Just upgraded to a 250 CFT argon tank.

[breakneckmot]

I'm just getting into TIG, I bought my current machine from a friend this weekend. He loaned me the Argon cylinder he was using with it. I need to go get it filled and I'm trying to decide if I should just fill it (80 CF) and use it, or if I should rent/buy a second one for myself. I like the idea of a backup cylinder since my LWS shops (Airgas/praxair) are both only open on weekdays during the hours I work my 8-5 job. I really don't know how much argon I'll be using, I have been using my fluxcore about 3-4 nights a week and have gone through about 8lbs. of wire in about 2 months.

[joshuab]

I really don't know how much argon I'll be using, I have been using my fluxcore about 3-4 nights a week and have gone through about 8lbs. of wire in about 2 months.

Typical TIG flow rate is about 15 cfh. 80 cf / 15 cfh is about 5 hours. Post-flow will affect the accuracy of that number. If you're tacking up a lot, you'll have 1-2 seconds of arc followed by 5-10 seconds of post-flow, whereas when you're welding you might have 20-60 seconds of arc. So the post-flow "overage" varies, but dividing the tank size by 15 will at least give you some basis for comparison.

[breakneckmot]

Typical TIG flow rate is about 15 cfh. 80 cf / 15 cfh is about 5 hours. Post-flow will affect the accuracy of that number. If you're tacking up a lot, you'll have 1-2 seconds of arc followed by 5-10 seconds of post-flow, whereas when you're welding you might have 20-60 seconds of arc. So the post-flow "overage" varies, but dividing the tank size by 15 will at least give you some basis for comparison.

Good info, thanks! I really need to get my current bottle swapped/filled and just use it. I really don't know how much arc time I'll be spending a night and the only way to tell will be to start playing I guess.