Short Answer:

Reciprocating pumps are mainly divided into two types — single-acting and double-acting pumps. In a single-acting reciprocating pump, water is delivered only during one stroke of the piston, while in a double-acting pump, water is discharged during both strokes. These pumps are also classified based on their construction and use, such as plunger pumps, piston pumps, and diaphragm pumps.

Each type of reciprocating pump has a specific design and application. For example, single-acting pumps are used for low discharge and high pressure, while double-acting pumps are used where continuous discharge and higher efficiency are required.

Detailed Explanation :

Types of Reciprocating Pumps

A reciprocating pump is a positive displacement pump that uses the back-and-forth movement of a piston or plunger to transfer fluid. Depending on the working mechanism, discharge characteristics, and construction, reciprocating pumps are classified into different types. Each type has unique advantages and is selected according to the pressure and discharge requirements of the system.

1. Based on Action of Piston

Reciprocating pumps are mainly divided into two types according to how the piston acts during each stroke.

(a) Single-Acting Reciprocating Pump

In a single-acting reciprocating pump, the liquid is in contact with only one side of the piston. The suction and delivery of water take place during alternate strokes.

• Suction Stroke: When the piston moves backward, a vacuum is created inside the cylinder. This causes the suction valve to open, allowing liquid to enter the cylinder.
• Delivery Stroke: When the piston moves forward, the suction valve closes and the delivery valve opens, forcing the liquid out through the delivery pipe.

Thus, the water is discharged only during one stroke of the piston, making the flow intermittent and pulsating.
Example: Hand pumps and small water supply pumps.

Advantages:

• Simple design and easy maintenance.
• Suitable for small discharge and high-pressure applications.

Disadvantages:

• Flow is not continuous.
• More wear and tear due to frequent starting and stopping of the flow.

(b) Double-Acting Reciprocating Pump

In a double-acting pump, both sides of the piston are used for suction and delivery of the liquid. When one side of the piston performs suction, the other side performs discharge simultaneously.

• During one stroke, one side of the piston draws water into the cylinder, and the other side pushes water out.
• During the next stroke, their roles are reversed.

This means water is discharged during both strokes, which gives a more uniform and continuous flow.
Example: High-pressure industrial water pumps.

Advantages:

• Continuous and smoother discharge.
• Higher efficiency compared to single-acting pumps.

Disadvantages:

• Construction and maintenance are more complex.
• Requires precise alignment and sealing to prevent leakage.

2. Based on Construction

Reciprocating pumps can also be divided according to the construction and the type of moving part used inside the cylinder. These include:

(a) Piston Type Pump

In this pump, a piston moves back and forth inside a smooth cylinder. Sealing rings (piston rings) prevent leakage of liquid. This type is commonly used for moderate pressure and flow applications.
Examples: Domestic water supply systems and oil pumps.

(b) Plunger Type Pump

Here, a plunger or ram moves inside a stationary cylinder. The plunger has a smooth surface and is smaller in diameter, which helps develop very high pressure. It is mostly used for high-pressure operations such as hydraulic systems and oil drilling equipment.
Examples: Hydraulic press feed pumps and pressure testing pumps.

(c) Diaphragm Type Pump

In this type, a flexible diaphragm moves back and forth, creating suction and discharge. The liquid does not come into direct contact with moving parts, which makes it suitable for handling corrosive, dirty, or chemical fluids.
Examples: Chemical dosing pumps, slurry handling, and wastewater systems.

3. Based on Number of Cylinders

Reciprocating pumps are also classified depending on the number of cylinders used:

• Single Cylinder Pump: Has only one cylinder and provides intermittent flow.
• Double Cylinder Pump: Has two cylinders operating 180° out of phase to produce smoother flow.
• Triple Cylinder Pump: Has three cylinders placed 120° apart, giving nearly constant discharge and very little pulsation.

These multi-cylinder arrangements are used when uniform flow and high discharge are required.

4. Based on Discharge

According to discharge characteristics, reciprocating pumps are classified as:

• Low Discharge Pumps: Used for small water supply applications like domestic use or small machinery.
• High Discharge Pumps: Used in industrial or irrigation systems where a large quantity of fluid is needed at high pressure.

Conclusion

Reciprocating pumps are versatile positive displacement machines available in various types, each serving a specific purpose. The major types include single-acting and double-acting pumps based on piston action, and piston, plunger, and diaphragm types based on construction. Single-acting pumps are best for simple, small-scale use, while double-acting and plunger pumps are ideal for industrial and high-pressure applications. Selecting the correct type of reciprocating pump ensures efficient, safe, and reliable fluid transfer for any mechanical system.