1. What is Fire Pump Flow Rate Calculation?

Definition: This calculator determines the flow rate (in gallons per minute) that a fire pump can deliver based on its horsepower, efficiency, total head, and fluid density.

Purpose: It helps fire protection engineers and designers properly size fire pumps for building protection systems.

2. How Does the Calculator Work?

The calculator uses the hydraulic power formula:

Where:

• \( Q \) — Flow rate (gallons per minute, GPM)
• \( HP \) — Pump horsepower (HP)
• \( \eta \) — Pump efficiency (0-1, dimensionless)
• \( H \) — Total head (feet)
• \( \rho \) — Fluid density (pounds per gallon, lb/gal)

Explanation: The formula converts mechanical power (HP) to hydraulic power, accounting for pump efficiency and fluid properties.

3. Importance of Fire Pump Calculations

Details: Accurate flow rate calculations ensure fire pumps can deliver adequate water pressure and volume to meet fire protection system demands.

4. Using the Calculator

Tips: Enter the pump horsepower, efficiency (default 0.75), total head in feet, and fluid density (default 8.34 lb/gal for water). All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What is the constant 3960 in the formula?
A: This is a conversion factor that relates horsepower to foot-pounds per minute (1 HP = 3960 ft-lb/min).

Q2: What's a typical efficiency for fire pumps?
A: Most fire pumps operate at 70-85% efficiency (0.7-0.85). The default is 0.75 (75%).

Q3: How do I determine total head?
A: Total head includes static head, friction losses, and pressure requirements. Consult hydraulic calculations for your system.

Q4: Why does density matter?
A: Heavier fluids require more energy to pump, reducing flow rate at constant power. Water at 60°F is 8.34 lb/gal.

Q5: Does this account for system curves?
A: No, this calculates maximum theoretical flow. Actual flow depends on system characteristics and pump curves.