Argon Bottle Question

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I bought an argon bottle back in March of this year.  I am relatively new to TIG welding and have been trying to enhance my skills but do not really think I have used a lot of Argon.I am using a flow regulator with a high side pressure gauge not a pressure regulator with two pressure gauges on the regulator.  Am I correct in my belief that I will get 20 cfh whether I have 2000 psi or 1300 psi showing on the regulator from the bottle and thus at the torch?I am going to make an assumption that I average 20 cfh of flow. I do not believe that I have TIG'ed (actual argon flow) more than 2-3 hours (probably less) if I only count the time the torch valve is open.  Thus I should have only used 40 to 60 cubic feet of argon.  Since I have a 250 Cu ft tank I have presumably used less than 25% of the tank.  I am presuming that a 250 cf bottle contains 250 cf of argon that will flow for either 250 hours at 1 cfh or 1 hour at 250 cfh.The bottle pressure when it was new was 2000 psi (130 kg/cm2)  and now is at 1300 psi  (92 kg/cm2).  It seems to me that the pressure has decreased much more rapidly than I would expect.  I have "soaped" each connection both when first hooked up and again today and find no leaks.  Does it sound as if I have a leak that I can not find, or is this pressure drop seem reasonable for the amount of use I have made of the argon?  Does argon pressure not drop in a linear fashion with the cubic feet of argon that is used? My oxygen and acetylene bottles have never had pressure drop this way but I do not have a flow meter on them (only pressure regulators) and thus other than the charts for tips and pressures have no real idea what the flows on them have been.Thanks for any help.Last edited by pine; 06-10-2013 at 02:37 AM.Reason: correct units of pressure
Reply:I have no clue what kind of gauge you really have.Traditionally the first gauge shows tank pressure. The second gauge show output pressure rated in CFH. As the tank pressure drops the output pressure stays constant(or trys to).Sounds like you lost a good deal of money in argon. You should invest in a quality flowmeter. Personally I like the ball/glass tube type.Weld like a "WELDOR", not a wel-"DERR" MillerDynasty700DX,Dynasty350DX4ea,Dynasty200DX,Li  ncolnSW200-2ea.,MillerMatic350P,MillerMatic200w/spoolgun,MKCobraMig260,Lincoln SP-170T,PlasmaCam/Hypertherm1250,HFProTig2ea,MigMax1ea.
Reply:130 psi when new doesn't sound right at all. My tank was around 2000 psi when I bought it. Check that. I just did the conversion and 2000 psi is 137 bar. Is your regulator marked only in bar or also psi?Going to your question, I don't know why you would assume your regulator is putting out a fixed 20 cfh. Usually there is a low pressure side knob to adjust flow rate, or at least psi. A photo of your regulator would probably be helpful.Whether the regulator will put out constant cfm regardless of tank pressure has a lot to do with how expensive it is. Cheaper regulators may require adjusting as tank pressure changes to hold constant cfm or psi on the low pressure side.Last edited by joshuabardwell; 06-10-2013 at 02:12 AM.Everlast PA160-STH... and that's about it!
Reply:Originally Posted by shovelonI have no clue what kind of gauge you really have.Traditionally the first gauge shows tank pressure. The second gauge show output pressure rated in CFH. As the tank pressure drops the output pressure stays constant(or trys to).Sounds like you lost a good deal of money in argon. You should invest in a quality flowmeter. Personally I like the ball/glass tube type.
