Generally, there are three types of expanders, namely, low-pressure expander, medium pressure expander and liquid expander. For a certain type of gas expander, the greater the volume flow of working medium, the higher the efficiency. Generally, the efficiency of the low-pressure expander with a flow of more than 8000nm is 85 ∽ 88%, and the efficiency of the expander with a flow of less than 3000 ∽ 8000nm will be as low as 70 ∽ 80%.

The production scale of China's air separation equipment has changed from the early stage, which can only produce 20m3 / h (oxygen) oxygen generator. It has developed to the capacity of producing 20000 m3 / h, 30000 m3 / h, 50000 m3 / h and 60000m3 / h large-scale air separation equipment, and has completed the scientific research stage and is about to manufacture 80000m3 / h ultra large-scale air separation equipment.