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  1. #16
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    Hi Bob, I was using four cloth bags before and there was almost no back pressure with them when new, but after a year or so they started reducing flow after one hour of lathe work including fine sanding and it got worse after each clean. To measure Back pressure I would need something really sensitive like your latest project, I'm using a digital differential pressure unit the same as yours and it can not detect the difference with or without the Filters installed, it's been over 8 months since installing them and the amount of fine sanding my Wife has done in that time would have had the old bags dropping 3" of vacuum after a week if they were installed. With these big filters there is about 1/4" drop in vacuum measured with a bell mouth open intake and current appears to have dropped around 200ma in that time. I say appears because even though I can measure with the same AC voltage, I can't really compensate for temperature, humidity and atmospheric pressure which all effect a simple open port vacuum / current / voltage measurement, but using all three certainly gives me a better indicator of how the filters and system are travelling. I have a permanently installed combined Current - Voltage Power and running total consumption display unit, I think you have something similar.

    The old bags were starting to leak at the seams and in the end I decided to bin them - 6 years old.

    Mike

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  3. #17
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    Makes sense Lathe work is a killer on filters.

  4. #18
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    Finally a few photos of the Pleated filters added around 11 moths ago. This is a six year old photo of the new 3HP DC with cloth bags top and bottom.

    As stated previously, after a few years they were reducing air flow faster than ever. A single small bowl on the lathe with some fine sanding would reduce flow rate by around 5% and it would quickly decrease from there, I was cleaning the 4 filter bags every month. And the fine powder like dust passing through the bags meant that the cabinet had to be cleaned and washed out after the bags were removed to reduce the effect on my sinus, yes I was wearing a vapour mask during the cleaning process.

    How anyone can still run a DC with cloth filter bags inside a workshop is beyond my comprehension.

    BTW the top cloth bags in the first photo are the same size as the lower cloth bags.

    .

    When a good deal came up for two huge pleated filters I decided it was time. These Pleated filters are almost twice as high as the cloth bags, I had to add over a meter to the top of the cabinet and they only just fit in.

    Yesterday, 11 months after installing the pleated filters and countless hours of my Wife doing a huge amount of fine sanding and turning, I opened the cabinet to turn the filter cleaning paddles. The flow rate had only reduce around 2% in this time, and to my surprise (amazement) the inside of the cabinet was almost spotless, I had no need for a mask and turning the paddles did not result in any visible dust or dust mist in the air, my sinus did nothing. I closed the door and rechecked the current, vacuum and power consumption, all readings were back to as new.

    Below: The housing extends over a meter above the top of the door which is not even visible in the photo, hopefully gives you an idea of the size of these pleated filters.


  5. #19
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    Mike, how are you measuring the 5 and 2% ?
    Is this based on Vacuum?

    The visible dust present inside enclosures is most likely to come from 3 sources
    1) leaks are the most likely cause - even the slightest ruck or pin prick hole in a plastic bag can cause this.
    2) fine stuff getting through the filters
    3) dust escaping while emptying bags

    Your pleated filters sound like they are pretty efficient because none of the PFs I have tested have been more efficient than needle felt bags.
    This is a summary of all the stuff I tested a few years back
    RAF = room air filters, NF = needle felt bags, PF = Pleated filters, FFM = Full Face Masks, CG = cloth bags VC = Shop Vacs, RHS = refer to Right hand axis.
    Screen Shot 2019-04-05 at 9.05.31 am.png

    Of course PFs do have ~10% or more greater flow and take longer to clog up.
    After the 3 key equally important things of
    1) moving or venting yoaur DC outside the shed,
    2) Using 6" ducting, and
    3) Opening up machine posts,
    Using Pleated filters is one of the next most significant things to consider.

    Somewhat interestingly, after some 8 years of (light) use, the inside of my DC enclosure clearly has visible dust on the surfaces
    BUT
    the actual air that comes out of the enclosure is still considerably (ie >10 times) cleaner than external air.
    This suggests no leaks so the dust is adhering to surfaces and not being picked up by the escaping air.

    My take on it is that most of this surface dust comes from when I empty the bags as I don't bother to sweep or blow it clean every time - in fact I think I have only ever done this once.

