BS,
I'm not sure about the Smith/Victor/Harris differences, but I will take a shot at the tanks...
As for the O2 tank, change it out whenever the regulator pressure goes below what you need for your cutting-stream jet or to get a neutral flame when welding. You will know when this happens because the torch will simply begin cutting poorly (usually for me, this is about the time that I have been back from lunch for an hour or two and still have 6-8 hours left in the day and I'm 20 miles outside of town) or you have to keep adjusting the valves on the mixing chamber to get a good inner-cone. Once you have been using them for a while, you'll be able to judge when it is about to get low, and due to the physics of a pressurized tank, you would have to have one certain special set of circumstances to actually have the O2 tank "suck" air back in (this case would be such that the tank is danged near completely emptied when fairly warm outside, the main valve is closed and check valves are removed, and the tank is reopened later when it is cooler), so just run it until exhaustion or until you don't think you can go another round before it drops below the pressure you need.
The little gas-grill propane tanks and a 125 cu. ft. acetylene tank will both last the same amount of time as two 250 cu.ft. O2 tanks if you do mostly torching, but, if my logic is not flawed, welding will prolly bring it closer to 1 to 1, maybe less. If you are using propane as a fuel, just run the thing dry or until you have no more fire, then refill it or have it refilled. Acetylene is basically the same way, but I will warn you about running it low while in warm climates-I actually had a tank that worked fine until it got down to single digit PSI's (again, 20 miles outside of town and trying to stretch a buck), at which point my torch began backfiring fairly often. I couldn't figure out what was going on until I began to notice the frequency of small grass fires had increased when the sputtering began. Turns out that the tank either heated up enough to expand the acetone inside so that it began overflowing out of the main valve or the tank had been overfilled with acetone in the first place, and every so often, a short stream of flames would spit out of the tip, landing on the grass and making a pretty neat looking fire-line.
Either way, whether you go propane or acetylene, make sure they are stood up so that (a) you get propane gas instead of liquid propane or (b) you get actetylene instead of acetone out of the tip.
Good luck,
G. L.
Mrbillz
There is a difference in where the mix takes place- in the event of a flashback combustion can only take place where fuel and oxygen are combined. I guess it's possible for excess oxygen pressure to cause O2 to travel deep into a fuel hose, but o a day-to-day level you will notice your mixing handle get quite hot in the event of combustion traveling back to the source of the mixed gasses; the other arrangement however keeps that heat away from the brazed joints, seals, and such they used to build the torch, and hopefully keeps it in the torch tip, which has been engineered to dissipate heat. This should also serve to keep the innards clean and soot free- soot free innards posing less hazard for flashback.
Regards
d
Tip mix, base mix (as you call it) really doesn't make all that much difference.
From my experience, most torch designs work well. If they did not, the manufacturer would not be in business.
Remember- we are looking at a gas torch. Really nothing more than a pipe with a couple of valves.
While my money will always go to Victor, Harris, Airco-Concoa, there are some very good copies made.
If I were to buy an aftermarket, I would lean to Generico, or GenTec as they are known now. Rugged equipment, the price is right.
Hope this helps..
brande
