## Centrifugal, axial and double stage fans: a tecnical classification

In post “Industrial Fans explained to the laymen/ non insiders”, we have provided a very simplified description of the industrial fans, and we have added an essential classification too. In this post we want to provide a more technical explanation, defining the industrial fans with more specialized terms and classifying them accordingly.

In this situation, we can define the industrial fan (hereinafter: fan) as a turbomachine that receives mechanical energy and then uses it, thanks to a bladed impeller, in order to maintain a continuous flow of air or other gas passing through it, providing a work per unit mass that is not greater than 25 kJ / kg (UNI EN ISO 13349).

There are several ways of classifying industrial fans:

Classification based on the performance of the flow in the impeller:

• Centrifugal fans: in these fans the fluid enters the impeller with axial direction and leaves it in a direction perpendicular to the axis. The double stage is a particular configuration of the centrifugal fans (see the image in evidence) in which two impellers and therefore two different stages of compression are used;
• Axial fans: in these fans the air enters and exits the impeller along surfaces that are cylindrical and coaxial with the same fan.

Classification based on the drive system:

• Belt driven Fan
• Direct driven Fan (directly coupled with the electric motor)
• A particular system is the system with the coupling joint; it typically consists of a female plus a male part. The female part is installed with a plug to the bearing block, differently the male one is installed to the shaft of the electric motor.

Classification based on the maximum pressure delivered:

• Fans with low pressure (maximum pressure delivered: about 300 mmCA)
• Fans with medium pressure (maximum pressure delivered: about 600/700 mmCA)
• Fans with high pressure (maximum pressure delivered: about 2500 mmCA)

## How to choose an industrial fan (part one)

Can’t you figure out how to choose an industrial fan? Here you are some tips.

Check out the four main parameters determining the features of an industrial fan to choose the industrial fan suitable for a specific application.

These four parameters are:

• Flow rate
• Pressure
• Power
• Performance

Let’s see these four parameters in detail, as clearly as possible, using common language.

• Flow rate

The flow rate is the quantity of air passing through an industrial fan over time: in the metric system, it is expressed in cubic meters processed in a second, a minute or an hour. It is the main parameter, as it defines for the field operators “the purpose” for which the industrial fan has been created.

• Pressure

The pressure is the form of energy enabling the fan flow rate to flow into the circuit where the fan is applied. In other terms, think of the pressure of a fan as of the blood pressure, made by the pulse of the heart, to enable the blood flow (the flow rate) to reach all parts of the body.

• Power

After setting the required combination between flow rate (which performs the work) and pressure (which allows the flow rate to do the work), it’s time for the power to apply to the fan. The power is the energy used to drive the impeller, in order to achieve the required combination between flow rate and pressure.

• Performance

As you know, in nature energy can neither be created nor be destroyed but rather transformed. Particularly, not all of the energy delivered to run an industrial fan is transferred to the fan itself:
a part of it is converted into heat due to the friction of the engineering parts (and to other factors) and then dispersed. Thus, the performance is the ratio of the energy that the industrial fan actually transfers to the air mass and the energy dispersed by the energy resource (in our case nearly always an electrical motor).

Interesting, isn’t it? For more details on the parameters defining the industrial fans and their choice, see the part two of this post and the Glossary, both forthcoming.

## The industrial fans explained to non-experts

Industrial fans are machines whose rotating blades are driven by an electrical motor (hence the name “electric fan”). The primary functions of these fans are to provide a continuous large flow of gas, such as clean air or dusty air, and to transport particulate floating in a gas flow, such as wood chips.

These fans may have fan wheels/impellers that range from a few tens of centimeters to several meters, and are typically used both inside of machines, industrial equipment and inside of plants for the industrial fans, for which they are essential parts of.

In terms of construction, most industrial fans can be categorized into one of two general types:

• axial industrial fans: the gas fluid is sucked and moved parallel to the fan wheel’s shaft;
• centrifugal or radial industrial fans: the gas fluid is sucked in the direction of the impeller’s axis and then moved perpendicular to the fan wheel’s shaft

The installers of industrial fan plants are used to categorizing the industrial fans according to their pressure range

In detail, industrial fans can be:

• low-pressure industrial fans (up to about 300 mmWC)
• medium-pressure industrial fans (up to about 600/700 mmWC)
• high-pressure industrial fans (up to about 2500 mmWC)

Finally, just note that there are 4 basic values defining an industrial fan: flow rate, pressure, performance and rotation speed. These four features are critical in selecting an industrial fan; for more details on this topic, see this article from industrial-fans-blowers.com.

## Industrial-fans-blowers.com is born, the first blog dedicated to industrial fans blowers

Industrial-fans-blowers.com is the first blog wholly dedicated to the industrial, commercial and technical aspects of the industrial fans blowers and, more generally, of the world of industrial fans applied to machinery, plants and environments.

Designed by Euroventilatori International Spa, international leading company in the world of industrial fans, Industrial-fans-blowers.com wants to be a valuable resource for students, fitters, designers, engineers, installers and in general, for the entire community of people who perform professional or training activities relating to the world of industrial fans.

Industrial-fans-blowers.com will include informative articles, technical insights, product and field news. Our goal is to share leading and accessible viewpoints on the world of the industrial fans with the community of field experts, as well as to map out considerations, promote the sharing and the spreading of technical information and above all, get the field operators communicate to ease the circulation of ideas … as well as of air flows.