How do I calculate pump power?

P=ρgQH/η. ρ=density, g=9.81, Q=flow(m³/s), H=head(m), η=efficiency.

What is typical pump efficiency?

Small: 50-65%. Medium centrifugal: 70-80%. Large: 80-90%.

Hydraulic=useful fluid power. Shaft=hydraulic/efficiency. Motor≥shaft power.

P(bar)=ρgH/100000. Water: 10m≈1bar.

Net Positive Suction Head. Insufficient NPSHa causes cavitation.

Free Engineering Tool — #155

Calculate pump power from flow rate, head, density, and efficiency. P=ρgQH/η.

P = ρgQH/ηkW & hp

Shaft Power

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Power (hp)

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Hydraulic Power

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Flow Rate

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Pump System Diagram