ocean runner venturi

[brandon0350]

i have 2 ocean runner 2700s. what is the best way to make venturis for them?

[huig]

just put a valve in front of the air intake that way you have an adjustable venturie.

[Horace]

<a href=showthread.php?s=&postid=7808143#post7808143 target=_blank>Originally posted</a> by huig
just put a valve in front of the air intake that way you have an adjustable venturie.

Sorry bro, but the "adjustable" venturis pretty much suck compared to a properly designed one. They seem to create too much turbulance.

[brandon0350]

what is a proberly designed one? it has to be water tight. its going to be external

[Adam]

Hi all,

You can get ASM venturis (same as euroreef) from www.customaquatic.com as replacement parts. They are about $15.

Adam

[brandon0350]

the connection on a or is 3/4" male threaded. the sedra venturis are slip

[Horace]

Brandon, you dont attach the venturi to the pump... buy a male adapter that will screw into the pump and has a slip on the other side so that the venturi will slip into it. Thats how pretty much all pumps are designed. Good luck!

You can also get the venturis for the H&S skimmers from www.finsreef.com for about the same cost as the sedra. Couldnt tell you which one is better but my bet is on the H&S.

[huig]

well the problem with venturies is that you need the right size for a certain pump but when you change head the venturie needs to be adjusted to this change. (skimmer body tall or short)

eg I made a recirculating (OR3500) skimmer and the venturie I took worked well up to 70 cm and above 70 cm no air was taken in anymore. you can get around this by:
1- choosing the proper size venturie (you need to test several ones for a given height)
2- a venturie which is a bit too small and using a valve on the airintake
3- using an adjustable venturie

Horace
do you have any proof that adjustable venturies cause turbulence and if so does the turbulence affect the ability to draw in air and chop it up?

[hahnmeister]

A valve on the intake is actually a very nice way to do it. It makes them very easy to fine-tune. I have two of them set up like that and they run fine. There might be some turbulence, but that doesnt have much anything to do with it...its creating a suction...thats all. The nice thing about a valve is that you can tweak the skimmer intake to get the most air possible...a fixed venturi doesnt allow this. Tweaking is needed because depending on how you hook up an OR pump, its venturi should change as well to reflect the back-pressure placed on the pump with regards to air and water. If you are worried about 'turbulence', just mount the valve farther away from the pump intake and air inlet...but its not really an issue. Its all about pressure manipulation...thats all.

[huig]

hahnmeister
indeed, amen to that
I'll try to post some pictures of my skimmer

[landragon]

<a href=showthread.php?s=&postid=7808384#post7808384 target=_blank>Originally posted</a> by Horace
Sorry bro, but the "adjustable" venturis pretty much suck compared to a properly designed one. They seem to create too much turbulance.

I SO agree with you Horace.

Edit : and heres why. I have used both fixed and adjustable, and allthough they each have characteritics discussed here that they are named for, his comment that a properly designed one will outprform an adjustable (my words) is true. There will be a large amount of turbulence created at the air water interface of all the adj. designs I have seen, as they require the air intake tube to cross the water flow inside the water intake tube.

Also, the H&S venturi is so much better than the asm, euro, octopus, OR, etc..... On all of the pumps used in those systems too.

[hahnmeister]

The venturi needs to be designed for the right pump though. Putting an ASM venturi on a OR might not give the best output...if too large, then less air will be brought in...if too small...then too much air can cause the overall perormance of the skimmer to choke.

I have to disagree with you guys on the valve thing causing turbulence. Since when does turbulence effect the intake of the pump??? Think about it...when it gets to the pump's intake, the whole thing is TURBULENCE. The impellers and needlewheels purpose is to cause turbulence and centrifugal force to pump the water & air out. As far as what goes on before the pump's intake, its just pressure manipulation. If the water valve is closed some, the air intake will go up some (to a point of course). Its that simple. If turbulence is still a concern, you can always mount the water valve farther away from the air intake/pump intake so that the water can regain uniform flow before getting to the air intake or pump intake. There are certain right & wrong ways to do it, but the end result from an adjustable intake on an asperating skimmer is uaually much better than a ready-made one. The ability to manipulate the intake pressures of both air and water seperately to match the pressure dynamics of each unique skimmer you attach it to is very useful.

