Low cost, accurate means of measuring dissolved CO2

[Eric Brewer]

I understand the physics behind dissolved CO2. And thanks to Dave Meheen, I now have a nifty chart for ideal settings to make our bottler happy.

But my boss and I have other reasons to want to measure CO2 in solution. We've priced out a few instruments for this task. Just wanted to know if there was an industry standard for the <20K BBL brewery.

The International Carbonic meter we are currently using is nowhere near accurate enough for our needs.

[Larry Doyle]

Make me smart. You are not talking vols. of Co2 are you? What are you measuring and why?

[Eric Brewer]

Yes, I'm talking volumes of CO2.

Same as dissolved CO2 -- how much CO2 is in solution. Boyle's law, Dalton's law and all that. Same stuff I learned in SCUBA school. (But there we were more concerned about nitrogen than CO2.)


The reasons are:

1) To keep our bottling machine happy.

2) To achieve better product consistency. X beer has 3.2 volumes @ Y Temp prior to bottling. Z beer has 3.5 volumes and so on.


One of our biggest consumer complaints is that the beer carbonation levels are either way too low or way too high. I haven't been the brewer here long enough to see examples. So I'm falling back to the way I solve every problem -- measure it, record it, see if I can repeat it.

First, I need accurate measurements.

[dick murton]

Many moons ago, we used to add an accurate vome of specific strength caustic to a bottle or can of beer, or run beer into a standard volume of the same caustic into a standard size bottle, and then titrate the resulting carbonate with acid. I'm afraid i don't have the details of this ananlysis any more.

The more sophisticated and expensive version of this is to use a Corning instrument. I understand that although these were no longer being made the manufacturers / agents have started to recondition them, and perhaps even make new ones as they are so popular.

If I can find details of the reagents / volumes / analysis, I will post them (thinking about it, I could do with this info in case I ever need it for my own purposes), but you should be able to go back to chemistry basics to get an idea of what is required. Don't forget to add a slight excess of caustic though to ensure it is carbonate not bicarbonate, so you get a consistent analytical result

Cheers


Dick

[BrewinLou]

A used Zahm Nagel IS the inexpensive way to test. It is as manual as it gets. If you are bottling tell your boss that is what you need. If he/she thinks thats is expensive show them a quote for a Gehaltemeter.

[Larry Doyle]

GOOD NEWS! You do not have to be a rocket scientist or a physicist to know what the CO2 vols are in your beer. All you need to know is pressure and temperature of the product.

For packaged product, use a Zahm piercing device. Its a simple device that pierces the bottle/can and has a pressure gage attached and sometimes a dial thermometer attached. I say "sometimes" because they used to come with or without the thermometer.

What you do is heat your bottle/can up to ~68 degrees f, pierce it, shake hard for a few seconds. Then you read the pressure on the gage. If your device has a built in dial thermometer, read the temp. If the device does not have a thermometer, just stick a good thermometer into the bottle can and read the temperature. Once you have pressure and temp, consult a chart and read your CO2 vols. You can get the chart from Zahm and Nagel or your peers in cybeerspace. (hey, I just made that up).

Backing up in the process, you need to know what the Co2 level is in you bulk beer.( Its too late after it hits the filler). To measure CO2 in bulk beer use another device sold by Zahm and Nagel. Don't know what they call it but its a metal bottle with a thermometer and pressure gage attached. You attach the bottle to the tank via a swiggle, let it run to the floor for a couple minutes and then shake it real hard.Then you read the pressure and temperature, consult a chart and read your CO2 vols. Note that this is a different chart than the one used for packaged product since the temperatures are significantly different.

By using these two devices you are measuring CO2 with oranges and oranges instead of apples and oranges. In my experience, tank CO2 is a bit higher than packaged CO2 so you will come up with tank CO2 specs that will yield packaged beer CO2 vols in your acceptable range, if you even have one. Below are made up numbers to show you what I am talking about:

TANK CO2 SPEC = 2.65-2.75
PACKAGED SPEC= 2.50-2.70

Our tank spec was always tighter than our packaged spec.
By using these devices there will be reasonably good predictabilty between bulk and packaged CO2.

Why not use a sooper dooper electronic device such as a gehaltameter? I think its more complicated and more high tech than you need. I also think the Zahm devices are more reliable: its just P and T.

Also, you don't need an instrument technician to test and maintain the Zahm devices. You test your gages by comparing them to a standard gage on a test rig. If the thermometers go bad, its usually because the mercury has separated and you can see that.

