The sealing plate and pure nitrogen outlet cap at the upper end of the upper step, the crude argon outlet cap of the crude argon tower condenser must be removed at ground level, the lifting of the lower tower which has been compounded with the condenser with random lifting lugs, the assembly of the upper tower with the main condenser, the heat exchanger, the dirty nitrogen liquefier, the oxygen liquefier only, the installation of other vessels in the cold box.