Back when Spazz was coming up with the Dart NW, I did suggest something that might have been the best of both worlds...an asperating intake with a bypass loop...much like an industrial flow eductor.

On a true venturi...I couldnt agree with you more... the sloped parts of a good venturi eductor, like a mazzei, will aid in the water flow and provide a greater drop in pressure at the air intake. This idea only slightly applies to asperating, because the intakes are on the inlet side of the pump, not outlet...and so even if there is some turbulence, it is easily overcome by the ability to tune the intake anyways.

[Horace]

Guys, here is what you can do for a venturi if you want to build your own. Take the intake tube and then find the next smaller size pipe. For example, a small cross section of 1/2" PVC will fit inside a piece of 3/4" if you make a small slit in the 1/2" chunk so that you can compress it slightly. Drill a hole through both of the pieces after you insert the 1/2" inside the 3/4" where the air hose will be inserted. You can use a dremel to enlarge the opening if you need to until you get the right amount of suction. That is the easiest way to make a correctly designed venturi w/out using a valve. I have seen other designs that are adjustable w/out a valve, but I am not convinced they are any better. I have yet to have the time to actually test it out though. Now that I have a air meter, I can do some more testing but frankly, now that I have an aquabee that came w/ a venturi I will likely just use it and call it a day. Perhaps I will try some different designs on my older DIY skimmer that has a GX2400 that doesnt have a factor venturi, but right now with the venturi I have on it that I built has it pulling 10 SCFH which isnt bad for that pump.

[hahnmeister]

Heyyy horace...thats my secret for building venturis!!! I use clear flexible hose as the reducer though. You can use a countersink bit to give its intake and outlet a slight slope, and then you can slip the air line right through it, and the rubbery hose holds it in place. Either way works fine in the end, I just find that the clear tubing is easier to work with since very few PVC pipes actually fit inside each other w/o heavy modification...I tried that too.

[BeanAnimal]

I have heated a piece of 1" thinwall pvc and stretched it several times to produce a ~1/2" neck with a steeply sloped input (about 30 degrees) and a gradual output cone (about 5 degress).

Because it is 1" pvc, it will fit inside 1" pvc fittings (a bulkhead on one end and a union on the other). This makes it's oveall length somewhat shorter than the kent or mazzie venturis but still yields the same optimized shape.

Perfect? NO... but certainly much better than a washer (orifice) based or valved setup. The lenght is a bit longer than the replacement units sold for ASMs H&S etc and should therefore offer a but less resistance to flow by keeping it more laminar (for the same size pipe reduction).

Bean

[Horace]

There was a guy on a different forum who had a different idea as well. He took a section of PVC and filled it with some sort of epoxy and then used a step drill bit (cone shaped) and drilled in from both sides so that the bit met roughly in the center of the pipe. This creates a cone shaped enterence/exit and he claimed that it incresed the suction of the venturi dramatically.

You can also make one on a lathe like this if you have solid acrylic rod (the preferred way IMO)

[BeanAnimal]

I thought of a number of ways to do this. I had considered using a "non stick" delrin or similar material to make a postive mold out of and using it to pour liquid acrylic around, lost wax casting with liquid acrylic and a dozen other things. I figured the heated PVC pipe would get me close enough to determine if it is worth the effort.

I am glueing up my unit now... but will not be able to test it until my aquatic eco order arrives... they have been VERY SLOW as of late (slow enough that I will never order from them again).

Bean...

[RandyStacyE]

This is just a crude drawing and I know that this won't work for you exactly as drawn, but I’ve measured the venturi that came with a Gen X 2400 and the ID of the middle of the venturi is almost exactly the same ID of ½” SCH 40 PVC.

