Choosing Fan Design of ID and FD Fans
                     CHOOSING FAN DESIGN OF ID AND FD FANS
Neel Rao
Writes on Forced draft fan, and 
ID Fans and FD Fans from Reitz India
Induced draft (ID) and forced draft (FD) fans are crucial pieces of 
equipment in many industries. These blowers are critical to running 
factories where there are furnaces and boilers. Choosing the 
appropriate ID and FD fan design is an important decision for high 
output and efficiency. The right design of these fans is dependent 
on many key parameters like the required pressure and airflow 
requirements of a manufacturing plant.
A plant or a factory has to carefully analyze these aspects. It is only 
then that a proper decision can be made about the exact blade 
design for the ID and FD fans. Typically, both the ID and FD blowers 
make use of centrifugal fan type due to its many advantages. Based 
on the type of manufacturing plant, there is a variation in the type 
of impellers used.
Choosing the right FD fan design
These are a few key aspects to be considered while choosing the right FD fan design.
FD fans are with airfoil blades or blades that are backward-curved. This particular design 
ensures that the air from the external environment is thrust into a furnace or a boiler. 
The process of combustion gets completed properly.
These types of blades support medium air pressure.
Backward-curved blades enable operational efficiency.
Airfoil blades are preferred when the sound emitted by the fans has to be on the lower 
side.
When the supply of air is relatively clean, both the blade types are equally efficient. 
These blades are extremely useful when the volume of required airflow is high.
Tips for selecting the correct ID fan design
ID fans are primarily used in boilers and industrial furnace systems for creating a 
negative pressure in the combustion chamber, pulling flue gases out of the system, 
and discharging them to the chimney. They are located at the outlet of the 
combustion system or heat exchanger. The negative pressure helps in efficient 
combustion by ensuring the air/fuel mixture is drawn in and exhaust gases are 
removed.
These are a few key aspects to be considered while choosing the correct induced 
draft fan design.
Here, choosing either the backward-curved or the radial versions is the best option.
It is blowers with these designs that can efficiently gather flue gases present within 
the system, and promptly eliminate them into the outside atmosphere.
To achieve the above objective, it’s imperative that the fans create high levels of air 
pressure. Both the radial and backward-curved designs help in generating this air 
pressure.
Blowers with these blade designs will be able to handle hot, corrosive gases found 
inside combustion chambers or furnaces.
Normally, plants choose a radial design when they want the blades to be highly 
robust. This robustness is essential to withstand hot, dusty, and corrosion-causing 
gases. The radial blades withstand such harsh conditions.
Similarly, if the gases are relatively clean, then plants optimize for blades of the 
highest efficiency – in such situations the backward-curved variants are chosen.
Furnaces and combustion chambers are not the only systems where these fans are 
used. Radial and backward-curved ID fans find their usage in kilns, dust collectors, 
and incinerators, too.
Sometimes, we see that these blades have special coatings or wear liners. Obviously, 
these models are more rugged than the regular versions. They are useful in plants or 
factories where the systems are required to handle extremely corrosive and dusty 
gases.
In this article, we have summarized the logic that goes into the choosing of a 
suitable fan design for both ID and FD fans for a variety of manufacturing processes.
About REITZINDIA
Reitz India has set a benchmark to deliver high quality fans for heavy duty industries 
which can work at precise operating conditions like high temperatures and 
pressures. Reitz offer idealistic Centrifugal Fan and Centrifugal blower design that 
can be used in all large scale process industries like cement, iron & steel, power 
plants, fertilizers/ chemicals and more.
Thank you for spending your precious time in reading this article!