Large-scale systems such as plants should be operated with high reliability and availability because the downtime due to system failure has a significant influence on the manufacturing activity. Nowadays the emerging ICTs (Information Communication Technologies) and sensor technologies make it possible to monitor health status of important equipment of the plant and do diagnosis and prognosis for further suitable maintenance actions in real time, which leads to much concern on PHM (Prognostics and Health Management) or CBM (Condition-Based Maintenance). In this study, we briefly look through the concept of PHM and introduce prognostics case studies for plant equipment.