Skimmer Ratings- a discussion.
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Jon Warner
Well-Known Member
the shape of a cone inherently has less water volume above the pump, thus less back pressure on the pump outlet.
So it means that the same pump will flow a bit more air on a cone compared to a cylinder. Again, plus vs. minus. Less back pressure/more air = good, less volume = bad.
I've always thought the whole "back presssure" issue is overplayed and I'd call it near meaningless.
Powerman
Community Member
Or just plain old head pressure..... But that is where I'm lost. Head pressure is per square inch and is only determined by height, volume does not determine head pressure at the pump discharge.
ksed
Valuable Member
Jon
Points well made
but if you look at a becket skimmer vs a RK2, the becket has little volume compared to the RK2, yet the becket would probably out skim the RK2.I dont know if I am on the right track here but you might be able to help me out here.
Thanks
Kevin:confuse:
Points well made
but if you look at a becket skimmer vs a RK2, the becket has little volume compared to the RK2, yet the becket would probably out skim the RK2.I dont know if I am on the right track here but you might be able to help me out here.
Thanks
Kevin:confuse:
luke33
2500 Club Member
I've always thought the same thing about the backpressure. Kinda a lame excuse to say the cone's are better. Its all about the transition imo.
Jon Warner
Well-Known Member
Last edited:
Jeremy R.
Community Member
There is less head pressure in a cone compared to a related standard skimmer body or even hybrid. But not always loss of water volume. Take the SRO 3000 and the XP-3000 skimmer. They both have comparable water volume as the SRO 3000 uses a standard 8" cylindar while the XP-3000(cone) has a 10" base 5" neck. Cones have less head pressure because as the cone tapers there is less water volume and for the majority of the cones on the market that I have seen only have the internal water level mid way up the cone. This is the reason that the pump will pull more air at less wattage and really makes a difference with internal skimmers because they have to draw in the feed water and the air so less head pressure can benefit the performance of the skimmer especially with smaller pumps. This is also why we are seeing a trend of manufacturers designing large, short and wide skimmers as apposed to taller cylindrical skimmers of the past. Are cones that much greater than a standard cylinder or hybrid skimmer? That really depends on who you ask, the design of the skimmer (pump and body mechanics) and the application it is used.
Powerman
Community Member
OK... I guess I'm not being clear here..... volume has absolutely...positively.... nothing to do with head pressure. Pressure is equal and spread out in a fluid. Head pressure is determined by the weight of the water column above the pump. The water level is equal on the suction and discharge (unless there is a small adjusted difference which we know changes head pressure).... therefore the only added head pressure is the weight of the column above the water level. The majority of that column is the same cone or cylinder. Volume has nothing to do with pounds per square inch.
Look at simple hydraulics. A 1 square inch piston can exert 100 psi of force on a 10 square inch surface and produce a 1000 pounds of force.
So if a cone and cylinder skimmer both have a 4" neck and are 24 inches high, how does a cone produce less head pressure at the pump discharge?
Hmmm... except foam is compressible and not the same as liquid.....then it would be a matter of the weight of the foam head on the water level, but at the water level much of the cone is submerged. So at the water level it would be the difference between a cone and a cylinder to the neck and the weight of that foam...... I'm going to call that negligible. I mean what could it be..... .01 psi?
Jeremy R.
Community Member
You just explained what I was stating about head pressure. The majority of the cones water volume is lower (with the mass majority under the water level in internal skimmers) while the equivilant cylinder would have water level above the water level putting more exertion on the pump. You also have to take in account that there is less pressure on the pumps outlet because of the larger base/ bubble chamber so there is less restriction and is also one of the factors why the cone reduces turbulence besides the slope of the body. The higher the body of water above the pumps outlet, the more pressure it has to push against.
Lets put it another way. Take two external skimmers both with the same pump, neck size and water volume. The cone with its natural slope will have less turbulance in the upper half and having the water level much lower than the cylinder in result having a much steadier head of foam formation. While the cylilnder skimmers water volume is distributed evenly throughout the cylinder and much higher than the cylinder causing more force on the outlet of the pump and hinders the pull the water and air. This is why you don't see a 4" cylinder 48" tall with a sicce pump. It is just too much pressure to be practical and why you only see force driven skimmers like becketts, venturis and downdrafts at substantial heights. But like I said there is much more involved than the shape of the skimmer body that rates a skimmer. I actually don't feel that the Cone vs its cylinder counter part really can handle larger water volumes. What the cone actually allows is more control on a wider range of water volumes.
