A decrease in water pressure during flow due to internal friction between molecules of water, and external friction due to irregularities or roughness in surfaces past which the water flows
For oil hydraulic systems, the following will approximate pressure drop through "short orifice" (1/4 to 1/2-inch long-length not over 3 times diameter): For specified pressure drop: A (required) =
the amount of pressure required to fill that section Adding up the pressure drops over every section in a flow path totals the pressure required to fill the mold
The drop in static pressure of the fluid (air, gas, or water) due to friction or obstruction as the fluid flows through pipe, valves, fittings, regulators, burners, and appliances
Resistance to flow created by the element (media) in a filter Defined as the difference in pressure upstream (inlet side of the filter) and downstream (outlet side of the filter)