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Measurement of fine filters and blinding

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RogerS

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Regular readers will recall odd comments from me regarding my suspicion that my Axminster 2200 chip extractor wasn't giving me as much 'suck' as I seemed to remember. At the time, it was the extractor for everything in the workshop including dust generators like the table saw. At each bag change I would give the fine filter (from RB Industrial) a bit of a bash to dislodge any dust. I even went as far as taking the fine filter outside and using my SDS hammer drill on hammer and managed to fill half a bucket with fine dust.

I experimented briefly with a large cyclone front-ending the Axminster and while it clearly worked, like many others I am in that halfway house between needing a larger installation and the relatively low volumes of dust/chips created by the occasional user. I sensed that I'd be forever emptying that oil drum. Plus the lack of space for the cyclone as well. So I compromised and got a secondhand Camvac to take the dust from table saw, drum sander etc leaving the Axminster to take chippings from the planer/thicknesser and spindle moulder. So far so good.

Now having bought a brand new fine filter I wanted some sort of metric or measurement/benchmark that I could use to see when the filter needed replacing. I bought a cheapie digital manometer off eBay and after a lot of confusion on my part and with a huge amount of help from Chris (siggy_7) I learned that what I needed to do was measure the pressure drop across the fine filter. The lower the pressure drop, the cleaner the filter.

So I siliconed a small tube into the bag below the fine filter - effectively sampling the pressure after the motor but before the fine filter. The other input was to the atmosphere. Turned on the Axi and measured -15 (units were cm of H20). Switched off. Gave the filter a good bashing with my hands. A lot of fine dust fell out and into the bag although one's never sure if this dust is coming from the metal ramps inside the extractor housing or from the filter.

Turned on the Axi and got measured -10. Proof how effective a good bashing is.

Next, I removed the old filter and out of curiosity weighed it...9 kg. I then weighed my new filter and that was 5.6kg. So, assuming, that the filter construction is the same, that means 3.4kg of dust is up there and in the filter. So the filter is doing it's job very effectively, it would seem.

Replaced with the new filter and fired up the Axi. Measured -1.4 and so now I have my benchmark reading.

I'll be interested to see over what sort of timescale it will start to clog up (blind) again as the p/t and s/m still generate some dust. At least, I have some way of measuring where the filter is in it's life.

Now I need a way to measure flow through the pipe and see how that reduces over time and also to explore the reduction in 'suck' with various configurations of pipe connection, Y-pieces and blast gates etc.
 

Pete Maddex

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Hi,

I have hoovered mine several times, it comes up much cleaner, and a wash in a bucket after hoovering helps as well.

Pete
 

Eric The Viking

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I turn the bag inside out, fit the 'blow' hose to the vacuum, stand upwind in the garden, and blow through. The wood dust quickly degrades in the soil, so I can't see there's a problem. It seems to work well for the cylindrical fine filters in the vacuum too, after a thorough bashing and brushing over first.
 

Lord Kitchener

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Worth remembering that how well a filter flows is a big part of the story, how well it removes particles of dust is the other, and a good coating of dust on the filter will actually help that rather than hinder it. Personally I would not be to assiduous in my filter cleaning for precisely that reason.
 

theartfulbodger

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Thanks all for your responses to another daft question!

I've just purchased a new to me Axminster model 310451 extractor. It has a fine bag fitted to it and a "normal" bag still in its packaging.

I'm guessing it's a balance: less filtration means more airflow...which in turn might mean more "suck" if using a plumbed in system with pipes and ducting' and result in more filtering due to the higher airflow?

If that makes any sort of sense #-o


Stand by for more daft questions re home made ducting :mrgreen: I saw a tumble drier venting kit in a big orange shed earlier and it got me thinking..
http://www.diy.com/diy/jsp/bq/nav.jsp?f ... egories%3C{9372015}%2Fcategories%3C{9372046}%2Fcategories%3C{9372182}%2FspecificationsProductType%3Dtumble_dryer_condensation_kits&icamp=ns_5
100mm diameter as well :ho2
 

RogerS

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Artful, been there...it's not such a silly idea! I use some of the rectangular ducting and some 90 degree bends and converters to round that gets the 4" extractor pipe up to the back of the bench with my mitre saw. I've also got some very thin (but it works) tumble dryer hose connected to my small thicknesser. Seems to be fairly robust.

Your link is broken BTW
 

theartfulbodger

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You're right about the link, sorry all.

I did think it looked a bit mahoosive when I copied and pasted it..

Wonder if this one will work?
http://www.diy.com/diy/jsp/bq/nav.jsp?a ... egories%3C{9372015}/categories%3C{9372046}/categories%3C{9372182}/specificationsProductType=plastic_ducting

it's item number 5020953930709
Manrose 100mm 2.5m Circular Aluminium Flexible Ducting & 2 Worm Drive Clamps £18.99
It might be a bodge ;) but it's a LOT cheaper than the "proper" stuff!
 

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