Abstract: A stiffener assembly for a riser extending from a subsea well component through an opening in a floating platform has at least two partially cylindrical inner sleeve segments that mount around the riser. Inner sleeve grooves are on an outer surface of each of the inner sleeve segments, defining inner sleeve ribs. The inner sleeve segments have abutting side edges when mounted around the riser. At least two partially cylindrical outer sleeve segments are mounted around the inner sleeve segments. The outer sleeve segments have abutting side edges when mounted around the inner sleeve segments. Outer sleeve grooves on an inner surface of each of the outer sleeve segments define outer sleeve ribs that fit within the inner sleeve grooves between the inner sleeve ribs. The abutting side edges of the outer sleeve segments are circumferentially offset from the abutting side edges of the inner sleeve segments.

Abstract: A riser tensioner for maintaining a tensile force on a riser extending through an opening in a deck of a floating platform includes a frame assembly that may be quickly bolted together in the field. The frame assembly includes a plurality of tensioner legs that may be installed on an un-level deck yet still provide a level support of the riser. Lower leg mounting assemblies include a slip ring for mounting directly to the deck and a deck mounting member received in the slip ring at a variable angle and having an upwardly extending shaft passing into a bore in a lower end of a tensioner leg.

Abstract: A riser tensioner assembly for supporting risers on an offshore drilling platform includes a frame assembly and a plurality of riser centralizers circumferentially spaced about the frame assembly. The riser centralizers each include a clevis supporting roller for bearing on a riser to limit lateral movement of the riser with respect to the frame assembly. The clevis includes an elongated channel along which the roller is movable to accommodate angular movement of the riser with respect to the frame assembly.

Abstract: A riser tensioner system maintains a tensile force in a riser having an axis and extending from a subsea wellhead assembly through an opening in a floating platform deck. The tensioner includes a plurality of tensioner legs having lower ends mounted to the deck, and upper ends having slots formed therein to receive leg attachment plates having an opening therein through which a tubular support ring passes. A plurality of cylinders extend between the tubular support ring and a tensioner ring and couple to the support ring with cylinder attachment plates through which the tubular support ring passes. An upper end of each cylinder pivots about the mounting point, and a lower end of each cylinder adjustably mounts to the tensioner ring.