Main components of a centrifugal pump
Centrifugal pump has the following main components:
It is a flange to connect the suction pipe with the pump.
It is the pipe on the upstream side of the centrifugal pump and the pressure is negative in this pipe. Diameter of suction pipe is kept larger than the diameter of the delivery pipe to increase the maximum suction. The suction pipe of a centrifugal pump plays an important role in the successful and smooth working of the pump. A poorly designed suction pipe causes insufficient net positive suction head ( NPSH). While laying the pipe, a great care should be taken to make it air tight. A strainer foot-valve is connected at the bottom of the suction pipe to avoid the entry of foreign matter. Since the pressure at the inlet of the pump is suction(i.e., negative) and its value is limited to avoid cavitation. It is therefore essential that losses in the suction pipe should be as small as possible. For this purpose, bends in suction pipe are avoided and its diameter is often kept larger.
Sometimes, to reduce the axial thrust, the suction pipe is branched into two parts. Then liquid is allowed to enter the impeller from both sides. Such a pump is called double suction pump.
It is a flange to connect the delivery pipe with the pump.
A check valve is provided in the delivery pipe near the centrifugal pump. This check valve is provided in order to protect the pump from hammer. Check valve is also used to regulate the discharge from the centrifugal pump. The size and length of the delivery pipe depends upon the requirement.
It is an air tight chamber which accommodates the the rotating impeller and vortex flow is formed in it. At the inlet of casing, pressure is negative. Pressure is positive at outlet of casing.
A rotating wheel having the backward curved vanes, fixed in the casing on a shaft is known as impeller.
Types of impellers
The impeller in which circular plates are on either side of the curved vanes. Shrouded impellers are used for pumping clean water.
The impeller in which circular plate is only on one side of the blade. Un-shrouded impellers are used for pumping muddy water.
Due to the rotation of impeller, suction is produced in the center. This suction will suck the liquid and liquid will flow centrifugally outwards through the vanes. The impeller will increase the energy of the liquid.
It is a rotating rod which transmits mechanical energy from coupling to the impeller.
Coupling is a device which is used to transfer mechanical energy from motor to the centrifugal pump.
Bearing and housing
These are the devices to hold the rotating shaft.
Stuffing box with jute packing
These are the water seals which are provided at the point of contact between the rotating shaft and casing. It’s function is to made the joint water tight.
These are the points from which water enters into the center of impeller.
This is to prime the pump.