In this article, you will learn about the Reciprocating pump, its Definition, Main Parts, Types, working principle, and the difference between reciprocating and centrifugal pumps.
What is Reciprocating Pump?
A reciprocating pump is a device that converts mechanical energy into hydraulic energy by sucking the liquid into a cylinder. In this pump, a piston reciprocates, which uses thrust on the liquid and increases its hydraulic energy.
A reciprocating pump is also known a called a positive displacement pump. Because it discharges a definite quantity of liquid. It is often used where a small quantity of liquid is to be handled and where delivery pressure is quite significant.
Parts of Reciprocating Pump
The following are the main parts of the reciprocating pump.
- Suction Pipe
- Delivery Pipe
- Suction valve
- Delivery valve
- Piston and piston rod
- Crank and connecting rod
- Air vessels
In the cylinder, the piston is moving to and fro. The moment of the piston obtains by a connecting rod, which connects the piston and crank.
#2 Suction Pipe
It is the source of water that connects the cylinder together. The suction pipe allows the water to flow in the cylinder.
#3 Delivery Pipe
After the process, the source of water leaves the cylinder and discharges through the delivery pipe. The delivery pipe joins the pump cylinder to the discharge outlet.
#4 Suction Valve
In this valve, the flow of water enters from the suction pipe into the cylinder. It allows only one-directional flow. Hence it is also known as a non-return valve. This valve is found on the suction pipe inlet.
#5 Delivery Valve
With this valve, the flow of water is discharged from the cylinder into the delivery pipe. It is also a non-return valve located between the delivery pipe outlets. The valve is in the closed position during suction.
#6 Piston and Piston Rod
It is a solid part that acts back and forth inside the cylinder for the suction and delivery of the liquid. Whereas the piston rod helps the piston to move in a linear direction.
#7 Crank and Connecting Rod
A crank is a circular disc that is connected to a motor. While the connecting rod connects the crank to the piston. As a result, the rotational motion of the crank is converted into linear movement of the piston.
A strainer is an essential part of the pump that is located at the end of the suction pipe. This helps in preventing the entry of solids from the water source into the cylinders.
#9 Air Vessels
It is a closed chamber made up of cast iron. It has two ends. One ends is open at its base through which the water flows into the vessel cylinder. The air vessels are fitted to the suction pipe and delivery pipe of this pump to get a uniform discharge.
Functions of Air Vessels
- The air vessels use to get the continuous flow of water at a uniform rate.
- To reduce the amount of work in overcoming the frictional resistance in the suction pipe and delivery pipe.
- To run the pump at high speed with separation.
Types of Reciprocating Pump
Following are the two different working principles:
- Single-acting reciprocating pump and
- A double-acting reciprocating pump.
1. Single Acting Reciprocating Pump
In this pump, A cylinder, in which a piston moves forward and backward. The piston is reciprocating by means of the connecting rod. The connecting rod connects the piston and the rotating crank. The crank is rotating by means of an electric motor.
The suction and delivery pipes with suction and delivery valve are arranged to the cylinder.
- The suction valve allows the water to the cylinder and
- The delivery valve leaves the water from the cylinder.
As the crank rotates, during the first stroke of the piston (called suction stroke), the water enters into the cylinder. In a suction stroke, the crank is rotating from A to C (from 0° to 180°) the piston is moving towards the right side of the cylinder. Due to this, the vacuum creates in the cylinder. This vacuum causes the suction valve to open and the water enters the cylinder.
In the next stroke called delivery stroke, the water leaves the cylinder. In the delivery stroke, the crank is rotating from C to A (from 180° to 360°) the piston is moving to the left side of the cylinder. Due to this, the pressure of the liquid increases inside the cylinder. This pressure causes the suction valve to close and delivery valve to open. Then the water is forced into the delivery pipe and raised to a required height.
2. Double Acting Reciprocating Pump
In this, the water is acting on both sides of the piston as shown in the figure.
Thus two suction pipes and two delivery pipes are required for a double-acting pump. When there is a suction stroke on one side of the piston, at the same time there is a delivery stroke on the other side of the piston.
