PNEUMATIC VOLUME BOOSTER FOR VALVE POSITIONER

摘要

The system controls the position of a pneumatically operated valve (12) usin g an electrical control signal from a controller (26). A pilot circuit (22) of the system has multiple piezo valves (30, 32) that are subject to electrical signals from the controller to provide pneumatic output signals to a volume booster circuit (20) of the system. Relatively small volume pneumatic pilot signals from the piezo valves are used to determine the opened or closed sta te of higher volume valve assemblies of the booster circuit which connect or disconnect the actuator of the valve to be operated with a source of pressurized gas (24). Both the piezo valves and the booster valve assemblies are subjected to gas at the same operating pressure, but the surface area of the pistons (82) exposed to the piezo valves is substantially larger than th e surface area of the pistons exposed to operating pressure such that the pnuematic signals shift the pistons even when pressure is the same on both sides thereof.