Patent Application
20170144731
The present invention is for a gravitation anchor, also known as a torpedo anchor, used for anchoring ships and offshore platforms. More specifically, the invention is for a gravitation anchor that has hydrodynamic stabilizers.
During the anchoring process of offshore oil platforms, a device known as a gravitation anchor or torpedo anchor is commonly used. Such a device is cast at a certain height from the seabed to gain speed, due to the gravitational pull during its descent to reach the seabed. Thus, the gravitation anchor hits the seabed at a high speed, causing it to have a higher load capacity and thus provide greater embedding into the seabed.
In addition, anchor line 2 is suspended by an intermediate point, with the aid of a second auxiliary casting line 3b, by an auxiliary vehicle 5. Anchor 1 is then positioned at a specific height and released for free fall until it reaches the seabed 6, being embedded.
The first auxiliary casting line 3a is then retracted until anchor line 2 reaches platform 4 and is connected thereto. Thus, platform 4 is anchored. Preferably, more than one anchor is used at different points of platform 4.
In order to increase the stability of the anchor during the fall, and consequently increase its final speed, it is desirable that the anchor stay as close as possible in a vertical direction. However, the geometric shape and the mass distribution of the stake are mainly designed for it to fulfill its geotechnical function, that is, after being embedded in seabed 6, which could adversely affect its stability during the fall to the seabed 6.
Consequently, stabilization of the anchor during the fall is often hindered, which can cause it to reach seabed 6 with high inclines, thus reducing its capacity and load, and causing embedding in seabed 6 to be more superficial. For this reason, often the anchor must be removed and reinstalled, or the use of a new anchor is required.
The prior art provides some solutions to increase the stability of gravitation anchors, as described by document EP1042162B1, which shows an anchor body, part of which has a polygonal or circular shape, a point and a rod projecting up, whereby the rod has a lower average density than the main body of the anchor. Thus, the anchor body is shaped such that the center of gravity is in the lower part thereof, and below the average distance of the sum of all fluid forces, which ensures directional stability.
Document EP1042162B1 also shows the use of fins to prevent rotation of the body during its descent. The attached fins shown in this document, however, may pose an obstacle to penetration of the anchor in the seabed, which could lead to the same problem described above, namely insufficient embedding of the anchor in the seabed.
Document U.S. Pat. No. 7,059,263B1, in turn, shows an anchor for anchoring structures into the seabed, comprising an elongated central body, which has a longitudinal axis through its center. A plurality of nose and tail plates are placed within channels, and hinged to the central body, so that the plates can swing inward or outward with respect to the central body, and then may be attached in the desired place. A means for attaching an anchor line 2 is also provided.
Also, as defined by document U.S. Pat. No. 7,059,263B1, the use of an arm in an approximately central region of the central anchor body is provided. This arm causes momentum in the anchor, causing the nose thereof to be kept pointed down (vertically). For this, the arm must be positioned and attached by pins before using the anchor.
The pin shown in document U.S. Pat. No. 7,059,263B1 should be installed only at the time that the anchor is used, so as to prevent damage from being caused to the equipment during transport. Thus, this solution requires rework on the anchor before it is cast, which may cause delays in the procedure. In addition, installation of the arm described is done manually, meaning that human error could cause a malfunction of the device.
Thus, it is clear that the prior art lacks a means of stabilizing a gravitation anchor that does not require rework prior to use, that does not negatively interfere with the anchor's load capacity and that does not require manual labor in order to function correctly.
The present invention is primarily intended to provide a gravitation anchor 1 comprising a means of stabilization that does not require pre-casting reworking and does not require manual labor in order to function correctly.
Thus, in order to achieve this objective, the present invention provides a gravitation anchor for offshore anchoring of ships and platforms, comprising a main body with a longitudinal axis of rotation, comprising a means of stabilization, whereby the means of stabilization comprises automatic activation.
The detailed description below makes reference to the accompanying figures and their respective reference numbers, representing embodiments of the present invention.
Preliminarily, it is emphasized that the following description will start with a preferred embodiment of the invention, applied to a gravitation anchor 1. However, as will be apparent to one skilled in the art, changes in the object described may be made within the scope of protection of the invention.
