The energy seems to have left this thread. While I learned a lot I also remain uncertain about some of these issues and I decline to simply make up my mind without understanding as much of the facts as I can. I started a new thread off in the Chemistry forum to see if I can get a better understanding of how all this bubble & protein stuff works. If you are interested, the thread is here: http://www.reefcentral.com/forums/showthread.php?threadid=961594
Beckett vs. Needlewheel skimmers
- Thread starter alwest45
- Start date
RichConley
New member
Zephrant, it seems to me that the issue here is that the Beckett injector is entirely too restrictive for our purposes. You need a huge pump to run it because its so restrictive, and the air:water ratio is so high, and then you need to choke it back because that doesnt allow proper bubble size. It seems to me that making it slightly less restricitive, while lowering the air:water ratio may allow a much smaller pump to be used, and make these things vastly more efficient.
Just to stimulate your appetite, here's a quote from the Chemistry thread regarding recirculating skimmers vs. non-recirculating skimmers. I didn't realize it at the time but it sounds almost like a preference for beckett style skimming rather than recirc needlewheel skimming....
Nothing new. Recirculating skimmers dont add much to skimming performance IMO. I dont think they are worth the premium you pay for them. An in sump NW (non recirc) is a much better bang for the $$.
I know this thread is performance, not performance/$$, but it doesn't take a genius to see the difference in price/performance
Here are some $500 NW skimmers:
Recirculating:
H&S: A110-F2000 $460
-This is a 4" bodied 22" tall, 460 LPH skimmer rated up to 100G
Euro-Reef: RC-80 $ 500
-This is a 5" bodied 22" tall 500 LPH skimmer rated for 80+G
Non recirc:
Euro-Reef
RS180 $440
-This is an 8" body 24" tall 900 LPH skimmer rated for 180G
RS250 $485
-This is a 8" body 30" tall 960 LPH skimmer rated for 250G
I know this thread is performance, not performance/$$, but it doesn't take a genius to see the difference in price/performance
Here are some $500 NW skimmers:
Recirculating:
H&S: A110-F2000 $460
-This is a 4" bodied 22" tall, 460 LPH skimmer rated up to 100G
Euro-Reef: RC-80 $ 500
-This is a 5" bodied 22" tall 500 LPH skimmer rated for 80+G
Non recirc:
Euro-Reef
RS180 $440
-This is an 8" body 24" tall 900 LPH skimmer rated for 180G
RS250 $485
-This is a 8" body 30" tall 960 LPH skimmer rated for 250G
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hahnmeister
In Memoriam
That idealogy assumes that proteins are evenly distributed throughout the water column... but they arent. It also assumes that dwell time is the same as contact time... a relation with many theories abound.
sherm71tank
Premium Member
And being 7 feet tall never hurt either!
hahnmeister
In Memoriam
Yeah, I mean, discounting the dwell/contact time arguments, and protein concentrations, you still have several reasons for why a recirculating skimmer would work better than a single pass skimmer... beckett, needlewheel, etc.
1. single pass skimmers have worse water/air flow than a co-current skimmer... the water travels from the outlet at the bottom of the skimmer to the outlet, also at the bottom of the skimmer. A recirculating skimmer works as a countercurrent skimmer... water must travel the height of the skimmer, possibly get recirculated multiple times due to the mixing pump on the way, and eventually get to the exit pipe at the bottom.
2. Recirculating skimmers eliminate the head pressure that robs pump performance. The only head-pressure that a recircualting skimmer has to deal with is whats involved in drawing the air down the air inlet pipe... and with the pressure from the skimmer drawing water from a 12" depth of water and pumping into a 24" tall body of water (for example), your performance increases.
3. Related to #3, but even greater, is that the lower throughput means that microbubbles are easier to control... the lower throughput means a larger mixing pump can be used on the same size skimmer body... meaning more skimmate. On a single pass skimmer, a 600gph pump might be used, but on a recirculating version of that same skimmer body, a 900gph pump can be used.
If some other theories on contact time's relation to dwell time are true, or ORP, etc... the reasons begin to stack up. I would also consider the ability to slowly draw from the top layers of the tank, the layers where proteins will naturally build up if given the chance, and then feeding them directly into the skimmer isnt something you can really do with a single pass skimmer, and I would consider the ability to do this with a slow flow sump to also be a performance booster.
1. single pass skimmers have worse water/air flow than a co-current skimmer... the water travels from the outlet at the bottom of the skimmer to the outlet, also at the bottom of the skimmer. A recirculating skimmer works as a countercurrent skimmer... water must travel the height of the skimmer, possibly get recirculated multiple times due to the mixing pump on the way, and eventually get to the exit pipe at the bottom.
2. Recirculating skimmers eliminate the head pressure that robs pump performance. The only head-pressure that a recircualting skimmer has to deal with is whats involved in drawing the air down the air inlet pipe... and with the pressure from the skimmer drawing water from a 12" depth of water and pumping into a 24" tall body of water (for example), your performance increases.
