CONJUNTO DE VALVULAS DE HASTE NAO ASCENDENTE E PROCESSO DE SUBSTITUICAO DE UM SELO PERMANENTE

摘要

A non-rising stem valve assembly (2) is disclosed including a valve body (4) having an inlet (3) and an outlet (5) and is capable of accommodating a non-rising stem valve (14). The non-rising stem valve includes a bonnet member (8) securely attached to the valve body (4) and forms a tubular passageway. A valve stem (14) extends through this tubular passageway and has a lower valve portion (20) axially displacable relative thereto, with the lower valve portion (20) being positioned between the inlet (3) and outlet (5). A retaining ring (16) is provided for securing the valve stem (14) against inward movement relative to the bonnet member (8) 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 nut (24) is removably secured to the bonnet member for sealing the valve assembly. The packing nut has an interior surface and an exterior surface with a first O-ring seal (26) being provided on the interior surface and a second O-ring seal (28) being provided on the exterior surface. A third axially displacable seal (36) is provided which rests on an upper surface of the lower valve portion (20) and is axially movable with the lower valve portion. The first and second O-ring seals form permanent seals and seal the valve assembly during normal use, while the third 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 permanent seals to be replaced when necessary without decommissioning the valve assembly. A method of replacing the permanent seals is also disclosed.