Reducing trenching at mooring lines
10894581 ยท 2021-01-19
Assignee
Inventors
Cpc classification
B63B2021/505
PERFORMING OPERATIONS; TRANSPORTING
E02D27/525
FIXED CONSTRUCTIONS
B63B21/50
PERFORMING OPERATIONS; TRANSPORTING
E21B41/08
FIXED CONSTRUCTIONS
B63B21/20
PERFORMING OPERATIONS; TRANSPORTING
International classification
B63B21/50
PERFORMING OPERATIONS; TRANSPORTING
E02D27/52
FIXED CONSTRUCTIONS
Abstract
The present techniques are directed to systems and a method for reducing trenching around piles. An exemplary method includes attaching a mooring line to one end of a padeye extender bar that is coupled by another end to a padeye on the pile. The pile is installed in a sediment layer. The padeye extender bar is deployed to hold an attachment point for the mooring line above the sedimenlt layer.
Claims
1. A system for reducing trenching, comprising: a pile configured to be disposed in a sediment layer and held in place by friction with the sediment layer; a padeye mounted to the pile; a padeye extender bar coupled to the padeye at one end, and attached to a mooring line at an opposite end, wherein the padeye extender bar is configured to support the mooring line above a surface of the sediment layer; and a stop mounted proximate to the padeye configured to hold the padeye extender bar at an operational position.
2. The system of claim 1, wherein the pile is a suction pile or a driven pile.
3. The system of claim 1, wherein the padeye comprises a locking mechanism configured to lock the padeye extender bar in an operational position.
4. The system of claim 3, wherein the locking mechanism comprises a ratchet mechanism.
5. The system of claim 1, comprising: a support bar padeye mounted proximate to an upper surface of the pile; and a support bar coupled to the support bar padeye, wherein the support bar is configured to deploy to the padeye extender bar and lock to the padeye extender bar.
6. The system of claim 5, wherein the support bar and the support bar padeye comprise deployment holes that are aligned when the support bar is in a vertical position and a deployment pin configured to be inserted through the aligned deployment holes to lock the support bar in the vertical position.
7. The system of claim 5, wherein the support bar and the padeye extender bar comprise locking holes configured to accept a locking pin inserted through both locking holes to lock the support bar to the padeye extender bar.
8. The system of claim 5, wherein the support bar is configured to be held in a vertical position by the mooring line during an installation.
9. The system of claim 5, wherein the support bar comprises a wheel configured to allow the mooring line to hold the support bar in contact with the padeye extender bar when tension is placed on the mooring line.
10. The system of claim 9, wherein the support bar and the wheel comprise: wheel locking holes that align when the support bar is deployed to the padeye extender bar; and a wheel locking pin configured to be inserted through the aligned wheel locking holes to hold the support bar in a locked position with the padeye extender bar.
11. A method for reducing trenching around a pile, comprising: attaching a mooring line to one end of a padeye extender bar that is coupled by another end to a padeye on the pile; installing the pile in a sediment layer; deploying the padeye extender bar to hold an attachment point for the mooring line above the sediment layer; deploying a support bar mounted to a support bar padeye disposed proximate to a top surface of the pile; and locking the support bar to the padeye extender bar.
12. The method of claim 11, comprising locking the support bar to the padeye extender bar by inserting a locking pin through aligned locking holes on the support bar and the padeye extender bar after deployment.
13. The method of claim 11, comprising: threading the mooring line over a wheel disposed on the support bar at an opposite end from the padeye mounting; and using the mooring line to deploy the padeye extender bar and the support bar.
14. The method of claim 13, comprising inserting a wheel locking pin through aligned wheel locking holes in the wheel and the support bar after deployment.
15. The method of claim 11, comprising: attaching the mooring line to a support bar at an end opposite to a coupling to a support bar padeye; installing the pile in the sediment layer; and releasing the mooring line from the support bar to deploy the support bar.
16. The method of claim 15, comprising: deploying the support bar and the padeye extender bar; and inserting a locking pin through holes in the support bar and padeye extender bar that align when the support bar and padeye extender bar are deployed.
17. The method of claim 11, comprising: placing a support bar in a vertical position before deployment to align deployment holes on a support bar padeye and support bar; and inserting a deployment pin through the aligned deployment holes to hold the support bar in the vertical position during deployment.
18. The method of claim 11, comprising locking the padeye extender bar in a deployed position using a ratchet mechanism.
Description
DESCRIPTION OF THE DRAWINGS
(1) The advantages of the present disclosure are better understood by referring to the following detailed description and the attached drawings.
