Flow Control Valve "Off" No Flow; Flow Control Valve "On" Slow Flow - Wayne Vista Series Service

5.2.1. Flow Control Valve "Off" No Flow (see Figures 5-1 and 5-2)
Flow control valve "off" or no flow occurs when the inlet to the valve is
charged, but there is no flow required from the particular valve, as in the
instance, where the submersible pump motor is running because another
fueling point is being used. The inlet and the "inlet chamber" (A) are charged
with the pump pressure. This pressure passes through a port (2) from the inlet
chamber to the "outer chamber" (B). From there the product passes through
the orifice (3) into the "center chamber" (C), then through a passageway (4),
and into the 2-stage actuator (1).
The pressure in the inlet chamber and the center chamber are equal at this
point. Because the area of the diaphragm material (8) exposed to the inlet
chamber is approximately half that exposed to the center chamber, the force
holding the diaphragm closed is twice that which is trying to open it. There-
fore, the diaphragm material (8) remains in the closed position covering the
outlet port.
5.2.2. Flow Control Valve "On" Slow Flow (see Figure 5-3)
Flow control valve "on" slow flow occurs at the beginning of all sales, and
again at the end of preset sales. The pressures remain the same as described in
Section 5.2.1.1. The difference is that the slow flow actuator coil (omitted for
clarity) has been energized. This causes the slow flow poppet (12) to be
pulled off of its seat exposing a path (5) to the outlet. The flow through this
path is so slow that the pressure in the center chamber (C) is not reduced.
Therefore, the diaphragm remains in the closed position.
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Part No. 917543 Rev. A November 1992