Bill Pentz Discussion

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eoinsgaff

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My attention was recently drawn to Bill Pentz's website on dust extraction and the pitfalls for small scale or hobbyist wood workers.

http://billpentz.com/woodworking/cyclone/index.cfm

I found this site riveting as well as a disturbing.

Personally I'm inclined to believe what he is saying and I think it has merit but it would be foolish of me to take his word as gospel straight off. For that reason I think a decent discussion is required.

If what he is saying is correct then I would wager that there is very few of us, those who don't have a professional shop of considerable size, who are not in a significant long term health risk.

So, bring it on. Considered option, nae sayers, yes men, vitriol and the like. Lets hear it all...

Regards

Eoin
 
Hmmm.... I too have spent a disproportionate amount of time on his site trying to follow what he's saying. I get the main gist but I don't quite get why there's only one "authority" on the subject. And where's the scientific evidence? I'm not disputing that dust is a hazard and quite serious in some cases - that I can believe. However, where's the tests in a controlled environment with control tests to prove that his solution actually works or, perhaps more the point, other lesser solutions DON'T work?

I get that dust comes in sizes less than 0.5 micron. So, it follows, that a vacuum with a filter performance of down to 0.5 micron will blow smaller particles back in to the workshop. It also follows that a respirator with a filter performance to 0.5 micron will suck in and blow smaller particles at your face. Or, a passive mask will allow smaller particles in. And an air filter with similar performance will also blow smaller particles around the air. So, venting the vacuum outside seems like a good measure. Catch the bulk of the dust and shove it outside, keeping the concentration inside the workshop to a reasonable level.

I did this with my DX5000. I've had a mirror laid horizontally in the workshop for two weeks now and, if I run my finger across it, you'd be hard pressed to see a track. I'm a hobbyist so that does not account for two weeks worth of woodworking, nor have I done a lot of machining - but I have done some.

I'm not a disbeliever but currently that's only because I don't want to regret not giving the dangers due consideration. Have I rushed out and built a cyclone? No - I'm keeping an open mind as I suspect someone else will be along soon with another angle and another solution etc.

So - to summarise:
1. Dust = danger. Yes, I don't dispute.
2. Bill Pentz's solution is significantly better than my DX5000 vented to outside - Hmmmmmmmmmmmm.... Not convinced. Better, maybe - significantly - where's the evidence? Based on his original analysis - we would have to wait X years to see a drop in dust related health problems.
 
Hmmm,

I've seen Head Clansman's post before and it would have been of the same layout as I was considering before reading Bill Pentz.

What Bill proposes is different and quite specific and his technical reasoning seems sound to me as it brings back some of the fluid dynamics and thermofluids I was supposed to have studied in college.

To summarize what I think Bill Pentz is saying:
  • Minimum 150mm ducting with no reductions
Smooth bore piping with large sweep bends
  • Extractor air outlet to be outside or very significant filtration
Various other details on blast gates and hoods etc.

In fairness I've still a lot more to read from Bill.

Eoin
 
After reading Bill Pentz website i feel a bit confused about what is a good dust extractor. At the moment my workshop is just getting up and running and i am now trying to decide a dust extractor to buy. From reading his website it seems that no commercial dust extractor that is being sold is good enough, this doesn't really help me as i don't really know much about duct extraction, but i do want to get it right first time round. He quotes many american brands and the gist that i got - even though i did not understand some of the things he said - is that they haven't got enough suction power and fine enough filters to truly remove the fine dangerous dust. So the question that i am asking is.

What is the best dust extractor to buy considering this information?

Thanks

Woody.
 
I think I should summarize what Bill Pentz is saying in a better format.

Firstly, as I would read it, he has primary concerns as follows:
* hobbiest or small commercial wood workers are in a very significant danger from a super fine dust not visible to the naked eye.
* This is because dust extraction units for these people are generally in the shop and also vent into the shop rather than being stored outside.
* The end result of all this is that the super fine particles are being pumped around the shop by the extraction unit rather than being removed.
* Being super fine these particals float in the air indefinitly and are inhaled continously. The volume of the super fine particals continues to grow and rapidly achieve very dangerous levels.
* The filtration systems in just about all of these machines is not fine enough to remove this dust and if they were, they would not work efficiently.


