What is the working of a reciprocating pump?
The above figure shows a ‘single acting reciprocating pump’,which consists of a piston which moves forwards and backwards in a close fitting cylinder.The movement of the piston is obtained by connecting the piston rod to crank by means of a connecting rod.The crank is rotated by means of an electric motor.Suction and delivery pipes with suction valves or non-return valves,which allow the water to flow in one direction only.Suction valve allows water from suction pipe to the cylinder which delivery valve allows water from cylinder to delivery pipe only.
When crank starts rotating,the piston moves to and fro in the cylinder.When crank is at A.,the piston is at the extreme left position in the cylinder.As the crank is rotating from A to C,(i.e.,from θ=0 degree to θ = 180 degrees),the piston is moving towards right in the cylinder.The movement of the piston towards right creates a partial vacuum in the cylinder.But on the surface of the liquid in the sump atmospheric pressure is acting,which is more than the pressure inside the cylinder.Thus,the liquid os forced in the suction pipe from the sump.This liquid opens the suction valve and enters the cylinder.
When crank is rotating from C to A (i.e.,from θ=180 degrees to θ=360 degrees),the piston from its extreme right position starts moving towards left in the cylinder.The movement of the piston towards left increases the pressure of the liquid inside the cylinder more than atmospheric pressure.Hence suction valve closes and delivery valve opens.The liquid is forced into the delivery pipe and is raised to a required height.
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