Pump Calculations



PUMP SHAFT POWER

Enter the flow rate, head and efficiency to calculate the power absorbed by a pump.

This is the shaft power required by the pump and is also the power that is shown on the pump performance curve.

Click on the Calculate options (drop down list) to select which value to calculate



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ELECTRICAL POWER

Calculate the electrical power consumed by a pump, including efficiency losses through the pump, motor and drive. The drive could be a VSD, pulley drive or gearbox

Electrical power is what we pay for so we want to make sure that the overall efficiency losses are kept as low as possible. This is sometimes referred to as the wire to water efficiency


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SPECIFIC SPEED (Ns)

The term impeller specific speed is used to classify impellers of various types based on their performance. Specific speed is defined as that speed at which a geometrically similar pump would deliver one unit of flow to one unit of head.

Input values for Flow and Head or NPSHR that correspond to the the pump performance at optimum (or best) efficiency point. In this example, calculate the specific speed in either Metric or US units.


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SUCTION SPECIFIC SPEED (Nss)

Suction Specific Speed (Nss) like Specific Speed (Ns) is a parameter, or index of hydraulic design describing the suction capabilities and characteristics of a given first stage impeller.

Input values for Flow and NPSHR that correspond to the the pump performance at best efficiency point and calculate the suction specific speed in either Metric or US units.


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AFFINITY LAWS CALCULATION

Calculate the effect of a change of speed or impeller diameter on pump flow rate, head and power.

These laws apply accurately when varying the speed but care should be taken when trimming the impeller as the physical changes to the geometry of the pump make the calculations less accurate, particularly for pump power



IMPELLER TIP SPEED CALCULATION

Calculate the tip speed of an impeller - the velocity at which the fluid leaves the impeller vane. This speed is critical to the performance of the pump.

For slurry applications, keep the speed below 28 m/s to prevent excessive wear on the pump internals
For clear liquids tip speeds up to 42 m/s are common for mild steel or cast iron impellers, while bronze and stainless steel impellers can go as high as 50 m/s


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Minimum Suction Pipe Submergence

Calculate the minimum submergence required for the suction pipe to prevent air entrainment