Looking for a source of nitrogen gas for use in pressure / leak testing of an A/C system.

One source is a Welding Supply Shop, but adding up the price of a cylinder, a regulator, plus the gas, the cost is high when it will only be used a few times. Does anyone know of alternative sources of nitrogen gas, packaged in a disposable gas cylinder ?

Some sources that were checked:
Air Brush Propellant - None found that utilize nitrogen.
Air Duster - Found that "canned air" use.
Tire Inflator - No nitrogen, plus has sealant.

With the increased use of nitrogen for filling auto tires at many tire stores, I would expect someone would sell nitrogen in a can, but I did not locate any sources.

You might try the link below as a possible solution.

http://www.harborfreight.co...taf?Itemnumber=92807

The tank is for Argon gas but I'm pretty sure that you can use Nitrogen gas in the same type of cylinder because they are both noncombustable gases.

The tank is shipped empty and you will have to get it filled. The real problem is the regulator which you can get from you welding supply source or a specialty gas supplier like Airco, or MG Industries. But the regulators are not cheap.

P.S. Why do you have to use nitrogen gas for the leak test? Couldn't you just use compressed air? I'm assuming that you are going to be evacuating the AC system before you refill with new Freon.

Good luck.

~Bob

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"Its nice to be important.
Its more important to be nice."

[This message has been edited by FieroBobo (edited 08-11-2008).]

Don't paint ball guns use nitrogen?

There is a "air compressor replacement" for sale at lowes that includes a co2 tank with regulator.

I use a portable 8 gal. air tank for the race tires. I get Costco to fill it. On store won't do it, was not too friendly. Other store was nice and did it several times. You might get 125-150 psi.

You can use any dry gas such as any of the inert welding gases or even O2 or CO2. Humidity is the problem, you don' t want to introduce any more since it essentially consumes your dessicant's capacity to absorb moisture. Once you've completed your pressure test you're going to pull a vacuum on it anyway that will remove all of whatever gas you used to test it with so what you use isn't really important.

That being said, most people test system integrity by just pulling a high vacuum and letting it sit to see if the vacuum decreases over time, thus indicating a leak.

JazzMan

quote Originally posted by JazzMan: That being said, most people test system integrity by just pulling a high vacuum and letting it sit to see if the vacuum decreases over time, thus indicating a leak. JazzMan

You can use a gas that is 80% nitrogen...commonly called air.

A vacuum decay is not a reliable way of detecting a leak. The pressure differential is only 14.7 psi and it's in the wrong direction. A better test would be to pressurize the system with 100 psi of air and let it sit for a day or two.

You would want to do this before you change out the dessicant just in case. The vacuum is for drying out the system and the vacuum decay ensures that it's dry.

Thanks for all your responses !

Started out looking for an inexpensive source of nitrogen gas, a disposable canister would be ideal.

Some options require a gas tank and regulator, pushing the cost to over $100, even looked at nitrogen tanks for Paintball uses, still high initial cost. The cost of the Lowes co2 tank with regulator also totals over $100. If I was working on many systems, the capacity and refill capability would be great.

My first thought for filling with nitrogen was make an adapter with a tire valve and drive to the local membership store for a fill-up, but as Mike found they can be selective on what services they offer. Some managers must be looking at possible liability issues. A portable air tank is one option.

The use of an inert gas other than nitrogen might be an option. I know of Argon gas cylinder and regulator for use with a MIG welder that I may be able to borrow. I would guess that the cost of argon is more that nitrogen and that is why it is not used for A/C systems testing.

I was looking at nitrogen for leak testing with the additional benefit that the gas will assist in removing water vapor. The A/C system was non-functional when I bought the car, due to a leak since there was no refrigerate in the system. There was an oily mess around the condenser fittings, so one leak identified. Need to finish replacing the o-rings so it can be evacuated, tested, and charged.

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88 Stock GT
I'm not cheap, just fiscally responsible

When I don't have nitrogen I use shop air with a moisture trap and the old accumulator. I pump the system up to 150 psi and check for leaks. I then vacuum it down for 4 hours on and 4 hour off a during the day and then check that it holds vacuum. That will remove the moisture except from the accumulator.

I then install the new accumulator and repeat the vacuum 4on/4off all day then check it will hold over night. If it does, I charge mid-day when the temps are higher. I know some people assume the system is good if it will hold for an hour but I expect it to hold at least 8 hours and not flinch.

