EP0192311A2 - A method of placing a platform on a support structure surrounded by water, in particular in high seas, and a vessel for carrying out said method - Google Patents

A method of placing a platform on a support structure surrounded by water, in particular in high seas, and a vessel for carrying out said method Download PDF

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Publication number
EP0192311A2
EP0192311A2 EP86200278A EP86200278A EP0192311A2 EP 0192311 A2 EP0192311 A2 EP 0192311A2 EP 86200278 A EP86200278 A EP 86200278A EP 86200278 A EP86200278 A EP 86200278A EP 0192311 A2 EP0192311 A2 EP 0192311A2
Authority
EP
European Patent Office
Prior art keywords
platform
vessel
support structure
relatively
rods
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP86200278A
Other languages
German (de)
English (en)
French (fr)
Inventor
Cornelis Bordes
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.)
GustoMSC BV
Original Assignee
Marine Structure Consultants MSC BV
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Marine Structure Consultants MSC BV filed Critical Marine Structure Consultants MSC BV
Publication of EP0192311A2 publication Critical patent/EP0192311A2/en
Withdrawn legal-status Critical Current

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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 
    • B63B35/00—Vessels or similar floating structures specially adapted for specific purposes and not otherwise provided for
    • B63B35/003—Vessels or similar floating structures specially adapted for specific purposes and not otherwise provided for for transporting very large loads, e.g. offshore structure modules
    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02B—HYDRAULIC ENGINEERING
    • E02B17/00—Artificial islands mounted on piles or like supports, e.g. platforms on raisable legs or offshore constructions; Construction methods therefor
    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
    • E02D29/00—Independent underground or underwater structures; Retaining walls
    • E02D29/06—Constructions, or methods of constructing, in water

