Understanding Pump Power Calculations

Correctly sizing a pump motor is critical to prevent overloading and ensure longevity. This calculator determines the Shaft Power (Brake Horsepower) required to drive the pump and recommends a standard electrical motor size based on API 610 safety margins.

[Image of centrifugal pump performance curve]

Hydraulic vs. Shaft Power

Hydraulic Power is the theoretical energy actually transferred to the fluid. However, no pump is 100% efficient. Shaft Power accounts for mechanical and hydraulic losses inside the pump casing. The formula used is:

Shaft Power (kW) = (Flow × Head × Gravity × SG) / (3600 × Efficiency)

Safety Margins (API 610)

To ensure reliability, motors are sized larger than the required shaft power. Common industry standards suggest:
• 125% margin for motors < 22 kW
• 115% margin for motors 22–55 kW
• 110% margin for motors > 55 kW

Model Your Pump in Aspen HYSYS

Calculating power is just the first step. To simulate how this pump performs under varying process conditions or to generate a full system curve, you need advanced simulation tools. Learn how to model pumps, piping, and control valves in our Aspen HYSYS Training Courses.