(Common values: 100 for standard smoothbore, 80 for rougher/older hose, 120 for smooth bore)
Friction Loss: — PSI
Understanding Fire Hose Friction Loss
Friction loss is a critical factor in firefighting operations. It refers to the pressure lost due to the friction of water moving through a hose. As water is forced through a hose, it rubs against the inner walls, creating resistance. This resistance directly translates into a reduction in pressure available at the nozzle. Accurately calculating friction loss is essential for ensuring adequate nozzle pressure to achieve effective fire streams and for determining the required pump discharge pressure.
The Mathematics Behind Friction Loss
Several formulas are used to calculate friction loss, but a widely recognized and practical one for fire service is the "Nozzlemen Formula" or a variation of it. A common simplified version for smoothbore nozzles is:
FL = (C / 100) * (Q^2) * L
Where:
FL = Friction Loss per 100 feet of hose (in PSI)
C = Hose Friction Loss Coefficient (often 100 for standard hose, but varies)
Q = Flow Rate in Gallons Per Minute (GPM)
L = Length of hose in 100-foot sections (total length / 100)
The calculator uses a slightly modified version to directly provide total friction loss for the given hose length:
This calculation helps firefighters understand how much pressure they are losing over the length of their hose lay. This loss must be compensated for by the fire pump.
Key Inputs Explained:
Flow Rate (GPM): The volume of water being discharged through the hose per minute. This is determined by the nozzle's setting or size.
Hose Diameter (inches): The inner diameter of the hose. Larger diameters generally result in less friction loss for the same flow rate.
Hose Length (feet): The total length of hose being used from the pump to the nozzle. Longer lengths mean more friction.
Hose Friction Loss Coefficient (C): A factor representing the internal roughness and condition of the hose. A lower 'C' value indicates a smoother, less restrictive hose, resulting in lower friction loss. A 'C' of 100 is a common baseline for standard fire hose.
Why is This Important?
Understanding and calculating friction loss is vital for:
Ensuring Adequate Nozzle Pressure: Firefighters need sufficient pressure at the nozzle to create an effective fire stream.
Setting Pump Discharge Pressure: Firefighters must set the fire pump to a discharge pressure that accounts for friction loss and any elevation changes, plus the required nozzle pressure.
Hose Lay Optimization: Choosing the right hose diameter and length can significantly impact available pressure and firefighting effectiveness.
System Design: For fixed systems or standpipes, accurate friction loss calculations are essential for proper system design.
This calculator provides a quick and easy way to estimate friction loss, aiding in tactical decision-making and safe operational planning. Remember that this is an estimation, and actual friction loss can vary based on hose condition, couplings, and flow dynamics.
function calculateFrictionLoss() {
var flowRate = parseFloat(document.getElementById("flowRate").value);
var hoseDiameter = parseFloat(document.getElementById("hoseDiameter").value); // This value is implicit in the coefficient for common formulas, but we can use it if a diameter-specific coeff is implemented later. For now, we focus on the 'C' value.
var hoseLength = parseFloat(document.getElementById("hoseLength").value);
var hoseCoeff = parseFloat(document.getElementById("hoseCoeff").value);
var resultDiv = document.getElementById("result").querySelector("span");
// Validate inputs
if (isNaN(flowRate) || isNaN(hoseLength) || isNaN(hoseCoeff) || flowRate <= 0 || hoseLength <= 0 || hoseCoeff <= 0) {
resultDiv.textContent = "Invalid Input";
return;
}
// Using the simplified formula: Total FL = (C * (Q^2) * HoseLength) / 10000
// Where FL is in PSI, C is the coefficient, Q is GPM, and HoseLength is in feet.
// This formula is derived from FL per 100ft = (C/100) * Q^2 * (L/100), which simplifies.
var frictionLoss = (hoseCoeff * Math.pow(flowRate, 2) * hoseLength) / 10000;
// Display the result, formatted to two decimal places
resultDiv.textContent = frictionLoss.toFixed(2) + " PSI";
}