US3649978A - Stabilized semi-submersible platform - Google Patents

Stabilized semi-submersible platform Download PDF

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Publication number
US3649978A
US3649978A US883723A US3649978DA US3649978A US 3649978 A US3649978 A US 3649978A US 883723 A US883723 A US 883723A US 3649978D A US3649978D A US 3649978DA US 3649978 A US3649978 A US 3649978A
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US
United States
Prior art keywords
support
horizontal
swell
supports
horizontal element
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Expired - Lifetime
Application number
US883723A
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English (en)
Inventor
Georges Monnereau
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Compagnie Generale dAutomatisme SA
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Compagnie Generale dAutomatisme SA
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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
    • B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING 
    • B63B39/00—Equipment to decrease pitch, roll, or like unwanted vessel movements; Apparatus for indicating vessel attitude
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
    • B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING 
    • B63B35/00—Vessels or similar floating structures specially adapted for specific purposes and not otherwise provided for
    • B63B35/44—Floating buildings, stores, drilling platforms, or workshops, e.g. carrying water-oil separating devices
    • B63B35/4413—Floating drilling platforms, e.g. carrying water-oil separating devices
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
    • B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING 
    • B63B39/00—Equipment to decrease pitch, roll, or like unwanted vessel movements; Apparatus for indicating vessel attitude
    • B63B39/06—Equipment to decrease pitch, roll, or like unwanted vessel movements; Apparatus for indicating vessel attitude to decrease vessel movements by using foils acting on ambient water
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
    • B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING 
    • B63B1/00—Hydrodynamic or hydrostatic features of hulls or of hydrofoils
    • B63B1/02—Hydrodynamic or hydrostatic features of hulls or of hydrofoils deriving lift mainly from water displacement
    • B63B1/10—Hydrodynamic or hydrostatic features of hulls or of hydrofoils deriving lift mainly from water displacement with multiple hulls
    • B63B1/107—Semi-submersibles; Small waterline area multiple hull vessels and the like, e.g. SWATH
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
    • B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING 
    • B63B1/00—Hydrodynamic or hydrostatic features of hulls or of hydrofoils
    • B63B1/02—Hydrodynamic or hydrostatic features of hulls or of hydrofoils deriving lift mainly from water displacement
    • B63B1/04—Hydrodynamic or hydrostatic features of hulls or of hydrofoils deriving lift mainly from water displacement with single hull
    • B63B2001/044—Hydrodynamic or hydrostatic features of hulls or of hydrofoils deriving lift mainly from water displacement with single hull with a small waterline area compared to total displacement, e.g. of semi-submersible type

