Patent Grant
7887262
This application claims priority to Swedish Patent Application 0701218-0, filed with the Swedish Patent Office on May 22, 2007, the entirety of which is incorporated by reference herein.
1. Field
The present embodiments relate to attachments for attaching together a first body and a second body of a marine structure, which marine structure is adapted to be located at least partially immersed in water, wherein at least a portion of each one of the first and second body is adapted to, during use, to be in contact with the water. An attachment can comprise at least a portion of the second body, which comprises a wall which delimits the second body. An attachment can further comprise at least a portion of the first body, wherein the first body is fixedly attached to, and extends from, the second body.
The present embodiments further relate to methods of attaching together a first and second body of a marine structure. Further, the present embodiments relate to a semi-submersible vessel comprising an attachment according to the present invention.
2. Description of the Related Art
Marine structures are generally used for performing work and/or transports at sea or in lakes. For example, marine structures are used for drilling for, and production of, natural recourses such as gas or oil, when the natural recourses for instance are located in a well which is situated below the bottom of an ocean or a lake. Marine structures are also used for quartering personnel working at sea or on a lake.
As an example of marine structures, fixed production platforms may be mentioned, i.e. the type of platform constituted by a framework which is fixedly attached to a sea floor and extends upwardly through the water surface, or floating semi-submersible vessels which comprise a plurality of floats and/or columns. In order to enhance the strength of the marine structure, this is quite often provided with one or more bracings. For example, a semi-submersible vessel which is constituted by two pontoons and four columns may be provided with a bracing extending between the floats and/or the columns in order to make the ship more durable to external loads such as wave loads or internal loads such as for example the dead weight of the ship or pressure from liquids located on the ship.
Traditionally, a bracing is fixedly attached to the outer walls of the parts which are to be joined to one another and the fixed attachment is often achieved by means of a welded joint. Since the outer walls of the parts which are to be joined to one another by the bracing, in the example of a semi-submersible vessel the parts may for instance be pontoons and/or columns, often are adapted to be arranged at least partially immersed in water, often salt water, the weld joints are quite often located in a harsh environment. This makes great demands upon the weld joints and leads to expensive and complicated welding operations in order to achieve weld joints which fulfill the requirements of both extreme and fatigue strength, in particular since the weld joints are adapted to transfer large loads from the bracing to the outer walls. Furthermore, since the weld joints are located beneath the water surface, they may be difficult to inspect and/or repair, which results in that great demands also are made on the working life of the weld joints.
In order to solve this problem, the prior art proposes, for example U.S. Pat. No. 4,771,720, that the bracing is attached to an inner structure of a support column of a semi-submersible vessel. By this solution, a part of the load transfer from the bracing to the column occurs through a weld attachment which is located within the column and which is thus not exposed to the water ambient to the column. U.S. Pat. No. 4,771,720 also discloses that a portion of the bracing is attached to the wall of the column and this attachment is adapted to on the one hand be located in a harsh environment, namely immersed in water, and on the other hand transfer large loads from the bracing to the column. Thus, even if a reduction of the loads which are transferred through the weld attachment located in water is achieved in U.S. Pat. No. 4,771,720, it may still be difficult and expensive to design a weld attachment which is sufficiently strong as regards both extreme and fatigue strength. Furthermore, it is difficult to inspect the weld attachment which is located in water. Moreover, the attachment illustrated in U.S. Pat. No. 4,771,720 is especially suitable for marine structures under construction, or at least an attachment of a new bracing in an existing column.
Thus, a need exists for further improving the attachment of bracings in bodies of marine structures in order to enhance the strength of the joint, in particular as regards the fatigue strength.
So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.
a depicts a side view of a cross-section of yet another embodiment of the attachment.
b depicts a front view of the embodiment illustrated in
A detailed description will now be provided. Each of the appended claims defines a separate invention, which for infringement purposes is recognized as including equivalents to the various elements or limitations specified in the claims. Depending on the context, all references below to the “invention” may in some cases refer to certain specific embodiments only. In other cases it will be recognized that references to the “invention” will refer to subject matter recited in one or more, but not necessarily all, of the claims. Each of the inventions will now be described in greater detail below, including specific embodiments, versions and examples, but the inventions are not limited to these embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the inventions, when the information in this patent is combined with available information and technology.
A first object of the present invention is to provide an attachment between a first body to a second body of a marine structure, wherein a load transfer between the first and second bodies mainly occurs through joints which are adapted to not be in contact with the water ambient to the marine structure.
A second object of the present invention is to provide an attachment between a first body and a second body of a marine structure, wherein the joints which are a part of the attachment and which are adapted to be located in water may be designed in a simple and cost efficient way, but nevertheless fulfill requirements on the strength, in particular the fatigue strength.
A third object of the present invention is to provide an attachment between a first body and a second body of a marine structure, wherein a load transfer between the first and second bodies mainly occurs through joints which are located in areas which are easy to inspect.
A fourth object of the present invention is to provide an attachment between a first body and a second body of a marine structure, wherein the attachment may be executed on already existing connections between a first and a second body.
At least one of the objects above is achieved by an attachment according to claim 1.
