CO2 Vs. Scuba tank?

This is basic physics. Ever hear of the ideal gas law? If your tank size and temperature are the same, then the amount of gas in the tank is directly proportional to the pressure. Double the pressure, double the amount of gas, and (approximately) double the use for any particular application. (I say approximately because you can't really get all the gas out. If you require 30 psi pressure for your application, for example, the last 30 psi in the tank is useless.)

Earle

That's where it gets wierd. one company is saying they get 84 Ft^2 out of a cylinder the same size as a 40 Ft^2 O2 cyl, because it's CO2 in a liquid state. That's what I'm trying to figure, is a tank under 2000 PSI going to actually deliver only 40 Ft^2 when an 800 Psi tank of CO2 will deliver 84 ? The sites of CO2 tank makers only compare with a 150 Psi air tank, not a scuba cyl.

I don't know off hand whether CO2 enters a liquid state at room temperature and sufficient pressure, but I just got off the phone with my daughter who is a master's student in chemistry and she says it probably does. (She gave me a hard time too, like I should remember the physical characteristics of CO2 just because I have a physics degree.) If it goes liquid of course the ideal gas law doesn't apply and what the CO2 dealer is telling you is probably true. In that case go with the CO2. Note that this stuff is also dry and inert and has a lot of advantages over air because of that.

Earle

Depends on what the tank is filled with. CO@ tanks are fuilled with just that liquid co2. It expands to only a certain pressure. Scuba tanks are not filled with liquid gas but with actual compressed breathing air. Generally compresed to 2,000 - 4,500 psi depending on tank. If you use a scuba tank for truck use with tires, air tools etc you have to have it filled at a place that can fill to the 2k-3k psi. A standard compresor goes nowheres near that high. Generally only places that can fill it are dive shops. You'll next have to find oen that will fillthe tank. But general law they cannot fill a tank unless it is certified and owned by a PADI certified diver. I ran into this problem when I used to use scuba fill tanks for paintball guns.

Mr. Bill at a 4 way stop.....the vehicle with the largest wheels has the right of way My Jeep is not an SUV....your SUV is not a Jeep

Earle Horton did pass the time by typing:

It does. Only at atmopheric pressures does it sublimate from solid to gas without a liquid phase. Give it enough pressure and it becomes a liquid.

Check out

IMHO of you are going with a compressed gas solution for airing up tires CO2 is the only way to go. Without going into all of the chemistry CO2 is stored as a liquid and as such you can store much more gas than you can with compressed air. Above about 800 psi CO2 turns into a liquid, so the pressure in the tank stays constant until all of the liquid is used and then it, the pressure, drops rapidly. I've been using CO2 for years and it will fill up your tires and run air tools just fine,

BUT

again IMHO any compressed gas solution is a pain in the a$$ to maintain over time. You have to pay attention to how much gas you have, and it always seems to run out just when you need it. So now you have an empty tank, which means you've got to go get the thing filled up again. That going to cost you time and money. This is true with either CO2 or a scuba tank.

Like I said I've used and continue to use CO2, but installing a York air compressor is high on the list of mods scheduled for my Jeep.

Dean

Not sure, but I'm a scuba diver, and own a few tanks. Here's my take on it, though:

I'm not so sure I want 3000 lbs of compressed ANYTHING potentially bouncing around while offroading. 800 lbs "secured" makes me feel more secure than 3000 lbs "secured".

You need an expensive regulator to bring that 3000 lbs to a usable 0-120 LB range.

But the big kicker is:

I need to present my C-card in order to fill my scuba tanks. No dive shop as near as my local welding shop. No c-card needed at my local welding shop.

If I had a Dive Shop closer than the welding shop, the situation might tip the other way.

Heh. Forgot about that. Absolutely right. A lot more gas is generated by evaporating C02 than you can get out of a scuba tank.

Go with the C02, or nitrogen.

Just don't lay the tank on its' side while filling your tires.

There is a notice at the business where I exchange my tanks that says that no compressed gas should ever be transported inside a vehicle. If your CO2 tank should leak from the valve it could fill the vehicle's interior with CO2 and displace all the oxygen, which you need. I don't know how likely this is...

Earle

If your CO2

Not likely in my rig, no weatherstripping, so even with the doors and hard-top on, it is well ventillated. The site say their bottle of CO2 will fill my tire size 16 times from 10 to

30 Lbs, so i guess I could figure 8 times with air, or 2 fillups. Hardly worth the time or cost, and the welding shop is 35 miles away. I already own an O2 bottle, havent checked to see if they fill air to high pressures, and O2 won't do the job for me. Still in square 1, if i have to spend money I will go back to the compressor method.

