the water will tighten the main towing lines 21 whilst continued letting out of the recovery lines 24 will cause the agitator 10 to deploy such that the aft support frame 1 9 trails behind with the net 1 7 in a substantially horizontal condition.

The height of the spray boom 11 above the water and the length of the main towing lines 21 will, with the spraying vessel 12 moving forward, cause the forward support frame 1 8 and a forward region of the net 1 7 to ride slightly out of the water.

Recovery of the agitator 10 is equally as straightforward and can be performed whilst the spraying vessel 12 is underway. The recovery lines 24 are drawn in to initially bring the aft support frame 1 9 towards the forward support frame 18 whereafter the assembly of the net 1 7 and the support frames 1 8 and 1 9 is pulled forward towards the spray boom 11.

Once clear of the water the spray boom 11 and the agitator assembly can be swung alongside the spraying vessel 1 2 and finally recovered.

The net 1 7 of the agitator 10 as tested was made of 1 '/8 inch plaited terylene net 1 3 feet wide by 9 feet long with a 4 inch square crimped mesh. Used Naval flight deck safety nets or cargo nets have been found eminently suitable. The forward support frame 18 was a 3 inch diameter aluminium tube whilst the aft support frame 1 9 was a 1 + inch diameter aluminium tube. The main towing lines 21 were of 10 mm wire shackled to the lugs 22 which were set 1 8 inches in from the ends of the frame 1 8. The recovery lines 24 were of 1 '/8 inch nylon connected to the lugs 26 which were set 3 feet in from the ends of the support frame 1 9.

With the agitator of the invention it is possible for two men to complete the entire recovery operation with the spraying vessel underway at slow speed. However recovery whilst underway is partly determined by the strength of the spray boom and mast and if these are of adequate strength and a suitable reduction tackle was inserted in the recovery lines 24 it is expected that the agitator could be recovered even with the spraying vessel steaming at maximum spraying speed.

Agitation of the water surface by the agitator of the invention is considerably improved when compared with conventional surface break of boards used in similar sea conditions and towing speeds.

It will be appreciated that the invention is not limited by the specific embodiment and that the broad principle of employing a flexible net-like layer of material can be used in alternative designs.

Claims (9)

1. An oil pollution dispersant agitator comprising a net secured along its forward region to a forward support frame by which in use it is towed through the water.

2. An oil pollution dispersant agitator as claimed in claim 1 in which the net is also secured along its aft edge to an aft support frame.

3. An oil pollution dispersant agitator as claimed in claim 1 or 2 in which the support frames are in the form of buoyant tubing.

4. An oil pollution dispersant agitator as claimed in claim 2 or 3 in which the forward support frame tube is of larger cross-section than the aft support frame tube.

5. An oil pollution dispersant agitator as claimed in claim 2, 3 or 4 in which means are provided for stowing the net, the means being capable of bringing together the forward and aft support frames.

6. An oil pollution dispersant agitator as claimed in claim 5 in which the means comprises at least two recovery lines secured to the aft support frame, the lines passing weftlike through the deployed net such that movement of the lines relative to the forward frame draws the aft frame towards the forward frame with the net folded therebetween.

7. An oil pollution dispersant agitator as claimed in claim 6 in which the lines extend slidably through passageways in the forward support frame.

8. An oil pollution dispersant agitator as claimed in claim 6 or 7 in which the recovery lines in use pass through pulley blocks secured to a spray boom whereby continued drawing in of the recovery lines after the aft support frame has been brought into contact with the forward support frame draws the stowed assembly of net and frames towards the spray boom from where it can be easily recovered.

9. An oil pollution dispersant agitator substantially as hereinbefore described with reference to the accompanying drawing.