MXPA00006523A - Anchor - Google Patents

Abstract

Method for installing an anchor that is released in the sea, especially for installation of in soft seabed sediments. An anchor is released in free fall from an at rest position or nearly at rest position and with the longitudinal axis vertical from a position in the water, and that ensures directional stability and nonrotational acceleration during movement towards the seabed. The anchor body (14) has a main member or shank (22) with a regular cross section, especially circular or regular polygon form, with tip (23) and with upward projecting shank (25) with lower average density than the main anchor body has. The anchor body is shaped such that the center-of-gravity lies lower than the middle of the total anchor length and below the average distance to the sum of all the fluid forces which ensures directional stability and nonrotational acceleration during free fall and penetration into the seabed sediments.

Description

ANCHOR The invention comprises a method as described in the introduction of claim 1 of the patent, and an anchor as described in the introduction of claim 2, wherein an anchor element can be released freely to the seabed and penetrate the sediments. in order to serve as the anchor for a platform or a ship on the surface, as an example.

BACKGROUND In the Patent document. Norway No. 142,389, an anchor that can be propelled to the seabed by a ram or weight, which is fastened to the anchor, is described. The ram is operated by a lifting wire that runs to a bench on the surface, and allows the anchor to be driven to the seabed until the ram does not allow further penetration. This is not satisfactory for cases where a secure anchorage of a large structure or flotation system in loose sediments of the seabed is required. In the patent document of the United States No. 3,850,128, a method is described for driving an anchor towards the seabed through the use of vibrations. Here, a formed, cylindrical rod has four ears that form a cross that guides penetration. This anchor is dependent on external manipulation to be able to penetrate the seabed and therefore can not be dropped.

OBJECTIVE The main objective with the invention is to derive an anchor that through free fall can penetrate deep into the seabed such that the entire anchor is engulfed in relatively strong sediments. It is important that the anchor during the fall phase in the water stays exactly in the vertical position and does not rotate, but remains in a linear motion during the descent. In addition, it is an additional objective to create a connection for the anchor line that transfers the tension forces to the anchor such that a favorable load distribution develops.

INVENTION The invention is described in Claim 1. With this anchor it is possible to obtain penetration depths of 20-30 meters in soft sediments of the seabed with an anchor weight of 60-70 tons. The main effect is on the stable movement of the anchor during the fall phase without rotation, and the low center of gravity in relation to the fluid forces that ensures that the anchor body does not tilt in the water phase or when performing the Penetration resistance of the sediments, but continue in a straight line manner during the complete descent. The re-indications 2-10 describe especially favorable details of the invention.

