Question about gas cylinders? (and gas too)

admin

Well I have two cylinders that came with the welder I bought. One of them, is a praxair rental tank (not sure what capacity but it's about 4 feet tall), and the other is a 20 lb. CO2 tank. I called both the local Airgas, and the local Praxair to find out how much it would be to fill.I want C25, but maybe you guys could help me decide on a better option, if one exists. (Just for mild steel)Naturally, the Praxair guy told me that I can do absolutely nothing with the rental Praxair tank (not to mention it hasn't been hydrotested, but regardless, I can't use it). The Airgas guy, said that they can fill the CO2 bottle. I asked about filling it with C25 and he said they would have to change the valves, and they would do it for me for around $30. So my question to you guys is: What if I switched the valve from the Praxair tank, to the CO2 tank to save the $30? Can it be done? Should it be done? If this is a stupid question, I do apologize. I will not do anything until I hear a response to avoid acting without information. (Also the Airgas guy told me once filled, the 20 lb. CO2 tank would cost "around $38" to fill. Is this about right? I never asked Praxair)Thank you in advance.
Reply:Well first of all the Praxair rental bottle is not yours. The valve is theirs too. And you should drop it off as soon as it is empty. If Airgas will change the valve for $30, let them do it. They may also do a hydro, I don't know.I like C25 better than Co2, so I think it is worth it. I have not used Co2 for 30 years, so I don't know about cost.Last edited by shovelon; 06-21-2012 at 11:01 AM.Reason: oldWeld 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:I think I'm just going to see if Airgas will exchange the CO2 bottle as is for an Argon bottle.As for the Praxair bottle. I didn't realize I had to return it to Praxair. The Praxair employee told me that it was a rental bottle and they wouldn't fill it for me. I asked "What can I do with it?" and he said "There's nothing you can do with it." So he never informed me of any obligation to return it. I don't really mind returning it, since I have no use for it, except for the trip I would have to make just to go out of my way to return an old bottle that they didn't even express interest in my returning. Maybe I'll just see if they can exchange my CO2 bottle so that I don't have to go to two places. Thanks for your help. I was very skeptical of the "changing valves" idea but I thought I'd ask on the off chance that people do that kind of thing all the time.
Reply:I don't mind C02  so I would just have them refill the 20# tank since you'll end up with about 174CF of gas from it.If you change to c25 you'll only get about 40cf of gas.But as you mentioned you wanted C25 just have them change the valve for the 30 bux.Ed Conleyhttp://www.screamingbroccoli.com/MM252MM211 (Sold)Passport Plus & Spool gunLincoln SP135 Plus- (Gone to a good home)Klutch 120v Plasma cutterSO 2020 benderBeer in the fridge
Reply:Well to be honest, I didn't want to show my lack of experience, but I've never welded with gas. I've been using fluxcore since I got the welder. So I don't know whether straight CO2 or C25 would be better. I've read people sometimes can't tell the difference, and then some people say it doesn't give you good results, but what do I know?But if it's not a big difference, then it does sound a lot more attractive to have 174CF rather than 40CF of gas. Especially since I'm learning and practicing so the more hood time for the price, the better. Thanks for the tip!!Last edited by UMfan92; 06-21-2012 at 11:27 AM.
