Failure modes, effects and criticality analysis of a 3kW@4.5K helium refrigerator

The comprehensive research facility for key systems of fusion reactors was included in the “13th Five-Year Plan” priority project in China. In order to meet the requirements of cryogenic testing of large superconducting magnets, it is proposed to build a 3kW@4.5K refrigerator and carry out research on 3kW@4.5K superfluid helium cryogenic system. In order to evaluate the reliability of the 3kW refrigerator, the FMECA analysis was performed on the helium refrigerator. The refrigerator system is divided into three subsystems: the compressor system, the monitoring and control system and the cold box, to identify the failure mode and the impact on the refrigerator system related functions. The critical value is calculated and the critical matrix is drawn by the severity and the occurrence of the rating criteria. Identify the parts with high and medium risks and propose corresponding risk mitigation measures.