Definitions

  • This invention relates to a method of placing a platform on a support structure which, on the one hand, is anchored in the bottom under a body of water surrounding the support structure and, in particular in high seas, and, on the other hand, extends to above the water surface.
  • a platform must be positioned in a relatively deep body of water, such a method of installation is no longer feasible on account of the required length of the legs.
  • a leg is built up from segments, which are separately and successively lowered and mounted one on top of the other.
  • the working platform which may weigh as much as 20,000-60,000 tonnes, is also supplied in segments, which by means of a derrick are placed in position and interconnected to form a platform. Placing a platform on a support structure in this manner is labour-intensive, resulting in a long construction period, which is further adversely affected by the difficult and spatially restricted conditions under which the work must be carried out. Indeed, such a method involves very high cost.
  • this is achieved in a method of the kind defined in the opening paragraph by placing the platform in its totallity on a semi-submersible vessel adapted to carry the platform in such a manner that the place or places where the support structure is to engage it is or are situated on a part of the platform that is not supported by said vessel, moving the vessel into such a position that the bottom of the platform is generally above the level of the top of the support structure, moving the vessel between and/or around the support structure and mooring it in a position in which the platform is roughly in proper position relative to the support structure, arranging for the platform to be movable relatively to the vessel in a horizontal plane with relatively light forces by releasing locking means and activating means suitable for the purpose, accurately positioning the platform relatively to the support structure by automatic steering and correcting means, and, while keeping the platform accurately in position, submerging the vessel at least until the platform is placed on the support structure.
  • the load is arranged to be relatively easily movable relatively to the vessel, by suitable means, and accurately positioned relatively to the fixed support structure by the steering and correcting means.
  • This position is continuously maintained by the means referred to during the submerging of the vessel, so that any movements of the vessel which may occur during the submersion operation, other than the submerging movements themselves, for example, as a result of rough water, are continuously corrected.
  • the method according to the invention makes it possible for the platform to be bodily placed on the support structure in accurately positioned interrelationship, and to be subsequently connected to it.
  • Wave movements occurring during the submerging of the vessel may cause the platform to bump against the support structure, in which connection it should be borne in mind that the submerging operation is a process that is relatively slow, at any rate as compared with the movements of the water, so that the actual deposition will take some time, and, after a first contact has been made between platform and support structure, wave movements may cause these two parts to come apart again.
  • spring means or damping means are arranged between the platform and the support structure, while further, the arrangement may be such that, as the platform is being supported by the support structure during the descent of the vessel, spring means and/or damping means become active between the platform and the vessel.
  • the desired accurate interrelationship between platform and support structure can advantageously be maintained by means of, or with the help of vertical guide means, for example, in the form of pins, disposed between the platform and the support structure after the platform has been accurately positioned relatively to the support structure.
  • the invention also relates to a vessel for performing the method according to the invention, said vessel being semi-submersible and comprising an upper pontoon, at least one lower pontoon, and members, such as columns and struts or other cross connection pieces interconnecting the upper and lower pontoons.
  • the vessel accordinging to the invention has a recess open to one side, with box-shaped sidewalls meeting said side and capable of supporting the platform at least for the greater part.
  • the open-ended recess makes it possible for the vessel to manoeuvre its box-shaped sidewalls around the support structure, so that the latter comes to lie within the outer circumference of the vessel and under the platform.
  • the box-shaped construction of the sidewalls meeting the sidewall with the recess therein has the further advantage that the centre of buoyancy can be situated substantially in the centre of the recess and/or centrally under the platform, which has advantages in submerging the vessel and depositing the platform on the support structure.
  • the platform For the platform to be arranged to be movable relatively to the vessel with relatively light forces, so that it may be accurately positioned relatively to the support structure, a great variety of means may be used. Thus slides may be interposed between the vessel and the platform, or a rolling ball support for the platform may be provided on the vessel.
  • the vessel is characterized by the provision of at least two, substantially vertically extending rods in each sidewall, said rods being pivoted at their lower end to a support and pivoted at their upper end to a platform supporting structure interconnecting the rods. Owing to these features, the platform is supported on the vessel in a manner comparable to the situation described above, in which a load hangs from a derrick.
  • the substantially vertically extending rods can be regarded as "inverse" derrick cables, by virtue of which the platform to be deposited can be accurately positioned in the same, relatively simple manner as is the case with a load hanging from a derrick.
  • the height of the sidewalls of the semi-submersible vessel may be in the order of 30 meters, so that, as a result of the long lever arm, a relatively light force is required for displacing the platform.
  • the rods are, to a certain extent, capable of twisting about their longitudinal axis at their ends.
  • the available lever arm length can be increased still further if, in accordance with a further embodiment of the invention, the supports connected to the lower ends of the rods are suspended by means permitting twisting and/or pivoting movement, such as cables secured adjacent the top of the sidewalls.
  • the platform can now be accurately positioned by using means disposed on the vessel in a stationary position relative to the platform, there being a preference for a construction in which the platform carrying structure is movable in a horizontal plane in two perpendicular directions and about a vertical axis by controlled hydraulic means.
  • Fig. 1 diagrammatically shows a semi-submersible vessel 1.
  • the vessel comprises an upper pontoon la, which also forms a deck, two elongaged lower pontoons lb, columns lc connecting upper and lower pontoons, two of which are extended to form box-shaped outer walls 1d.
  • a platform 2 is placed substantially on the tops of the box-shaped sidewalls ld.
  • Platform 2 is to be placed on a support structure 3, which in the embodiment shown is constituted by a single leg anchored in the bottom.
  • a support structure 3 which in the embodiment shown is constituted by a single leg anchored in the bottom.
  • other constructions are possible, such as four legs.
  • Fig. 3 shows the situation in which vessel 1 is positioned so that the support structure 3 is substantially centrally under platform 2, which, roughly, is in a correct position relative to support structure 3.
  • support structure 3 is within a U-shaped recess of vessel 1, defined by the box-shaped sidewalls ld and the meeting edge of the upper pontoon la.
  • the submersible vessel 1 is moored and the platform 2 is arranged, by means to be described hereinafter, so that it can be moved relatively to the platform in a horizontal plane with light forces.
  • the platform 2 is accurately positioned relatively to support structure 3, and spring means, to be described hereinafter, are interposed between platform 2 and support structure 3.
  • platform 2 After platform 2 has been accurately positioned relatively to support structure 3, this position is continuously maintained by means of the steering and correcting device.
  • platform 2 By partially submerging vessel 1, platform 2 is now placed on support structure 3, whereby platform 2 is released from vessel 1, as shown in Fig. 4. After weighing anchors, vessel 1 can move off.
  • Fig. 5 shows the top end of support structure 3, and illustrates lugs 4 provided at the top end of the support structure, on which spring and/or damping means 5 can bear which on the other hand form a support for platform 2.
  • platform 2 can be placed on the support structure 3 without major shocks or bumps by submerging vessel 1.
  • the spring and/or damping means and possibly lugs 4 can be removed.
  • Fig. 6 shows platform 2 supported on a platform carrying construction 6 supported by at least four rods 7 extending substantially vertically within the box-shaped sidewalls ld.
  • the connection between the platform carrying construction 6 and the ends of rods 7 can be effected by means of hinges, but we preferably use a resilient joint which, in addition to pivoting, also permits a certain amount of twisting.
  • rods 7 are each connected at their lower ends to a support 8 which in turn is suspended by means of cables 9, the upper ends of which are fixedly connected to, or in the vicinity of the upper ends of the box-shaped sidewalls ld.
  • the platform carrying construction 6 is fixed by locking means, not shown, so that platform 2 is restrained from moving relatively to vessel 1.
  • Fig. 1 shows the platform carrying construction 6 in plan view.
  • Four hydraulic cylinders 10-13 may be in operative association with the platform carrying construction and/or rods 7 so that the platform 2, not shown, is movable relatively to vessel 1 in a horizontal plane in any desired direction.

