CO2 schedule ?

[Raul]

I might endup doing this since I have a couple of arduinos here, looks like a nice project.

http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1240000018

[Complexity]

Well the ph controller will be my next gadget but have to put my wallet to rest for some days :)

Yup, the wallet is the one thing that I think holds most people back. But when you consider how much money we put into our tanks, filters, CO2 equipment, lighting, decor, fish, inverts, and plants, I figure what's another hundred?

[Raul]

yep well the, DIY ph controller probably will not happen I found the probe to connect to the controller and it might be an interesting project but expensive the probe and PH board is already $96.00

http://www.sparkfun.com/products/10972

[Complexity]

Yeah, and with amount of money, you can buy a pH meter with probe.

[Totenkampf]

you can plug the solenoid operated valve (SOV) into a pH controller too. I was using a timer but will install my milwaukee controller next time around. there are mixed feelings on the pH swing, but i like the idea of using a controller now.

the SOV that comes with the milwaukee is garbage, it is not continuous duty rated. WHEN you replace look for an ASCO on ebay. We using them in chemical refineries and they last for many years.

A good NV is really important, a poor one may cause a CO2 dump when the lquid CO2 is exhausted from the cylinder and you have nothing but gas left. this can cause a rapid pressure drop -> gas dump -> dead fish. The ideal looks good, i dont know what they cost but I find it odd that I have never seen them used in my field (precison chemical analyzers) so they arent undoubtedly the best made. They get many recommendations though. Look up Swagelok metering valves on ebay, IMO a Swagelok SS-SS2 cant be beat, they may come in brass too and that would be cheaper. Note that the word "metering' means a better precision 'needle' valve

[Totenkampf]

Personally, I prefer to just use a pH controller. Then it won't matter what needle valve you use since the pH controller does all the real work. As long as you get the needle valve in the ballpark, it's good enough.

The pH controller also takes care of the turn off at night issue. It handles it automatically. Since the plants aren't using the CO2 at night, the pH won't rise at night so the pH controller won't tell the regulator to dose any CO2. The only exception would be if the CO2 outgasses from the surface, but then it would only dose a small amount to make up for what was lost. Then, when the lights come on in the morning, the CO2 is all set for the plants to use.

As the plants begin to use the CO2, the pH will rise, and then the pH controller will tell the regulator to does more CO2. It will only dose as much CO2 as needed.

So when you've just done a major trim, there's less plant material to use CO2 so the pH controller will dose less CO2. However, when the plants have really grown, there's more plant material to use CO2 so the pH controller will dose more CO2. it's all automatic. Your tank always has just the right amount of CO2 that the plants need based on their actual usage.

You can't do that with any needle valve, no matter how high the quality.

A pH controller is just an on / off switch that controls the SOV, it is NOT a flow control device. You will still need a good needle valve. The one that you bought from HD might show small precision but that doesnt mean that it has a quality design that will prevent a CO2 dump. You need a good valve for that. The Fabco is another highly regarded valve for aqaurium use, but then again they arent used in my industry so i dont have experience with them. Any metering valve of 1/8" NPT or Tube Fitting size from Swagelok / Parker / Hoke would be top notch. There are others but those are the def facto kings of the process chemical and refining market.

that said, the pH control does make things worry free by all accounts. The Milwaukee SMS122 is pretty cheap and well made. make sure you get calibration fluids for it and if you buy used, get a new pH probe

[Complexity]

I fully understand and agree that a pH controller is just an on/off switch that controls the SOV. However, because of that control, it overrides any setting from the needle valve, reducing the needle valve's importance.

Let's say I set my pH controller to 72. When the pH sits at 72, the pH controller keeps the SOV turned off so no CO2 is injected. However, when the pH rises to 73, the pH controller switches the SOV on. It is only at this point that the needle valve comes into play. It determines how much CO2 is injected -- at what rate it is injected into the tank.

