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LARGE-DIAMETER HOSE HYDRAULICS IN YOUR HEAD

Issue 11 and Volume 144.

LARGE-DIAMETER HOSE HYDRAULICS IN YOUR HEAD A glance at most hydraulics books convinces the average reader that he needs a computer for hydraulics calculation. However, there is a simple way to calculate gpm flowing through large diameter supply hose in your head. HYDRANT PRESSURE, INLET PRESSURE, AND FRICTION LOSS Because of friction loss (FL) in supply hose, the pressure at a hydrant (HP) decreases uniformly along the hose to the pump inlet. Since 10 pounds per square inch (psi) is needed at the pump inlet (maintaining at least 10 psi prevents cavitation, which will damage the pump impeller) the pressure available to overcome friction loss in the supply hose is HP — 10 psi. That is, to determine the pressure available to overcome friction loss in the supply hose, simply subtract 10 psi from the hydrant pressure when flowing. For example, if 1,000 feet of supply hose is laid from…

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