Definitions

  • U S Cl 9/8 P platform is achieved through floating supports whose length is 51 I .t .Cl substantially greater than their diameter closed at heir base 1 and vertically oriented witha cylindrical horizontal member 58 Field of Search ..9/s R, 8 OP, 114 05, 230, on which the swell acts fixed to the base to compensm the am 114/435, 121, 140, I22, 124, 126; 61/46' gular movement it produces on the vertical supports and to position the platform in relation to the direction of its propagation.
  • the present invention involves a device for angular stabilization and orientation of a semi-submersible platform sub-
  • the present invention concerns a semi-submersible plat- 5 lected a Swen, including at least one Partially submerged form including semi-immersed supports in the form of closed, hollow vertical cylinders holding the platform out of the water, and relates more particularly to the attachment to each support of means for improving the angular stability of the said platform in a swell, these means having a generally cylindrical form, with their generatrices horizontal.
  • the swell also exerts an orientation action on such a structure.
  • the system of forces applied to a semi-submersible platform by the action of the swell reduces to an alternating resultant force whose vertical component gives the platform an alternating translation movement or bobbing motion characterized by its amplitude and frequency.
  • the horizontal component exerts an alternating couple giving the structure an oscillator movement about the vertical, characterized by its angular amplitude and its frequency.
  • the swell may be represented as exerting an oriented action on the platform, each point of which oscillates in a substantially vertical plane, parallel to the direction of the swell. This is why the swell does not exert the same effect on all parts of the disc elements mentioned above.
  • the surface portion of the disc furthest removed from its axis, following the direction of the swell provide the most important fraction of the correcting couple.
  • the invention employs for the stabilization of a platform with semi-immersed vertical supports, a surface extending along a horizontal direction, rather than a disc-like surface having its axis of symmetry vertical.
  • the geometric asymmetry of a surface is thus adapted to the asymmetry of behavior of the two components of the swell, presenting an improved stabilization.
  • an elongated correcting surface has the property of orienting itself in the direction of the swell, since the asymmetrical action of the swell on the extremities of the said surface generate, in effect, a restoring couple about a vertical axis.
  • the platform' thus adopts a preferred direction with respect to the swell such that when it moves away from this direction, the stabilization surfaces return it thereto.
  • the damping of the angular oscillations is improved while the bobbing motion remains the same, being independent of the orientation.
  • this orientation device it is possible to obtain with this orientation device the same stabilization of a platform for a bobbing motion less than in case of known devices.
  • a practical realization of such an elongated stabilization surface consists in using a cylindrical tubular form with horizontal generatrices and preferably open at its extremities. Under the action of the swell, the platform turns until these generatrices are parallel to the direction of the swell, and in these conditions there is obtained, for a given swell, a stabilization of angular movement and heading, with attenuation of the bobbing motion.
  • the wavelength of the swell changes, the disturbing couple varies and there is no longer angular movement compensation, the position of the platform s center of gravity is varied, by means of counterweights movable along the vertical supports, thus modifying the floating support of elongated form with substantially vertical axis of symmetry, being hollow and closed at its base.
  • Each support is provided with at least one horizontal element of generally tubular form fixed near the base of the support.
  • the device is characterized in that the dimensions and depth of submersion of each horizontal element and the cross-section of each support near the liquid surface are so chosen that the action of the swell on each horizontal element of each support produces a first couple compensating a disturbing couple produced by the swell on the corresponding support, and a second couple tending to orient said horizontal element or elements with respect to the swell; and in that each support is provided with a counterweight adjustable to make the value of the corresponding disturbing couple equal to the corresponding first couple.
  • FIG. 1a shows a vertical cylindrical support device provided with a cylindrical compensator element with horizontal generatrices
  • FIG. lb is a section on the line and in the direction of the arrows x-x of FIG. 1;
  • FIG. 2 is a diagram of a compensator cylinder device having an open portion of the side opposite the water surface;
  • FIG. 3 is a diagram of a vertical support device formed by two cylinders of different diameters
  • FIG. 4 is an elevation of a monopod platform with conipensator element formed by three cylinders arranged in starlike configuration
  • FIG. 5 is a view from above and in horizontal projection of the compensator cylinders of FIG. 4;
  • FIGS. 6, 7 and 8 show in horizontal projection the compensator cylinders, in parallel, star-like and triangular configurations respectively, of a device with a tripod support device;
  • FIG. 9 is a view of a system with two vertical supports (dipode) in which the compensator cylinders are placed in parallel;
  • FIG. 10 is a view of a system with two vertical supports, each support carrying a star-like configuration compensator element, these elements being arranged to have a common branch joining the two supports.
  • a hollow cylindrical support 1 is provided at its base with a cylinder 2 with horizontal generatrices and intended to compensate the angular movement produced by the action of the swell on the cylinder 1.
  • the assembly is in equilibrium in water of mean level 3, since the resultant of the buoyancy forces, applied at P, is equal to the resultant of the weights, applied at the center of gravity G.
  • the position of the point G, arranged above the point P so that the equilibrium is stable, depends on the relative positions of the platform fixed above level 3, the cylinder 1, and a counterweight located above the cylinder 2, the platform and counterweight not being shown in the Figure.
