Lifetime Assessments of an Old Westinghouse-Design Steam Chest

Fossil steam turbines were designed for approximately thirty years of reliable operation based on a normal duty cycle. During operation, highly stressed components of steam turbine power plants undergo a change in material properties due to cyclic stress and exposure to different temperatures. Among all the components of a steam turbine, the steam chest is affected the most as it experiences a wide variation of stresses and loads during transient events and steady-state operation. These factors can strongly influence the metallurgical condition and overall reliable life of steam chests. In this paper, Siemens’ overall approach for lifetime assessments will be discussed with a real life example on a 40 year old Westinghouse-design steam chest. The methodology and the findings from the assessment are also discussed.