Generator Retaining Ring Inspection and Evaluation

Dozens of utilities throughout the world have saved millions of dollars by continuing to operate generator rotor retaining rings that OEMs have condemned. This course covers metallurgy, design, NDE, and fracture mechanics analysis of retaining rings. Solutions are presented that detail how utilities determine a favorable cost benefit to maintain their 18 Mn - 5 Cr rings, as opposed to replacement with 18 Mn - 18 Cr rings (typically recommended by generator OEMs).

Course Outline

• Retaining Ring Inspection and Life Assessment
  • Root Cause Analysis of a Retaining Ring Failure
  • Overview
  • Plant Operating History
  • Visual Inspection of Ring
  • Metallurgical Study
  • Stress Analysis
  • Fracture Mechanics
  • Conclusions
  • Recommendations
  • Summary
• · Retaining Ring Nondestructive Inspection
  • Crack Closure and its Effects
  • Conventional Pulse Echo UT
  • Time-of-Flight Diffraction UT
  • Mode Converted L-wave UT
  • ID Creeping Wave UT
  • Linear and Annular Phased Array UT
  • Eddy Current
  • Liquid Penetrant
• EPRI’s RRing-Life Computer Program
  • Theory and Program Development
    • BasicConcepts
    • Finite Element Stress Analysis
    • Probability of Moisture Exposure
    • Material Properties Database
    • Ring Sections/Flaw Models
    • Monte Carlo Analysis
  • Program Applications
    • Installation/Hardware Requirements
    • General Program Features
    • Program Moduls and Their Use
    • Basic Sample Problems
    • Advanced Sample Problem

INSTRUCTORS

Larry Nottingham - a Senior Associate at Structural Integrity Associates, received his BS in Mechanical Engineering from the University of Pittsburgh and completed extensive graduate coursework in Metallurgical Engineering at Carnegie Mellon University and the University of Pittsburgh. He has over 34 years of experience in power plant engineering and NDE. Mr. Nottingham's expertise is in the time-of-flight diffraction technique and phased array ultrasonic technologies, including annular and linear arrays. He has been instrumental in expanding these technologies to a number of new applications. Larry also has extensive experience in the design and manufacture of generator rotors, including retaining rings.

Darryl Rosario - an Associate at Structural Integrity Associates, received his MS in Mechanical Engineering form the State University of New York at Stony Brook. He has over 25 years experience in stress and fracture mechanics analyses of power plant components with expertise in deterministic and probabilistic fracture mechanics methods, including high temperature creep-fatigue crack growth. He was developer of the EPRI LPRimLife computer code to evaluate rim-attachment cracking in LP rotors, and co-developer of the EPRI Creep-FatiguePro computer code module for application to turbine components. He contributed to EPRI SAFER and Turbo-X computer codes for performing remaining life evaluations of turbo-generators rotors, and was co-developer of economics-based risk assessment method for boiler tube failures.