Dynamic pumps unlike positive displacement pumps output fluid over a range of flow values for a given range of rotational values.
Centrifugal pumps are dynamic and are very common in industrial applications. They are typically made up of one main rotating component, an impeller, and several stationary components. The outer housing is the volute aka pump housing or casing, and holds all the components within. It is responsible for the collection and direction of the fluid flow toward the impeller. It is also responsible for the redirection of flow out of the the pump after the impeller.
The housing is usally a cast or machined piece of metal that has attached, at the intake and discharge, flanges that can be used to attach it to piping. The housing may be bolted to the motor, this may allow for it removal to service the internal and allow access to the impeller.
The diffuser is a geometry within the volute that slows down the fluid prior to exiting the pump. The impeller is the main rotating part that induces the fluid flow. Flow usually enters the impeller axially and is discharged at a right angle to this. These impellers usualy have a series of vanes help to induce the fluid motion, said vanes can be either exposed, open impellers or shrouded, enclosed impellers, if it is only enclosed on one side it is a hub impeller or partially open.
With enclosed impellers there is a wear ring, used to reduce internal leakage are attached to either the volute, the impeller or both. They are used to ensure proper clearance between the impeller and the volute, tighter clearances means better pump efficiency. Wear plates function in a similar manner with semiopen impellers. Impellers can be fed from one or both sides, most are single suction though.
Seals are used within the pump assembly to ensure that fluids do not escape from the pump, especially from the rotating shaft. Seals can take many forms be it mechnical or packing. Mechnical usually use a mechnism to ensure that tolerances between contact surfaces to do not leak, packing is usually a material that is fitted around areas that may leak. They are then squeezed into a proper fit, many still allowing a fluid to, they do not seal but reduce leakage. For the most part packing is out dated technology.
These pumps can be used in conjunction with other equipment to make them very versatile pieces of process equipment. The can be combined with devices to strain or chop solid upon entry to the pump, they by their vane design be used to handle slurries or abrasive fluids. They can be used in applications that require them to be entirely submerged or can be used to assist with the priming of larger pumps. Some of these pumps can be multi-stage with one stage directing fluid to the intake of another.
