Reliability of steam turbine rotors. [STRAP]
An automated Steam Turbine Rotor Analysis Program (STRAP) has been developed to facilitate the prediction of rotor lifetime given the duty cycle of the turbine and the results of ultrasonic examination from the rotor bore. STRAP consists in part of a preprocessor code that generates the boundary conditions and finite-element mesh for transient and steady-state temperature and stress analyses employing the ANSYS general-purpose structural analysis code. A postprocessor contains fracture toughness, stress-rupture, yield strength and fatigue crack growth rate data for air-melted 1 Cr--Mo--V forgings, on the basis of which the local stress and temperature values are screened to determine the critical crack size, the initial crack size that could grow to critical size within a specified number of hours or cycles and the minimum area fraction of defects which could link up to result in a significant crack. A boresonic data reduction code allows rapid sorting of indicated flaw sizes and locations to find the regions of greatest defect density. At this stage of development, STRAP contains several deficiencies, which are the targerts of the continuing RP502 effort. There are currently no means to assess the probability of temper embrittlement of an individual rotor short of determining the fracture appearance transition temperature, which has been found to be highly variable. No suitable crack growth algorithm has been developed for temperatures in the creep range, and an unequivocal interpretation of the TVA Gallatin rotor burst event in terms of measured mechanical properties is still being sought. Finally, the statistical correlation between ultrasonically-indicated defects and metallographically-determined sizes and spacings is inadequate, mainly because destructive sectioning of two retired rotors failed to reveal any flaws of structural significance.
- Research Organization:
- Southwest Research Inst., San Antonio, TX (USA)
- OSTI ID:
- 6531026
- Report Number(s):
- EPRI-NP-923-SY
- Country of Publication:
- United States
- Language:
- English
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STRAP: steam turbine rotor analysis program. Part 1. General information manual
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Related Subjects
200104* -- Fossil-Fueled Power Plants-- Components
ACOUSTIC TESTING
COMPUTER CODES
CRACKS
DEFECTS
ELECTRIC UTILITIES
FORECASTING
MATERIALS TESTING
MECHANICAL PROPERTIES
METALLOGRAPHY
NONDESTRUCTIVE TESTING
POWER PLANTS
PUBLIC UTILITIES
RELIABILITY
ROTORS
S CODES
SERVICE LIFE
STEAM TURBINES
STRESS ANALYSIS
TESTING
THERMAL POWER PLANTS
TURBINES
TURBOMACHINERY
ULTRASONIC TESTING