Well, I would be more worried about flying debris knocking the valve off in an accident or roll over.

I took welding way back in school and watched the safety video. A tank that gets the valve knocked off is a torpedo and it will blast right through a concrete block and brick wall like it was paper.

My wife and i also worked for a scrap dealer in the 80's and we both did a mess of cutting for him. All the metal had to be in 2' x4' chunks for the shredder that filled up barges to go to Japan to build new cars. We were using cryogenic liquid O2 and propane in the cutting torches.

Man, the regular gas tanks have zip on a tank filled with liquid O2. Liquid O2 is serious nasty stuff! If it touches grease of any kind, it explodes. Use a tank for a few hours steady and the shutoff valve freezes solid, so if you have a hose or torch failure, there is no way to shut the sucker down.

The gas company rep that was teaching us about it said if the above happens, run like hell!

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's

Earle Hort>

Heh. That's why you need to carry also an oxygen tank! ;-) Just kidding!

Depends on the size of the leak. Like anything else, the seals and valves should be checked and maintained. If it's leaking, it's outta there.

Also, it's less of a problem when the Jeep top is off, but I could see how a winter hard top could collect enough C02 from a leaky tank and suffocate someone. Hmmm...

In that kind of situation, however unlikely, probably not vented enough. But if you had that heavy of a leak, you might be able to hear it? Hmmm, radio at full blast, road noise from big tires...

12 bucks for a C02 tank fill vs $350 and install for a compressor. I bought one of those 12v Hummmer compressors, and boy, what a slow pain in the ass it is. CO2 tanks are worth it to me just for the quietness of it. But then, my welding shop's a lot closer.

The belt driven model (York?) seems like the ticket if you're going to go that route.

>

My main thing is I'm not exactly rolling in money these days, I quit a good job to become a student a year and a half ago, and it doesn't pay well . An O2 tank could be kept with the regulator off, and the safety cap on, but I wont do that with O2 because of the possible reactions with petrochemicals, fire danger, perhaps even oxidization of my tires. Compressed air in the same bottle still has drawbacks, and I would rather spend money on a compressor than a tank that I can't refill at home. It's just too easy to forget to go to town and get it filled, and it's a 70 mile round trip. Using my O2 tank is just not a worthwhile option, if I will only get 2 air-ups out of it. Now I have to balance fill-time Vs. cost. That 110V compressor at the parts store only draws 2A at 110v, but it only flows 1.2 Ft^2@Min, (that's funny, it's not a link). I have a 12V compressor that will air-up in 80 minutes, but will be shopping compressors in the up-to $150 range, probably after Christmas. I could deal with 1/2 hour to bring 4, 35x12.50x15 tires up, but

1.3 hours is a bit ridiculous. The belt-driven is not an option, I have a 455 Buick stuffed under the hood of a 68 Jeepster, not a lot of room in there, and I will soon swap out my 60A alt for a 130A I have on the shelf.

I have a little baby tire pump that will work ok. It takes about 15 minutes per wheel. I also have a hand pump.

I never use them. When I had to drop my tires down with the old tires I had, 31x10.5's, I just drove easy to the nearest gas station. I now have 33x9.5's and haven't needed to drop the pressure. The fat tire boys can't follow me so I get to sit at the top and take photos of them all trying... LOL!

There also is a unit named a 'chuffer' I think that you can put in a spark plug socket on the head and it will act as an air pump powered by your piston.

It is 'slow' at idle but it works every time.... Rev it up and it pumps faster.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's

Paul Calman wrote:

On 07 Dec 2003 10:05 PM, Mike Romain posted the following:

I would be concerned about introducing fuel vapors into my tire, at the correct ratio for combustion, no less. Call me paranoid, I guess.

---------------------------------------------------- Del Rawlins- del@_kills_spammers_rawlinsbrothers.org Remove _kills_spammers_ to reply via email. Unofficial Bearhawk FAQ website:

Everywhere I fill my CO2 they say it is best not to store it inside ANY vehicle. Mine is in a rack bolted to the steel body inside. It also has a custom made collar around the regulator to protect it. I dont use this Jeep as a daily driver and feel that the risk I am taking is minimal. Lots of guys with XJ's run thier tanks the same way and so far no one has had an incident. So far so good.