TM 10-4320-344-10SECTION II. DEFINITION OF UNUSUAL TERMSThe following definitions include the terms used in this manual that are notdefined in the text or not listed in the Army Dictionary (AR 310-25).Head- The pressure against which a pump forces liquid, expressed in feet.Each pound of pressure per square inch against which the liquid is forced isequivalent to lifting a column of water l-inch square and 2.31 feet high.Thehead includes the height to which the liquid must be raised plus the forcerequired to overcome friction losses in the pipeline or hoseline.Net positivesuctionhead- The absolute pressure at the pump inlet expressed infeet of liquid, plus velocity head, minus the vapor pressure of the fluid atpumping temperature.If the inlet liquid is exposed to the atmosphere, it isalso necessary to correct for the elevation at the entrance to the pump impeller.Suction Pressure - As used on pump suction gauges, the negative or positivepressure at the pump suction inlet.It will be a negative pressure if the inletliquid is exposed to the atmosphere below the suction inlet (such as a sourcepump taking water from a well, stream, or lake).It will be a positive pressureif the inlet liquid is from an elevated source (such as a storage tank) or anupline pump.Totaldischarqehead- The sum of the suction pressure and the discharge pressure,expressed in feet.Glossary 2
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