Importance

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Abstract

Systems for lifting drilling risers that serve as thrust collars to retain buoyancy modules on the risers and also enable the risers to be lifted using lifting lugs that are attached to the thrust collars. In one embodiment, a lifting device uses two annular ribs at the edges of a cylindrical collar, wherein the ribs have substantially constant height, but varying thickness. The thickness of each rib is greater at the position of the lifting lug, and may also be greater at its base than that its top or outermost edge. The collar may be segmented, where the segments are bolted together to assemble the device around the riser. The segments may be pre-stressed to reduce stresses during lifting. The device may include an elastomeric layer on its inner surface.

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First Claim