Closed loops tricks

[Dark]

Have tips or trick to avoid having micro bubbles with a system closed loop? Many people telled me this gernre problem with the closed loop.

And also if you cant tell me somethig about your experiments with the closed loops, they are welcome…

What would you make if you should remake your closed loop?
Also, I am better to take water by my overflow drilled in my tank, or to make an independent intake in plumbing?

I've planned using an ocean Motion Super Squirt as flow divider...

Thank you in advance...

Dark

 

[Icehockey_whino]

I just got my CL going today. The only thing I would change is when measuring and cementing together all the pieces... I would make myself remember that the tank has a cross brace and it is almost physically impossible to actually get it into the tank after it has been assembled. I tweaked and angered a few of my corals doing it, but finally did it.

Micro bubbles were a problem at first but i think they were just caught up in my ballvalve apparatus. Once I tweaked it, evrything was fine.

With all the research that I did on CLs, I would recommend doing an external pumped CL. That way you don't mess with your sump or need to worry abou how fast of a return your overflow has. With external what comes out ...goes in and what goes in ... comes out...etc...

 

[Jasen Hicks]

I think the issue you are having is not a big enough intake to the pump in your closed loop. If you have too little water getting to your pump it will cavitate, strip the gas out of the water, and blow it back into your tank. (like you have now)

The way to avoid this is to 1. Put a big suction line to the pump (the goes in part) and then put a valve on the outlet (the goes out) that way you can match your input and output using the valve.

Ideally you want the input to be greater than the output so you dont have to worry... most of the time though it can be difficult unless

1. you drill the bottom portion of the tank (back side) so you have the entire column of water FORCING water down the pipe to the pump.

2. Or you can put a 2" U-Tube into it and that would draw enough through the siphon but it would be ugly!

Its all about the net positive suction head!

 

[Dark]

Do you think that a "Y" at the intake with two 1" "U" pipes intakes will help the pump to not cavitate and create micro bubles?

Dark

 

[Dark]

Any other issues taht I'd better think in the desing of my Closed-Loop?

Is that necessary to have a dismontable union on each outlet of the Super Squirt, for further dismounting?

Are you using any filter/strainer at the intake of the pump, other thant a strainer in the tank, to filter debris?

Dark

 

[Jasen Hicks]

Any place you want to keep somthing accessible, i.e. the squirt id put unions. that way if it ever clogs or gets damaged you can easily remove it and not replace a lot of PVC.. the parts add up.

I dont filter my intake to my CL pump at all. I use a GEN-X 55HP for mine and as long as you keep your inlets screened to keep large stuff out the small stuff **shouldnt** hurt your pump.

If you do 2 pipes coming to the inlet join them into a pipe that is equal to thier diameters added together... i.e. 2 1" pipes into a 2" pipe. A little time in the pvc section at HD will help put it together, just be creative with reducers, fittings, etc.

When you do join them, make sure you get at least 6" of straight pipe to your pump inlet to help reduce turbulence at the impellar. And, ALWAYS put a valve before and after the pump so you can isolate the pump and replace the impellar if needed. I didnt do it on my stock tank and had to drain all 100 gallons to fix a pump. Wasted $70 in salt that endevor. But just make sure the valve on the inlet side is always 100% open, and yes it can count in the 6" of straight pipe since it will be wide open.

Jasen

 

[Dark]

Thanks Jasen! I've never thinked about that straight section of 6" before the inlet of the pump...

Does the turbulence is responsible of micro bubles sometimes?

Dark

 

[Jasen Hicks]

It can, think of the white caps on a wave as it crashes, same idea but smaller scale. The white is the foam or gasses being released from the turbulence.

Jasen

 

[BrainBandAid]

I would recommend looking at all your connections for leaks before you seriously worry about cavitation. From what I've read, the majority of bubble problems are from pinhole leaks or un-tight threads on the suction side. Especially on closed loops.

If the problem is suction cavitation, then the bubbles are usually reabsorbed back in the discharge side, due to the higher pressure there. You would throttle shut the discharge valve for suction cavitation, or increase the suction pipe diameter.

If it is discharge cavitation, then the pump is running too fast or building too much pressure in the volute, due to too high discharge head pressure. So increasing the size of the discharge pipe would be a better fix. You would have very low flow with discharge cavitation anyway.

And if you really have cavitation, you should be able to hear it very well. Sounds like little pebbles being bounced around in the volute. Or like knuckles cracking.

And if it's turbulence, wouldn't the water have to mix with air at some point? It shouldn't if it's really a closed loop.

Also, I read a long post a while back about a guy who's chemistry was way out of whack and it caused his water to be saturated with some kind of gas, like oxygen or something. Poor guy went crazy trying to get rid of the bubbles. Ended up being that some meter or test kit he had messed up his alkalinity or something...
I'll have to try and find that one.

Hello Jasen...
(Ex) MT2 from the Maryland Gold :wavehand:

 

[NoCarrier]

Re: Closed loops tricks

<a href=showthread.php?s=&postid=8490634#post8490634 target=_blank>Originally posted</a> by Dark

Also, I am better to take water by my overflow drilled in my tank, or to make an independent intake in plumbing?

Couldn't this be a problem? An overflow intake seems like a likely source for extra air entering the plumbing.