Reply:Depends greatly on what machine you have and what you intend to weld. CO2 usually gives you the most penetration with small 110v welders, but you tend to get more spatter. This makes it useful to get the most out of what is a limited machine power wise. You won't get a huge increase in power though, but the gas is less expensive.The extra increase in penetration however is a down side if you want to do thin metal body work. There 75/25 is a better choice. You have a bit less penetration and a "cleaner" weld with less spatter.With 230v machines, the difference in penetration with thicker material is less noticeable ( down side with thin metal stays the same), simply because you have more power available. There it usually comes down to what the person already is using and is set up for or price. With larger ( usually 250 amp class and up) machines some run either 100% CO2 or 75/25 with dual shield wire ( special FC wire designed to be run with gas shielding as well). The gas used depends on the wire chosen. This is a bit "beyond" the average hobbyist, but is often why some guys will favor one gas over the other. If you need 100% CO2 to run dual shield, many will simply run 100% when they run solid wire from a logistics standpoint. Less cost and they only need to keep one gas on hand etc.Note that to run 100% CO2 with "stock" regs that come with most small migs, you need an adapter. Make sure you keep the adapter with the reg and not with the cylinder when you exchange it! I'd guess you probably already have the adapter if you got the cylinder of CO2 with the machine and some one else was using it. If not, you'll have to get the adapter before you can run CO2 or get a dedicated CO2 reg..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:Thank you DSW! That really helps a lot. I was wondering the difference between C25 and full CO2 in terms of results and your answer cleared that up. Well I primarily got this welder for auto body work, but since I don't plan on doing anything just yet, I think I'll go with CO2 to get more value for practice. Besides, I am creating a bunch of household projects for fun. I'll be making a work-table soon, (I know it's so typical of a beginner to make a table!) so the extra penetration will come in handy. When I decide to tear out the cowl on my old Mustang, I'll get some C25.
Reply:you'll also need a Nylon washer to go in between the adapter and the Tank.Last edited by Broccoli1; 06-21-2012 at 12:29 PM.Ed Conleyhttp://www.screamingbroccoli.com/MM252MM211 (Sold)Passport Plus & Spool gunLincoln SP135 Plus- (Gone to a good home)Klutch 120v Plasma cutterSO 2020 benderBeer in the fridge
Reply:Well I just got my CO2 tank swapped for another 20lb. tank. The guy at Airgas was confused and kept telling me that I should use "an Argon mix" and he's never heard of welding with just CO2. He was just trying to help and he was nice.Now I just need an adapter. Surprisingly, the person who sold me the welder, did not have an adapter. Weirdly enough, they were using the Praxair tank with God knows what gas inside. It's weird because the last hydro test on that tank was in 1999. It still had 80 PSI of something when I drained it. Where can I get one of those adapters? I looked at Airgas and asked the guy and he said they didn't have anything like that. Do I just go to the plumbing area of Home Depot and find the right adapter? What are the thread sizes of CO2 and Argon bottles? A google search revealed very little.
Reply:You got the Good Airgas I see http://www.airgas.com/browse/product...ct=RAD64003956orhttp://www.ebay.com/itm/Western-Styl...ht_1905wt_1141they even provide a description of the difference when using CO2Ed Conleyhttp://www.screamingbroccoli.com/MM252MM211 (Sold)Passport Plus & Spool gunLincoln SP135 Plus- (Gone to a good home)Klutch 120v Plasma cutterSO 2020 benderBeer in the fridge
Reply:Think there's some "bad information" being put out in this thread.You don't just "change the valve" on a cylinder certified for CO2 to make it a C25 cylinder.CO2 cylinders are hydroed to a different standard than high pressure cylinders.Just been thru all this with ARCET on two different cylinders.  Here's what I found.Had an owner 330 (no name on neck ring) that I wanted to convert to a 50# CO2 cylinder.  I use the 50# CO2 on my gas mixer.  ARCET would not install a CO2 valve in the cylinder (even though the high pressure cert was current) without rehydroing the cylinder for CO2.  Cost me $30 for the hydro and valve exchange (I provided the new valve).Then I went thru the same ordeal with a 125 high pressure cylinder that I own.  Rehydro and install new CO2 valve.  This is a cylinder I use only for backup to the 50# primary cylinder on my mixer.  Had to be rehydroed even though the high pressure certification was still current (cylinder was only 2 years old).Now for the catcher.Happened across a deal on several 20# CO2 cylinders, so decided it may be smart to convert my 125 back to a C25 cylinder (used for portable work).  I'm now told that they will have to re-hydro my cylinder for high pressure use and the hydro and valve change (back to the nearly new 580 valve) will cost me $30 (again) even though the original high pressure certification is still good for nearly 8 more years.Bottom line, is that you don't just change valves and call it good.PS.  As a side note.  When I returned the 50# leased cylinder that I had previously used on the mixer, I let the ARCET guy know that the cylinder still had about 20# of CO2 in it.  Thought it may save them some gas when refilling.  He immediately took the cylinder and opened the valve to bleed off the CO2.  Said every cylinder they fill has to be empty and purged prior to refilling.  Only way they can verify what's actually in the cylinder.  Made me feel a little better about the gas I'm getting from them.I then swapped out that leased 50#CO2 cylinder for a full 330 of argon.Syncro 250 DX Dynasty 200 DXMM 251 w/30A SG XMT 304 w/714 Feeder & Optima PulserHH187Dialarc 250 AC/DCHypertherm PM 1250Smith, Harris, Victor O/ASmith and Thermco Gas MixersAccess to a full fab shop with CNC Plasma, Water Jet, etc.
