Foam Generators--Skimmer Designs

[Lavoisier]

The Beckett 1408 foam head was commonly used in DIY skimmer designs for the last several years but currently is no longer available. The concept of this type of skimmer seems sound (cf. http://reefkeeping.com/issues/2002-03/fm/index.php). What are people using now instead of the Beckett 1408?

I am assuming that newer foam genarator nozzels are even more efficient but I am not sure which one to use in my diy skimmer, such as, Sunterra 305314 Foam Jet Nozzle or Sunterra 400100 Triple Foam Jet Nozzle, 1-Inch.

Have these replaced the Beckett 1408?

 

[laugh]

So if I had one of these beckett 1408 nozzles, what would it be worth?

 

[der_wille_zur_macht]

I think you'll find that many DIY'ers and manufacturers have moved on to needlewheel designs, since they typically give you much better efficiency (a needlewheel pump drawing 30 or 40w might replace a 200 or 300w pump running a beckett).

 

[laugh]

You are really not helping the value of my beckett.

 

[Lavoisier]

I think you'll find that many DIY'ers and manufacturers have moved on to needlewheel designs, since they typically give you much better efficiency (a needlewheel pump drawing 30 or 40w might replace a 200 or 300w pump running a beckett).

Awe...yes, I just did a search and see what you mean. I have been working my way up beginning with counter current/airstones (Aquatic Systems Engineering: Devices and How They Function by Escobal) to venturi, to eductor foam nozzels, to (now) needlewheel designs. I wonder what's next!

 

[mussel and hate]

Counter current airstone revolution is next!

Seriously.

 

[laugh]

Counter current airstone revolution is next!

Seriously.

Um, no. That would be like going back to horse and buggy.

 

[peppie]

Counter current airstone revolution is next!

Seriously.

I agree, You are able to regulate the air to water ratio. It is all about contact time and bombardment rate.
IMO todays skimmers are not able to hold a candle to a properly designed and tuned counter current air driven skimmer

 

[karimwassef]

where does it show that needlewheels are able to provide better bubbles than a venturi or eductor solution? My experience has been that they are unreliable and cannot process flow comparable to an eductor.

Lavoisier, let me throw in a penductor as well:

http://www.championlighting.com/home.php?cat=1252
http://www.thepondoutlet.com/home/tpo/page_12562_617/eductor_jets.html

<a href="http://s1062.beta.photobucket.com/user/karimwassef/library/" target="_blank"><img src="http://i1062.photobucket.com/albums/t496/karimwassef/eductor_zps95e786e7.gif" border="0" alt="Photobucket"/></a>
<a href="http://s1062.beta.photobucket.com/user/karimwassef/library/" target="_blank"><img src="http://i1062.photobucket.com/albums/t496/karimwassef/eductor34m_zps61cc314e.jpg" border="0" alt="Photobucket"/></a>

The idea would be to create a housing like a Beckett with a controllable air valve inlet (and one way valve). I found this since they are commonly used as foaming fountain nozzles just as the Beckett originally was.

 

[karimwassef]

can't resist posting this when talking of foaming nozzles...

http://www.nowpublic.com/freaky-foam-beach-australia

 

[uncleof6]

For those that figure one is better than the other:

http://www.advancedaquarist.com/2009/1/aafeature2


This is the only study, that I am aware of on these "skimmers," that we so wish to argue the merits of, outside of the R & D facilities of the various manufacturers. Though "beckett" skimmers (or variations be it eductor or what have you,) are not included in this test, I am fairly confident, that had they been included, the results would be the same. I would also contend, that all the "new and improvements" do not improve on the performance of skimmers, rather are a means to separate the hobbyist from his money. An example would be the R & D by Royal Exclusiv with the bubble plates in short--very wide skimmers, utilized with great success, suddenly sparked a bunch of "me too" clones, that did not fit the use for which the bubble plate was developed.

In terms of home DIY, I have to stand with peppie, based in no small part, on information too old to link to on the internet. ( I believe at any rate)

The the air driven counter-current skimmer is the simplest to design and have work well--due to the complete separation in the introduction of water and air. Lacking the R & D facilities, and finances--as well as a gas chromatograph mass spectrometer needed to evaluate the skimmers performance, for these smaller "more efficient designs" and to make design alterations to improve the performance, it is going to guess work at best.

Further, from this same information, a downdraft or beckett (don't remember which it was) against an air driven counter current, green guck vs a mid amber colored skimmate, respectively--and a gas chromatograph mass spectrometer, the amber colored skimmate had a higher concentration of dissolved organics. That is what it is all about.

Offered FWIW.

 

[karimwassef]

Excellent article, uncle. Thanks.

While the general conclusion is that they're all comparable, the needlewheel's flowrate was consistently the lowest as was the average removal of organics (20 vs. 25 or 30 for the others). It may not be statistically significant given the spread of the data, still...

One very valuable comparison was to the airstone approach - The separation of air and water flow allowed for some very interesting and hopeful experimentation.

