Abstract: An improved gate valve having a body with a chamber and an inlet and an outlet extending therethrough into said chamber, a gate mounted for reciprocation in said chamber between open and closed positions, a pressure responsive actuator having a housing, a piston, a connection to the gate and an actuating stem extending from the housing, a supplemental actuator having a connection to the actuator housing, an operating stem connected to the actuating stem, the operating stem having a shoulder facing in the direction opposite to the direction of closing movement of the gate, roller levers pivotally mounted to be in engagement with the exterior of the operating stem and a spring urging the roller levers into tight engagement with the operating stem, the roller levers pivoting on engagement with the stem shoulder to exert a closing force on the stem.

Abstract: A carbon black reactor capable of producing carbon black of varying properties is disclosed comprising a longitudinally extending reactor tunnel having combustion, reaction, and quench zones in contiguous axial alignment. First and second venturi flow constrictions are provided in spaced relationship in the reaction zone of the reactor tunnel to create a pressure profile in the reaction zone. The pressure profile produces carbon blacks having certain physical properties. The second venturi constriction may be provided with means for varying the effective area of the second constriction for altering the pressure profile in the reactor tunnel to vary the properties of the produced carbon black. Further, carbon blacks of varying properties are produced for a given pressure profile by varying the point and direction of feedstock oil injection into the reaction zone.