3. Related to #3, but even greater, is that the lower throughput means that microbubbles are easier to control... the lower throughput means a larger mixing pump can be used on the same size skimmer body... meaning more skimmate. On a single pass skimmer, a 600gph pump might be used, but on a recirculating version of that same skimmer body, a 900gph pump can be used.
If some other theories on contact time's relation to dwell time are true, or ORP, etc... the reasons begin to stack up. I would also consider the ability to slowly draw from the top layers of the tank, the layers where proteins will naturally build up if given the chance, and then feeding them directly into the skimmer isnt something you can really do with a single pass skimmer, and I would consider the ability to do this with a slow flow sump to also be a performance booster.
Roland Jacques
Premium Member
I think it a hard topic to keep going forward in a open forum, because it so involved. When we try to narrow down and look at one part, a bunch of unrelated stuff come into the mix. kind of like we keep stepping backwards.
Even though good skimming a multi dimension interactive function, I think you do have to break it down into all the different aspects to be able to look at it and discus them. If you assign a personal value to each aspect of skimming, then debate those aspects separately on their own, then you can go forward. I think once you've done that, then you can better plug them back into the big picture. Or reevaluate your assign importance to that aspect.
Like zeph said, the performance in regards to water contact time follows a curve, ether end is bad. so the question is not which is better more turns or longer contact time. the question should be where is the BEST middle ground.
It was said that are discussion was kind of absurd cause we were talking in extremes. I might agree with that but the extremes are out here. Js big skimmer turns his tank1200 gallon tank at .5 times and hour air driven skimmer has a water dwell time of 5 minutes plus, and he thinks that's good, and another guy here like to turn 9 times an hour with his skimmer I think in fact has about a 10 seconds water dwell. This seem by itself can be extremes. My point was not to say which is right rather it was to say where is the best medium.
alwest45, You said "I didn't realize it at the time but it sounds almost like a preference for beckett style skimming rather than recirc needlewheel skimming...."
You are adding more than is there. The quote only talks about reicrc vs non recirc. when you add beckett vs NW to that, it muddys the point of recirc VS non recirc. I suggest if we want to understand these nuances that we try to eliminate the non related things to that one subject. so when you compare recirc to non recirc, keep it beckett to beckett same size... and NW to NW ... that may help us to get some things. maybe not.
Im not that good with english so i apologize if this makes no scene.
Even though good skimming a multi dimension interactive function, I think you do have to break it down into all the different aspects to be able to look at it and discus them. If you assign a personal value to each aspect of skimming, then debate those aspects separately on their own, then you can go forward. I think once you've done that, then you can better plug them back into the big picture. Or reevaluate your assign importance to that aspect.
Like zeph said, the performance in regards to water contact time follows a curve, ether end is bad. so the question is not which is better more turns or longer contact time. the question should be where is the BEST middle ground.
It was said that are discussion was kind of absurd cause we were talking in extremes. I might agree with that but the extremes are out here. Js big skimmer turns his tank1200 gallon tank at .5 times and hour air driven skimmer has a water dwell time of 5 minutes plus, and he thinks that's good, and another guy here like to turn 9 times an hour with his skimmer I think in fact has about a 10 seconds water dwell. This seem by itself can be extremes. My point was not to say which is right rather it was to say where is the best medium.
alwest45, You said "I didn't realize it at the time but it sounds almost like a preference for beckett style skimming rather than recirc needlewheel skimming...."
You are adding more than is there. The quote only talks about reicrc vs non recirc. when you add beckett vs NW to that, it muddys the point of recirc VS non recirc. I suggest if we want to understand these nuances that we try to eliminate the non related things to that one subject. so when you compare recirc to non recirc, keep it beckett to beckett same size... and NW to NW ... that may help us to get some things. maybe not.
Im not that good with english so i apologize if this makes no scene.
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hahnmeister
In Memoriam
Well... how could you? I have seem some attempts at it.... but they are hardly 'direct-feed' in the counter-current manner. I suppose one could add an inlet to the top of their single-pass skimmer, much like a recirculating skimmer's inlet, and have additional water enter the skimmer there... but that would be too much throughput for almost any skimmer... considering most have microbubble control issues as is with the mixing pump acting as the feed pump as well.
jnarowe
New member
Maybe I don't understand what you mean by "single pass". Here's a pic of my skimmer which I consider to be single pass, in that there is no recirculation pump. The water enters directly from the overflow and into the top of the skimmer. Then it flows down counter-current style and exits the bottom.
Isn't this single pass fed directly from the surface?
Isn't this single pass fed directly from the surface?
hahnmeister
In Memoriam
Ha ha ha... no, your skimmer is not a single pass. Airstone skimmers are neither, but if anything, they follow the countercurrent design because they let water in at the top, and exit at the bottom... against the upward flow of bubbles, much like a recirculating skimmer.
