US2972973A

US2972973A - Offshore platform

Info

Publication number: US2972973A
Application number: US733284A
Authority: US
Inventors: Ernest L Thearle
Original assignee: Individual
Current assignee: Individual
Priority date: 1958-05-06
Filing date: 1958-05-06
Publication date: 1961-02-28
Anticipated expiration: 1978-02-28

Description

Feb. 28, 1961 E. L. THEARLE 2,972,973

OFFSHORE PLATFORM Filed May 6, 1958 3 Sheets-$heet 1 300 2 9 291, 06 r 8%; q BBQ INVENTOR.

I 1i ERNEST L. 771mm: i W 5% Feb. 28, 1961 E. L. THEARLE 2,972,973

OFFSHORE PLATFORM Filed May 6, 1958 r 3 Sheets-Sheet 2 INVENTOR. ERA/57 L. THEARLL' BY WW- A TTOENE) Feb. 28, 1961 THEARLE 2,972,973

OFF SHORE PLATFORM Filed May 6, 1958 5 Sheets-Sheet 3 55 v 55 28a 28b INVENTOR.

EBA/57 L. THEAQLE BY V W ,4.

United grates Patent QFFSHORE PLATFORM Ernest L. Thearle, 12710 S. 3rd St., Yucaipa, Calif.

Filed May 6, 1958, Ser. No. 733,284

3 Claims. (Cl. 114-435) 2,972,973 i s F .1.

hull 11 provided with three ballast tanks 12 which are disposed symmetrically with reference to the vertical axis of the hull. The hull may be cylindrical as shown, or it may be hexagonal or other suitable shape. It is a closed tank which provides the necessary buoyancy. The buoyancy is varied and controlled by the amount of water admitted to or expelled from the ballast tanks 12.

The superstructure 13 is supported by slender tubular members 14 which offer a minimum resistance to move ment of water. The water is shown at 15, its surface being shown at 15a. The superstructure 13 comprises two decks, to wit, a lower machinery or operating deck operations, for radar stations and as heliports, include the following: The platform should be relatively unaffected by tides or wave motion and by changes in the amount or distribution of the live load. Also, it is preferably capable of being anchored in relatively deep water and of being moved without undue difficulty from one location to another.

Heretofore, to my knowledge, offshore platforms satisfying these objectives have not been provided, unless, perhaps, by the use of extremely complex machinery and equipment.

It is an object of the present invention to provide an improved offshore platform of the floating or buoyant type.

It is another object of the invention to provide a stable offshore platform which is of the floating or buoyant type and whose working deck remains in a predetermined horizontal plane substantially unaffected by tides, wave motion and live load.

Yet another object is to provide a stable oflshore platform of the general character described which can be anchored in relatively deep water, and which can be moved without undue difficulty fro-m one site to another.

These and other objects of the invention will be apparent from the ensuing description and the appended claims.

Certain forms of the invention are illustrated by way of example in the accompanying drawings in which:

Figure 1 is a view in side elevation of the platform of the invention.

Figure 2 is a section taken along the line 22 of Figure 1, such section being taken in a horizontal plane beneath the working deck and showing in top plane view and more or less diagrammatically, the machinery employed to operate the platform.

Figure 3 is a view in side elevation of one of the automatic weighing and adjustment units, there being three pairs of such units, one member of each pair being intended to adjust the ballast and the other member being intended to adjust tentacle tension directly by Winch control.

Figure 4 is a diagrammatic view of a control circuit for operating a pair of the weighing and adjustment units, one of which is shown in Figure 3.

Referring now to the drawings and more particularly to Figures 1 and 2, the platform is generally indicated by the reference numeral 10. It comprises a buoyant 16 and an upper working deck 17. It is the latter deck (the deck 17) which is intended to support drilling equipment, radar equipment or the like or to serve as a landing platform for aircraft such as helicopters.

The platform 10- is anchored to the sea bottom 18 (or to the bottom of a lake, river or other body of water), by anchors 19 and anchor cables 20. The anchor cables 20 pass under sheaves 25, thence upwardly to anchor winches 26. Preferably the sheaves 25 are so placed that the anchor cables 20, if extended as tangents to the sheaves 25, would meet at approximately the center of the working deck 17. The platform 10 is preferably a three-celled structure as shown, hence there are preferably three anchor cables 20. However, the principles of the invention are applicable to a different number of cells, for example, four in which case a like number of anchors and cables will be employed. For convenience of reference the three cells are indicated as A, B and C. However, since the three cells are identical only one need be described.

