Pump Shaft Power Calculator

| Added in Physics

What is Pump Shaft Power and Why Should You Care?

Pump shaft power is the amount of power your pump's shaft delivers. It helps you determine how efficiently your pump is converting hydraulic power into useful work. Understanding this can save you energy, money, and hassle by optimizing performance, reducing operational costs, and extending pump life.

How to Calculate Pump Shaft Power

First, calculate the hydraulic power:

[\text{Hydraulic Power (kW)} = \frac{\text{Flow Rate (m}^3\text{/hr)} \times \text{Density (kg/m}^3\text{)} \times \text{Gravity (m/s}^2\text{)} \times \text{Pump Head (m)}}{3.6 \times 10^6}]

Where:

  • Flow Rate is the volume of fluid passing through the pump per hour
  • Density is the mass per unit volume of the fluid
  • Gravity is the acceleration due to gravity (9.81 m/s²)
  • Pump Head is the height the pump will lift the fluid

Then calculate the shaft power:

[\text{Shaft Power (kW)} = \frac{\text{Hydraulic Power (kW)}}{\text{Efficiency}}]

Where:

  • Hydraulic Power is the calculated power in kW
  • Efficiency is the pump's efficiency as a decimal (e.g., 75% = 0.75)

Calculation Example

Given:

  • Flow Rate: 500 m³/hr
  • Density: 1,050 kg/m³
  • Pump Head: 4 m
  • Efficiency: 75%

First, calculate Hydraulic Power:

[\text{Hydraulic Power} = \frac{500 \times 1050 \times 9.81 \times 4}{3.6 \times 10^6} \approx 5.72 \text{ kW}]

Then calculate Shaft Power:

[\text{Shaft Power} = \frac{5.72}{0.75} \approx 7.63 \text{ kW}]

The pump shaft power is approximately 7.63 kW.

Frequently Asked Questions

Pump shaft power is the mechanical power delivered by the pump shaft. It accounts for hydraulic power divided by pump efficiency to determine actual motor requirements.

First calculate hydraulic power: HP = (Flow x Density x 9.81 x Head) / 3,600,000. Then divide by efficiency: Shaft Power = Hydraulic Power / Efficiency.

Efficiency represents how well the pump converts electrical energy to hydraulic energy. Lower efficiency means more shaft power is needed for the same hydraulic output.

Pump efficiencies typically range from 60% to 85% depending on pump type, size, and operating conditions. Centrifugal pumps often achieve 70-80% efficiency at their best operating point.