Kahe pioneers use of T91 for superheater-tube replacement
Modified 9Cr steel--referred to as T91 for tubing and P91 for piping--is a relatively new alloy that has seen more powerplant service in Europe than in the US. In Germany, for example, P91 has been specified in most high-pressure/high-temperature refurbishment work since the late 1980s, and has been used in virtually all new construction projects since 1992. The 9Cr steel was first used in the US by Dayton Power and Light Co. (DP and L) in a piping application. DP and L used P91 to replace one secondary-superheater header in 1990 and to replace three more headers over the next two years. The utility`s P91 headers have been in operation for more than 33,000 hours without incident. At least two other major US utilities have used the new alloy for piping application since then. Hawaiian Electric Co. (HECO) is one of the first US utilities to apply 9Cr steel to tubing projects. HECO`s Kahe station Unit 5 had experienced a series of failures of secondary-superheater tubes. Availability of this 150-MW base-load facility is essential to system reliability for the entire island of Oahu. A life-extension study proved the feasibility of replacing the entire secondary-superheater tube bundle and T91 was selected as the optimum material. This article describes the selection and replacement processes.
- OSTI ID:
- 51697
- Journal Information:
- Power (New York), Vol. 139, Issue 1; Other Information: PBD: Jan 1995
- Country of Publication:
- United States
- Language:
- English
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