The present invention relates to the improvement of gravitation anchors as illustrated in
In addition, anchor line 2 is suspended by an intermediate point, with the aid of a second auxiliary casting line 3b, by an auxiliary vehicle 5. The anchor is then positioned at a specific height and released for free fall until it reaches the seabed 6, being embedded.
The first auxiliary casting line 3a is then retracted until anchor line 2 reaches platform 4 and is connected thereto. That is how the platform 4 is anchored. Preferably, more than one anchor 1 is used at different points.
The present invention provides a gravitation anchor comprising means of stabilization 14 to stabilize the downward movement of the anchor, increasing its speed and its load capacity, and enabling deeper embedding of anchor 1 when it hits the seabed 6.
Optionally, the anchor comprises a main body 10 with a longitudinal axis of revolution 11, whereby the main body 10 comprises fins 12 in at least one portion of its length.
Preferably, at least two fins 12 are adopted, preferably three fins 12, and more preferably four fins 12.
Optionally, the gravitation anchor 1 comprises a connector element 13 for connection to an anchor line 2 at its upper end.
Preferably, the means of stabilization 14 comprises at least one stabilizer 14, whereby each stabilizer 14 comprises an end pivotally attached 141 to the gravitation anchor 1 and a free end, so that when the means of stabilization 14 is in its retracted position, the free end is positioned closer to the main body 10 of the gravitation anchor 1. In turn, when the means of stabilization 14 is in its extended position, the free end is positioned away from the main body 10 of the gravitation anchor 1. Optionally, the stabilizer 14 comprises a rigid plate.
Optionally, each stabilizer 14 is attached in a coplanar fashion on a fin of the gravitation anchor 1. As shown, each fin comprises a stabilizer 14; however, other embodiments are provided. For example, the number of stabilizers 14 may be greater than the number of fins 12, whereby each fin comprises more than one stabilizer 14, or the number of stabilizers 14 is less than the number of fins 12.
As defined by the present invention, the means for stabilizing the gravitation anchor comprises a means of automatic activation 140, so that each means of stabilization 14 is automatically activated when the gravitation anchor 1 is positioned to be cast or when it is immersed in water and starts to move.
As can be best seen in
Optionally, so as to optimize the hydrodynamic forces mentioned, the protrusion 140 is positioned along at least one surface of the stabilizer 14, whereby when the stabilizer 14 is in its retracted position, illustrated in
Note that other embodiments of means of automatic activation 140 can, however, be adopted, staying within the scope of protection of the present invention. Merely as an example, alternatively, the means of automatic activation 140 may comprise a system of cables whereby the stabilizer 14 is activated and positioned in its position of use by gravitational force, when the gravitation anchor 1 is suspended. Other embodiments can also be adopted.
Optionally, the gravitation anchor 1 comprises a stroke limiting element 142 of the stabilizer 14, adapted to limit the rotation stroke of the stabilizer 14, defining the final position thereof.
As illustrated by the optional embodiment of
Optionally, the gravitation anchor 1 comprises a locking element (not shown), adapted for locking each stabilizer 14 in its final position, preventing it from going back to its retracted position, once it reaches its final position of use.
Optionally, in order to prevent the means of stabilization 14 from negatively interfering with the load capacity of the gravitation anchor 1 of the present invention, it can be designed to detach from the gravitation anchor 1 upon impact with the seabed 6. Such detachment may take place by a break in the means of stabilization 14 itself, or a break in the element responsible for attaching the means of stabilization 14 to the gravitation anchor 1.
Thus, the present invention provides a gravitation anchor 1 comprising means of stabilization 14, without requiring rework for positioning the means of stabilization 14. As such, it allows the anchor to reach a higher final speed, which increases its load capacity and thus provides deeper embedding thereof into the seabed.
In addition, when the embodiment in which the means of stabilization 14 is designed to detach from the gravitation anchor 1 at the time of impact against the seabed 6 is adopted, it minimizes the possible negative impact of the means of stabilization 14 on the embedding of the gravitation anchor 1, increasing the effect of its use.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2015 029208-2 | Nov 2015 | BR | national |
