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

[mic-d]

Surely you must have thought 'I need a sign that says "this way up" '

The only sailient point in my whole post?

Both Bob and Mini have mentioned in recent posts about the problem of machine hamstrung by small ports. It is often raised as a major deficiency in DE and perhaps an easily remedied problem in many cases. Perhaps also an easily remedied solution if machinery manufacturers got involved. But Mini in a recent post has lamented how there is no interest in a change by manufacturers, and so how to get traction in this area? Well perhaps it is time to consider bringing the spotlight onto the school situation if that is what needs to be done to overcome the inertia This is what I was trying to suggest in my previous post. Anybody want to weigh in with cost/benefit on this?

[Gunnaduit]

the problem of machine hamstrung by small ports. It is often raised as a major deficiency in DE

I really wish there was some hard info on this. I do not count BP as hard info. BP has no references to any research, and if he has got his own calculator out to do the sums, he hasn't shown how (including a reference to an engineering text that lays out the rationale). The best BP can do for any of us is to provide a set of propositions that need to be checked out.

This has become even more clear to me having done the Wikipedia page
Wikipedia talk:Articles for creation/Health hazards and exposure control of wood dust - Wikipedia, the free encyclopedia
I still haven't found ready-made info of the sort that would inform about machine ports sizes and duct sizes. It really requires someone to work it out for a 'typical' shed/garage (or classroom) system. This is possible to do, but would be better for somone who is currently keen at this kind of thing. If nobody is able to help on this, well we're at the end of the road. Believers in BP the prophet vs BP non-believers, like in the dark ages before the advent of science. It irks me that this is the situation.

So is it really true that the ports are too small? Considering all relevant factors, who can say? Where is the independent assessment? There isn't one. There's only the BP way, or the highway. Very unsatisfactory state of affairs.

Bob, thanks for the statutory limit refs, I had them already, and put them into the Wikipedia page, where I have tabulated that info. Would be intersting to put in the Australian regs. Which AS number contains the limits you quote?

[Chris Parks]

IF you accept the premise that 150mm/6'' is the minimum for good DE and the further assertion that anything in the duct that goes below that size restricts it then you must accept that machine ports are too small. They are an integral part of the duct system even though they do not look like it. Air is drawn into and travels through the cabinet and hopefully carrying the airborne dust from the cabinet into the exhaust duct. This is why the air inlet port must match the extraction port.

[BobL]

I really wish there was some hard info on this. I do not count BP as hard info. .
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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. Not only are they much too small, opening the ports up does not always help. It seems to me like there has been very little effort into the design of dust ports on machines.
I would have no qualms about quoting BP on this.
When you put it into Wiki you can also write it as a strong possibility following on from the fact that 6" ducting is needed with standard DCs
or
What Mini said!

Bob, thanks for the statutory limit refs, I had them already, and put them into the Wikipedia page, where I have tabulated that info. Would be intersting to put in the Australian regs. Which AS number contains the limits you quote?

I Just found the 2011 version of what I talked about
WORKPLACE EXPOSURE STANDARDS FOR AIRBORNE CONTAMINANTS DATE OF EFFECT: 22 DECEMBER 2011
http://www.safeworkaustralia.gov.au/...ntaminants.pdf

Here is a reference to the WA govt recommendation :http://www.commerce.wa.gov.au/worksa..._wood_dust.pdf which also quotes the limit for MDF

The exposures are IMHO completely inadequate because they say nothing about particle size distributions. 5 mg/g of a normal distribution around say a mean of 25 and std-dev of 5 microns is vastly different from a 1 mg/g with a mean of 5 microns and Std-dev of around 2 microns.

[Chris Parks]

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.

[m2c1Iw]

I really wish there was some hard info on this. I do not count BP as hard info. BP has no references to any research, and if he has got his own calculator out to do the sums, he hasn't shown how (including a reference to an engineering text that lays out the rationale). The best BP can do for any of us is to provide a set of propositions that need to be checked out.

This has become even more clear to me having done the Wikipedia page
Wikipedia talk:Articles for creation/Health hazards and exposure control of wood dust - Wikipedia, the free encyclopedia
I still haven't found ready-made info of the sort that would inform about machine ports sizes and duct sizes. It really requires someone to work it out for a 'typical' shed/garage (or classroom) system. This is possible to do, but would be better for somone who is currently keen at this kind of thing. If nobody is able to help on this, well we're at the end of the road. Believers in BP the prophet vs BP non-believers, like in the dark ages before the advent of science. It irks me that this is the situation.

So is it really true that the ports are too small? Considering all relevant factors, who can say? Where is the independent assessment? There isn't one. There's only the BP way, or the highway. Very unsatisfactory state of affairs.

Bob, thanks for the statutory limit refs, I had them already, and put them into the Wikipedia page, where I have tabulated that info. Would be intersting to put in the Australian regs. Which AS number contains the limits you quote?

I have read this post several times and feel compelled to respond.

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.

FWIW I have built two cyclones and a ducting system based on Bill's recommendations and can attest to the basic premice that good dust extraction does rely on the factors he measures and that port size does dramatically impact airflow therefore dust extraction.

If you are not disputing Bill's findings but looking for further verification I suspect as you say you will be left unsatisfied. Who will conduct tests on a hobbyist DE system other than a hobbyist with the enthusiasm and dedication to publish the results for scrutiny to the degree that Bill has done.

My understanding of Bill's work is that he has identified the variables and points the reader in a direction that will provide good results based on his practical experimentation and testing not as a result of a set of engineering specifications.

Perhaps I misunderstand your post, as I said I've read it several times but still I'm wondering.

