Combined valve

A combined steam valve in which a stop valve for blocking the flow of heated steam into a steam turbine and a control valve for controlling the flow rate of the heated steam supplied to the turbine are arranged in the same valve casing,

• wherein said stop valve is arranged upstream of the control valve with respect to the flow of the heated steam, a valve body constituting said control valve is provided with a bypass valve and a steam passageway for introducing the heated steam, which has passed through said bypass valve, into the steam turbine, and
• wherein a valve body of said bypass valve is attached to a valve stem for opening and closing said bypass valve relative to a bypass steam passageway formed through said control valve, and, on the valve body of said bypass valve and the valve body of said control valve, there are provided portions, respectively, which engage with each other to open said control valve when said valve stem is displaced in the direction for opening said bypass valve beyond a fully open position thereof, the control and bypass valves being operable for enabling the flow rate of the heated steam flowing through said steam passageway into the steam turbine to be proportional to the extent to which said bypass valve is opened, up to said fully open position, and thereafter in proportion to the extent that the control valve is opened, the bypass valve providing a fine control of the steam flow rate commensurate with the rate of increase of speed of the steam turbine during start-up, and the control valve providing a greater range of control upon opening after a desired turbine speed and load is achieved.