The cone design discussion thread

Discussion in 'Protein Skimmers, Mechanical Filtration' started by leslie hempel, 26 Nov 2010.

  1. leslie hempel

    leslie hempel Moderator MASA Contributor

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    Guys

    what makes the "cone" a better design than any conventional skimmer design?

    my understanding is that there is less resistance for the dirt to be pushed up to the collection cup?

    please list the advantages and disadvantages of using it over the normal ones.

    im interested in seeing what thoughts we get from this discussion.
     
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  3. Bob the (reef)builder

    Bob the (reef)builder

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    I think that the idea started from the fact that the older skimmers had a "shoulder" where a lot of clumping of bubbles took place. Manufacturers then made steeper and steeper "sloping shoulders" which eventually became a pure cone.

    I have strong doubts whether a skimmer with steeply sloped shoulders is any worse off than a pure cone. In fact it will have more contact area than the cone and might be better.
     
    Last edited: 26 Nov 2010
  4. dallasg

    dallasg Moderator MASA Contributor

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    i agree, there is also a very bad misconception of how skimmers work and what the required flow rate etc is to be for them.
    i would go into the science of it, but all the people would simply disagree and tell me i am anti-skimmers again, but if u desire i can elaborate
     
  5. yusufgamiet

    yusufgamiet

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    please do.
     
  6. Achilles

    Achilles

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    I can say now one major difference! Cone skimmers are able to still skim at low salinity When conventional skimmers dont skim i have seen this first hand.
     
    magman likes this.
  7. Bob the (reef)builder

    Bob the (reef)builder

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    I would suggest that possibly it was something other than the cone, possibly the pump or some other design feature that is making the difference in the superior skimmer.

    If we were to compare two Bubble blaster skimmers one a cone and one it's steeply shouldered predesessor (both the same in every other respect) I doubt that there would be any difference.:)
     
  8. leslie hempel

    leslie hempel Thread Starter Moderator MASA Contributor

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    this is interesting guys and a good debate dallas offer your imput dude, the more opinions the better

    guys remember its just a debate and a means of learing more about the skimmer and its performances in terms of the developments that have occured..

    good comments by all.

    keep them coming.
     
  9. dallasg

    dallasg Moderator MASA Contributor

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    sources : Shane Graber
    Aquatic Systems Engineering: Devices and How They Function by P.R. Escobal

    ok here are the tools needed, i will list them and then explain

    the equation
    T = 9.2 (G/F)
    T=time
    G=total gallons of tank water
    F=flow rate (gph).
    The 9.2 is a purity coefficient that when used in this equation yields a 99.99% purity.
    Its like gravity, just believe it

    the premise
    It is estimated that some proteins take upwards of 2 minutes contact time with air to attach properly to the bubbles.

    the big four
    these are the main 4 design elements for skimmers, aka foam fractionation

    1. The water flow rate through the skimmer
    2. The height of the skimmer
    3. The amount of air pumped into the reaction chamber of the skimmer
    4. The diameter of the skimmer
    lets discuss

    1. Water Flow Rate Through the Skimmer:
    For optimum skimming, the water in your tank should not flow through the skimmer any more than two times per day. Many people believe that to skim more effectively and efficiently, you have to increase the water flow through their skimmer as the air bubbles will contact the air bubbles more times per hour. This is NOT the case. The water running through the skimmer is not the limiting factor when it comes to nutrient export. It's the amount of AIR that contacts each "drop" of water that is the limiting factor to how much a skimmer pulls out of the water column. Some organics require up to 2 full minutes of contact time with air bubbles in a skimmer before they are removed via foam fractioning. Thus the need for a slow rate flow through the skimmer is crutial for proper design and function.

    here we use the line equation y= 3/4x
    y = flow rate and x is volume in gallons
    For example, let's say you have 100 gallons of water in your reeftank and you want to find out how many gallons per hour you should flow water through your skimmer for optimum skimming. In this case it is 75 gph. Thus, for your skimmer the tank water should not flow through the skimmer any faster or any slower than 75 gph. Pretty straight forward. 75 = 3/4 * 100

    Using the above example for a moment, this should then raise another question: I'm flowing 75 gph through my skimmer. According to that, I should be running all of my tank water through the skimmer every 1.333 hours (100 gal/75 gal/hr) and not every 12 hours. Contrary to popular thought, this is not the case. Every time you run water through the skimmer, it dumps the water back into the tank of "unskimmed" water thereby diluting it. As water is continually pulled through the skimmer, it will then pull in "skimmed" and "unskimmed" water. As more "skimmed" water is pumped back into the tank, more and more already "skimmed" water will flow back through the skimmer. The equation is used to calculate when 99.99% of the water has flowed through the skimmer: T = 9.2 (G/F)

