Deep cold air separation technology

What is the reason why the purity of the lower column is the basis for the purity adjustment of the upper column product?

Pressure test before valve installation 1. In the warranty period, those with the certification and the sealing surface is intact can no longer conduct the strength test alone, but only the air tightness test can be taken before installation. 2. Within the warranty period, it has the certificate, and its sealing surface has defects such as corrosion and damage. After treatment, it must carry out the air tightness test. 3. Outside the warranty period, those with certification and intact sealing surface shall be subject to air tightness test before installation. 4. For valves that need to be degreased and disassembled on site, air tightness test shall be conducted separately before installation. 5. The safety valve shall be sent to the local quality inspection department of the project for verification before the end of installation and commissioning.