Compressed air control system refinements

摘要

A compressed air control system has a plurality of air-conducting airways connected between upstream and downstream headers. A control valve arrangement utilizes a main analog flow control valve in one of the parallel airways and at least one digital trim valve in another of the parallel airways. The control and trim valves respond to pressure changes in the downstream header and ensure that the control valve never closes more than 25 percent and never opens beyond 75 percent so as to stabilize system pressure.