  • the cylinder 1b In FIG. lb, the cylinder 1b, the cylinder 1 is closed at its lower extremity by the lateral surface of the cylinder 2. The sealing of the cylinder 1 is assured by welding fillets 4, providing the rigid assembly of the two cylinders.
  • the cylinder 2 is preferably open at its two extremities and can be partitioned without prejudicing the orientation of the device about the line x-x by the swell bringing the generatrices of the cylinder 2 into line with its propagation direction.
  • the cylinder 2 is cutaway in that portion opposite the water surface 3, with a window 5 thus eliminating the portion of the surface least subjected to pressure changes caused by the swell.
  • the portions 6 have been kept since at the extremities the lower surface portions of the cylinder 2 are more affected by the swell, in participating in the compensating action.
  • the floating vertical support is in two parts la and lb, the latter being below and having a greater diameter than the former. There is thus obtained a floating support which is more buoyant and able to carry a heavier platform.
  • the compensator device is divided into three cylinders 7 with horizontal axes spaced in star-like configuration around a vertical support 8, to which they are welded by means of auxiliary corner-plates 9.
  • the platform is shown diagrammatically as closed and provided with openings 11.
  • Counterweights 12 located near the lower extremity of the floating support 8 permit the center of gravity G of the assembly to be brought below the buoyancy center P.
  • the counterweights 12 are fixed to vertical rods 13 movable in guides 14 by a winch 15.
  • the direction of propagation of the swell that is the direction in which the wave 16 (FIG. 4) moves, is represented by the arrow 17.
  • the orientation action of the swell on the device with star-like configuration of the cylinders 7 involves a rotation of the device through an angle of less than 30 so as to make the axis of the cylinder 7 nearest to the direction 7 coincident with this direction; the other two cylinders 7 arrive in positions'symmetrically disposed about the direction 17.
  • any variation of the wavelength produces a modification of the disturbing couple.
  • This disturbing couple caused by the horizontal component of the resultant of the hydrodynamic forces acting on the floating support, is returned to its basic value by adjustment of the counterweights.
  • the length of the corresponding lever arm is modified, that is to say, the position of the center of gravity G is modified.
  • the bulk of the compensation system with cylinders arranged in star-like configuration is of substantially the same order of magnitude as that of the equivalent single cylinder.
  • FIG. 6 the compensator cylinders 19 mounted on the supports 18 are parallel; in FIG. 7 a star-like configuration of the cylinders 20 has been adopted; while in FIG. 8, the compensator cylinders 27 are triangularly arranged.
  • each floating support 22 At the base of each floating support 22 is arranged a single compensator cylinder 23, the cylinders 23 being parallel.
  • a compensator cylinder device for each floating support 24 a compensator cylinder device has been adopted wherein the compensator cylinders 25 are arranged in star-like configuration, two colinear branches being combined in the form of a common cylinder Calculations and experiments have allowed a determination to be made, for a swell wavelength of 200 meters, of the ranges in which the compensator cylinder device parameters lie.
  • d is between 0.4 and 6 meters
  • L is between 5 and 30 meters
  • l is between 2 and 8 meters
  • h is between 4 and 30 meters
  • an increase in the tonnage of a monopod platform may be obv tained, for values increasing to 1,000 to 1,500 metric tons, by the following means:
  • the compensator cylinders are shown open at their extremities, but they can be closed without losing their orientation effects. Similarly in the median part of a compensator cylinder of closed cross-section, bulkheads may be installed without influencing the orientation effects due to these extremities.
  • a device for angular stabilization and orientation of a semi-submersible platform subjected to a swell including at least one partially submerged floating support of elongated form with substantially vertical axis of symmetry, being hollow and closed at its base, and each support being provided with at least one horizontal element of generally tubular form fixed near the base of the support; the improvement wherein: the dimensions and depth of submersion of each horizontal element and the cross-section of each support near the liquid surface are so chosen that the action of the swell on each horizontal element of each support produces a first couple compensating a disturbing couple produced by the swell 0n the corresponding support, and a second couple tending to orient said horizontal element with respect to the swell; each horizontal element is open at its extremities and has a crossseetion in the form of a closed curve, and said device further includes a counterweight for each support, and means for adjusting the position of said counterweight to make the value of the corresponding disturbing couple equal to the corresponding first couple.
  • each horizontal element has a central portion with a cross-section in the form of a curve open at the side opposite the liquid surface.
  • each support is provided with two cylindrical horizontal elements, the sum of the horizontal projections of their surfaces being equal to .that of the single cylinder.
  • the angular stabilization and orientation device wherein: the support is a cylinder and said cylindrical horizontal elements number three and are equally spaced around the axis of symmetry of said support.
  • angular stabilization and orientation device according to claim 1, wherein said device includes three supports disposed at the apices of a triangle and each is provided with a cylindrical horizontal element with the three horizontal elements being arranged in a triangular configuration.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • Ocean & Marine Engineering (AREA)
  • Architecture (AREA)
  • Civil Engineering (AREA)
  • Structural Engineering (AREA)
  • Earth Drilling (AREA)
  • Cleaning Or Clearing Of The Surface Of Open Water (AREA)
  • Monitoring And Testing Of Nuclear Reactors (AREA)
US883723A 1968-12-10 1969-12-10 Stabilized semi-submersible platform Expired - Lifetime US3649978A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
FR177486 1968-12-10

