US3537587A - Flexible filtration boom - Google Patents

Description

United States Patent [72] Inventor Calvin L. Kain [56] References Cited 1325 Roc'kdale, Bartlesville, Oklahoma UNlTED STATES PATENTS 74003 1 1 2,330,508 9/1943 McColl 210/242 :1 3,221,884 12/1965 Muller 210/242 ii} j'f #:33 3,499,291 3/1970 Mikkelsen 61/1 I a e FOREIGN PATENTS 829,756 3/1960 Great Britain 61/] Primary Examiner- Samih N. Zaharna Att0rneyJ. E. Phillips [54) FLEXIBLE FILTRATION BOOM W 10 Claims 4 Drawing Figs ABSTRACT: A flexible weighted net is supported in a vertical [52] U.S. CI 210/242, position by at least one horizontally elongated floatation unit.

61/] A flexible layer of hydrophobic, oleophilic material is at- [SI] lnt.Cl B0ld 33/00 tached to the net to generally conform to the position and [50] Field ofSearch 6l/l; movement of the net. Water passes through the filter layer 2 I01] 70, 242 while liquid hydrocarbons are blocked.

Patented Ndv. 3, 1970 Shoot g at 2 I INVENTOR.

Patented Nov. 3,1970 v 3,537,587- .1

4 yam INVENTOR.

FLEXIBLE FILTRATION BOOM This invention is directed to apparatus for permitting a flow of water while preventing passage therethrough of hydrocarbon materials.

Oil slicks on bodies of water occur from accidental or intentional discharges from ships and shore installations, leaks from underwater pipelines, leaks in the ocean floor from oil bearing formations, and other causes. It is frequently necessary to skim oil slicks in harbor areas. However, present skimmers encounter considerable resistance in being towed through the water and are difficult to "handle. It has also become desirable to contain oil slicks resulting fromunderwater leaks or leaks from injured vessels. However, the great majority of boom systems proposed for such use survive for less than a day in rough seas. In addition, many of the more rigid boom systems do not conform to the contours of the waves sufficiently fast to prevent the passage of oil beneath sections which are left hanging in the air.

lt-has now been discovered that these disadvantages can be avoided by utilizing a flexible weighted net supported substantially vertically in the water by at least one horizontally elongated floatation unit, with at least one flexible layer of hydrophobic, oleophilic material attached to the net to generally conform to the position and movement of the net.

Accordingly, it is an object of the invention to provide a new and improved apparatus for containing oil slicks. It is an object of the invention to provide an oil barrier which can be readily assembled and easily towed through water. Another object of the invention is to provide a flexible boom which rapidly conforms to changes in the contours of the water surface. Yet another object of the invention is to provide a flexible oil boom having sufficient strength to endure through long periods of rough seas.

Other objects, aspects and advantages of the invention will be apparent from a study of the specification, the drawings and the appended claims to the invention.

In the drawings:

FIG. I is an elevational view of a portion of a boom system in accordance with one embodiment ofthe present invention;

FIG. 2 is a plan view ofthe boom of FIG. 1;

FIG. 3 is an elevational view in cross section taken along line 33 in FIG. 2; and

FIG. 4. is a diagrammatic representation of the boom system of FIG. 1 forming an oil retention barrier around an offshore drilling rig.

Referring now to FIG. 1', the flexible filtration boom 11 is shown with an end section 12 and an intermediate section 13. The intermediate sections 13 are identical to the end sections 12 except for the grommets 14. A- cable 15 can be used to tow the boom by the end or to anchor the end ofthe boom. An additional cable (not shown) can also be utilized with the lower grommet, if desired. Each boom section comprises at least one horizontally elongated flexible floatation unit 16. While the floatation units 16 can be employed in single serial array, it is presently preferred to. utilize a serial array of parallel pairs of floatation units located on opposite sides of the barrier wall member 17, as illustrated. The barrier wallmember 17 is supported in a substantially vertical position by the pairs of floatation units 16 when the boom is placed in a body of water.

