End of tank dump

[GillesF]

Hi guys

I was talking about end of tank dumps which are typical of cheaper co2 systems on another forum. One member told me that such a dump increases the bubble rate by only 1/3 a day which won't endanger the aquarium. However, I do have noticed my shrimp panicking when an end of tank dump occured, so I'm pretty sure this CAN cause trouble.

But what factors might influence the danger of such an increase in pressure? CO2 vs O2, the bps, the circulation, ....?
Does it have anything to do with a drop in ph?

Best regards,
Gilles

 

[dutchy]

It's just that the pressure rises, and so does the bps. A ph controller will automatically compensate by shutting off sooner. A manual system is blind though, and with CO2 levels that are already high basically, it can lead to trouble. However, most people don't use a high CO2 level so they don't notice the increase.

 

[GillesF]

So basically, someone who's using the EI might encounter problems while someone who's lean dosing won't see the increase?

And what about O2 vs CO2? Can a high amount of O2 decrease the dangerous effects of an end of tank dump?

 

[dutchy]

Doesn't have much to do with EI, more with high light, since high light also means you have to use high CO2. I can also use EI with low light and 25 ppm of CO2 might be enough.

High O2 can mitigate the effect or make the threshold higher, but eventually could lead to the same problem if the CO2 level keeps rising.

 

[jerrybforl]

Gilles I can tell you from experience that if your tank dumps the last of the CO2 into the tank you're going to have problems. Your pH will drop becoming acidic and stress/kill your fish/ inverts. I've had this happen with a cheap regulator twice. That's with I invested in building my own reg! It's always best just to check the PSI left in the tank to make sure its not getting low. It sucks waking up and finding all your fishes floating...

 

[Left C]

I used to have Azoo regulators and an early AquariumPlants.com's "The Best Regulator" which had a Cornelius regulator, Burkert solenoid and Clippard needle valve. The needle valves were the weak link in these setups and the Cornelius regulator body next. The only way for me to run these regulators comfortably was to use pH controllers. These controllers cut off the CO[SUB]2[/SUB] if it happened to get to a certain limit. If needle valve fluctuation added too much CO2, the controller would cut if off. These controllers allowed me to run my CO[SUB]2[/SUB] cylinders until they were empty too. I was away from home at the college about 14 hours a day and I would come home to empty cylinders and the fish were OK. I was never home when the tank emptied to see what actually happened.

I no longer have these regulators and I don't use pH controllers any more. I've switched to Victor two stage regulators which hold a stable pressure output, dependable Burkert solenoids and Ideal "1" series needle valves that hold their flow rate setting rock solid along with simple timers. I no longer worry about needle valve fluctuations and end of tank dump. I can run the CO[SUB]2[/SUB] cylinders until they are empty. The two stage regulators hold the pressure setting up until the available pressure is less than the pressure setting. Then this last little bit of CO[SUB]2[/SUB] isn't enough to cause problems..

 

[hbosman]

I also use Victor dual stage regulators and run the cylinder down until I guesstimate that it won't last another day without a refill. If I miss, no big deal. I Just keep the lights off for the day or two I don't have CO2. Anyway, if you have a single stage regulator, just keep an eye on the tank pressure gauge. when it drops down to 500, assuming it was 800 to begin with, get the tank refilled. Once the tank pressure drops, not counting temperature, there is very little CO2 left in the cylinder so, waste is very minimal. If you are itching to get a dual stage regulator, go for it. Otherwise, refill the tank when the supply pressure gauge moves to 500 or so. You aren't talking wasting that much money at all. When I had single stage regulators, I would tweak the working pressure down to the desired setting until it was empty to squeeze out the last few pennies worth of CO2. What a waste of time. :-(

 

[Tom Barr]

I've used theVictor regs, the single stages, and a high grade valve, Ideal or Swagelok/NuPro, Burket solenoids, Clippard or Swagelok Check valves and then thick walled Tygon tubing.
This typically goes to a smaller Needle wheel diffuser which chops the CO2 into extremely fine mist and then that is fed into the pump return.

This mixes the CO2 and gives it direction into the tank.

 

[nipat]

In terms of price and reliability...

I wonder if a high-pressure rated needle valve + metering valve + high-pressure rated solenoid
is a better choice than low grade single-stage regulator setup.

Because there won't be EOTD. Bubble rate will just taper off when tank pressure drops, not rising.

 

[Tom Barr]

Mine just slowly taper........after 50-100 or more times over the years, no issues.

 

[Left C]

In terms of price and reliability...