    2. Height of the Skimmer
    This one's pretty straight forward. Make the skimmer reaction chamber as tall as you can to maximize the total contact time that the water has with the air in the skimmer. He also recommends that skimmers be a minimum of 28"

    3. Amount of Air Pumped into Reaction Chamber
    According to Escobal, the upper limit of the amount of air able to be inside the skimmer at any one time is 13% of the water volume inside the skimmer.
    There are two keys to injecting air into the skimmer for optimum nutrient export:

    1. Keep the air bubbles as small as possible
    2. Minimize turbulence of the air bubbles in the skimmer reaction chamber

    4. Diameter of the Skimmer
    This selection is also pretty straight forward. The larger the amount of water to skim, the wider the diameter of the skimmer needs to be in order to skim effectively. This requirement also ties into the previous section with the amount of air pumped into the reaction chamber of the skimmer and minimizing turbulence of that air flowing upward. Based on these requirements, Escobal published a chart detailing the specific diameters required for tanks of known volume.

    [​IMG]

    so taking all of this into account and with the further research i have done and experiments on my various tanks, bigger doesnt always mean its more efficient.




     
  10. dallasg

    dallasg Moderator MASA Contributor

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    to add to this, and this is MY OPINION, most of the skimmers on the market are crap and not needed. like most things its a marketing hype like water changes
     
  11. Bob the (reef)builder

    Bob the (reef)builder

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    Escobals reasearch is pretty old and applied to pump and airstone skimmers.

    While I'm sure much of this is still applicable, I'm not sure that some of the newer variables that are used today fit with it. It would be interesting to see if anyone has published new specific research on skimming.

    I think most skimmer design is done in a trial and error way.:)
     
  12. leslie hempel

    leslie hempel Thread Starter Moderator MASA Contributor

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    its very difficult to find a standard to compare to, is there one?

    if not isnt it just the blind leading the blind?
     
  13. dallasg

    dallasg Moderator MASA Contributor

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    he research is dated and geared towards counter-current design... but the principle of foam fractionation is sound, we use similar to remove oils etc from our water plant
     
  14. Junz

    Junz

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    I would love to find out if it would work...can you hookup a BB skimmer pump to an older skimmer and let us know the result, i think the result my be suprising
     
  15. dallasg

    dallasg Moderator MASA Contributor

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    the cone shape is a marketing gimmic
     
  16. ziyaadb

    ziyaadb

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    please show me a stunning tank growing SPS with no skimmer or waterchanges done to the system
     
  17. 459b

    459b Moderator MASA Contributor

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    Last edited: 26 Nov 2010
  18. Achilles

    Achilles

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    I definitely disagree about the cone shape being a marketing gimmick, although i can base this only on 4 skimmer designs that i use constantly. 1 red sea berlin skimmer with multiple chambers, 2.old sander helgoland model venturi no cone no tapering,3 bubbleking skimmer with tapering shoulder and atb cone skimmer- i have used the same atb pump on the sander skimmer but still it doesnt produce the same foam as the bubble king with tapered shoulders. The cone skimmer is not a marketing gimmick, i would say it adds at least 20-30% efficiency to the skimmer and i would say it will most likely still skim water in hyposalinity situations even though bubble size will be bigger it , will still have foam head which the conventional ones lose at the neck in hypo
     
  19. IMarine

    IMarine

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    Hi guys i agree with Achilles a cone skimmer is no marketing gimmick,i have sold a lot of atb cone skimmers and i can say that it skims far better that your normal skimmer will do,i had over 20 top skimmers that includes bubble king 500 and now i swear by atb cone skimmers,i will be hooking up my monster over the weekend and lets see what it pulls out and its also not the amount of gunk that comes out but quality
     
  20. Trev

    Trev

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    Being an engineer working with hydrodynamics although in a totaly different field my theory on cone skimmers is that it has more to do with pressure than any other factor. Conventional skimmers use air bubbles only to create a pressure which forces organics that have attached to the bubbles to the surface. Where as a cone skimmer will use its shape to inherently create a higher pressure at the bottom of the reaction chamber which will make it nearly impossible for bubbles which have organics attached from escaping back out of the skimmer which happens alot in conventional skimmers. It would be a similar design theory as that used in the recently destroyed athlone cooling towers.
     
  21. dallasg

    dallasg Moderator MASA Contributor

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    look at mudsharks tank.....
     
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