Reciprocating Pump: Working Principle, Types, Components, and Applications

Q: Who Invented Reciprocating Pump?

Greek discoverer Ctesibius invented the reciprocating pump in 200 BC .

A pump is a device used to transfer different fluids from one location to another. Pumps have multiple types according to different applications. A reciprocating pump is a famous type of pump from the category of positi ve displacement pumps. This article deeply explains the reciprocating pump working, types, components, and applications.

What is a Reciprocating Pump?

A reciprocating pump is a type of positive displacement pump that uses a reciprocating component (i.e., plunger or piston) to pump the fluid from one area to another. The reciprocating piston or plunger converts the mechanical energy of the fluid into pressure energy.

In this pump, the reciprocating piston or plunger reciprocates in an upward and downward position inside the pump cylinder. As the piston moves toward the bottom dead center (BDC), it sucks fluid. The piston compresses the fluid when it moves toward the top dead center (TDC).

A hand pump is a most common example of a reciprocating pump. A bicycle pump and syringe pump are also the most commonly used examples of reciprocating pumps.

The reciprocating pump pumps the fluid through the downward and upward motion of the piston. In contrast, dynamic pumps use an impeller and diffuser to pump the fluid from low-head areas to high-head areas.

The reciprocating pumps highly depend on their reciprocating component (i.e., piston, plunger, or diaphragm). If the reciprocating piston or plunger is damaged then pumps will be unable to efficiently pump the fluids.

Reciprocating pumps are usually used for applications where low flow rates and high pressure are needed, such as in water treatment, chemical processing, and oil and gas production. These types of pumps have the capability to control an extensive range of fluids, from liquids to slurries and gases. Therefore, they are famous because of their high reliability and efficiency.

Reciprocating Pump Working Principle

The reciprocating pump works on the positive displacement principle. A reciprocating piston pump contains a piston or plunger that moves back and forth in the pump chamber.

The piston is connected to a crankshaft with the help of a connecting rod. This piston moves according to the movement of the connecting rod move. The connecting rod gets power from the crankshaft. The crankshaft is connected to an electric motor.

The pump cylinder is connected to a suction pipe and a discharge pipe with an inlet valve and an outlet valve. The inlet and outlet valves act as check valves that allow the fluid flow to flow in one direction. The fluid sucks into the cylinder through the inlet valve. The fluid exits the cylinder of the pump through the outlet valve.

A reciprocating pump works in the following way:

As you can see in the above diagram, when the crankshaft is at position A, the piston has a far-left position inside the cylinder. As the crankshaft rotates from A to C (θ = 0° to 180°), the piston in the cylinder moves to the extreme right side.

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

Due to the cylinder inner and sump pressure difference, the pump sucks fluid from the sump into the suction pipe.

The fluid opens the inlet valve of the pump and starts entering the cylinder. As the suction process completes, the crankshaft rotates from C to A (θ = 180° to θ = 360°), and the piston also moves from the right position of the cylinder to the left position.

When the piston inside the cylinder moves to the left, it reduces the cylinder volume. Due to this reason, the cylinder’s internal fluid pressure becomes higher than the atmospheric pressure.

As the piston pressurizes fluid and the cylinder’s inner pressure becomes higher than the atmospheric pressure, the discharge valve opens, and fluid is delivered to the desired location or storage tank.

Do you know: How does a Centrifugal Pump Work?

Components of Reciprocating Pump

The reciprocating or piston pump has the following parts:

Section Valve
Delivery Valve
Suction Pipe
Delivery Pipe
Cylinder
Connecting rod
Crank
Piston and piston rod
Air Vessel
Strainer

1) Suction Valve

The suction valve is one of the most important components of the reciprocating pump. It is a one-way valve. Therefore, this valve allows the fluid to flow only in one direction. The suction valve is located in between the cylinder and the suction pipe.

When the fluid is discharged from the pump chamber, its pressure becomes lower than the external pressure, and a vacuum produces on the suction side. This vacuum forces the suction valve to be opened. When the suction valve is opened, the fluid enters from the external source to the pump cylinder.

2) Suction Pipe

The suction pipe is utilized to introduce water from the storage tank to the pump cylinder. This part of the reciprocating pump connects the inlet valve with the reservoir or water tank.

3) Pressure Valve

The discharge valve is one of the major parts of the reciprocating pump. It is also a one-way valve. This valve makes a connection between the delivery pipe and the cylinder.

During the suction process, this valve closes while it opens during the delivery process of the fluid. It is used to discharge the fluid from the pump cylinder to the storage tank.

