Fairing for marine drilling risers

Abstract

A fairing includes two half-shells of fiber reinforced plastic or fiberglass. The shell halves are shaped to close around the buoyancy modules (e.g., cylindrical syntactic foam buoyancy modules) commonly used on deep-water risers, but with an extended trailing edge. The fairing includes a tail that streamlines the riser and reduces/prevents formation of the vortex, which causes drag and vibration. Hinges at the tail join the halves and enable them to be opened for assembly around the riser pipe as it is being run into the water. The fairing may be fastened together by bolted stainless steel tensioners that tightly draw together straps of high strength aramid fiber, such as KEVLAR®. The fairing is positioned on the riser such that the fairing is free to swivel and rotate into the current, while integral buoyancy blocks support the tail. To prevent movement up or down the riser string, the fairing is held in place by a channel clamp gripping the outside diameter of the syntactic foam buoyancy module.

1 . A fairing for use on with a riser, comprising:
 an adjustable channel clamp that includes first and second clamp halves that are longitudinally and rotatably secured together around the riser with a first synthetic fiber strap;   a fairing that includes first and second fairing halves secured around the riser, where the first and second halves form a channel around an interior periphery of the first and second halves such that the adjustable channel clamps rides within the channel; and   a second synthetic fiber strap that co-axially encircles the fairing to hold the first and second fairing halves in a closed position.   
     
     
         2 . The fairing of  claim 1 , where the each of the first and second fairing halves includes a semi-cylindrical component that partially surrounds the riser and a tail that tapers downward to a point at a tail end of the fairing.