Abstract: A double-block and vent valve having an improved actuator mechanism to allow one part of a composite valve member to be lifted separately from another. The actuator mechanism overlies the valve housing and is connected to the two valve member parts via coaxial rod and tube members. Hold-down cams normally block the upward movement of the tube member to positively lock the upper valve member part against its seat when it is desired to lift only the lower valve member part. A pair of pivotal cams are spring-biased to this blocking position where they bear against lug means carried by the tube member. A small, horizontal, fluid-actuated cylinder pivots the hold-down cams to a non-interfering position whenever it is desired to lift only the upper valve member part or to lift the composite valve member.

Abstract: A valve has an upper region connectable to a first piping system, a lower region connectable to a second piping system and an intermediate passageway therebetween which is opened and closed by a valve member which is reciprocated by an overhead actuator. The valve member has first and second members which are slidable relative to one another. In the closed position, the first and second valve members seal with spaced apart seats and define therebetween an intermediate chamber including the surface of the interior passageway between the seals. A lower valve member extending exterior of the lower region has cleaning solution inlet and outlet passageways which communicate with the intermediate chamber whereby the surfaces of the intermediate chamber may be cleaned and whereby any leakage around either of the seals is drained externally.