How does a Reciprocating Pump work?

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A reciprocating pump is a preferred pump from the category of positive displacement pumps. It is a mechanical device that converts mechanical energy into hydraulic power. In this article, we will also discuss the principle of the reciprocating pump and its various components. Such a positive displacement pump uses the piston to pump fluid from one to another. The reciprocating pump uses the piston for pumping purpose; Hence, it is also known as a piston pump.

The reciprocating pump has a working principle according to the forth and back speed of the piston. In contrast, dynamic pumps use the kinetic energy of the impeller to pump fluid from the lower head area to the higher head areas.

This can be achieved by pulling the fluid into the cylinder with the reciprocating piston. The piston pushes the fluid out and increases the compressive strength of the fluid.

This is a well-known type of pump that has a plunger or piston. The piston pump displays inside the cylinder, where it rotates forward and backwards. Reciprocating pumps are used when moving a relatively small amount of fluid at high pressure. These pumps at high pressure are more suitable for a small flow rate compared to centrifugal pumps. When using a plunger or piston pump, a certain amount of fluid (mainly sump) must be transported from the lowest and highest area.

For example, if you go to service water on a bike, you may see used water collected from the sump and sprayed on the bike by applying pressure through a nozzle.

Working Principle of the Reciprocating Pump

The reciprocating or piston pump contains a piston, which moves back and forth in the cylinder. The piston connects to the crankshaft with the help of a connecting rod. The piston moves as the connecting rod move due to the crankshaft speed. The crankshaft connects it to the rotating motor.

reiprocating pump working

The cylinder connects with the suction pipe and with the discharge pipe to the suction valve and the delivery valve. The inlet and outlet valves act as check valves, allowing fluid to flow in only one direction.

The liquid introduces into the cylinder‌ through the inlet valve. The fluid comes out of the pump’s cylinder through the outlet valve.

As you can see in the picture above, when the crankshaft “A” is in position, the piston is very far inside the cylinder, as the crankshaft rotates from A to C (θ = 0 ° to 180), so the piston moves to the right inside the cylinder.

During the right piston movement, a partial vacuum is created inside the cylinder. However, atmospheric pressure acts on the surface of the fluid in the sump, and this pressure is higher than the pressure in the cylinder.

Therefore, the fluid flows from the sump into the inlet pipe. The fluid opens the inlet valve of the pump and inserts it into the cylinder. As the crank rotates from C to A (180 = 180 ° to 360 = 360), the piston moves from the right position of the cylinder to the left.

As the pump piston inside the cylinder rises to the left, the fluid pressure in the cylinder increases compared to the atmospheric pressure. Therefore, the inlet valve closes, and the discharge valve opens. The fluid enters the delivery pipe and comes to the required head.

Parts of Reciprocating Pump

1) Suction valve

A suction valve is a vital part of a piston pump. In other words, this type of valve allows flow in the same direction. The suction valve inserts between the cylinder and the suction pipe. During the suction process, this valve opens. While during the discharge process, the suction valve closes.

2) Suction pipe

The suction pipe is used to bring water from the storage tank into the pump cylinder. This part of the reciprocating pump connects the inlet valve to the reservoir. It also connects the pump inlet to the water tank.

3) Discharge valve

It is also a one-way valve. This valve makes the connection between the delivery pipe and the cylinder. During the suction process, this valve closes. It opens during the delivery process of the fluid.

4) Delivery pipe

The distribution pipe pumps the fluid from the pump cylinder to the desired height or position. It connects directly to the delivery valve of the cylinder of the piston pump.

5) Cylinder

Cast iron or alloy steel is used to make pump cylinders. The piston and piston rod are mounted in the cylinder. Fluid from the suction valve introduces inside the cylinder. The piston moves the fluid forward inside the cylinder to increase its pressure. The cylinder connects to a discharge valve, from where the fluid is released into the discharge pipe.

6) Piston and piston rod

The piston rod and piston are the most vital parts of a piston pump. The piston is a solid metal part. It moves in and out of the cylinder for suction and expels the fluid. As it travels backwards, it forces fluid inside the cylinder, and when it moves forward, it delivers fluid. The piston moves due to the movement of the crankshaft. The piston rod supports the piston in linear motion.

7) Crank

The crankshaft is an important part of a positive displacement pump. It is a solid disc that connects to the piston by means of a connecting rod. Crank is directly connected to the electric motor. It rotates when the electric motor powers it.

8) Connecting rod

The connecting rod forms the connection between the piston and the crankshaft. This part links the piston to the crankshaft. As the crankshaft rotates, the connecting rod also rotates. It converts linear crankshaft rotation into piston linear motion.

9) Strainer

The suction pipe strainer prevents solid particles from entering the water source inside the cylinder. Otherwise, solid cells will impede delivery.

10) Air vessel

It connects to the inlet and outlet pipes. This component removes friction head needs. Air vessels also provide a constant delivery rate. component d


  1. Reciprocating pumps use for oil drilling applications.
  2. Uses in the servicing water stations for automobiles etc.
  3. Piston pump uses in an oil refinery.
  4. This pump utilizes for light oil pumping.
  5. Utilizes in the Petrochemical industries
  6. It uses in pneumatic systems.
  7. These pumps use in natural gas industries.
  8. For blow up bicycle tyres.
  9. Supply of small boilers with condensate.

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