Understanding The Centrifugal Pump Operation

In any process plant, the centrifugal pump stands to be one of the simplest pieces of equipment. This pump has its own mechanism like every other form of machinery. Thus, it becomes important to understand the centrifugal pump operation. The purpose of the centrifugal pump is to translate the energy of a prime mover i.e. electrical energy into kinetic energy and then into pressure energy of the liquid that is being pumped.

The entire conversion of energy that takes place in the pump happens because of two main parts i.e. the impeller and the volute, which is also known as the diffuser. The impeller is the part of the pump that rotates and converts the energy of the driver into kinetic energy. For the conversion of this kinetic energy into pressure energy, the volute or the diffuser that is the stationary part comes to aid. Here it would be appropriate to mention that whatever forms of energy are involved in the liquid flow system are expressed in terms of height of liquid that is head.

The liquid reached the impeller, which is the rotating part via a suction nozzle. This impeller has curved blades, which means that the liquid is pushed in a tangential and radial direction. As the impeller rotates, it spins the liquid present in the cavities between the vanes and pushes it outward. The force that pushes the liquid outward is known as the centrifugal force. While the fluid begins to move outward, a low-pressure area is created which further pushes the liquid towards the inlet.

The centrifugal force imparts kinetic energy to the fluid. Now this kinetic energy is directly proportional to the velocity of the impeller at its edge. The higher the velocity of the impeller at its edge or the bigger it is in size, the higher the amount of kinetic energy imparted to the liquid. So if you want the liquid to gain more energy make sure that either the impeller revolves fast or it is large in size.

To utilize this kinetic energhy of the fluid that comes out of the impeller several forms of resistance are created to convert the kinetic energy into pressure. The first resistance comes in the form of the pump volute. This volute catches the liquid and slows it down. As put forth by the Bernouli's principle, the velocity of the liquid is further decreased when it reaches the discharge nozzle and is converted into pressure. Since the energy is being transformed from one form into the another, the kinetic energy of the fluid is approximately equal to the pressure that is created in the end.

Put into simple terms, the centrifugal pump operation is simple and basically works on the principle of transformation of energy. Here in, kinetic energy is translated into pressure energy.