Cam-driven valve system for steam turbines

Abstract

A steam turbine system including a source of motive steam and a turbine adapted to operate at less than a full load and normally provided with two separate valve chests each incorporation a plurality of commonly controlled valves, is modified to improve turbine efficiency by separating the camshafts for each group of control valves associated with each of the steam chests such that the valves associated with each of the steam chests may be operated in two distinct groups. In one form, the steam chests are each associated with four valves and the camshafts are split so that each section of camshaft controls two valves. In this form, the turbine is initialized at 50 percent admission by opening two sets of valves and thereafter the admission is increased in 25 percent increments by sequentially opening the other two valve sections. In another form, the valves are divided into groups of three and one in each steam chest and initial operation at 50 percent admission is achieved by opening one group of three and one single valve. Thereafter the valves can be appropriately opened and closed so as to step admission in 12.5 percent increments. A similar arrangement is provided for turbines utilizing other numbers of valves such as six.

Dependencies are inferred from the claim text.