Non-rising stem valve assembly and method of replacing a permanent seal

摘要

The non-rising stem valve assembly includes a valve body having an inlet and an outlet and a bonnet member securely attached to the valve body which defines a tubular passageway. A valve stem extends through this tubular passageway and has a lower valve portion axially displaceable relative thereto and positioned between the inlet and outlet. A retaining ring is provided for securing the valve stem against inward movement relative to the bonnet member and an inwardly projecting flange on the bonnet member is provided for securing the valve stem against outward movement relative to the bonnet member. A packing assembly is removably secured to the bonnet member for sealing the valve assembly. An axially displaceable seal is provided in a cavity formed between the flange and the upper surface of the lower valve portion which is axially movable within the cavity by the lower valve portion. This axially displaceable seal forms a temporary seal which may be selectively formed between the valve stem and the bonnet member for temporarily sealing the valve assembly and allowing the packing assembly to be replaced when necessary without decommissioning the valve assembly.