So if I have the needle valve set to inject the CO2 at a very slow rate (very few bubbles per second), it will take a long time to inject enough CO2 into the tank to bring the pH back down to 72. However, if I have the needle valve set to inject the CO2 at a fast rate (several bubbles per second), it will take a short time to inject enough CO2 into the tank to bring the pH back down to 72. Either way, once the pH is back down to 72, the pH controller will turn the SOV back off. The needle valve is no longer part of the equation.

Therefore, the only role the needle valve plays is in determining how fast the CO2 is injected between the time in which the pH controller turns the SOV on and then turns it back off.

As long as the needle valve is set to a reasonably slow rate, does it really matter whether it's 1 bubble per second or 3 bubbles per second? Does that fine of a setting really matter in the overall equation? Or does it become pretty much insignificant at this point given that the pH controller is truly what's in control of determining how much CO2 is being dosed into the tank?

Without a pH controller, the needle valve is critical because of the accumulation of the dosing rate throughout a day. Three bubble per second is triple the amount of CO2 in the tank over 1 bubble per second! In this scenario, that fine difference in the needle valve's setting makes a huge difference. However, that is not the case when a pH controller is in control.

Same applies to end of tank dumps. Liquid or gas, when the pH controller literally shuts off the SOV, no CO2 is dosed. It can't. It cannot operate without electricity. So if a dump occurs, the instant the pH controller detects the drop in pH, it shuts the SOV off which stops the end of tank dump. The needle valve won't change that. However, it is my understanding that a dual stage regulator can stop the end of tank dump before it hits the needle valve, but those regulators usually cost even more than a pH controller. So that makes the pH controller a good backup against end of tank dumps for the money paid.

This is why I consider a pH controller a very good investment. You can use a lesser expensive regulator and needle valve while not only maintaining a good level of control, but even a higher level of control than a single stage regulator with an Ideal needle valve. Of course, the best would be to pay hundreds more for a dual stage regulator with an ideal needle valve and then run that on a pH controller, but at that point, you're talking some real money.

When money is a consideration, I believe the first investment should be to get a pH controller. Then, when more money can be invested, a dual stage regulator would be the next best investment. Then we can talk about an upgraded SOV, and then an upgraded needle valve. I would not upgrade the needle valve as one of the first things -- IF a pH controller could be obtained.

[Totenkampf]

thats all very well though out, however the Cv (coefficient of velocity) for a typical SOV of the type used on the CO2 setups is often 10x the flow for a Swagelok SS2 valve that is wide open. Maybe that isnt enough to matter when you are counting bubbles. Maybe it is. On another note, how fast would you say that the pH meter can respond and clamp down? Since the probe is in the water and a dump happens in a second or two, I would think it would signal you to start buying new fish. I saw a gas bubble of H2S from an anaerobic substrate start killing fish seconds after it broke the surface. Given H2S is way worse than CO2 but still, wouldnt it be easier to mechanically prevent the gas from entering the tank rather to hope that a controller signals a valve to close first? When i design things that go boom, i go for a low Cv valve or a fixed orifice, but thats me. You can often find brass metering valves for less than 50 bucks. Good insurance IMO.

[Complexity]

thats all very well though out, however the Cv (coefficient of velocity) for a typical SOV of the type used on the CO2 setups is often 10x the flow for a Swagelok SS2 valve that is wide open. Maybe that isnt enough to matter when you are counting bubbles. Maybe it is.

You just went over my head. Can you explain what that means in terms of our discussion?

On another note, how fast would you say that the pH meter can respond and clamp down? Since the probe is in the water and a dump happens in a second or two...

Okay, this is a good point. So what you're saying is that the CO2 would have already gone through the regulator, through the needle valve, and be inside the tank in a matter of 1-2 seconds? If that's the case, then how could an Ideal needle valve stop the end of tank dump any better than any other needle valve?

I always thought the main advantage of the better needle valve was that you could fine tune the bubbles (and, therefore, the amount of CO2 being dosed) more finely.

Is an Ideal needle valve able to hold back the pressure of the dump all by itself while the lesser needle valve would fail? Is that the determining factor?

