... 0.7MPa (Gauge); upon being cooled in the after-cooler, it enters the pre-cooling unit where it is ... part of the expanded air thru expanding in the sub-cooler, is cooled by the oxygen in the LP ... level of the LP column, and thru expansion air sub-cooler and main heat exchanger reheating, it is then ... the LP column, and after being reheated in the sub-cooler and main heat exchanger, it is then delivered ...