"you don't want to buy a cyclone separator"

[Phil Thien]

This is my second post to your question, I misplaced the first one. I have a Jet 1200 with the Super Dust Deputy (SDD) and measured off the 6" inlet 5700 fpm/1114 cfm. After the SDD/55 gal drum/5 feet metal duct/5 ft of flex gave me 5800 fpm/1089 cfm. That is a 25 cfm loss through all that hardware. The guy who said you would see 35 per cent loss is wrong. I measured my with a Alnor anemometer model RVA.

Measuring airflow through a pipe is trickier than it seems.

FWW's comparison of the SDD to a DC equipped with my baffle design indicated a more substantial hit.

With no separator, the airflow was approx. 550-CFM. Adding one of my baffles to the ring dropped the CFM to approx. 525-CFM (about 5%).

Then they tried a SDD, and that brought the CFM down to approx. 430-CFM (a 30% hit).

In all fairness, the FWW article did show the separation of the SDD was superior to the unit modified with the Thien baffle. OTOH, the DC they modified with the Thien baffle wasn't really the ideal choice, as the bag retention method interferes with the proper operation of the Thien baffle.

[Mike Chalmers]

I have a Jet 1200 (12" fan) hooked to a Super Dust Deputy (SDD) and ran some cfm/fpm numbers using a Alnor anemometer Model RVA. The DC with a 6" 90 degree fitting measured 5700 fpm/1114 cfm from the pipe center.
The Jet DC with 6" flex running to the SDD sitting on a 55 gal barrel and 5 ft of straight metal duct measured 5800 fpm/1089 cfm. This leaves a total loss through all my hardware including the SDD was a whole 25 cfm. Therefore, the guy who said you would see a 35 per cent loss is not correct. I ran 35 gal of nothing but dust and found less than 1/2 cup of dust in my bag even after using the flapper.

Hear, hear! Actual statistics from someone with actual experience instead of speculation or regurgitation of "facts" from some web site. I run a SDD on a 2hp using flex hose and am very satisfied that I am controlling the dust. I do not have any equipment to actually measure my CFM etc, however, I do have the evidence of my eyes and nasal passages.

[Julie Moriarty]

So my questions are: 1) Does a cyclone really have that much negative impact on blower performance and 2) does a cyclone separator offer other benefits in addition to keeping the filter from getting clogged up?

When I converted my drum dust collector to a shop-built cyclone I didn't notice any drop off in performance but did notice the drum collected much more dust and chips. Mine vents to the outside (no filter) and, before the cyclone addition, ejected most of the waste outside. I'm very happy I made the addition.

[Alan Schaffter]

Hear, hear! Actual statistics from someone with actual experience instead of speculation or regurgitation of "facts" from some web site. I run a SDD on a 2hp using flex hose and am very satisfied that I am controlling the dust. I do not have any equipment to actually measure my CFM etc, however, I do have the evidence of my eyes and nasal passages.

I agree "speculation" surely adds nothing, but without knowing the specifics of testing, who says the "actual statistics from someone with experience" are any better. For example, is the Alnor vane type anemometer versus a hot wire anemometer, best in this situation ? How was it used? Were multiple readings taken across the opening in the same place- velocity decreases rapidly as you approach the walls of the inlet- for each reading during all tests? Were the readings averaged or integrated? It can make a big difference. The "regurgitated 'facts'" from "some website" may in fact have been obtained during repetitive, well designed and conducted experiments. Finally, your last two statements fall under the worst category of speculation. "I . . . satisfied that I am controlling the dust." "I do not have any equipment to actually measure my CFM etc.. . . . . however, I do have the evidence of my eyes and nasal passages." Tell us what kind of woodworking operations you do and provide us with before, during, and after Dylos readings. The dangerous stuff is typically not captured by mucous in the nasal passages, etc.

The whole point of my post, is that rarely, if ever, do these posts contain results or comparisons that would hold up under any sort of scientific scrutiny.