[eklikewhoa]

The finer needle valve would be able to hold a true setting even if pressure is increased vs. one of lesser quality.

[Complexity]

Hmmm... I'm reading up on this, and ran across an interesting article. Forget that this is someone's faq for a system he's selling. Jump to the section that starts "What happens when the tank starts to run out?".

http://www.wcf.com/co2iron/faq.html

I like how it explains the technical process of what happens in basic language. It helps me to understand better what's going on. It also comments on the needle valve.

[Complexity]

But damn, when I price out the cream of the crop regulator that specifically states no end of tank dump, the price jumps to $450! And keep in mind that I'd need two of them!

http://greenleafaquariums.com/co2-regulators/ultimate-dual-stage-regulator.html

[Complexity]

Yes, I know I'm talking to myself. But I found this post from someone I know in a thread regarding end of tank dump, and this follows my own experience:

"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 CO2 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 CO2 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."

http://www.barrreport.com/showthread.php/9464-End-of-tank-dump?p=76677#post76677

I knew I didn't just make it up. I have always ran my tanks dry, but have never had a problem. I've always attributed that to the pH controller for the same reason as stated here.

However, I had read enough to see that there is more to the needle valve than just controlling the bubbles per second. It can help with end of tank dump problems since its job is to hold back pressure. In fact, the combination of a good needle valve and a pH controller can work well together. I can also see that it's important to maintain a stable low pressure which is something the milwaukee regulator has problems with (mine has crept from 20 to 25, for example) so I need to watch that.

So my mind is changed, and I see the value in getting a high quality needle valve as one of the first investments to upgrading an otherwise lower cost CO2 setup. Thanks for helping me to see that!

[Complexity]

Okay, here's the real answer to the end of tank dump. I thought it had to do with the regulator. To truly guard against end of tank dump issues, you have to get a dual stage regulator, and this explains why.

http://pdf.directindustry.com/pdf/matheson-tri-gas/regulators/30801-32596.html

DUAL STAGE regulators reduce the source pressure down to the desired delivery pressure in two steps. Each stage consists of a spring, diaphragm, and control valve. The first stage reduces the inlet pressure to about three times the maximum working pressure. The final pressure reduction occurs in the second stage.

The advantage of a dual stage regulator is its ability to deliver a constant pressure, even with a decrease in inlet pressure. For example, as a cylinder of gas is depleted, the cylinder pressure drops. Under these conditions, single stage regulators exhibit a “decaying inlet characteristic”; where the delivery pressure increases as a result of the decrease in inlet pressure. In a dual stage regulator, the second stage compensates for this increase, providing a constant delivery pressure regardless of inlet pressure conditions. The dual stage regulator is recommended for applications where a continuous supply of gas is required; such as the gas supplied to analytical instruments where constant delivery pressure is critical.

SINGLE STAGE regulators perform the same function as the two stage regulator using a single step reduction of source to outlet pressure. For this reason, the outlet pressure cannot be as accurately controlled as the source pressure decays. We highly recommend single stage regulators only be used in circumstances where the operator can monitor and adjust the regulator as needed or where the regulator is supplied a nearly constant source pressure.

So the concept is to hope that that the needle valve can hold the full amount of pressure suddenly dumped on it when the end of tank dump occurs. It won't stop the end of tank dump from occuring, but the hope is that it will serve as a barricade to stop the CO2 from going any further since it has already passed the regulator. However, should the needle valve fail, all hope is lost.

[Raul]

Ha!! and I thought I was done getting only the regulator hehe, but well I really like now the pressurized system and I am hooked, I was looking at the Swagelok SS2 sweet looking valve it even makes the regulator look nice, but well to expensive for now, I went for the fabco nv-55-18 even the green leaf regulaotr use that valve in their setups

http://greenleafaquariums.com/co2-regulators/nature-beast-regulator.html

the valve is $30.00 from fabco and it already has the 1/8" ports i will run it inline just for not to mess with the MA957 but later I will move it to the regulator, but it seems this valve is also good not as nice the SS or an ideal valve.