  6. #20
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    Hi Bob, I mentioned a few time that for the past 6 years I have logged AC voltage + AC current, power and vacuum for the closest port to the Dust extractor. I have a base line of all ports closed, an open 1m length of 150mm intake to the DC as the maximum power input to the DC and therefore the maximum flow, what ever that may be. I'm not going to do elaborate real flow readings every time I want to get a rough estimate of the performance degradation of the system. Obviously if my DC draws 9A @ 240V at the closest logged open port, and that is almost identical to a 1M length of open intake, then I have all the flow I'm going get from this 3HP DC and impeller configuration.

    The needle felt bags would drop the current up to 3A as they clogged in shorter and shorter intervalís as they aged over the years.

    Needle felt bags may have more flow than pleated filters, and you obviously mentioned the larger surface area for a given comparable size, these two PF units are comparable in size to four NEW needle felt bags. The needle felt bags when new, and for the first year or two, would take a few months of fine dust before the flow got noticeable to the operator (me) at around 1A reduction in current for the same input voltage under almost the same conditions.

    After 9 months the current drop measured with these pleated filters is 200 ma, obviously sometimes less depending on the time of day, humidity and temperature. After using the PF paddles, that 200mm loss has disappeared. I ran the DC for around 20 minutes to see if the swirling mass of powdered dust in the bottom bags would return to the P-Filters and pull that 200mm back, but it hasn't so far. Thing is, I can't, and I doubt anyone can, physically detect a 200ma change at a machine, not without doing accurate flow rate measurements as has been discussed before in your posts. However I can notice a 1A change just by the sound of the intakes, that's why I have my rough power and vacuum measurement system permanently installed, I obviously start by checking all blast gates, then all ports closed, all ports open and reference running port power input readings before digging deeper to find the cause for any noticeable decrease in DC power input. Vacuum alone is totally misleading and for the most part near useless, but when it's combined and interpreted correctly with power input to the impeller, then I find the combination a quick useful tool for me.


    Somewhat interestingly, after some 8 years of (light) use, the inside of my DC enclosure clearly has visible dust on the surfaces
    BUT
    the actual air that comes out of the enclosure is still considerably (ie >10 times) cleaner than external air.
    This suggests no leaks so the dust is adhering to surfaces and not being picked up by the escaping air.

    My take on it is that most of this surface dust comes from when I empty the bags as I don't bother to sweep or blow it clean every time - in fact I think I have only ever done this once.
    The dust was like talcum powder, it could only be removed (from rough surfaces) with a wet cloth and some scrubbing. I dismantled and sealed all the leaks in the DC metal work years ago. Yes the dust was adhering to the surfaces of the enclosure, quite often it looked more like a stain on the surfaces.

    Yes, even with that fine dust inside the housing, there was normal air quality measured 2 meters from the exhaust, the amount of powdered dust inside the DC housing was more every time a few hours of very fine sanding was done. I was always extremely careful when removing the cloth bags, never done on a windy day and so on.

    When I have had a dust-leak in the lower bag seal I normally get a small wispy stain, but also larger dust particles around it. Even the grey metal DC housing looked like I had just cleaned it.

  7. #21
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    Quote Originally Posted by MandJ View Post
    The needle felt bags would drop the current up to 3A as they clogged in shorter and shorter intervalís as they aged over the years.
    The most I have ever seen it drop on one mine when it was 3HP was about 1A. However, I do realise your system sees a lot more sanding dust than mine and I think the ratio of sanding to other dust makes a big difference.

    It would be useful to know your currents and pressures with cleaned filters and all gates closed, and with all gates open.

    The pressures across my filters (which have not been cleaned or shaken for ~2 months) to atmosphere are
    1) Motor not running 11 Pa,
    2) Motor running and all gates open 85 Pa
    3) Motor running and all gates close 13 Pa.

    The fact that 2) is almost the same as 1) says there are very few leaks in the sections of ducting between the gates and impeller and the impeller and filters.
    The filter pressure drop 2)-1) = 75 Pa or ~0.3" WC. When I clean them I expect to see less than 0.2" WC.

