Flow Control Valve Relieving Back Pressure; Meter; Meter Adjustment - Wayne Vista Series Service

5.2.5. Flow Control Valve Relieving Back Pressure (see Figure 5-6)
In this instance as the pressure builds, it lifts the slow flow poppet off of its
seat and passes through the port (4) into the center chamber. Once the pres-
sure reached approximately 35 psi the relief valve (6) would open allowing
product into the outer chamber, where it would flow through the port (2) into
the inlet chamber, and from there back into the underground tank.
5.3. METER (see Figure 5-7)
The meter is, in effect, a three-cylinder motor, using cylinders 'B' and 'C' and chamber
'D' as the three cylinders. Because the filling and discharging ports in the valve are
located 120° apart, and the port openings in the valve seat are at 120°, there is no dead-
center position in the meter. The operation of filling is continuous, in that before one
chamber is fully filled, the next one is in the process of starting to fill. The same proce-
dure applies to the discharging operation. The filling and discharging operations each
occupy 180° of rotation. Measurement of flow is determined by the fact that the dis-
placement of each cylinder, together with the displacement from chamber 'D', represents
a known quantity, and the flow has a direct and substantially constant relationship to the
rotation of the output shaft.
By connecting the output shaft to the pulser assembly, the rotary movement of the meter
can be converted into pulses, which can in turn be counted by the computer. Calibration
is made possible by the incorporation of an adjusting knob on the top of the unit. Move-
ment of this knob causes the throw of the crank arm on the output shaft to be varied, so
that the speed at which the shaft rotates can be accurately adjusted to the known output of
the meter.
5.3.1. Meter Adjustment (see Figure 5-8)
While the dispensers leave the factory properly adjusted, rough handling in
transit or special installation conditions can change this. Therefore, before
placing the dispenser in operation, these items must be checked and adjusted,
if required.
If meter adjustment is required, the adjustment knob is located on the top of
the meter; see Figure 5-8. If the test can reads low, break the seal, lift the
adjustment knob and turn in a clockwise direction, viewing the knob from the
top of the meter. The lower portion of the knob is hexagonal and, in a normal
position, the portion of the knob is inserted in the output shaft assembly.
There are 18 vertical notches within the shaft, therefore, as the adjustment is
made, the knob can be felt to click over the leading edge of the notches. Each
notch is equivalent to a correction of approximately one cubic inch in five
gallons. After the meter has been adjusted and brought within tolerance,
replace the seal wire and seal by pinching the lead lock on the wire.
38
Part No. 917543 Rev. A November 1992