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Scuba Forum / General / December 2003CO2 through SCUBA 1st Stage Regulator
I'm thinking about using an old SCUBA tank to hold CO2 (liquid) and mounting it in my Jeep for "onboard air" for filling up tires after going offroad or running power tools. When the CO2 goes through the regulator at a high flow rate, the regulator might frost up somewhat (at least this sometimes happens with my CO2 regulator on my normal CO2 tank). The tank pressures associated with CO2 (approximately 800 psi normally, perhaps 1100 psi after a fill) are considerably less than the 3000 psi fow which the SCUBA cylinder was originally certified and since the tank would be carrying liquid CO2, it would contain a higher capacity of expanded gas than if it was carrying 3000 psi air. Assuming that I can find a cheap 1st stage, what is the intermediate pressure coming off the low pressure ports of most 1st stages? Any potential problems with having that cold of a gas going through the 1st stage? What would be the maximum flow rate that one could probably expect from such a 1st stage? > I'm thinking about using an old SCUBA tank to hold CO2 (liquid) and > mounting it in my Jeep for "onboard air" for filling up tires after [quoted text clipped - 11 lines] > through the 1st stage? What would be the maximum flow rate that one > could probably expect from such a 1st stage? Hmm.... I dunno abou carrying LIQUID CO2 in a Alu scuba tank, excessive cold tends to make Alu brittle. if it was steel tank tho. it should work. rhys >> I'm thinking about using an old SCUBA tank to hold CO2 (liquid) and >> mounting it in my Jeep for "onboard air" for filling up tires after [quoted text clipped - 16 lines] > >rhys It's not cold when it's just sitting in the tank. It does chill upon expansion, so I expect the first stage will very likely freeze up during use. > >> I'm thinking about using an old SCUBA tank to hold CO2 (liquid) and > >> mounting it in my Jeep for "onboard air" for filling up tires after [quoted text clipped - 18 lines] > > It's not cold when it's just sitting in the tank. surely you jest! you can not be serious? > It does chill upon expansion, > so I expect the first stage will very likely freeze up during use. > > It's not cold when it's just sitting in the tank. > > surely you jest! > you can not be serious? Does the outside of any liquefies gas tank feel cold to touch? Cheers David M > > > It's not cold when it's just sitting in the tank. > > > > surely you jest! > > you can not be serious? > > Does the outside of any liquefies gas tank feel cold to touch? Liquid Oxygen and Liquid Nitrogen have been known to be a bit cold to the touch. > > > > It's not cold when it's just sitting in the tank. > > > [quoted text clipped - 5 lines] > Liquid Oxygen and Liquid Nitrogen have been known to be a bit cold to the > touch. ...at atmospheric pressure. > Liquid Oxygen and Liquid Nitrogen have been known > to be a bit cold to the touch. Whether a gas is liquid or not is a function of the temperature and the pressure... Some gases can be readily liquified by just increasing their pressure a moderate amount... Others require so much of a pressure increase that from a practical standpoint, we must decrease their temperature also... CO2 and propane fall into the former category, nitrogen and oxygen fall into the latter... If I remember correctly, it is a function of their vapor pressure which is a function of temperature... CO2 readily goes into solution in water and the colder the water the more CO2 will go into it... This fact in addition to the carbonic acid that is produced is what gives us the distinctive flavor and bubbles of carbonated drinks... This is also why it is so easy to create your own carbonation vessel out of no more than a 2-liter soft drink bottle and a metal schrader valve for a bulkhead connector in the bottle top... You only need to pressurize the carbonation vessel to about 30-35 psi and shake vigorously to carbonate the liquid... I usually pressurize to 65 psi so that I don't have to add carbonation as many times when I started out with a warmer than optimal liquid... Optimal temperature is probably around 35-40F... I've also tried oxygenating drinks... The bubbles are smaller and the drink does not have the same flavor due to the lack of carbonic acid... >> >Hmm.... I dunno abou carrying LIQUID CO2 in a Alu scuba tank, excessive cold >> >tends to make Alu brittle. if it was steel tank tho. it should work. [quoted text clipped - 5 lines] >surely you jest! >you can not be serious? I'm not sure if you're joking, since I thought you had a scientific background and would know this. At room temperature (25C), CO2 condenses to a liquid at 50 bar. Here's a phase diagram that helps explain it: http://www.chemicalogic.com/download/co2_phase_diagram.pdf A tank of CO2 sitting around will either contain a liquid or a gas depending on the pressure, but it will not be cold (until you open the valve, that is. At that point, if it is in a liquid phase, it will give up a large amount of latent heat and get seriously cold, usually forming dry ice). Alan > Hmm.... I dunno abou carrying LIQUID CO2 in a Alu scuba tank, excessive cold > tends to make Alu brittle. if it was steel tank tho. it should work. Irregardless of whether it really is cold or not, aluminum would be perfectly acceptable since commercial soft drink fountains often use aluminum for their CO2 tanks... Luxfer makes them also... Common IP would be around 130 psi +/- 10. You could dial that down... argon regs generally run around 80psi or so. Even that is more than you'd really need for your tires, and getting the tank filled with CO2 while fitted with a K-valve MAY be problematic (not to mention a hazard). See if you can fit a regular kegerator CO2 valve and then you can use a kegerator regulator as well... or check here. http://www.morebeer.com/index.html?page=detail.php3&pid=D1052 $129 for a 20-pound tank. $55 for a reg. --- Rich http://richlockyer.tripod.com/ > I'm thinking about using an old SCUBA tank to hold CO2 (liquid) and > mounting it in my Jeep for "onboard air" for filling up tires after [quoted text clipped - 9 lines] > intermediate pressure coming off the low pressure ports of most 1st > stages? Between 130 and 150 psi depending on brand and how it was adjusted when last serviced. > Any potential problems with having that cold of a gas going > through the 1st stage? How cold do you expect the gas to be? Expanding gas cools. That's true of air just like it is true of CO2. Since the expansion is somewhat greater from liquid to gas, I would assume that it would be a bit colder, but can't really tell how cold. On the other hand, I would assume that a gas that is not cold enough to damage the rubber in your tires, would not be cold enough to damage the parts in your regulator. Frost buildup on the outside of the regulator would not seem to be critical to its operation, but you might get better information from somebody that actually uses the things in cold climates. > What would be the maximum flow rate that one could probably expect from such a 1st stage? It would be approximately the same as the flow you would get out of a low pressure port now. It is certainly adequate for filling tires. Lee >to damage the parts in your regulator. Frost buildup on the outside of the >regulator would not seem to be critical to its operation, but you might get >better information from somebody that actually uses the things in cold >climates. I'd put an OPV on the reg to save the hose (and maybe a hand) in case the reg freeflows. --- Rich http://richlockyer.tripod.com/ > I'm thinking about using an old SCUBA tank to hold CO2 (liquid) and > mounting it in my Jeep for "onboard air" for filling up tires after [quoted text clipped - 11 lines] > through the 1st stage? What would be the maximum flow rate that one > could probably expect from such a 1st stage? One more thing I should have mentioned. Mark this tank very, very clearly. Picking it up and using it for breathing gas is likely to be a mistake you only get to make once. Lee > > I'm thinking about using an old SCUBA tank to hold CO2 (liquid) and > > mounting it in my Jeep for "onboard air" for filling up tires after [quoted text clipped - 17 lines] > > Lee Better to buy a co2 tank and a cheap regulator. No potentially deadly mistakes then. Probably cheaper too. You can rent co2 or argon tanks here for about 18 bucks a year. Just exchange them when you run 'em dry. -- An amateur built the ark ....professionals built the Titanic. > Better to buy a co2 tank and a cheap regulator. No potentially deadly mistakes > then. Probably cheaper too. You can rent co2 or argon tanks here for about 18 > bucks a year. Just exchange them when you run 'em dry. Oh, I already own a 20# CO2 tank and regulator, but I was recently bidding on some old SCUBA tanks on eBay and made the mistake of bidding on multiple tanks at the time time... Hey, it was my first attempt at eBay and as luck would have it, no one else bidded on these tanks... I've got a few steel and aluminum tanks headed my way and I figured that I would get some use out of them... Some of them are out of hydro and using them for CO2 would still be safe even if they were some of the 6351-T6 alloy (of which a few out of the millions that were manufactured) that ruptured... I've been renting a large O2 tank for welding and I'll transfer some of the O2 into a couple of them for use while flying at night and return the large O2 tank so that I no longer will be having to rent it at $9 per month... So far, I've won the bid on 3 of the tanks and my luck will probably have me winning the bid on a few more before it is all over... Oh well, I'll just chalk it up as a "learning experience" and since I can still use the tanks for other stuff, it's not that big of a deal... As "learning experiences" go, it was a rather cheap one (i.e. no compound fractures or missing body parts involved this time)... Although I would have to buy a regular CO2 valve to get a gas supplier to fill the tank and they would probably expect a recent hydro, I figure that I can rig up a fill whip with some adapters and transfer the liquid CO2 from my actual CO2 tank to the SCUBA tanks that I'll be using for