My own design uses a combination of downdraft (feed from the top with penductor), independent foam injection like the airstone at the bottom (separate pump and injectors), and the injection is based on a venturi...

One pump controls the flow rate in and down. The other pump controls the recirculation and foam generation. This is not the most power efficienct design due to the need for 2 pumps, but it captures characteristics of 3 out of the 4 tested designs.

<a href="http://s1062.beta.photobucket.com/user/karimwassef/library/" target="_blank"><img src="http://i1062.photobucket.com/albums/t496/karimwassef/ps_zps7af04252.jpg" border="0" alt="Photobucket"/></a>

 

[der_wille_zur_macht]

where does it show that needlewheels are able to provide better bubbles than a venturi or eductor solution?

I don't think anyone has made that claim in this thread - my comment above was meant to indicate "progress" in the sense of the direction the hobby is going, not in the sense of measurable and documented improvement. I hadn't intended to indicate that I feel that beckett skimmers are no longer valid, rather I was trying to offer an explanation for why it is not a big deal in the hobby that they are suddenly not available - because in large part the hobby has "moved on" for better or worse.

I think we need to be careful in terms of how we evaluate the results of that skimmer study. Essentially, if you measure one needlewheel skimmer against oneventuri skimmer, can you really extrapolate the results to be significant when comparing needlewheel skimmers in general to venturi skimmers in general? I think that would be a mistake. The article is very thought provoking and provides an interesting framework, for sure, but I don't think it provides a basis to broadly compare styles of skimmers.

At any rate I agree with uncle's premise to a certain extent here, there doesn't appear to be any strict correlation between specific styles of skimmer vs. performance, and the industry certainly has a LOT of marketing hype. I think two things are pretty clear: you can run a successful aquarium with any of these styles of skimmer, and there is no large body of widely accepted data that show one style is "better" at skimming than another (much less agreement on what "better" actually means).

IMHO, this leaves the hobbyist to make the decision based on their specific needs or interests. The Escobal-style airstone skimmer is hard to build for a large tank unless you've got a lot of height, for instance, so people without that kind of room will probably look elsewhere. Similarly, as I mentioned above, beckett-style skimmers typically require a much more powerful pump for a given end result, so people who are energy-conscious usually stay away from them in favor of needlewheels.

 

[Lavoisier]

Wow! What a great forum and great participators! Thanks everyone for your insightful and very helpful comments. I appreciate each of your responses. As I am considering my options for a diy skimmer I have a couple more questions that I hope you would respond to.

Following Escobar's argument (heavy going for a non-engineer like me) in his two chapters on skimmers, a skimmer that turns over the tank each 12 hours, and keeps the volume of air in the water chamber at 13% will be the most effective at keeping organics in contact with the bubbles. He provides a number of easy to use graphs to put together height, diameter, and flow. (Feel free to push back against his if you believe he is in error regarding the calculations or the physics). My questions are:

Is there a danger with venturi or eductors (or pinwheel) of putting too much air in the chamber? If so, how would one keep the percentage at 13?

What air pump (how large) would one need for a 9" diameter chamber, 60inches tall--volume of the chamber would be 3,815 cuin (I think) so one would need 496cuin of air at any given time? How loud would such a pump be?

Thanks for your thoughts.

 

[karimwassef]

I'm sure I'll get flamed for this but here goes...

A penductor is claimed to add 4x the volume of the flow of the surrounding liquid to the pressurized fluid when submerged (4+1=5... Hence a 5x multiplier). If the surrounding volume is gas (air), I would expect that the volume of injected air would be less since air is compressible while water is not... How much air? I expect it would depend on the pressure of the injected fluid... I would have to research that but that should answer the question of injected air volume.

The best forums I have found are based on firefighter hoses since these kinds of penductors are used to add foam to the pressurized nozzle outputs.

 

[karimwassef]

der wille- I didn't mean to sound mean or rude. I apologize if it came across that way. I've been out of the reef keeping for a long time and the idea of my favorite air injector losing to a pinwheel got my old biases flaring up. Sorry and thanks for the feedback

 

[der_wille_zur_macht]

karim, no worries. This has been a great thread so far.

 

[karimwassef]

while researching, I found this picture and thread in the malaysia marine club

<a href="http://s1062.beta.photobucket.com/user/karimwassef/library/" target="_blank"><img src="http://i1062.photobucket.com/albums/t496/karimwassef/730_penductor_air_zpsd9274721.jpg" border="0" alt="Photobucket"/></a>

The penductor injects water and air even when completely submerged... much like a needlewheel I expect.

http://www.chuisui.com/viewthread.php?fid=6&tid=8809&action=printable

 

[Lavoisier]

can't resist posting this when talking of foaming nozzles...

http://www.nowpublic.com/freaky-foam-beach-australia

Now that is foam refraction!!

 

[Lavoisier]

Sorry, foam fractionation.