Should WW Forums have a position on dust hazards and practices?

[Gunnaduit]

Mike,

I really think you do Bill's work a disservice by dismissing his observations and calculations as unscientific. Surely at some point the results of testing via measuring air quality, air flow and pressure over a number of systems can be recognised as compelling evidence.

In kindness, may I say that I think it is BP who is doing a disservice to himself. The old saying:" extraordinary claims require extraordinary evidence". He has no citation references, and simply says "believe me, I've got 3 engineering degrees". Said the chief engineer at Chernobyl to the Kremlin. Why should anyone believe anyone based on personal authority claims? How the hell he got 3 engineering degrees without having the discipline to provide citations is beyond me. In the real world of evidence-based research, it is simply not acceptable. He would never be published in any peer-reviewed journal. If what he has to say is true, and it may well be, his writing habits totally ensure that he remains a dweller on the engineering fringe, in the next tent to the perpetual-motion nuts. What a pity.

It is great you say that there have been tests of a number of systems. I'd like to see the data. Not to pick holes in it, but because I always tend to look at data - as long as it is well presented - before drawing my own conclusions - at least about things I have an interest in. Again, why not present the data if you have it. The results ought to be tabulated and set on the web site. If it isn't reported, after all the effort of collecting it, it sort of looks like maybe it didn't support the case. It all comes back to how you mount a case: through evidence, or through assertion.

BP's website is guaranteed to build skepticism even among the sympathetic. Personally, I would never present information in the way he has. If you look at that Wikipedia page I've drafted, you'll see my style. Support every truth claim that you can. Either with literature citations, or if need be in other circumstances, test results (as in engineering research) or presented calculations (as in a design documentation). That's how it is done everywhere, long live science. I can't believe that with stuff as important and as widely discussed as this, it all rests on a most idiosyncratic old gent without any form of (published, evidence based) corroboration.

I am not attempting to pull the house down. I have been quite prepared to give BP the benefit of the doubt, reserving judgement until I could dig deeper into the literature out there, and in the meantime argued quite vigorously for a faq.

But I am pointing out how very far from acceptable the BP website is in terms of the norms of evidence-based truth claims. The practical upshot is, has all the appearance of a website full of nostrums. What a pity, as it may be important. But who would know without a leap-of-faith, a trust-in-me usually now relegated to the religiously inclined.

Because I have given him the benefit of the doubt, and do think he raises enough concerns to look into it, I took the time to build the Wikipedia page to provide the discipline and the references that BP hasn't. Unfortunately, I am finding that a lot of it can't be backed up, at least by my own many hours of trying to hunt down literature that would fit his, er, journalistic ramblings. I am not being frivolous in this, I am not in some political or ideological sense opposed to BP, I am investing good time and effort in good faith, this is a service I am doing, not a disservice, but I find it all quite frustrating.

[Groggy]

Its a pleasure. I hope that it is becoming apparent why the earlier suggestion of moderators editing content would have proved to be impractical - we simply don't have the knowledge or time. I happen to be sitting in a hotel in Brisbane at present with little to do as my work link is broken, so I can spend a little time tonight.

At some stage I'd like to get the FAQ on a large monitor and sort it out a little, maybe group the content somehow. Until then I'll just 'chuck' stuff in until the ideas slow down. Then we can focus on getting good quality links and better, more concise, wording of each factoid (is that what they are? Seems appropriate).

[Sturdee]

If the FAQ is too detailed it won't be read.

I agree. I have been reading both threads on this subject and I'm giving up on it because this is getting way too heavy and hard to read.

Over the years I have designed and installed three Triton dust bucket mini cyclone conversions to use with vacuum cleaners in outside soundproofed boxes, a cyclone powered by a DC outside the workshop with inline booster motors connected with 4 " ducting to most machines. Not perfect but affordable.

So if it becomes too hard to read for me think of a newbe who comes along. He will immediately ignore it, so unless it can be simplified you are wasting your time.

My suggestion is to use the old KISS system.


Peter.

[Chris Parks]

My suggestion is to use the old KISS system.


Peter.

Which is?

[Grandad-5]

So if it becomes too hard to read for me think of a newbe who comes along. He will immediately ignore it, so unless it can be simplified you are wasting your time.

My suggestion is to use the old KISS system.

In most aspects I would agree with your sentiment Peter, but speaking as one who has never seen a health need for DC I must say that the shear quantity of information on these two threads and the obvious dedication that so many here have of getting the word out has made me stop and think about this issue for the first time in my life.

This flooding of info probably wouldn't work for most newbies to this issue but I'm looking forward to the FAQ and the Wiki article as two definitive places to start research when the day comes that I turn my mind to doing something for myself

Jim

[Grandad-5]

Which is?

Old army adage...Keep It Simple Stupid

[Chris Parks]

Old army adage...Keep It Simple Stupid

I am aware of what it means, what I would like is Peter's version of KISS as applied to dust extraction.

[Grandad-5]

I am aware of what it means, what I would like is Peter's version of KISS as applied to dust extraction.