4) Delivery Pipe

A delivery pipe is utilized to deliver fluids from the pump cylinder to the desired height or position. It is directly attached to the delivery valve or discharge valve of the pump.

5) Cylinder

The pump cylinder is usually made of cast iron or Alloy steel. The piston rod and piston are installed in the cylinder. The inlet valve is connected to one side of the cylinder while the discharge valve is attached to the other side of the cylinder.

The reciprocating component (diaphragm, piston, or plunger) reciprocates inside the cylinder to compress the fluid.

6) Piston and Piston Rod

The piston and piston rod include are the major components of the reciprocating pump. A piston is a solid metal part. It moves back and forth inside the cylinder to suck and compress the fluid.

When the piston moves backward, it sucks liquid inside the pump cylinder, and when it moves forward, it pressurizes the fluid and discharges it. The piston is attached to the crankshaft via a connecting rod. The crankshaft drives the piston.

7) Crankshaft

The crankshaft is a rotating of the reciprocating pump. It is made of solid metal. It is a solid disc that is attached to the piston through the connecting rod. The crankshaft is directly attached to an electrical motor or engine. When the electric motor turns on, it rotates the crankshaft, which further reciprocates the piston or plunger.

Read More: Crankshaft Working and Parts

8) Connecting Rod

The connecting rod links the piston and the crankshaft. This part of the pump is used to transfer the crankshaft motion to the piston.
One end of the connecting rod is attached to the piston, while the other end is connected to the crankshaft. It moves according to the motion of the crankshaft. It transforms the linear motion of the crankshaft into the reciprocating motion of the piston.

Read More: Working of Connecting rod

9) Strainer

The strainer is a filter. It separates the solid particles from the fluid and stops the solids from entering the pump cylinder. Otherwise, solid particles may block the inlet and discharge valves.

10) Air Vessel

The air vessel is one of the most vital components of the reciprocating pump. The main purpose of the air vessel is to lessen the pulsations in the fluid flow, which is produced due to the reciprocating motion of the plunger or piston. The air vessel is also called a surge tank or air chamber.

When the plunger or piston travels forward, it forces the liquid into the pipelines and produces a pressure wave.

As the plunger or piston travels backward, it produces a vacuum in the pipelines and introduces the fluid into the pump cylinder. This process generates a pulsating fluid flow that may lead to pipeline vibration and pressure variations.

Therefore, the air vessel is used in the reciprocating pumps to remove the pulsations from the fluid flow by feeding a cushion of compressed air.

When the pressure wave from the piston comes into the air vessel, it compresses the air within the vessel, which then swells and forces the liquid back into the pipeline during the suction stroke. This process assists in ensuring a smooth flow of fluid and decreasing pressure variations in the pipelines.

The air vessel also plays a vital role in increasing the pump performance by lowering the amount of energy needed to pump the liquid.

Read also: Centrifugal Pump Working and Types

Types of Reciprocating Pumps

The reciprocating pump has the following major types:

Single-stage pump
Multi-stage pump
Single acting pump
Double acting pump
Reciprocating pump with air vessel
Plunger pump
Piston pump
Diaphragm pump

1) Single-Stage Pump

In this type of reciprocating pump, only one cylinder uses for pressurizing the water. These pumps have less efficiency than two-stage pumps. But these have low prices and require less maintenance than two-stage pumps.

2) Two-Stage Pump

The name of this pump represents that it uses two cylinders for pressurizing the water. First of all, it sucks water or other fluid in the 1st cylinder where the piston increases its pressure after that it sents into the 2nd cylinder.

In the 2nd cylinder, another piston increases the pressure of the fluid. After this, the fluid pumps to the desired area.

3) Single Acting Reciprocating Pump

In the single-acting reciprocating pump, only one side of the piston works while the other side is fixed. Only one side of the piston uses for suction and delivery purpose.

In simple words, the first stroke of the piston sucks the water inside the cylinder while the second stroke converts the kinetic energy of the water into pressure energy and increases its pressure.

4) Double Acting Reciprocating Pump

In the double-acting reciprocating pumps, both sides of the piston work. In simple words, when the piston moves backward, it sucks the liquid while it moves forwards, then it reduces the volume of the fluid and pressurizes it.

5) Reciprocating Pump with Air Vessel

A reciprocating pump with an air vessel pump has a closed chamber that contains fluid in the bottom section and air in the top section of the chamber. This chamber has an opening on the bottom from where the fluid can move in or out of the vessel. In addition, this vessel has an inlet and outlet valve from where the air enters and discharges from the vessel.