[Mark Carlson]

I put a SDD on a 1 1/2 hp Delta 50-760. It did reduce the suction. I dont know the exact percent, my gut says 15% after putting my hand in front of the inlet. Scientific I know. The important thing is the performance I now get is constant and good. The performance I got without the SDD was better initially but quickly became much worse as the canister filter clogged. Not to mention I was constantly cleaning a filter and ruining it by constantly cleaning it.

I agree with previous comments about flappers being useless at best and bad at worse. Only get a canister if your willing to pre-separate. My opinions
~mark

[Art Mann]

I agree "speculation" surely adds nothing, but without knowing the specifics of testing, who says the "actual statistics from someone with experience" are any better. For example, is the Alnor vane type anemometer versus a hot wire anemometer, best in this situation ? How was it used? Were multiple readings taken across the opening in the same place- velocity decreases rapidly as you approach the walls of the inlet- for each reading during all tests? Were the readings averaged or integrated? It can make a big difference. The "regurgitated 'facts'" from "some website" may in fact have been obtained during repetitive, well designed and conducted experiments. Finally, your last two statements fall under the worst category of speculation. "I . . . satisfied that I am controlling the dust." "I do not have any equipment to actually measure my CFM etc.. . . . . however, I do have the evidence of my eyes and nasal passages." Tell us what kind of woodworking operations you do and provide us with before, during, and after Dylos readings. The dangerous stuff is typically not captured by mucous in the nasal passages, etc.

The whole point of my post, is that rarely, if ever, do these posts contain results or comparisons that would hold up under any sort of scientific scrutiny.

Hear, hear! Finally, someone observes that anecdotal evidence under uncontrolled circumstances typically does not provide much useful information.

[Michael W. Clark]

I think Fred's readings may have been taken on either side of the SDD. If so, that is not the loss being described by the salesman.

I don't trust the salesman, but he would have been more wrong to have said that you can put a cyclone or separator in the system and the flow will not be affected.

Mike

[Bradley Potts]

Hear, hear! Finally, someone observes that anecdotal evidence under uncontrolled circumstances typically does not provide much useful information.

DITTO. I'll also remind folks that what Alan is talking about is called "data." Proper data is impartial because it is a simply a report of observed facts, however humans decide which data to collect, how to collect/generate it, which to keep, which to analyze, and most tricky of all: which conclusions can be drawn from the analysis. Every single one of those steps can be manipulated in such a way as to steer the outcome(s) and the conclusions. Enter the Ad Man....

Ultimately, unless we each objectively and correctly test our systems, we will have to make "a leap of faith" before we can move forward. To control the inherent risks therein, we'll have to rely on 2 things to arrive at an acceptable DC system: A) Employment of known and credible guiding facts, and B) The highest level of craftsmanship in assembling a system that honors those guiding facts. The proof will be in the end result, which for me will be whether or not my system can draw off the dust from my sources, like the RAS and the planer.

This is an appropriate moment to point out that this entire thread has skipped over a critical element in DC systems: Collection at the immediate source! This is Festool's game plan, so each of us should really endeavor to follow Festool's example and maximize the dust capture at the source, then the rest of the thread can come into play.


-- Bradley

[paul cottingham]

Ok. I have no hard data to back my claims up, but, a Thien style top hat separator works great with my 1.5 hp steel city DC. Is there CFM loss? Yep. Is that offset by:

Way less crap getting into my DC?
And the filter getting less clogged?
And emptying the chip collector being much easier?
The ability to bypass my filter bags and vent outside?

And that's good enough for me.

I wish I could afford a much better, more efficient cyclone system, but for the amount of power tool usage I have in my shop, and for the sake of my marriage, its not an option.

[Bradley Potts]

Bradley,

Are you thinking a "dust right" sorta-cyclone lid on a can, or the Oneida dust deputy mini-cyclone? I would have thought the dust deputy highly restrictive to a DC, given the small openings, but I've not used one. daniel

@daniel: As I noted, it would be a DD (or SDD), and only because it has been proven to be about 3% cleaner than a Thien baffle. Yes, the smaller inlet is a restriction for CFM, but it will INCREASE the static lift (I think that’s the correct term), which is desirable at the source. That CFM matters when the debris must travel thru long pipe runs. That’s only one reason why my proposed system will 100% eliminate pipe runs. A mobile system limits the total of needed bits n' bobs AND the req'd size for them as well, which ultimately saves even more money and reduces the amount of crap, er um, stuff that I have laying around.