Knowing this, it wouldn’t be hard at all to make an excellent venturi from PVC slip fittings.

http://randystacye.com/images/diyventuri/PVCslipventuri.gif

[BeanAnimal]

Randy the problem is turbulance. It severely reduces the efficiency of the venturi. What you have drawn is no better than a simple washer acting as an orifice (it is worse because of the length of the narrow tube acutally). There will be severe turbulance on the input side as the water backs up against the narrow orifice. The flow through the narrow section will be very non laminar and thus slower than it should be. Upon exit in the larger area the middle portion of the stream will puish ahead and backwards eddie currents will swirl around the right angle area. This will in effect slow the water through the narrow section be creating extra resistance :)

Maybe with some creative use of plumber putty and a stick you could at least make the transitions smooth.

The input side should be somewhere between a 20* and 35* angle and the exit somehwere between 5* and 10* for smooth transistion. This of course depends on the velocity and pressure of the fluid and where the engineering comes in.

[BeanAnimal]

http://www.processinnovation.com/images/venturi_stream.gif

Here is a basic illustration of the flow dynamics. The picture you have shown above would create severe flow separation in the through section as well as the output cone.

[RandyStacyE]

I know exactly what you are saying, but isn't there a different between that venturi you show and the type that is on every other needle wheel protein skimmer (inlet venturi)? I always thought the one you show is the ideal design for a 'venturi driven' protein skimmer typically installed on the 'output' of a pump.

[RandyStacyE]

That's just a crude drawing that I listed, not to scale or even the exact fittings, but I know what you mean about being 'jagged'. You could even turn it on a lathe or run a large drill bit in there to make a smoother transition if necessary. Many slip reducers are smooth and angled inside (without 90 angles). Similar to this:
http://www.jains.com/Pipefittings/pvc_fab_red_single_section.jpg

This is the GX2400 venturi I was copying:
http://randystacye.com/images/diyventuri/gx2400venturi.JPG
http://randystacye.com/images/diyventuri/gx2400venturiinside.jpg
- I wonder what that little ridge if for -

I mean yeah, a professional venturi designer/engineer might spit on the idea, but the venturi works. The ID of the fittings and the venturi are a match; that drawing of mine just sucks.

[RandyStacyE]

<a href=showthread.php?s=&postid=7818921#post7818921 target=_blank>Originally posted</a> by Horace
There was a guy on a different forum who had a different idea as well. He took a section of PVC and filled it with some sort of epoxy and then used a step drill bit (cone shaped) and drilled in from both sides so that the bit met roughly in the center of the pipe. This creates a cone shaped enterence/exit and he claimed that it incresed the suction of the venturi dramatically.

You can also make one on a lathe like this if you have solid acrylic rod (the preferred way IMO)

I've seen that. It was on Reef Frontiers by DonW:
http://www.reeffrontiers.com/forums/showthread.php?t=4007&highlight=venturi

The other dude was me. I did that after reading the above thread.

[BeanAnimal]

Randy, the same basic flow principle still apply. You are correct in the fact that most of the "OEM" stuff is shaped similar to what you posted. I was just offering some info that would help to increase the efficiency of a "DIY" design by further refining the shape.

[hahnmeister]

I dont think that the slope of the intake and other contours are necessary for an asperating venturi however. You are talking about fluid and gas under a relative suction, unlike a regular venturi which is under a relative greater pressure. If the internal contour was as important, then we would be seeing contours on asperating pump intakes that mirror the venturi's made by Kent and Mazzei...but we dont. The turbulence isnt as great because of this as well.

See, the intake of an asperating venturi behaves more like a static body... like a jug of water with a hole in the bottom... it doesnt really matter how contoured the hole is. Its the release of the water's potential energy that matters. Now, the intake on a asperating pump is much the same deal...the pump removes the water on the other end of the pipe, and the water on the other side of this intake wants to replace it with its potential energy. Only, if the intake is restricted, the water cant 'fall' fast enough, and so it draws in air as well.

