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26th November 2012, 11:39 PM #91.
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How not to use a vacuum cleaner
I have been continuing to make a number of dust measurements in woodworkers sheds but haven't been posting results mainly because there has been nothing much new to report.
Most DCs are working well (even the crappy cloth bag models) but the testing has continued to identify problems with VCs and how they are used.
I have also been working with owners in replacing and retesting VC filters with mixed success.
What is starting to emerge is how unreliable vacuum cleaners (irrespective of price) are at fine dust filtration.
Some of this seems to be inherent to the VC itself and sometimes it is how the VC is used or some combination of both.
Of the 15 VCs I have measured only 5 demonstrate any filtering of the finer dust particles.
The quality of the filtration is poorly correlated to VC price but may to be correlated with VC age.
10 of the 15 VCs make more (as much as 100 times more) fine dust than is present as background dust in their respective sheds (most sheds have similar background levels)
Of the 15 VCs I have tested I would personally only consider using one in my shed (and it is not a premium model).
Here are examples of 2 premium quality VCs (VC! & VC2) that generate up to 24 times more 0.3 - 0.5 micron dust than is present in the shed background.
VC1 and VC2 are similarly branded, but not the brand that would come to mind first up to most woodworkers.
VC3 is an example of the results from a premium VC maker (the one most people would normally think of) which also has problems although they are not as bad as VC1 or VC2.
BTW - The problems with VC3 have been improved but not as much as I had hoped, by a filter replacement.
VC2 is used inside a router table/cabinet (See Diag below) and connected to the router chamber by a short length of VC hose.
The only way the air exiting the VC has of escaping the chamber is for the air to fill the VC chamber and leak out through the narrow gaps around the door.
Any dust that exits the VC2 filters ( arrow A) is able to be grabbed by the motor cooling circuit which will then mince this dust (Arrows B) into even finer dust filling the chamber with fine dust .
Because the air finds it difficult to exit the the VC chamber this will also throttle the flow allowing more time for repeated mincing of dust.
The VC and the cabinet were highly contaminated with fine invisible dust so much so that it was streaming from the gaps around the door into the shed even when the router in not cutting anything.
The owner had no idea what was going on as the VC effectivley collects chips and leaves no visible dust behind in the router chamber.
The situation was so poor I thought it was worth posting this as a way not to use a VC.
A solution is to actively vent the VC chamber using a DC that vents to the outside, but in that case the VC is redundant and venting the router chamber with a DC would provide greater flow.
VC1 is connected to a mitre saw. I have no explanation for the poor performance of this VC other than the filter being damaged and have advise the owner to replace the filter.
The problem with ALL VCs is that unless they are regularly tested with a particle counter it is impossible to tell if they are working properly so while they may well start out fine they could drop the ball at anytime and the owner would never know they are contaminating their shed. At least with a DC vent the DC outside is a possibility.
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27th November 2012, 01:10 PM #92GOLD MEMBER
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Just a heads up on particle counters. I received an email the other day telling me that Clearvue in the US will be selling Dylos particle counters so I will, be able to stock them as well. As yet no pricing or stock but I will let you know those details when I can.
Air Quality Monitor $199CHRIS
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27th November 2012, 05:18 PM #93.
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28th November 2012, 03:38 PM #94
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28th November 2012, 05:41 PM #95.
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3rd March 2013, 04:35 PM #96.
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Now that I'm retired I have more time to get back to doing some dust testing.
Today I tested a DC with a PF, and a high end VC connected to a small cyclone (SC).
The DC had a number of leaks in the plastic bag and around the rim of the DC housing.
This probably explains why the PF is not working quite so well a other PFs I have measured.
Just a reminder that negative efficiencies (shown in %) mean the device is making more dust than it is collecting.
The result for the VC alone is typical of most (even expensive) VCs - ie making more of the finer dust than they collect.
The interesting thing for me was the effect of the SC.
While it improved the efficiency of the collection of dust above 5 microns it generated more dust for all of the other sizes and especially so for the two smallest particle size ranges. In addition these devices reduce flow so fewer fine particles are grabbed at source.
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3rd March 2013, 10:28 PM #97... and this too shall pass away ...
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BobL,
Took a look at the Dylos particle counter. It seems to measure only two sizes of particles.
You, on the other hand, have readings of a range of sizes.
What kind of instrument are you using?