It is the purpose of the anchors 19 and anchor cables 20 to restrain the platform 10 from lateral movement. The more difficult function of holding the working deck .17 in a fixed, horizontally plane is accomplished by weights or spuds 27a, 27b, tentacles 28a, 28b and the machinery and control equipment located on the deck 16; Each of the cells A, B and C has associated with it the following equipment: A pair of spuds 27a, 27b; a pair of tentacles 28a and 23b; a pair of

tentacle winches

29a, 2%; one ballast tank 12; one anchor winch 26; two

automatic weighing units

30a, 3%, one of which is shown in Figure 3; and a control circuit 31 (see Figure 4). It will be understood that a suitable prime mover (e.g., a diesel engine) will be provided to supply power for operating this equipment. Thus, a single diesel engine-electric generator combination may be provided for the entire platform 10 and each winch may be provided with an individual electric motor powered by the electric generator.

Referring now to Figure 3, the weighing unit 30a of cell A is there shown. All of the other five weighing units (i.e., the unit 3011 of cell A and the

units

30a and 30b of cells B and C) are identical. Therefore, detailed description of this one unit will suflice.

As will be seen, the tentacle 28a passes over a large sheave 35 which forms a part of the weighing unit 30a. The sheave 35 is journaled at 36 in a lever 37, such lever being fulcrumed at 38 on brackets 39, one of which is shown in Figure 3. The free end of the lever 37 passes through a stop member 40 which is fixed to the deck 16, and which serves the purpose of preventing extreme motion of the lever. An expansion spring 45 and a screw 46 opposing the spring are provided to hold the lever 37 normally in whatever position desired. The

extreme outer end of the lever 37, which is indicated by I 49 and 50 are supported by a bracket 51 which is fixed to the deck 16. The pressure-responsive device 49 is connected by tubing 52 to a pressure-responsive switch 53. The other pressure-sensitive element 50 is connected by tubing 54 to apressure-responsive switch 55'. A branch tube 60 connects the pressure sensitive element 50 to a third pressure-responsiveswitch 61.

- The weighing unit 30a illustrated in Figure 3 is the ballast control unit of cell A. That is, the unit 30a is intended to control the ballast in the ballast tank 12 of cell A. This ballast tank (as well as the other two ballast tanks) is provided with an inlet valve 62 and an outlet pump 63 (which are shown in Figure 4) to admit and discharge water respectively.

Suppose that the tentacle 28a shown in Figure 3 is relaxed because of insuiiicient buoyancy. The lever 37 will rotate in counterclockwise direction as viewed in Figure 3, thereby relieving pressure in bellows 5t} and in switch 55. The switch 55, therefore, closes and starts the ballast pump 63 of cell A. Pump 63 pumps water out of the tank 12 of cell A, thereby increasing the buoyancy of cell A until it reachesits normal value. If, on the other hand, there is excessive tension in the tentacle 28a; the lever 37 will rotate in clockwise direction thereby relieving pressure in bellows 49 and in switch 53, which will open the ballast valve 62 of the ballast tank 12. The buoyancy of cell A is, therefore, decreased until the normal value is reached. 7

As stated above, cell A is provided with a second weighing unit 30b which is similar to the weighing unit 30a, but it is connected to the tentacle 28b and it serves toopera'te a motor (not shown) which operates the winch 29b. Thus, when the tentacle 28b of cell A relaxes, lever 3.7 of the weighing unit 30b, will rotatecounterclockwise and, acting through the bellows 50 and switch 55, it will cause the winch 29b to rotate in the proper direction to take. in the tentacle 28b until the proper tension is reestablished. Similarly if the tension of tentacle 28b becomes excessive, the weighing unit 30b will operate, in a manner which will be apparent, to restore the proper tension. p It will be understood that each of the cells B and C has a pair of tentacles 28a and 28b, a pair of

winches

29a and 2%, a pair of weighing

units

30a and 30b, a ballast valve 62. and a ballast pump 63 which operate in like manner to maintain the proper tension in each of the tentacles 28a and 28b. The system is preferably adjusted to maintain the tentacles 28a and 28b between one-quarter and three-quarters of the spud weight of each tentacle.

Referring now to Figure 4 the control circuit 31 of cell A is there shown. Similar control circuits are pro vided for cells B and C. Figure 4 shows a simplified line diagram rather than a complete circuit but it will suifice for the purpose of illustration. Thus the weighing unit 30a operates its pressure switches 53 and 55 (lefthand side of the diagram).