A key concept for us to grasp is that it is the very expensive, elaborate, big, and EVOLVED systems that are the fodder for Pentz’s very thoughtful and well-intentioned work. Those systems are based on an industrial/production model which are in big spaces, have lots of big tools producing huge volumes of dust, have several operators producing that dust all at the same time, and these type systems have strong fiscal incentive for a central maintenance point and they can generate beneficial economies of scale by using a central collection system. Central DC’s are complex, industrial grade solutions for industrial grade problems. They also are loud and serious suckers of electricity.

A hobby style or small shop posses none of those attributes, so a responsible designer will point out that the central collection systems are likely an inappropriate solution to our small shop needs; that is unless we are willing to make some very costly sacrifices. I’m an architect by profession and understand the vast majority of us are truthfully only hobbyists or small-scale operators; we flat-out don’t need an industrial solution for a hobby issue. Some of us choose to work wood and some choose to go the path of machine hot-rodding and collection -- spend your $$ accordingly.


-- Bradley

[Bradley Potts]

A separator is total overkill if all you want is something you can connect to one tool at a time. Use the black plastic contractor bags; way cheaper than the clear ones made for DC's. I'd also forget about the pleated filter and get a shaker felt bag, instead. They don't wear out and some, like mine, filter down to 1-micron. My Delta unit is a 1-1/2HP model (that they no longer make), is ultra portable, and works just fine if I keep my hose lengths relatively short. I do think adding a separator will add a bit of friction loss, so the guy at the woodworking supply store is probably right. I don't buy the bit about the flapper being "designed to wear out." Also keep your hose diameter full size and reduce down at the tool (not at the collector).

@Jason, this is where I've landed, except that I consider the drop box and separator to be equivalent in terms of work, so I've used a Thien because of its superior extraction. KISS, "Keep It Simple, Stupid!"


-- Bradley

[Bradley Potts]

Ok. I have no hard data to back my claims up, but, a Thien style top hat separator works great with my 1.5 hp steel city DC. Is there CFM loss? Yep. Is that offset by:

Way less crap getting into my DC?
And the filter getting less clogged?
And emptying the chip collector being much easier?
The ability to bypass my filter bags and vent outside?

And that's good enough for me.

That's what I'm talking about!

[Alan Schaffter]

@daniel: As I noted, it would be a DD (or SDD), and only because it has been proven to be about 3% cleaner than a Thien baffle. Yes, the smaller inlet is a restriction for CFM, but it will INCREASE the static lift (I think that’s the correct term), which is desirable at the source. That CFM matters when the debris must travel thru long pipe runs. That’s only one reason why my proposed system will 100% eliminate pipe runs. A mobile system limits the total of needed bits n' bobs AND the req'd size for them as well, which ultimately saves even more money and reduces the amount of crap, er um, stuff that I have laying around.

Yes, with a smaller inlet you are trading CFM for SP (static pressure)- you WANT CFM at the source- remember all the fine dust escapes and expands from the source in almost a sphere- every direction. CFM is the only way you will have any chance of capturing it. You still need a little SP to overcome duct resistance, etc. (look at a fan curve) but SP really comes into play when you are trying to suck dust through a small duct, hose, or tool dust port (whole house vac, ROS and router hoses, CMS blade shroud, etc.) or need to pick up stationary dust on a surface (or pick up a bowling ball ) What matters in long duct work is both CFM and SP, but if you are talking about dust settling out of the air stream in the duct, what matters is VELOCITY (4000 +/- fpm, depending on whether the duct is horizontal or vertical), not CFM. While a mobile system may eliminate "bits and bobs" you are still left with the filter issue- unless you can discharge outside with another length of flex- which in itself will add SP and limit CFM.

