I couldn't find a consistent or even roughly correct answer to this question on the web, so I got it somewhere else, namely a guy at American Welding Gas in Orlando. Maybe it will be useful to other people. Today he told me the pressure in a brand-new tank of beer gas should be around 1800 psi. That's at something like 75 Fahrenheit, and it will vary with the volume of the tank. For example, some 5-pound tanks are not the same size as others. Today I swapped an empty for a full aluminum tank, and when I got about a quarter of a mile away from the gas place, I turned back, because I realized the new tank was about 2" taller and might not fit my keezer. I swapped for a smaller steel tank. I'm going to measure my keezer next time.
A full tank will probably not come in at exactly 1800, but presumably, it won't be something grossly different, like 1500 or 2500, unless you have a pretty weird tank. The gas dude said "1800 to 2000." I saw what appeared to be at least three different sizes today, and they were all 5-pound tanks.
In case you're wondering what the pressure will be once the tank is in your keezer, chilled, unless the Ideal Gas Law has been repealed or amended, an 1800-psi tank will drop around 6.5% at 38. That's close to 1700. You don't need to know the whole law. You just need to know P/T = P/T for a constant volume and amount of gas. Convert the temperature to Kelvins. If you want to be really accurate, which serves no purpose in this case except to be annoying (1800/14.7 = 0.00816), add atmospheric pressure to the pressure on the gauge as a tiny, meaningless correction. If P2 is your pressure after a temperature change, P2= P1T2/T1.
I believe this is right. Check and see. I made a mistake once in 1973. It could happen again.
Now here is a question: is the EVAbarrier/Duotight system a good idea for beer gas, which often has to hold 35 psi? Duotight connectors are junk. Let's face it. They're very weak. They seem to work great for CO2 and beer, but I seem to be losing beer gas in a hurry. I blew through 5 pounds in a month, which is why I went to AWG today.
The directions for Duotight female threaded connectors say to adjust them finger-tight plus 90 degrees. This doesn't even work for CO2. Not even close. I had to use a wrench, and I went several threads past finger-tight. Now my CO2 system has zero leaks. It only has Duotight past the secondary regulator, though, so the pressure is low except when I'm carbonating a keg. I still have vinyl from the primary regulator to the secondary.
I redid the fittings and tubing on my beer gas system, and I'm under 800 pounds already. I tried them with and without nylon gaskets, and I found that with gaskets, you get so little thread engagement, the Duotights tear up when you try to tighten them properly. Then they have to be thrown out. Maybe I did something wrong and someone will want to chime in. I ended up applying keg lube to the threads and installing the fittings the same way I installed them on the CO2 system. No gaskets.
Should I go back to vinyl and barbs on the high side or what? I have EVAbarrier on the "out" side of my CO2 system, and it's fine, but I left vinyl on the "in" side because it took forever to get fittings and it was a real pain to change the "in" barb on my secondary regulator. I find vinyl or Tigan or whatever it is more flexible than EVAbarrier, and at 30 psi, it's not leaking at all. On the beer gas side, EVAbarrier and Duotight seem to be leaking at 35 psi, which is roughly the same as 30 and shouldn't be more of a challenge.
I pushed the EVAbarrier in all the way. I used EVAbarrier with clean ends. I don't know what could be wrong. I just made sure the cap on the Duotight gas disconnect on the keg was cranked all the way down. I suppose the keg could be leaking. It's a brand-new Torpedo keg, and I tightened the posts and seated the lid as well as I could. I have hosed it with Star San solution, and I haven't seen any bubbles. I have three crummy old kegs on the CO2 side, same disconnects, two old lid O-rings, and no leaks.
I put a steel valve compatible with Duotight on my beer gas regulator because old-style valves appear to be prone to failure. I am wondering if there is some kind of brass non-junk fitting that will connect this threaded valve to EVAbarrier or vinyl.
I'm inclined to think vinyl is superior for this purpose. Stiff hoses push the tanks around, and vinyl doesn't. Fittings that go with vinyl are metal, not plastic. The valves seem to be a weak point, but surely there is a fitting out there that will allow me to use the newer valves to connect to vinyl.
A full tank will probably not come in at exactly 1800, but presumably, it won't be something grossly different, like 1500 or 2500, unless you have a pretty weird tank. The gas dude said "1800 to 2000." I saw what appeared to be at least three different sizes today, and they were all 5-pound tanks.
In case you're wondering what the pressure will be once the tank is in your keezer, chilled, unless the Ideal Gas Law has been repealed or amended, an 1800-psi tank will drop around 6.5% at 38. That's close to 1700. You don't need to know the whole law. You just need to know P/T = P/T for a constant volume and amount of gas. Convert the temperature to Kelvins. If you want to be really accurate, which serves no purpose in this case except to be annoying (1800/14.7 = 0.00816), add atmospheric pressure to the pressure on the gauge as a tiny, meaningless correction. If P2 is your pressure after a temperature change, P2= P1T2/T1.
I believe this is right. Check and see. I made a mistake once in 1973. It could happen again.
Now here is a question: is the EVAbarrier/Duotight system a good idea for beer gas, which often has to hold 35 psi? Duotight connectors are junk. Let's face it. They're very weak. They seem to work great for CO2 and beer, but I seem to be losing beer gas in a hurry. I blew through 5 pounds in a month, which is why I went to AWG today.
The directions for Duotight female threaded connectors say to adjust them finger-tight plus 90 degrees. This doesn't even work for CO2. Not even close. I had to use a wrench, and I went several threads past finger-tight. Now my CO2 system has zero leaks. It only has Duotight past the secondary regulator, though, so the pressure is low except when I'm carbonating a keg. I still have vinyl from the primary regulator to the secondary.
I redid the fittings and tubing on my beer gas system, and I'm under 800 pounds already. I tried them with and without nylon gaskets, and I found that with gaskets, you get so little thread engagement, the Duotights tear up when you try to tighten them properly. Then they have to be thrown out. Maybe I did something wrong and someone will want to chime in. I ended up applying keg lube to the threads and installing the fittings the same way I installed them on the CO2 system. No gaskets.
Should I go back to vinyl and barbs on the high side or what? I have EVAbarrier on the "out" side of my CO2 system, and it's fine, but I left vinyl on the "in" side because it took forever to get fittings and it was a real pain to change the "in" barb on my secondary regulator. I find vinyl or Tigan or whatever it is more flexible than EVAbarrier, and at 30 psi, it's not leaking at all. On the beer gas side, EVAbarrier and Duotight seem to be leaking at 35 psi, which is roughly the same as 30 and shouldn't be more of a challenge.
I pushed the EVAbarrier in all the way. I used EVAbarrier with clean ends. I don't know what could be wrong. I just made sure the cap on the Duotight gas disconnect on the keg was cranked all the way down. I suppose the keg could be leaking. It's a brand-new Torpedo keg, and I tightened the posts and seated the lid as well as I could. I have hosed it with Star San solution, and I haven't seen any bubbles. I have three crummy old kegs on the CO2 side, same disconnects, two old lid O-rings, and no leaks.
I put a steel valve compatible with Duotight on my beer gas regulator because old-style valves appear to be prone to failure. I am wondering if there is some kind of brass non-junk fitting that will connect this threaded valve to EVAbarrier or vinyl.
I'm inclined to think vinyl is superior for this purpose. Stiff hoses push the tanks around, and vinyl doesn't. Fittings that go with vinyl are metal, not plastic. The valves seem to be a weak point, but surely there is a fitting out there that will allow me to use the newer valves to connect to vinyl.
