- Atmospheric Pressure
The force exerted by the atmosphere on the earth’s surface, which allows a centrifugal pump to operate. At sea level, the atmospheric pressure equals 14.7 PSI. As elevation increases, atmospheric pressure decreases, therefore pump performance also decreases. - Capacity
The water handling capability (volume) of a pump expressed as gallons per minute (GPM). - Cavitation
Status in which the pump impeller is not receiving a full supply of material. This can be due to reduced flow or over rotation. Excessive pump RPM can cause a vortex in the eye of the impeller. Air bubbles attach to the metal surfaces and, under extreme pressure, implode, taking tiny bits of metal away with each implosion, pitting the impeller and volute surfaces. Excessive cavitation can cause severe, permanent damage to the pump components, resulting in poor performance. - Centrifugal Pump
Moves water by displacing liquid from the center of the impeller as it spins to the outer part of the impeller creating a vacuum in the center by means of centrifugal force. The diameter of the impeller predicts the pressure and the width predicts the water flow. - Efficiency
A ratio of total energy output to the total energy input expressed as a percent. - Flow
The measure of the liquid volume capacity of a pump. Given in Gallons Per Hour (GPH) or Gallons Per Minute (GPM) , as well as Liters Per Minute (LPM) - Friction Loss
Reductions in flow due to turbulence as water passes through hoses, pipes, valves, and fittings. This includes both suction and discharge friction losses. - Head (Feet)
1) A measure of the energy possessed by water at a given location in the water system expressed in feet
2) A measure of the pressure or force exerted by water expressed in feet. - Impeller
The moving element in a pump that drives the fluid. - Mechanical Seal
A spring-loaded pump component that forms a seal between the pump and the engine or motor. Pumps designed for working in harsh environments require a more abrasive resistant seal. - NPT
Refers to the National Pipe Thread standard measurement. - Positive Displacement Pump
Remove water from a cavetti or cylinder by directly applying pressure to a diaphragm or piston or a flexible impeller and cam. Check valves are used to preserve the pressure down line except in the case of the flexible impeller and cam. Usually diaphragm or flexible impeller or piston pumps are used for more exact amounts of water and for higher pressures. This makes them ideal for solar applications , RV’s, pressure washers, small cabins, R.O., misters or situations where water demand is low but pressure demand is high. A centrifugal pump is limited in the pressure it can produce unless the design of the pump allows for impeller stacks. This type of pump is usually self priming a few feet. - Pressure Head
A measurement of the amount of energy in water due to water pressure. - Priming
The action of starting the flow in a pump or siphon. With a centrifugal pump, this involves filling the pump casing and suction pipe with water. - Shut-Off
Point in which pump will not push water passed the listed feet in a vertical column . No flow past the listed vertical feet. This does not effect the horizontal run but if the run is very long say 50 or 100 ft. then friction comes into play. - Total Dynamic Head (TDH)
The sum of the dynamic suction head and the dynamic discharge head. Also referred to as Total Head. - Velocity Head
A measurement of the amount of energy in water due to its velocity or motion. - Volute
The casing surrounding the impeller in a centrifugal pump that collects the liquid discharged from the impeller.
Formulas
| Brake Horsepower | = | USGPM x Ft Head x SG | ||
| 3960 x Pump Eff | ||||
| BTU | = | USGPM x ΔT (°F) x 500 | ||