Which dust collector would you get

[Sid Matheny]

When I first got my Delta I built this home made separator and it works well. Very little makes it to the DC itself. What you see in the bag is after more than 6 months.



Sid

[Kevin W Johnson]

Kevin, my point was that unless you are very careful when cleaning, a one micron cartridge won't stay one micron, escpecially if the bag is overflowed into the cartridge and chips tear into the filter. A one micron bag generally gets better when the dust cake forms. When I used bags my dylos .5 micron would drop as low as 300 when the DC was on for a while. My nano filters will get the number down to 150 so better but they are new. I won't know how well they hold up for some period of time but without some way to monitor the air you can't assume the cartridge is better just because of it's initial rating. Most commercial shops still use bags with shakers or pulse jet cleaners. Cartridges were originally designed to filter outside to in so the additional filter area also reduced the pressure drop of the system. The fairly recent conversion to inside out filters has made cleaning them more difficult and negated some of the pressure drop benefit. Not advocating bags here, just reminding that care is needed and a poorly performing cartridge or bag reduces cfm which isn't noticeable until after it is way too low to remove dust from the air effectively. Unless you measure velocity or cfm at the machine port and monitor the air you don't really know how safe the system is. I run my motor on a vfd so I can tell by the amp draw if the filters are getting clogged and there are other ways to measure the pressure drop to tell you the same thing. Again, I obviously like cartridges but they are not better in every application. Dave

Most DC's don't come with a 1 micron bag as standard. Yes, they are available, and are cheaper than a cartridge filter. No matter the micron rating of a bag filter (or cartridge), relying on "cake" to improve the micron rating is silly. While that cake improves the micron filtering ability, it comes at a cost of CFM's. Most DC's (short of cyclones) don't have CFM's to spare. Your example of a 1 micron bag getting better with cake, would easily apply to cartridge filters as well. At least the cartridge filters have additional surface area to help keep the CFM's up.

My system has a top hat separator, and a Wynn cartridge filter. I don't remember the exact numbers, but when I replaced the bag with the cartridge, there was a good increase in CFM's. Either way, a separator is a must if you want to keep as much CFM's as your system is capable of. So yes, the cartridge filter has an advantage that you can't get with the bag, and a separator allows it do it's job while maintaining maximum flow.

By the time people with no separator realize they have lost CFM's, they have already exposed themselves to quite a bit of dangerous fine dust.

[David Kumm]

Kevin I agree with most everything you said. I would not use a standard bag and talked of an oversized replacement. There are a lot of material and treatment choices. I don't rely on the "cake" but meant that while both types of filters rely on seasoning- cake- to improve filtration, bags do hold up better under repeated cleaning. Cartridges have more area, due in part to finer filtering and in part to how quickly they surface load in the pleats due in part to the inside out nature of the dust path. Your statement about cfm loss is exactly to my point. With the fine filters we are generally using today we lose cfm pretty quickly as the filters load and although we feel good about .5 micron or even HEPA type filtering, the loss of cfm means more dust never gets into the system but ends up in our lungs. Since dust generated in woodworking isn't of the submicron variety in some situations it might make sense to maximise the cfm through slightly less effective filters rather than restrict the flow through fine but loaded up ones. You are absolutely correct in the need for pre separation as I posted as well. The inherent limits built into the 2 hp system mean some compromise is necessary. I run 6000-7000 fpm through all machines to pull as much as I can but the dylos goes up from a few hundred to a thousand at any machine due to what doesn't get pulled in. At 1500-2000 cfm it clears pretty quickly but with a small system you breathe a lot of dust before the room air goes through the filters- cartridge or bag. Dave

[Michael W. Clark]

By the time people with no separator realize they have lost CFM's, they have already exposed themselves to quite a bit of dangerous fine dust.

Kevin, a separator before the collector also costs you flow. The separator has a differential pressure associated with it. This adds system resistance and causes the fan to operate a lower flow. The net result depends on numerous variables. Some that are unique to your system, and some that are inherent in the DC equipment specs. As another gentleman on here, Ian, says, we need real performance specs on the equipment we purchase before you can estimate the effects of adding additional equipment to the system.

Mike

[Jerry Thompson]

I have never been so confused in my life.

[Jerome Hanby]

More power for less money? Hmmm. Question is, why hasn't an 8 yr old DC ever been used? Does it work?

No input on the dust collector brands, but several year old never used equipment doesn't strike me as all that odd. I'm always catching what seem to me to be good deals on equipment I can see a use for but don't have time, space, need, or whatever for at the moment. I bought a big Jet DC a few years back that I found in the local classifieds. I recently dropped a 240 volt circuit for it, but I still haven't fired it up yet. It has to be pushing 5 years...

[Van Huskey]

I have never been so confused in my life.

Don't worry DC is probably the least understood segment of woodworking. It also breaks some of lifes paradigms ie bigger isn't always better, writing a bigger check doesn't necessarily fix things etc. It also honestly requires some way to objectively monitor air quality and without something like the Dylos that Dave is using we are often shooting in the dark and when shooting in the dark with subjects that involve fluid dynamics it often ends in frustration. Look at F! cars, the teams employ people who know fluid dynamics better than most anyone in the world and spend tens of millions of dollars predicting how air will flow over the car, every year despite all this knowledge at least one team gets it horribly wrong. To add to this you have the two exteme ends with people that will use spray paint in a small enclosed room and no filtration or mask and the other end of the spectrum with people that aren't happy until they essentially work in a plastic bubble, though there has been none of that extremism in this thread.