Cumberland last stage blade failure investigation
- Tennessee Valley Authority, Chattanooga, TN (United States)
- Stress Technology Inc., Rochester, NY (United States)
TVA`s Cumberland plant has two sister units which are rated 1,300 MW each, and have been in service since 1973. Five other units in the United States share the identical design and configuration as the Cumberland machines, and have a similar operating history. Relying on a cross compound design, these machines have an HP turbine and two LP turbines in line A, an IP turbine and two LP turbines in line B. The four double flow LP turbines are identical in design. The L-0 stage is comprised of 71 free standing blades, each of which measures 30 inches from hub to tip. On December 3, 1993, Unit 1 experienced an in-service catastrophic failure. Subsequent inspection revealed that blade {number_sign}35 in the L-0 stage, LP1 turbine end of A line had failed in the airfoil near the platform. The separation of blade {number_sign}35 caused a revere rotor unbalance which resulted in extensive consequential damage to all the components in the A line rotor train. To manage the forced outage and minimize the unit downtime the plant needed to establish (a) a list of immediate actions to restore the damaged unit and return it back into service and (b) the long term actions which should be taken to ensure the reliability of both the damaged machine and its sister unit. A key issue included within this decision making process was to identify the root cause of failure of blade {number_sign}35. By relying on the EPRI BLADE{trademark} program, TVA was able to initiate a technical investigation in parallel with the repair efforts being performed with the cooperation of the Original Equipment Manufacturers (OEM). Based on the technical detail generated in part with BLADE, and supplemented with a series of additional tests and studies, TVA was able to bring Unit 1 back into service and reduce the downtime by 58 days, and thereby save an estimated $25.55 million towards the purchase of replacement power.
- OSTI ID:
- 207811
- Report Number(s):
- CONF-951010--; ISBN 0-7918-1488-2
- Country of Publication:
- United States
- Language:
- English
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