Replace the pump with a variable-frequency model
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The motor of the polypropylene feeding pump in our company operates at 2930 rpm (head: 160 m, rated flow rate: 16.8 m³/h); the actual flow rate is around 20 tons. After installing a variable frequency drive, it is no longer possible to meet the existing flow requirements. The motor now operates at 2830 rpm (head: 160 m, rated flow rate: 16.8 m³/h), with an actual flow rate of around 9 tons
After frequency conversion, the flow rate is proportional to the speed ratio, while the head is proportional to the square of the speed ratio. Can the head after frequency conversion meet your pressure requirements? If the flow rate required by the pump cannot be met, it will definitely be low.
The pressure can be achieved, but the actual flow rate cannot.
How much head is actually needed? The flow and head curve of a pump is a downward-sloping curve; it is the curve at the top of the figure. The head is high when the flow rate is low, and it is low when the flow rate is high. The flow rate after pump speed adjustment is 16 cubic meters per second, at 149 m. If your system requires a head of 152 meters, then a head of 149 meters will not be sufficient for delivery; the pump’s flow rate will decrease. When the flow rate drops to 10 cubic meters, the head at that point will still be 152 meters.
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