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Civil Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Structural Engineering (AREA)
  • Transportation (AREA)
  • Combustion & Propulsion (AREA)
  • Mining & Mineral Resources (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Environmental & Geological Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Paleontology (AREA)
  • Ocean & Marine Engineering (AREA)
  • Ship Loading And Unloading (AREA)
  • Bridges Or Land Bridges (AREA)
  • Other Liquid Machine Or Engine Such As Wave Power Use (AREA)
  • Toys (AREA)
  • Containers And Packaging Bodies Having A Special Means To Remove Contents (AREA)
  • Earth Drilling (AREA)
EP86200278A 1985-02-22 1986-02-21 A method of placing a platform on a support structure surrounded by water, in particular in high seas, and a vessel for carrying out said method Withdrawn EP0192311A2 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
NL8500509 1985-02-22
NL8500509A NL8500509A (nl) 1985-02-22 1985-02-22 Werkwijze voor het plaatsen van een platform op een steunconstructie omringd door water, in het bijzonder een open zee.

Publications (1)

Publication Number Publication Date
EP0192311A2 true EP0192311A2 (en) 1986-08-27

Family

ID=19845575

Family Applications (1)

Application Number Title Priority Date Filing Date
EP86200278A Withdrawn EP0192311A2 (en) 1985-02-22 1986-02-21 A method of placing a platform on a support structure surrounded by water, in particular in high seas, and a vessel for carrying out said method

Country Status (7)

Country Link
EP (1) EP0192311A2 (fi)
JP (1) JPS61246413A (fi)
KR (1) KR860006604A (fi)
BR (1) BR8600867A (fi)
FI (1) FI860742A (fi)
NL (1) NL8500509A (fi)
NO (1) NO860515L (fi)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2003066425A1 (en) * 2002-02-08 2003-08-14 Master Marine As Method for use in offshore load transfer, and a floater and hydraulic device for the same

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2003066425A1 (en) * 2002-02-08 2003-08-14 Master Marine As Method for use in offshore load transfer, and a floater and hydraulic device for the same

Also Published As

Publication number Publication date
KR860006604A (ko) 1986-09-13
BR8600867A (pt) 1986-11-11
NO860515L (no) 1986-08-25
JPS61246413A (ja) 1986-11-01
FI860742A (fi) 1986-08-23
FI860742A0 (fi) 1986-02-19
NL8500509A (nl) 1986-09-16

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Inventor name: BORDES, CORNELIS