I mentioned this in another thread: Don't forget to replace the o-ring in the coupling under the front tire tub (just over the steering rack on the driver's side). That o-ring has gotten me twice now. I kept forgetting about it. Two systems would pressurize to 150 psi and hold short term but would leak down in 8 hours or over night. When you install the new OT in the short hose section below the accumulator, you tweak that connection under the tub and it will leak...very slowly. Yes, it sucks to replace the o-ring but you need to do it.

[This message has been edited by TK (edited 08-12-2008).]

Why not just vacuum the system, put in 2 cans of freon for your pressure test - this will only cost you about $12. If it does not leak then you are done!

You shouldn't really vent even R134 unnecessarily (and yes, I have) and the pressure isn't high enough to catch a leak. Static pressure alone when fully charged is in the 70 PSI range and that's far from the 300 the high side could see. If you have a BAD leak, one can will tell you but if you have the little leak that makes you recharge once a month, you need more pressure.

Nitrogen is nice to use as it won't hold moisture, but drawign a vacuum in the system will remove the moisture also, as mentioned earlier. The empty cylinders that you can buy for argon mixture gas welders wouold require a different valve assembly as each of the different regulated gases use a different type of valve and regulator adapter. You cannot use a regulator designed for oxygen service on a nitrogen, argon, carbon dioxide, etc. cylinder. Each type of gas has it's own fittings so you cannot mix your gases. Paintball cylinders usually use carbon dioxide.

Welding shops are required to refill cylinders with the proper gas as the fill threads are different and cannot be mixed. A nitrogen inflator regulator is available and can be set up for tire filling ( we have one at our shop for our trucks ) and that can be used to fill a portable air tank. But, that gas must be drawn out of a nitrogen cylinder designed for that service. We do carry smaller nitrogen cylinders for testing medical pipe installation but the customer rents those long term. It is possible to get the setup for personal use but it's not cheap. You are better off with using pressurized air and then vacuuming out the system.

Good luck.

Mark
Airgas Puritan Medical

Actually, any gas will hold moisture, none of them will repel water molecules. Air is over 70% nitrogen and it holds moisture just fine, which is good for us.

That being said, the process that pressurized gas suppliers use normally dehumidifies the air so a tank of nitrogen from a welding supply won't have any moisture in it. Neither will Argon, or CO2, or O2, or Helium, etc.

JazzMan

quote Originally posted by TK: When I don't have nitrogen I use shop air with a moisture trap and the old accumulator. I pump the system up to 150 psi and check for leaks. I then vacuum it down for 4 hours on and 4 hour off a during the day and then check that it holds vacuum. That will remove the moisture except from the accumulator. I then install the new accumulator and repeat the vacuum 4on/4off all day then check it will hold over night. If it does, I charge mid-day when the temps are higher. I know some people assume the system is good if it will hold for an hour but I expect it to hold at least 8 hours and not flinch.

Thank you for posting that. I'm not an a/c expert, but when I worked on servicing the Freon loops on the Space Shuttle that is the procedure we used. Of course we had a source of dry gas, (actually we used Helium so we could sniff for leaks). But you have to use pressure to look for leaks, vacuum won't cut it.

Vacuum is only for drying. We let the system sit a vacuum for days with the vacuum pump running on and off to make sure we not only got all the moisture, but there were as few molecules of anything in the system before we filled. Also, back in the day we used to vent freon right into the air...and lots of it. I think that hole in the ozone formed over Central Florida.

quote Originally posted by jscott1: Also, back in the day we used to vent freon right into the air...and lots of it. I think that hole in the ozone formed over Central Florida.

I remember when the issue started about vernting years ago. I was reading an article about the extent of damage venting freon was causing compared to other world issues. The space shuttle launching was used as an example (volcanoes were another one I remember). The statement was made that every time the shuttle was launched, there was more damage done to the ozone than the total amount of freon ever vented in the world, ever. Venting freon is such a non-issue. Then they made us switch to 134A because it does not do damage to the ozone, but you are still not allowed to vent it. Remember too, that countries all over the world are still venting freon. The US Navy still vents it when using it on ships (they use a lot). Reclaiming freon is the law, but it is the law for political reasons. The money that is being spent in the process could do thousand times more good if it was only properly directed.