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Thread: sieving microscopic glass beads

  1. #11
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    Be super careful when working with this size beads. That is the size fraction most able to clog your lungs and glass doesn’t dissolve ever. Make sure the stack is enclosed and do it outside.

    nanoparticles can also get into your bloodstream.

    https://www.ors.od.nih.gov/sr/dohs/D...%20Program.pdf

  2. #12
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    Thank you for the word of caution.
    The sizes I need sieved only account for 10% or so of the batch. I'm personally looking into sieving no smaller than 3-5 microns. These are the sizes of some metal paint pigments. Not that this means they are any less dangerous but I'm taking the necessary precautions as with any fine particles.

    Viktor, I'm sorry but I still don't get the purpose of the aquarium pump. I believe the ultrasonic cleaner agitates the liquid already. Do you believe it may not be sufficient by itself?

  3. #13
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    ... the US cleaner "agitates" the fluid in a chaotic way -- so for faster separation you'll need a steady "directed" water flow through the sieves ...

    Viktor
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  4. #14
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    You've been great help. I just want to be sure I understand you completely.
    So to be clear, you know others who have used only ultrasonic cleaners withut an additional water pump and suggest the latter to speed up the process, correct?
    If so, I'm not sure what you mean by water flowing through the sieves. Water doesn't seem to flow through these tiny holes much itself.
    Last edited by neilhrgd; 08-05-2019 at 08:18.

  5. #15
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    ... water won't flow through the sieves, if only rinsing water into the sieves in open air - it's mostly the surface tension, what's holding the water in the sieve.

    But with submerged sieves it's different - here a higher filling level inside a tube (or some additive pressure) will force some water through even smallest holes -- this is the "slow water flow", I've mentioned. You can calculate the "open" surface of the holes against the sieve to get a number of possible throughput per time.

    ---
    For the "only ultrasonic" - they dissolved some carbon nanotubes in alcohol by "cracking" the clogged tubes by mechanical force (have some with 200 nanometers length and 2 nanometers diameter, which are grown in "flakes" and stay together, when removed from the substrate), then "agitated" the solution by US to distribute for single CNT's and pressed it trough a sieve with sub-micron holes to hold back clogged chunks ... then poured single droplets of the solution on sensors and let the CNT's settle across a pad grid while evaporating the alcohol ...

    Viktor
    Last edited by VDX; 08-05-2019 at 10:12.
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  6. #16
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    I did a simple experiment today before posting trying to see whether water was flowing through the sieve when it was fully submerged in water or not. I did notice a small piece of sponge moving away from the sieve but since the only container I had was only slighter larger than the sieve dish itself I wasn't sure if the force moving the piece was water going through the sieve or just water bouncing from the sieve back to the walls and reaching to the back side that way.
    Thanks for the explanation. A couple of these attached to the sieve frame should do the trick, however I will need to order some smaller sieves as these 300mm ones won't fit in an ultrasonic cleaner.
    https://www.amazon.com/Fucung-Micro-.../dp/B07FXVY4HH

    I've been thinking, instead of submerging the whole sieve dish in water there may be a less messy way to do this:

    Fill the vat of the ultrasonic cleaner with distilled water.
    Put a small sieve dish on the water and have it float on the water instead of submerging it. have a dish with no holes attached to the bottom of the sieve dish, filled with water.
    Apply your particles on the dish.
    Fill the dish 50% with distilled water and make sure it doesn't sink.
    Attach some of those tiny water pump motors I linked to the inside walls of the sieve which are submerged in water.
    Turn on the water pumps and ultrasonic cleaner.

    I think it is less messy than applying the beads on the sieve which is already under water or submerging the sieve dish with the particles already on it under water hich will form a cloud of the particles that then need to settle.


    I will update on my sieving results when I get the parts and get them working together.
    Again thanks so much for all the advice.
    Last edited by neilhrgd; 08-05-2019 at 12:02.

  7. #17
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    ... this was my idea ...

    Viktor
    Attached Thumbnails Attached Thumbnails microspheres-separation.jpg  

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  8. #18
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    I understand. This is what I'm thinking instead.

    Click image for larger version. 

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    With your approach the water pump is assumed to fill the dishes as fast as water is pumped through their sieves back. But if there is any amount of clog the dish will get filled faster than it water leaves it and it will eventually overfill.
    That's my concern. By having the pump on top of the first sieve instead I don't think this will happen. What do you think?

  9. #19
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    ... I'll add a level sensor to stop the pump, if high enough.

    The pump in the outer volume won't "see" any beads greater than the smallest holes, so the "lifetime expectation" should be better, than with bigger beads goingt through the pump and wrecking the sealings/membranes ...

    Viktor
    Aufruf zum Projekt "Müll-freie Meere" - https://reprap.org/forum/list.php?426
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  10. #20
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    Actually that makes sense. I will try that.

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