Quote Originally Posted by rusty00 View Post
It won't rid the tank of fuel, but it will creat an environment where an explosion can't happen by removing the oxygen.
If you have no oxygen then no fire can start.
It is best to remove all fuel any way you can to be sure and to make sure you are happy with the process.
If you have a mig welder and can access the tank crack you will be okay as long as you can squeeze yourself or the welder in place.
We use to use this method to cut tanks in half and weld when fitting gas tanks and also for repairs.
Never ever had a problem.
That means the tank has to be air tight while welding, otherwise oxygen would squeeze in, regardless of the purge.
Why wouldn't oxygen get into the tank from the very crack you're trying to weld??!!