| 摘要 |
A retrofit valve stem seal assembly (100), which can be retrofitted to existing quarter-turn valves already in service, is provided. The retrofit valve stem seal assembly is added to the valve stem (2) by inserting a valve stem adaptor (3) onto the valve stem and firmly attaching the adaptor to the valve stem. The inner surface fo the valve stem adaptor fits on the valve stem. To prevent leaks between the valve stem adaptor and the valve stem "O" rings (5) are installed in the valve stem adaptor to bear against the valve stem. A rotatable valve stem adaptor includes a sliding tractrix surface (7) for sliding contact with a stem packing (6). The stem packing includes a complementary tractrix surface (8) for contacting the sliding tractrix surface on the valve stem. Wear between the contacting surfaces is uniform at all points of contact between the sliding tractrix surface and the complementary tractrix surface, creating and maintaining a dynamic seal.
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