CO2... Of course, I'll mark these tanks so that I won't make a mistake and use them for air tanks... On my other CO2 tank, I've already made it so that it can fill tires, run air tools, and make my own carbonated beverages... So, what can I expect for the flow rate from a 1st stage? > So, what can I expect for the flow rate from a 1st stage? Far more than needed to inflate a flat tire. Now, what are you really up to? > Far more than needed to inflate a flat tire. Inflating tires can withstand a slower flow rate than seating tires after you've popped them off their bead... Sometimes that happens if you deflate them too much before going offroad... There is also the issue of wanting the regulator to be able to handle an impact wrench... > Now, what are you really up to? Just what I originally posted... Onboard air for my Jeep... The one that I originally configured for it has kind of gotten dedicated to carbonation of drinks... Here's a link to someone else who has done it: http://www.stu-offroad.com/co2/co2-1.htm > > Far more than needed to inflate a flat tire. > > Inflating tires can withstand a slower flow rate than seating tires after > you've popped them off their bead... Sometimes that happens if you deflate > them too much before going offroad... There is also the issue of wanting the > regulator to be able to handle an impact wrench... Use ether to re-seat the bead. > Use ether to re-seat the bead. With or without a supplemental spark? <grin> > > Use ether to re-seat the bead. > > With or without a supplemental spark? <grin> Sparingly, with a wooden match thrown at it. > > > Far more than needed to inflate a flat tire. > > [quoted text clipped - 5 lines] > > Use ether to re-seat the bead. It can be spectacular when you do that.....especially when you over-apply the ether. But it does work well. -- An amateur built the ark ....professionals built the Titanic. >> So, what can I expect for the flow rate from a 1st stage? > >Far more than needed to inflate a flat tire. > >Now, what are you really up to? CO2 can be a little more volumetrically efficient than air. For example, a typical "T" tank of nitrogen (56" x 9") holds about 304 ft3 at 2650 psi, while the same size tank of liquid CO2 (at 400 psi) holds about 437 ft3. > CO2 can be a little more volumetrically efficient than air. For example, a > typical "T" tank of nitrogen (56" x 9") holds about 304 ft3 at 2650 psi, while > the same size tank of liquid CO2 (at 400 psi) holds about 437 ft3. From what I understand, you get about 3 times the 'air' supply for running air tools and such from CO2 vs a similarly sized SCUBA tank... Plus, it's easier to transfer most of the CO2 from one tank to another with CO2... With air, you can only transfer half of it from one tank to another... With CO2, you should be able to transfer all of it except for around 800 psi of gas (assuming that you invert the doner tank)... > > CO2 can be a little more volumetrically efficient than air. For example, a > > typical "T" tank of nitrogen (56" x 9") holds about 304 ft3 at 2650 psi, [quoted text clipped - 7 lines] > you should be able to transfer all of it except for around 800 psi of gas > (assuming that you invert the doner tank)... nope, only half. -- An amateur built the ark ....professionals built the Titanic. >> > CO2 can be a little more volumetrically efficient than air. For example, a >> > typical "T" tank of nitrogen (56" x 9") holds about 304 ft3 at 2650 psi, [quoted text clipped - 9 lines] > >nope, only half. No, almost all. You're thinking about gas transfer, where the pressure will equalize between the two cylinders. Above ~50 bar (see my previous post), CO2 is a liquid at room temperature. As long as the liquid can flow between the two tanks, it will be possible to almost completely fill one tank and empty the other. > No, almost all. You're thinking about gas transfer, where the pressure will > equalize between the two cylinders. Above ~50 bar (see my previous post), CO2 > is a liquid at room temperature. As long as the liquid can flow between the two > tanks, it will be possible to almost completely fill one tank and empty the > other. So I can use CO2 in one of my doubles, thus using the CO2 in one tank to force the last cf out of the other, and get rid of my Spare-Air???? In article <%gbzb.142788$Ec1.5763743@bgtnsc05-news.ops.worldnet.att.net>, mike gray, CID <mikegrayCID@worldnut.nut> wrote: > > No, almost all. You're thinking about gas transfer, where the pressure will > > equalize between the two cylinders. Above ~50 bar (see my previous post), [quoted text clipped - 6 lines] > So I can use CO2 in one of my doubles, thus using the CO2 in one tank to > force the last cf out of the other, and get rid of my Spare-Air???? Sure. Just make sure you're upside down and backwards when you make the valve switch <g>. On Wed, 03 Dec 2003 01:47:39 GMT, "mike gray, CID" <mikegrayCID@worldnut.nut> wrote ... >So I can use CO2 in one of my doubles, thus using the CO2 in one tank to >force the last cf out of the other, and get rid of my Spare-Air???? If you were doing something that required filling up large lift bags, taking a CO2 bottle