Publications (1)

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US3649978A true US3649978A (en) 1972-03-21

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US883723A Expired - Lifetime US3649978A (en) 1968-12-10 1969-12-10 Stabilized semi-submersible platform

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US (1) US3649978A (xx)
BE (1) BE742811A (xx)
DE (1) DE1961943A1 (xx)
ES (1) ES374425A1 (xx)
FR (1) FR1594989A (xx)
GB (1) GB1266750A (xx)
LU (1) LU59969A1 (xx)
NL (1) NL6918501A (xx)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4112864A (en) * 1976-10-08 1978-09-12 Seatek Corporation Heave stabilization of semi-submersible platforms
US20050166433A1 (en) * 2003-11-25 2005-08-04 Barlow William R. Inflatable display apparatus

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2153885B (en) * 1984-02-01 1988-04-07 Compagnon Jean Pierre Jacques Stabilised floating platform

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2944267A (en) * 1958-07-08 1960-07-12 Kurtz Mark Buoy
US3089157A (en) * 1960-08-11 1963-05-14 Gordon H May Fin for water skis
US3159130A (en) * 1962-02-26 1964-12-01 Shell Oil Co Floating storage tank
US3490406A (en) * 1968-08-23 1970-01-20 Offshore Co Stabilized column platform

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2944267A (en) * 1958-07-08 1960-07-12 Kurtz Mark Buoy
US3089157A (en) * 1960-08-11 1963-05-14 Gordon H May Fin for water skis
US3159130A (en) * 1962-02-26 1964-12-01 Shell Oil Co Floating storage tank
US3490406A (en) * 1968-08-23 1970-01-20 Offshore Co Stabilized column platform

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4112864A (en) * 1976-10-08 1978-09-12 Seatek Corporation Heave stabilization of semi-submersible platforms
US20050166433A1 (en) * 2003-11-25 2005-08-04 Barlow William R. Inflatable display apparatus
US7240445B2 (en) * 2003-11-25 2007-07-10 William Richard Barlow Inflatable display apparatus

Also Published As

Publication number Publication date
GB1266750A (xx) 1972-03-15
ES374425A1 (es) 1972-01-01
FR1594989A (xx) 1970-06-08
LU59969A1 (xx) 1971-08-17
NL6918501A (xx) 1970-06-12
DE1961943A1 (de) 1970-09-10
BE742811A (xx) 1970-06-08

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