US3086367A - Offshore mooring platforms - Google Patents

Description

April 23, 1963 c. J. FOSTER OFFSHORE MOORING PLATFO Filed Sept. 22, 1959 RMS 5 Sheets-Sheet 1 INVENTOR.

s Sheets-Sheet 2 Filed Sept. 22, 1959 W/TNESSES III F.

April 23, 1963 c. J. FOSTER OFFSHORE MOORING PLATFORMS 5 Sheets-Sheet 3 w mt Filed Sept. 22, 1959 April 23, 1963 c. J. FOSTER OFFSHORE MOORING PLATFORMS 5 Sheets-Sheet 4 Filed Sept. 22, 1959 INVENTOR.

WITNESSES m zwfitr w m April 23, 1963 c. J. FOSTER OFFSHORE MOORING PLATFORMS 5 Sheets-Sheet 5 Filed Sept. 22, 1959 INVENTOR.

mm l Ir W/TNESSES United States Patent 3,086,367 OFFSHORE NIGQRING PLATFORlWS Christopher J. Foster, Sands Point, N.Y. (44- Wllitehall St, New York, N.Y.) Filed Sept. 22, 1959, Ser. No. 841,515 3 Claims. ((ll. 61-46) My invention relates to an improvement in offshore mooring platforms and has for its object to provide a vertical anchor cylinder impaled in the sea bottom and braced thereon and extending upwards above the sea level to a point Well above the wave action of a hurricane. To use the structure as a mooring a buoyant tank is provided to which a floating barge or other vessel is attached. The doughnut like mooring tank is free to swivel around the anchor cylinder together with the barge as a unit with the wind and to move up and down the anchor cylinder with the tide. The mooring tank also adds considerably to the stability while the structure is lowered to the sea bottom. The vertical cylinder is also used to support a platform for hose handling above storm sea level. My invention when used as a mooring for a storage barge provides a nearly horizontal chain link between the barge and the mooring tank and with a chain weight suspended from the midpoint of the link in order to cause a substantial horizontal tension in the link to keep the barge pressed against its moorings and thus prevent it from surging back and forth. Also by means of leaving a sub stantial sag in the nearly horizontal chain link, suflicient freedom is assured for the pitching, rolling and yawing of the barge without the setting up of excessive stresses in the moorings.

Finally I provide means whereby the link connection to the mooring tank is broken when the tension in the chain link to the barge exceeds 50 tons which is less than one fourth of the anchor chain strength, and I also provide means whereby, after the link break, the mooring tank is sunk to the bottom of the mooringcylin'der so that the anchor chain that has been preferably coiled on the deck of the mooring tank will be completely payed out and the chain pull applied to the bottom of the anchor cylinder directly and without causing excessive bending therein.

In the drawings: FIG. 1 is a plan view of my preferred mooring device; FIG. 2 is a vertical elevation showing my mooring device afloat; FIG. 3 is a vertical elevation showing the mooring cylinder being lowered to the sea bottom; FIG. 4 shows a storage barge attached tomy mooring device; FIG. 4-A shows in an enlarged scale the chain connection between the storage barge and the submersible mooring tank; and FIG. 5 shows the storage barge securely anchored to the lower portion of the anchor cylinder in hurricane weather; FIG. 6 shows a modified offshore platform afloat where the submersible mooring tank is replaced by a removable split-ring tank supporting a platform; FIG. 7 shows the platform welded to the anchor cylinder with the split-ring tank dotted just prior to its removal.

In the drawings where like reference characters designate corresponding parts, 1 represents my preferred mooring device which comprises the mooring cylinder 2. which is welded to the anchor base 3 with its lower portion 4 preferably projecting some 12 feet below the bottom thereof while it extends upwards to a point more than thirty feet above the sea level. The anchor cylinder 2 is provided with a domed head 5 just below the bottom of the base 3. This domed head is preferably provided with an opening 6 at its center while an airtight dome 7 is provided in the shaft at a distance from the top thereof in order to allow for the installation of an air compressor 8.

3,086,367 Patented Apr. 23, 1963 "ice On the top of the shaft 2, the hose handling stiflleg derrick 9 is mounted on a rotating platform 9 on wheels or rollers to render it free to rotate with a wind swung storage barge 10. Passing through the anchor base 3, the pipe line 11 is connected to an underwater supply line 12 and it terminates in a riser 14 at the center of the anchor cylinder 2.

The horizontal line 13 indicates the water surface in calm weather, while the dotted line 13' indicates the surface contour of a maximum wave in hurricane weather.

The riser 14 is provided with the swivel manifold 15 which together with the horizontal pipe 16 and the flexible hose 17 forms my preferred connection to the storage barge 10.

