US3786773A - Hydrocarbon retainer for drydocks - Google Patents

Abstract

A device placed on the floor of a drydock to encompass the damaged area of the hull of a ship drydocked therein, intercepts the flow of water from the area of the hull during drydocking to filter out hydrocarbons eminating from the damaged hull to preclude contamination of the waters surrounding the drydock and the drydock itself.

Description

Unite States Patent. 1191 1111 3,786,773

Preus Jan. 22, 1974 HYDROCARBON RETAINER FOR 3,702,657 11 1972 Cunningham et al. 61/1 F x DRYDOCKS 3,537,587 11 1970 Kain 61/1 F x Paul Preus, PO. Box 1002, Toms River, NJ. 08753 Filed: Sept. 28, 1972 Appl. No: 292,887

Inventor:

US. Cl. 114/45, 61/66 Int. Cl. 1863c 1/02 Field of Search... 114/435, 44, 45, 46, 47, 48,

References Cited UNITED STATES PATENTS Jamieson 114/46 Primary Examiner-Duane A. Reger Assistant Examiner-Randolph A. Reese Attorney, Agent, or FirmCameron, Kerkam, Sutton, Stowell and Stowell [57] ABSTRACT A device placed on the floor of a drydock to encompass the damaged area of the hull of a ship drydocked therein, intercepts the flow of water from the area of the hull during drydocking to filter out hydrocarbons eminating from the damaged hull to preclude contamination of the waters surrounding the drydock and the drydock itself.

8 Claims, 6 Drawing Figures HYDROCARBON RETAINER lFOR DRYDOCKS BACKGROUND OF THE INVENTION In the repair, overhaul and maintenance of ship hulls, the drydock provides a means to provide access to the entire surface of the hull for accomplishing the necessary work. In the process of drydocking, the ship to be drydocked is floated into the drydock and positioned over the drydock blocks arranged to conform to and support the ships bottom. The water in the drydock is then expelled and the ship comes to rest on the drydock blocks.

There are two basic types of drydock; the graving dock and the floating drydock. The graving dock is fixed and provided with water-tight doors which seal the drydock after the ship is positioned so that the water therein can be pumped out. The floating drydock is provided with water ballast tanks for partly submerging the dock to provide for ship entry, and with pumps for discharging the water ballast from the tanks for floatation of the dock once the ship is positioned therein. Water in the latter type of drydock is expelled therefrom by gravity as the drydock is refloated.

Although the invention disclosed herein is equally applicable to both the aforgoing types of drydocks, it will be described hereinafter as specifically applied to the latter, floating drydock, for purpose of illustration.

A problem which has become of increasing importance in recent years is pollution of the environment and not the least noted contributor to this problem is pollution by oil spills on waterways. Public reaction and government sanctions have been so severe that such pollution is becoming an important factor in the economic survival of many industrial enterprises.

When a damaged ship requires drydocking for inspection and/or repairs and the fuel or cargo tanks have been damaged, suspected or actual pollution of the waters surrounding the drydocks by oil from damaged tanks is inevitable unless definite preventive steps are taken because the great quantities of water expelled from the drydocks drain directly into the adjacent waters and will carry any oil contamiments present or discharged into the drydocks with them.

In the case of collisions or groundings of dry cargo ships, the hazard of oil pollution during subsequent drydocking is great since fuel oil or bunkers is carried in double bottom tanks formed by the bottom hull of the ship and spaced, parallel-planar tank tops" or double bottoms disposed above the bottom hull of the ship. Upon grounding or collision, one or more of these double bottom tanks is almost invariably holed if the hull of the ship is penetrated and, upon being holed, that tank is open to the sea. Although there is an initial escape of oil from a holed double bottom tank, the

major portion of the oil in that tank, due to its lower density, is pressed against the tank top and remains in the tank as long as there is water beneath the ship to keep it there. Upon drydocking, the water pressure is relieved and the bunkers are discharged into the drydock. Although a major portion of the bunkers could sometimes be removed from the damaged double bottom tanks by the ships fuel transfer system, such removal is sometimes inadvisable or impossible due to fear of contamination of fuel transfer system by sea water, because of loss of heating capability necessary to render the bunkers pumpable in the damaged tank or because of the ships fuel transfer capability.

In the cases as described above, oil pollution during drydocking is a serious problem and it is that to which the present invention is directed.

SUMMARY OF THE INVENTION This invention provides a device for intercepting hydrocarbons escaping from the damaged hull of a ship during drydocking thereof.

In a preferred embodiment, the invention provides such a device comprising a wall structure disposed on the deck of a drydock to extend beneath the hull of a ship and encompass the damaged portion thereof; at least a portion of the structure being liquid pervious to pass liquids flowing from the damaged portion therethrough and an oleophilic hydrophobic material associated with the liquid pervious portion to absorb and retain hydrocarbons from the liquid passing therethrough.