EXAMPLE The invention is described in more detail below with reference to the drawings, wherein Figure 1 shows a schematic profile of an anchor according to the invention where the anchor body is suspended ready for installation, with a line of fall in line anchor combined; Figures 2-4 show perspective drawings of alternative anchor shapes; Figure 5 shows a side view of an anchor according to the invention, with a second integrated anchor line; Figure 6 shows a side view of the arrangement of the second anchor line in Figure 5, while Figure 7 shows a side view of an anchor according to the invention in an installed, fixed state. In this description, the term "anchor" means the anchor body, which is dropped from a height above the seabed that penetrates the sediments and the lines, chains or fixing arrangements that are used to connect the anchor element to a vessel of anchor. lifting during the installation and the structure to be anchored. In Figure 1 there is shown a ship 11 with a crank 12 having a first anchor line 13 and falling, combined which keeps an anchor body 14 suspended approximately 20 meters above the seabed 15. The crank 12 can be constructed from such a way that it can feed the anchor line by a motorized operation when the anchor is dropped, so that the anchor and its elements can freely fall to the seabed 15. In addition to the first anchor line 13, a second anchor line 16 can be found which is fixed to a fixing hook 17 at the front end of the body of anchor 14 and that is designed so that it lies freely in the sea. Figure 2 shows an example of an anchor body design 21. It has a main part or shaft 22 having a cylindrical shape with a bottom tip 23, which tapers 24 to a thinner part of the shaft 25. In the upper end, the shaft 25 tapers 26 towards a retaining ring 27 for the anchor line 13. The main shaft 22 has in this case three vertical ears 28. The main shaft 22 and the upper part 25 of the shaft can be formed from A type of material or put together by some practical method comprised of two parts and can also have the same cross section, since both the upper and lower shaft can be made of pipe filled with a suitable ballast material. During manufacture with a massive material, the center of gravity of the anchor shaft 22 will be in the same place as the geometrical center and will be in the lower part of the anchor body. During manufacture with composite products, for example, steel and concrete, and a shaft 25 cylindrically formed, the center of gravity can be moved further towards the anchor tip 23, so that it will be below the geometric center. With the anchor as a point of reference, water and soil will flow past the surface area of the anchor body, mainly parallel to the movement of the anchor. The anchor has a shape such that if the anchor begins to rotate around the horizontal plane, the viscous forces of the flowing fluid will increase on the outward tipping side and will force the anchor back to the vertical position. The low center of gravity helps maintain rotational stability during descent. This is especially true for the anchor shown in Figure 3. In Figure 3 an alternative design is shown where the basic shape is the same as in Figure 2, but the ears 28 'move further towards the top of the shaft 25A An alternative design may include ears on both the upper and lower part of the anchor shaft. In Figure 4, an additional design is shown, where on the tapered part of the shaft 24, between the ends of the shaft, lower 22"and upper 25", a joint 29 is inserted allowing a fold of approximately 90 ° between the two halves of the shaft. The reason for this attachment is described below with reference to Figure 7. In Figure 5 a design form of the invention is shown, where the anchor comprises an anchor body as shown in Figure 2. On the anchor line 13, which at the lower end comprises a chain 30, there is a distance on the retaining ring 27 equivalent to 4 to 6 times the total length of the anchor body 21, arranged a guide 31 for a second anchor line 32 running down to a fixing ring 33 on the bottom of the anchor. The details of this arrangement are shown in Figure 6. The guide 31 is formed such that a short section of the chain 34 is attached to the chain 30 via the sliding member 35. At each end of the guide rod 41, which is connects to the anchor line 32 and runs through the guide 31, there are stop tabs, the lower 36 and upper 37, respectively. Before the fall of the anchor, the second anchor line 32 is suspended via the lug 37 at the top of the slide member 35. In this position, both anchor lines 30 and 32 are suspended parallel and hang downward towards the body Anchor 21. During the fall phase, the cone-shaped driving element 40, attached to the anchor line 13, will brake the movement of the anchor lines 30 and 32, such that they remain taut against the anchor. and help extend the anchor on a straight route to the seabed. During the installation of the anchor, the anchor body is suspended in the water, for example, 20-30 meters above the seabed 15. During the fall phase, the anchor body will fall through the water and will penetrate into the soft sediments of the seabed. Due to the shape, according to the invention, the penetration will be sufficiently deep to allow the anchor to serve as an anchor point for the mooring of vessels, platforms, wave and tidal power stations and other similar structures. The aerodynamic shape combined with the low center of gravity ensures a straight line route to the seabed and together with the ears forbids the rotation of the anchor body. With this movement of straight lines in rotation of the anchor body, it is possible to achieve penetrations of 20-30 meters with an anchor body weight of 60-70 tons. In some cases, there may be sufficient resistance to friction from the ground against the surface area of the anchor body to allow pure vertical loading of the anchor. In this case, only one anchor line will be sufficient, connected to the upper part of the anchor body. The anchor body shown in Figure 3 will be "more suitable for this situation" Figure 7 shows how the anchor, according to the invention, can be used for mooring Here, an anchor body according to Figure 4 , shown in its original, penetrated position at 39A.After anchoring the anchor line 32 ', the first anchor line 13' will slide along the guide 31 (Figure 6) until the guide rod 41 stop by the tension tab, lower 36. Additional tensioning of the anchor line will cause the upper part of the shank 25"to rotate around the joint 29. Simultaneously, the anchor body will move from the position 39A to a position 39B somewhat raised and rotated.In this position, with a lateral tension on the anchor line, the ears of the anchor will receive a lateral resistance of the sediments of the seabed.The junction 29 stops the anchor body from being lifted during the tensioning of the line Anchor The anchor can also be used with an anchor line, which is preferably held or fixed to the lower half of the anchor body, such that it develops a lateral displacement when the anchor line is tightened. Alternatively, the anchor can be equipped with only one anchor line that is attached to the retaining ring 27 (Figure 2) on the upper part of the anchor body. This assumes that there is sufficient resistance to friction in the ground against the surface area of the anchor. The number of anchor ears can be between 2 and 8, but more likely 3 or 4. The anchor ears can be trapezoidal, curved or triangular with finished, straight edges. The design of the anchor shown in Figure 3 is then used. The cone-shaped driving element 40 is equipped with a clamping or fixing ring 42 at its upper end to suspend the anchor before the fall. An alternative design of the anchor body, the shaft is cylindrical along its length with a density that decreases towards the upper end, such that the center of gravity is in the lower half of the anchor body.

Claims (10)

PEIVTNniCATlONS

1. Method for installing an anchor that is released especially for installation in loose sediments of the seabed, characterized in that the anchor body is freely released from a resting position or near a rest position in the water, with the longitudinal axis vertical, which ensures directional stability and non-rotational acceleration towards the seabed.

2. Anchor to be lowered into the seabed, comprising an anchor body with an anchor line for anchoring a structure on the surface, such as a boat or floating platform, with a main shaft that is equipped with guiding elements such as two or more ears that extend radially outwards from the central part of the anchor and axially along the anchor body, with the front edges inclining or arching backwards and where the end of the main shaft extends upwards to a fastening ring for the anchor line, characterized in that the main shaft has a rectangular cross section, and that the surface area of the ears is a substantial portion of the total surface area of the anchor, to give sufficient frictional resistance to the ground during load, and that, the center of gravity of the anchor is located at or slightly below the center of flotation, but also below the center of the area total surface of the anchor to give directional stability and counteract rotation during free fall and penetration into the seabed. The anchor according to claim 2, characterized in that the anchor body with respect to the main anchor shaft has a shaft with less density, such as a hollow shaft or one that is filled with a less dense material than the main or lower part of the anchor. The anchor according to claim 3, characterized in that the ears are fastened to the main anchor shaft and / or to the upper part of the shaft. 5. The anchor according to claims 3-4, characterized in that the main anchor body of the main shaft are connected by a joint that allows bending up to 90 °, in order to limit vertical movement in the anchor body during tensioning of the anchor line. The anchor according to claims 2-5, characterized in that there is a fixing point for an anchor line, a distance from the fixing ring. The anchor according to claim 6, characterized in that the fixing point for the anchor line is placed between or under the ears. The anchor according to claims 6-7, characterized in that the second anchor line is placed through a guide on the first anchor line. The anchor according to claim 8, characterized in that the movement of the second anchor line through the guide has its movement limited by two stop tabs that are at a distance from each other on the guide rod in order to allow an some displacement between the two anchor lines during tensioning. The anchor according to claims 8-9, characterized in that the guide is constituted by a chain handle.