OPERATION OF BALANCED SOLENOID VALVES
Technical Bulletin 105
When power is applied to the Solenoid (1) of a valve in the normal or de-energized position, the Armature (2) is stroked upward, pulling the Poppet Assembly (3) with it. When the power is removed, the Poppet Assembly (3) and Armature (2) are pushed downward by the Spring (4). The Shoulder Stops On the Poppet Assembly control this movement within precise limits providing optimum seat indentation and armature head space (when solenoid is energized). This assures low pull-in and high drop-out voltages and unrestricted flow through the valve when in the open position.
Essential to balanced pressure operation is the maintenance of an exact seating area. Although it is relatively easy to balance pressure forces with dynamic bore seals, it is extremely difficult to maintain exact sealing areas with a Resilient Valve Seat.
In the de-energized or energized positions, pressures are retained between two O-rings (the valves use O-rings for seats and dynamic seals) whose effective sealing areas are equal. For this reason, pressure forces acting on the Poppet Assembly are equal and opposed. Pressure balancing in this manner minimizes and stabilizes Solenoid and Spring forces required for valve actuation over the entire operating pressure range. Static and dynamic o-ring friction resulting from pressure is kept to a minimum by special Back-up Rings that also prevent extrusion of the o-rings at high pressures.