Reply:Yeah sorry about that SundownIII. It was a dumb idea to swap the valves but I figured I'd ask. I know now not to do that and I'm sure the different valves have different pressure specs. The thread kinda drifted onto which gas I should get and what I should do instead of changing the valves.Thanks for the warning anyway. I know you just wanted to steer me in the right direction.
Reply:Last time I looked at Tractor Supply they stocked the adapter to use an inert gas reg on a CO2 cylinder.Not a huge surprise the guy behind the counter had no clue. My guy is fairly good and I still find things he's unfamiliar with..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:After he told me he had never heard of straight CO2, he did admit to me that he was not a welder, which explains why he hadn't heard of it. Oh and I decided I'm just going to buy a new regulator. My regulator is old and I don't want it to spring a leak, and I'm not sure if it's accurate. I'm going to buy a regulator that comes with both fittings.
Reply:UMfan,Just know I wouldn't steer a fellow "Hurricane follower wrong".Did my graduate work there (MS in Industrial Engineering), finishing in 1975.  Followed the Canes closely since then.As a new guy just learning mig, I personally feel your best choice of gas is C25.  That's all I ever run on my small mig.  All gas mixes are a compromise in one shape, form or fashion, but C25 (75%Argon, 25%CO2) will give the best all around results with minimal spatter.PS.  Think Al Golden will soon establish another Hurricane Dynasty.  Probably not this year, but think he'll accomplish what Howard S. would have done had he stayed around.Syncro 250 DX Dynasty 200 DXMM 251 w/30A SG XMT 304 w/714 Feeder & Optima PulserHH187Dialarc 250 AC/DCHypertherm PM 1250Smith, Harris, Victor O/ASmith and Thermco Gas MixersAccess to a full fab shop with CNC Plasma, Water Jet, etc.
Reply:SundownIII, Awesome! Another Hurricane on the forum! I just finished my sophomore year, heading into my junior year at UM, majoring in Mechanical Engineering. And my Dad graduated with his BS in Mechanical Engineering in 1989 (when our football team was making history, he went to the games!)Thanks for the tips on the gas. I already got some CO2 since it's cheaper and I'll learn with that for now (college budget!). But I'll definitely be trying C25 eventually. And yeah All Golden is definitely turning things around. It would be awesome to win a championship while I'm there. Go 'Canes!Last edited by UMfan92; 06-21-2012 at 06:23 PM.
Reply:Around here Prax only leases 330cf cylinders. I know it is different everywhere, but I can't imagine your 4' Praxair bottle to be a lease bottle. Why do you think it is?
