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Alternate Gases For Pressure Checking

69-er on Tue June 22, 2010 8:02 PM User is offlineView users profile

I saw a post on using argon successfully to leak check a system. How about Co2/argon mixed gas? Is 134 still better to check for leaks because of the small molecular size?

I also seem to see a lot where a sniffer is best to use for leak checks, when using 134, but what about leaving the gauges on for a few days for this check? Might this not work too well because they might tend to leak more than a tight system?

NickD on Wed June 23, 2010 6:50 AM User is offline

EPA lets you waste a can (or two???) to test for leaks with a good electronic detector in a draft free space, I added the draft free space. Gauges don't work, static pressures will be the same even if you leak out a half a can, but will shift with ambient. You could fill it with 150 psi of air, dip your vehicle in a lake and look for bubbles.

Nobody puts more R-134a into the environment than the manufacturers of MVAC systems, but the EPA turns their head the other way to this very strong fact. Can only wonder if they are getting fringe benefits from these manufacturers. I have difficult telling the difference when looking under the hood and those piles of stuff my dog leaves behind. But the good news today after watching these many TV ads, you can buy a pile of problems, interest free. All EPA created problems, they are good at that.

mk378 on Wed June 23, 2010 10:26 AM User is offline

There's no reason to use argon instead of nitrogen unless of course you have some argon on hand and not nitrogen. Sniffers exist for refrigerant and CO2, that's why those are used. When pressure testing with refrigerant, do not exceed the saturation pressure (pressure corresponding to the ambient temperature where the refrigerant will start to condense). Use a proportion of refrigerant in inert gas (nitrogen, argon, etc-- but not air or oxygen!), the refrigerant acts as a "tracer" to be detected by sniffing and the other gas raises the overall pressure to open up leaks. Car evaporators are not built to withstand much more than 150 psi so don't exceed that pressure with non-condensable test gas.

69-er on Wed June 23, 2010 3:23 PM User is offlineView users profile

Quote
Originally posted by: mk378
There's no reason to use argon instead of nitrogen unless of course you have some argon on hand and not nitrogen.

Yes, I have a cylinder of Co2/argon for my mig welder, but no sniffer for C02.

Quote
Originally posted by: NickD
Gauges don't work, static pressures will be the same even if you leak out a half a can, but will shift with ambient.

I see how the pressure might not change with 134 if the pressure raises to the point of condensing the gas. But, is using gauges to check for pressure losses with Co2/argon a reliable method? I can see if the Co2/argon molecules were larger than 134, it might not find the real small leaks.

Edited: Wed June 23, 2010 at 3:26 PM by 69-er

mk378 on Wed June 23, 2010 3:42 PM User is offline

The issue with "small molecules" is actually not leakage, but diffusion through intact "airtight" materials like rubber and glass. (Argon might count as "small" since it exists as single atoms, not molecules). You won't be able to find really small leaks just by looking for pressure loss anyway. Realize that pressure will change with temperature even with a noncondensable gas in a leakproof system, masking the effect of small leaks. Bottom line is that MIG gas should be fine for leak tests.

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