VALVE STEM SEALING MEANS FOR PREVENTION OF FUGITIVE EMISSIONS

摘要

A valve stem sealing means comprising first (22) and second (40) seal assemblies, the first seal (22) assembly being proximate a valve plug and comprising an expandable ring (26) adapted to be expanded by pressure within the valve to effect a first seal around the valve stem (12), and the second seal assembly (40) being nearer a free end of the valve stem and comprising a second expandable ring (44) adapted to be expanded by contact with a selectively movable member (50) to effect a second seal around the stem (12).