Filter
Spill Funnel
Strainer located
inside the casting
Coupling part
of iMeter base
Figure 2.2: Strainer Casting, Filter, and Spill Funnel
2.3 Strainer and Filter Suction Pumps
Refer to the Suction Pump section of this manual for details.
2.4 Proportional Flow Control Valve
The proportional flow control valve is a pilot-operated solenoid valve located between the meter
and the hose outlet. The valve performs two basic functions. It regulates the ratio of blended
feedstocks, and it controls the flow rate by limiting the maximum flow rate through a given hose.
The valve and coil are shown in Figures 2.3 and 2.4. The IEC and NA regions use the same
valve. The coils are slightly different in shape, but they are both ASCO coils and they operate
in much the same manner as described below.
The valve is controlled by a 24 VDC pulse width modulated (PWM) signal with 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 piston controls
the amount of flow. Normally closed, the pilot opens by an amount proportional to the amount
of current sent to the valve coil. As the pilot raises off its seat, it reduces the pressure to the back
side of the piston causing it to lift off of its seat as well. The same applies to the valve closing.
In blender models, the piston follows the pilot back to the closed position as the current to the
coil is reduced. During a sale, the iGEM computer continually adjusts the current to the valves
based on the desired blend ratio of the two feedstocks and the maximum allowable flow rate. In
blenders, the high and low products remain separate until they are mixed at the hose outlet.
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.
WM048523 Rev 08 01/2019 15
2 Hydraulics
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