Switches

53 and 55 are connected by a circuit generally indicated as 70a and which includes a transfer switch 71a, to the ballast valve 62 and ballast pump 63, respectively. A solenoid 72b maintains, the switch 71a normally closed. Similarly weighing unit 30b operates its pressure switches 53 and 55' (right-hand side of the diagram), which are connected by a circuit generally indicated as 70b, and which includes a transfer switch 71b to the winch 2912. One of the

switches

53, 55 operated by the weighing unit 3015 operates the winch 29b in one direction (to take in the tentacle 28b) and the other switch operates the Winch 29b oppositely to pay out the tentacle "2815. In Figure 4, the reference numerals 29c indicate reversible motors for. operating the winches 29a and 2911.

It will be seen that two solenoids 72a and 73a are also PI ided in the control circuit 31 of cell A. The sole.- noids 72a and 730: are energized only when the low pressure switch 61 of weighing unit 3041. O ny Cell is closficb i The switch 61, which is also shown in Figure 3, closes when, for any reason, a very low pressure is reached in the bellows 50 (see Figure 3). Thus if the tentacle 28a of cell A should break, switch 61 will close, solenoids- 72a and 73a will be energized and

transfer switches

71a and 71b will shift to the opposite contacts there energizing

circuits

74a and 75b. The energizing of circuit 74a will operate winch 2901, which will haul in the broken tentacle 28a. The energizing of circuit 75b will connect weighing unit 30b to the ballast valve 62. and ballast pump 63, thereby shifting weighing unit 3% and itstentacle 28b from its normal winch control to ballast control. Leads 76 connect with the control circuits of cells B and C. Hence when any of the tentacles 28a breaks all of the weighing units 30b are placed on ballast control and all of the weighing units 3G5: are placed on winch control. .The winches 2% connected to unbroken tentacles 28a do not exert sufiicient force, however, to raise their spudsydue to ballast control. If a tentacle 28b breaks while on winch control, winch 2% will wind in the tentacle and the ballast control of so corrects for its loss.

Thus a continuous ballast and winch control are maintained at all times; the deck 17 is maintained fixed in space regardless of varying loads and varying load distribution; emergency operation is provided in case any of the ballast controlled tentacles should break; and in case of emergency a symmetrical application of winch control is preserved.

To remove the platform from a site, the anchor winches 26 and the winches 29a are backed oif to slacken the anchor cables 20 and tentacles 28a, respectively. The weighing units 30a will, therefore, automatically remove ballast from the ballast tanks 12 and will provide the necessary buoyancy until the platform surfaces and acquires its natural level and stability with its ballast tanks empty. Meanwhile the weighing units 3012 will back off their winches 2% to maintain constant tension. The weighing

units

30a and 3% are then inactivated, the spuds and anchors are raised and the platform is towed to another site. To establish the new site the reverse procedure is carried out.

I claim:

1. A platform structure of the character described comprising a deck, a buoyant hull supporting the deck, said hull having inlet means and outlet means to admit and expel Water and thereby decrease and increase its buoyancy, respectively; means for anchoring the platform to restrain the same from transverse displacement, weights opposing the buoyancy of the platform, cables connected to said weights and to the platform, and controland sensing means actuated by tension in said cables to operate said inlet and outlet means to increase and decrease the buoyancy of the hull and maintain the deck in a fixed horizontal plane.

2. A platform structure of the character described comprising a deck, a buoyant hull supporting the deck. said hull comprising a plurality of ballast tanks each having inlet and outlet means for decreasing and increasing, respectively, the buoyancy of the respective tank and means for anchoring the platform to restrain the same from transverse displacement; said platform structure also comprising a tentacle, a weight and a winch for each ballast tank, said weight being adapted to rest on the bottom of a body of water to oppose the buoyancy oi the hull, said winch being supported by the hull, said tentacle being connected at one end to its weight and at its other end to its winch; and sensing and operating means for each ballast tank actuated by tension of its cable and operating the inlet and outlet means of its ballast tank to maintain said deck in a fixed horizontal plane.

3. In a buoyant type of platform of the character described comprisinga buoyant hull and a working deck supported. by the hull, and buoyancy control elements having means for increasing and decreasing the buoyancy of the hull to maintain said working deck in a fixed, horizontal plane notwithstanding the ebb and flow of tides and other factors tending to lift or lower the working deck, the improvement which comprises cables each connected at one end to said platform, a weight connected to the other end of each said cable, said weights being adapted to rest on the bottom of a body of water to oppose the buoyancy of the hull, sensing means for sensing the tension in each cable and control means actuated by said sensing means to operate said means for increasing and decreasing the buoyancy to maintain the working deck in said plane.

