Abstract
During cool-down operation of a helium liquefier, turbo-expanders are most susceptible to mechanical damage resulting from the extreme operating conditions. Growth and distribution of internal turbine losses were therefore calculated based on inlet temperature transitions. These were predicted by assuming a steady state in the liquefier. Predicted turbine performance was compared with actual measured data. A simplified prediction method is proposed for customers to correlate measured turbine performance on the manufacturer's test stand with their liquefiers that have different cool-down characteristics.