The anchor base 3 is provided with a peripheral buoyancy chamber 18 mounted thereon, and I prefer to raise the deck of the anchor base 3 at the center for stability reasons. I prefer to install an annular shelf 19 on the shaft 2 to form a resting place for the mooring tank 20 in its submerged position. The anchor base 3 is also pro vided with a layer of concrete ballast 21 on the bottom thereof in order to add to stability of the device when it is being lowered to the sea bottom.

The mooring tank 20 is shown provided with a bottom that slopes upwards towards the outer periphery with the cylindrical shell projecting some distance downwards to trap air under the bottom of the tank. A valve 22 is installed for air escape and a check valve 22' is installed for water discharge.

I also prefer to install an upward directed air nozzle 23 which discharges the air into the air trap under the tank bottom, when it has to be raised after being submerged.

In FIG. 4 the buoyant mooring tank 20' is shown free to rotate around the mooring shaft 2 together with the storage barge and with the anchor chain 24 coiled on the deck thereof. This chain is shown looped around a sleeve projection 25 on top of the tank, and at the point Where the chain leaves the tank deck I prefer to install an open ended hook 26, on which the chain is hung and draped into 'a deep sag 28 between the hook and the mid point of the chain link 27. The weight of the sag sets up a considerable tension in the near horizontal chain link 27 which will prevent the storage barge from surging back and forth. The shear pin connection 29 on the mooring tank is designed to shear off when the tension exceeds a predetermined tonnage of some 50' tons.

I prefer to connect a ring 30 to the anchor chain 24 and put the ring on the long upright handle of the sea cock 31 which I prefer to install between the pocket under the mooring tank and the tankbody proper. I also prefer to provide the mooring brackets with thick rubber fenders 32 against which the storage barge '10 will rest, and I also provide annular rubber fenders 33 around the center opening of the mooring tank in order to effectively cushion all mooring strains.

I also prefer to install a snap-off connection 34 where the hose is supported by the hoisting line. Vents and compressed air connections, not shown on the drawings, are provided for the anchor cylinder 2, the peripheral tank 18 and the main tanks of the base 3.

The method of operation is as follows: The mooring device rigged as shown in FIG. 2 is towed to location. The water is kept out from the anchor cylinder by compressed air. With the anchor base 3 flooded and the peripheral tank 18 empty the structure will sink as water enters the pocket enclosed by the peripheral tank 18 through the scuppers 35. The sinking is thereupon entirely controlled by the air vent of the anchor cylinder 2 which permits the compressed air to escape. During the sinking the mooring tank 20 will float as the cylinder shaft 2 submerges. The whole structure mainly supported by the buoyant peripheral tank 18 together with the buoyant part of the anchor cylinder 2 is stable during submerging maintaining an upright position, then the lower projection of the shaft becomes impaled in the river mud and the structure and the base settles on the sea bottom as shown in FIG. 4. The peripheral tank 18 is then flooded, additional solid ballast may be added if stability requires it. The storage barge is moored to and tied to the mooring tank 20, preferably by pinning the end of the anchor chain to an anchor pad which is welded to the end of the storage barge 10, all as illustrated in FIG. 4-A. In handling the anchor chain the stitfleg derrick 9 is used.

With the chain arranged as shown and with the hose connections made up as shown, quick release is provided automatically if a hurricane suddenly arises.

With mounting wind and wave action the predetermined maximum tension is soon reached whereupon the link connection 29 will release. The barge will then drift with the wind and when it moves away from the buoyant mooring tank 20, the barge 10, pulls the drain out of its sag and turns the sea cock valve handle 31 to its open position, whereupon the chain 24 is pulled off the hook 26 and uncoils. In the meantime the flooded mooring tank 20 sinks to the bottom of the anchor cylinder shaft 2 as allustratedin FIG. 5.

In order to again float the tank 20, the valve 22 is closed by diver or automatic means not shown. The air jet is now opened and compressed air becomes entrapped under the tank 20 and enters it through the open sea cock 31 and the water is pressed out through the check valve 22'. The float will rise and as the water head is reduced the dewatering proceeds faster. When the tank 20 is afloat the sea cock 31 is closed and the valve 22 is opened. The chain is readjusted and with the broken fastening again secured to the tank 20 the cycle is completed.

FIGS. 6 and 7 show a modified three story platform 36 carried above hurricane reach on a truss 37 which is supported on the removable split-ring tank 38. This tank is removed after the platform 36 has been welded to the anchor cylinder 2.