Reply:Originally Posted by SundownIIIThink there's some "bad information" being put out in this thread.You don't just "change the valve" on a cylinder certified for CO2 to make it a C25 cylinder.CO2 cylinders are hydroed to a different standard than high pressure cylinders.Just been thru all this with ARCET on two different cylinders.  Here's what I found.Had an owner 330 (no name on neck ring) that I wanted to convert to a 50# CO2 cylinder.  I use the 50# CO2 on my gas mixer.  ARCET would not install a CO2 valve in the cylinder (even though the high pressure cert was current) without rehydroing the cylinder for CO2.  Cost me $30 for the hydro and valve exchange (I provided the new valve).Then I went thru the same ordeal with a 125 high pressure cylinder that I own.  Rehydro and install new CO2 valve.  This is a cylinder I use only for backup to the 50# primary cylinder on my mixer.  Had to be rehydroed even though the high pressure certification was still current (cylinder was only 2 years old).Now for the catcher.Happened across a deal on several 20# CO2 cylinders, so decided it may be smart to convert my 125 back to a C25 cylinder (used for portable work).  I'm now told that they will have to re-hydro my cylinder for high pressure use and the hydro and valve change (back to the nearly new 580 valve) will cost me $30 (again) even though the original high pressure certification is still good for nearly 8 more years.Bottom line, is that you don't just change valves and call it good.PS.  As a side note.  When I returned the 50# leased cylinder that I had previously used on the mixer, I let the ARCET guy know that the cylinder still had about 20# of CO2 in it.  Thought it may save them some gas when refilling.  He immediately took the cylinder and opened the valve to bleed off the CO2.  Said every cylinder they fill has to be empty and purged prior to refilling.  Only way they can verify what's actually in the cylinder.  Made me feel a little better about the gas I'm getting from them.I then swapped out that leased 50#CO2 cylinder for a full 330 of argon.
Reply:Originally Posted by Fred sI dont get all of that.  seems like a 2640 rated cylinder should be fine for the ~800 psi of CO2
Reply:Originally Posted by SundownIIIThink there's some "bad information" being put out in this thread.You don't just "change the valve" on a cylinder certified for CO2 to make it a C25 cylinder.CO2 cylinders are hydroed to a different standard than high pressure cylinders.
Reply:Fred,Didn't make sense to me either.  Just telling you what my LWS required.I also agree that my 330 which was current for high pressure inert gas should/could be filled with CO2 with no problem, but they required that it be recertified (hydroed) for CO2.  The current stamping on the bottle (for CO2) are different from the high pressure stamps.Same thing for my 125 (bottle is only 2 years old and had a + stamp for high pressure).  Recert for CO2.  Now they say they've got to rehydro to convert it back to a high pressure cylinder.Since this is my "only realistic" gas supplier, I'm kinda at their mercy.  Don't think they're just "jerking me around" though since they give me a good rate (high commercial) on my gasses.Syncro 250 DX Dynasty 200 DXMM 251 w/30A SG XMT 304 w/714 Feeder & Optima PulserHH187Dialarc 250 AC/DCHypertherm PM 1250Smith, Harris, Victor O/ASmith and Thermco Gas MixersAccess to a full fab shop with CNC Plasma, Water Jet, etc.
Reply:I wouldnt think they are jacking you up too much.  I work for a good sized gas company and I get involved a bit with the cylinder testing side.  I am not aware of any national standard that would require a "CO2" hydro if the current "HP" hydro is OK.It may very well be a damn good idea to have a policy that no matter what, a change of service means you will hydro, etc. etcPer CGA C10-4, (which is a "Reccomended Procedure"), you should always do a visual.  Depending on what the various inspections show, you then have some cleaning procedures, etc.I know that there are a bunch of pressure ratings, and you have to pay attention to what cylinders get filled to what pressures.  rlit's example of a CO2 bottle possibly not being suitable for full pressure 75/25 coming to mind immediately.Experience is something you get right after you need it
Reply:Local supplier policy varies greatly. If I end up with an inert gas cylinder which fails hydro or which I can't exchange, it meets the cutting torch. The top becomes a yard gong and the bottom becomes a handy place to drop hot metal when torch cutting. They'd make a good crucible but I'm too lazy to build a furnace. The mid-section is an nice hunk of pipe for whatever you want to use it for.I donated one long top cutoff to a bud who will use it for a bowling ball mortar. If (a supplier) doesn't care about a cylinder, I might keep it until I found someone with a (matching) account and sell or swap it to them. Saves them $$ on a lease. I don't lease. Thirty bucks for a cylinder conversion is plenty reasonable.