(2)
(3)
(4)
(5)
(6)
(7)
(8)
(9)
(10)
(11)
(12)
(13)
(14)
DETAILED DESCRIPTION
(15) In the following detailed description section, the specific embodiments of the present disclosure are described in connection with one or more examples. However, to the extent that the following description is specific to a particular embodiment or a particular use of the present disclosure, this is intended to be for exemplary purposes only and simply provides a description of the one or more embodiments. Accordingly, the disclosure is not limited to the specific examples described below, but rather, it includes all alternatives, modifications, and equivalents falling within the true spirit and scope of the appended claims.
(16) Various terms as used herein are defined below. To the extent a term used in a claim is not defined below, 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.
(17) Certain terms are used throughout the following description and claims to refer to particular features or components. As one skilled in the art would appreciate, different persons may refer to the same feature or component by different names. This document does not intend to distinguish between components or features that differ in name only. The drawing figures are not necessarily to scale. Certain features and components herein may be shown exaggerated in scale or in schematic form and some details of conventional elements may not be shown in the interest of clarity and conciseness. When referring to the figures described herein, the same reference numerals may be referenced in multiple figures for the sake of simplicity. In the following description and in the claims, the terms including and comprising are used in an open-ended fashion, and thus, should be interpreted to mean including, but not limited to.
(18) The term substantially, substantially the same or substantially equal as used herein unless indicated otherwise means to include variations of a given parameter or condition that one skilled in the pertinent art would understand is within a small degree variation, for example within acceptable manufacturing tolerances.
(19) As used herein, installation or installed is used to refer to inserting a pile into a sediment layer, for example, using a pile driver or a pump to remove water from the piling. The term deployment or deployed is used to refer to the final steps to set up the piling after installation, such as moving a padeye extender bar into a final position and locking it into place.
(20) As used herein, proximate indicates that an object or effect is near or on another object or effect. For example, a first object that is proximate to a second object, or a location on a second object, is placed near or in contact with the second object or location.
(21) As described herein, a pile provides an attachment point for a mooring line. The pile is installed into a sediment layer and held in place by friction. In some examples, the pile is a suction pile that is pulled into place in the sediment layer as water is removed from the inside of the pile. In other examples, the pile is a driven pile, forced into the sediment layer, for example, by a repetitive hammer force. The pile may be formed from any suitable material, such as concrete or metal. For offshore applications, the materials may include corrosion resistant steel, structural steel, cast-iron, or cast concrete, among others.
(22) The techniques described above may not control scouring from the motion of a mooring line, termed trenching herein. Thus, there remains a need to provide trenching protection to a pile while providing maximum surface area contact between the pile and surrounding soil. Trenching may cause seafloor degradation and erosion around a pile. In some instances, the trenching may be significant, reaching the depth of the padeye that attaches the mooring line to the pile, for example, about two thirds down the side of the pile. Accordingly, the trench formation may impact the functional performance of the pile. As a result, the loads the pile can support may be reduced or, in extreme examples, the pile may become dislodged from the seafloor. This may jeopardize the station-keeping capability of the pile foundation and mooring system.
(23) The present disclosure provide a method and systems for reducing trenching. In one example, a system includes a pile with a padeye extender bar attached to the padeye on the side of the pile, in place of the mooring line. The padeye extender bar may then extend above a sediment layer before attaching to the mooring line. In some examples, the padeye extender bar is locked into place, preventing the padeye extender bar from creating a trench as the mooring line moves.
(24)
(25) The pile 104 is installed into sediment layer 112, such as a seafloor, and the padeye extender bar 106 is deployed. In concert with other piles 114, which may use the same or different technologies, the pile 104 forms a pile foundation that is attached to the offshore structure 102 through mooring lines 110. The pile foundation assists in station-keeping for the offshore structure 102, controlling its movement from wind and water forces. In various examples, the offshore structure 102 is a floating structure as depicted in
(26) As described herein, in an example, the pile 104 is an open-ended structure, or suction pile, that is installed by removing water, or allowing the water to exit, from a port 116. The removal of water from the pile 104, in turn, facilitates the insertion of the pile 104 into the sediment layer 112. A suction pile is often used in deeper waters due to its relative ease of installation and the types of sediment present.
(27) In some examples, the pile 104 is installed into the seafloor, for example, by driving the pile 104 into the sediment layer 112. A driven pile may be adapted to variable site conditions to achieve uniform load carrying capacity with reliability. The use of a driven pile may be advantageous over a suction pile, whose installation may be more sensitive due to various soil types and layering. Additionally, due to the small size of a driven pile relative to a suction pile, a driven pile may be well suited in water depths where existing driving equipment may be used. In either example, the use of the padeye extender bar 106 to bring the attachment point for the mooring line 110 above the surface of the sediment layer 112 may protect the pile 104 from trenching.
