Leadership

Universal Friction Loss Formula

Issue 4 and Volume 131.

Universal Friction Loss Formula Most fire science students and pump operators eventually become familiar with the given formula used in determining engine discharge pressure for a given hose layout: EP = NP + FL + BP Where: EP = engine pressure (pump discharge) NP = nozzle pressure FL = pressure loss due to frictional effects in hose BP = back pressure, or pressure due to difference in elevation between pump and nozzle Here we have a fire fighter’s version of the Bernoulli equation, stating quite surely that energy in a hose line is neither created nor destroyed, but rather converted from one form to another. The formula is quite simple and can be mastered by even the most casual of pump operators. Nozzle pressures specified for today’s fog nozzles are quite universally in the vicinity of 100 psi. A straight tip is ideally operated at 50 psi for a hand…

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