Pump Shaft Power Calculator

Shaft Power Formula:

\[ P_{shaft} = \frac{\rho \times g \times Q \times H}{\eta} \]

Fluid Density (ρ):

kg/m³

Flow Rate (Q):

m³/s

Head (H):

Efficiency (η):

(0-1)

Shaft Power (P_shaft):

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1. What is Pump Shaft Power?

Pump shaft power is the mechanical power required to drive a pump, accounting for the energy needed to move the fluid and the pump's efficiency. It's a crucial parameter for selecting motors and assessing pump performance.

2. How Does the Calculator Work?

The calculator uses the shaft power formula:

\[ P_{shaft} = \frac{\rho \times g \times Q \times H}{\eta} \]

Where:

\( P_{shaft} \) — Shaft power (kW)
\( \rho \) — Fluid density (kg/m³)
\( g \) — Gravitational acceleration (9.81 m/s²)
\( Q \) — Volumetric flow rate (m³/s)
\( H \) — Total dynamic head (m)
\( \eta \) — Pump efficiency (0-1)

Explanation: The formula calculates the power required to move a fluid with specific properties at a given flow rate against a certain head, adjusted for the pump's efficiency.

3. Importance of Shaft Power Calculation

Details: Accurate shaft power calculation is essential for proper motor selection, energy consumption estimation, and system design. Oversizing leads to wasted energy, while undersizing can cause motor failure.

4. Using the Calculator

Tips:

For water at standard conditions, density is 1000 kg/m³
Flow rate must be in m³/s (convert from L/s by dividing by 1000)
Efficiency typically ranges from 0.5 to 0.9 for most pumps
Head includes all static and dynamic components

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between shaft power and hydraulic power?
A: Hydraulic power is the theoretical power needed to move the fluid, while shaft power includes the pump's inefficiency (P_shaft = P_hydraulic/η).

Q2: How do I account for motor efficiency?
A: Motor power = Shaft power / Motor efficiency. This calculator only considers pump efficiency.

Q3: What's a typical pump efficiency value?
A: Centrifugal pumps typically range from 40-85% efficiency, with larger pumps generally being more efficient.

Q4: How does viscosity affect shaft power?
A: Higher viscosity fluids require more power and may reduce pump efficiency. Special corrections are needed for highly viscous fluids.

Q5: Can I use this for positive displacement pumps?
A: This formula works best for centrifugal pumps. Positive displacement pumps require different calculations considering pressure rather than head.