Abstract: In a steam generating plant having a main steam line and a pivotally actuated valve movable between open and closed positions for controlling the flow of steam in the main steam line, a system for operating the main steam line valve comprising a spring assembly for biasing the valve pivotally into the closed position, fluid actuated means for urging the valve pivotally into the open position against the biasing action of the spring assembly and means for supplying fluid under pressure for the fluid actuated means, the fluid supply means including a pump operatively connected to the fluid actuated means and at least one exhaust valve operatively connected to the pressure end of the pump.