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Any body use a Rotameter?

Discussion in 'CO2 Enrichment' started by Gbark, Feb 27, 2010.

  1. Gbark

    Gbark Guru Class Expert

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    Just wondering if anyone uses a rotameter for CO2 flow rate to reactor instead of a bubble counter. I currently use a bubble counter, but i find them crude and inconsistant to read.
     
  2. Biollante

    Biollante Lifetime Charter Member
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    Yes

    Hi,

    Bubble counters are really poor measures of CO2 flow, bad indicators of effective use and even worse devices for replication.

    Rotameters give a reasonable idea of at least relative flow, particularly at lower flow rates; still do not till us much about effective use. Where they shine in this evil plant monster, ever-humble opinion is in replication. http://www.sensorsmag.com/sensors/flow/the-basics-rotameters-1068.

    I love the fact that once you find a setting it is easy to get back to where you started, if like me you like to try things. I like the fact I can see the process and sighting is easy. They can be had fairly cheap, it really depends on how much calibration you require, contrary the opinion of the intelligentsia, I do not think there is much need. It is relative, once you are happy, that is your calibration.

    Flow meters went in my off-limits buckets a while back. I have a number I have picked up over the years cheap and I now have a fancy-schmancy test bench variety that allows me to monitor, measure and record 8 operations at once.

    Biollante
     
  3. Tom Barr

    Tom Barr Founder
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    Mass flow controllers are much better.


    Regards,
    Tom Barr
     
  4. Biollante

    Biollante Lifetime Charter Member
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    Forgot Stuff

    Hi,

    I meant to mention I use rotameters to monitor other flows and efficiencies as well.

    I also meant to include other links Cole-Palmer has actually been the most helpful folks.

    http://www.coleparmer.com/techinfo/techinfo.asp?htmlfile=V_AFLowRotometers.htm&ID=813
    http://www.instrumart.com/ProductList.aspx?CategoryID=4148&Landing=1&gclid=CP_Dy-Ggk6ACFRsiawodjj98SA
    http://www.yokogawa.com/us/ia/fieldinstruments/us-ykgw-rotameters.htm

    Agreed mass flow controllers are better.

    http://www.flowmeterdirectory.com/flowmeter_artc/flowmeter_artc_07042201.html
    http://www.aei.com/upload/File/White_Papers/SL-MFCFUND-270-01.pdf
    I cannot locate the Cole-Palmer piece.

    Biollante
     
  5. Gbark

    Gbark Guru Class Expert

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    I too agree, but they are expensive. I haven't seen any LFS suggesting anything other than a bubble counter, and yet as biollante said rotameters can be picked up cheap.

    Which mass flow controllers do you use, and have you gone as far as using a DCS system to contol everything:D
     
    #5 Gbark, Feb 27, 2010
    Last edited by a moderator: Feb 27, 2010
  6. Biollante

    Biollante Lifetime Charter Member
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    To Be Clear, Or Not...Er-ah...To... Oh Well You Get The Idea

    Hi,

    I wish to be clear, no hobbyist “needs” a rotameter and “reasonably priced” is a relative term. Relative to bubble counters, rotameters are expensive. Look around and you might find some real deals, just make sure they are designed for, or can be adapted to your task, CO2 in this case. Look for places going out of business, upgrading equipment, folks retiring. :gw


    Once people know you are looking (and you will buy) “deals” tend to come to you. The internet is good, but the phone and email are your best friends. Learn about the thing you are looking for and of course, what they cost new, out of the box. Will you need adapters? That sort of thing.

    A Left C kind of person is the sort that really ferrets out deals and understands the difference between junk and a real deal. ;)


    The lines tend to blur between the various types of flow meters and controllers. What I described as an 8 port "rotameter" is properly a mass flow controller. There are some really cool (Uh-Oh old codger speak)and "relatively" cheap digital flow meters, I hear folks refer to them as "rotameters." Maybe I am a purist or some old gasbag, but I like the traditional "rotameter" that I can see across a room things are working.



    Biollante
     
  7. Gbark

    Gbark Guru Class Expert

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    Thanks for the info, i will look around for a rotameter.

    If i can pick one up for no more than £50 i will be happy. :D
     
  8. Gbark

    Gbark Guru Class Expert

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    I was looking at a cole parmer, what sort of flow rate would i need, as you guys already use them i thought i would cheat and ask you :)
     
  9. Biollante

    Biollante Lifetime Charter Member
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    Should Have Asked

    Hi,

    Before answering your question, I should ask, I should have asked, what you are trying to accomplish?

    How are you controlling your CO2 flow?

    Honestly if the issue is control, I would rather see you spend your money on a quality needle valve. Knowing the volume of gas going in is great and it does make life easier when fiddling with levels. But rotameters are not magic and the valves on cheap rotameters are, well, cheap valves. If you have a good needle valve, that is fine a cheap rotameter will work well.

    Biollante
     
  10. pat w

    pat w Member

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    Would my vernier mod serve as a suitable alternitive, assuming you consider the Fabco 55-NV acceptable?
    http://www.barrreport.com/showthread.php/6984-Rex-Grigg-Bubble-Counter-Fabco-valve-Panel-mounted-w-simple-vernier-mod

    Pat
     
  11. Biollante

    Biollante Lifetime Charter Member
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    Hi Pat,

    A good question, I wish I had a good answer. :eek:

    My experience suggests not, since there is no feedback as to the actual volume of gas.

    I had tried using Ideal 52-1-12 Needle valve which is an excellent hobbyists control valve and a ridiculously expensive “laboratory grade” valve. Returning to a precise setting, it seems involves variables for which marking a spot on the knob does not account.