Jon Warner
Well-Known Member
cones have very little contact time... BUT they do a great job at lifting detritus. Again... it's all about compromises. And not all cones are low-turbulence... there are several "turbulent cones" out there.
I could get into all this theory of this and that, I think we call all agree it really just has to do with balance. A balanced skimmer is the ultimate goal.
I think this is one of the best skimmer discussions I have read in a long time. Great work everyone. Lots of good experience and positive views. Great discussion.
Just my two cents.
And I havent heard about pressure in a hydraulic cylinder since I took fluid power classes in college.
I think this is one of the best skimmer discussions I have read in a long time. Great work everyone. Lots of good experience and positive views. Great discussion.
Just my two cents.
And I havent heard about pressure in a hydraulic cylinder since I took fluid power classes in college.
Troylee
all about the diy!!!!!
This is a great thread but I still want to know what powerman is after???? Are you trying to build a skimmer or buy the best bang etc????I don't want to bash any skimmers out there but I have seen straight up cylinders get down and would whoop on cones in the market today.... I run cones and I like them but I also wouldn't have any problems running a cylinder either... I should build one just to show what a good balanced one can do.... My only downfall is the tubing for the body is so darn expensive for me to build a 10" diameter cylinder it would run me a couple hundred for the body vs. The cone I can make for for 100$ off a flat sheet.... When ever I quit buying frAgs I will have some extra money lol... Might do one just for fun...
ksed
Valuable Member
I believe this is a very informative discussion on pros vs cons of skimmer designs.This is great for the hobbiest.
We should thank the big players for stepping up to the plate and helping us hobbiest with these discussions.
Keep up the good work !
We should thank the big players for stepping up to the plate and helping us hobbiest with these discussions.
Keep up the good work !
Powerman
Community Member
Well I have not really had to explain hydraulics in a while.... it is what was driving my thought process about head pressure...... it wasn't until I typed it that I realized it does not apply to compressible foam/water mixtures. Ya it is weight being applied to an area, but not the same as a non compressible fluid.
So then..... there are various variables in a balanced skimmer. Not all will be the same, yet at the end of the day, the skimmers are produced. At that point it is up to the consumer to figure out what is good and which one to get.
Yet every one's tank is different, everyone's needs are different, and everyone's approach to reef keeping is different.
So adding all that up..... there is basically no way to come up with any reasonable guidelines to skimmer sizing???? That you need so much air per gallonage, or so much tank turn over per tank size... or even so much neck per air or gallon size?
Does that sound about right?
Powerman
Community Member
This is a great thread but I still want to know what powerman is after???? Are you trying to build a skimmer or buy the best bang etc????I don't want to bash any skimmers out there but I have seen straight up cylinders get down and would whoop on cones in the market today.... I run cones and I like them but I also wouldn't have any problems running a cylinder either... I should build one just to show what a good balanced one can do.... My only downfall is the tubing for the body is so darn expensive for me to build a 10" diameter cylinder it would run me a couple hundred for the body vs. The cone I can make for for 100$ off a flat sheet.... When ever I quit buying frAgs I will have some extra money lol... Might do one just for fun...
What I'm after is the same thing that drives 90% of skimmer threads on 90% of the forums.... "will this skimmer be good for my tank"???
We know about a lot of flow rates for tank turn over and flow inside the tank. We know a lot about light out put, par readings, light spectrum and what not to be able to make an educated decision about how we want to light our reef. We know about surface area for turf scrubbers, calculations for flow and piping systems and return pumps....
Yet at the end of the day.... 90% of the consumers in this hobby are left to the mercy of asking some guy if this skimmer will be good for his tank. Or worse.... left to the mercy of a marketing claim by the company. I realize all that stuff gets worked out at some point when so many people buy the product and you can get an idea of how they are. Plus, there is certainly value to asking for ones experience, or trusting a respected vendor, and there are a lot of knowledgeable people is this hobby that have learned what to look for. I just figured though at this point there would be some sort of useful metrics to look at or develop to come up with some sort of way to judge what a component will do on your setup.
I'm really not leading anywhere... there really is no driving alternative motive here. Really just asking a question and trying to learn more.
To put it in perspective... I have learned some stuff from my own experience. I suppose there is a learning curve and experience range in every hobby. And every hobby I have been involved in, and every forum.... no matter how many times you post and answer to a common question.... it will be asked again by the next newbie coming aboard.:bigsmile:
Jon Warner
Well-Known Member
what upsets me... and I see it daily, is the guy who posts a thread saying "I have a 120G tank, so I'll buy a skimmer rated to 250 but the next model up is only $100 more so I'm buying the next model up that's rated to 400, my water will be PERFECT!"
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