Thus, the present invention relates to an attachment for attaching together a first body and a second body of a marine structure, which marine structure is adapted to be located at least partially immersed in water, wherein at least a portion of each one of the first and second bodies is adapted to, during use, be in contact with the water, wherein the attachment comprises at least a portion of the second body, wherein the second body comprises a wall which delimits the second body. The attachment further comprises at least a portion of the first body, wherein the first body is fixedly attached to, and extends from, the second body.
According to the present invention, the attachment further comprises a sealing member, attached to the wall and the first body, which sealing member extends from the wall to the first body such that an enclosed volume is formed between the sealing member, the first body and the second body.
By the above joint, the fixed connection between the first body and the second body will be separated from the water surrounding the marine structure. This means that the fixed connection will be located in an environment which is substantially less harsh as compared to the prior art. Further advantages of the sealing member, as compared to the prior art, are that this may be attached around already existing connections between a first and a second body of a marine structure, and that the first body does not necessarily need to be attached within the second body, although this is preferred.
According to a preferred embodiment of the invention, the sealing member is designed such that a displacement imparted on the first body relative to the second body results in a highest mechanical stress in the sealing member which is substantially lower than a highest mechanical stress in the first body, such that only a small part of the loads which are transferred between the first body and the second body is conducted through the sealing member.
Accordingly, the joints which are a part of the attachment which joints are adapted to be located in the water surrounding the marine structure, namely the joints attaching the sealing member to the wall and the first body, will only be exposed to a small portion of the loads transferred between the first and second body. This results in that these joints may be designed in a simple and cost efficient manner and nevertheless present strength characteristics, in particular as regards fatigue strength.
According to a further embodiment of the present invention, the highest mechanical stress in the sealing member is less than half, preferably less than a fourth, more preferably less than a tenth of the highest mechanical stress in the first body.
According to another embodiment of the present invention, the sealing member is fixedly attached to the wall and the first body by means of a welded joint.
According to a further embodiment of the present invention, the sealing member is fixedly attached to the wall along a first closed circuit around the first body, wherein the sealing member further is attached to the first body along a second closed circuit around the first body, wherein the ratio between the circumference of the first closed circuit and the second closed circuit is in the interval of 1.5-5, preferably within the interval of 2-4.
According to another embodiment of the present invention, the sealing member has a first extension from the wall in a direction which is substantially parallel to the extension direction of the first body, wherein the ratio between the length of the first extension of the sealing member and the circumference of the second circuit is within the interval of 0.1-1, preferably within the interval 0.2-0.6.
According to a further embodiment of the present invention, the sealing member comprises a first portion extending substantially parallel to the extension direction of the first body and a second portion extending substantially parallel to the extension direction of the wall.
According to another embodiment of the present invention, the sealing member further comprises a third portion extending substantially parallel to the first portion and a fourth portion, extending substantially parallel to the second portion.
According to a further embodiment of the present invention, the sealing member further comprises a fifth portion extending substantially parallel to the first portion and a sixth portion extending substantially parallel to the second portion, wherein the third and fifth portion are located at substantially the same distance from the wall.
According to another embodiment of the present invention, the second body is buoyant.
As used herein, the expression “buoyant” relates to a body the mass of which is lower than the mass of the volume the body would, when incorporated in the marine structure, displace if the body was to be immersed in water.
According to a further embodiment of the present invention, the wall comprises an opening which is located in the above-mentioned portion of the second body. The opening is located within the sealing member, in order to make inspection of the enclosed volume possible.
According to another embodiment of the present invention, the second body comprises an inner structure which is enclosed by the wall, whereby the first body is fixedly attached to the inner structure and extends out of the opening in the wall.
According to a further embodiment of the present invention, the inner structure comprises a bulkhead and the first body is fixedly attached to the bulkhead.
According to another embodiment of the present invention, the sealing member is constituted by a plate, preferably a plate of the same material as the second body and/or the first body.
According to a further embodiment of the present invention, the first body comprises an outer wall and the ratio between the thickness of the plate and the thickness of the outer wall is within the interval of 0.1-0.6, preferably within the interval of 0.2-0.4.
According to another embodiment of the present invention, the second body is a float of a ship, preferably of a semi-submersible vessel.
According to a further embodiment of the present invention, the first body is a bracing.
A second aspect of the invention relates to a semi-submersible vessel comprising a float, a deck structure and at least one column extending from the float to the deck structure, wherein the ship further comprises an attachment according to the present invention.
According to a preferred embodiment of the second aspect of the invention, the column comprises the attachment.
A third aspect of the invention relates to a method of attaching together a first body and a second body of a marine structure, wherein the second body is buoyant and comprises a wall which delimits the second body. In accordance with the third aspect of the invention, the method comprises the steps of: attaching the first body to the second body such that the first body protrudes from the second body; applying a sealing member extending between the wall and the first body, and attaching the sealing member to the wall and the first body.
According to a preferred embodiment of the third aspect of the invention, the second body comprises an inner structure which is enclosed by the wall, wherein the wall further comprises an opening. The first body is attached to the second body by attaching the first body to the inner structure such that the first body protrudes through the opening.