A regular venturi acts more like a dynamic body on both ends, or, if nothing else, a dynamic body on the intake, and a static body at some point after the eduction point of air. In this case, the conservation of the pump's pressure seems to require a more contoured venturi.

I suppose its hard to convey what Im trying to say here, but it just seems like intake venturis and output venturis are two different beasts. We all know how much easier it is for a liquid/gas to fill a space rather than get forced through one...

IME, the intake/asperating style venturi doesnt need much contour....

[BeanAnimal]

Hahn I think you don't see the profiles becuase of the length and the cost. Why do more than what is needed to get a product out the door that works?

Turbulance is turbulance ANYPLACE in the system.

AS well, the intake profile of the pump does have an effect on the efficiency of the pump. The volute is a bernoulli device as well. Smooth flow is smooth flow...

Look at the intake ports on a cylinder head and the runners in a throttle body or intake (which are under vacuum btw). Taking a honing wheel to them and putting them on a flow bench can get you a LOT of horsepower. Not because you increase the airflow by making them bigger. By smoothing the surfaces you decrease turbulance which increases the laminar flow. Just knocking the rough edges of the castings can give you a lot. Why is this not done from the factory if it works so well? It costs extra money and time. Why do it when the engine runs and sells without the improvements.

So.. yes the contour matters. Will it work otherwise? Of course, but if your going to DIY something why not make it at leat better than what you can buy for $14 instead of worse.

[hahnmeister]

yeah, but you know what I mean when I say...

you know how water seems to fall into place and follow a straight line easier when its on the suction end rather than on the pressure end? For example, place your hand over the output of a maxi-jet intake (or similar pump where the intake is the same size as the output for arguments sake). You dont see turbulence at the intake...but you see lots of it at the output. Thats because except for the point where the water enters the pump, its at static equilibrium...no velocity, no pressure...so no turbulence, right? So no matter what the asperating venturi looks like, since the water is static until the point right where it enters the intake...how could there be turbulence? At the outlet, its under pressure, velocity, etc. Its the output of a pump that makes turbulence, not the intake. See the difference? An asperatingg venturi operates by taking from water that is at static equilibrium...its not like you see streams of water going into a pump's intake...you see them coming out. So an asperating venturi really doesnt need much to deal with turbulence since until it passes through the most restricted point in the venturi....its pretty much just static water thats experiencing a suction. A regular venturi, OTOH, has the water fed by a pump where they water is dynamic...so turbulence going into the most restricted point is more of an issue.

See what Im getting at here? I think that might have something to do with it...not sure though.

[ChemE]

Sorry Hahn but I'm going to have to side with Bean on this one. To my way of thinking, the less resistance the venturi offers the higher the flow rate in the venturi section. A higher flow rate directly translates into a greater pressure differential which directly translates into greater air being aspirated. Think of the limiting case in which I screw up the design so badly that the water is trickling through my venturi; I'd get no pressure differential and no air. Bean has to be correct.

[hahnmeister]

Uh, I gotta call you out on that one ChemE... The more resistance (or smaller the venturi's restrictive point), the higher the velocity of the water at this point, and the more the pressure drops at this point drawing water in. Sure, at a certain point, you choke the pump out of water to function...but up until this point the more restrictive, the more air gets in.

In your example, Im not quite sure what you are saying, but it seems as though you are using an extreme to prove your point...kinda like saying 'my engine chokes out if I give it too much gas, so more gas must make it perform worse'. I wouldnt draw any conclusions from your experiment gone wrong...Im sure there is another reason.

Im not saying Bean is right or wrong...Im asking for his input on this because there has to be something more to this. The turbulence from a pump's intake and lack of at the outlet are clues to this Im sure. We need a aquacultural engineer or hydrodynamics engineer. I have just never looked into it this closely.

Its kinda like this...for an asperating venturi...you dont really even need a venturi. It could be a 'T' leading to the pump inlet...no contours at all...with water coming in one end and the air coming in the other...thats no venturi because the two dont even come in together or in the same direction, etc., yet somehow it works rather well.

