803056,
"It is interesting to note how few welders are aware of the issue of withdraw rates for acetylene from a given tank size. "
In response to this. It is not only the welders, but Foremen, shop managers and their purchasing agents are also to blame for this potentialy serious safety issue.
The backfiring of rosebuds can melt a torch mixing barrel. Fortunately most places install check valves these days, so it's been quite a while since I've seen the hoses blow up (which is something that definately gets the blood flowing).
I was in a shop a couple of years back and they had just purchased 6 brand new rosebuds. I don't recall what size they were, but were of such large of orifi that the smoke would not even begin to clear when opened all the way. Not a single person could use them with out backfiring.
Since I mentioned in my previous post about cupric acetylide, though I ought to elaborate a bit. It is a very unstable and shock sensitive explosive compound that is made by the passing of actylene through copper (under certain conditions)...rare, yes but it can happen. I was touring XXXXXX solid rocket motor plant and test site and shown some impressive holes in the ground where some of these type compounds in test-tube quantities got away from them. NASA and the military have all the FUN TOYS!
http://www2.itap.purdue.edu/MSDS/detail.cfm?MSDSID=7218Moral of the story is...If buying your own supplies, get the small rosebud! Yes, you might think it takes longer, maybe it does, but so does relighting a torch that's always popping out. Charge by the hour!
Anyway, I've found propane weed burners to be far cheaper and efficient for most preheat applications.