The draught fans, which pertain to the centrifugal variety of industrial fans, are among the various types of fans that are used in industrial processes. These fans are further segregated into two subcategories: FD (Forced Draught) fans and ID (Induced Draught) fans.
There is a major difference between these two varieties. The FD fans bring in external air and thrust it inside the air system to ensure that the system remains balanced. The ID variants work in a way to draw in the gases present within the system and expel them into the outside air.
Thermal power plants are the places where the draught fans are of immense value. Here, the fans are helpful in crucial processes such as heating steam, supplying powdered coal, and air preheating.
FD fans – features
Now, let us have a look at the important features of forced draught
fans.
The FD fans are installed at the boiler’s inlet from where they push
air into the combustion chamber, with high pressure. After that, the
air and fuel mix together and this leads to the creation of positive
pressure.
- When power plants are taken into consideration, the forced draught fans serve as primary as well as secondary fans. These fans both make sure that the combustion is proper and also the fuel efficiency improves.
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The design of these fans, which are backward curved ones, is such
that a wheel is there exactly in the middle. The wheel is suspended
from the shaft together with the silencer, inlet boxes, and the
filter.
- With the FD fans, the air is purer and hence exercises only a gentle effect. Therefore, the mechanical life of these fans is higher than that of their ID counterparts.
- The mechanical elements of these fans are easily accessible and this makes things simpler when there is any repair work.
- These fans are totally exposed to extreme climatic conditions.
Induced draught fans – details
These are the key details related to the ID fans:
-
Generally, the area that is precisely in the middle of the chimney
and dust collector is where the ID fan is located. These fans are of
the backward inclined type.
- The induced draught fan sucks in noxious flue gases and directs them to the chimney and from there they get dissipated into the atmosphere. Due to this aspect, these fans are considered to be safer alternatives to the FD fan.
- The ID fan maintains a bit of negative pressure in the furnace. The pressure is lesser than the atmospheric pressure and this makes sure that there is no hassle in the smooth flow of combustion air.
- The power consumption of ID fans is more when compared with the FD types. This is understandable because the elimination of the above flue gases uses a lot of power.
- Since the induced draught fans come into contact with flue gases, they get corroded soon. Using these fans together with electrostatic precipitators also cannot slow down the speed of corrosion.
- The ID fans are protected from the harsh weather to a significant extent, for almost 60% of the fans are enclosed.
- Here, as more than 50% of the fan is covered, it’s quite difficult to gain access to the mechanical parts.