Thread: Want your DC checked for invisible dust?

Damkit Bob, wished you lived in Melbourne, have you over in a heartbeat.

Cheers Fozz.

200 viewers of this and the same thread in the the Announcements Forum and only one person has availed themselves of the opportunity. Like I said in the other thread, maybe I need to change my deodorant?

Just out of interest Bob are you planning to use your data for a publication on the subject?

Stinky

Bob your armpits are not the issue for me at all. It is the Pacific Ocean between us that keeps me from availing myself of your offer.

Pete

Originally Posted by QC Inspector

Bob your armpits are not the issue for me at all. It is the Pacific Ocean between us that keeps me from availing myself of your offer.

Pete

I dont know Bob's armpits either, its the Nullarbor Plain for us Wise Men from the East - otherwise I would have responded in a flash

Regards

Peter

Originally Posted by Sir Stinkalot

Just out of interest Bob are you planning to use your data for a publication on the subject?

Stinky

I wasn't, but now you mention it, I might think about doing so. I have seen very little published on the dust capture performance of DC's, especially those that are actually in use by hobby level woodworkers.

The thing that concerns me is that the OHS occupational dust limits of 5 ppm for softwoods, 1 ppm for hardwoods and recommended 0.3 ppm for MDF are only providing part of the story. While the invisible dust only represents a minor fraction of the dust mass they usually represent a substantial fraction of the particles and the ones that can penetrate furthest inside respiratory systems.

Bob I notice you have at least one other interested person in Melbourne, Dont know why perth arent interested. Would it be viable to post your instruments to Melbourne for us to take the readings for you? We could pass them round and send them back when finished and all pay a share of the costs, unless you intend to profit from the data then it would be more appropriate if you pay the costs and we provide the data.

I know there may be some issues from your perspective on integrity of data if you dont take it yourself but maybe having two members present to ensure your instructions for consistency are followed (as we pass the instrument from member to member maybe) may be a solution. I guess its up to you and your intended end use of the data. either way, as long as it is reasonable you can count me in.

Doug

Originally Posted by doug3030

Bob I notice you have at least one other interested person in Melbourne, Dont know why perth arent interested. Would it be viable to post your instruments to Melbourne for us to take the readings for you? We could pass them round and send them back when finished and all pay a share of the costs, unless you intend to profit from the data then it would be more appropriate if you pay the costs and we provide the data.

I know there may be some issues from your perspective on integrity of data if you dont take it yourself but maybe having two members present to ensure your instructions for consistency are followed (as we pass the instrument from member to member maybe) may be a solution. I guess its up to you and your intended end use of the data. either way, as long as it is reasonable you can count me in.

Doug

Hi Doug,

Thanks for your good intentions to help me get some data. I'm not intending to derive anything financial from these measurements. However, given the instrument costs ~$10k, is moderately delicate and that it does not belong to me but to my work and for these measurements I am financially responsible for it I can't see shipping the instrument around as a current option. The way the background readings are taken are also pretty critical in the measurement process.

I do have another scheme cooking that I need to test.

I may even bring the instrument with me when I next go to Melbourne and take a few measurements while I am there.

Cheers
Bob

Just read this now, yeah why not, sounds good Bob......

Originally Posted by BobL

Hi Doug,

Thanks for your good intentions to help me get some data...
Cheers
Bob

No worries, Bob. I had a feeling the offer was a bit of a longshot but I am all behind any effort to help us understand our workshop environments so that we can manage the risks sensibly. Keep up the good work.

Doug

Hi Bob, I would have expected you to get the 10 pretty quickly, good oppourtunity to see first hand the performance of the the owners DC system, I'd certainly be interested but unless your coming to Rocky
The results will be interesting to see if it gets that far.



Pete

If you live in WA I think you would be crazy not to have Bob pay a visit... Unfortunately Perth is a little too far west for a Sydney home visit.

I have managed to get a dozen volunteers to partake in this study and I did my first yesterday. I was going to wait until I have all or most of the results in but there was something that I found yesterday that is worth sharing and that is the performance of budget priced vacuum cleaner. While it was much cleaner that I expected while it was free running it is the first time I have put the particle counter on such a vacuum cleaner. Also shown is the performance of the subject's 2HP DC with well seasoned needle felt bag, as well as the results for my DC.


The budget vacuum cleaner is struggling to filter the finest dust even in the bigger sizes it only manages ~75% efficiency.

The other thing I measured was the dust levels coming out of the vacuum cleaner while it was connected to a ROS sanding some softwood.
This combination was outputting from the outlet of the vacuum cleaner about 0.045 mg/m^3 per minute.
Thus in just over 2 minutes it would already be exceeding the European OHS standard and in ~20 minutes would exceed Aussie OHS hardwood standard.
BTW this test assumed 100% collection efficiency at source which it clearly wasn't able to do as there was visible dust present around the wood and sander.

This demonstrates nicely the two big issues in DC
1) Catching the dust
and
2) Filtering the dust

It may not seem like there is much difference between a 75% efficient filter and a 95% filter but for operators that cannot vent outside a work area the ability of filters to handle realistic dust loads really does require as high an efficiency as possible. I have prepared a (possibly over complex) graphic to demonstrate this but I will not load this particular post up with this level of detail.

Hi Bob, looking at the graph and just so I/all understand it, taking the first point of the Vac, looks like it means that ~35% of particles in the range 0.3 to 0.5 were captured and therefore ~65% not captured and the second point for the Vac ~65% of the 0.5 to 0.7 were captured and ~35% not captured, etc.etc

Is that how we read it? If yes it shows that the small particles are the hard ones to collect!



Pete