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Need help to calculate how much better (CFM) is one air filter vs the other (Truck air filters)

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MiniMe4Eng

MiniMe4Eng

Electrical
Jun 19, 2015
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I have this Dust Collector (wood working)
The filter is 5microns and my garage all covered in dust because of the inefficiency of this filter.
I have been using a 3M respirator when the things got really bad and I did a lot of work (this is a DIY workshop)

I am now trying to replace the original filter (a bag) with an high efficiency air filter but still pay a decent price for the filter
The woodworking community has been testing various filter models.
The gold standard are the Whynn environmental filters but they are going to cost more than the table saw or the dust collector I have
The alternatives are Donaldson Truck filters which are also 0.5micoron and 99.9 efficiency
- Donaldson P181099
Efficiency: 99.9
Inner Diameter: 9.49
Length: 18.06
Outer Diameter: 13.84
Overall Length: 18.56
Style: Round​
-Donaldson P181038
Efficiency: 99.9
Inner Diameter: 11.07
Length: 23.06
Outer Diameter: 17.58
Overall Length: 23.56
Style: Round​

The dust collector is a 2HP Harbor Freight
SKU(s) 97869, 61790, 45378
Brand CENTRAL MACHINERY
Flow rate 1550 CFM
Volume 70 gallon
AC Volts 120
Amperage 20
Certification CSA, ETL
Horsepower 2
Inlet size 4 in.
Product Height 75-1/2 in.
Product Length 33 in.
Product Weight 100 lb.
Product Width 22 in.
Shipping Weight 98.00 lb.
Filtration (microns) 5 microns​

My question is this: how can I objectively calculate what CFM rate can the Donaldson filters deliver?
P181099 seems to be larger but I am wondering if the DC will benefit from that or maybe P181038 can already match the dust collector CFM?
 
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Update: I found this PDF document -on page 13 EBB filters (like P181099) are rated up to 1650CFM while P181038 is an SRG filter which is rated way above 2050CFM ...

Here is their chart; if you search the above doc for the two models you will find the type of filter for each (EBB and SRG)
So practically then both cover the CFM requirements but it all comes down to how heavy is the Dust environment (left side scale)
EZbnRVm_1_eawnv9.png
 
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I'm confused; how do your lungs compare with a truck engine? Is the truck going to die of silicosis 40 years from now because you used an off-the-shelf truck air intake filter, or does it even care, since it burned everything that made it through the filter?

Do you want to bet your lungs and life on a truck intake filter?

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! faq731-376 forum1529 Entire Forum list
 
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You sound like a fortune teller not like an engineer
0.5 microns is MUCH better that 5 microns.
Microns are microns either for a truck engine or for human lungs
If the Dust Collector was approved to be sold on the american market with a 5 micron bag without being considered a threat to the user then a 0.5micron filter can't be more dangerous, don't you think ?

Please put on your engineer hat, set the fearmongering aside and let's have a technical conversation please
 
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I doubt the Harbor Freight dust collector will pull its rated cfm through the 0.5 micron filter. Its most likely rated some other way than drawing through some filter medium. Anyway, 0.5 micron filter would be less porous than the 5 micron filter. 1/10 ?

Ted
 
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The dust collector information doesn't include the differential pressure at your 1550 CFM and neither do the filters.

So there is no way to answer your question without this data.

In general a higher efficiency and lower micron size will need more differential pressure per square metre of filter per m3 sec of air.

You normally find two pressures- clean and dirty. Make sure to allow for monitoring the pressure or flow and changing them when dirty.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
 
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You guys have very good points
Here is some data, measurements done with a 0.5microns filter, the equivanlent of P181038
Source of the data and how it was measured and calculated/aproximated:
60D32ff.png


So based on your comments it seems that the smaller filter MIGHT cover the needs of this dust collector
It will improve the filtration but it will decrease the CFM. I guess a larger filter translates to higher CFM everything else being equal.

So since both filters will cover the at impeller measured CFM number (which seems to be around 800 either with a bag or with a Whynn filter) the selection of the filter comes down to
how much the smaller filter can limit the CFM.
As per this comment the DC can deliver around 800CFM with the 5micron bag on
The above measurements where taken with the bigger filter at 0.5microns. Since a filter improves the filtration area compared with a bag, but due to a lower micron number increases the resitance to air circulation I could conclude that somehow the bigger filter provides more capacity that the DC would need (since with bag -5microns or large filter 0.5M the measurements seem to be around 800CFM at impeler)

So next it would be to try to guess how much less capacity would the smaller filter provide and try to aproximate the CFM drop
 
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One other thing to think about is whether the filter is designed to flow in to out or out to in....

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
 
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Yeah these are designed for a out to in flow while the woodworking requires the opposite.
These have been used by the community for years and I have not heard or red about this to be a problem although they are aware of the difference

In your opinion how could that impact the performance of the filter ?
 
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I'm not a filter man per se, but my understanding is that these filters are actually multi layer components and hence the outer sections trap the larger particles which then gradually reduce down to the 0.5 micron level.

But opposite way, it all immediately clogs up the inner 0.5 micron filter layer meaning your filter needs cleaning much more often or gives you a much higher DP for the same flow.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
 
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I believe that the line is to mark which side of the filter is which.
In some designs it may be a glue to hold the filter together during assembly (does both jobs).
As LI said, blowing these the wrong way is not good.
What makes it worse is that the filter rating drops when you do this.
There is more pressure driving the particles against the finest media, and what breaks through can easily escape the coarse side.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed
 
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Don't know what to say ..the experience shows that there is lots of woodworkers using these without any visible problems and with a much better performance than the stock bag
 
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Well a lot of your material is dust / small particles so probably works OK, but would work better if you flow the right way around...

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
 
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It would be interesting to know the particle size distribution of the dust that you are dealing with.
My guess is that if we are talking about cutting and milling it is no big deal.
If we are dealing with sanding then it could be a very different matter.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed
 
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Yes cutting and milling, not much sanding for me
If the CFM decreases due to reversed airflow I am OK I think the DC is well under what the filter can support even if reversed
If the air filtration performance goes down then that is wasted money ....
Biggest problem right now for me is that the stock bag is practically a fine dust pump.
Everybody confirms that that is the case
 
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The yellow lines are a hot-melt adhesive used to fixture the outer pleats of the filter to the expanded metal mesh, in order to maintain the desired pleat spacing. Otherwise air pressure will collapse the pleats and pinch-off air-flow. Pleats increase the filter surface area per unit of filter volume, but pleats are not self supporting.

Bag filters rely on a build-up of filter cake to increase filter efficiency. Bag filters are not efficient without the cake.
 
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