dP on air filter for centrif blowers?

[NoHoCa]

I'm trying to characterize the system curve for an existing wastewater aeration system based on centrifugal multistage blowers installed in 1991. Specifically, I'm interested in the pressure drop across the inlet air filter. The blower is rated 125 HP and delivers about 1800 scfm drawn from atmospheric conditions. Limited information exists at the facility, and the blower manuf (Lamson, G-D) does not have records on the filter. They referred me to a filter manufacturer named "Industra" for more info, but I could not find them online.

This is for wastewater aeration, so outside air must be filtered to prevent dust from clogging the fine bubble diffusers. I've made inquiries about the pore size on the diffusers but after a week the manuf still has not responded - so I'm unsure of what micron (or mesh?) rating is necessary on the air filter.

Are there typical ranges of pressure drop (in-h2o or psi) for inlet air filters, clean and dirty condition? Are there rules of thumb?

 

[MintJulep]

Why not simply measure it?

125 HP to move 1800 cfm is way outside typical HVAC pressure drops.

You might have better luck in the waste disposal and treatment forum, forum161

 

[marcoh]

Many years ago I worked for a water company and seem to recall that the aeration blowers produced pressures of about 3 atmospheres, ie way more than normal hvac fans and getting closer to compressed air!

If they have existing filters and they are maintained try to find out the specs of these existing filters (assuming they are replaceable and not some sort of scrubber system)

 

[RossABQ]

These are truly blowers, not "HVAC fans". I can understand the need for some filtration to prevent nozzle plugging, but my limited experience with a sludge plant was that the nozzles were about 1/4" diameter. You really just need to keep chunks out of the system, I would think. Low efficiency filters, say 30%, maybe 4 sq ft of them, you should have a pressure drop of under an inch even after some run time. As noted above, all filter mfrs publish velocity vs pressure drop graphs.