Found this while searching for cartridge filters:
Why Cartridge Filters are not suitable for Wood Dust | | Airtight Solutions
The situation is probably different with a cyclone removing the bulkier particles.
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Found this while searching for cartridge filters:
Why Cartridge Filters are not suitable for Wood Dust | | Airtight Solutions
The situation is probably different with a cyclone removing the bulkier particles.
It depends on the cyclone. Efficient cyclones that remove a significant fraction of the finest dust will maintain air flow for longer between filter cleanings.
Most wood processes actually produces relatively small amounts of the finest dusts but it doesn't take much of the finest dust to contaminate a shed above recommended safe levels, or to start clogging filters, so inefficient cyclones may not help as much as you might think.
Even when sanding, the mass of very fine dust (<2.5 microns) produced is typical in the low tenths of percent of the total dust produced, so for every kg of dust only about 1g of very fine dust is made. For sawing and planing the proportional mass of fine dust is very much smaller but of course the total dust produced is much greater.
I see this misconception all the time all the time with folks who use a third party cyclone and then a plastic bag collector and filter. After generating a plastic bag or drum full of chips they look into their plastic bag and see next to no dust in there so they keep going but don't realize the half teaspoon of fine dust that has come through the cyclone has been sucked into their filters and already started to build up and block them. This is why they see very little in their bags.
This means to always maintain max flow the filters still need to be cleaned after extracting every bin full of sawdust. Actual the bin should never be allowed to get more than ~2/3rds full anyway as this significant reduces the efficiency of cyclonic separation - if allowed to fill more than this, eventually most of the dust won't be separated at all.
What helps with pleated filters is a system that rattles the pleats internally on a regular basis.
But ultimately they have to be cleaned and its always a lot sooner than is thought.
But all this still misses the main point of why not to using a cyclone on smallish DCs. A cyclone may even be efficient at separating the fine dust that they suck up and keeping the filters clean but because small cyclones can seriously restrict flow on what are already below spec DCs, insufficient air and fine dust fails to be collected in the first place. This is why a cyclone like a Clearvue uses such as large impeller and large motor.
Will the Clearvue cyclone remove particles smaller than 2.5 microns?
Nothing removes 100% at any size.Quote:
Originally Posted by jack620
However, the Clearvue is is a fully optimised/integrated system where the impeller/cyclone and motor are all designed to work together to initially capture the maximum amount of air/dust flow, and then maximum separation of all dust by the cyclone.
In Oz, Clearvues are usually set up so they vent outside so the small amount of fine dust that gets thorough is not significant.
In North America where they are usually used inside workshops they use filters similar to the one you described earlier in this thread (99.99% at 0.5 microns) but the filters do not need to be cleaned anywhere near as often as those on unoptimised cyclone systems because the Clearvue cyclone separation at <2.5 microns is so efficient. The filters will generate a back pressure which reduces flow but the Clearvue is such a hulk is can afford to do this. Usually 2 such cartridges stacked one on top of the other are used to reduce back pressure
I never said it did. Where did you get the idea that I think that? Certainly not from my question, which doesn't imply that at all.Quote:
Originally Posted by BobL
Good God Bob, they should pay you an influencer's fee.Quote:
Originally Posted by BobL
How efficient? Do they give a figure for separation of sub-2.5 micron dust? Oneida says the Super Dust Deputy I have removes 99% of fine dust, but they don't specify what size that goes down to, which isn't very helpful.Quote:
Originally Posted by BobL
Sorry if that came across that way. I usually write things bearing in mind any newbies reading thisQuote:
Originally Posted by jack620
I would like to think so :D but not really ,and even if I was offered something I would not take it.Quote:
Good God Bob, they should pay you an influencer's fee.
I have had quite a bit to say about Clearvues on this forum and it's not always positive. For instance I don't like the way the Clearvue is promoted as the only way to guarantee a dust free shed. Its much more complicated than just just purchasing any machine. I just have to walk into my mens shed and see that the Clearvue has not been turned on for a couple of hours and some members have been using machinery with no pressure switch fitted and generated heaps of dust inside the shed. Clearvues are also overkill for small sheds or occasional woodworkers using small machines where a smaller (non-cyclonic) DC or even a couple of exhaust fans would be sufficient to reduce their overall exposure to fine dust.
Despite that, for a larger shed, with larger machinery, or a woodworker (especially turners) spending long periods in sheds then Clearvues are definitely one of the best solutions. When sheds get even bigger or bigger machinery is involved Clearvues may no longer be a solution.
The only spec I have seen is 99.9% removal at 5 microns but from what I have seen and read, in practice it seems to be more effective that this.Quote:
How efficient? Do they give a figure for separation of sub-2.5 micron dust? Oneida says the Super Dust Deputy I have removes 99% of fine dust, but they don't specify what size that goes down to, which isn't very helpful.
Typical production of <5 micron dust for a process like sanding produces is around 1% of total sawdust. For every kg of sawdust produced, this means 10g of <5 micron dust will be produced and the Clearvue will remove 99.9% of the 1g, or let 10mg through. 1kg of sanding dust is a large amount but easily possible with a drum sander, ND let's say this is generated in 10 minutes. During this time the Clearvue on 150 mm ducting will pump at least ~0.5m^3/s so over 10 minutes this is a total of 300 m^3 of air. In terms of the <5 micron dust concentration in the air, this works out to be about 40 µg/m^3 which while well below current OHS standards for wood dust but is about half way to the dust level set as safe for seniors and kids.
The above example is close to a worse case scenario but is why the ClearVue exhaust can be vented direct to atmosphere. <10 micron dust cannot be seen so provided it is sufficiently diluted and produced in shortish bursts it will not become a nuisance. Of course there are larger industrial machines and processes that produce a lot more dust and this principle simply won't work for these cases.
I'm not sure how long this will be able to be done as all dust producing processes will sooner or later get a fine tooth comb type going over and it would not surprise me if town councils banned this sooner or later.
With such a low level of fine dust output one might ask why can't Clearvue air be recycled back into a shed. The reason is of course that the dust accumulates/concentrates inside the shed so instead of 300 m^3 of air its the shed volume that has to be used. For a 6x6x3 m shed (~100m^3) the dust levels from one 10 minute session of sanding will now be 120 µg/m^3 AND it is still inside the shed, a second bout of similar sanding will double that etc.
BUT in terms of venting inside a shed the real headaches comes when there is a slight leak, or the bin overflows etc then the cyclone will spill its guts everywhere and make a real mess, send the shed air way over the OHS limit, and if fitted it will ruin a filter. Some people are indeed careful at checking for leaks and rigorously empty their bins etc and for folks that recirculate their air and use filters they have to do this.
Apart from not knowing the particles sizes considered, another problem with third party cyclones is we don't know what flow rates, and impeller size and HP was used for the test. Then, how applicable is their test to a different impeller/motor combo. Most commercial cyclones are older designs and not developed as an integrated product so its no wonder they perform so poorly. Most commercial DCs also use an incorrect flow rating standard so my take on any specs quoted by DC manufacturers is always guarded.
Can you tell I'm stuck inside with a broken ankle :(