I love trying new ideas. But there are too few hours.
I love seeing some of the unusual solutions that people have developed. This (and some other) forums are great for that.
Maybe someone has tried this…
Advice on good DC system components seems to be pretty consistent (in air stream sequence) –
blast gates
5″ or 6″ ducting w/ reducers for long runs
cyclone or some type of separator
good motor & fan
a round column for filtration
The resulting system catches 90-95% of material at the cyclone.
Really good design for the final filtration characteristics are:
the more surface space the better (2 bags are better than 1, 4 better than 2, etc.
there are cannister type filters that work better than bags
Finer filtration is better
And the better solution in all cases means more cost. I am cheap! But I understand the price of these filters and bags is driven by market forces and production costs. And costs are affected by quantity – woodworking DC filter demand is less than something like home furnace systems. I.e., each square foot of filtration for a home furnace costs less that each square foot of filtration for a DC system. So…
Does the final filter need be round. especially since the cyclone collects almost all the debris? What about a 4 sided square column with fine furnace filters? Or a 6×10 “wall of filters”?
Replies
If you live someplace where it is practical to vent the exhaust from the DC to the outdoors, then you don't need a highly efficient final filter, and some form of furnace filter to catch the finer dust will work fine. An ordinary flat furnace filter, if clogged with dust, will probably blow out from the air pressure generated by a dust collector fan.
If you are returning the filtered air to the shop, then the final filtering needs to be HEPA class to catch the finest dust which presents a serious health hazard.
John W.
I'm not certian that I completely understand your question. But The main constraint for most shops is space not money. High capacity, fine filtering systems take up a lot of space compaired to the average hobby shop system. One cheap and effective solution is to put your DC in a closet that with air tight an air tight door and tight construction. Then Use numerous air filters (20"x 25" is the cheapest) to filter the air returning to the shop. I have four 3M mico allergen filters. They filter down to the smallest stuff and a 3 pack costs like $13 at HD. I clean them every day of work and replace them every .....few months. The filters definately catch a lot of dust, but it didn't seem to change the amount of dust in my shop very much. A lot of dust still escapes machines like my RAS, router and TS. Not to mention all the hand and power sanding! The long and short of it is that a really good DC system costs around 1500 bucks for the average small shop (including the duct work) and that is a whole lot of money. When I move into my new shop I will probably not waste time building a closet like I have now, instead I will buy a top of the line, high capacity filter bag.
Mike
My question really boils down to ROUND vs RECTANGULAR filtering for wood dust. The DC fan sucks the dust in one side (dumping 90-95% of the debris into the cyclone) and blows the dust out into a filter. All of those filters I've seen in small shop systems are round. The few industrial systems (20-30HP, 20-30' cyclones) I've seen do not have columnar "after" filters.Your description of your closet seems similar to what I was thinking. The main difference is you have 80" x 25" of filter. The dual cloth bags system could have about 80" x 30" diam x pi. This is by my calculations 4 times the area you have (I am excluding the pleating). Do you think 4 times the filter area would change things?
Do you use a cyclone or another debris collector - and if so, does it collect 90-95%?From my readings, I think the dust in the air is a different issue. The ceiling mounted air cleaner takes care of that - and I'll bet the techniques you used in your closet install would make constructing one quite easy (there are losts of how-to articles, and furnace blowers seem to be well-suited.)Thank you for your comments. I hope my last comment might be useful to you.
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