Reciprocating Pumps-working Principle
The reciprocating pump is a hydraulic machine which converts the mechanical energy into hydraulic energy (Pressure energy ) by sucking the liquid into a cylinder in which a piston is reciprocating (moving forward and backward). It is also called a positive pumps, as it discharges a definite quantity of liquid during the displacement of its piston.
Classification of Reciprocating Pumps Reciprocating pumps are classified as follows.
a. According to the action of pump
ii. Double acting pump.
b. According to number of cylinders
- Single cylinder pump
- Double cylinder pump, and
- Multi cylinder pump etc.
Working principle of a single acting reciprocating pump
A reciprocating pump consists of the following parts:
- Cylinder: A cylinder e, in which a piston P works. The movement of the piston is obtained by a connecting rod, which connects the piston and the rotating crank.
- Suction pipe: It connects the source of water (sump well) and the cylinder.
- Delivery pipe: The water sucked from the sump is discharged by the movement of piston through this pipe.
- Suction valve: It admits the flow from the suction pipe into the cylinder.
- Delivery valve: It admits the flow from the cylinder into the delivery pipe.
When crank starts rotating, the piston moves forward and backward in a close fitting cylinder. During the suction stroke, the piston moves forward (ie, from IDC to ODC) and causes vaccum inside the cylinder. This vacuum causes the suction valve to open and the water enters the cylinder. The piston moves towards left (i.e.) from ODC to IDC, thus increasing the pressure in the cylinder. This increase in pressure causes the suction valve to close and delivery valve to open. Therefore, the water is forced into the delivery pipe.
Working principle of a Double Acting Pump
In a double acting reciprocating pump, the water is acting on both sides of the piston. Thus it requires two suction pipes and two delivery pipes. The discharge of this type is to be than that of single acting pump. This is due to the reason that, in a double acting pump, the water is sucked on one side of the piston and delivered from the other side during the same stroke. These two processes (i.e. suction on one side and delivery on the other side) are reversed during the return stroke. Thus for one complete revolution of the crank there are two delivery strokes. Therefore, the continues dis charge is obtained.
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