(28) As shown in
(29) The pile 104 also may have a maximum axial dimension, L.sub.p 120. The L.sub.p 120 may be any suitable dimension that is sufficient to accommodate the anticipated loads on the pile. For example, the ratio of L.sub.p 120 to D.sub.p 118 may be at least about 2, at least about 3.5, at least about 4, or at least about 4.5, for example, in the range of from 2 to 10, or from 3.5 to 8.5. For stiff clays, the ratio may be in the range of from about 3.5 to 4. For intermediate strength clays and other non-clay soils, the ratio may be in the range of from about 4.5 to 7. For soft clays, the ratio may be in the range of from about 7 to 8.5. In some examples, at least about 80% of L.sub.p 120 is disposed beneath the surface of the sediment layer 112, for example at least 90%, at least 95%, at least 99% or 100%.
(30) The pile may have any suitable cross-sectional geometry, for example circular, oval, elliptical, or polygonal such as triangular, square, rectangular, pentagonal, hexagonal, etc. In one or more examples, one or more external surfaces of the pile may have one or more surface features to enhance frictional contact with the soil sediment.
(31)
(32) For installation, the open end 202 of the pile 104 is positioned on the surface of the sediment layer 112. A lowering mechanism (not shown) is used to position the pile 104 on the sediment layer 112 and is released and withdrawn. The pile 104 may initially penetrate the sediment layer 112 level due to the weight of the pile, for example, as shown in
(33) As shown in
(34) As shown in
(35) As shown in
(36) Reinforcement may be provided to hold the padeye extender bar 106 in place, lowering stress on the padeye 108. This is discussed further with respect to
(37)
(38) In
(39) As shown in
(40) As shown in
(41)
(42) As shown in
(43) As shown in
(44)
(45) In some examples, the stop 502 is configured to slide into an opening on the padeye extender bar 106. A locking pin may then be inserted into aligned holes on the stop 502 and the padeye extender bar 106 to lock the padeye extender bar 106 in place. Other mechanisms, such as described with respect to
(46)
(47)
(48) In this example, the support bar padeye 304 and the support bar 302 have deployment holes 706 that are aligned when the support bar 302 is in a vertical position. A deployment pin 708 is inserted 710 to hold the support bar 302 in a vertical position during installation. After installation, the deployment pin 708 is removed 710 from the aligned deployment holes 706 to allow the support bar 302 to be deployed into the operational position. The removal of the deployment pin 708 may be performed by a remotely operated vehicle (ROV), or by other techniques, such as divers.
(49)
(50)
(51)
(52) In this example, the mooring line 110 is joined to an end of the support bar 302, for example, by having a portion, or a link, of the mooring line 110 held in a forked region 902 of the support bar 302 by a chain pin 904 that is inserted 906 into a hole 908 at an outside end of the forked region 902. After installation, the chain pin 904 may be removed 906 from the hole 908, allowing the mooring line 110 to be removed from the forked region 902 for deployment. This allows the support bar 302 to come into contact with the padeye extender bar 106, as discussed further with respect to
(53)
(54)
(55) In this example, the wheel 1102 is mounted to the support bar 302 with an axle pin 1104. The wheel 1102 includes notches 1106 configured to engage with the mooring line 110, for example, if the mooring line 110 is an anchor chain. The wheel 1102 and the support bar 302 may include wheel locking holes 1108 configured to align, for example, when the support bar 302 is in a vertical position, a deployed position, or both. A wheel locking pin 1110 may be inserted 1112 into the aligned wheel locking holes 1108 to prevent the wheel from turning, for example, to lock the mooring line 110 in place and hold the support bar 302 in the vertical position during installation. Once the pile 104 (
(56)
(57)
(58) At block 1304, the pile may be installed in a sediment layer. In one example, the pile is a suction pile and is installed in the sediment layer by removing water from inside the suction pile to force an open end of the suction pile into the sediment layer. In another example, the pile is a driven pile that is installed by being forced into the sediment layer.
(59) At block 1306, the padeye extender bar is deployed to hold the attachment point of the mooring line above the sediment layer. This helps to prevent movement of the mooring line, for example, from a moored structure, from generating a trench proximate to the pile.
(60) The method 1300 is not limited to the actions in the blocks described above. For example, the padeye extender bar may be locked in place using a mechanism to prevent motion of the mooring line from moving the padeye extender bar. Further, a support bar may be attached to the pile, and deployed to contact the padeye extender bar. This may provide reinforcement to the mooring line attachment point and locking mechanism.
(61) While the present disclosure may be susceptible to various modifications and alternative forms, the one or more examples discussed above have been shown only by way of example. However, it should again be understood that the present disclosure is not intended to be limited to the particular examples disclosed herein. Indeed, the present disclosure includes all alternatives, modifications, and equivalents falling within the true spirit and scope of the appended claims.