4. In a buoyant type of platform of the character described comprising a buoyant hull and a working deck supported by the hull, and buoyancy control elements in the form of ballast tanks and an inlet valve and an outlet pump for each such tank for decreasing and increasing the buoyancy of the hull, respectively, to maintain said working deck in a fixed, horizontal plane notwithstanding the ebb and fiow of tides and other factors tending to lift or lower the working deck, the improvement which comprises cables each connected at one end to said platform, a weight connected to the other end of each said cable and lying on the bottom of a body of water, sensing means for sensing the tension in each cable and control means actuated by said sensing means to operate said valves and pumps to maintain the working deck in said plane.

5. 'In a buoyant type of platform of the character described comprising a buoyant hull and a working deck supported by the hull and buoyancy control elements for increasing and decreasing the buoyancy of the hull to maintain said working deck in a fixed, horizontal plane notwithstanding the ebb and how of tides and other factors tending to lift or lower the working deck, the improvement which comprises cables each connected at one end to said platform, a weight connected to the other end of each said cable and lying on the bottom of a body of water, sensing means for sensing the tension in each cable, said sensing means being in the form of a lever pivoted by movement of such cable and pressureresponsive means operated by said lever to operate said buoyancy control elements to maintain the working deck in said plane.

6. A platform of the character described comprising a superstructure, a hull and a buoyancy control system; said hull having a buoyant compartment and a plurality of ballast compartments symmetrically arranged in relation to the vertical axis of the platform; said buoyancy control system comprising an inlet valve and an outlet pump for each ballast tank, a weight and a cable for each ballast tank, one end of each cable being connected to its weight, automatic weighing means for each cable adopted to sense the tension in the respective cable, said automatic weighing means being in operative relation to its cable to continuously sense its tension and control means actuated by variations in the cable tensions, said control means operating to maintain the tension of each cable between predetermined upper and lower limits by opening the inlet valve of each ballast compartment when its cable tension exceeds the predetermined upper limit and by operating the outlet pump of each ballast compartment when its cable tension slackeus below the predetermined lower limit.

7. A platform structure of the character described comprising a buoyant hull having a plurality of symmetrically arranged ballast tanks each having an inlet valve and an outlet pump, and a superstructure supported by the hull, first and second weights for each ballast tank and a first, ballast controlled cable and a second, winch controlled cable for said first and second weights, re spectively; a winch for each winch controlled cable and a reversible motor for each such winch; a cable tension sensing means for each cable, said sensing means being in operative relation to its cable to sense the tension thereof; and control means whereby the sensing means associated with each ballast controlled cable controls the inlet valve and outlet pump of the respective ballast tank to maintain the respective cable tension between predetermined upper and lower limits, said control means being also operable, whenever a ballast controlled cable breaks, to shift control of the buoyancy of the structure to the winch cables.

8. A buoyant platform structure comprising a buoyant hull, a superstructure and a plurality of symmetrically arranged ballast tanks each having inlet means and outlet means; a ballast operated cable means and a winchoperated cable means for each ballast tank; each said ballast operated cable means comprising a first cable, a weight connected to one end thereof and adapted to lie on the bottom of a body of water, a winch connected to the other end of said first cable, a reversible motor for operating said winch, and cable tension sensing means operated by said first cable to sense the tension thereof; control means normally connecting each said first cable tension sensing means to the inlet means and outlet means of the respective ballast tank to cause inflow of water when the tension of the respective first cable exceeds a predetermined upper value and to cause outflow of water when such tension falls below a predetermined lower value; each said winch operated cable means comprising a second cable, a weight connected to one end thereof and adapted to lie on the bottom of a body of water, a winch connected to the other end of said second cable, a reversible motor for operating said winch, and cable tension sensing means operated by said second cable to sense the tension thereof; said control means normally connecting each said second cable tension sensing means to the respective winch motor to maintain the respective second cable between predetermined upper and lower tension limits; said control means being also operable, whenever one of said first cables breaks, to connect the cable tension sensing means of the second cables with the inlet means and outlet means of the ballast tanks.

References Cited in the file of this patent UNITED STATES PATENTS 1,334,445 Gaiiney Mar. 23, 1920 1,678,472 Johnson July 24, 1928 1,892,125 Armstrong Dec. 27, 1932 2,147,761 Whitcomb Feb. 21, 1939 2,238,974 Creed Apr. 22, 1941 2,244,830 Doe et al. June 10, 1941 2,248,051 Armstrong July 8, 1941 2,399,656 Armstrong May 7, 1946 2,723,833 Burfeind Nov. 15, 1955 2,839,021 Patterson June 17, 1958