Marine structure

Details Marine structure Marine structure

2000-10-02

2002-12-03

Will, Thomas B. (Department: 3671)

Hydraulic and earth engineering

Marine structure or fabrication thereof

Floatable to site and supported by marine floor

C405S224100, C114S296000

Reexamination Certificate

active

06488446

ABSTRACT:

BACKGROUND OF THE INVENTION
The invention is concerned with a marine structure, a suction pile and a method for installing a marine structure. The invention is particularly, though not exclusively, directed to the application of so called “minimal platforms”.
DESCRIPTION OF THE RELATED ART
It is common to position a marine structure pre-assembled or in separate parts onto one or more barges or pontoons in a harbour and then tug said pontoons to the location of destination, whereafter the structure is lifted from the pontoons with the aid of a separate hoisting device and is then the structure is installed on the subsea bottom with the aid of that device, wherein prior to or after installing the structure onto the subsea bottom, a foundation therefor is made with the aid of a separate foundation pile ramming device.
Suction piles and their way of installing are o.a. known from GB-B-2300661 and EP-B-0011894, which desclosures are enclosed here by reference. Briefly, a suction pile is a thin walled steel cylinder, closed at at least one longitudinal end, that is located on the subsea bottom with the opposite end and penetrates the subsea bottom with the aid of a suction created within the cylinder. The creation of the suction can be with the aid of a suction source, such as a pump, being on, or close to or at a distance (e.g. above the water surface, e.g. at a vessel) from the suction pile. The applied level of the suction can be e.g. at least substantially constant, smoothly increase or decrease or else pulsate, for which there are convenient means; for an e.g. pulsating level a possibly in the suction pile integrated pressure accumulator that is intermittendly connected to the inner space of the cylinder. After use, the suction pile can easily be removed by creating an overpressure within the cylinder, e.g. by pumping in (sea) water.
SUMMARY OF THE INVENTION
According to one aspect the invention proposes to make the marine structure self floating and self foundating by providing it with buoyancy and one or more suction piles. So the hoisting device and the foundation plant can be eliminated. Preferably the structure has buoyancy of its own, e.g. obtained by the with the structure integrated appliance that is designed to, once the structure is installed, ballast the structure. Buoyancy can also be obtained from the suction pile, which for that can be provided with a floater. Said own buoyancy is preferably such that it is substantially contributing to the required buayancy to make the structure self floating. It is preferable, if the buayancy can be at least substantially decreased for installation purposes. By e.g. filling the one or more floating bodies with ballast, like water. Therefor it is convenient, to provide the structure with means for admitting and possibly removing of ballast, such as between the closed and open position switchable shutter valves in a water supplying respectively water venting opening to a ballast tank.
Since the structure is self floating and is provided with one or more suction piles, removal after use is made easier. On the one hand in that by pressing out the suction pile, the anchoring of the structure to the underwater bottom can be removed. On the other hand in that the structure can independently rise to the water surface by the (possibly regained) buoyancy.
The marine structure will typically be relatively small in this connection, e.g. a production platform with appliances. Because of its own weight, such a marine structure is designed to be used with a foundation of pile bodies to be rammed into the ground. Apart from the suction piles, such marine structure has, preferably, no floating bodies, neglecting parasitic floating bodies like ineviatbly present air filled spaces, such as frame tubes. The marine structure referred to here typically will weigh not more than about 50 tonnes.
Now it is no longer necessary to position the marine structure onto a barge for transport over water. This offers further advantages since the marine structure does not need to be lifted from the barge by a hoisting device. If the suction pile offers at least part of the required buoyancy, the marine device can be provided with fewer floating structures especially provided for said purpose, or such floating structures can even be eliminated.
As such, savings of costs, time, energy, environment and materialare possible and one can also work safer.
According to another aspect, the invention proposes to use the suction pile, or part thereof, as floating body of which the buoyancy is preferably adapted to keep itself floating. In this way it is e.g. possible, to take a suction pile independently floating in te water to its final destination, so without help of one or more auxiliary. floaters. Reclaiming such a suction pile is also made easier. On the one hand in that this can free itself independently from the subsea bottom with its buoyancy, once pressed upwardly but still partly standing in the subsea bottom. On the other hand since it can rise to the water surface independently. In particular the buoyancy of the suction pile according to the invention is substantially larger than its own weight, e.g. such that the suction pile alone or in combination with one or more other suctions piles substantially contributes to the marine structure with which it is integrated. Accordingly the invention proposes to provide the suction pile with a convenient buoyancy means.
The buoyancy means can be at least substantially comprise a space in open communication with the surrounding water at its under side, such as the pressure space of the suction pile, e.g. if the suction pile will at least as much upright as possible float in the water. If one can keep said space free of water to a satisfying level, the desired buoyancy can be maintained without requiring to delimit this floating space at all sides with respect to the water environment. Said space can therefor e.g. be connected to a convenient means, such as for delivering a gas generating dry compound into said space, or for delivering into said space a pressurised gas, such as a pump, to generate a convenient gas pressure in the suction space and to possibly maintain it against the pressure of the surrounding water. Due to the movements of the floating suction pile in the water, it is expected that without counter measurements this space will be filled more and more with water from below. A remedy is to continuously or intermittendly removing of the flowing in water by e.g. refilling said space with gas, for which said above mentioned means is/are continuously or intermittendly activated. In this connection it is preferred to integrate this means in an active, preferably automatic, e.g. electronic control circuit wherein said means is activated in dependency from the detection of the buoyancy of the suction pile at different times, such as by measuring e.g. the water level or e.g. the gas pressure within said space with e.g. a convenient sensor, outputting its measuring signal to an evaluation device comparing the measuring signal with an input value, switching on or letting switching on said means to get back to the initial situation once a treshold difference value is exceeded.
Application of the above described space in open communication with its surrounding water has drawbacks in view of ensuring the buoyancy. Its is therefor preferable if said buoyancy provides one or more floating spaces that are delimited at all sides with respect to the water environment and that are filled with a floating substance, such as air or a gas or some other material of relatively low specific weight. Said floating means can comprise e.g. a separate, inflatable, completely closed, diafragm type floating body, preferably within the suction pile, e.g. in the suction space. With e.g. a space of the suction pile that is open at its lower side, use can be made of an airtight bulkhead with which said opening can be sealed. If said bulkhead is at least substantially rigid, e.g. of metal, preferably steel, of sufficient thickness, it can withst

Affiliated with

Also associated with

Rating

Marine structure does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Marine structure, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Marine structure will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2997632