What is Centrifugal Pump? [Notes with PDF]

In the last article, I had discussed Reciprocating Pump which is a positive displacement pump. Today, we will study Definitions, Parts, Working principles, Advantages, Disadvantages, and the Application of the Centrifugal Pump.

Note: The PDF you can download at the end of the articles.

What is Pump?

A hydraulic device that converts mechanical energy into hydraulic energy is known as a pump.

The pumps are used for different applications. They are most commonly used in household and industrial applications. The pumps have multiple types, and a centrifugal is one of them.

A centrifugal pump uses centrifugal force to pump water. These pumps are used in fertilizer industries, septic tanks, manufacturing, and many other applications.

This article mainly explains different aspects of centrifugal pumps in detail.

What is a Centrifugal Pump?

The Centrifugal Pump is a hydraulic machine that is used to convert mechanical energy into pressure energy with the help of centrifugal force and that is acting on the fluid. It is used to transfer fluid by converting rotational kinetic energy to hydrodynamic kinematic energy. The rotation of fluid is done by the fan motor inserted into the pump and at a definite RPM (rotation per minute).

Or we can say It is a type of pump that uses a centrifugal force to transform the mechanical power of the water into pressure energy.

Normally, when the centrifugal pump is running, a certain amount of fluid rotates due to external forces, and the pressure level of the rotating fluid increases.

The increase in the head at any point in the revolving fluid is proportional to the square of the fluid tangential velocity at that point.

Due to the large radius of the outlet impeller, the fluid discharges from the impeller outlet with high pressure. If the radius is large, the fluid flow in the pump is radially outward.

This pump works like a reversing device of an inwardly directed radial flow reaction turbine.

This pump has an impeller and a diffuser. The impeller uses to convert the kinetic energy into pressure energy, while the diffuser uses to convert this increased velocity into the pressure energy of the fluid.

The design of the pump provides a simple and affordable solution for most large volume, low-pressure pumping applications that contain low viscosity liquids like diesel, chemicals, solvents, and water.

Centrifugal Pump Working in detail:

A centrifugal pump is a device that transfers water from one place to another by using centrifugal force. A centrifugal pump has an impeller and a diffuser.

Centrifugal Pump

The centrifugal pump requires priming. Priming is a method to fill fluid in the impeller and the suction pipe. This is necessary to start the pump because the pressure produced by the impeller of the pump is proportional to the liquid density.

The impeller is connected with a shaft which further connects with an electric motor or engine. As the motor delivers power to the shaft, it starts rotating. The impeller also rotates with the rotation of the shaft. 

Due to the rotation of the impeller, a cavity generates in the impeller eye. This cavity generates due to the pump’s internal and external pressure differences. Due to this pressure difference, the fluid starts entering the impeller eye.

When the fluid hits the impeller blades, the blades extract energy from the fluid. These blades convert the fluid energy into velocity and increase the fluid velocity.

After passing through the impeller, the high-speed fluid enters the diffuser. This diffuser slows down the fluid and converts its speed into pressure, and increases the fluid pressure.

This increased pressure fluid is transferred to the desired location.

Types of Centrifugal Pumps:

The centrifugal pump has the following major types:

  1. Axial Flow Pump
  2. Radial Flow Pump and
  3. Mixed Flow Pump

Axial flow pump: It is the best suitable pump for low-pressure and high flow applications. It lifts the fluid in a direction parallel to the axis of the impeller, and its mode of operation essentially corresponds to that of a ship’s propeller. In this pump, the fluid enters the pump axially while discharges in the same direction (axially). In this pump, the pressure generates as the fluid strikes the impeller blades.

Radial flow pump: These pumps are best suitable for low flow and high-pressure applications. In this pump, the fluid introduces axially into the pump and discharges radially to the impeller shaft. All pressure is generated by centrifugal force.

Mixed flow pump: It is a combination of the radial flow pump and axial flow pump. These are typically used for medium pressure and medium flow applications. This centrifugal pump pushes the fluid away from the shaft of the pump at more than 90° angle. In these pumps, some part of the pressure generates by the impeller’s lifting pressure, and the remaining part of pressure generates through centrifugal force.

Centrifugal Pump Parts or Construction:

The centrifugal pump has the following major parts:

#1. Impeller

An impeller is the major component of the centrifugal pump. It connects with the electric motor via a shaft. As the motor delivers power to the impeller, it starts rotating and sucks water. It has a series of blades. When the fluid strikes the blades, they convert the fluid energy into velocity.

