ROLE OF PA AND SA FANS IN THE MANUFACTURING COMBUSTION PROCESS
                     ROLE OF PA AND SA FANS IN THE 
MANUFACTURING COMBUSTION PROCESS
Neel Rao
Writes on Reitzindia industrial fan manufacturers and 
Reitzindia massive industrial fan.
Industrial process fans are essential in the manufacturing process of many 
industries. We hardly find any sector where usage of these process fans isn’t there in 
some way or the other. Industrial process fans, also called blowers, perform many 
important tasks in factories/ plants such as conveying/handling of materials, 
combustion air, the elimination of noxious pollutants and removal of moisture / 
drying.
In fact, in quite a few plants like the ones that involve the generation of thermal 
power, the presence of the blowers attains much more importance. For, they make 
sure that the process of combustion gets completed most appropriately. And, 
combustion is a highly significant aspect of these facilities. Let us now go into more 
detail.
• When combustion of fuel is considered, the PA (primary air) fans as well as the SA 
(secondary air) fans are of almost equal importance. It is only when both these 
blowers are there that the process progresses devoid of hassles.
• In plants/ factories where combustion is a key process, the significance of PA fans 
can never be overstated. These fans bring in an airflow having a very high pressure, 
which thrusts the crushed coal particles toward the furnace, by creating a positive 
pressure. It is only after that that proper combustion takes place. Centrifugal fans 
that are curved in a backward direction are the variants generally used as the 
primary air fans.
• In the same way, we have the SA fans, which are crucial in units where combustion 
is among the most paramount of all processes, too. The main job of secondary air 
fans is to play a supportive role for the PA blowers. There are some situations where 
the airflow coming from the PA fans isn’t sufficient for combustion.
It’s in these instances that the SA fans come to the rescue; they lose no time in 
supplying the added airflow to the system. Following that, there won’t be any 
further issues in the process of combustion. The relevance of the SA fans is also 
attributable to the fact that they make sure that fuel doesn’t get wasted.
ID fans and FD fans in the combustion process
The ID (induced draft) fans and FD (forced draft fans) are the types that are generally 
installed as primary/ secondary air fans in these facilities. Which of those is the 
primary blower, and which is the secondary varies from one unit to another. This is 
primarily dependent on the nature of processes.
• The outlet that is exactly in the middle of the chimney and dust collector is the 
location where the ID fans are fixed. It is from this spot that these blowers collect 
the flue gasses having extreme heat and expel them into the outside environment, 
through the chimney. The fans carry out this by creating negative pressure.
• Since the ID fans are continuously exposed to flue gasses, these blowers tend to 
develop issues related to corrosion quite often.
• The forced draft blowers are present near the boiler’s inlet. From there, the FD 
fans take in the air from outside and push it with high pressure into the chamber 
where combustion happens.
• The cost of maintaining forced draft fans is much less than their ID counterparts.
• Despite the differences in ID and FD fans, both these kinds of blowers ensure that 
power consumption is always on the lower side. This leads to a lot of cost savings, in 
the long- run.
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!