Patent ID: 7819195

Claim:
A tensioner for applying tension to a subsea riser extending to a floating offshore structure, comprising: inner and outer barrels telescopingly engaging each other, one of the barrels adapted to be mounted to the offshore structure and the other to the riser to apply tension to the riser; a primary seal on an exterior wall surface of the inner barrel that slidingly and sealingly engages an inner wall of the outer barrel, defining a chamber within an interior of the inner barrel containing a gas under pressure, the primary seal having a high pressure side that is exposed to the gas under pressure within the chamber; an exterior reservoir containing a lubricant mounted external to the inner and outer barrels; a lubricant port extending through a sidewall of the inner barrel and having an outlet on the high pressure side of the primary seal; a lubricant conduit extending from the exterior reservoir into the chamber to the lubricant port for supplying lubricant to the primary seal; and a gas conduit extending from the chamber to the exterior reservoir, the gas conduit communicating the pressure of the gas in the chamber to the lubricant in the exterior reservoir.