#2. Casing or Housing:

The housing is a tight passage that is arranged around the impeller. This part of the pump converts the kinetic energy of the fluid released at the impeller outlet into pressure energy before the fluid leaves the housing and enters the supply line. The construction of the pump housing is similar to that of the reaction turbine housing. The casing has the following three main types:

i) Volute Casing:

This is a spiral-shaped casing that is surrounded around the impeller. The area of the volute casing increases gradually.  An increase in the cross-section increases the pressure and reduces the flow rate of the fluid passing by the housing. This casing improves pump efficiency but loses more energy due to the creation of vortices.

ii) Vortex Casing:

It is a circular chamber installed between the pump impeller and housing. This round chamber reduces vortex formation, and energy loss is significantly reduced. The pumps having vortex casing have more efficiencies than the volute casing pumps.

iii) Casing with guide blades:

In this type of casing, the impeller surrounds via multiple blades attached to a ring called a diffuser. Vanes are designed so that impeller water can enter the vanes without stocks. An increase in the area of ​​the vanes reduces the flow via the guide vanes and increases the water pressure.

#3. Suction Pipe:

One end of the suction pump connects with the centrifugal pump while the other end submerges into the sump water.

This pipe has a check valve at its base. This valve works as a one-way valve and permits the water to follow in only one direction.

#4. Delivery Pipe:

The one end of the delivery or discharge pipe connects with the pump outlet, while the other end connects with the area where you want to transfer fluid. As the pump pressurizes the fluid according to the requirements, the fluid is transferred into a delivery pipe from where it further delivers to the desired area.

#5. Diffuser:

Few pumps contain diffusers, a diffuser is the combination of different vanes, The main use of a diffuser is to enhance the efficiency of the pumping system. It increases the area of flowing fluid in the system and converts rotational energy into pressure energy to get the required head of the pump.

What is the Priming in the Centrifugal Pump?

Priming is an important process to starting up the centrifugal pump but the centrifugal pump is not able to pump the bubble formed by air and vapors.

In priming the impeller of the centrifugal pump is fully into the water without any air bubble into the system. This is required when the pump is starting.

It is required for positive displacement when the centrifugal pump is started for the first time. Priming means trapping liquid into the system (casing) to remove clearance volume. Self-priming is also used.

Some of the Method Used for Priming are:

  • Manually
  • With pumping by vacuum
  • With jet pumping
  • By using separator

Centrifugal Pump Uses or Application:

Here I have listed in bullet point following application:

  • The centrifugal pumps are used on construction sites and houses for transferring fluid from one place to other.
  • These types of use in oil and energy industries to pump mud, slurry, and crude oil.
  • They also use in boilers as feed pumps.
  • The centrifugal pump uses in a septic tank.
  • These pumps are used in flood protection, irrigation, gas processing, drainage, municipal industry, and wastewater processing applications.
  • They are employed for food and beverage production, sugar refining, cellulose, Petrochemical, hydrocarbons, and paint applications.
  • They are also used for aerospace, food production, pharmaceutical, chemicals, and manufacturing industries.

Advantages of Centrifugal Pump:

The following advantages include:

  • The centrifugal pump has easy maintenance.
  • These pumps have small in size.
  • They require a low installation area.
  • They have no leakage issues.
  • These pumps have lower capital costs.
  • They provide pulseless flow.
  • They have more reliability than reciprocating pumps.

Disadvantages of Centrifugal Pump:

The following disadvantages are:

  • They have cavitation issues.
  • They require initial priming for operation.
  • These have shaft misalignment problems.
  • The centrifugal pump can’t pump high viscous fluids.

Difference between Centrifugal Pump and Reciprocating Pump:

Reciprocating PumpCentrifugal Pump
It is a positive displacement pump.It is a dynamic pump.
A reciprocating pump uses a piston for pressurizing the fluid.A centrifugal pump uses an impeller and a diffuser for pressuring the fluid.
This pump provides pulsating fluid.It supplies pulsating free fluid.
They don’t have priming issues.They have priming issues.
These are less expensive than centrifugal pumps.They have a high cost.
They are more efficient than centrifugal pumps.The centrifugal pumps have low efficiency.
These are not best suitable for high viscosity fluids.These are best to transfer high viscosity fluids.
They don’t provide continuous discharge of the fluid.They provide a continuous discharge of the fluid.
The reciprocating pump has heavy-weight.The centrifugal pump has light-weight.
They need high maintenance.They require very low maintenance.
These pumps have a complex installation.They have an easy installation.

FAQ:

Who invented the centrifugal pump?

DENIS PAPIN invented the first centrifugal pump.

How does centrifugal pump increase pressure?

A centrifugal pump uses a diffuser to increase the pressure of the fluid. As the fluid enters the pump, it hits the rotating blades of the impeller. These blades increase the fluid speed and send it into the diffuser. The diffuser converts the speed of the fluid into pressure.

How long can a centrifugal pump run dry?

It can run dry up to 45 seconds to 60 seconds

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Reference [External Links]:


This is all about Definition, Construction or Parts, Working Principles, Advantages, Disadvantages, and Application of Centrifugal Pump.

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Amardeep Kumar

Amardeep will share information related to Mechanical Engineering in this platform. He is the author, editor at themechanicalengineering.com

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