Since a metering pump is usually a positive displacement pump there are two possible ways of controlling the flow capacity. The first one is by adjusting the volume of liquid displaced per stroke of the pump and the second is by adjusting the speed of the strokes.
I. Stroke Length – control the displacement volume per stroke
II. Speed of Strokes per minute
1. Stroke Length – Manual: All AquFlow hydraulic diaphragm metering pumps come with a standard manual knob to adjust the volume from 100% down to 5% or 10% without compromising the accuracy. On AquFlow pumps you can adjust the manual knob even while the pump is running unlike some other pumps where you have to turn the pump off before adjustment.
2. Stroke Length – Automatic ECCA: The stroke length can also be controlled automatically with an electronic signal (usually 4-20mA) coming from a source such as SCADA, PLC or a computer.
3. Stroke Speed / Frequency – VFD: We can adjust the speed of the pump by connecting a VFD to run the motor. Here again you can achieve very low flows by reducing the speed of the pump.
4. Dual Axis Control – Stroke Length And Stroke Speed Combined: Here we get the ultimate in control to the finest resolution by combining both the Stroke Length as well as the Stroke Speed. This can e done with a manual adjuster or automatic with electronic signal.