Importance

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Abstract

A tensioning ring and riser assembly for use in oil well platform riser tensioning apparatus. The cylindrical riser has male threads formed on the exterior surface. The annular tensioning ring has female threads formed on the interior adapted to loosely thread onto the male threads. The tensioning ring is adapted to be tensioned in a first direction relative to the riser. The female threads have a leading face lying at a shallow angle to the assembly centerline in the first direction and a trailing face lying approximately perpendicular to the assembly centerline. The male threads have a complementary configuration. When the tensioning ring is tensioned in the first direction, the shallow angled faces are brought into tangential pressure contact so that hoop stress is uniformly distributed and minimized in both riser and tensioning ring with the shear load between them distributed over the wall thickness of both parts. When the tensioning force is released, the only contact is at the faces that lie approximately perpendicular to the centerline. This contact is under little pressure and has a minimal contacting area, allowing easy rotation of the tensioning ring relative to thread the tensioning ring up or down the riser. A rounded root between the threads on each part allows clearance for thread tips as the threads move between the tensioned and untensioned positions.

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First Claim