Stress corrosion cracking of Ni-Cu alloy 400 tubes in feedwater heaters
- Consolidated Edison Co. of New York, Inc., NY (United States). Dept. of Mechanical Engineering
This paper presents the results of the inspections and metallurgical evaluations of a high pressure feedwater heater that experienced numerous tube failures after a short service life. Using EPRI NDE Center technical support, tubes were eddy current tested with special probes in the tubesheet region and with conventional probes in the remaining straight portion. Pulled tubes were metallurgically examined. Crack depths were correlated with eddy current indications. Short axial cracks were found on the inner surface of the tubes at roll transitions. Failures were attributed to intergranular stress corrosion cracking. The cold drawn-stress relieved Monel{trademark} (Alloy 400) tube had < 10 KSI hoop residual stress, however the residual stress was probably much higher in the roll transition. A large number of tubes were plugged based on the eddy current indications, however several tubes that showed no indications had leaked a few months later. This suggested that after initiation, crack growth was rapid. The heater was replaced after 4.5 years of service.
- OSTI ID:
- 78283
- Report Number(s):
- CONF-941007--; ISBN 0-7918-1381-9
- Country of Publication:
- United States
- Language:
- English
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