6) Piston Pump

The piston pump is one of the most famous types of reciprocating pumps. This pump uses a piston to pump fluid instead of a plunger. In this pump, the piston moves forward and backward to pump the fluid. These pumps are usually used to pump the fluids in high-head areas.

7) Diaphragm Pump

A diaphragm pump is a positive displacement pump that utilizes a Teflon, thermoplastic, or rubber diaphragm or membrane. A diaphragm is surrounded by valves. This pump is also known as a membrane pump. It works by temporarily generating a vacuum.

Read More: Diaphragm Pump Working and Types

8) Plunger Pump

These reciprocating pumps use a plunger instead of a piston. In these pumps, the movement of the piston is the same as the piston. A plunger pump is best for applications to pump chemicals, saltwater, and oil.

These pumps have low weight and low density. They need low maintenance. They have high durability. Plunger pumps are most commonly used in the beverage, food, petrochemical, gas, oil, nuclear, mining, and medical industries.

These have high resistance to impact, thermal shock, vibration, and abrasion. The plunger pump has a compact design and it has easy maintenance.

How to Calculate Efficiency of Reciprocating Pump?

The efficiency of a pump is the ratio between the outpower and input power. The following formula can calculate the reciprocating pump efficiency:

Efficiency = output power/input power

In the above-given equation, the output power can be calculated by multiplying the fluid flow with the rise of pressure. While the input power can be calculated by multiplying the torque to speed.

Use the below-given formulas for calculating the input power and output power:

Out Power = Pressure Rise * Flow

Input Power = Torque * Speed

Volumetric efficiency and mechanical efficiency are also a kind of pump efficiency.

Mechanical efficiency is related to pressure and torque. The mechanical efficiency of your pump tells how much a pump converts input torque into output pressure.

The volumetric efficiency is related to speed and flow rate. A volumetric efficiency tells how well a pump converts inlet velocity to outlet flow.

Therefore, the overall efficiency of a reciprocating pump is equal to the product of the volumetric efficiency and the mechanical efficiency.

By using the below-given equations, you can easily calculate the flow (Q), Torque (T), Shaft Power, and Hydraulic Power of your pump:

In the above equations, the shaft power represents input power while the hydraulic power represents output power.

Advantages and Disadvantages of Reciprocating Pump

The reciprocating pump has the following advantages and disadvantages:

Advantages of Reciprocating Pumps

This type of pump uses for providing a high suction head.
Reciprocating pumps don’t need a priming process like a Centrifugal pump.
They can handle a wide range of fluids, including viscous liquids and fluids with solids in suspension.
The reciprocating pump delivers a constant flow rate.
It doesn’t have priming issues.
Reciprocating pumps have the capability to control high-viscosity, high-pressure liquids.
They are easy to repair and maintain.
These pumps don’t have cavitation issues.
They have high efficiency due to their positive displacement nature.

Disadvantages of Reciprocating Pumps

These pumps require regular maintenance.
Most of its parts have high wear and tear.
It has a low flow rate.
It has a high cost.
These are heavy pumps.
It doesn’t provide uniform torque.
It requires a high maintenance cost.
A reciprocating pump consumes a lot of energy, especially when working at high flow rates and pressures.

Applications of Reciprocating Pumps

Reciprocating pumps are most commonly used for various commercial and industrial applications where a constant flow of fluid is needed. The reciprocating pumps are most commonly used for the following applications:

Oil and Gas Industry: Reciprocating pumps are most commonly used in the oil and gas industries to pump oil and gases, including pumping natural gas and crude oil and oil injection and stimulation.
Mining Industries: They are used in the mining industries to pump mine dewatering and slurries.
Water Treatment: The reciprocating pump is used in water treatment systems to supply disinfectants and chemicals and regulate pH levels.
Chemical Processing: They are employed in the chemical processing industries to transfer acids, chemicals, and other harmful liquids.
Agriculture Field: They are utilized in the agriculture field to spray fertilizers, herbicides, and pesticides.
Pharmaceutical Industry: Reciprocating pumps are employed in the pharmaceutical industries to pump medicines such as creams and medicines liquids.
Food and Beverage Industries: They use in the food and beverage industries to pump high viscous fluids such as dairy products, syrup, and honey.
Power Generation: They are employed in power plants to circulate water throughout the cooling tower and to supply water to the boiler.

The reciprocating pumps are most commonly used in different industries because of their capability to control high-viscosity, high-pressure liquids. They also supply a constant flow rate.

FAQ Section

Who Invented Reciprocating Pump?

Greek discoverer Ctesibius invented the reciprocating pump in 200 BC.

What are the types of Reciprocating Pumps?