Reply:I agree that $30 for a "cylinder conversion" is pretty reasonable (even when I provided the new valves).I did get a "warm and fuzzy" when they took my 50# cylinder back and immediately opened the valve to bleed off the remaining CO2 (even though the cylinder still had about 20# in it).  Said ALL cylinders are drained and purged prior to refilling.With all this discussion about "bad gas", I'm happy to report that I've NEVER encountered that problem.  Maybe it's because my LWS is overly cautious and careful about what gas goes into the bottles.Syncro 250 DX Dynasty 200 DXMM 251 w/30A SG XMT 304 w/714 Feeder & Optima PulserHH187Dialarc 250 AC/DCHypertherm PM 1250Smith, Harris, Victor O/ASmith and Thermco Gas MixersAccess to a full fab shop with CNC Plasma, Water Jet, etc.
Reply:I keep 20# CO2 tanks on my truck because they are easy to lug around and cheap to fill ( I pay 12 bucks). I never worry about the date because my LWS just swaps em out for me.Disclaimer; "I am just an a$$hole welder, don't take it personally ."Well I got my welder all set up. I bought a new regulator that comes with fittings for both argon and CO2 and set it up. Then I proceeded to check for leaks. I used a bunch of that white thread seal tape to make sure nothing had leaks. I just need one more thing: WIRE! All I have is flux cored so I gotta go pick some up at Home Depot tomorrow. Any recommendations? I don't want to spend a ton but I don't want Harbor Freight wire so I was gonna go with Lincoln SuperArc. Any good?
Reply:Also, my welder has a really long hose from the cylinder to the gun, and I want to shorten it. I have to coil it  and leave it around the cylinder like a garden hose. Only thing is, I don't know how the fitting works and I don't want to screw anything up. Is there any reason to have a hose this long? Anything that would make it dumb for me to shorten it? It's like 4 feet out of the back of the welder.
Reply:hose length is fine just coil it up and ditch that damn white seal tape to seal on the fittings it seals on brass on brass contact and the co2 seals with the washer seal between the valve and the regulatorLast edited by WeldorWes; 06-23-2012 at 06:55 AM.Miller Xmt 350Lincoln Ln-25Ahp 200xSmith Gas Mixer AR/HTig is my Kung FuThrowing down dimes and weaving aboutInstagram http://instagram.com/[email protected]
Reply:Ok I'll keep the hose the length it is now. But why ditch the white tape? I thought it was good for sealing the threads. When I installed everything without the tape, it had some small leaks. Perhaps I just didn't tighten the fittings enough, but I didn't want to over-torque them.
Reply:Originally Posted by UMfan92Well I got my welder all set up. I bought a new regulator that comes with fittings for both argon and CO2 and set it up. Then I proceeded to check for leaks. I used a bunch of that white thread seal tape to make sure nothing had leaks. I just need one more thing: WIRE! All I have is flux cored so I gotta go pick some up at Home Depot tomorrow. Any recommendations? I don't want to spend a ton but I don't want Harbor Freight wire so I was gonna go with Lincoln SuperArc. Any good?
Reply:Originally Posted by Broccoli1Where di you get the Regulator?
Reply:I figgered you did so why didn't you buy the HF Wire?It is not bad,Ed Conleyhttp://www.screamingbroccoli.com/MM252MM211 (Sold)Passport Plus & Spool gunLincoln SP135 Plus- (Gone to a good home)Klutch 120v Plasma cutterSO 2020 benderBeer in the fridge
Reply:Lol Well I just assumed that the regulator just has to deliver gas so it shouldn't be a big deal, but the wire has to be good quality with certain additives and the proper alloy, and the Lincoln wire that I got (superarc L-56) is copper coated to protect the tip. So what about the gas flow? What should I set it at?
Reply:Gas flow is some what dependent on what you are doing. Code work would list the settings you would use, but that probably doesn't apply here. Usually you can keep turning it down until you see signs you are getting poor gas coverage (porosity), then turn it back up a  bit. If the work is critical, "wasting " a bit of extra gas to be safe is cheaper than having to grind out a weld because of porosity especially in tight awkward locations.  How far you hold the gun from the work would also change how much gas you run. If you stay in nice and tight, you can get away with less gas than if you are holding back 3/4"-1" from the material. Joint design would also play a part. Inside corners in a box would probably need less gas than outside corners out in the open. Breezes or drafts would also cause you to want to increase gas flow. 15-20 CHF is an "average" number, but I'll go higher if I have to weld outside and there's even the hint of a light breeze..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan