The whole set of 35 000 m3/h air separation equipment of Masteel Gas Company is imported from abroad.Due to the original design factors of expansion machine,process liquid oxygen pump and crude argon circulation pump,the re-frigeration capacity of rectification system is insufficient,and the process liquid oxygen pump and crude argon circulation pump cannot automatically adjust the load.Through the localization technical transformation of expansion machine,process liquid oxygen pump and crude argon circulating pump,the refrigeration capacity of rectification system was increased,so that the outlet pressure of process liquid oxygen pump and crude argon circulating pump could be automatically adjusted.This paper describes the problems in operation of the expansion machine,process liquid oxygen pump and the crude argon circulating pump and the specific methods of technical transformation.