Summary
Turbine-generator owners are being asked to run aging rotors harder, with more cycling and longer intervals between outages, while the components most likely to limit life sit where they are hardest to see: rotor bores and near-bore forging material, shrunk-on disk keyways prone to stress corrosion cracking, blade attachment dovetails, generator retaining rings, and shaft keyways exposed to torsional fatigue. Replacing a rotor based on conservative database assumptions is expensive, and running one without condition data is a risk few owners will accept. Structural Integrity Associates’ (SIA’s) turbine and generator team brings inspection, engineering analysis, and metallurgy together, so those decisions rest on measured condition rather than worst-case estimates.
The inspection program is built around advanced nondestructive evaluation that reaches flaws without disassembly. Rotor bore inspections pair multi-channel ultrasonic and eddy current testing, supported by in-house bore machining, honing, and plug manufacturing so the replacement plug is ready the moment the exam ends. For solid rotors with no bore, linear phased array (LPA) ultrasonics sweep the entire central volume from the outside surface. The same approach sizes cracking in disk bores and keyways, turbine and valve casings, and—through an EPRI-demonstrated process—tangential- and axial-entry blade attachments. Generator retaining rings are examined in place, using ultrasonic, eddy current, and time-of-flight diffraction (TOFD) techniques. SIA also offers LPA alternatives to OEM-recommended exams, including Westinghouse OMM-13/OMM-14 inlet sleeve and nozzle chamber inspections and a GE TIL 1292 generator rotor dovetail inspection that avoids pulling retaining rings and slot wedges.
Inspection findings feed life assessment tools SIA developed in partnership with EPRI. SAFER-PC combines transient thermal-elastic finite element analysis, fracture mechanics, and boresonic data to set rotor reinspection intervals. The team uses advanced software to evaluate rotors with blade-attachment stress corrosion cracking and estimates the probability of crack initiation, growth, and failure in retaining rings. When database properties point toward retirement, miniature sampling removes a small wafer from a rotor bore or disk face for chemistry, hardness, and microstructure testing at SIA’s Metallurgical Laboratory in Austin, Texas, which also performs rotor, disk, and blade failure analysis. SIA’s advanced engineering group adds steam chest life assessments, crack criticality evaluations, and root cause analysis, while vibration and torsional monitoring tracks the transient events that consume generator shaft fatigue life.
The outcome is a defensible technical basis for run, repair, or replace decisions on steam turbine and generator rotors across fossil and nuclear fleets—one that can avoid unnecessary machining, extend the interval between inspections, and direct maintenance spending toward the areas of real risk. Contact Structural Integrity Associates to scope a turbine-generator inspection or remaining life assessment.