And finally, using the Zahm device for packaged CO2 we found that the CO2 vols differed depending on what size your package was. The "apparent" CO2 increased as the package size increased. But this was not a problem.. Our package CO2 specs for 7 oz were .05 vols lower than the 12 oz specs and our specs for 32 oz were .05 higher than the 12 oz. specs. Again, this was not a problem.

That's all for now. I think Zahm and Nagel should send me a Zahm and Nagel tee shirt.

[coolguywalt]

I second the Zahm. We use it for our beers to ensure not only do they bottle at the right carbonation, but serving them from the tap is consistent every time.

[Rob Creighton]

North American Dispense Systems sells a discount version of the Zahm that works fine. It sells through Foxx for about $300.00. I've replaced the gauge once (but you have to do that with Zahm as well) but other than changing the tubing occassionally, it has been reliable and has tested against a Zahm well. 2.5 to 2.7 is your target.

[Larry Doyle]

Thanks Rob. I am assuming you are talking about the piercing device for cans/bottles. Am I correct?

Also, do you check CO2 in bulk beer? What do you use for that?

[Eric Brewer]

GOOD NEWS! You do not have to be a rocket scientist or a physicist to know what the CO2 vols are in your beer. All you need to know is pressure and temperature of the product.

While I'm going to look into the Zahm, the above isn't entirely true.

I can raise the pressure in my bright from 0 PSI to 14 PSI in about 15 minutes. Just because the gauge reads 14, and my temp is 34, doesn't mean I'm at 3.0 volumes.

There's a third variable -- time. It's what prompted Joseph Priestly to get this whole carbonation train rolling.

We're in the situation right now where we need to bottle product X the minute it's ready, so we can send product Y over, so we can bottle that the minute it's ready, so we can send product Z over.

Yes, we need additional bright tanks. (We only have two.) But space and money are concerns.

So, while we're certainly interested in measuring the volume of CO2 in our packaged product, we're more interested in bulk beer volumes. We don't want to have to use the bottling machine to take a measurement.

We basically need a solution for the volume in the BBT, and in the packaged product -- so we can compare them and log them.

[Larry Doyle]

I never said you figure tank CO2 by looking at a pressure gage and a thermometer in a tank. We always figured it by using the metal Zahm bottle that has a gage and a thermometer. The zahm bottle doesn't care what your tank instrumentation is reading and it doesn't care how long the beer was in the tank. It only cares about the beer that was put into it.

[froptus]

Buy a Zahm. I've been using one for 15 years and they're quite accurate. Yes you do have to replace the guage once in a while. Of course the tank you pulling the sample from does need to have a Perlick style sample valve ($100.00 at GW Kent). The Zahm itself costs around $1000.00 brand new. Not exactly cheap but it will give you many years of reliable service.

Just a week ago I did see that new device that Foxx is offering. I don't know how well it works though. A Zahm is the industry standard.

[beermaker]

I use a Zahm on the tank...purchased new in 1994, may be the only piece of gear Ive never had to work on...last year I also purchased this unit (T-03-495) from www.terriss.com to take bottle readings, so far it works fine and was way cheaper than anything else I found.

michael@chocbeer.com

[TL Services]

Zahm, Gehaltemeter and others that use pressure and temperature are fine instruments...so long as there is only CO2 present.

Any other gas - eg. N2 is very commonly used in the UK and elsewhere for improvements in head stability, foam tightness, etc. - and these methods will not give the correct result.

If anyone does use N2 then an Orbisphere 3654/3658 or Anton Paar CarboQC are the way to go.

High levels of dissolved oxygen (hopefully not something that troubles folk on here ) will also interfere with accuracy.

Like dick murton, I can remember titrating and also a pressure method in the dim/distant past that required a measured amount of beer to be put into a round-bottom flask attached to an angled burette, then shaken to release the CO2. A mercury bead - I think - moved up the burette until the pressures equalised, giving a CO2 reading from the point it reached on the scale...

Corning instruments - the 965 model - are still available as refurbished units.

[Rob Creighton]

..last year I also purchased this unit (T-03-495) from www.terriss.com to take bottle readings, so far it works fine and was way cheaper than anything else I found.

Eureka! To all of the guys at the Michigan Winter Technical Conference that asked me about bottle lifters, Terriss is the supplier. It's in their catalogue. I'll post this on another thread.

Larry, the NA Dispense unit I have is for bulk tank readings. Exact same principal as the Zahm, just not made of stainless. I've been using it for 2 years with minimal problems. It's fun to use base level stuff when you've had pin point and in-line equipment before. It keeps you honest.

Thanks Michael for the Terriss reference...I've been racking my brain trying to remember their name. Their bottle lifter is a great little tool. Based on a milk bottle lifter from the '40's