1. What is the Fire Pump Power Equation?

The fire pump power equation calculates the required horsepower for a pump based on flow rate, head pressure, fluid specific gravity, and pump efficiency. It's essential for proper fire protection system design.

2. How Does the Calculator Work?

The calculator uses the pump power equation:

Where:

• \( Q \) — Flow rate (gallons per minute, GPM)
• \( H \) — Total head (feet)
• \( SG \) — Specific gravity of fluid (1.0 for water)
• \( \eta \) — Pump efficiency (decimal, typically 0.7-0.9)
• 3960 — Conversion factor (ft-lb/min per HP)

Explanation: The equation converts the hydraulic power (flow × head × specific gravity) to mechanical power (horsepower) accounting for pump efficiency.

3. Importance of Pump Sizing

Details: Proper pump sizing ensures adequate water supply for fire protection while avoiding oversized pumps that waste energy and increase costs.

4. Using the Calculator

Tips:

• For fire protection systems, use the required flow rate from hydraulic calculations
• Include all head losses (friction, elevation, nozzle pressure)
• Typical pump efficiency ranges from 70-85% (0.7-0.85)
• For fluids other than water, adjust specific gravity accordingly

5. Frequently Asked Questions (FAQ)

Q1: What's a typical efficiency value for fire pumps?
A: Most centrifugal fire pumps operate at 70-85% efficiency at their rated capacity.

Q2: Should I add a safety factor to the calculated HP?
A: Yes, it's common to add 10-15% to account for system variations and future needs.

Q3: How does specific gravity affect pump size?
A: Heavier fluids (SG > 1) require more power, lighter fluids (SG < 1) require less.

Q4: What's the difference between total head and static head?
A: Static head is just elevation difference, while total head includes friction losses and pressure requirements.

Q5: How do I select an actual pump based on this calculation?
A: Choose the next available standard motor size above your calculated HP, considering manufacturer curves.