Evaluation of LP Rotor Rim-Attachment Cracking Using LPRimLife

摘要

Stress corrosion cracking (SCC) in the blade attachment region of low-pressure (LP) turbine rotors ahs emerged as one of the most significant problems affecting both nuclear and fossil steam turbines today. To assist turbine operators in evaluating the remaining line of LP rotors with known or suspected cracking, an easy-to-use PC-based computer program, LPRimLife, was developed for EPRI by Structural Integrity Associates. The first phase of development, incorporating the methodology for evaluating cracking in General Electric (GE) dovetail (straddle-mount) attachments, was completed in 1999 [1]. The second phase, which included evaluation of cracking in Westinghouse axial-entry (steeple) attachments, was completed in 2000 [2]. The third phase, to address cracking in GE multi-pin-finger attachments, is currently under way. Since initial development, the LPRimLife computer code has been successfully employed at nuclear and fossil plants providing the basis for deferring or eliminating major unscheduled and costly repairs, such as "pressure plating," which would have significantly extended the outages. Deferring unscheduled repairs for even one more fuel cycle allows for advance planning to evaluate and select the most-effective repair/replacement option and lead time needed for procurement of appropriate materials/services. In today's competitive marketplace with ever-tightening outage schedules, timely application of LPRmLife has resulted in significant cost savings to utilities. This paper provides a summary of the LPRimLife program methodology, software features and recent utility applications.