Regards

[BobL]

It is not possible to say straight off how many CFM will be lost or gained by doing something to your DC system.This is because changes to a DC system are dynamic and changing one thing will cause a number of other changes. Instead of changes to CFM it is easier to discuss pressure changes - some of these are fixed and some vary.

Let us start out by saying our DC generates a certain pressure in this case I have made it about 8" of H20 Pressure.

Here is a comparison chart calculated with Bill Pentz StaticCla.XLS showing what 8" of pressure can generate in a 4" and 6" ducting and the associated pressure losses covering a wide range of junctions and fittings.
The duct and flex pressure losses are per ft of length



In the middle and lower part of the chart is a set of pressure losses caused by a range of separators and bags and filters etc

Some observations.
1) Note the vast difference in CFM generated between 6 and 4" ducting. Although the FPMs are similar the 4" duct is a long way from meeting the BP spec of 1000 cfm at 4000 fpm
2) The pressure losses for various fittings and junctions are similar because I have fixed the total pressure loss but two stand out dramatically 4" duct and 4" flex are dogs. Avoid - Avoid - Avoid.
3) Trashcan separators and small basic cyclones are also dogs - learn to clean bags or buy a pleated filter

All this assumes that the machines being used have free flowing ports - I cannot think of a machine under $2000 that have these and even many above this do not have proper porting.

The best thing to do is download BPs staticcalc and try it for your self.

[BobL]

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.
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If you are not disputing Bill's findings but looking for further verification I suspect as you say you will be left unsatisfied. Who will conduct tests on a hobbyist DE system other than a hobbyist with the enthusiasm and dedication to publish the results for scrutiny to the degree that Bill has done.

I agree, BP is about as good as you can get at the moment and I would be happy to quote him despite is 'merican folksy style. I have had some minor disagreements with BP but I reckon overall he knows what he is doing and cannot fault a method or calc he presents. He has not done this all by himself. He has had a lot of expert help but he has been the driver of all this and without him we would be far worse off than we are.

[Bushmiller]

This type of discussion is always intriguing and to some extent unresolveable. The points I have picked up on are:

1. Be careful what you wish for.
2. Australia may have the highest level of regulation in the world (I haven't checked that.)
3. By all means make people aware, but leave the final decisions up to them. I suppose this is a develpoment of leading a horse to water, but not making him drink.
4. Many materials are considered carcinogenic, but are not neccessarily life-threatening.

I'd like to home in on that last point in particular in two ways.

A while back one of our managers (with a chemical background) boldy proclaimed there were no carcinogenic materials on site. One of my shift colleagues quickly denounced that statement and said "Yes there are. We have fuel on site." Well of course the manager looked up the MSDS for fuels and sure enough they are listed as carcinogenic.

Does this mean we will be unable to fuel our cars in the future? No, I think we are safe in that regard (for the moment.) So my point is to emphasise that the length of exposure to all this is important. (STEL?).

We go out in the sun, but every australian knows what is going to happen if you do that too often for too long.

Conversely, just because a substance is not carcinogenic, it doesn't mean it is good for you. In my industry we produce, as a waste product, ash and dust, which we are told are not carcinogenic, but breathing down huge quantities are definitely not good for you and in fact even small quantities are not good.

I think that the key is awareness and the FAQ that Groggy is organising via another thread will assist in dispelling many of the myths and inform woodworkers sufficiently to make their own decisions.

Possibly this thread and Groggy's FAQ (I appreciate that he is merely the facilitator for that thread) are not the place for detailed discussion of DCs vacuums, room filters, cyclones and the like. To my mind we are trying to establish broad principles.

Pneumoconiosis is real and you need to be aware. What you do about it once you have all the information is up to you.

Regards
Paul

[BobL]

2. Australia may have the highest level of regulation in the world (I haven't checked that.)
l

We have more or less the same as everyone else.

[m2c1Iw]

and I'm sorry if this sounds rude.

and so you should

And will no one reply to my previous two posts?

A brief response would be to highlight one of the assumptions Bill uses and that is most hobbyist systems will use small HP blowers so he deems power as reasonably constant whereas in a school environment who knows could be a 15hp blower driving the system.
DE is about airflow and the elements that restrict therefore machinery manufacturers could easily claim "you're using an undersized blower ya dill".

[Groggy]

Possibly this thread and Groggy's FAQ (I appreciate that he is merely the facilitator for that thread) are not the place for detailed discussion of DCs vacuums, room filters, cyclones and the like. To my mind we are trying to establish broad principles.

I agree. I am having a lot of difficulty with the big posts. If I delete them there is a lot of good information disappears. I'd prefer it if the detail is kept elsewhere so it can be linked to from the FAQ.

If the FAQ is too detailed it won't be read. I had some good entries today from Mini. We need a short statement followed by an authoritative link.

I am going to move some of the heavy detail posts into this thread so they are not lost.

[Chris Parks]

Groggy, concerning links for information. I find if I am reading something on the net links only disturb the flow of the read and learning. I realise that educational texts have to be linked but I would like to see links kept to a minimum. Of course that is my view and others may differ, that is what makes the world go round.

[Groggy]

Mini, I agree. I certainly do not suggest dozens of links like a bibliography or a scholastic piece.

I have been hoping to have the FAQ contain typical questions asked by woodworkers, provide a basic factual answer then support that answer with a link to a more authoritative source. A single link for each topic would be ideal, that way if the reader finds themselves interested they have somewhere to start.

If there are some topics where people might say there are no simple answers, then that is what needs to be said in the FAQ and a few links provided to get the reader started. Brevity and accuracy is king here.

[Chris Parks]

Groggy, I would like to thank you for the time and effort you are putting into this.