with you instead of relying on air tanks would be more efficient... The key issue would be ensuring that the take was upright durng the filling process, thus it could really suck if you attempted to use it for dry suit or BC inflation... > Hey, it was my first attempt at eBay and as luck > would have it, no one else bidded on these tanks... I've got a few steel and > aluminum tanks headed my way and I figured that I would get some use out of > them... You could send me a tank :) I spent all my insurance on new gear, but still lack a tank and reg. I've had to spend the money I was saving for the reg on my 4WD, the head gaskets blown, so I've now gotta take off the head and install a new gasket, and I'll change the timing while I'm at it. It's not much use having all the gear to dive and not having the transport to get to the dive site, I figure it's better to have the transport to get to a gear rental shop and the site... :) rhys > I've had to spend the money I was saving for the reg on my 4WD, the head > gaskets blown, so I've now gotta take off the head and install a new gasket, > and I'll change the timing while I'm at it. It's not much use having all the > gear to dive and not having the transport to get to the dive site, I figure > it's better to have the transport to get to a gear rental shop and the > site... :) That's a very expensive head gasket. > One more thing I should have mentioned. Mark this tank very, very clearly. > Picking it up and using it for breathing gas is likely to be a mistake you > only get to make once. Especially if you were inverted and started to breathe off of that tank and ended up breathing liquid CO2... <grin> > One more thing I should have mentioned. Mark this tank very, very clearly. > Picking it up and using it for breathing gas is likely to be a mistake you > only get to make once. Since he presumably won't be putting a second stage on this particular first, he could potentially rethread the ports. That would make it much more difficult to screw up badly, since it would require some significant effort to do so.  SignatureSteve The above can be construed as personal opinion in the absence of a reasonable belief that it was intended as a statement of fact. If you want a reply to reach me, remove the SPAMTRAP from the address. > Since he presumably won't be putting a second stage on this particular first, he > could potentially rethread the ports. That might not be that bad of an idea since for this useage, having ports that were threaded in 1/4" NPT would be best since that is the most common thread used for the air tool quick connects... Not having the capability to do this though, I would just use the standard ports and have a small hose that converted from a LP port to a 1/4" NPT thread... > > Since he presumably won't be putting a second stage on this particular > first, he [quoted text clipped - 5 lines] > do this though, I would just use the standard ports and have a small hose > that converted from a LP port to a 1/4" NPT thread... buy a tap. -- An amateur built the ark ....professionals built the Titanic. Why not just use air? It's cheaper than CO2 and its not as much a pain in the a.s. Besides...using CO2 on power tools will only mess up the tool > I'm thinking about using an old SCUBA tank to hold CO2 (liquid) and > mounting it in my Jeep for "onboard air" for filling up tires after [quoted text clipped - 11 lines] > through the 1st stage? What would be the maximum flow rate that one > could probably expect from such a 1st stage? > Why not just use air? It's cheaper than CO2 and its not as much a pain in > the a.s. Besides...using CO2 on power tools will only mess up the tool. He needs portability and can carry more liquid CO2 than air in the same sized bottle. Hoe does CO2 mess up power tools? Lee > > I'm thinking about using an old SCUBA tank to hold CO2 (liquid) and > > mounting it in my Jeep for "onboard air" for filling up tires after [quoted text clipped - 11 lines] > > through the 1st stage? What would be the maximum flow rate that one > > could probably expect from such a 1st stage? > Why not just use air? It's cheaper than CO2 and its not as much a pain in > the a.s. Besides...using CO2 on power tools will only mess up the tool I guess it depends upon where you get your CO2... I get a 20# tank filled up locally for around $8... About the same price as a refill on a SCUBA tank, but you get about 3 times as much 'air' out of it to run your tools... There is also the issue of being able to use my one current hydro CO2 tank to get the gas from the supplier and then being able to transfer most of it to the other tanks that might not have a current hydro... Although I could do that with air, I would only be able to transfer half of the original tank to the new tank... Since I would be transferring liquid, I could transfer most of it to the new tank... There are a lot of people who use CO2 for the air tools and I have not heard any reports of them messing up the tools... You have to add a little oil to the tool periodically, but you need to do that with air also... |
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