. . . centrifugal pumps

centrifugal pumps

Centrifugal pumps represent the most common type of pump. The centrifugal pump is efficient, easy to install and maintain, delivering liquids by radial flow - throwing the liquid out and causing the liquid in the resevoir to rise.
The performance of these pumps is usually given as:

• suction lift
  is in fact the atmospheric pressure forcing the water into the pump, so that when the pump starts it creates a vacumn in the pump chamber. Altitude, temperature and air vapour can affect the operation of the pump and its performance.

The suction lift is the vertical rise from the top of the water surface to the centre level of the pump.

• pressure
  which is equivilant to the weight of an imaginary column over a small area of the bottom of the tank.
  kilograms per square centimeter If you are measuring in kilograms and using a metric area then the pressure is recorded in kilograms per square centimeter.
  Kilopascals or as a kilopascal reading (kPa )
  Pounds per square inch (psi) of column .
• vacumn
  At sea level, air exerts a pressure of 14.7 psi or 34 feet. If you have a perfect vacumn atmospheric pressure pushes water up to a height of 34 feet which is the theoretical limit for pump suction.

Suction is actually reduced along with other effects that cause limitation on the pump. At high suction levels air vapour bubbles become seperated from the liquid but collapse as they reach the high pressure areas of the pump. This is cavitation which can cause noise and it has the effect of reducing the performance and efficiency of any pump.