Pump Terminology

How to Size and Specify a Pump

Bubbles (cavities) in liquid created by the low pressure (usually the back side) of the pump impeller blades.

The imploding or collapsing of these bubbles triggers shockwaves inside the pump causing

damage to the impeller and pump housing.

When a gas is formed and trapped in a pump causing the pump to lock up and cease to work.

A valve can be present to release the trapped gas.  This usually occurs during start up of the pump.

Positive Displacement Pump

Example: Gear Type Pump

For every cycle of the pump a fixed amount of fluid is pushed through the pump.

This is a function of the mechanical design of the pump.

This type pump is usually used for thicker liquids such as oil

Variable Displacement Pump

Example: Centrifugal Pump

For every cycle of the pump the amount of fluid pushed through the pump is variable.

This is a function of the mechanical design of the pump.

This type pump is more efficient for thinner liquids.

Pump Head Pressure

The vertical distance that the pump can perform at a given pressure and flow rate

Expressed in vertical feet or meters.  

An expression of what forces the pump can overcome or needs to overcome. 

The vertical distance from the fluid to the pump

Submersible Pump

A pump that operates by being immersed in the liquid that it is pumping.

Example: Sump Pump

Sanitary Pump / Food Grade Pump

Example: Sanitary Positive Displacement Pump

A pump that is designed for food or agriculture use and as such needs to be clean in order to prevent disease.

Self Priming Pump

A pump that can be located above the liquid to be pumped and have a dry line from the pump to the liquid.

The pump will be able to prime itself (draw suction on the liquid) up to a given distance.

A pump that is NOT self priming will need the liquid to be present in the line all the way to the pump.

A foot valve can be used with a NON self priming in order to keep the suction line wet and avoid the need for a self priming pump.

A pump that is designed to take suction on a liquid that includes solids up to a given size.

Typically a variable displacement type centrifugal pump and submersible.

Applications: Truck loading dock sump for rain water and any debris.

Macerator Pump

A pump designed with cutting blades that will cut up the solids in the liquid during pumping.

Applications: Sewage

Blending or Shear Pump

A pump that is designed to blend (mix together) or dice up solids as the liquid and/or solids pass through the pump.

Typically a Blending or Shear pump is for food processing applications.