Berniep
Platinum Member
For things like gasoline and oils they collect residue in the pores of the metal and this will come out as a flammable vapor when you cut it with a torch. not much of a problem until you get a stoichiometric mix (https://en.wikipedia.org/wiki/Air–fuel_ratio) and then you get a big boom. A good way to avoid this is to use any kind of device to move the air in and out of the tank. like a constant stream of air from a compressor or a running engine exhaust. Although, as already stated, if it is not tuned well a gas engine, and possibly any engine can contribute to the problem rather than help.That is my experience, too. Cursed with a sensitive nose, I really want to eliminate that stink.
For LP or gasoline tanks, as well as 55gal drums, I remove all caps and ventilate with compressor air
after removing liquids. With 2 holes, I can blow in one, and ignite the exhaust from the other, using
a propane torch. If there are flammable gases, you get a flame. Stop the air when the flame dies
out. No woof or explosion. Works like an O-A torch. No water.
Just a few miles from me a guy was killed cutting the end out of a tank open with a torch. The tank was about head high with two sizable caps that had been open for at least 20 years. There was no discern-able odor and he had almost made the complete cut in one end when it blew.