1. What is the Pump Power Equation?

Definition: This equation calculates the horsepower required by a pump to move fluid at a specified flow rate against a given head pressure.

Purpose: It helps engineers and technicians properly size pumps for various fluid transfer applications.

2. How Does the Equation Work?

The equation uses the formula:

Where:

• \( HP \) — Horsepower required
• \( Q \) — Flow rate (gallons per minute, GPM)
• \( H \) — Total head (feet)
• \( \rho \) — Fluid density (pounds per gallon, lb/gal)
• \( \eta \) — Pump efficiency (decimal, typically 0.5-0.9)

Explanation: The numerator represents the hydraulic power needed, while the denominator (3960) converts units to horsepower and accounts for efficiency.

3. Importance of Pump Power Calculation

Details: Accurate power calculation ensures proper pump selection, prevents under/over sizing, and optimizes energy consumption.

4. Using the Calculator

Tips: Enter flow rate in GPM, head in feet, density (default 8.34 lb/gal for water), and efficiency (default 0.85). All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What is the 3960 constant?
A: It's the conversion factor that results from combining unit conversions to get horsepower (1 HP = 550 ft-lb/sec).

Q2: What's a typical pump efficiency?
A: Centrifugal pumps typically range from 50-90% efficiency (0.5-0.9), depending on size and design.

Q3: How do I determine total head?
A: Total head is the sum of static head, friction losses, and pressure differences in the system.

Q4: What density should I use for other fluids?
A: For other fluids, use their specific weight divided by 7.48 (gallons per cubic foot). Example: oil at 55 lb/ft³ would be 55/7.48 = 7.35 lb/gal.

Q5: Does this include motor sizing?
A: No, motor size should be 10-20% larger than pump HP to account for startup loads and inefficiencies.