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VaporTEK Pump
VaporTEK System Description
MDE-5394B VaporTEK™/VaporTEK-3 Controller Board 110 V UL® Vapor Recovery Collection System for Encore® 500 S
Start-Up and Service Manual · March 2019
VaporTEK Pump Operation
The VaporTEK pump is a variable-speed piston pump. The flow rate is proportional to the
speed, and the pump achieves maximum flow rate at 2500 rpm.
The inlet and outlet pressure/vacuum also affects the flow. These are determined by the system
in which the pump is operating. That is, the restrictions at the inlet to the pump (nozzle, flow
meters, tubing, and fittings) and at the outlet of the pump (piping to a sealed UST) limit the
flow being delivered. The design point for the VaporTEK pump in the Encore dispenser is
approximately 150 mbar inlet vacuum (850 mbar absolute pressure) and 100 mbar outlet
pressure (1100 mbar absolute pressure).
The relationship between the pump flow and the suction pressure is shown in
.
Figure 3-2: Relationship Between Pump Flow Rate and Suction Pressure
shows that the flow at 150 mbar suction pressure and the 100 mbar discharge
pressure is approximately 95 LPM. This is the design point of the system. It defines the
conditions under which the pump operates with the nozzle wide open, and is illustrated by the
small dot on the curve above.
During operation, the inlet vacuum and, to some extent, the vapor flow is controlled by the
vapor valve in the nozzle. When the nozzle is fully open, dispensing the maximum amount of
fuel and collecting the maximum amount of vapor, the pump draws a vacuum of about
150 mbar through all the other restrictions in the lines. As the nozzle closes, the vacuum
increases with the closing of the vapor valve and the vapor flow decreases accordingly.
However, the vapor valve does not control the flow precisely enough to satisfy the regulations
that govern the recovery of vapor. In most regions where monitoring of the vapor recovery is
mandated, the requirement is that the vapor flow be within 15% of the liquid being dispensed.
If the control of the vapor flow were left up to the opening of the vapor valve in the nozzle
alone, the vapor collection would frequently go outside the allowable range.