[BeanAnimal]

Conservation of the pumps pressure? These are not positive displacment pumps. The suction and relative output pressure are a factor of many variables.

You have brought up static bodies and dynamic bodies and equilibriums, velocities, pressures....

What I am saying is very simple. Non laminar flow is parasitic. Please review the reasons why deburring an intake manifold will increase horsepower. You may also want to do some reading on the principles of vane and centrifugal pumps and the role of the volute.

[BeanAnimal]

Hahn these are NOT postive displacement pumps. Their "suction" is a direct result of their ability to intake water and expell it. The DISPLACEMENT is variable. The more laminar the intake, the easier the pump pulls water in. The smoother the venturi, the smoother flow through it and the more volume the pump is cabable if displacing. The larger volume of displacement means more air. It is all tied together. Instead of trying to put math to this, all you need to do is understand that smooth flow is better than turbulant flow.

I have no idea why you are looking at the pumps input and output with regard to trying to corrolate turbulance through the pump body.

I fear once again, another thread is headed down a lengthy and uneeded scientific path.

[ChemE]

<a href=showthread.php?s=&postid=7822411#post7822411 target=_blank>Originally posted</a> by hahnmeister
Uh, I gotta call you out on that one ChemE... The more resistance (or smaller the venturi's restrictive point), the higher the velocity of the water at this point, and the more the pressure drops at this point drawing water in. Sure, at a certain point, you choke the pump out of water to function...but up until this point the more restrictive, the more air gets in.

The more resistance the higher the velocity? We must be thinking about two different things here Hahn. What I'm saying is given two identical venturis with identical CSA at the narrowest point but one with significant vena contracta and the other without vena contracta. Powered by identical pumps the venturi without losses from the vena contracta is going to present less head to the pump which will respond with a greater flow rate since we aren't using positive displacement pumps.

I think what you are saying is the narrower the constriction the greater the pressure gradient and the greater the aspiration which I agree with.

What say you was this a misunderstanding or are we still butting heads on the underlying science?

[hahnmeister]

Yeah, but with a asperating venturi, there is no turbulence going into the restriction point where the air is drawn in...the water is coming from a solid body of water. With a regular venturi, the water going into the venturi is in motion, so the water going into the restriction point has turbulence. I just dont see how you can have turbulence when sucking from a static body...or at least enough to warrant a contoured intake.

I dont think you are getting the analogy here Bean... look how the intake of a pump has very little turbulence around it, but the output creates turbulence all around it in a cone. Theres something to this more than we are seeing...otherwise both intake and output venturis would look the same...but they dont.

[ChemE]

<a href=showthread.php?s=&postid=7822508#post7822508 target=_blank>Originally posted</a> by hahnmeister
Yeah, but with a asperating venturi, there is no turbulence going into the restriction point where the air is drawn in...the water is coming from a solid body of water.

I don't agree with this statement. It doesn't matter whether the fluid is being pushed into the restriction (typical venturi) or if it is being sucked there (aspirating venturi) there exists the possibility of vena contracta which when present represent frictional loss. Just like if the Reynold's number is greater than 2100 the flow in that section will be turbulent.

[hahnmeister]

Ahhh, thanks for the input ChemE...the viscocity and reynolds number were exactly what I needed to hear. I went to a hydrodynamics site and found exactly what I needed. It turns out to be a bit of 2 things. Simply put, turbulence only matters if it gets into the most restricted point where the air gets sucked in. Being that the water up until the point of intake doesnt have any pressure behind it beyond static, it has no turbulence. So the water entering the venturi has only the turbulence from the suction of the venturi...which is present no matter what on any venturi...but this is still much less than the turbulence coming out of a pump and then going into a venturi...so its not as big a deal. On an asperating venturi, turbulence after the air inlet doesnt matter...its in the pump at this point in the middle of turbulence central! But on a regular venturi, the slope is there on the outlet to try and restore as much of the pressure to keep the bubbles flowing out and continue in their path. With an asperating...not an issue, so you often see no slope or only a slight one after the air inlet goint into the skimmer.

