we actually just recently went over this in school, iirc the options were empty a full CO2 fire extinguisher into the tank, purge it with water, or purge it with steam for a few hours.
The purging with water seems like the most logical and time-effective method, imo.
Like BlkCurrantKord said, it's the vapors you're worried about, so just make sure the vapors get flushed out.
edit: I just checked 2 books I have on me, the general book says "Before welding any fuel tank, thoroughly purge it of all explosive fumes by steam cleaning, or some other means to remove all of the danger. To steam a fuel tank, pass live steam through it from the bottom and let it flow out the top. Continue steaming for at least an hour." But then says " For Integral fuel tanks, drain and purge it with either argon or CO2 until a vapor detector shows that the tank is free of explosive vapors and safe to repair. Both of these gases are heavier than air and will remain in the tank during the repair."
Then, the other book which is an advisory circular says "Purge de-fueled tanks of explosive fuel/air mixtures in accordance with the manufacturer's service instructions. In the absence of such instructions, utilize an inert gas such as CO2 as a purgative to assure the total deletion of fuel/air mixtures."
I've never done this, though, so Idk which method to recommend. But I hope this was helpful.
lmaooo sorry i had too