Reply:The pressure does indeed drop linearly, it is proportional to the amount of argon by way of the ideal gas law PV= nRT.  V is constant, so assuming Temp is constant, and of course R is constant, it only leaves n as the independent variable.If you're truly worried, you can hook up a balloon to the regulator outlet, fill it up, noting the flow rate and how long you let it fill.  You can dunk the argon filled balloon in water and measure the displacement (and thus argon volume), then compare it to the calculated displacement of Flowrate x balloon fill time (seconds/3600 to convert fill time in seconds to hours).  Obviously you have to fill it slowly and at a constant rate (as constant as possible).  If the balloon is roughly spherical, you can measure the circumference and use V= 0.0169 * C³ to get it's volume without having to measure it's water displacement.  Lots of work though, and you're gonna waste more argon in the process.  Last edited by Oscar; 06-10-2013 at 05:19 AM. 1st on WeldingWeb to have a scrolling sig! HTP Invertig 400HTP Invertig 221HTP ProPulse 300HTP ProPulse 200 x2HTP ProPulse 220MTSHTP Inverarc 200TLP HTP Microcut 875SC
Reply:Have you check the valve at the top of the tank I have heard the valve should be opened to the max to seal the valve in an open condition. If the valve is open to half the turns to max it could be leaking around the stem.Also the ball type flow meter shows the actual volume of gas passing around the ball.  That is why the have different scales for different gases.
Reply:Originally Posted by pineThe reason I would assume my regulator is putting out a fixed 20 cfh is I have set it on the glass tube/ball to read that.
Reply:I treat it just like the Oxygen bottle.  Full open or full closed, no in between so that the valve seats properly.  The other reason I do not think there is a leak, that I have not found, is that the flow ball drops to the bottom and does not move when the torch valve is turned off.  If there was a leak I would think I would get a least a small movement from the ball.  Of course it may not be that sensitive to show a real slow leak.
Reply:Well, there's only a few possible options:1) There's a leak in the system and you're losing gas somewhere you're not noticing.2) The flow-rate is reading wrong.3) Your regulator is not reading correct pressure.4) Your welding time is not what you think it is.I don't trust the flow meters to show a small leak. Below a certain point, I don't think it would be enough pressure to raise the ball. I think one could easily be losing, say, less than 0.5 cfh of gas to a leak and not know it.If you want to leak test your system, one way to do it is to pressurize the system with the flow-meter open and then close the valve on top of the cylinder. Note the regulator's pressure. Come back, say, 15-30 minutes later and note how much drop there has been.Everlast PA160-STH... and that's about it!
Reply:You're pretty close on your usage.  60cf is 24% of 250cfGoing from 2000psi to 1300psi is a reduction of 35%Also, everytime you strike an arc, there is a surge of argon before flow settles to the reading.Btw, the manufacturer no longer says you need to open high pressure bottles fully to back-seat.  But it also does no harm.http://weldingweb.com/vbb/showthread.php?t=268311Dave J.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:The flow meter pictured shows units of flow being in liters per minute, not cubic feet per hour as you are claiming.  If you're flowing 20 lpm, it's roughly about twice that in terms of cfh (20 lpm is actually ~42 cfh).Also, some flow meters read at the top of ball, vs. middle of ball, vs. bottom of ball.  Are you sure you're reading yours correctly?In any event, yet another possiblity is that your tank pressure gauge is not accurate, and it will read zero when there is still a lot of pressure left (I have one flowmeter that has this problem - inaccurate at low tank pressure.  It still works great aside from that issue).
Reply:What kind of welds are you making?  Short welds, say 6 1"  long welds will use up more argon then 1 6" weld due to post flow.
Reply:I want to thank everyone for their inputs.  While none gave me a direct answer to the problem they did help focus my troubleshooting so that I was able to find a leak that I previously had not detected.  The torch head itself had a leak that was causing the excessive use of Argon.  Not a lot but enough that it did show over time.  Again thanks
Reply:Originally Posted by pineI want to thank everyone for their inputs.  While none gave me a direct answer to the problem they did help focus my troubleshooting so that I was able to find a leak that I previously had not detected.  The torch head itself had a leak that was causing the excessive use of Argon.  Not a lot but enough that it did show over time.  Again thanks
Reply:Originally Posted by pine  I have "soaped" each connection both when first hooked up and again today and find no leaks.