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Fire Hose Flow Equation:
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The fire hose flow equation calculates the flow rate of water through a fire hose in gallons per minute (GPM) based on the hose diameter and water pressure. This calculation is essential for firefighting operations to ensure adequate water supply and proper nozzle selection.
The calculator uses the fire hose flow equation:
Where:
Explanation: The equation accounts for the relationship between hose diameter, water pressure, and resulting flow rate, with 29.7 being a constant that incorporates conversion factors and the coefficient of discharge for typical fire hoses.
Details: Accurate GPM calculation is crucial for firefighting operations to determine water requirements, select appropriate pump settings, and ensure effective fire suppression. It helps in planning water supply needs and determining the reach and effectiveness of fire streams.
Tips: Enter hose diameter in inches and water pressure in psi. Both values must be valid (diameter > 0, pressure ≥ 0). For accurate results, use the actual measured diameter of the hose and the operating pressure at the base of the hose.
Q1: Why is the constant 29.7 used in the equation?
A: The constant 29.7 incorporates conversion factors (from inches to gallons) and accounts for the typical coefficient of discharge for fire hoses, which is approximately 0.98-0.99.
Q2: Does hose length affect the flow rate?
A: While the basic equation doesn't include length, longer hoses will have greater friction loss, which reduces the effective pressure at the nozzle and thus decreases flow rate.
Q3: What are typical GPM values for fire hoses?
A: Common fire hoses range from ½" to 6" in diameter, with flows from 10 GPM for small attack lines to over 1000 GPM for large supply lines.
Q4: How does nozzle type affect the calculation?
A: This calculation provides flow at the base of the hose. Nozzles create additional pressure drop, so actual discharge will be less than calculated unless nozzle pressure is accounted for.
Q5: Is this equation accurate for all hose types?
A: The equation works well for standard fire hoses. Specialized hoses with different internal coatings or construction may have slightly different flow characteristics.