INTRODUCTION: -
When a certain mass of liquid is made to rotate by an external source, it is thrown away from the centrifugal axis of rotation and a centrifugal head is impressed which enables it to rise to a higher level. If more liquid is made available at the center of rotation a continuous supply of liquid passes through revolving wheel of impeller. Its angular velocity changes which also results in increasing the pressure of liquid. Centrifugal pump has wide range of head and discharge. Centrifugal Pumps can be used for viscous and non-viscous liquids. Centrifugal Pump has higher efficiency.
CONSTRUCTION: -
The Main Parts of Centrifugal Pump are:
1. IMPELLER
It is a wheel or rotor which is provided with a series of backward curved blades or vanes. It is mounded on the shaft which is coupled to an external source of energy which imparts the liquid energy to the impeller there by making it to rotate.
They are classified as;
1. Shrounded impeller
2. Semi open impeller
2. CASINGS
It is a pipe which is connected at the upper end to the inlet of the pump to the centre of impeller which is commonly known as eye. The double end reaction pump consists of two suction pipe connected to the eye from both sides. The lower end dips into liquid in to lift. The lower end is fitted in to foot valve and strainer.
3. DELIVERY PIPE
It is a pipe which is connected at its lower end to the out let of the pump and it delivers the liquid to the required height. Near the outlet of the pump on the delivery pipe, a valve is provided which controls the flow from the pump into delivery pipe.
WORKING: -
The first step in the operation of a centrifugal pump is priming. Priming is the operation in which suction pipe casing of the pump and the position of fluid with the liquid which is to be pumped so that all the air from the position of pump is driven out and no air is left. The necessity of priming of a centrifugal pump is due to the fact that the pressure generated at the centrifugal pump impeller is directly proportional to density of fluid that is in contact with it. After the pump is primed the delivery valve is still kept closed and electric motor is started to rotate the impeller. The delivery valve is kept closed in order to reduce valve is opened the liquid is made to flow in an outward radial direction there by vanes of impeller at the outer circumference with high velocity at outer circumference due to centrifugal action vacuum is created. This cause liquid from sump to rush through suction pipe to eye of impeller thereby replacing long discharge from center circumference of the impeller is utilized in lifting liquid to required height through delivery pipe.
