Evaluation of service exposed 1Cr-1Mo-1/4V turbine piping

Book · Sun Dec 01 04:00:00 EST 1996

OSTI ID:403325

Ellis, F V ^[1]

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1. Tordonato Energy Consultants, Inc., Chattanooga, TN (United States)

A section of 1Cr-1Mo-1/4V main steam piping was removed after approximately 190,000 hours of service following detection of circumferential cracking at the piping to turbine stop valve girth weld. Evaluation consisted of chemical analysis, dimensional measurement, metallurgical examination, tensile testing and creep rupture testing. Testing was performed on circumferentially and axially oriented specimens. Measured room temperature tensile strengths were independent of specimen orientation and position-tension/compression side of bending moment. The measured minimum wall thickness of 25 mm was below the nominal specified wall thickness of 29.4 mm. Creep and creep rupture testing was performed at stresses from 47 MPa to 98 MPa and temperatures from 665 C to 600 C. Axially oriented specimens ruptured prematurely compared to circumferentially oriented specimens. The measured rupture time for the service exposed piping base material was slightly less than that for minimum strength unexposed base metal, life fraction consumed estimated as 10%. The remaining creep life was estimated using isostress extrapolation and time temperature parametric methods. At the service conditions of 47 MPa and 566 C, isostress remaining lives were 250,000 hours using direct temperature extrapolation and 291,000 hours using inverse temperature. The minimum creep rate was correlated using a Dorn parameter. Based on a correlation with rupture time, the mean life fractions at the end of primary creep, end of secondary creep, and offset tertiary were 0.065, 0.185, and 0.44, respectively. For creep through the end of secondary creep, a rational polynomial plus steady state creep constitutive equation was used. For tertiary creep, the linear strain softening creep equation showed reasonable correlation.

• OSTI ID: 403325
• Report Number(s): CONF-960706--; ISBN 0-7918-1782-2
• Country of Publication: United States
• Language: English

Related Subjects

20 FOSSIL-FUELED POWER PLANTS
36 MATERIALS SCIENCE
CRACK PROPAGATION
CREEP
EXPERIMENTAL DATA
FOSSIL-FUEL POWER PLANTS
MECHANICAL PROPERTIES
MECHANICAL TESTS
RUPTURES
SERVICE LIFE
STEAM LINES
STEEL-CRMOV
TENSILE PROPERTIES