    Needle felt bags may have more flow than pleated filters,
    PFs should have greater flow than NF.

    and you obviously mentioned the larger surface area for a given comparable size, these two PF units are comparable in size to four NEW needle felt bags.
    So they will have about an 8 times greater surface area. You won't get that much extra instantaneous flow because that will be impeller limited but they should take a lot longer to clog.

    I haven't done a lot of power measurements and what I have done I have not been able to make much sense of, over some 8 years. That is one reason why I've installed a sensitive pressure gauge. I've been to crook and weak to do much in the shed and haven't been able to make much wood dust so I can't do any real time testing.

  8. #22
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    Hi Bob, I must have read you post incorrectly with respect to NF and PF filters.

    Actually you may not remember but we have been over some of this before, but not since you made and calibrated your new differential pressure device. I have only tested with the same electronic manometer that you have.

    During testing of the 3HP DC, I removed everything from the Impeller housing outlet, which is the Y connection and filters. There was no difference between an open 1m x 150mm intake port and the Y connection on or off, there is no difference with 4 new cloth bags installed, and no difference when the two big PF are connected.

    The Y connection is larger than the 150mm intake port and I feel that ultimate flow rate is limited by an impeller and housing that were designed for 60 Hz not 50 Hz.

    Static closed port readings of 9" @ 4.6A stays the same (except for the digital manometer dancing around a bit) when the complete system is reconnected and the four blast gates are closed. With all ports open, obviously I get the same readings as 1 X 150mm straight intake - I should have done that with a bell-mouth intake but that was a few years back now, I may revisit that reading.

    Sorry to hear you are not feeling well enough to do any dust making, hope you get back to that soon. Fortunately I can do some computer work and a bit of light construction work at the moment, but it's a hard mountain I've been given to climb, I don't think I'll ever make to the top.

  9. #23
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    Finally got around to updating the old externally mounted Shop VAC system and adding a remote control for on/off. There was a mini cyclone and BIN inside the workshop that connected to the wall dust port fittings, as it's a small workshop it was taking up room. The complete system was moved into an enlarged housing on the outside of the shed wall. I went back to having one port as it's easier in the end.

    The larger housing is once again clad HardieFlex and will get painted during the week.

    Pix1: The white object protruding from the bottom of the enclosure is the chip collection bin, gets emptied about once a year.

    Pix2: This cheep replacement VAC has a blower port, basically an exhaust port and the pipe in the photo was to test the effect on noise, there is a big difference as most of the noise is from the fan. Something I could not do on the old VAC as it just spewed air out around the top cover. I'm going to replace this test setup pipe with some lined 100mm PVC as a muffler.

    .

    Pix3: The top is retained by a screw on each side, it simply slides forward and off, I made the water shield and it's glued to the wall with silicon sealer. I've used this method for years and it's simple and has never failed. The sloping top slides under the shield and no water ever enters the housing.

    P4: Top removed, VAC, switching relay, mini cyclone and remote receiver.

    .

    P5: The remote control receiver is in the gray box on the right, a small wire aerial stick out the side, no dead spots anywhere in the shed.



    I and others who use a system like this for general cleaning, have mentioned on many occasions that this is the one of the most used pieces of equipment in the workshop. You can hardly hear it inside the workshop, doesn't matter what gets sucked in, nothing ever gets into the VAC itself. The vac bin never gets emptied, the old vac was never emptied in the years it was running and it was still empty when I pulled it out the other day. All the crap, nails, screws, metal / wood shavings in the workshop are picked up with this. Small power tools / sanding tools and whatnot get connected to it to supplement the main 3HP DC. Having something ready to go at the touch of a button and not having to worry about emptying it for at least a year is magic. The work area and floor are cleaned as I work, but best of all, unlike a vac inside the room, ZERO dust gets blown around when you use it, you can clean a work area without stirring up any fine dust, not that we have much with the main DC, but it's mainly metal and wood shavings, dirt, roaches, etc and anything else I don't want in the DC pleated filters.

    Cheers.
    Mike

  10. #24
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    I bought one of those $20 mini-cyclones as well. They work so well. I chose to keep mine mobile though.

    IMG_0179.jpg

  11. #25
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    Yes I bought one when they first came out ($19) as opposed to a commercial system selling at over $200 for the same thing, and a second $20 unit when the ramp intake version came out, both work about the same. I have a quality 3M dust collection hose that covers most of the workshop, an extension covers the rest, I've almost never used the 2nd mobile unit.

