Centrifugal Pump: Ordinary machine with extraordinary features

Since ancient age, humans have been trying to discover a convenient way to lift water to higher levels for household, irrigation and many other purposes. It is believed that the thought of water lifting by centrifugal force was first sparked at the end of 16th century. As years progressed, a continuous advancement in these pumps has lead us to a highly advanced form of this machine which is used in wide array of applications of our daily life, across the world.

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Introduction

Typically, a pump can be defined as a device that lifts water or other fluids from lower to higher level when driven by an external source. Technically, a pump may also be defined as a machine that converts mechanical energy to pressure energy. And the pump which employs centrifugal force to raise water from lower level to higher is known as a centrifugal pump. A centrifugal pump is Roto dynamic in nature and uses a rotating impeller similar to that of a turbine to increase liquid pressure. The impeller is enclosed in a watertight casing and curved vanes are fitted to this impeller. The impeller also has a delivery pipe on one of its sides. The design of the pump's casing converts kinetic energy of the water into pressure energy before water leaves the casing. This in turn considerably increases the efficiency of the pump.

Working

Centrifugal pumps operate by converting the moving force of kinetic energy, which is resultant of electric motor or turbine, to a static liquid pressure. Principle of Bernoulli describes this process well. Once the pump impeller begins to rotate, it imparts kinetic energy to the fluid which is drawn inside the pump from the impeller eye. The fluid is then forced outward to the periphery because of centrifugal force. As the fluid exits the impeller, its kinetic energy is transformed into static pressure as the fluid experiences change in the area in the volute section. The primary reason for the conversion of energy is the volute shape of the pump casing or the vanes. Essentially, the function of the diffuse is to decelerate the fluid and convert kinetic energy into flow work which then results in the increase in the pressure on the downstream side. The entire process causes liquid to flow. The total energy usage of a centrifugal pump for the entire pumping process can be estimated quite easily based on the required flow, the height lifted and length of the pipeline.

Applications

The most common applications of a centrifugal pump include Petrochemical Pumping, Petroleum, water supply and sewage amongst others. A water turbine is the reverse function of the centrifugal pump where in potential energy of water pressure is converted into mechanical rotational energy.

Disadvantages

In spite of the extensive application in household and diverse industrial sectors, centrifugal pumps have some problem with regard to erosion, corrosion, leakage, overheating etc. Hence, they require regular maintenance.

Multistage Centrifugal Pumps

A multistage centrifugal pump is a type of centrifugal pump with two or more impellers. These impellers maybe mounted on the same shaft or different. The impellers can be connected in series at the outlet if higher pressure is required. However, in cases where higher flow is required, impellers can be connected in parallel. A common usage of a multistage centrifugal pump is in the boiler feed-water pump.