Air Dryer System
of Air Dryer
Why Dry Air
air is used in industries for various applications in pneumatic
tools, pneumatic instruments, pneumatic machines and in a variety of
production processes. The consequences of using wet air are rust
and scale deposits in steel pipes, increased resistance in flow,
malfunctioning of process control instruments, corrosion and damage
to electromagnetic valves and pneumatic system, peeling and
blistering effect on spray painted surface etc. Thus it will affect
the quality of product and lead to excessive maintenance cost.
compressed Air System
|Air from the compressor has excessive
moisture and contaminants. The sketch below shows a typical
Compressed air system to remove these damaging impurities and get
Clean and Dry air.
When compressed to 7Kg/cm2g the temperature of
discharge air reaches around 140oC. The after cooler and Separator
installed after the compressor will cool the air, and removes 90% of
moisture and oil. For instance, when the compressor takes in 100
NM3/hr of ambient air at 40oC and 50% relative humidity, at 7Kg/cm2g
the after cooler will condense an average of 30 liters of water in
If the outlet air temperature from the after
cooler is 40oC, it still contains 8000 ppm moisture. At 45o C
compressed air contains 10,500 ppm, at 50oC, 13,500 ppm moisture
which is removed by Air Dryer. Therefore, lower the temperature of
air at dryer inlet, smaller would be the size of Air Drying Unit.
If compressed air temperature is higher
than 400C, it is essential to precool it to 400C temperature before
Air dryer. This cooling is achieved in a shell & tube type heat
exchanger using cooling water. Due to this cooling some moisture
condenses out which then helps in keeping the moisture load low on
Air dryer and thus better Dew-point of air.
"Dew point is the measure of moisture
in Air. It is the temperature at which moisture present in the Air,
starts condensing. Lower the Dew Point, more dry is the Air.
Air of (-) 400C Dew point means no moisture would condense unless
the temperature of the compressed air goes below (-) 400C. For most
industrial applications Dew point of around (-) 100C is
satisfactory. However, as a common industrial practice, most of Air
dryers are rated for (-) 400C Dew point. Lower the Dew point, higher
would be the operating cost. Hence, proper selection of Dew point is
very important for economical operation.
|Dew point, at Atmospheric pressure
||Moisture content, w/w
Oil present in Compressed air is
detrimental to the desiccant of Air Dyer. If not removed, it gets
coated on the desiccant and reduces moisture adsorption capacity
resulting in frequent replacement of desiccant.Therefore if your
compressor is oil lubricated type, an oil filter before the air
dryer is essential. This oil filter has Activated Carbon which
removes oil from the air completely and thus enhances life of
This is the simplest type of Air Dryer
with Activated Alumina / Molecular sieves Drying agent. Investment
wise also this is the cheapest. This design is virtually maintenance
free, fully automatic, and requires no attention for years.
type dryers do not require any heating for re-generation and
therefore are very simple in design and smooth in operation.
>> Fully Automatic
Eliminates need of costly heaters for regeneration, and also no
cooling water requirement
>> Low temperature operation
reduces corrosion in towers and desiccant lasts longer
Automatic re-pressurizing equalizes desiccant vessels pressure
before changeover. So Desiccant movement is avoided
Desiccant life is around 5- years.
>> Power requirement
is Single-Phase, 60 watts only.