    The two problems with using a mobile unit inside a workshop are the same problems as a standard VAC. Exhaust airflow blowing settled fine dust into the air, for a larger workshop like the one pictured in your photo, maybe not such a problem but in a smaller wood working shed it can be a big problem, even if you can't see it. Problem 2 is the finer particles that go right through the filter and can't be captured by the small cyclone. I have to wear a mask with a normal inside vac, when I tested with a particle counter it showed a big increase in counts and agreed with my stupidly sensitive sinus. For anyone with a sinus allergy or hay fever symptoms, an external vented or externally mounted system is a God send.

    The little hand held remotes are just icing on the cake, especially so with small power tool dust extraction.

    Mike.

  12. #26
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    Quote Originally Posted by MandJ View Post
    Yes I bought one when they first came out ($19) as opposed to a commercial system selling at over $200 for the same thing, and a second $20 unit when the ramp intake version came out, both work about the same. I have a quality 3M dust collection hose that covers most of the workshop, an extension covers the rest, I've almost never used the 2nd mobile unit.

    The two problems with using a mobile unit inside a workshop are the same problems as a standard VAC. Exhaust airflow blowing settled fine dust into the air, for a larger workshop like the one pictured in your photo, maybe not such a problem but in a smaller wood working shed it can be a big problem, even if you can't see it. Problem 2 is the finer particles that go right through the filter and can't be captured by the small cyclone.
    The problem here being, because folks can see dust they think they are safe.

    Sanding wood typically produces a small fraction of fine dust smaller than about 2.5 microns which is invisible unless it clumps together, but in an unclumped form it gets through most cyclones and shop vac filters.
    In terms of the number of particles of saw dust it is typically <0.1% of the total sawdust while in terms of the total weight it's much less ie <0.05%.

    Sounds like bugger all right?

    Let's say sanding operation generates 10g total of dust. That's about 1/12th of a cup - looks like this
    10gdust.JPG

    0.05% = 10* 0.05/100 = 5mg of sub 2.5 micron dust.

    If that is spread evenly through a 6 x 4 x 2.7m = 65 m^3 shed that's an air concentration of 77 Ķg/m^3

    This is about 2x more than the levels considered safe for sensitive groups (kid, seniors and people with allergies) but it only needs about 2x more than this to be considered unhealthy for everyone, and 2x more again to be considered hazardous for everyone.

    Remember this is just the dust that gets through the cyclone/filter, never mind the fact that nearly all vacs leak, their motor cooling loops mince fine dust into even finer stuff, and due to low flow rates simply fail to capture a lot of fine dust produced from tools and machinery in the first place.

  13. #27
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    Just to follow on the post from BobL. For the first few years we never used powered sanding tools with the VAC and the interior of the vac was always clean, the filter was always clean. That changed a few month ago when SHMBO decided to use super fine sandpaper and a small powered hand sander for finishing some items, after a few weeks of this, I noticed fine powered dust haze on the surfaces inside of the old cabinet (one wipe with a damp rag and it was gone), this is the super fine stuff that's virtually invisible until enough of it builds up somewhere (hopefully not in your lungs), the small cyclone and typical pleated filter have no hope of catching this.

    This is the main reason I went with a VAC that has a blower port. Although there is very little of that super fine dust produced, it should now be fed outside of the cabinet, and as I said before, the noise level is way down even with that bit of exhaust pipe I used. I must dig out the noise meter and have a look at the difference, especially with a lined exhaust to deaden the noise.

    EDIT: As mentioned in my post, we use this VAC system as a SUPPLEMENT to the main DC, so when sanding, the work piece in on the downdraft table, 3HP DC is running and the tool is connected to the external mounted / vented VAC system, and if that wasn't enough, the workshop is set up to have the sanding station next to the open window, and the workshop is vented by a 300mm fan through the wall. and ceiling mounted vent for anything that rises.

    Needless to say there is no fine dust build up in this workshop, I can work without a mask 90% of the time, I use a real vapour mask sometimes as the smell of some glues and timber is a bit much for my dam sinus.

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