I think you may not need to worry about purging all of the other gases from a container. If you purge a lot of the O2 then you will have some effect, and anything that uses the O2 will use up the little that you have left rather quickly.

Of the gases in air, I think, nitrogen is one of the lighter ones, so you may want to add the N2 to an atmosphere when the N2 is warm. Liquid N2 might not do what you want it to do.

Nitrogen is more than 70% of the air, and oxygen makes up about 21% of air, followed by argon, CO2, neon, helium, methane, krypton, nitrogen oxide N2O, and hydrogen. I am pretty sure all but the hyrodgen and helium are heavier than nitrogen.

If you were trying to change the atmosphere in a tank with air in the atmosphere, you would push nitrogen into the top of the environment, and let gas escape from the bottom. Using an 02 sensor, you should be able to tell when the N2 had evacuated the O2 and thus all the air.

I think if you are going to seal things at that point, you want to do it quick, so the glue or caulk may not be a good idea.


EDIT:

I was looking for information on how LNG or similar ships change atmospheres, but could not find any. Generally, they push lighter gases into the tops of tanks and heavier into the bottom and the do so slowly. If you do it too quickly, the gases will mix, and diluting an atmosphere takes longer than just a change. Also, beware of pushing warmer gases into the bottom or colder into the top of anything, and the temperature difference leads to mixing or maybe the gases flipping. Been a while since I looked at the loaidng manual for any ship like this.