I do not desire to be understood as limiting my invention to the specific details of construction and arrangements herein described, and illustrated, as it is manifest that variations and modifications may be made in the features of construction and arrangement of parts in. the adaptation of the device to other uses than moorings without departing from the spirit and scope of my invention and improvements. I- therefore, reserve the right to all such conditions and modifications that properly. fall within the scope of my invention and the terms of the following claims:

I claim:

1. In an offshore mooring platform which also includes a floating oil storage barge, a hollow buoyant anchor base seated on the sea bottom, means to flood the hollow buoyant anchor base, a vertical anchor cylinder attached thereto and extending above the sea level, a platform mounted thereon, a. buoyant annular mooring tank concentrically mounted on the anchor cylinder and free to float and swivel all around the upper part of the vertical anchor cylinder and free to move up and down thereon, an anchor chain coiled on the bouoyant annular mooring tank with one end attached to the storage barge and the other end attached to the annular mooring tank, an added short tension connection between the barge and the mooring tank resisting the full mooring pull, means whereby the short tension connection is released when the mooring pull substantially equals one quarter of the permissible stress of the anchor chain, a flood valve on the annular tank and means whereby the flood valve is opened after the tension release, thus permitting the annular tank to sink to and be pulled all around the lower part of the vertical cylinder by the floating storage barge chained thereto.

2. An offshore mooring which includes a floating oil storage barge having an anchor base seated on the sea bottom, a vertical cylinder attached thereto extending above the sea level, an annular buoyant hollow tank concentrically mounted on the vertical cylinder and free to move up and down on the upper portion of the vertical cylinder, a sea cock on the annular tank to flood and sink it, an anchor chain coiled on top of the annular tank, one end of the chain attached to the storage barge, a hook attached to the annular tank, a shear pin connection thereon, a tension connection therefrom to the anchor chain at a mid point of the link connection between the barge and the tank, the chain arranged to form a loop between said point and the hook on the annular tank to press the barge and the annular tank tightly together and to permit them to swing as a unit around the upper part of the vertical cylinder with the mooring strain resisted only by the tension connection until the mooring pull substantially exceeds one quarter of the working stress of the anchor chain, means whereby the tension connection is broken at the aforesaid mooring pull to permit the barge to separate from the annular tank, means to open the sea cock and sink the separated tank to close proximity of the anchor base, and means whereby the anchor chain is pulled out from the tank and leaving the tank free to rotate all around the lower portion of the vertical cylinder when pulled around by the barge which is: chained thereto.

3. In an outlet station for an oil supply line, an offshore mooring after claim 2, a rigid pipe riser from the supply line having a swivel pipe above the sea level connected to the storage barge which is free to rotate around the upper part of the vertical cylinder together with the annular tank and the swivel pipe as a unit, and a snapoff connection in the swivel pipe.

References Cited in the file of'this patent UNITED STATES PATENTS 2,534,480 Shannon Dec. 19, 1950 2,621,485 Ross Dec. 16, 1952 2,771,617 Brackx Nov. 27, 1956 2,894,475 Hutchinson July 14, 1959 FOREIGN PATENTS 598,037 Great Britain Feb. 9, 1948 692,892 Great Britain June 17, 1953 778,450 Great Britain July 10, 1957 1,041,426 Germany Oct. 16, 1958 220,711 Australia Feb. 20, 1959

Claims (1)

1. IN AN OFFSHORE MOORING PLATFORM WHICH ALSO INCLUDES A FLOATING OIL STORAGE BARGE, A HOLLOW BUOYANT ANCHOR BASE SEATED ON THE SEA BOTTOM, MEANS TO FLOOD THE HOLLOW BUOYANT ANCHOR BASE, A VERTICAL ANCHOR CYLINDER ATTACHED THERETO AND EXTENDING ABOVE THE SEA LEVEL, A PLATFORM MOUNTED THEREON, A BUOYANT ANNULAR MOORING TANK CONCENTRALLY MOUNTED ON THE ANCHOR CYLINDER AND FREE TO FLOAT AND SWIVEL ALL AROUND THE UPPER PART OF THE VERTICAL ANCHOR CYLINDER AND FREE TO MOVE UP AND DOWN THEREON, AN ANCHOR CHAIN COILED ON THE BUOYANT ANNULAR MOORING TANK WITH ONE END ATTACHED TO THE STORAGE BARGE AND THE OTHER END ATTACHED TO THE ANNULAR MOORING TANK, AN ADDED SHORT TENSION CONNECTION BETWEEN THE BARGE AND THE MOORING TANK RESISTING THE FULL MOORING PULL, MEANS WHEREBY THE SHORT TENSION CONNECTION IS RELEASED WHEN THE MOORING PULL SUBSTANTIALLY EQUALS ONE QUARTER OF THE PERMISSIBLE STRESS OF THE ANCHOR CHAIN, A FLOOD VALVE ON THE ANNULAR TANK AND MEANS WHEREBY THE FLOOD VALVE IS OPENED AFTER THE TENSION RELEASE, THUS PERMITTING THE ANNULAR TANK TO SINK TO AND BE PULLED ALL AROUND THE LOWER PART OF THE VERTICAL CYLINDER BY THE FLOATING STORAGE BARGE CHAINED THERETO.

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