I wonder if a high-pressure rated needle valve + metering valve + high-pressure rated solenoid
is a better choice than low grade single-stage regulator setup.

Because there won't be EOTD. Bubble rate will just taper off when tank pressure drops, not rising.

Why would you want to run a high pressure rated needle valve plus a metering valve?

Is this a typo and you meant to say high pressure regulator?

I've used a Swagelok 31 series high pressure medium flow metering valve; a SS-31RF4. It's Cv is similar to a "M" series Swagelok medium flow metering valve. It was not really very suitable for my use. There was a very tiny range of adjustment that had a usable flow for me. When I first cracked it open, the flow was low enough. After that, it was way too high. It went "plaid" as some people say. I used it with a pH controller and then I had no issues with it. Someone with a large aquarium may find it more usable than I did. Information is found in the following pdf. Page 4 has the Cv comparison: http://swagelok.com/downloads/webcatalogs/EN/MS-01-142.pdf

SS-31RF4

 

[nipat]

I mean a needle valve with CGA-320 connection. And a metering valve connected to it,
because I suppose CGA-320 valves would probably too coarse to adjust,
basically getting low grade regs out of the picture.

For example:

But one with a pressure gauge showing tank's pressure would be nice
so that you can estimate when to refill it.

The critical part would be the high pressure rated solenoid, since there is no reg
to regulate pressure anymore.

I also not sure if a metering valve like that Ideal Valve (I don't remember the model
but I think you know what I mean) will become too coarse to adjust at 800-1100 PSI
(tank's pressure).

Is this idea viable?

 

[Left C]

I mean a needle valve with CGA-320 connection. And a metering valve connected to it,
because I suppose CGA-320 valves would probably too coarse to adjust,
basically getting low grade regs out of the picture.

For example:

I understand what you are thinking about. Check out what I am saying about a Clippard part that Rex used to use on his regulator builds.

But one with a pressure gauge showing tank's pressure would be nice
so that you can estimate when to refill it.

You could install a Tee for the gauge to mount to.

The critical part would be the high pressure rated solenoid, since there is no reg
to regulate pressure anymore.

See below.

I also not sure if a metering valve like that Ideal Valve (I don't remember the model
but I think you know what I mean) will become too coarse to adjust at 800-1100 PSI
(tank's pressure).

From the Ideal literature, it says that: "Ideal needle valves offer extremely precise flow control with a working pressure up to 3000 psi for brass valves and 5000 psi for stainless steel." .... "Every valve is factory tested to be leak-tight at 1100 psi." http://idealvalve.com/

Is this idea viable?[/QUOTE]Check out what Clippard has. Rex used to sell it. The build thread is below.

There is a minature low pressure type regulator mounted after the Cornelius regulator and the solenoid that the Clippard needle valve is mounted to. I'm sure that you could add a Fabco NV-55 needle valve for a bit better control than the Clippard MNV-4K2 needle valve used in Rex's build. Both the Clippard needle valve and the Fabco NV-55 have #10-32 threads. The Clippard low pressure regulator Rex used is the 30 psi model; part no. MAR-1P-3

Rex Builds a Regulator You use the low pressure regulator for coarse adjustment and then use the needle valve for fine adjustment. I have an 100 psi model that Clippard sent me for free years ago. I've never used it.

I think that this will function somewhat what you want to create, but using different parts. Below is an image of the low pressure regulator and the description from Clippard's catalog. Note that there are relieving or non-relieving versions. I don't know if the relieving version could help with end of tank dump or not. It speaks of compensating for downstream flow obstructions and not upstream flow like needed for EOTD use. Someone might want to give it a try.

Clippard MAR-1P-3

Miniature Pressure Regulators

Regulators are offered in either relieving or non-relieving versions. The relieving design maintains a constant pressure output even when downstream conditions change. As downstream pressure increases due to reduced flow, this increased pressure overcomes the regulator piston and the pressure is relieved to atmosphere to maintain a constant output pressure. The non-relieving regulator does not automatically compensate for changes in downstream flow or pressure. There is no vent to atmosphere, as in a relieving type regulator, and the output pressure can increase due to a downstream flow.

• Panel mounting permits unit to be located with other controls on a control console or panel board for pilot operation of larger regulators or for remote control; mounting nuts and lockwashers furnished
• Small, compact - ideal for mounting on individual jigs and fixtures as well as in control circuits

Medium: Air
Materials: Brass body, Buna-N seals, stainless steel stem and spring
Air Flow: 3 scfm @ 50 psig; 5 scfm @ 100 psig; 120 l/min. @ 6 bar
Input Pressure: 300 psig/21 bar max.
Mounting: #15/32-32 thread. Nuts and lockwashers furnished
Adjustment: By means of a knob with micro-adjustment (40 pitch thd.)

