Valve stem sealing means for prevention of fugitive emissions

摘要

A valve stem sealing means comprising first and second seal assemblies, the first seal assembly being proximate a valve plug and comprising an expandable ring adapted to be expanded by pressure within the valve to effect a first seal around the valve stem, and the second seal assembly being nearer a free end of the valve stem and comprising a second expandable ring adapted to be expanded by contact with a selectively movable member to effect a second seal around the stem.