High pressure gate valve with preloaded, stacked, solid lubricated stem seals

摘要

A high pressure gate valve having at least one pressure actuated seal means between the bonnet part of the valve body and the valve actuating stem and between the chamber part of the valve body and the valve actuating stem is disclosed. Each seal means includes at least one seal assembly. Each seal assembly includes two sets of plural, e.g., four, metal rings with an elevated temperature resistant and chemical resistant ring of solid lubricant, e.g. , tetrafluoroethylene or graphite, separating the metal rings. Each metal ring is softer than the stem and is of rectangular cross-section. The seal assembly is actuated by pressure on larger follower metal rings. When multiple seal means are involved, another metal follower ring larger than the set of metal rings of the seal means also separates the two sets of seal assemblies. The seal means may also include a biasing spring. Each seal means is disposed in an annular pocket or stuffing box in the adjacent part of the valve body extending around the stem. Each stuffing box is closed by an annular packing gland screwed into the stuffing box far enough to flatten out the lubricant sufficiently for the inner and outer peripheries of the inner and outer metal rings respectively of the set of metal rings to engage the stem and stuffing box walls respectively and seal in the lubricant ring. The valve stem sealing arrangement may also be employed for packing off lock screws and in other situations wherein relatively movable parts are to be sealed both during and after relative motion.