Root cause analysis of early performance deterioration of an existing helium liquefier using process simulation.

A two-stage investigation was performed to identify the causes of failure in steady state operation as well as of no production of liquid in the helium liquefier in Cryogenic Engineering Centre, IIT Kharagpur, India. The liquefier was a 17 L/hr, liquid nitrogen pre-cooled Claude cycle. During early days, the liquefier produced at rated capacity; however, with time its performance deteriorated and later it never produced any liquid. In the investigation, log-sheets of the operation of the plant, process configuration as supplied, and equipment specifications as obtained by direct measurements and by estimation using dynamic simulation together with
the experiences of operators and scientific staffs were considered. The outcomes of first-stage investigation are presented in the paper. It was found that regular power failures, malfunctioning of chilling unit and turbine control system were a few major causes. Recommendations are proposed based on the findings for future operation of such plants.

本研究针对印度印度理工学院卡拉格普尔分校低温工程中心（Cryogenic Engineering Centre, IIT Kharagpur）的氦液化装置（helium liquefier），开展两阶段调查，以探明其稳态运行故障及无法产出液态氦的成因。该液化装置为额定产能17升/小时的液氮预冷式克劳德循环（Claude cycle）氦液化器。该装置初期可按额定产能稳定产出液氦，但随着运行时长增加，其性能逐渐劣化，最终完全无法产出液态氦。本次调查综合考量了装置运行日志、原厂提供的工艺流程配置、通过直接测量及动态仿真（dynamic simulation）估算得到的设备参数，以及操作人员与科研人员的实操经验。本文呈现了第一阶段调查的结果，研究发现经常性停电、制冷机组故障及涡轮控制系统失灵是导致装置故障的几类主要诱因。本研究基于上述调查结果，针对此类装置的后续运维提出了优化建议。