What is a Reciprocating pump?
A reciprocating pump is a class of positive-displacement pumps that includes the piston pump, plunger pump, and diaphragm pump. Well-maintained, reciprocating pumps can last for decades. Unmaintained, however, they can succumb to wear and tear.
It is often used where a relatively small quantity of liquid is to be handled and where delivery pressure is quite large. In reciprocating pumps, the chamber that traps the liquid is a stationary cylinder that contains a piston or plunger.
A reciprocating pump is a mechanical device that changes the mechanical energy of the fluid into hydraulic energy (pressure energy). It uses a piston or plunger to pump the fluid from one location to another. Because a reciprocating pump uses a piston or plunger for pumping purposes, therefore, it is also known as a piston pump.
In this pump, the piston reciprocates in an upward and downward position inside the pump cylinder. As the piston moves toward BDC, it sucks fluid while it pressurizes the fluid when it moves toward TDC.
Parts of Reciprocating Pump
The Parts of the Reciprocating Pump are as follows.
- Water Sump
- Strainer
- Suction Pipe
- Suction Valve
- Cylinder
- Piston and Piston rod
- Crank and Connecting rod
- Delivery valve
- Delivery pipe
The explanation for the parts of the Reciprocating pump is as follows.
1. Water Sump
It is the source of water. From the sump, water is to be transported to the delivery pipes by the usage of the piston.
2. Strainer
It acts as a mesh that can screen all the dirt, dust particles, etc. from the sump. If there is no strainer, then the dirt or dust also enters into the cylinder which can jam the region and affects the working of the pump.
3. Suction Pipe
The main function of the suction pipe is to collect the water from the sump and send it to the cylinder via a suction valve. The suction pipe connects the water sump and the cylinder.
4. Suction Valve
It is a non-return valve which means it can take the fluid from the suction pipe and send it to the cylinder but cannot reverse the water back to it. In this sense, the flow is unidirectional.
This valve opens only during the suction of fluid and closes when there is a discharge of fluid to the outside.
5. Cylinder
It is a hollow cylinder made of cast iron or steel alloy and it consists of the arrangement of piston and piston rod.
6. Piston and Piston rod
For suction, the piston moves back inside the cylinder and for discharging of fluid, the piston moves in the forward direction.
The Piston rod helps the piston to move in a linear direction i.e. either the forward or the backward directions.
7. Crank and Connecting rod
For rotation, the crank is connected to the power source like engine, motor, etc. whereas the connecting rod acts as an intermediate between the crank and piston for the conversion of rotary motion into linear motion.
8. Delivery Pipe
The function of the delivery pipe is to deliver the water to the desired location from the cylinder.
9. Delivery valve
Similar to the suction valve, a delivery valve is also a non-return valve. During suction, the delivery valve closes because the suction valve is in opening condition and during Discharge, the suction valve is closed and the delivery valve Is opened to transfer the fluid.
How does a Reciprocating Pump work?
When the power supply is given to the reciprocating pump, the crank rotates through an electric motor.
The angle made by the crank is responsible for the movement of the piston inside the cylinder. By referring to the above diagram, the piston moves towards the extreme left of the cylinder when the crank meets position A i.e. θ=0.
Similarly, the piston moves towards the extreme right of the cylinder when the crank meets position C i.e. θ=180.
A partial vacuum in the cylinder takes place when the piston movement is towards the right extreme position i.e. (θ=0 to θ=180.) and that makes the liquid enter into the suction pipe.
This is due to the presence of atmospheric pressure on the sump liquid which is quite less than the pressure inside the cylinder. Therefore, due to the difference in pressure, the water enters the cylinder through a non-return valve.
The water which stays in the volume of the cylinder has to be sent to the discharge pipe via the discharge valve and this can be done when the crank is rotating from C to A i.e. (θ=180 to θ=360) which moves the piston in the forward direction.
Due to the movement of the piston in a forward direction, the pressure increases inside the cylinder which is greater than the atmospheric pressure.
This results in the opening of the delivery valve and the closing of the suction valve.
Once the water comes into the delivery valve, it cannot move back to the cylinder because it is a unidirectional valve or non-return valve.
From there, it enters into the delivery pipe so that it can be sent to the required position.
Therefore, in this way, the water is sucked and discharged from the sump to the desired location through the piston inside the cylinder.
Advantages of Reciprocating Pump
- Reciprocating pumps can deliver the required flow rate very precisely.
- It gives a continuous rate of discharge.
- It can deliver fluid at very high pressure.
- No priming is needed in the reciprocating pump.
- The efficiency of a reciprocating pump is 10% to 20% greater than the efficiency of a Centrifugal Pump.
Disadvantages of Reciprocating Pump
- The pump is very costly (Capital cost is high).
- Viscous liquids are difficult to pump using a reciprocating pump.
- The maintenance cost of the pump is very high as there is a large number of parts.
- The flow rate is less.
Reciprocating Pump Application
The application of Reciprocating pumps is as follows:
- Vessel, pipe, tank, tube, condensate pipe, heat exchanger, etc. cleaning,
- Oil drilling, refineries, production, disposal, injections.
- Pneumatic pressure applications.
- Vehicle cleaning.
- Sewer line cleaning.
- Wet sandblasting
- Boiler feeding
- High-pressure pumps for the RO system (Reverse osmosis)
- Hydro testing of tanks, vessels, etc.
- Firefighting system.
- Wastewater treatment system.
FAQs
What is a reciprocating pump used for?
Reciprocating pumps are used where a precise amount of fluid is required to be delivered, also where the delivery pressure required is higher than can be achieved with other types. The fluid is moved by the means of a piston that travels in a cylinder.
What is the difference between centrifugal and reciprocating pump?
Unlike centrifugal pumps, which rely on rotation, reciprocating pumps utilise a piston, diaphragm or a plunger to displace the fluid in a controlled manner. This reciprocating action creates a pressure differential that draws in the fluid on one stroke and then pushes it out on the return stroke.
Why is reciprocating pump more efficient?
Generally, a reciprocating pump is more efficient than a centrifugal pump because it operates in low-flow and high-discharge pressure environments.
What are the advantages and disadvantages of reciprocating pumps?
Advantages and disadvantages of reciprocating pumps. The efficiency of a reciprocating pump is at least 10% to 20% greater than that of a centrifugal pump. The capital cost of these pumps is extremely high. Other than that, the flow rate of these pumps is also low.
What is a practical example of a reciprocating pump?
Simple hand-operated reciprocating pump. The simplest example is the bicycle pump, which is used ubiquitously to inflate bicycle tires and various types of sporting balls.
What flow is a reciprocating pump suited for?
The liquid is sucked at the inlet side when the cavity expands and discharges when the cavity decreases. In general, a reciprocating pump has a higher efficiency than a centrifugal pump. Reciprocating pumps operate in low-flow and high discharge pressure environments.