Hence for one complete revolution of the crank, there is two delivery stroke and the water is delivered to the pipes by the pump during these two delivery strokes.
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Working of Reciprocating Pump
When the crank connects to the power source (motor), it will start rotating, and the connecting rod and the crank will also be in movement. As the piston is attached to the connecting rod, it will also start moving in a linear direction.
When the crank is moved outwards, the piston moves to its right, creating a vacuum in the cylinder. This causes the suction valve to open. Now, the liquid from the source is sucked into the cylinder by the suction pipe.
Similarly, when the crank moves inwards of the cylinder, the piston will move to its left, compressing the liquid in the cylinder. At this point, pressure is generated, causing the delivery valve to open, and the liquid flows through the delivery pipe.
Finally, the piston reaches its extreme left position, and all the liquid in the cylinder is delivered through the delivery valve. Again, the crank spins outwards, and the piston moves to the right to create suction, and the process is repeated.
Watch the video below to learn how the reciprocating pump operates:
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Types of Reciprocating Pump
The following are the types of reciprocating pumps according to the source of work and mechanism.
Simplehand-operated reciprocating pump Power-operateddeep well reciprocating pump
- Single-acting reciprocating pump
- Double-acting reciprocating pump
- Triple-acting reciprocating pump
- Pump with air vessels
- Pump without air vessels
Difference Between Centrifugal Pump and Reciprocating Pump
|This pump is simple in construction due to less number of parts.
|This pump is complicated in construction due to more number of parts.
|Centrifugal pump has more weight for a given discharge.
|The reciprocating pump has less weight for a given discharge.
|It is suitable for large discharge with small heads.
|It is suitable for large discharges with small heads.
|It requires more floor space and it has a heavy foundation.
|It requires less space and it has a simple foundation.
|This pump has less wear and tear and it can handle dirty water.
|This pump has more wear and tear and it cannot handle dirty water.
|Its delivery is continuous and needs priming.
|Its delivery is pulsating and no needs priming.
|Centrifugal pump has low efficiency and it can run at higher speeds.
|Reciprocating pump has high efficiency and it cannot run at higher speeds.
|It cannot require air vessels and operation is quite.
|It cannot require air vessels and operation is quiet.
|The maintenance cost of the pump is less.
|The maintenance cost of the pump is high.
|In this pump, thrust on the crank is uniform.
|In this pump, the thrust on the crank is uniform.
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Application of Reciprocating Pumps
- The reciprocating pump is used in oil drilling operations.
- It is helpful in pneumatic pressure systems.
- Primarily used in light oil pumping.
- It is used for feeding small boilers condensate return.
Advantages and Disadvantages of Reciprocating Pump
Following are the advantages and disadvantages of reciprocating pump:
- These pumps can maintain a constant discharge rate while precisely delivering the desired flow rate.
- In addition, reciprocating pumps can deliver fluids at high pressures without the need for priming.
- These pumps have a very high capital expense. Also, these pumps have a low flow rate.
- A reciprocating pump has a higher efficiency than a centrifugal pump by at least 10% to 20%.
- Since there are so many parts involved in reciprocating pumps, they cannot pump viscous liquids, and their maintenance costs are very high.
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Frequently Asked Questions
The act of reciprocating itself is referred to as reciprocating action. It means to take an action in response to one particular action that is similar to or identical to the earlier action.
When a precise amount of fluid needs to be delivered, reciprocating pumps are used. Likewise, the pumps are used when the required delivery pressure is greater than what can be obtained using other types.
Both have advantages, with centrifugal being the less expensive option and reciprocating being the more complicated option. However, which one is better depends on the type of area in which they will be working.
Reciprocating pump designs can handle a wide range of liquid properties, including low-viscosity chemicals, slurries with high particle content, and high-viscosity liquids. Due to their wide operating range, they tend to be the technology of choice for challenging applications.
Many installations of reciprocating pumps experience issues that can result in high maintenance costs and unstable performance. Examples of this include noise and vibration in the pump and piping. Vibration can cause parts like valves, crossheads, crankshafts, piping, and even pump barrels to fail and perform poorly.