Part No. 920525 Rev A - Wayne 3/VISTA series Service Manual

5.3. PROPORTIONAL FLOW CONTROL VALVE continued
The pilot operated proportional solenoid valve performs three basic functions in the
dispenser. It provides positive shutoff, regulates the ratio of blended feedstocks, and
controls the flow rate through the hydraulic path by limiting the maximum flow rate
through a given hose.
The pilot operated proportional flow control valve consists of two main parts:
• The proportional valve
• The valve coil
The proportional valve is an electrically operated solenoid made up of a body and an oper-
ator. It controls all flow through the dispenser.
The valve coil controls the operator of the valve. The coil is energized with a pulse width
modulated (PWM) signal that sends discrete "bursts" of current at a set frequency level.
When the coil receives this signal, the pilot inside the operator reacts to the changing
magnetic field and moves up and down depending on the amount of current through the
coil. The position of the pilot relative to the pilot orifice in the diaphragm controls the
amount of flow.
In all Wayne dispensers using this valve, the general order of operation is the same. At the
beginning of a sale, the coil is energized with a minimum current level, allowing slow
product flow to start. After a small amount of product is delivered, the coil is energized with
more current to initiate full regulated flow. For preset sales, the dispenser will switch back
to slow flow at a pre-determined point.
5.2.1. Flow Control Valve "Off" No Flow
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 a submersible pump motor is running because another fueling
point is being used. The pilot stays closed allowing pump pressure to build on
the back side of the diaphragm, closing the outlet port.
5.2.2. Flow Control Valve "On" Slow Flow
Flow control valve "On" slow flow occurs at the beginning of all sales, and
again at the end of preset sales. In this case the coil is energized with current
bursts of shorter duration. This allows the pilot to slightly move off its seat,
allowing slow flow through the pilot orifice leading to the valve outlet, but not
relieving enough pressure to cause the diaphragm to open.
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Part No. 920525 Rev A

June 2001