Pump is a device which plays a very important role in this society. It has a wide range of applications. It can be divided into various types such as positive displacement pumps, buoyancy pump, impulse pumps, velocity pumps, gravity pumps, and steam pumps.
Among all the above mentioned categories of pumps, the velocity pumps can be future divided into centrifugal pumps, radial flow pumps, axial flow pumps, eductor-jet pumps, and mixed flow pumps. The centrifugal pump is one of the simplest pieces of equipment in any process plant. Its purpose is to convert energy of a prime mover first into velocity or kinetic energy and then into pressure energy of a fluid that is being pumped. The energy changes occur by virtue of two main parts of the pump, the impeller and the volute or diffuser. The impeller is the rotating part that converts driver energy into the kinetic energy. The volute or diffuser is the stationary part that converts the kinetic energy into pressure energy.
There are two main components of the centrifugal pumps. Those are a rotating component and a stationary component. The former consists of an impeller and a shaft, while the latter is composed of a casing, casing cover, and bearings.
Let us first see something about the rotating component. The impeller is the main rotating part that provides the centrifugal acceleration to fluid. It is also classified in many ways. For example, it can be classified according to mechanical construction. There is closed type, open type, semi-open or vortex type if classify according to this. The first type of impellers require wear rings and these wear rings present another maintenance problem. And the open and semi-open impellers are less likely to clog, but they may need manual adjustment to the volute or back-plate to get the proper impeller setting and prevent internal re-circulation.
And another important part of rotating component is the shaft. The basic purpose of it is to transmit the torques encountered when starting and during operation while supporting the impeller and other rotating parts. It must do this job with a deflection less than the minimum clearance between the rotating and stationary parts.
Now, let us get down to some parts of the stationary component. Generally, there are two types of casings which are volute and circular. Volute casings build a higher head, and one of its purposes is to help balance the hydraulic pressure on the shaft of the pump. Circular casings are used for low head and high capacity. Except for them, bearings are also very useful components in the centrifugal pumps.
All these various components are very important. They cooperate well with each other to achieve good performance of centrifugal pumps.