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  1. #1
    Join Date
    Feb 2006
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    Perth
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    Default Chip Collector performance

    I had a spare 50L well sealed plastic drum laying around so I decide to make and test a chip collector (CC).
    The container lid has a serious rubber seal and a strong clamp so its ideal for this task.
    The PVC fittings I used are a push fit for 2" tubing and the fitting on the outer rim is also attached to a 90º elbow under the lid.
    Chip Collector performance-cc1-jpg

    I tested out how much restriction to flow the CC generated by attaching it in between a DC/VC and a 150 mm test pipe and using an air flow meter on the test pipe - both are on the bench in this photo.

    Chip Collector performance-cc2-jpg

    The maximum air flow my DC can pull through 3 m of 2" flex is ~122 cfm.
    Putting the CC in line drops the flow to 65 cfm or a 47% loss of flow

    When my clapped out National VC (which at best can pull 51 cfm though it's 1.5 m long kinked and wonky hose) is connected to the CC it pulls 47 cfm.
    These low flow rates are not just the fault of the clapped out nature of this VC and its hose but the fact that is is only a 38 mm diam hose.

    I will also test some better VCs when I get a chance and I will make up a bigger CC to test it with 4" diam ducting.

    When I finish testing I will be giving away at least this smaller CC so if anyone wants it just let me know.
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  3. #2
    Join Date
    Feb 2006
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    Perth
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    Default

    I just measured another old National Panasonic VC that is in better shape than the one I reported on in the first post.
    It gives 73 CFM without the CC and 67 CFM with the chip collector.

  4. #3
    Join Date
    May 2010
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    Not far enough away from Melbourne
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    Default

    Hi Bob,

    Just wanting to confirm that at the time of testing these vacuum cleaners had clean filters and empty bags/canisters or whatever they use to collect dust?

    What I would be interested to see would be the progressive effect on the CFM of the vacuum cleaner as it fills up without the chip collector in the line and see at what percentage of capacity the CFM drops below the CFM with the chip collector inline.

    What I am getting at is: How often will the vacuum need emptying and the filters cleaned to maintain its CFM above what it would be getting with the chip collector in place? DOes it drop down as the bag fills and if so is it at a quarter full, half full or when that the CFM drops below what it would be anyway with a separator in the line.

    Of course this would also depend on the dust that does not stop in the chip collector and starts to clog the vacuum's filters. Maybe it would require a test involving two identical dust piles each large enough to fill the vacuum. Divide each pile into say 10 smaller piles. Then hook up the vacuum only and measure the air flow. then add one of the 10 piles and measure again, then repeat until the vacuum is full. Empty and clean the vacuum and connect the separator into the line and repeat the test.

    Then we could put a cyclone in the line and find a third identical pile of dust and see whether a cyclone has a bigger or smaller effect on the drop in CFM compared to a similar sized chip collector as well as determine how much more efficient they are at collecting the finer particles that may clog the filters of the vacuum.

    Doug
    I got sick of sitting around doing nothing - so I took up meditation.

  5. #4
    Join Date
    Feb 2006
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    Perth
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    27,757

    Default

    Quote Originally Posted by doug3030 View Post
    Hi Bob,
    Just wanting to confirm that at the time of testing these vacuum cleaners had clean filters and empty bags/canisters or whatever they use to collect dust?
    Yep I gave them a complete tune up.
    - Emptied bags and blew out the filters with compressed air
    - washed and and wiped down the rubber seals with Armour-All so that they sealed nice and tight and
    - gaffer taped up a couple of cracks.
    The clapped out VC is not worth considering as it really is on it's last legs but the other VC is still in good shape and is performing normally for a 1000 W VC.

    What I would be interested to see would be the progressive effect on the CFM of the vacuum cleaner as it fills up without the chip collector in the line and see at what percentage of capacity the CFM drops below the CFM with the chip collector inline.
    Yeah I would interested as well except there is no way I am running these VCs in my shed on a long terms basis as they generate up to 24 times more dust than background without any wood dust even going into them. The first VCs gave me a full on allergy attack just running it for the 5 minutes I was doing the testing. When testing the second VC I wore a face mask and then ran the VC to vent the shed. But I don't want to cover everything in my shed with fine dust or wear a face mask when I don't need to.

    What I am getting at is: How often will the vacuum need emptying and the filters cleaned to maintain its CFM above what it would be getting with the chip collector in place? DOes it drop down as the bag fills and if so is it at a quarter full, half full or when that the CFM drops below what it would be anyway with a separator in the line.
    Yep all valid tests.

    The flow measurements are a right PITA to perform accurately as they have to be performed using the big test pipe which clutters up the shed/bench and I would not like to continually have to pull that out to repeatedly make measurements. When I retire I might do this test with a brand new VC so that I don't at least have to wear a face mask. Maybe I will install a flow meter on the VC so I can monitor what is going on all the time.

    Chip collectors and flow rates are not on my agenda during my current study but the 3 CCs I have run across so far haven't impressed me at all - in fact they appear to have made things worse since the systems they were connected to were fair pumping out fine dust. Their owners confirmed they don't need to empty their VC/bags as often which means in practice they don't clean their filters as often (or even at all!). If anything, a DC/VC system that uses a CC will need it's filters cleaned more often because the dust that gets through the CC will now contain a much greater concentration of finer dust and this appears to impair filter function faster than when a mix of coarse and fine dust is filtered. For the most recent participant (2HP DC, needle felt filter, 4" ducting with in-line 200L CC) his DC flow rate was less than 200 cfm (with no ducting connected!) which meant his filter was seriously clogged. At <200 cfm he had no chance of capturing fine dust at source which explains why his shed was covered in dust. He had no idea he had a problem. I am still working with him to try and understand what is going on.

    I have just finish making a 200L 4" ducting CC and will now go and test the flows.

  6. #5
    Join Date
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    Default 200L CC with 4" ducting

    OK - I made up a 200 L CC with 4" ducting and connected it to my DC.

    The CC is a 200 L 3 mm thick HDPE water tank.
    It also has a 90º elbow on the underneath of the outer connection and the flat lipped lid is sealed with double sided sticky foam strip.
    Chip Collector performance-cc3-jpg

    The flow through the 3 m of 4" flex without the CC is 380 CFM - remember the best one can pull with a medium sized DC through a 4" orifice is ~ 410 CFM.
    With the CC in place the flow is 277 CFM so this CC reduces flow by 27%

    It's interesting to see that a VC loses <10% of its flow when using a CC where as a DC loses nearly 50% when 2" ducting is used and 27% when 4" ducting is used.
    This is consistent with VCs being lower flow higher pressure devices compared to DCs.

    Whether DCs or VCs are use I'd be watching the filters a lot more closely and cleaning them more often than normal.
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