Does Argon Get Impure As The Tank Nears Empty?

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Last night I was TIGging aluminum boxes for my van, doing outside corner joints in 6061 16 gauge, then inside corner joints, getting low on argon I decided to try one more time the Diversion 180. I hadn't used it in a couple of months. I couldn't do a thing with it. I found it hard to get a clean puddle, once I was sucessful with a liquid puddle, I would hit it with rod, instant ball of black coated snot. It would drip off the rod onto, and roll across the work. It was as though a thin blackish gray ball filled with liquid aluminum. After studying it a while wondering if I was getting enough gas, (I dont have a flow regulator). I satisfied myself that I did indeed have 22 CFH of argon, I turned attention to an air leak. I found no reason to believe I had one. Giving up on that machine I switched to the Dialarc, It worked fine for a while, then it too started acting up in the same way. Tank pressure was low enough to barely lift the gauge off the rest, but hose pressure remained at or near 22 CFH. Am I missing the obvious? I used two different regulators, they behaved the same, With pedal depressed The gauge never dipped below set pressure.Is the last of the gas in a tank dirty, impure or something? I bought a new tank but haven't tried it yet.
Reply:Heck, hook up that new one and see I have used my 330 cu.ft. tank for 30-60 min after it quit reading on the gauge.It did give problems eventually though - even though the flow meter still read correctly.Dave J.Beware of false knowledge; it is more dangerous than ignorance. ~George Bernard Shaw~ Syncro 350Invertec v250-sThermal Arc 161 and 300MM210DialarcTried being normal once, didn't take....I think it was a Tuesday.
Reply:your saying hose PRESSURE at or near 22cfh. that is a contradictory measurement.heres how I figure it, speaking in terms of FLOW-METER'S!most welding I do with 20-25 cfh. the FLOW-METER is regulated down to 60 psi (usually) and you set your FLOW-RATE based on that 60psi acting pressure. if TANK PRESSURE dips below 60-psi, the flow meter is not able to deliver my desired 20-25cfh. that is when bad things happen.FLOW-REGULATORS I am unsure of. I do not understand how they can regulate PRESSURE and try and tell you that your achieving a desired FLOW-RATE. they have no idea what I am running as far as gas-lens, or any other "obstructions" that may be between the device and the weld. the fact that you can set to a FLOW-RATE on the guage without any gas actually flowing tells me they are full of bull and need to be thrown away.just my opinion of course and I am not quite an expert in pneumatics or pressure/flow-rate relationships of argon.just out of curiosity, how do you determine that you have 22cfh at the torch?bosses stuff:trailblazer 325maxstar 200my stuff:sa 200fronius transpocket 180100 amp Lincoln w/f97 f350 DITKevin
Reply:Originally Posted by 92dlxmanyour saying hose PRESSURE at or near 22cfh. that is a contradictory measurement.heres how I figure it, speaking in terms of FLOW-METER'S!most welding I do with 20-25 cfh. the FLOW-METER is regulated down to 60 psi (usually) and you set your FLOW-RATE based on that 60psi acting pressure. if TANK PRESSURE dips below 60-psi, the flow meter is not able to deliver my desired 20-25cfh. that is when bad things happen.FLOW-REGULATORS I am unsure of. I do not understand how they can regulate PRESSURE and try and tell you that your achieving a desired FLOW-RATE. they have no idea what I am running as far as gas-lens, or any other "obstructions" that may be between the device and the weld. the fact that you can set to a FLOW-RATE on the guage without any gas actually flowing tells me they are full of bull and need to be thrown away.just my opinion of course and I am not quite an expert in pneumatics or pressure/flow-rate relationships of argon.just out of curiosity, how do you determine that you have 22cfh at the torch?
Reply:It turns out that if moisture is the impurity of concern, it actually does tend to show up more and more as the cylinder pressure goes down.  At higher pressures, the moisture tends to condense on the cylinder walls.  As you drop the pressure the moisture will vaporize, come off of the cylinder wall, and start to enter the gas stream.  If you really want to know how much moisture is in a given cylinder, always have it analyzed at the lowest possible pressure.Experience is something you get right after you need it
Reply:Does the argon in the tank get "impure" as the tank (cylinder) nears empty?  No.But it certainly can give you flow-related issues.  (especially if the flow 'meter' or regulator(s) act-up at the lower tank pressure).  I'll bet a donut that if you had a real "flow-meter" showing the flow rate of the shielding gas as the tank got near empty that you would have seen some flow 'irregulariities'.Just change the cylinder out for a full one and refill the empty one.  The best laid schemes ... Gang oft agley ...
Reply:> Does Argon Get Impure As The Tank Nears Empty?Sure.  It's like when you're drinking coffee, and you get to the grinds at the bottom.   Has anyone else ever been affected by argon "grinds"?    LOL Originally Posted by Fred sIt turns out that if moisture is the impurity of concern, it actually does tend to show up more and more as the cylinder pressure goes down.  At higher pressures, the moisture tends to condense on the cylinder walls.  As you drop the pressure the moisture will vaporize, come off of the cylinder wall, and start to enter the gas stream.  If you really want to know how much moisture is in a given cylinder, always have it analyzed at the lowest possible pressure.