Sorry, my mistake
Jim

[Bushmiller]

I don't think you should hold out too much hope of converting everyone. However that's not really the point and you can't please everybody.

A straight forward FAQ with concise answers to whet the appetite and a list of further reading by reliable, non-controversial sources for those that want more information seems to me the way to go. It is intended to reach the uninitiated and those who have never considered sawdust to be a problem in the past. I'm sure I have swallowed a whole tree (well, not a whole tree as such), but a tree's worth of sawdust in my time!

Don't forget (not that you would for a moment) that we have a a whole sub-forum dedicated to Dust Extraction. There is plenty of reading there .

I would like to add my thanks to Groggy for taking on the task. You must be starting to wonder about the old soldiers adage about not volunteering for anything.

Regards
Paul

[BobL]

My suggestion is to use the old KISS system.

Unfortunately best practice dust collection is neither simple or cheap.

95% of wood workers want to be able to walk into a store and purchase an "out of the box solution".
The only out of the box solution for power tools is an expensive vacuum cleaner, everything else "requires a lot of work". For most woodworkers the idea of spending a grand on a vacuum cleaner to provide dust control on a $40 tool is out of the question.

Which is why large numbers of cheap vacuum cleaners, 1 and 2 HP and ineffective 3HP systems and lengths of 4" flexy are sold. At the low cost DIY end of things, endless numbers of ineffective: home made dust catchers, dust deputies. small cyclones and dual switching switches just make things worse.

Locating a DC outside and setting up 6" ducting is either too hard or not possible and more importantly few small DCs have the intake port size or air speed that can benefit from 6" ducting. How many woodworkers are prepared to buy a new 2HP DC and commit some major mechanical surgery on it?

Even those with $$ that can afford a 3-4-5 HP DC still should locate it outside a shed but it does not end there I cannot think of a single woodworking machine under a couple of thousand that has adequate ports so machine level modification is required. How many woodworkers are prepared to do that?

The few simple messages we can promote are things like
1) provide lots of natural ventilation but how many woodworkers are prepared to do that when it is 0ºC outside?
2) Put pedestal fans at openings on opposite walls of a shed (see 1)
3) External DC locations should not vent near major openings to the shed but outside the opposite wall to the major opening.
4) Throw the dual switching switch away and run any externally venting DC for at least 30 minutes after the dust making activity

Everything else is not KISS.

[mic-d]

IF you accept the premise that 150mm/6'' is the minimum for good DE

This is not the premise at all, nor is it Bill Pentz who worked it out.
The premise is that dust is bad and should be controlled. You might have come to that conclusion by reading the medical references, a, b, c, on the dangers of wood dust or the original workers may have been prompted by anecdotal medical evidence or just to minimise nuisance dust etc.
The work that led to 6" port/duct size was done long ago (the references are in the dust control handbook). First, to prevent dust settling in ductwork, a minimum velocity for wood dust of 3500-4000FPM is required. This is quite easy to understand and obvious that you can work it out by dialling back the velocity until dust starts settling, then give it a margin and you end up at that number. The other number is the volume of air required to capture the dust in an exhaust port. That number for wood dust (the references are also in the dust control handbook) is 800-1000CFM. If you divide the volume of air by the velocity you end up with the cross-sectional area of the port/duct required to get those two parameters. So: 4000FPM/800CFM = 0.2square feet = 28.8square inches ~ 6" round port/duct. I can understand that, it's simple. Surely that is the best way to explain the best duct size and I don't think it would scare a 'newby' away

It's a no brainer - they are too small. Given a 6" minimum ducting is needed using standard types of DCs, placing any sort of 4" orifice in the way immediately compromises the flow rate. There's no sums or calcs needed.

Ian, got to your local plumbing suppliers (Bunnings don't carry 150mm) and ask for two bends in both 100 and 150mm and have a look at the huge disparity in size. Then it becomes obvious that 100mm is just too bloody small for dust extraction.

I self-edited my previous post about these three quotes but really actually I don't think there's anything wrong with it. These quotes are why I think you'll lack credibility, they all ask you to believe, like it's a religion. The last quote is ridiculous. You might as well say to me, Michael open your mouth, look what a big gob you've got, now look at your nostrils, see how obvious it is you weren't meant to breath through them! It's only because I can immediately test your assertion that I can assess the suitability of them to the task.

By the by, I'm not convinced that even hoods with 6" ports will capture all the dust generated from fast-spinning woodwork machines. I think that figure of 800-1000CFM was based on capturing dust from a falling stream of dust, not ejected at high velocity. If you accept the premise that invisible dust acts much like a gas, then if you cut some timber and can smell it, you are also breathing in wood dust. This is why I would favour a multi layer approach to dust control, eg put the DE outside, cross ventillate, wear a mask etc etc.

[BobL]

I started doing this chart some time ago but Sturdee's post prompted me to finish it. It's as simple and brief as I can make it.



If anyone has ideas for improvement I am happy to consider them.