These and many of the attendant advantages and objects of this invention will be better understood by those skilled in the art by reference to the following detailed description when viewed in light of the accompanying drawings wherein like components throughout the figures thereof are indicated by like numerals and wherein:

BRIEF DESCRIPTION OF THE DRAWING FIG. I is a perspective view of an embodiment of the invention disposed in a floating drydock.

FIG. 2 is a fragmentary elevational view of a portion of a device in accordance with the invention.

FIG. 3 is a sectional view of the device of FIG. 2 taken along the lines 3-3 thereof.

FIG. 4 is a perspective of the drydock of FIG. I showing a ship in place in the drydock with the drydock submerged.

FIG. 5 is a sectional view taken along the line 55 of FIG. 4.

FIG. 6 is a view similar to FIG. 5 after the water has been expelled from the drydock.

DESCRIPTION OF A PREFERRED EMBODIMENT In FIG. 1 an oil containing device in accordance with the invention is shown generally at 10 mounted on the deck of a floating drydock 12. The device 10 comprises longitudinal legs 14 and 16 running fore and aft on the starboard and portsides of the drydock and legs 18 and 20 running thwartships the drydock. The legs intersect one another to form a rectangular enclosure beneath what will be the damaged portion of a ship when placed in the drydock 12. The longitudinal legs 14 and 16 are disposed outboard of what will be the turn of the bilge of a ship when placed in a drydock. Drydock blocks 22 are disposed on the floor of the drydock 12 to support a ship when placed in the drydock in a manner well known in the art. The thwartship legs 18 and 20 are of equal height to the drydock blocks-22 at least for the portion thereof coinciding with the bottom of a ship when placed in the drydock such that the legs will be in sealing contact with the ship bottom fore and aft of the damaged portion of the ship. The longitudinal legs 14 and 16 as well as the portions of the legs l8 and 20 outboard of the ship bottom may be the same height as the afordescribed portions of legs 18 and 20 if the damage to the ship is confined to the hull bottom itself or may be greater in height if the damage extends above the turn of the bilge as will be described in greater detail below.

FIGS. 2 and 3 are detailed views of the device 10 of FIG. I. It should be understood that the exact form of construction of the device may vary and that the following fabrication details represent a convenient form of construction with materials readily available in a particular shipyard at a particular time. Each of the legs I4 through 20 are of substantially identical construction and the detailed structure set forth here'inbelow should be understood to apply equally to any portion of any of the legs with the variations as may be set forth hereinbelow. The device 10 is attached to the deck of the drydock 12 preferably by welding vertical members 24 thereto. Top cross members 26 are then attached, preferably by welding, to the tops of vertical members 24 and the structure is braced by a stiffleg member 28 attached diagonally between the top of one vertical member and the bottom of the adjacent opposed vertical member 24. The stiffleg 28 is preferably angled upward toward the interior of the enclosure formed by the legs 14 through 20 (FIG. 1) so that the member 24 to which the stiffleg 28 attaches at the top is disposed on the inside edge of the device 10 to brace the device toward the direction of eventual flow as will be described in detail below. The members described thusfar are preferably metal and more particularly angle iron or a similar readily available structural form. A pair of lower stringers 30 are attached to the lower ends of the vertical member 24 on the drydock floor 12. A pair of upper stringers 32 are attached to the upper ends of the same vertical members. Mesh netting 34, preferably 541 inch mesh hardware cloth wire, is attached between the stringers to form perforate sides and a top for the device 10. A bouyant oil absorbent, water repellant material 36, having an effective partical dimension sufficient to be retained by the mesh 34, is disposed in the confines formed by the mesh 34. Petroleum absorbent material marketed by Clean Water, Inc. of Toms River, NJ. under the trademark, Sorbent C, has proven ideal for the purpose of this invention. At suitable intervals along the length of each leg of the device 10, 8 foot intervals for example, cross stringers 38 are attached between the upper stringers 32 and between the lower stringers 30 to which mesh netting 40 is attached to serve to longitudinally divide the legs and preclude migration of the absorbent material 36 during operation of the device as described below. The above described stringers are preferably formed from planking such, for example, as 2 X 12 inch planks, the netting 34 and 40 being attached thereto by nails, staples or the like.

In operation, and with reference now specifically to FIGS. 4, and 6, a ship 42 is brought into the drydock l2 and is positioned over the drydock blocks 22 so that a damaged portion of the hull 44 (FIGS. 5 and 6) is positioned within the confines of the device 10.