Ok, this is the other reason why asperating intakes dont need as gradual of a slope (little to none) compared to a venturi on the output. It has to do with the delta in the pressure.

On most regular or mazzei type venturis, the methos is > add pressure > pressure causes the water to gain velocity through the oriface > air is educted > mixture must keep its pressure so it continues its path. When you stand back from what our experience is with reefing and pumps...one might ask...why would you hook up an intake to the outlet of a pump...and this is a valid point. The venturi must not only overcome the natural static pressure of trying to draw air down a tube that would otherwise be under a few feet of water, but the pressure of the pump itself. If you hooked up a T to the output of a pump (a venturi w/o a restriction), the water level in the pipe would be higher than the water level in the skimmer or body of water you are pumping into. With an asperating intake...the process starts at the pump and runs in reverse. The mixture doesnt need to continue on its way after the intake because it has the pump there to mechanically push it. On the intake side, its only the relative vacuum that matters...sure...it turns out some slope it good...but not as much is needed...a 45degree cone is plenty compared to the 15degree slope you see in a mazzei.... This is because if you hook up a 'T' to the intake side of a pump like before, and ran the T like a venturi again, the relative water level in the T would be lower than the body of water you are pumping into. The pressure from the pump is working with you.

This is because a venturi on a pump outlet is trying to make a vacuum out of what is really the higher pressure end of a pump. When you look at the slope on the inside of a mazzei, it is very gradual, and that is because the restriction at its narrowest point is much greater. For example, a 3/4" pipe might need a 1/4" oriface to accelerate the water enough to overcome not only the depth pressure, but also the pressure of the output of the pump.

In the pressure equasions, on an asperating intake, the pump's pressure works with you in that the relative pressure difference between the pump and intake is more in the direction you desire (lower).

Look at a regular asperating intake... a 3/4" intake might only need to reduce its oriface to what...1/2", 3/8" to function properly?

The degree of the slope on the inside of a venturi is inversely proportional to the amount of acceleration that the water goes through...or the relative pressure drop that is desired. When its on the output of a pump, the pump's pressure works against the drop in pressure, and so the water must be accelerated that much more to overcome...hence a smaller oriface and more slope. When on the intake of a pump, the acceleration is much less because you have the pump's intake side, which aids you, and rather than the pump's output pressure working against you, it works with you because its on the vacuum side.

Its late, and I hope maybe someone can follow. The bottom line is that the degree of acceleration needed to make an asperating venturi work is less, so the slope can be much less since according to bernoulli, as pressure increases by 1.42x, flow increases by 2x...so less pressure difference (larger oriface on the venturi) means that much less pressure change...meaning that much less turbulence. So the slope you need to have on an asperating venturi can be 45 degrees or less (some asperating venturis have no slope on the pump side) and work just as well as a mazzei venturi with a 15 degree slope on the intake.

The thing that got me thinking was how the same pump with a needlewheel can make 2x as many bubbles as the same pump on a venturi. Of course there must be a difference or this commonly accepted fact wouldnt hold true. Your typical intake on a asperating is much larger than that on a mazzei type...so the slope doesnt have to be as gradual.

[BeanAnimal]

Hahn, why does every one of these threads turn into 20 paragraphs of misapplied science and big words? I am not trying ot be mean, but you seem to have a knack for dragging in an entire science book and trying to use it to explain your point. To be honest it is getting very hard to follow your line of thought and with each passing thread I am afraid your application of principles becomes more conjecture than fact. It's good that you are using your brain to try and formulate an answer and informed discussion. However, at some point the need arises to say "whoah stop" lets get back to the basics. I just don't know how to do that without offending you, or tempting you to unleash another 10 paragraph response.

[BeanAnimal]

I have looked at this both ways. It is easy to see how that the pumps "suction" alone can be used to pull air into the pump if some of the water input is restricted. This is why a simple "T" or similar injector works.