There are then a number of secondary concerns.
* Extraction machines do not move nearly as much air as specified and are therefore inherently inefficient.
* People have a fundamental misunderstanding of the way these machines work. Extraction machines move large volumes of air. Shop vacumns move air very fast. It is not possible to reduce an extraction duct from 150mm to 50mm and expect the performace of a shop vacumn.
* Filtration systems are also grosly inefficient as a result of the poorly designed extraction machines. For example, the cyclones do not separate enough of the dust into the bins and so the filters get blocked very quickly. This is especially true if filters fine enough to remove the 'super fine particals'.

Solutions proposed by Bill Pentz.
* Set up the extractor outside.
* Failing that vent the extraction machine outside and ensure the dust cannot be blown back into the shop.
* 150mm ducting is the optimum size of duct when used with what he proposes as the optimum blower performance for a small shop -
* As mentioned above an optimum performance for the extraction blower is proposed but I don't have it at hand. I'll add later.
* Numerous other small details on ducting such as bends, sweeps, blast gates etc.
* Bill has also proposed a design for a more efficient cyclone which can be made at home.

I hope this will make the situation a little clearer and allow us to focus on the problems and solutions separately. There is much more detail and I need to continue reading his stuff so this is anything but definitive.

Regards

Eoin
 
Interesting thread - my thoughts will turn to extraction relatively soon.

eoinsgaff":ihmb8p3h said:
* hobbiest or small commercial wood workers are in a very significant danger from a super fine dust not visible to the naked eye.
* This is because dust extraction units for these people are generally in the shop and also vent into the shop rather than being stored outside.
* The end result of all this is that the super fine particles are being pumped around the shop by the extraction unit rather than being removed.
* Being super fine these particals float in the air indefinitly and are inhaled continously. The volume of the super fine particals continues to grow and rapidly achieve very dangerous levels.
* The filtration systems in just about all of these machines is not fine enough to remove this dust and if they were, they would not work efficiently.
Click to expand...

The one thing I would point out - if you think dust in a woodworking workshop poses a danger, how about an Auto Bodyshop? Epoxy and other fillers being sanded with air tools using abrasives upto and past 1500G. Not to mention 2 pack paints\lacquers as well. Air lines being used to blow dust off and into the atmosphere. The ducting is 6" on the whole in these places with smaller 2" or thereabouts for the drops.

But I have never seen the vacuum\filtration systems outside the shop. Not wanting to go off topic - my only reason for mentioning the Auto side of things is that they do use stuff where the dust, etc. has far greater consequences and usually quicker.

So back to Bill Pentz - yes the systems would be better stored outside - common sense. Matt has nailed it on the head for me - I would like to see evidence before an "Authoritative" position is stated.
 
Thanks Eoin that makes things much clearer. But can anyone advise a dust extractor with a filtration system that would be the best to reduce these fine particles going in the air?

Thanks

Woody.
 
Biggest problem for me is that I cant have my extractor outside :(

looks like I'll be ordering a huge batch of 3M 4251

Trend airsheild on the list as well I suppose
 
Hi Eoin and guys, i've as you know been banging away on this for a while too - albeit i'm still at the stage where i'm installing but my Pentz system is not up and running yet. I set out the basis of my decision to try this route a while ago.

One way of looking at the issue of choosing your dust equipment is that to get proper extraction at a machine you need properly designed hoods (to intercept high speed dust particles), and then to pull in enough air to capture that dust. (the finer and more dangerous portion of which is invisible)

There's a section in Bill's pages explaining how this translates to what's needed in terms of air movement which (i gather) is drawn from the H&S/medical standards he quotes - he talks in terms of creating a (roughly spherical) volume of air around the cutter that's big enough to prevent dust escaping, with at least 50ft/sec (i think is the number? - check his pages) face velocity/air movement inwards over its outer surface.

It's no problem to get 50ft/sec from even a tiny fan, but it's clear that as you increase the size of the sphere the volume of air needed increases very rapidly indeed. (because the surface area of the sphere is proportional to its radius squared - the radius multiplied by itself)

This is in effect the factor that determines how much volume of air movement (cfm) you need to do a good dust collection job. i.e. even quite moderate increases in the size of the sphere/volume cleared of dust around the cutter increase the volume of air required very rapidly.

Once the required air volume is specified you can theoretically do the job with several different varieties of fan delivering varying combinations of volume and pressure drop. i.e. a fan capable of a higher pressure drop/level of suction like a vacuum can theoretically do the job by moving the air at higher velocity through smaller ducting.

