What is the principle of action of the DEAR Liquid air separation unit (section-2 or section-3 valve) and how does it work?

1.The purpose of purging is to purge the welding slag and dirt left in the pipeline and container. 2.The principle of purging is doing the outside columnfirstly,and the inside column after. The purging should be carried out one pipeline by one. 3.When purging the system, the filter core on the equipment inlet pipe should be removed. 4.When purging the pipe outside the cold box, all the valves connected with the cold box should be disconnected to prevent dirt from entering the valve and column. 5.The purging of each system should be repeated for many times. The purging time shall not be less than 4 hours. 6.To check whether the purging is complete, wet white filter paper or white cloth shouldbe used to placeat the outlet of purging. After 5 minutes, it is qualified if it is clean and free of obvious mechanical impurities.

How can one determine whether the molecular sieve heating and regeneration process in an air separation unit is thorough?