HEAD – The ability of a pump to push a column of water vertically in a pipe. As the column lengthens, the flow rate decreases until the column’s weight just balances the pump’s force and there is no flow. This height is the total head (usually expressed as feet of head).

FLOW RATE – Usually expressed in gallons per minute (GPM) for large-volume pumps; in gallons per hour (GPH) for small-volume pumps.

DYNAMIC SEAL – Seal located at the shaft end of the pump drive.

HECK VALVE – Allows liquid to flow in one direction only. Generally used in discharge line to prevent reverse flow.

DEAD HEAD – Ability of a pump to continue running without damage when discharge is closed off. Only recommended with centrifugal pumps.

DENSITY (specific weight of a fluid) – Weight per unit volume, often expressed as pounds per cubic foot or grams per cubic centimeter.

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 (I/min), or milliliters per minute (ml/min).

FLUIDS – Include liquids, gases, and mixtures of liquids, solids, and gases. For the purposes of this catalog, the terms fluid and liquid are both used to mean a pure liquid or a liquid mixed with gases or solids that acts essentially like a liquid in pumping applications.

FOOT VALVE – A type of check valve with a built-in strainer. Used at point of liquid intake to retain liquid in system, preventing loss of prime when liquid source is lower than pump.

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, assuming negligible friction losses.

PRESSURE – The force exerted on the walls of a container (tank,,pipe etc.) by a liquid. Normally measured in pounds per square inch (psi) for positive displacement and metering pumps.

PRIME – A charge of liquid required to begin pumping action when liquid source is lower than pump. May be held in pump by a foot valve on the intake line, or by a valve or chamber within the pump.

SEAL – A device mounted in the pump housing and/or on the pump
shaft, to prevent leakage of liquid from the pump. There are three types:

1. LIP – A flexible ring (usually rubber or similar material) with the inner edge held closely against the rotating shaft by a spring.
2. MECHANICAL – Has a rotating part and a stationary part with highly polished touching surfaces. Has excellent sealing capability and long life, but can be damaged by dirt or grit in the liquid.
3. PACKED – Multiple flexible rings mounted around the pump shaft and packed together by tightening gland nuts; some leaking is essential for lubrication.

RELIEF VALVE – Usually used at the discharge of a positive displacement pump. An adjustable, spring­loaded valve opens when a preset pressure is reached. Used to prevent excessive pressure buildup that could damage the pump or motor.

SEALLESS (MAGNETIC DRIVE) – No seal is used; power is transmitted from motor to pump impeller by magnetic force.

SELF-PRIMING – Refers to pumps that draw liquid up from below pump inlet (suction lift), as opposed to pumps requiring flooded suction.

SPECIFIC GRAVITY – The ratio of the weight of a given volume of liquid to the same volume of pure water. Pumping heavier liquids (specific gravity greater than 1.0) will require more drive horsepower.

STATIC DISCHARGE HEAD – Maximum vertical distance (in feet) from pump to point of discharge with no flow.

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, suction lift, and friction loss.

VISCOSITY – The “thickness” of a liquid, or its ability to flow. Most liquids decrease in viscosity and flow more easily as they get warmer.