Did you Select, correct Capacity Air blower for your aeration Tank/Basin ? Any water and wastewater treatment process Air Requirement is inevitable for clear process. many engineer is is still confusing and trouble to choose exact capacity for that application,
for your easy understand we given simple solution with example.
HP of the Blower / Fan = ( CFM X PSI ) / ( 229 X Efficiency of the blower )
Stands for CFM : Cubic Feet per Minute
PSI : Pounds per Square Inch
for Example .. after you determine air quantity of the Aeration Basin,
here we take roughly Require Air quantity = 650 M³/Hr ; Aeration Tank Depth is 4 Metre
Now Apply that figure into above formula,
Firstly, we convert M3/Hr to CFM
1 Metre³ = 35.31 Feet³
So, 650 Metre³ air require per Hour, hence 650 /60 = 10.833 M³ require per Minute
10.83 x 35.31 = 382.41 CFM air require / Minute
Secondly, we determine PSI using Depth 1 Metre Depth Water Column builds 1.42 psi
hence 4 metre Depth created 5.68 psi = 0.4 kg /cm²
Add 1 More metre, for Liquid Depth 4 metre vertical and One or half metre free drop of pipe and distribution pipes, valve’s throttle back pressure which you have fitted in the distribution line
hence we might add 1 to 2 metre roughly that will be better.
4 + 2 = 6 metre = 8.53 psi = 0.6 Kg/cm² is OK
similarly add 10 % Air volume = 383 + 38.3 =421.3 say 425 CFM
So, apply this figure
HP =( 425 X 8.53 ) /( 229 X 0.69) = 10.9 HP say 11 HP Power, Air Blower Capacity is OK
60 TO 78 % Efficiency have Twin Lobe Air Blower, here we took 69% efficiency
Check Blower Efficiency from Name Plate OR straight away ask to supplier.
Now, we should find Motor Capacity in HP
Motor HP = Blower Capacity in HP / Motor Efficiency
Normally it range 75 to 92 %, Here we take 85%
So, = 11/0.85 = 13 HP
we make take 15 HP in motor Side else in neck to neck 12.5 HP.
Good Luck!! … drop your comments.