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theboss
02-04-2012, 06:26 PM
Dear All,
We intend to design and build a clean air system for transformer fabrication facility. The customer requirement is dust free air with controlled moisture. Fresh air will be continuously pushed into the facility with the help of centrifugal blowers and vented out from gravity controlled louvered configured to maintain a 0.5kpa difference between atmospheric and indoor pressure. The ventilation type is positive displacement.

Filtration will be two stage using pre-filter and HEPA filter.

I would like to have your input in regards to selection of MERV / HEPA filters and the general system design over all as we are taking such job first time. We do have experience in fabricating small units for hospital use however this job is the biggest ever in our scope. Definitely we cannot use medical grade HEPA filters here because they run into thousand bucks per filter.

Every filter maker makes tall claim of 96-97% efficiency but real life experience will tell the actual capability.

The fabrication will be stainless steel and centrifugal blowers will be Ebm-Papst EC-Plug product line.

Brian_UK
02-04-2012, 11:07 PM
Have you considered electrostatic air filtration ?

An example here, filters down to 0.01 micron,...
http://www.rydair.com/modular-electronic.html

aramis
03-04-2012, 12:24 AM
Depending on station process you'll need to setup fume hoods and ventilated workstations or your hepa filters will clogg fast.

Magoo
03-04-2012, 03:21 AM
Hi theboss,
definitly consider electrostaic filtration and roughing pre-filter, structural pressurization is the next problem I generally operate at 5 > 10 pa, with variable fan speed control to compenstae for door openings leakage etc.. 0.5 Kpa is 500 pa

smpsmp45
03-04-2012, 06:00 AM
Also check on the various doors as if locatd in opposite direction can create problems due to such pressure differential

Tesla
03-04-2012, 08:29 AM
Hi boss

Is your room space on positive or negative compared to ambient? I look after a few labs at a uni which are on a negative pressure of 5 - 10 Pa but 500 is whopping - you would need a staging door before entering or leaving the room to open & close doors, this figure should be rechecked. The labs I work on have exhaust from fume hoods depending on how far the hood door is open with large AHUs on VSD to maintain pressure and conditions with filtration.

theboss
03-04-2012, 09:24 AM
The air pushed into the facility will be fresh on continuous basis so there is no reason for it to pick up fumes. Only outdoor dust. The working pressure is 0.05Kpa with positive pressure. Sorry about the typo earlier.

Electrostatic filter is definitely what we can consider but we will need much larger units that those suggested above. Each AHU is going to have 50 Fans and the facility size is

Height 22 Meters (max useable 18 meters)
Width 18.6 Meters
Length: 64 Meters

Brian_UK
03-04-2012, 11:05 PM
Agree with the larger size units being needed, contact manufacturers, I have used walk-in electrostatic units in the past so they are made/can be made.