A valve device for influencing an overpressurized flow of media comprises a control valve for controlling the flow of media, and a closing valve which is either totally open or totally closed to stop the flow. The valves are arranged in a common valve housing and can seal independently of each other against a common valve seat. The valve seat presents an outlet side which forms the outlet channel of the valve device. The valve device can be made compact, and the number of necessary redirections of the flow of media is minimized.

A valve seat and a valve assembly incorporating such valve seat form tight dual seals with glass lined nozzle of a reagent or reaction vessel. This reduces or eliminates cavities and crevices between the value seat and the nozzle where residues or contaminants can accumulate. Additionally, the present valve assembly comprises flush ports to permit the valve seat and the valve to be cleaned-in-place. This eliminates the need to disassemble the valve seat and/or the valve to remove the contaminants, thereby minimizing process "down time."

There is disclosed two embodiments of a gate valve having a pair of parallel-sided gates for opening and closing a flowway through the valve body upon reciprocation within a gate cavity intersecting the flowway intermediate its ends. The gates are connected to an actuator stem by a lost motion connection which causes one to be moved from closed toward open position prior to the other, and the one gate has a passageway therein for moving into a position to connect the cavity with the flowway prior to movement of the gates together toward open position.

A process control valve is disclosed including a valve body assembly which includes process fluid input and output ports, an actuation pressure port and a vent port. The valve body includes a cylinder with two pistons longitudinally spaced and separated by a biasing means such as a spring. The pistons each have a rod which acts as a seal for a process fluid port when normally biased by the biasing spring. The actuation port of the body assembly communicates with the opposite faces of the pistons from the bias spring to open the process fluid input and output ports by overcoming the biasing port closing force. The two pistons include rods having process fluid passageways therethrough. The pistons also include a valve poppet & seat combination which is closed whenever actuation force is applied to the process control valve sealing the process fluid path from the vent port. A reversible input/output valve is disclosed as well as a modular assembly of interchangeable valves is disclosed.

A valve which is fitted with two sealing places which are disposed in series and in the closed position of the valve prevent the overflow of fluid from one valve casing part into another, with the leakage cavity disposed between the sealing places and connected to the outside of the valve through the valve casing, has a closed position in which the connection of the leakage cavity with an inside space of the valve casing parts is sealed by a closing member cooperating with the two sealing places. The connection between the leakage cavity and the inside space can be controlled also in positions other than the closed position of the valve by a locking piece which substitutes the closing member regarding its interaction with the leakage cavity. This locking piece, which is movable relative to the closing member in the direction of the degree of freedom of motion of the closing member, controls the connection between the leakage cavity and the inside space.