bottle sizing and run time

[new welder guy]

how do you know what size bottle is right for you.also about how long will the diff sizes of bottles last like a 20cf 80cf 120cf and so on im taking like c25 or stargon mixs thanks

[Bob the Welder]

Divide your size of bottle by flow rate per hour. For example, 80 cu. ft. bottle divided by 20 cu. ft. per hour flow rate will give about 4 hrs. weld time.

[Dmaxer1]

Be sure to look at the cost per hour for welding with the different sized cylinders. I.e., the bigger the bottle, the lower the cost per cu.ft. of of gas so the (much) lower the cost per hour. I use a "K" size cylinder for Ar and C-25, about 250 cu.ft., and find it is much cheaper over time compared to a cylinder half the size. The huge cylinders (330 cu.ft.) are cheaper still, but the 250's are all I can handle alone with confidence. The general rule is, the bigger, the cheaper. You just have to be able to deal with the logistics.:D

[new welder guy]

the bottle was bought for me for xmas so when i take it in to refill ill see if i can get them to let me pay for a upgrade to a bigger tanks altho the 80cf tank looks pertty dam big

[MichaelP]

My LFS upgrades cylinders at no additional cost.

Keep in mind that as soon as you bring your own cylinder for the first refill, they exchange it for one of their tanks (one that is marked so). Only very rarely stores have a capacity to refill your own cylinder on-site: they ship them out. Therefore, when you come, they simply substitute your empty cylinder with a filled one. This "marries" you to the store since almost no other store will be willing to accept another store's property. Even if you show them a proof of ownership of the initial bottle, thay may refuse dealing with you.

Now, since you're "married" to the first LFS, they only gain if you ask them for an updrade. They sell gas, and more gas costs more. So, they really shouldn't charge you for the upgrade. That is unless you have jerks at your LFS. But in this case, I wouldn't suggest you to marry this LFS: the marriage won't be pleasant, and the divorce will be very painful.

P.S. In any case, request a written proof of the initial exchange. Something that would show that you brought your own cylinder. Naturally, absence of tank lease payments is an indication of your ownership by itself, but having a paper wouldn't hurt, especially if you need to present it somewhere else.

[new welder guy]

i dont think i have any of the paper work or anything to the tank it was gave to me for xmas as a gift they said that i own the bottle tho i guess

[MichaelP]

When you bring your cylinder for the first refill, ask the store to provide you with a receipt that shows that you brought your own cylinder and exchanged it for a store's one.