Knowing the correct terminology for laboratory pumps helps you understand their functionality. Dead head? We’re not talking about a fan of a 70’s jam band. Find the meaning of this and other terms below.
Cavitation. Process in which small bubbles are formed and implode violently; occurs when NPSHa < NPSHr
Dead Head. The ability of a pump to continue running without damage when discharge is closed off. Only recommended for centrifugal pumps
Density (specific weight of a fluid). Weight per unit volume, often expressed as pounds per cubic foot or grams per cubic centimeter
Discharge Head. The outlet pressure of a pump in operation
Flooded Suction. Liquid flows to pump inlet from an elevated source by means of gravity. Recommended for centrifugal pump installations
Flow. A measure of the liquid volume capacity of a pump. Given in gallons per hour (GPH), gallons per minute (GPM), liters per minute (L/min), or milliliters per minute (mL/min)
Fluids. Include liquids, gases, and mixtures of liquids, solids, and gases
Head. A measure of pressure, expressed in feet of head for centrifugal pumps. Indicates the height of a column of water being moved by the pump (without friction losses)
Pressure. The force exerted on the walls of a tank, pipe, etc., by a liquid (normally measured in pounds per square inch (psi))
Prime. Charge of liquid required to begin pumping action when liquid source is lower than pump. Held in pump by a foot valve on the intake line or by a valve or chamber within the pump
Seals. Devices mounted in the pump housing and/or on the pump shaft that prevent leakage of liquid from the pump.
Self-Priming. Pumps that draw liquid up from below pump inlet (suction lift), as opposed to pumps requiring flooded suction
Shear Rate. The velocity of a liquid per unit distance between two surfaces
Specific Gravity. The ratio of the weight of a given volume of liquid to pure water. Pumping heavy liquids (specific gravity greater than 1.0) will require more drive horsepower
Strainer. A device installed in the inlet of a pump to prevent foreign particles from damaging the internal parts
Sump. A well or pit in which liquids collect below floor level; sometimes refers to an oil or water reservoir
Total Head. Sum of discharge head minus the suction head
Viscosity. The “thickness” of a liquid or its ability to flow—most liquids decrease in viscosity and flow more easily as they get warmer
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