6. A reminder of some practical information

6.1 Speed variation laws

Any centrifugal or side-channel pump is subject to certain physical laws when the drive speed varies, namely :

• the flow ratio is equal to the velocity ratio ;

• the ratio of the heights or pressures generated is equal to the square of the ratio of the speeds ;

• the ratio of absorbed power is equal to the cube of the ratio of speeds.

Any increase in speed (e.g. motor change or pulley change in a belt drive) can overload the original motor, making it inadequate.