As illustrated in FIG. 3, the vertical barrier wall 17 comprises a weighted net having horizontal members I8 and vertical members 19. The term weighted net" indicates that the net, either by the weight of members 18 and 19 or by the use of additional weights at the bottom thereof, has a specific gravity significantly'greater than that of water so that the net acts as ballast to maintain wall member 17 substantially vertical. Members 18 and 19 can be steel cables which are interwoven or overlaid and welded to each other. The net can be woven of relatively light material, such as polypropylene rope, provided that additional weightis added to the net to meet the ballast requirements.

It is presently preferredthat the upper portion of barrier wall 17 extend upwardly from the surface ofthe body of water a greater distance, than the floatation units Thus, where curved surfaces of the floatation units permits the surface water and/or oil to be swept upwardly and over the floatation units by wave action, the higher projection of the barrier wall 17 prevents such washover from passing over the boom. The deflected spray passes freelydownwardly between barrier wall 17 and floatation units 16. The portion of the weighted net which extends above the surface 21 of the body of water can be provided with additional stiffening means 22 to further assist in maintaining the exposed portion of the barrier wall in a substantially vertical position. One particular suitable stiffening means which provides the desired upright rigidity while permitting flexibility in other directions and is readily available is chain link fencing. However, any other suitable stiffening means can be employed.

At least one layer 23 of flexible filtering material is positioned generally coextensive with the weighted net. in a presently preferred embodiment the filtering material extends downwardly along one side of the weighted net to a point below the lowermost portion of the weighted net and then upwardly along the opposite side of the weighted net to form a loose fitting envelope for the weighted net. The adjacent vertical ends of the filtering material can be secured together by any suitable means, for example by lacing or by thermal bonding where appropriate. Similarly the upper horizontal edges of the filtering material can be secured together or to the adjacent portion of the weighted net. However, the filtering material can be associated with the weighted net in any manner which causes the filtering material to conform generally to the verticalpositioning and movement ofthe net.

The layer of filtering material can be formed of any suitable hydrophobic, oleophilic material, having a plurality of passageways therethrough. By its nature of not being wetted by water, the filtering material will readily permit the flow of water through the passageways. However, due to its selective affinity for hydrocarbons, oil will adhere to the filtering material and will not pass through the passageways. While any suitable hydrophobic, oleophilic material can be utilized, the crystalline, normally solid polyolefins are particularly useful. These include polymers and copolymers of monomers having the formula Bgfiggfi wherein R is selected from the group consisting of hydrogen or alkyls having from l to 8 carbon atoms. Specifically, this includes polyethylene, polypropylene, ethylene-butene copolymers and the like. All liquid hydrocarbons which are immiscible with water will be prevented from passage through the filtering material while water will flow relatively easily therethrough. While the filtering material can bein the form of granules encased within permeable fabrics, it is presently preferred that the filtering material be in the form of a self-supporting fabric of fibers of normally solid polyolefin. The fabric can be either woven or nonwoven. If desired, the portion of the barrier wall 17 extending above the surface of the body of water can be provided with a film covering 24 which is impermeable to both water and liquid hydrocarbonaceous matter. This minimizes stresses on the vertical rigidity of the upper portion ofthe barrier wall by preventing accumulations of water, oil or other matter. The cover 24 can be secured to the filtration layer 23 by any suitable means, for example by the use of polypropylene rope lashing 25.

Floatation units I6 are preferably in the form of waterproof plastic cylinders 26 filled with particles 27 of material having a specific gravity less than 1, for example a cylinder formed of vinylsheeting and filled with foamed polystyrene particles and air. The plastic cylinders 26 can be encased in a fine mesh 28 whichis capable of retaining the particles 27 in the event ofa rupture of cylindrical tubing 26. The cylinder 26 can be formed from sheeting with the edges overlapping to form an outwardly projecting flange 31. The flange can be provided with outer covering members 32 to provide additional strength and to secure the net 28. The outeri'members 32 can be secured to the flange 3 by any suitable means, for example by lashing 33. The floatation units 16 are secured at closely spaced intervals to the weighted net in barrier wall 17 by suitable means, for example snaphooks 34 and eyebolts 35, to provide substantially continuous support of the vertical barrier wall 17. This permits an easy removal of one of the floatation units'and replacement with a new unit while the boom is on location. While each elongated flexible floatation unit is preferably in the form of a flexible cylinder, it can be composed of a plurality of individual spheres, cubes or other shapes, spaced sufficiently close together to effect substantially continuous support of the vertical barrier wall member.