According to a further embodiment of the third aspect of the invention, the sealing member is attached to the wall and the first body by means of welding.
A fourth aspect of the present invention relates to a use of a sealing member for the method according to the third aspect of the present invention and/or for an attachment according to the first aspect of the present invention.
With reference to the figures,
The vessel 10 in
As realized from
The attachment 32 further comprises at least a portion of the first body 34, wherein the first body 34 is fixedly attached to, and extends from, the second body 36. In the embodiment illustrated in
In order to reduce the stress in the points of attachment between the sealing member 40 and the first 34 and second 36 body, respectively, the sealing member is preferably designed such that a displacement imparted on the first body 34 relative to the second body 36 results in a highest mechanical stress in the sealing member 40 which is substantially lower than a highest mechanical stress in the first body 34, such that only a small part of loads which are transferred between the first body 34 and the second body 36 is conducted through the sealing member 40.
Preferably, the highest mechanical stress in the sealing member 40 is less than half, preferably less than a fourth, more preferably less than a tenth of the highest mechanical stress in the first body 34. This is done in order to further reduce the load transferred through the sealing member 40. This share is continuously reduced, the smaller the highest mechanical stress in the sealing member 40 is as compared to the highest mechanical stress in the first body 34 and in some implementations of the sealing member 40, the highest mechanical stress in the sealing member may be as low as one hundredth of the highest mechanical stress in the first body 34, for a given displacement of the first body 34 relative to the second body.
The displacement of the first body 34 relative to the second body 36 may be of various kinds, for instance the first body may be bent, extended or compressed, depending for instance on the relative motions of the bodies with which the first body 34 is attached.
The difference in the highest mechanical stress between the sealing member 40 and the first body 34 may be achieved in a plurality of ways. Among others, the sealing member 40 may be manufactured from, or at least comprise, a material the modulus of elasticity of which is substantially lower than the material in the first body 34, for example the sealing member 40 may be made of rubber. Optionally, the sealing member 40 may be manufactured of a material having a modulus of elasticity which is approximately the same as the material of the first body 34, the sealing member 40 may even be made of the same material as the material of the first body 34, but the lower bending stiffness of the sealing member is instead obtained by the design of the sealing member 40.
It is further realized from
In the embodiment illustrated in
a illustrates a further embodiment of the present invention, wherein the sealing member 40 further comprises a third portion 54 extending substantially parallel to the first portion 48 and a fourth portion 56, extending substantially parallel to the second portion 50.
a further illustrates a preferred implementation of the joint between the first 34 and second 36 bodies, wherein the second body 36 comprises an inner structure 58 which is enclosed by the wall 38, wherein the first body 34 is fixedly attached to the inner structure 58 and extends out of the opening 52 in the wall 38. The inner structure 58 illustrated in
b illustrates a top view of the embodiment illustrated in
In order to obtain an attachment according to any one of the above embodiments of the attachment, a manufacturing method is preferably used which comprises the steps of: attaching the first body 34 to the second body 36 such that the first body 34 protrudes from the second body 36; applying a sealing member 40 extending between the wall 38 and the first body 34, and attaching the sealing member 40 to the wall 38 and the first body 34.
The first and second bodies 34, 36 are preferably attached to one another by means of welding. Also the sealing member 40 is attached to the wall 38 and the first body 34 by means of welding. In the cases wherein the second body 36 comprises an inner structure 58 and the wall 38 comprises an opening, the first body 34 is preferably attached to the second body 36 by attaching the first body 34 to the inner structure 58 such that the first body 34 protrudes through the opening 52.
It is realized that the present invention is not limited to the embodiments described above and illustrated in the drawings; rather a person skilled in the art will detect many alterations and modifications that can be performed within the frame of the scope of protection of the appended claims. For instance, even though the first bodies 34 in the above embodiments have been bracings, it is possible that the first body 34 may be a pontoon which is attached to a column. Furthermore, even though a semi-submersible ship is used as an example for the attachment of the invention, the marine structure in which the attachment is used could for example be a fixed installation, for instance of a jacket type, a ship or a spar buoy.
Various terms have been defined above. To the extent a term used in a claim is not defined above, it should be given the broadest definition persons in the pertinent art have given that term as reflected in at least one printed publication or issued patent. Furthermore, all patents, test procedures, and other documents cited in this application are fully incorporated by reference to the extent such disclosure is not inconsistent with this application and for all jurisdictions in which such incorporation is permitted.
While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.
| Number | Date | Country | Kind |
|---|---|---|---|
| 0701218 | May 2007 | SE | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 4084430 | Boyle et al. | Apr 1978 | A |
| 4143540 | Peterson et al. | Mar 1979 | A |
| 4771720 | Yuzuriha et al. | Sep 1988 | A |
| 4830540 | Abrams | May 1989 | A |
| 5941662 | Weaver | Aug 1999 | A |
| Number | Date | Country |
|---|---|---|
| 2004-100266 | Apr 2004 | JP |
| Number | Date | Country | |
|---|---|---|---|
| 20080292406 A1 | Nov 2008 | US |