However it is prudent to understand that the pumps suction is directly related to how much material it can displace (these are not postivie displacement pumps). By smoothing the flow paths on the inlet side, the pump has to do less work and can produce an increased output. The increased output works hand in hand with the increased input (flow or velocity). You can look at this as increased suction head and can also see that the bernoulli principle can be used to show an increase in air intake.

It is very simple. You can apply the bernoulli principle at either end of the pump (and in the volute itself).

Again, you may not see these intakes on hobby skimmers beause they take up to much room and cost to much to produce. A much less refined design can provide sufficient air in many cases. The point here and the other threads was that there is much room for improvement.

[BeanAnimal]

Lastly han, please study the flow model drawings above.

If the flow in the venturi neck becomes turbulant or separated, the flow along the outside edges becomes slower due to drag and eddie current wheras the flow in the center of the of the column jets through at high velocity. This means that the air intake sees less suction. If you donwload a piece of flow simualtion software, you will see this as you shorten the venturi shape and make it's angles steeper and less refined.

Enjoy.

[prugs]

<a href=showthread.php?s=&postid=7821547#post7821547 target=_blank>Originally posted</a> by RandyStacyE
http://www.jains.com/Pipefittings/pvc_fab_red_single_section.jpg

http://randystacye.com/images/diyventuri/gx2400venturi.JPG
http://randystacye.com/images/diyventuri/gx2400venturiinside.jpg


I got the above venturis with my Genx 2400 NW pumps. They are junk & would not suck air below 8"of water. I made these & they kit butt.
http://reefcentral.com/gallery/data/583/29791skimmer_018.jpg
3/8" hose barb sanded down on an angle. A simple good working venturi. This was used on some 1"pvc plumbing.

[BeanAnimal]

Well I have installed my DIY unit on the input of the OR3700 Pump. I only have a 10-100 SCFH dwyer so my readings are rather crude at this point. I also don't have any OEM venturis to play with. However, first testing at 6" of head bounces the ball between 20 and 30 on the meter. So I figure this thing is at least pulling 15 scfh at low head. If I have time this afternoon I will try it at a much greater head. Others have indicated that the 3700 at best will pull 20 SCFH... so we will see.

[ChemE]

Bean, do you have a Kill A Watt? I'd love to see a curve of air suction and power as a function of head from 6"-60". Of course those numbers would be a strong function of the venturi but hey, it would be more data than is on the internet now!

[BeanAnimal]

No kill a watt. I am not even sure if this DIY thing is any good... it may suck. I know it cost me more to make than it would to buy the mazzie. It could be done cheaper... but my pump will rest on this so it needed to be beefy.

I also need to get a different flow meter as 10-100 is pretty broad and the ball bounces a LOT.

[ChemE]

How about the VBF-52 here (http://www.dwyer-inst.com/htdocs/flow/SeriesVFA-VFBPrice.cfm#CRA)?
(have to choose 4" on the drop down before it shows up)

Should be better suited to the range the OR3700 operates in and the longer scale (4" vs. 2") should result in less instrumental error.

[BeanAnimal]

Yeah that would be a much better choice... except I am tired of spending money on this project :(

[ChemE]

Hehe. Yup; I know that feeling quite well.

[Horace]

<a href=showthread.php?s=&postid=7825053#post7825053 target=_blank>Originally posted</a> by BeanAnimal
Yeah that would be a much better choice... except I am tired of spending money on this project :(

Oh dont I know it :)

I have spent ALOT of money on this project so far. Last night i went out and got a new circle cutting jig and bit for my router as well to the tune of $35. I have also bought two diff air meters (the first one was the wrong scale :( ) I also bought a full 10' length of 6" PVC that is now wasted because I decided I wanted a clear body and not to cheap out. So needless to say I have about $60 in wasted materials/tools. I still have to either buy or borrow somone's hole saws too :(

[orlenz]

why would we want to adjust the air input?
dont we want as much air input as possible?
IMO an adjustment valve on the air input, can only do one thing, turn DOWN the air flow, am I missing something?

