The present invention relates to a method and a device for collection of oil or the like floating on water, wherein a boom is towed or moored in a current so that it forms a bend where the oil or the like is collected and removed by means of at least one suitable skimming device.

When collecting offshore oil spills by means of booms one has learned that if the relative velocity, between the boom and the water exceeds 1 - 1,5 knots, the rise occuring in the bend of the boom will result in water and oil being forced down under the boom so that substantial amounts of oil will escape before it can be removed. This means that usual oil booms and collection equipment in many cases cannot be utiliz to restrict offshore oil spills since the current velocity easily may be 3 knots or more. The same problem will be encountered when collecting oil in channels or narrow sounds where for instance tide water may give current velocities exceeding about 2 knots.

It is the purpose of the present invention to change these restrictions on- the use of usual oil protection equipment. This is obtained according to the invention by a method of the type mentioned in the introduction, which is characterize in that a backwater, or vortex, is created near the bend of t boom on its upstream side, where said at least one skimming device is placed.

In this vortex the current velocity will be substantially reduced and, furthermore, the vortex will have a tendency to virtually suck the oil in its direction since the liquid level will be somewhat lower in the vortex than in the surroundings. Thus, άOnventional skimming equipment may be utilized in an effective manner.

According to the invention it is also suggested to provide an at least partial partition between the vortex and

passing water. This prevents the oil in the vortex from coming into contact with, the strongly turbulent boundary layer between the vortex and the passing water, which turbulence otherwise would pull the oil down and out of the 5 boom.

The invention also relates to a device for use in collecting oil or the like floating on water by means of a boom or the like which is towable or moorable in a current so that it 10 forms a bend, and at least one suitable skimming means. The device is characterized in that it comprises a backwater or vortex forming means which is placeable near the bend of the boom on its upstream side.

• "J5 The vortex forming means may advantageously have an elongate form and be provided with means for placing it at least partially submerged and generally transversely of the current resp. towing direction. As regards collecting oil in sounds or channels, one end of the vortex forming means may be

20 attached to the land while the other end is moored so that the means extends generally outwards from the land. The vortex forming means may advantageuously be constituted by a section of boom, which may be ballasted somewhat stronger than usual, thus obviating any other equipment than that whi

25 usually comprised by oil spill prevention equipment.

The device according to the invention may advantageously also comprise at least one partition means which is placeabl downstream of the vortex forming means generally between the 30 vortex formed and the passing water. The partition means serves to prevent the oil which collects in the vortex from coming into contact with the rather strong vortices being formed at the ends of the backwater or vortex forming means

35 The partition means may advantageously be constituted by a section of boom, again for obviating the use of other than usual oil spill protection equipment. The partition means may also be constituted of an end portion of the first ^' mentioned boom. _^"

For better understanding of the invention it is described more closely with reference to the exemplifying embodiments shown in the appended drawings.

c Figure 1 illustrates schematicly and in plan view the use of a device according to the invention in a channel.

Figures 2 and 3 illustrate in plan view the use of the invention wherein a boom is towed by two vessels.

Figure 1 shows a channel 1 between the banks 2, 3 of which a boom 4 is extended so that it forms a bend 5 near one bank

3. The boom 4 is attached to the bank 3 at a point

6 some distance from the end of the boom, so that the end portion 7 of the boom freely may adjust to the current conditions at the site. The free end of the end portion may be attached to the bend 5 of the boom by means of a mooring 8. The current direction in the channel is indicated by the arrow 9. Upstream of the boom bend 5 a backwater or vortex forming means 10 is arranged in the form of a boom section which in one of its ends is moored to the bank 3 and in its ^• other end is connected to anchors through mooring lines 11 so that it is extended generally transversely of the current direction 9. On the downstream side of the boom section 10 a vortex 12 is formed where the current velocity will be less than in the remainder of the channel 1. The more or less free end portion 7 of the boom 4 will have a tendency to follow the contour of the vortex and form a partition against the turbulence formed at the outer end of the boom section 10. In the vortex 12 an oil skimming device 13 is arranged, which through a hose 14 is connected to a collectio tank or the like 15.

Figure 1 schematicly shows an oil spill 16 drifting along with the current. The oil abuts against the boom 4 and is guided towards the boom bend 5, where it is concentrated. Instead of rising in the bend of the boom and being forced under the boom, the oil is virtually sucked into the back¬ water 12, where it is further concentrated and gives tl

skimming device 13 very good operating conditions.

In the embodiment shown in Figure 2 the boom 4 is towed by two vessels 17 and 18. The vessel 17 is located somewhat 5 ahead of the vessel 18, which results in the bend 5 of the boom being located near the vessel 18. On the vessel 18 a backwardly extending boom or the like 19 is arranged, from which extends a vortex forming means 20 in the form of a generally platelike body which extends a suitable distance

10 down into the sea, for instance about 1 m. The platelike body 20 is held in place by a stay 21. Also in this case the main, boom 4 has a more or less free end portion. 7 forming some sort of partition between the backwater or vortex 12 forming downstream of the platelike body 20 and the passing

15 mass of water. The hose 14 from the skimming device 13 leads to the vessel 18.

In Figure 3 is illustrated an embodiment wherein the two boom towing vessels 17 and 18 lie at generally the same level

20 so that the boom 4 mainly takes the form of a ϋ. Upstream of the bend 5 of the boom a transverse plate-formed body 22 is placed, which is connected to the towing vessels by means of tow ropes 23 and 24. On the downstream side of the body 22 a backwardly extending means 25 is attached, which serves

25 for the attachment of two skimming devices 13 and two partition forming boom portions 26. The hoses 14 from the skimming devices lead to a collecting vessel 27, which keeps at a suitable distance behind the bend 5 of the boom and which may be moored to the means 25 in order to keep the

.30 backwater forming means 22 in a suitable position.

It will be clear to the skilled person that the invention may be varied and modified in a number of ways within the frame of the following claims and that the embodiments 35 described herein are only meant to illustrate the invention and not to represent any limitation of same.

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