Is there some place where I can get an idea of how much welding gases cost.
For example, I think that I will go to refill
1) a 397 CF, or maybe alternatively a 145 CF, acetylene bottle 2) A 240 CF oxygen bottle 3) A 25/75 MIG gas bottle
The bummer is that the guy wants $39.99 for hydro, but I think that he has me by the balls, so I cannot argue too much.
Also, what would be a ratio of oxygen to acetylene, ergo, which acetylene bottle (397 or 145) would better fit the 240 CF oxygen bottle.
The fill costs are really a mix of fixed and variable costs. The net is that filling a bottle that is twice as big is usually only ~50% more money.
Your oxy acetylene bottle mix depends a lot on what you do with it: -small welding/brazing jobs: get the 132/145 cubic foot tanks for each, they run for a long time -Cutting takes a LOT of O2, 145 acetylene, 240 (or bigger) O2 -Heating with a rosebud takes a LOT of acetylene, you will over load the small 145 acetylene tank very quickly, this is the only reason to deal with the 397 CF acetylene tank. It is HEAVY, nasty to transport.
Sounds like you are getting hit with a hidden transfer fee on the tanks. But $40 per tank to get full tank swap privileges is not horrible. But make sure that the dealer will let you bring in a tank, walk out with a full one on the spot. My neighbor had to drop off HIS tank, wait two days to get HIS tank refilled. That is a disaster when in the middle of a project.
Yes, the 397 tank is nasty, I can barely get it into and out of my truck alone. But it is big and will alow for fewer trips, and cheaper refill costs.
So, I think that I will take my 75/25, Oxygen and 397 CF acetylene tanks with me and will leave the small 145 CF tank home for now, maybe I will sell the 145 tank. As you can tell, I have no experience and no good idea as to what I will be doing with them.
Well every time I negotiate a " good " price the next time I go in the computer has automatically spit out the highest possible price. even if the attendant says it is locked in. Actually the gas takes a good of electricity to create, even oxy acetylene welding is kind of electric welding the way I see it.
22 cents a cubic foot was the best I have got acetylene for but that was a few years ago and I was getting the big one you speak of 397, acetylene should be sold by how much they actually put into the tank unlike the compressed gasses which should all have the same contents for the same size. Just guessing 40 cents a cubic foot or look elsewhere.
I thought it was 220 for the standard oxygen size, I used to be able to get the 336 for $25 but that is using a bunch of them a year I am sure they would charge me at least $40 for a 220 now after all the merging. I can choose between Airco and abco. abco bought out a local privateer who I liked and they won't quote me prices on the phone unless I go down and explain my whole operation. I will keep those tanks until empty and expect to loose the deposit I put on them with the local independent they bought out. At least the guys at airco are the ones I have dealt with before and know quite well. If you buy some big ticket items down there it helps all around as far as pricing goes. then there is the hazardous material fee which is around $7.50 even for inert gas.
It is not unlike selling scrap steel if I call the local place and have at least a ton and know it's grade and get a quote it is almost twice of what I get if I get just what the computer spits out.
Carbon dioxide is the cheap gas I got 50 pounds for $25 which is like a 220 size tank. Of course they get me on the lease also and the haz mat.
As for the ratio, oxy acetylene welding is about one to one. For flame cutting it really depends on the size of the cutting orifice, a 40 cubic foot tank and a standard 220 oxygen seem to go down about together with a #60 or half inch steel tip. Propane or natural gas uses more oxygen and might not really be economic unless you get liquid oxygen and run a scrap yard. But it will work until the oxygen is gone then I can exchange both of them.
Of course if you get the biggest tanks and forget to turn them off for a few days or weeks it could get more expensive than if you had smaller ones.
The correct method of choosing the size of an acetylene cylinder is by the FLOW RATE, not by the stoichiometric combustion ratio.
When you draw acetylene from a cylinder the acetone inside the cylinder is "fizzing" like soda when you shake it. The acetone can only "fizz" out so fast.
The maximum flow rate (draw rate) from an acetylene cylinder is 1/7 (some say 1/10) of the total, filled, gas volume per hour. ie, if you have a 145 ft^3 cylinder the MAXIMUM flow rate at any time (full to empty) is 145/7 = 21 ft^3 per hour (CFH). This is reduced by low temperatures and vice-versa. However heating an acetylene cylinder is not recommended to increase flow rate! =:o
If you try to draw at a higher rate you will pull acetone out of the cylinder. This is bad for several reasons. One reason is it can clog your regulator allowing the acetylene pressure to creep past the regulator setting, possibly causing an explosion.
You match the cylinder size to the gas flow required by the largest tip you plan to use.
There is nothing wrong with using a large acetylene cylinder with a small oxygen cylinder. The oxygen cylinder will just empty faster, especially if you are cutting.
According to this chart: http://www.harrisproductsgroup.com/techdata/TipFlow.asp You can exceed the maximum flow rate of a 145 ft^3 cylinder with a #7 tip on 1/4-inch steel.
There are some heating tips that require such a high flow rate that four 397 ft^3 acetylene cylinders must be connected together with a manifold to supply the correct flow.