The catch though is that it still has to deliver enough air movement at the business end, and in this regard there's no free lunch as you still need to put in enough energy/fan HP:

fan or blower HP = cfm X PIW/6356 X fan efficiency ( %/100)

Where:
cfm = cubic feet per minute
PIW = pressure drop/suction in in water gauge

i.e. you can in effect trade between cfm and PIW in the fan type you choose, but in the end for a given fan efficiency cfm is proportional to HP.

Bill went the large duct/lower velocity route - i suspect basically because this type of impeller while not very efficient is proven to be highly resistant to dust, shaving and chunks of wood coming through the system; and opens the way to low cost DIY fans like his MDF design. It's relatively quiet too due to the lower velocity, although since the fan is inefficient it makes more noise than it could and seems to be running about as fast as is feasible in this regard.

There's no particular reason to think that Bill's is an optimised solution. The fan/impeller type he used is standard usage for dust handling in industry, but he himself for example played around with aerofoil cage type fans as they are much more efficient. (the downside is that they stall and vibrate badly if taken outside of a fairly narrow pressure drop range, and they don't handle dust and shavings very well)

So the air movement task can probably be done other ways using different kit, but it's not that easily improved on.

My personal view is that it's probably a relatively crude and power heavy but effective solution. (typical US industry practice actually) Ideally much more work is needed on hoods and dust interception methods at the blade. If the dust can be contained in a small area, then much lower fan HP/air volume can do the job. Secondary benefits would be much smaller and more convenient ducting sizes. More efficient fan types would allow much higher velocities with no more noise. The likes of Festool have shown how well this sort of approach can work, at least on handtools it seems.

I went Bill's route because it seems to be a pretty well proven option, and i haven't got two years to spend on R&D - and don't want to buy a pig in a poke. But maybe you guys know of something else better that delivers the above requirements.

The big advantage of a high volume system like Bill's is that it's got to be much more tolerant of variations in hood layout seen on the multiple machine types seen in your average shop, also of certain types of ducting funnies like leaks and so on. Plus if you can handle the DIY route it's a relatively cost effective way to get set up...
 
I agree wholeheartedly with Bill Pentz'z reasons for taking dust extraction seriously. Hardwood dust is proven to be linked to cancer and other diseases.

The recommendations on his website are all backed up by maths so I'm not gonna argue - I'm just do what the man says.

I've got no intention to make a system complying to his spec. I'm good with wood but nought else.

Gonna install 6" ducting. Local builder merchants do it for underground drains.

Apart from ClearVue in the US (who are ceasing to trade soon) who makes a cyclone that meets his spec?

Can someone please explain to me how I set up/buy or modify a system which seperates fine dust and chips, sticks the chips in a bin and exhausts the fine dust outside? This sounds like a good idea but I dunno how to do it?

I thinks this is a great discussion also
 
It's not too hard to do that Andrew. Even a fairly inefficient cyclone/separator will drop out heavy woodchips. It takes a well optimised design and set up (as Bill's reputedly is) to drop out the fine dust in a cyclone as well - small particles are very light, and don't drop out of the airflow so easily.

One way you could set up to do what you say is to use a cyclone, but run the outlet from it outside. This in the case of the stock layout for Bill's system would result in the 8in dia duct from the fan/blower outlet going directly outside instead of through filters.

If you can exhaust outside then the good news is that you would probably get away with a very basic cyclone/separator - something like a trash can separator. These are fairly common usage in the US, but don't do well at separating fine dust. (Bill for this reason reckons they are unsuitable for use with fine filters)

Here's the Woodcraft version for a standard US trash can: http://www.woodcraft.com/Catalog/Produc ... ef1511f80a It only takes 4 inch hoses, but you could probably do a DIY version on a larger 55 gal barrel to suit 8 in ducting.

There is potentially a big problem with this option. If you go that route you need to think through carefully whether or not you can tolerate dumping the air outside - from the point of view of whether or not the cooling effect of cold and potentially humid outside air being drawn into your shop will cause a problem, and ditto the dust going outside. Take a careful look at the other thread where the pros and cons of exhausting rather than recycling through high efficiency filters were discussed in detail.