A key concept for us to grasp is that it is the very expensive, elaborate, big, and EVOLVED systems that are the fodder for Pentz’s very thoughtful and well-intentioned work. Those systems are based on an industrial/production model which are in big spaces, have lots of big tools producing huge volumes of dust, have several operators producing that dust all at the same time, and these type systems have strong fiscal incentive for a central maintenance point and they can generate beneficial economies of scale by using a central collection system. Central DC’s are complex, industrial grade solutions for industrial grade problems. They also are loud and serious suckers of electricity.

You are missing most of what Bill has to say- his website is totally focused on home shop dust collection! He would need to include 25 hp blowers, 12" ducting, bag house filters, etc. if he were to address industrial systems! But you are partially right, "Central DC’s are complex" and they can be expensive. For someone who doesn't have the means, the most effective and economical approach to dust collection is to find a small roll-around DC to pick up the chips and use an effective mask to protect your lungs- no one (Bill P, Oneida, Grizzly, ClearVue) has been able to come up with a dust collection system that will perform as well. There is no right or wrong- it is a continuum: bad systems to better systems, and cost follows that pattern.

A hobby style or small shop posses none of those attributes, so a responsible designer will point out that the central collection systems are likely an inappropriate solution to our small shop needs; that is unless we are willing to make some very costly sacrifices. I’m an architect by profession and understand the vast majority of us are truthfully only hobbyists or small-scale operators; we flat-out don’t need an industrial solution for a hobby issue. Some of us choose to work wood and some choose to go the path of machine hot-rodding and collection -- spend your $$ accordingly.

-- Bradley

Here is just one reason everyone should get as smart as possible before buying any DC. While looking up the inlet diameters for the DD and SDD I noticed this bit of information about that manufacturer's Super Cartridge Filter Retrofit Kit. Look at the Gee Whiz filter specs: "Filter Media Captures 99.9% of Test Material from 0.2 - 2 Microns @ 11 FPM /Accredited, Independent Lab Tested." Pretty darn good huh? That is until you take a closer look at the easy-to-overlook "@ 11FPM" design/testing spec! Do the math!

I don't know the velocity of your DC, but for argument's sake, let's say it is at least 4000 fpm, a typical velocity for material handling blowers. Inlet area (in sq. ft.) times velocity (4000 fpm) = CFM through the filter. The SDD has a 5" dia. inlet. so cross-sectional area = pi X 2.5² sq. in. = 19.63 sq. in. To convert to sq. ft. we must divide by 144 = .136 sq. ft. Multiply that times 4000 fpm and you get 545.4 CFM. Now you need to ask yourself what happens to that ASRAE rating when you try to push 545 CFM through a filter media that is rated at 11 fpm (amd what happens to CFM when you try to push it through that filter). I don't know the answer, but am also certain no salesman will either. I doubt the rating will be as good as claimed!

Again, while not rocket science, dust collection is physics and can be complicated.

[Phil Thien]

@daniel: As I noted, it would be a DD (or SDD), and only because it has been proven to be about 3% cleaner than a Thien baffle.
-- Bradley

Have a source for the 3% proof?

I'm not saying a conventional cyclone doesn't separate better, but I'd be amazed someone has proven one is "3% cleaner" than the other.

[Michael W. Clark]

Now you need to ask yourself what happens to that ASRAE rating when you try to push 545 CFM through a filter media that is rated at 11 fpm (amd what happens to CFM when you try to push it through that filter)

As the filter velocity increases, small particles are pushed deeper into the media. This makes cleaning more difficult or less effective. The "clean pressure drop" will get higher over time until cleaning does not lower it to an acceptable level. The higher pressure drop reduces fan/system flow which reduces capture velocity at the hood. The result is less dust captured at the source. A new filter will return the system to normal flow until the process repeats itself.

This assumes the filter is not damaged during cleaning, which would result in emissions from the filter as well.

I am an advocate of bags. Bags are easier to clean and therefore usually designed for a higher filter velocity. When I use cartridges, I try to use more filter area to keep the velocity lower.Typical industrial baghouses run about 6 fpm with automatic cleaning (varies with the application). A much lower velocity is used if you only have fines.