Pumps Reciprocating pump, Centrifugal pump, Jet pump and Gear pump.

Pumps
A device driven mechanically which helps to increase the force of a liquid is called a pump. The main application of a pump is to lift liquid from a lower surface to a higher surface which means that the pump helps the liquid to move against gravitational force.
Working.
The pump lowers the pressure at the inlet and increases the pressure at the outlet this is the main concept of the pumps. Due to the low pressure than the normal pressure the liquid is forced to enter to the low pressure area ie, to the inlet and the high pressure at the outlet pushes the water out from the pump.
Classification on the basis of working principle.
On the basis of working principle the pumps are divided into rotodynamic pumps and reciprocating pumps the reciprocating pumps are often called positive displacement pumps.

• Reciprocating pump.
• Centrifugal pump.
• Jet pump.
• Gear pump.

Reciprocating pump.



The lower pressure at the inlet and higher pressure at the outlet is obtained by the reciprocating motion of the piston inside a closed cylinder . Due to the reciprocating motion of the piston the pump is a positive displacement pump.

Working.
While the piston moves away from the inlet valve in the cylinder it creates a vacuum by lowering the pressure inside the cylinder. While the pressure lowers the liquid from the suction pipe enters to the cylinder . After liquid enters to the cylinder of the pump the inlet valve close and the outlet valve opens the forward motion of the piston pushes the water out to the delivery pipe. The valve restricts the reverse flow of the liquid in the corresponding containers. The movement of piston inside the cylinder is obtained by connecting the piston with a crankshaft. The crank shaft is then connected to an electric motor.



Centrifugal pump.




The low pressure at the inlet and high pressure at the outlet is obtained by the centrifugal force. We can observe that while we are rotating some liquid over a round plate fixed at its centre the liquid at its surface is thrown away from the centre this same principle is used in the centrifugal pump.Rather than the centrifugal force the liquid is passed through a rotating impeller while the angular momentum increases considerably. The centrifugal pump have an impeller which is made up of brass generally to resist rust which have an open circle in the middle of the circle and a number of blades tangential to the eye. The blades help to increase the angular momentum of the liquid that enters through the eye of the impeller. Another important part is the foot valve which prevents the back ward flow of liquid in the suction pipe. There is a covering for the impeller called casing and a delivery tube.

Working.
The priming is very important for the centrifugal pump because the vapor inside the casing and impeller can't create the suction force. It is not enough to lift the water from a lower surface to a higher surface.[priming: the process of removing the air from the casing by filling the liquid is called priming] so after priming, the electric motor will rotate the impeller this will increase the angular velocity of the liquid by throwing it away from the eye of the impeller towards the casing. While the liquid is removed very quickly from the casing it lowers then pressure in the suction pipe and the water from the sump is forced to move in casing . The water after passing through the impeller and casing it pushes to the delivery pipe.

Jet pump



A nozzle and a diffuser are the main part of the jet pump. A stream of liquid in very high velocity is allowed to pass through the nozzle it may be from the delivery pipe or an independent source. While the liquid passes through the nozzle the pressure energy is converted in to kinetic energy and slowly the pressure in the suction pipe gets reduced and the water from the high pressure sump enters to the suction pipe. All the liquid are mixed together in the mixing zone and a pressure variation is developed in the mixing zone . After the mixing zone the liquid is pumped to the delivery pipe with a high velocity.

Gear pump.



Two inter meshing spur gears are the main parts of the gear pump. The gears are connected with a electric motor outside the casing . The gear pumps are very efficient in pumping viscous liquids .The casing is perfectly shaped of the gears inside in it. The liquid enters through the entering pipe and the rotating gear take the liquid away .Due to the meshing of the gears the liquid can't flow back .