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Reciprocating Pump Working

Reciprocating Pump Definition:

The reciprocating pump is a positive displacement pump works on the principle of a reversing piston motion within a cylinder. During suction stroke, it sucks liquid and during discharge or return stroke, delivers liquid under pressure. One way valve installed on both suction and delivery side to perform pump operation. The discharge of liquid pumped through the reciprocating pump depends on the swept volume and the speed of the pump.

Reciprocating Pump Working Principle:

The reciprocating pump consists of a piston, cylinder, connecting rod, crank and a drive mechanism. Connecting rod converts crank rotational motion into the piston to and fro motion (reciprocating motion).  After crank connected with the piston, piston rotates at the uniform speed through a driving mechanism (motor or engine). When crank rotates from 00 to 1800, the piston moves from extreme left position to extreme right position. This movement of the piston creates a vacuum in the cylinder. This vacuum enables the liquid in the sump to move up through forcing open the suction valve and fill the cylinder. With crank movement by 1800, suction stroke completed. After suction stroke completion, suction valve closed.

Reciprocating Pump
Reciprocating Pump Working

When the crank further rotates from 1800 to 3600 piston moves inward from its extreme right position to extreme left position. This movement of piston pushes the liquid and opens the delivery valve. At the time of delivery valve opening, the suction valve remains closed. This piston movement with the discharge valve open is called discharge stroke.  At the end of the delivery stroke, both suction and delivery valves remain closed. The same cycle repeats and reciprocating pump deliver the required liquid.

In a double acting reciprocating pump, suction takes place on one side of the piston and other side delivery the liquid. Therefore, in one complete rotation of the crank, two suction strokes and two delivery strokes take place.

Types of Reciprocating Pump:

Three types of reciprocating pumps are available.

  1. Piston pump
  2. Plunger pump
  3. Diaphragm pump

1. Piston Pump:

Piston pumps are single or double acting pumps. In a single acting piston pump, during suction stroke pump sucked liquid and during the return stroke, the pump delivers the liquid. The well-pump, cycle pump, and football pumps are single acting piston pumps. In double-acting pumps, each side of the piston compresses the liquid. Fluid is in contact with both sides of the piston. They can be horizontal or vertical. According to the number of cylinders in the pump, these pumps mentioned as simplex (one cylinder), duplex (two cylinders), and triplex (three cylinders) and so on. Sealing of pistons accomplished by piston rings carried by the piston.

2. Plunger Pump:

Plunger pumps are single-acting pumps. These pumps have higher pressures than piston pumps. The plunger runs through a stationary seal, generally a stuffing box. They can be vertical or, horizontal and simplex or multiplex. Designs with variable stroke are common. Plunger pumps used for the highest pressures in the industrial applications.

3. Diaphragm Pump:

Diaphragm pumps can be either hydraulically or mechanically operated. In mechanically operated pumps the pumping action, resulting from the deflection of the diaphragm, is accomplished by direct pushing of a cam or a push rod on the diaphragm. In more common fluid operated pumps the deflection of a diaphragm is achieved through the pressurized fluid. This fluid, in turn, is pressurized through a small plunger pump.

The diaphragm pumps are simplex or multiplex design and also have variable stroke arrangements. Diaphragm pumps can be used when zero leakage is required or when contact by the pumped fluid with the plunger and cylinder might be harmful to the pump.

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