 

[Jasen Hicks]

He does need to use an independent intake.

As for the bubbles.... Your aquarium has a lot of gasses in it including oxygen, nitrogen, etc. If it didnt then the fish would die. The whole system is open to the atmosphere so there is a constant gas exchange. I'm not sure the exact amount of air, but its a lot more than most people give credit for!

Jasen

 

[samtheman]

"strip the gas out of the water"
"building too much pressure in the volute, due to too high discharge head pressure."

Neither of these describe cavitation. Cavitation is where the pump does not have enough flow into the intake. The pump puts the water into a low pressure area where some of it vaporizes, causing bubbles.

 

[Dark]

Re: Re: Closed loops tricks

Re: Re: Closed loops tricks

<a href=showthread.php?s=&postid=8501703#post8501703 target=_blank>Originally posted</a> by NoCarrier
Couldn't this be a problem? An overflow intake seems like a likely source for extra air entering the plumbing.

Sorry, my english is'nt very good...

I was talking about my "hole" for my actual overflow ( I have two in my 125G for overflows). Just wanted tu use one of them for plumbing intake of the losed loop, but I can easily make an intake for the CL without using it.

Dark

 

[newnano]

cavitation doesnt create microbubbles necessarily. you can get cavi without bubbles. so most likely you have air getting in somewhere. also, anytime you set up a new system it could be a cpl weeks before micros disappear and you get "slime" all over everything.

if your pump is cavitating then look at your plumbing. are you restricting the pump in some way? i did this once with a 90 degree elbow too close to the intake of the pump

 

[Dark]

We can easily stop cavitation with a ball valve on the output of the pump... To reduce flow?

What are your intake look like? A PVC pipe caped with many small drilled holes? Or normal cone stainers?

Dark

 

[ReefJerk]

<a href=showthread.php?s=&postid=8493401#post8493401 target=_blank>Originally posted</a> by Jasen Hicks
...If you do 2 pipes coming to the inlet join them into a pipe that is equal to thier diameters added together... i.e. 2 1" pipes into a 2" pipe... When you do join them, make sure you get at least 6" of straight pipe to your pump inlet to help reduce turbulence at the impellar.
Jasen

Would the two 1" pipes then be sufficient to feed a 2" inlet? I have a dilemma where I need to feed a 3" inlet with (2) 1 1/2" U pipes over the back of the tank. The manufacturer highly recommends against reducing the inlet. With these 2 feeds on the 1 1/2" inlet of a Gen-X 18000(4750gph), I could hardly feel any drastic suction from either side with my hand. I just want to make sure I don't cavitate, or kill, the pump as soon as I power it on.

Cliff

 

[Jasen Hicks]

If the inlet of the pump is 2" and you put about a 6" run or more of 2" pipe in front of the impellar you could get a 1" - 2" elbow and a 2"x1"x" T to tie it all together it should be fine.

somthing like this simple drawing:

| |
L ===T === PUMP
(keep the L and T as close together as possible)
(T to PUMP should be AT A MINIMUM 6")

| is 1" pipe
=== is 2" pipe

 

[Jasen Hicks]

Sorry, that TXT drawing sucks.. heres one i did PS:

 

[samtheman]

<a href=showthread.php?s=&postid=8502436#post8502436 target=_blank>Originally posted</a> by newnano
cavitation doesnt create microbubbles necessarily. you can get cavi without bubbles. so most likely you have air getting in somewhere. also, anytime you set up a new system it could be a cpl weeks before micros disappear and you get "slime" all over everything.

if your pump is cavitating then look at your plumbing. are you restricting the pump in some way? i did this once with a 90 degree elbow too close to the intake of the pump

"Cavitation implies cavities or holes in the fluid we are pumping. These holes can also be described as bubbles, so cavitation is really about the formation of bubbles and their collapse. Bubbles form when ever liquid boils. Be careful not to associate boiling with hot to the touch. Liquid oxygen will boil and no one would ever call that hot."

Cavitation is the formation of bubbles as water vaporises. You can't have cavitation without bubbles. That is the defination.

 

[Jasen Hicks]

Ok, i agree it may or may not be cavitation. Let me explain a little bit better.

Pumps require NET POSITIVE SUCTION HEAD (abbreviated NPSH) at the inlet to function properly and not get damaged, cavitate or cause too much turbulence at the impellar. All NPSH is... amount of water weight at the inlet of the pumpthe VOLUME of water at the inlet of the pump (pressure into the inlet, because volume is proportionate to pressure)... . Put a pump at the bottom of a 55 gallon drum full it has a LOT of NPSH, put it very near the surface of the 55 gallon drum it has very little.

Equate that to the pipes feeding your pump... a 3/4" inlet line is a lot less than a 1" inlet line, or a 2" inlet line.

When you do not supply the proper amout of NPSH to the pump it will bring gasses out at the impellar. Why? A pump that is used in an aquarium is a centrifugal pump, it spins creating a low pressure part at the impellar and creating a high pressure part at the outlet or volute of the pump. Simple science, gasses stay in solution at high pressure and come out at low pressure. The impellar which drops pressure will bring this gas out of solution and send it to the tank as microbubbles if there is not enough NPSH.