| 摘要 |
<p>A valve stem packing assembly comprises a stacked assembly of V-ring seal elements, special back-up energizing rings interspersed between the seal elements and a spring-energized lip seal ring that is retained in the functional position by an adapter ring having a generally T-shaped cross-sectional configuration. As the assembly is installed in a valve stem packing chamber with the T-adapter ring at one end of the assembly and a back-up ring for the V-ring seal elements at the other end, the lip seal ring and the V-ring seal elements are radially compressed to establish an initial seal between the stem and the chamber wall. When the assembly is subjected to interval valve pressure the V-ring seal elements and the lip seal ring are additionally compressed and deformed to fill annular spaces that may still exist between the seal elements, their back-up/energizing rings and the lip seal ring, thereby establishing an essentially void-free dynamic packing between the stem and the chamber wall that is capable of withstanding many hundreds of gate valve stroke cycles (valve open to closed to open constituting one cycle) at unusually high pressures of fifteen thousand pounds per square inch and above, and unusually high temperatures of two-hundred and fifty degrees Farenheit and above. Furthermore, a stem packing assembly according to the present invention is extrusion-free, insensitive to fluctuations in pressure and/or temperature, and exceedingly resistant to chemical attack.</p> |