Some are using high efficiency filters, but installing an outside exhaust anyway - by placing a 45 deg Y in the exhaust duct, with one leg of the Y going to the filters, and the other going outside. A blast gate in the duct just after the Y branch into the filters makes it possible to either use the filters, or to exhaust outside when weather suits....
 
hi guys,

mind if throw something into the mix?

from the research i've done (extensive), on toxins and hazards to health and the onset of cancer, there is a significant factor that most people do not consider.

we (most of western humanity), live in EXTREMELY toxic environments. from our microwave ovens, wifi connections and mobile phones; to our plastic floors, vinyl wallpaper, solvent based paint and artificial air freshners; to our plastic housed, ready prepared, highly processed food and plastic housed poison (aspartame) filled drinks; to our undersink cupboard full of god knows what; to our plastic clothes, shampoo, deoderant, perfume, make-up (two for the ladies) and suncream covered days in the sun. and thats without stepping out the front gate.

with a list like that, your workshop is the safest room in the house.

our bodies are under constant attack and as such our immune systems are very often overcome. this will increase the risk in the workshop from dust, because your body is having a hard enough time fighting off everything else.

i'm not saying that wood dust does not pose risks, i have a dust extractor. i would even like to make it more efficient. but all things considered, i would much rather take my chances figthing something i am actually made of (all living things except sulphur based life forms are made from the same 18 elements) than trying to fight the pinnacle of man's achievement......plastic

it is my cosidered opinion that, for a healthy life we must minimise as much as possible our exposure to ALL toxins and that should start in the place you spend MOST time

if anyone doubts the dangers of any of the above, just do a quick ingredient search and check out the known side affects.

jeff
 
hi

hm-mm, guys .

you can spend as much time and money as you all feel necessary on your individual extraction system, install expensive pipe work,with all glued joints ,making airtight blast gates as i did , attached to it what you feel is the right extraction unit , BUT, and this the BUT it all falls apart the moment you switch on the machine that you want to use It will only suck up the dust it manages to capture at the time whilst using it , meaning badly designed machinery allows dust to escape all round it, as were seeing from others that have posted here on the forum. there is no such thing as a machine or extraction unit that will deal with 100% of the dust to much will escape until we get better DESIGNED machinery being made, Which will never happen .

Some dust (in fact a lot of dust) will get air born you will never stop that happening no matter who's opinion you decide to follow,or how good your suction is it will never take it all away, all any of us can do is try and take as much as possible. DAMAGE LIMITATION .hc
 
Maybe before we decide on the need, or not, to change all our dust extraction setups we could look at Pentz's number one concern - the dust.

Does this super fine dust exist? If so, how dangerous is it?

Then maybe we could look at his contention that all of our indoor extraction equipment are in fact 'dust pumps' that increases the amount of this super fine dust in the air and agitates it continuously.

If we came to a conclusion on those two points we would then be in a great position to decide if we need to go to the extremes proposed by Bill Pentz.

Eoin
 
HC,

i take your point on the design of our machines. Its very valid and also needs to be discussed, maybe even in a different thread.

I read an article recently - recently being sometime in the past two years or so - in Fine Woodworking were a reader had carried out some very clever work to seal up his tablesaw and, with a little fluid dynamics, had managed to increase the air flow to the extraction system to increase its efficiently considerably.

Intuitively his solutions looked like they would work very well and may be of some relevance here. I must dig them up again if I can.

Eoin
 
It'd be interesting Eoin to maybe organise a group buy of one of those Dylos particle counters between a decent sized group who agree rules for co-operation on its use.

Maybe agree these and plans first that everybody signs up to. Then maybe circulate it around the group fairly rapidly - leaving it with everybody initially for a few days. Each would report their findings in their own shop on the forum and commit to mailing it on to the next guy on the list after X days. Etc

The arrangement could easily come unstuck if somebody does not play ball.

It might be possible if people were keen to do the same to buy a duct pressure and air speed measurement set up. You can buy fancy instruments that cost around £1,000 that read velocity directly (they measure the rate of cooling of a heated probe), but i think it can be done much more cheaply with e.g. a Dwyer magnahelic gauge and some accessories (pitot tube set up etc): http://www.dwyer-inst.com/Products/GageApplications.cfm

It'd be worth talking to Dwyer UK about what we wanted to do, as they have lots of options to make these measurements.

It's possible too to do it even more cheaply using a U tube full of water, but i'm not sure how practical/robust it would be.

This is the best way to check what cfm your system is really delivering, it's also the way to properly check the state of your filters.

Thoughts anybody? Interest?
 

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