Method and apparatus for protecting offshore structures against forces from moving ice sheets
First Claim
1. A method for protecting a marine structure fixed in a body of water from forces exerted by sheet ice moving across the water surface comprising the steps of:
- placing adjacent the marine structure a shield surface which slopes away from the structure in a direction opposite to the direction of ice movement from the structure proceeding from an upper portion above the water surface to a lower portion disposed below the water surface,allowing a portion of the sheet ice to move substantially into contact with the shield surface so that a submerged portion of the shield surface is disposed below the ice,raising the shield surface to an elevated position thereof to cause the surface to lift the ice and to break pieces therefrom, andmoving the shield surface in the elevated position thereof to a position thereof downstream from the marine structure relative to the direction of ice movement.
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Accused Products
Abstract
A stationary offshore platform is protected against damage from moving ice sheets by a conical shield surrounding the platform support structure and having means, such as a pneumatic biasing system, for raising or lowering the shield along the platform support. A system of mooring lines, thrustors, or the like is used to rotate the shield about the platform support. After an advancing ice sheet contacts the narrower upper portion of the shield, the shield is raised so that a wider lower portion of the shield can exert an upward force on the ice sheet to break the ice into pieces. The shield is rotated, while in its elevated position, to carry the broken ice with it to a location downstream from the advancing ice sheet. The shield is then lowered to dump back into the ocean the ice pieces broken by the upstroke of the shield. Means are provided for heating the exterior surfaces of the shield to melt ice pieces sticking to it.
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Citations
46 Claims
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1. A method for protecting a marine structure fixed in a body of water from forces exerted by sheet ice moving across the water surface comprising the steps of:
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placing adjacent the marine structure a shield surface which slopes away from the structure in a direction opposite to the direction of ice movement from the structure proceeding from an upper portion above the water surface to a lower portion disposed below the water surface, allowing a portion of the sheet ice to move substantially into contact with the shield surface so that a submerged portion of the shield surface is disposed below the ice, raising the shield surface to an elevated position thereof to cause the surface to lift the ice and to break pieces therefrom, and moving the shield surface in the elevated position thereof to a position thereof downstream from the marine structure relative to the direction of ice movement. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. Apparatus for protecting a marine structure fixed in a body of water and extending above the surface thereof from forces exerted by a moving ice sheet at the water surface comprising:
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a shield adapted to be positioned adjacent the marine structure and having a sloping working surface, the shield being vertically movable between an elevated position and a lowered position in which the working surface extends from an upper portion thereof above the water surface downwardly away from the marine structure to a lower portion thereof disposed below the water surface, the shield also being movable laterally between an upstream position and a downstream position of the working surface relative to the marine structure in terms of the direction of ice movement, means for raising the shield from its lowered to its elevated position in the upstream position of the shield, the shield during such raising being adapted to engage and to lift and to break ice disposed above the working surface, and means connectible to the shield operable for moving the shield in the elevated position thereof from its upstream position to its downstream position. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37)
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38. In combination with a marine structure fixed in a body of water and having an upright support extending through the water surface, apparatus for reducing forces exerted on the support by a moving ice sheet at the water surface, the apparatus comprising:
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a vertically movably shield surrounding the support, the shield having a sloping working surface extending, in a lowered position thereof, from above the water surface downwardly away from the marine support, at least in a direction opposite to which the ice is moving toward the support, to a lower position disposed below the water surface; means for normally positioning the shield in a position thereof facing upstream, in terms of ice movement, so the working surface lower portion projects below the moving ice sheet; a floodable chamber in the shield and means for removing water from the chamber to increase the buoyancy of the shield for raising the shield to an elevated position in which the lower portion of the shield working surface is disposed below the water surface, the shield during raising thereof being adapted to engage and to lift and to break ice disposed above the working surface, the lower portion of the shield surface being configured to support broken ice pieces adhering to the shield surface; means for rotating the shield about the support, while the shield is in the elevated position, to move the working surface of the shield downstream, in terms of direction of ice movement, from the marine structure support so that broken ice pieces can be carried on the shield surface to the downstream position; and means for flooding the chamber to lower the shield from its elevated position to discharge the broken ice into the water at said downstream position. - View Dependent Claims (39, 40, 41, 42)
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43. A marine structure located in a fixed position in a body of water having a moving ice sheet at the surface of the water, the marine structure comprising:
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a platform located above the surface of the water; an upright support member extending through the water surface and supporting the platform above the water; a vertically movable shield adapted to be positioned adjacent the marine support and having a sloping working surface extending, in a lowered position thereof, from above the water surface downwardly away from the support, at least in a direction opposite to which ice is movable toward the support, to a lowered position disposed below the water surface; means for raising the shield to an elevated position in which the lower portion of the shield working surface is disposed below the water surface, the shield during raising thereof being adapted to engage and to lift and to break ice disposed above the working surface, the working surface being configured to support pieces of ice broken during raising of the shield; means connected to the shield and operable for moving the shield in the elevated position thereof to a position of the working surface downstream, in terms of the direction of ice movement, from the marine structure; and means for lowering the shield to a lowered position in which the working surface is submerged in the water to facilitate discharging the broken ice pieces from the shield surface in the downstream position. - View Dependent Claims (44, 45, 46)
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Specification