1. What is Pump Horsepower?

Pump horsepower (HP) is the power required to move a fluid at a specified flow rate against a specified head. It accounts for the fluid's properties (specific gravity) and the pump's efficiency.

2. How Does the Calculator Work?

The calculator uses the pump horsepower formula:

Where:

• \( Q \) — Flow rate in gallons per minute (GPM)
• \( H \) — Total dynamic head in feet
• \( SG \) — Specific gravity of the fluid (dimensionless)
• \( \eta \) — Pump efficiency (decimal between 0 and 1)
• 3960 — Conversion factor to horsepower

Explanation: The formula calculates the power needed to move a fluid against gravity and system resistance, adjusted for the fluid's density and pump efficiency.

3. Importance of Pump Horsepower Calculation

Details: Proper horsepower calculation ensures you select a pump with adequate power for your application, prevents under/over sizing, and helps with energy efficiency planning.

4. Using the Calculator

Tips:

• Flow rate: Measure or estimate your system's required flow in GPM
• Head: Calculate total dynamic head including elevation, friction, and pressure differences
• Specific gravity: 1.0 for water, higher for denser fluids
• Efficiency: Typical pump efficiencies range from 0.5 to 0.9 (50-90%)

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between brake horsepower and water horsepower?
A: Water horsepower is the theoretical power needed to move the fluid, while brake horsepower includes pump inefficiencies (what the motor must actually deliver).

Q2: How does viscosity affect horsepower requirements?
A: Higher viscosity fluids require more power due to increased friction. The calculator works best for Newtonian fluids with viscosities similar to water.

Q3: What if my pump has variable speed?
A: Horsepower requirements change with speed (approximately with the cube of the speed ratio). This calculator gives the requirement at the specified operating point.

Q4: How accurate is this calculation?
A: It provides a good estimate for centrifugal pumps. Positive displacement pumps may require different calculations.

Q5: Should I add a safety factor?
A: Yes, typical practice is to add 10-20% to the calculated horsepower for safety margin and future needs.