Air compressors are required to operate reliably for long periods of time without interruption.
The cryogenic separation process requires a very tight integration of heat exchangers and separation columns to obtain a good efficiency and all the energy for refrigeration is provided by the compression of the air at the inlet of the unit.
To achieve the ultra low distillation temperatures an air separation unit requires a refrigeration cycle, and the cold equipment has to be kept within an insulated enclosure called a "cold box". The cooling of the gases requires a large amount of energy to make this refrigeration cycle work and is delivered by an air compressor. Modern ASUs use expansion turbines for cooling; the output of the expander helps drive the air compressor, for improved efficiency.
When air compressors fail, it can mean significant downtime, significant maintenance costs, unsafe operating conditions, and lost profitability.