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Centrifugal pumps are negative displacement pumps meaning that their flow rate depends on the pressure on the discharge end. Flow enters the white/gray piece (in the picture below) and is pushed upward through the black port (perpendicular to the entrance port) by a motor driven propeller. Each of these pumps are designed to operate efficiently at a given discharge pressure which can be found in the manufacturer's manual. The flow rate of these pumps cannot be set by Process Controller - it can only turn the pump ON or OFF. They can only be used with a stamp box as the voltage required to operate them is higher than can be supplied by the stamp box.
