Draft fans are kinds of industrial fans, also called blowers, and are used in several plants and factories. Draft fans are further subdivided into two types – FD (Forced Draft) fans and ID (Induced Draft) fans.

1. FD FANS – PA AND SA FANS & APPLICATIONS
Neel Rao
Writes on Reitzindia industrial fan manufacturers and
Reitz India's ID Fans and FD Fans.

2. Draft fans are kinds of industrial fans, also called blowers, and are used in several
plants and factories. Draft fans are further subdivided into two types – FD (Forced
Draft) fans and ID (Induced Draft) fans.
The scope of this article is going to be focused on FD fans and the way they work as
both primary air (PA) fans and secondary air (SA) fans. Firstly, it will help to have a
basic understanding of forced draft fans.
What are forced draft fans?
FD fans are equipment used in plants involved in the generation of thermal power.
These fans, which are installed at the boiler system’s inlet, take in fresh air from the
outside atmosphere and push it inside the combustion chamber with increased
pressure. In the chamber, the fuel gets mixed with this air and this leads to the
creation of positive pressure.

3. As a direct result of that, the process of combustion goes on in an unhindered way.
Here, it must be highlighted that the amount of power consumed by FD fans is on
the lower side. This helps the business in saving costs specific to energy
consumption. The FD fans are suitable to be used as primary as well as secondary
air(SA) fans.
FD fans – PA and SA fans
These are some salient points related to how the FD fans play the dual role of both
PA and SA fans.
• A boiler system has two inlets to enable the flow of air into the chamber where
combustion takes place. The FD fan that serves as the primary air fan is installed
near the first inlet. And, the second inlet is the site where the blower acting as the
secondary air fan is deployed.

4. • Normally, the air provided by the primary air fan is sufficient to make sure that the
process of combustion goes on appropriately. This blower separates particles of fuel
so that each of those is touched by the air coming in at high pressure. This FD fan is
helpful in constantly maintaining the temperature inside the furnace at the needed
level, too.
•But at times, there are situations where the air supplied by the primary fan is
inadequate for the completion of the process. The system then immediately requires
an additional quantity of air. It is here that the FD blower operating as the secondary
fan comes to the rescue. These fans lose no time in sending the added air within the
boiler ensuring that the combustion process is not interrupted.
• In the above circumstances, the presence of secondary air fans is imperative to
make certain that there is no fuel wastage. And, that is a key aspect that no business
can ignore.

5. • Sometimes, it happens that out of the entire air brought in by the primary fan, a
little part remains unused. Here, the air provided by the secondary fan also helps in
the full utilization of that unused quantity.
• Thermal plants that are based on coal hold the number one position, in terms of
the leading producers of electricity. Coal mining is an activity that carries huge costs,
and thus; a plant cannot afford to leave even a small amount of coal unburnt in the
chamber. In this respect, when secondary air fans are also there for the boiler
system, the entire coal gets rightly combusted. Unwanted costs can be avoided.

6. 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!