    To be fair I have been seeking a ridiculous level of precision and consistency of delivery beyond that of any reasonable needs of a weed grower.

    This is why Tom Barr said, “Mass flow controllers are much better.”

    Ultimately, Mass flow controllers are the answer. The rotameters and various other flow meters are good for a reasonable level of manual control, for that matter, I am sure that with the given alarms it would not be difficult to incorporate them in an automated system.

    I do not know how good the answer is, I hope it helps. I do think with a quality control valve, and the Fabco may well be such, that your vernier mod ought to keep you in the proverbial ballpark.

    Biollante
     
  12. pat w

    pat w Member

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    Since the low end of the acceptable range is just short of what Riccia needs to pearl and the high end is distressed fish, ballpark should just about do it, right? After that I should just have to focus on distribution and stabillity.

    Pat
     
  13. Biollante

    Biollante Lifetime Charter Member
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    You Got It!

    Hi Pat,

    Tis true! :)

    Getting the CO2 into solution and well distributed is the far bigger trick! :cool:

    Biollante
     
  14. Gbark

    Gbark Guru Class Expert

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    Hi Biollante,

    I am controlling my flow through a bubble counter using a TMC needle valve and regulator, with solenoid valve for auto shut off.

    It is not a matter of control, I would like a means of knowing my CO2 flow by reading a scale rather than counting bubbles for 30sec at a time!

    I suggested a Rotameter as these are cheaper than a flow controller, Also i'm not after a fancy DCS setup, this is far to expensive for a living room aquarium.

    Which ones do you use?;)
     
  15. Biollante

    Biollante Lifetime Charter Member
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    Lower & Bigger Is Better

    Hi,

    Well you sound like a good candidate for rotameters. I am not familiar with your set up, but it sounds as though you are doing well.

    The lower the flow rates the better.

    The key to repeatability is the size of the scale, 65mm is better than 50mm, 275mm is great. As a rule, the larger the scale the more accurate the low end reading, 65mm seems to be the default.

    Biollante
     
  16. Gbark

    Gbark Guru Class Expert

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    Let see if i have this right,

    the 65mm and 275mm that you refer to are the scale lengths?

    But what about the flow are we talking for example 0-15L/M (litres per min) or 0-15L/D (litres per day)
     
  17. shoggoth43

    shoggoth43 Lifetime Charter Member
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    If you go with the L/M you're always going to be on the extremely low end of the scale. If you want to try something consider how many bubbles/second you run and then multiply by seconds to get your minutes. Get a 2 liter bottle of soda ( empty ) and for a rough ballpark just drip water in until you have the same number of drips as the bubbles for one minute. If you aren't near a full bottle by the end of it, it's going to be a very fine reading. Conversely, multiply the amounts by 60 for liters/hour and then calculate how many hours you run CO2. If you're at or above 15 liters, then the liters per day is likely too small a value as well and you'll either need a different scale or be reading on the low end of the liters/minute scale. Generally speaking it's far easier, and repeatable, to be in the middle of any graduated scale.

    -
    S
     
  18. Biollante

    Biollante Lifetime Charter Member
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    Size Matters

    Hi All,

    My apologies, I thought I posted this yesterday; I will take the liberty of expanding on shogoth43’s post.

    Usually with rotameters the low end reading is going to be 10% of maximum, so many list only maximum flow rates as shogth43 points out this meter is no different than any other, try to size the meter so your anticipated flow ends up somewhere in the middle.

    A couple of ways of determining anticipated flow rates with an operating system in place, in addition to shoggoth43’s method.

    “How many pounds of CO2 do you go through per month” method:

    • Remembering a pound of pressurized CO2 in the tank is worth roughly 8.7 cubic foot (246.4 liter) in the wild.
    • I know the-to-a-gnats-rear-end brigade will correct this and yes, I know there are variables involved.

    Direct method:

    • Take a glass-graduated cylinder, or a glass jar.
    • Disconnect the CO2 feed from the reactor or diffuser.
    • If the diffuser or reactor is in the aquarium, fill the jar with aquarium water.
    • In the aquarium, invert the container.
    • Move the CO2 feed hose under the inverted glass and time the length of time to fill the container with gas to a predetermined level or after a predetermined amount of time mark the level on the container and determine the flow rate.
    • If the reactor or feed is outside the tank, same thing just use a bucket of water.
    (Yes, I know there are some variables and some loses, do not get your knickers in a knot.)
    For many aquarists this may well be enough to satisfy the desire to know approximately you much CO2 is going in the tank and calculate efficiency for given rates of flow.
    You also could determine the size of the bubbles in the bubble counter calculate the gas in each bubble by the rate of bubble propagation as well.

    Biollante
     
  19. Left C

    Left C Lifetime Members
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    I did a guesstimate the other night about the volume just to see 'about' what the rate might be.. As an example, one bubble per second that is 4 mm in diameter (2 mm radius) is 0.12 L/hr or 0.002 L/min.

    Calculators used
    sphere calculator: http://easycalculation.com/area/sphere.php
    cubic millimeter to liter calculator: http://www.unitconversion.org/volume/cubic-millimeters-to-liters-conversion.html
     
    #19 Left C, Mar 3, 2010
    Last edited by a moderator: Mar 3, 2010
  20. Gbark

    Gbark Guru Class Expert

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    I also did a quick calculation, but it is more than likely wrong, I worked out that my flow rate is 0.018L/M based on 3 bubbles a sec and a 5mm pipe.
    But i will do as Biollante suggests the "Direct Method" :)
     
    #20 Gbark, Mar 3, 2010
    Last edited by a moderator: Mar 3, 2010
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