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3rd March 2013, 11:05 PM #98.
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I'm have been using ARTI and a Met 1 particle counters.
Both have 6 particle size ranges and they cost about 5 grand in Australia
The dylos units have 2 ranges they say cover moulds (>0.5 microns ) and pollen (>2.5 microns)
To perform accurate determinations of dust loadings per unit volume you really need a 5 and preferably 10 micron discrimination.
To understand what is happening the finest particle space it is handy to have 0.3 and 0.5 micron discrimination.
Hence a minimum number of channels I would work with is 4.
The dylos units are more than adequate for detecting leaks in systems and getting a general picture of what is going on inside a . But 95% of the leaks I see one does not need a particle counter for. Today I could see two leaks on the seal between the plastic bag and the DC and two holes in the side of the bag. I find it hard to believe that there are so many leaks in systems
One problem with the Dylos is that they do not provide sampling volume value - all they say is the sampling volume is equivalent of a 12 year old resting breath but they do not say what this volume is. The reason for this is probably because to perform accurate volume readings the pumps need to be calibrated about every year. Uncalibrated pump volumes means the counts reported are OK for relative work - ie compare readings made by the same unit but readings on different units cannot be accurately compared, and neither can any reading be converted to mg of dust per cubic m of air to establish OHS dust values.
Despite I think this they would be worthwhile gizmo for say a mens shed. I have seen a few people buying these and reporting their use in Blogs that demonstrates they have no effin clue about what they are doing. For example they get very high readings in their home and lower readings in their shed so they reckon their sheds are OK. The BIG difference of course is that their home is full of skin, hair, combustion products, and fabric dust - which most humans have been living with for hundreds of thousands of years, but their shed is full of wood dust - there is a big difference.
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9th March 2013, 01:39 PM #99.
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Industrial DC performance
Yesterday I tested a brand new type industrial DC.
3 Phase 5.5HP,
Pleated filter with 20 m^3 surface area (equivalent to about 3 regular cylindrical PF).
400 L chip collection with forced positive pressure sealing of bags
<0.1 mg/m^3 dust emissions.
The owner is a hobby woodworker who owns a 170m^2 factory unit to house his high quality machinery.
Even though it is an industrial location he cannot vent outside.
The DC is fully ducted to 10 machines (TS, 2 x BSander, 2 x BandS, Jointer, Thicknesser, Downdraft table, router table a SCMS) using a mix of 8,6 and 4" metal ducting.
The ducting cost about twice the cost of the DC.
Although I did not measure the flow rates, they are mostly very high so I guess it will have excellent capture at source.
While it easily meets it's rated 0.1 mg/m^3 specs, in terms of fine dust filtering the filter performed slightly below the average of the 12 PFs I have measured thus far.
I suspect it will perform better once the pleated filter is conditioned and being ruggedly built should be less susceptible to leakage issues.
A Clearvue and PVC ducting would have been IMHO been a MUCH better choice
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9th March 2013, 02:18 PM #100GOLD MEMBER
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Will this be tested again after some use? I hate filters, they are a band aid solution at best and it is my gut feeling that the area of filter calculated to do the job should be doubled on any installation to slow down the air and debris hitting the filters. I would go to extreme measures to eliminate their use on any installation given the choice.
CHRIS
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9th March 2013, 03:12 PM #101... and this too shall pass away ...
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I envy this guy's workshop ... but am glad I don't have filters ... the other benefit for which I am forever grateful is the small footprint of the Clear Vue.
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9th March 2013, 04:31 PM #102.
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I hate filters, they are a band aid solution at best and it is my gut feeling that the area of filter calculated to do the job should be doubled on any installation to slow down the air and debris hitting the filters. I would go to extreme measures to eliminate their use on any installation given the choice.
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9th March 2013, 05:11 PM #103GOLD MEMBER
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Avoid the need for filtration is my answer. dealing with wood dust this is possible other media can present problems but I don't deal with that apart from one instance and that is outside the reference of this forum.
CHRIS
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12th March 2013, 03:32 PM #104GOLD MEMBER
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This has been an interesting thread. I hope BobL keeps posting.
As an aside, I now feel much better about the central vacuum system I installed in the house during renovations!
The hose takes up as much room as a normal vac and can be quite unwieldy.
However, the central unit is located behind the garage, so any leaks are well away from the living area.
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