A single pass skimmer would be a beckett, ETSS, AquaC, where the mixing pump is responsible for the bubble production/mixing as well as the the throughput of the skimmer. The water makes a 'single-pass' since it enters the skimmer at the bottom/near the bottom, and exits at the bottom just a little ways away, and since the pump draws from outside the skimmer, there is no possibility for the skimmer water to be 'recirculated'.
A single pass skimmer would be a beckett, ETSS, AquaC, where the mixing pump is responsible for the bubble production/mixing as well as the the throughput of the skimmer. The water makes a 'single-pass' since it enters the skimmer at the bottom/near the bottom, and exits at the bottom just a little ways away, and since the pump draws from outside the skimmer, there is no possibility for the skimmer water to be 'recirculated'.
jnarowe
New member
I figured I must have misunderstood the terminology. Funny thing is that I consulted your skimmer work, sump theories, and manifold work before building my system....I only pass about 1/2 my system water per hour through that skimmer and my sump gets less than 4 x turnover.
20lb. CO2...:lol: I have not forgotten!
20lb. CO2...:lol: I have not forgotten!
Zephrant
Premium Member
Well, it comes back to conservation of energy- i.e. "you can't get something for nothing". The Beckett is restrictive because that is what a venturi is. The Beckett happens to be (in my mind) the best venturi available to us for the water and air flows we are looking at. Sure it requires a pressure rated pump, but that is the price you pay for this particular technology.
If you want less air with less water, there is a large variety of other venturi available. Most of them are threaded on each end and water-tight, and therefore much easier to use than a Beckett. However the fact that no-one as put forth a model that works better than a Beckett leads me to believe that a better one is not easily available.
But I'm certainly open to more testing.
Roland, I don't think I overstate the importance of the comments. I am sure that Randy's comments will be shocking to some, in terms of how he has turned their long held beliefs about skimming upside down. What he says is that he believes that fast water throughout the skimmer with lots of new bubbles is the more effective approach to skimming, at least if your goal is to lower the overall organics in your tank. It seems clear that he rejects the recirculation skimmer approach as inefficient. I did not appreciate the connection between his comments and fast power skimmers like beckett and DD designs until I reflected on it but I think the point can be made. However, I have asked him specifically if he thinks beckett and DD skimmers have a fundamental advantage - we'll see what he says (he may not want to get drawn into such a specific discussion).
Protein skimming is at it's heart a chemical process, not an engineering one. Attracting and binding proteins on the surface of small bubbles is at the heart of what we are trying to do. When the perhaps foremost chemistry expert on reef aquaria in the world today weighs in on this topic I think the opinions of the rest of us pale in comparison, no matter how strongly we believe in our hunches. Randy is challenging some of the fundamentals that are (rightly or wrongly) attributed to Escobal. And in this area I think his opinions carry much more weight that Escobal. Once we understand the fundamentals of protein skimming the engineers can take over and design skimmers that try to do the job more effectively than their competition. But we've all seen skimmer vendors that design product without (apparently) really understanding what a skimmer should do (my favorite example is the vendors that put a 2 foot skinny neck on their skimmer, thereby adding 2 feet to the height of the skimmer and claiming it therefore will handle a tank 200 gallons larger than a skimmer with a normal size neck). I think if Randy's perspective is accurate and it's all about lots of small bubbles exposed to as much water as possible then the design center for many of today's skimmers is wrong or at least off target.
Al
Roland Jacques
Premium Member
Good call, to post this topic over their.
I don't think his statement contrary at all to the curve idea. There is still to long of a time, and to short of a time.
"True contact time" just needs to be defined to get a good picture of what need to be considering in this topic. I just don't no how to define it.
Water in contact with bubbles. Were talking mainly about flow rates but say 2 skimmer have the same flow rate.
If one skimmers holds 2 gallons and the other holds 3 gallons and they had the same air volume and size bubbles then the 3 gallons would have more contact time. (if they were both the same shape...)
Now what if the 2 gallon has 30% smaller bubbles than the 3 gallon skimmer which would have more contact time?
Now if the 2 gallon skimmer had 300% more air than the other which has more contact time?
it obvius that the 2 gallon skimmer has a great deal more contact time. even though the flow rates are the same. It seems to me that should have a different name other than contact time.
I don't think his statement contrary at all to the curve idea. There is still to long of a time, and to short of a time.
"True contact time" just needs to be defined to get a good picture of what need to be considering in this topic. I just don't no how to define it.
Water in contact with bubbles. Were talking mainly about flow rates but say 2 skimmer have the same flow rate.
If one skimmers holds 2 gallons and the other holds 3 gallons and they had the same air volume and size bubbles then the 3 gallons would have more contact time. (if they were both the same shape...)
Now what if the 2 gallon has 30% smaller bubbles than the 3 gallon skimmer which would have more contact time?
Now if the 2 gallon skimmer had 300% more air than the other which has more contact time?
it obvius that the 2 gallon skimmer has a great deal more contact time. even though the flow rates are the same. It seems to me that should have a different name other than contact time.
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