Centrifugal Fans - Types and Benefits

Centrifugal fans are a special type of industrial fans, used in several process industries and air pollution systems. Centrifugal fans are also called as blowers. They are ideal for high-pressure applications, quite different from the other type of fans, known as the axial fans.

How does a Centrifugal fan work?Centrifugal fans increase the pressure of an incoming airstream through a series of blades mounted on a circular hub, which in turn accelerates air radially and changes the direction of the outward flowing air, usually by 90°. These blades are known as impellers. Industrial Centrifugal fans are mostly used in transporting air/gas and material handling.

Centrifugal fans provide various benefits as compared to axial fans.

• Energy efficiency: A Centrifugal fan provides a higher static efficiency of 84 % because of constant airflows and thus ideal for sustaining larger air systems.
• Enhanced durability: As all their moving parts are enclosed as a result their durability is higher and they can operate in corrosive environments.
• Ability to restrict overloading: The designing of the Centrifugal fans allow the ability to fit non-overloading motors. When the load exceeds the specification, the non-overloading motor can accommodate additional load. This non-overloading motor feature adds additional investment and causes some efficiency penalty but helps overcome operational cost and problems.
• Easy to maintain: Because of its lighter material and self -cleaning characteristics these equipment are easy to maintain.
• High versatility: Industrial centrifugal fans can process all types of air such as dry, wet and clean airs and also handle multiple airflow/pressure combinations.
• Multiple sizes: They are available in several sizes to accommodate diverse applications—such as those found in tight spaces or difficult to reach areas.

Types of Centrifugal FansThere are six basic types of centrifugal fans based on the blade configuration. Each type has its own application range and different ability to perform in the industrial processes.

1. Forward Curved Fans

Also known as 'squirrel cage' fans because the wheel type used in this fan is of squirrel cage wheel. The impeller has smaller forward blades. Because of the delicate nature of the impeller, it is used in low speed and low-pressure applications such as in domestic furnaces, central station units, packaged air conditioning.

2. Backward Inclined Fans

These fans offer three standard blade types – flat single thickness, curved single thickness, and curved airfoil. The blades are heavier and larger and used in low pressure, high volume applications such as heating, ventilation and air conditioning systems.

3. Radial Blade Fans

Also known as paddle wheel fans, they produce medium to high pressure and moves relatively a higher mass or volume of fluid. They are well suited for material handling and in some moderate pressure industrial applications.

4. Airfoil Blade Fans

They have hollow backward inclined blades that are suitable to handle large volumes of clean air at low to moderate static pressures. These fans produce optimum efficiency and are suitable for broad operating ranges in industrial applications, HVAC systems, air pollution control, drying & filtration.

5. Radial Tip Fans

They have blades of backward curved configuration but cupped in the direction of the wheel rotation. They have moderate material handling capabilities and are more efficient than radial blade fans. They are used in dust collection systems and general ventilation applications.

6. Inline Centrifugal Fans

They have a rugged construction with backward inclined type wheels enclosed in a tube-axial casing. These are medium duty fans with straight through airflow and are used in low-pressure air system requirements like heating and ventilating.

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