 

[nipat]

But the Clippard (which is called "low pressure regulator") is still a regulator right?
I don't know if it still has EOTD or not.

What I mean is there is not any regulator at all in the setup.

The picture I linked is a needle valve, not a regulator, as least this is by the shop's description.
It is probably really a needle valve because there was a report that a guy connected it to
an inline solenoid and got the hose in between blown off. He had to switch to a pneumatic hose.

Basically, if we get a CGA-320 to 1/8 NPT adapter, is it viable to just connect a good needle valve
and a solenoid to the adapter and call it a day? This sounds better than a setup with low grade reg,
no rising working pressure when tank pressure drops.

BTW, I have an SMC relieving type reg. I bought it to connect to my Azoo reg in hope of
calming the fluctuation down some. But It operated by letting "excess" air/gas out through the vent
all the time, no matter what downstream pressure is, there was always be huge amount of air/gas
wasted through the vent. This was the way it regulated pressure. And it's mainly designed for air,
so that makes sense since air is cheap and non-toxic. I found out about this later after reading the
product info.

For our use, you will want the non-relieving type. And this leads back to the tendency of EOTD.

 

[pat w]

Over on APE there was a discussion that centered basically on the difference between bubble sizes, bubble rates and actual CO2 content per bubble. A tangent developed on the variances that might exist as a consequence of varied delivery pressures developed by the then very new Atomic diffusor series vs. older systems that operated at lower pressures. It seem to me that here you might be trading elimination of EOTD with trying to meter the feed rate at grossly elevated pressures since nothing in the chain affects pressure, only flow rates. This would mean that for a given cubic mm/sec @ 900-1100 psi you'd be flowing much more than you would @ 15-40psi.

Just my $.02

Pat

 

[nipat]

This would mean that for a given cubic mm/sec @ 900-1100 psi you'd be flowing much more than you would @ 15-40psi.

Just my $.02

Pat

Yes that is one of things to consider. That's why I asked if Ideal valve was fine enough to adjust at that range of pressure.

 

[pat w]

Your diffusion method would set the operating pressure downstream of the valve(s) so the tubing shouldn't pose an issue. I'm not sure I'd be comfortable with a needle valve with 1000 psi behind it. I don't care what they say it'll take.

Pat

 

[Left C]

But the Clippard (which is called "low pressure regulator") is still a regulator right?
I don't know if it still has EOTD or not.

Its not really a regulator, but they call it one. It basically helps cheap needle valves like Clippard's to work a little bit better. Somewhere Rex wrote about it. I thought that it was on his site. I may of overlooked it.

What I mean is there is not any regulator at all in the setup.

The picture I linked is a needle valve, not a regulator, as least this is by the shop's description.
It is probably really a needle valve because there was a report that a guy connected it to
an inline solenoid and got the hose in between blown off. He had to switch to a pneumatic hose.

I knew what you were wanting to try. I just took it a step further.

Basically, if we get a CGA-320 to 1/8 NPT adapter, is it viable to just connect a good needle valve
and a solenoid to the adapter and call it a day? This sounds better than a setup with low grade reg,
no rising working pressure when tank pressure drops.

You will still have rising pressure when the tank pressure drops. The reason is that the gas goes from its liquid state to its more higher pressure gaseous state regardless. It's the "nature of the beast."

BTW, I have an SMC relieving type reg. I bought it to connect to my Azoo reg in hope of
calming the fluctuation down some. But It operated by letting "excess" air/gas out through the vent
all the time, no matter what downstream pressure is, there was always be huge amount of air/gas
wasted through the vent. This was the way it regulated pressure. And it's mainly designed for air,
so that makes sense since air is cheap and non-toxic. I found out about this later after reading the
product info.

For our use, you will want the non-relieving type. And this leads back to the tendency of EOTD.

I'm not familiar with your SMC part, but it sounds 1ike it works just like the Clippard MAR-1P-3 "regulator" part that I mentioned.

Good luck with your project. I'm going to stick with my ebay two stage regulators.

 

[nipat]

Your diffusion method would set the operating pressure downstream of the valve(s) so the tubing shouldn't pose an issue.

Yes I agree. The blowing off issue I mentioned occurred between the (in line) solenoid and the needle valve,
when the solenoid was turn off.