The main valve is diaphragm actuated, hydraulically operated, and consists of four major components. The body and cover plus interior seat and diaphragm/stem assembly, which is the only moving part in the main valve fusion bonded.

The design and innovative features incorporated into every BakerAutomatic Control valve means consistent, dependable, high performance, positive control and long life. A synthetic rubber/nylon diaphragm of reinforced Buna N materials, is assembled between the valve body and cover. This creates a sealed chamber into which line fluid and pressure is introduced. Varying the amount of pressure accurately positions the stem assembly to open, close or modulate the valve as required. A cover bearing and integral seat bearing guides the stem assembly for precise alignment with the seat. Coupled with the quad seal retainer plate, this alignment assures progressive opening/closing flows, stable throttling, low friction operation and positive closure.