As can be seen in FIG. 5 double bottom tanks 46 containing the ships fuel oil or bunkers" 48, are disposed in the bottom of the hull of the ship 42. The damaged portion 44 has ruptured one of these tanks 46 and a portion of the bunkers 48 has been displaced and replaced by sea water 50. Since oil is less dense than water, the bunkers 48 in the ruptured tank 46 are pressed against the tank top and are retained in the upper portion of the tank. The oil absorbent material 36, because of its bouyancy and water repellant characteristics, floats to the top of the device as the drydock is submerged and remains there, pressed against the top mesh of the device, so long as the drydock is submerged.

In FIG. 6, the drydock 12 has been refloated bringing the ship 42 out of the water for repair. The water in the drydock is discharged as the drydock is raised, through the open end thereof. As this water is discharged, the oil or bunkers 48 in the damaged tank 46 drains from that tank and flows, with the water level beneath the tank, toward the open ends of the drydock. As the water level drops in the drydock, the oil absorbent material 36 also follows the water level thereby remaining in a blocking position relative to the path the oil being discharged from the holed tank 46 must take to leave the area of the hull damage. As the oil and water reach the blocking position assumed by the oil absorbent material 36, the oil is absorbed at this point and effectively filteredf from the-water flowing through the device 10 thereby retaining all of the 'oil in the absorbent material and/or within the confines of the device 10 while allowing all of the water to drain from the drydock without pollution of surrounding waters.

In actual use a device incorporating this invention, as reported in the US. Coast Guard s Environmental Protection Newsletter, February, 1972 (Vol. 1, No. 1), the M/V Singapore Trader was successfully drydocked without any overboard discharge of bunker fuel although a considerable amount of fuel was discharged onto the drydock floor within the confines of the device.

Although the device 10 is illustrated having a water pervious construction throughout the entire perimeter thereof, it should be understood that portions thereof may be formed as a water tight wall with water pervious box portions interspersed along the length thereof as required. The primary feature that must be considered in such design is that the oil absorbent material 36 be present in sufficient quanity to absorb the full amount of oil expected to be discharged from the ship. Absorbent C petroleum absorbent material has an absorbtion capability of about 0.55 gallons of bunker C per pound of absorbent material and, utilizing the probable capacity of the damaged tanks, the quantity of material needed can readily be determined beforehand.

What has been set forth herein is intended as exemplary of a teaching in accordance with the invention to aid those skilled in the art in the practice thereof.

What is new and desired to be protected by Letters Patent of the United States is:

l. A device for retaining hydrocarbons discharged from the damaged hull of a ship during drydocking thereof comprising:

a drydock a wall structure extending upwardly from the floor of said drydock to define an enclosure to extend beneath the hull of said ship and encompass the damaged portion thereof, at least a portion of said wall structure being liquid pervious to pass all liquid flowing from the damaged portion of said hull therethrough; and means associated with said device to retain hydrocarbons in the liquid passing therethrough.

2. A device in accordance with claim I wherein the portion of said wall structure coinciding with the bottom of said ship is configured to make sealing contact length of about inch disposed in said enclosure.

6. A device in accordance with claim 5 wherein said 1 mesh is about #4 inch in size.

7. A device in accordance with claim 5 wherein said material is of lesser volume than said mesh enclosure and is disposed to follow the water line of the water in said drydock within the limits of said enclosure.

8. A device in accordance with claim 5 wherein said material is placed in said enclosure in quantities of about 2 pounds for every gallon of hydrocarbon to be discharged.

Claims (8)

1. A device for retaining hydrocarbons discharged from the damaged hull of a ship during drydocking thereof comprising: a drydock a wall structure extending upwardly from the floor of said drydock to define an enclosure to extend beneath the hull of said ship and encompass the damaged portion thereof, at least a portion of said wall structure being liquid pervious to pass all liquid flowing from the damaged portion of said hull therethrough; and means associated with said device to retain hydrocarbons in the liquid passing therethrough.

2. A device in accordance with claim 1 wherein the portion of said wall structure coinciding with the bottom of said ship is configured to make sealing contact with said hull to preclude flow of liquid between said hull and said wall structure.

3. A device in accordance with claim 1 wherein said means includes a buoyant oleophilic-hydrophobic material in said liquid pervious portion.

4. A device in accordance with claim 3 wherein said liquid pervious portion of said wall structure comprises a mesh enclosure for containing said oleophilic-hydrophobic material therein.

5. A device in accordance with claim 4 wherein said oleophilic-hydrophobic material comprises a loose mass of fiberous material having an effective fiber length of about 1/8 inch disposed in said enclosure.

6. A device in accordance with claim 5 wherein said mesh is about 1/4 inch in size.

7. A device in accordance with claim 5 wherein said material is of lesser volume than said mesh enclosure and is disposed to follow the water line of the water in said drydock within the limits of said enclosure.

8. A device in accordance with claim 5 wherein said material is placed in said enclosure in quantities of about 2 pounds for every gallon of hydrocarbon to be discharged.

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