- Adjacent sections of the boom can be secured together by overlapping the adjacent ends and fastening the overlapped ends by placing U-bolts 36 around opposing vertical members 19 of the weighted net in each section. These U-bolts can be utilized only in the upper half of the barrier walls to provide greater flexibility along the length of the boom.

Referring now to FIG. 4, the boom system 41 comprises a plurality of boom sections serially connected in a rough circle around an offshore drilling rig 42. The end sections are spaced slightly apart to permit the free ingress and egress of boats, but can be closed quickly in the event of the formation of an oil slick within the circle. Buoys 43 are provided at intervals along the length of the boom, and are preferably in pairs positioned on opposite sides of the boom. The buoy cables can be secured to U-bolts 36 or other suitable securing means can be provided.

in one particular embodiment of the invention corresponding to the drawings, each boom section was 100 feet in length and 8 feet in height. Five pairs of floatation units were provided for each section. Each floatation unit was 14 inches in diameter and 18 feet in length and filled with foamed polystyrene. The weighted net was woven of Aainch diameter steel cable at 8 -inch spacings. The filtering material was a nonwoven fabric of polypropylene fibers and encased the weighted net, as illustrated in FIGS. 1 and 3. The barrier wall extended 2%: feet above the surface of the water. This boom system was towed to an oil-drilling rig approximately 6 miles from shore and installed for a period of 12 days. Despite several storms during this period, the boom remained intact and performed satisfactorily to confine an oil slick within its boundaries. The extension of the filtering layer for feet below the normal water level maintained a filtering barrier elongated floatation unit when said boom is placed in a body of water, at least one layer of flexible filtering material, said layer of flexible filtering material being associated with said weighted net to conform generally to the vertical positioning and movement of said weighted net, said layer of filtering material being formed of hydrophobic, olcophilic material having a plurality of passageways therethrough permitting the flow of water through said boom while preventing the flow of liquid hydrocarbonaceous matter through said boom.

2. A boom in accordance with claim 1 wherein said flexible weighted net forms part ofa vertically positioned flexible barrier wall member, and wherein at least two horizontally elongated flexible floatation units are secured on opposite sides of said barrier wall member to support therebetween said barrier wall member substantially vertically in a body of water with said barrier wall member extending upwardly from the surface of the body of water a greater distance than said at least two horizontally elongated flexible floatation units.

3. A boom in accordance with claim 2 wherein the portion of said barrier wall member extending above the surface of said body of water is formed of a material which prevents the passage therethrough of water as well as liquid hydrocarbonaceous matter.

4. A boom in accordance with claim 2 wherein said layer of flexible filtering material comprises fibers of a normally solid 'polyolefin.

5. A boom in accordance with claim 2 wherein said layer of flexible filtering material comprises a nonwoven fabric of polypropylene.

6. A boom in accordance with claim 5 wherein said nonwoven fabric extends downwardly along one side of said weighted net to a point below the bottom of said weighted net and then upwardly along the opposite side of said weighted net to form a loose-fitting envelope for said weighted net, the adjacent end edges of said fabric being secured together.

7. A boom in accordance with claim 6 wherein said weighted net is woven of steel cables the portion of said weighted net extending above the surface of said body of water being provided with stiffening means to maintain the portion of said barrier wall extending above said surface of said body of water in a substantially vertical position.

8. A boom in accordance with claim 7 wherein said stiffening means comprises chain link fencing.

9. A boom in accordance with claim 1 wherein each said elongated, flexible floatation unit comprises a generally cylindrical watertight tubing filled with particles ofmaterial having a specific gravity less than l.

10. A boom in accordance with claim 9 wherein said particles are foamed polystyrene.

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