[Sturdee]

I started doing this chart some time ago but Sturdee's post prompted me to finish it. It's as simple and brief as I can make it.

.

Bob, that's exactly what I mean with the KISS principle.

A brief question followed with a simple answer (maybe expanded to say 2/3 para) with embedded links to other articles on the forum explaining it in more detail for those that want such detail.

In other words a very simple FAQ with simple answers linking to a series of separate posts with progressively more detail to satisfy those that need it.


Peter.

[BobL]

By the by, I'm not convinced that even hoods with 6" ports will capture all the dust generated from fast-spinning woodwork machines. I think that figure of 800-1000CFM was based on capturing dust from a falling stream of dust, not ejected at high velocity. If you accept the premise that invisible dust acts much like a gas, then if you cut some timber and can smell it, you are also breathing in wood dust. This is why I would favour a multi layer approach to dust control, eg put the DE outside, cross ventillate, wear a mask etc etc.

A minor point, but I always thought 4000 fpm was based on the ability to re-suspend settled dust inside a duct. This is because all systems will stall at some point thus some dust will settle inside the duct. If the re-established air flow cannot re-suspend the dust then this will reduce the air flow carrying capacity of the duct and lead to a dust build up and eventual blocking of a duct. This is a big problem when a horizontal pipe goes through a 90º bend to a vertical since during a stall all the dust held in the vertical pipe falls to the bottom of the vertical duct.

I thought the 1000 cfm was based on collecting a hypothetical half bubble or hemisphere of air radius of about 3 ft every second from the dust making area. This translates to a linear air speed at the edge of the half bubble of ~30 km/hr which too slow to capture some dust. This more of a problem for big chips which are not health issues but what is not understood is that invisible dust on or close to the big chips will ride long with the big chips and big chips smashing into surfaces and each other will make small chips.
In practice this 3ft hypothetical half bubble is rarely achieved at the cutting site because;
- machine ports are too small and cannot sustain the 1000 cfm
- dust/air collection openings on the machine in the vicinity of the cut are too constricted
- the cutter sets up non-uniform speed air currents that are in excess of 30 km hour at the edge of the 3 ft bubble
- the wood being cut impedes the air flow.
Nevertheless it is a target bubble rather than a practical bubble

This is why in addition to the multilayer approach describe above it is essential to keep DC running for some time after dust making activity.

It would be very interesting to map real air speeds and particle distributions inside this bubble while real dust making activity takes place. Something else to do when I retire.

[mic-d]

I like the chart Bob, it's a good way of displaying info. Minor point but makes sense. The reading I've done attributes it as I described, perhaps I'm reading oversimplified text Either way, if we want to try and KISS, it's a simple explanation that describes the derivation of the 6" minimum duct/port size, without resorting to witchcraft or the 'it is because it just is' explanation.

*just for Bob*
If a system has stall points or eddies where the dust will fall out it is always going to fall out isn't it? If a small pile of dust settles out it will grow and be moulded by the dynamics of the flow in that section until it reaches an equilibrium with the 4000fpm boundary and then it shouldn't grow any more. The velocity in that area of constriction would increase too and help to limit the amount of buildup. If it continues to grow because flow is reduced by constriction (and if it's not because of a fundamental flaw in the duct design) then you've done something wrong with the dust extractor choice, not because the duct is too small haven't you? I have 4" to 6" to 8" duct. I reckon that around some of those transitions there are small build ups of dust, but they've never grown to block the duct.

A minor point, but I always thought 4000 fpm was based on the ability to re-suspend settled dust inside a duct. This is because all systems will stall at some point thus some dust will settle inside the duct. If the re-established air flow cannot re-suspend the dust then this will reduce the air flow carrying capacity of the duct and lead to a dust build up and eventual blocking of a duct. This is a big problem when a horizontal pipe goes through a 90º bend to a vertical since during a stall all the dust held in the vertical pipe falls to the bottom of the vertical duct.

I thought the 1000 cfm was based on collecting a hypothetical half bubble or hemisphere of air radius of about 3 ft every second from the dust making area. This translates to a linear air speed at the edge of the half bubble of ~30 km/hr which too slow to capture some dust. This more of a problem for big chips which are not health issues but what is not understood is that invisible dust on or close to the big chips will ride long with the big chips and big chips smashing into surfaces and each other will make small chips.
In practice this 3ft hypothetical half bubble is rarely achieved at the cutting site because;
- machine ports are too small and cannot sustain the 1000 cfm
- dust/air collection openings on the machine in the vicinity of the cut are too constricted
- the cutter sets up non-uniform speed air currents that are in excess of 30 km hour at the edge of the 3 ft bubble
- the wood being cut impedes the air flow.
Nevertheless it is a target bubble rather than a practical bubble

This is why in addition to the multilayer approach describe above it is essential to keep DC running for some time after dust making activity.

It would be very interesting to map real air speeds and particle distributions inside this bubble while real dust making activity takes place. Something else to do when I retire.