[ChemE]

orlenz,

Too much air in the reaction chamber can result in an unstable foam head. If the foam is violent and boiling, it won't produce as much skimate as if it was calm and stable.

[hahnmeister]

Some mfgs like deltec even suggest in the manuals that their air intakes be at 2/3 or something like that because otherwise there can be too much air. It depends on what you have to start with, but I have had to restrict the air intake some on some skimmers as well. I like to use larger air tubing, at 3/8" most of the time...which can be a little too much.

[Roland Jacques]

<a href=showthread.php?s=&postid=7825711#post7825711 target=_blank>Originally posted</a> by orlenz
why would we want to adjust the air input?
dont we want as much air input as possible?
IMO an adjustment valve on the air input, can only do one thing, turn DOWN the air flow, am I missing something?
I was so with you on that, but I just learned something and I still can't figure it out as to why.

I was testing different ventures on a new skimmer. I was just measuring air flow. Later I tested the foam reaction. I noticed that when I remove the flow meter the foam went down. I hooked it back up and the foam column went up 2". The slight resistant increased the foam column in the neck about 75%. I am not at all sure as to why. It must have made the bubbles smaller (keeping more bubbles in solution longer is all I could think.

this skimmer was way low on air to water ratio so it was not about to much air causing aan unstable foam head.

[BeanAnimal]

OR the slight restriction may have stabilized the air intake instead of letting it oscillate.

[Roland Jacques]

<a href=showthread.php?s=&postid=7824592#post7824592 target=_blank>Originally posted</a> by BeanAnimal
Well I have installed my DIY unit on the input of the OR3700 Pump. I only have a 10-100 SCFH dwyer so my readings are rather crude at this point. I also don't have any OEM venturis to play with. However, first testing at 6" of head bounces the ball between 20 and 30 on the meter. So I figure this thing is at least pulling 15 scfh at low head. If I have time this afternoon I will try it at a much greater head. Others have indicated that the 3700 at best will pull 20 SCFH... so we will see. the screw in valve at the botom of your flow meter should stop your ball from bouncing screw it in untle your ball stablizes. On that 10-100 scale 15 Scfh may not stop bouncing.

[ChemE]

<a href=showthread.php?s=&postid=7829263#post7829263 target=_blank>Originally posted</a> by BeanAnimal
OR the slight restriction may have stabilized the air intake instead of letting it oscillate.

This gets my vote as plausible.

[BeanAnimal]

The adjustment screw adjusts the flow through the meter. Turning it down will reduce the overall flow to the skimmer :)

[Roland Jacques]

<a href=showthread.php?s=&postid=7829438#post7829438 target=_blank>Originally posted</a> by BeanAnimal
The adjustment screw adjusts the flow through the meter. Turning it down will reduce the overall flow to the skimmer :)

Yes it will, but just by the slightest amount. So you can get a reading. Otherwise it just a bouncing guess. If you had a 0-20 scfh scale you would not bounce as much but you would still have to screw it in a little to stabilize your ball.

[hahnmeister]

One of the reasons for drawing back the amount of air is because once you go past a certain point, you can end up with too much air in the pump which actually starts to choke the pump's performance. I have this happen with a couple pumps...too much air in the mix and the impeller just loses its 'bite'. Usually though, this results in a pulsing (too much air, pump throughput drops, air goes out, pump picks up again, too much air gets sucked in, it chokes, etc)....but I suppose it is possible for a NW pump to continue w/o 'pulsing' and still be drawing too much air.

OR, drawing back the air caused your pump to draw more water, raising the water level... just in case, are you sure its more bubbles/head and just not more water?

oops, sorry, nevermind...i didnt see this page yet...

[Cuby2k]

Oh for cryin out loud.

[prugs]

<a href=showthread.php?s=&postid=7972371#post7972371 target=_blank>Originally posted</a> by Cuby2k
Oh for cryin out loud.

I must be missing something here.