LP turbine retrofit of Encina 4 and 5
Conference
·
OSTI ID:405665
Power producers are faced with the ever increasing challenge of providing cost effective and reliable power to their customers. Having reliable generating equipment is a prime concern. In 1992, San Diego Gas and Electric (SDG&E) contracted with Siemens Power Corporation (SPC) to provide a low pressure (LP) turbine rotor and inner casing replacement for its units 4 and 5 at the Encina Power Station in Carlsbad, California. These units were doubleflow single casing LP turbines originally manufactured by Westinghouse Electric and installed in 1972 (Unit 4) and 1978 (Unit 5). The original configuration was the building block (BB) 72 model, which included 6 rows of blades per flow path and a nominal 28.5 inch last stage blade length. This design had suffered from continued problems including loss of tenons, rotor steeple cracking, and blade cracking exacerbated by high back-end loading. Siemens designed a replacement steam path that would best meet the existing steam conditions and fit into the confines of the original exhaust casing, so modification work would be kept to a minimum. The replacement turbine utilized an additional stage, or 7 stages per flow path, with a 32 inch last stage blade. By using this longer last stage blade, the higher back-end loading was significantly reduced. The blading consisted of Siemens T-4 integrally shrouded drum blading on the first three stages, twisted integrally shrouded blades on stages 4 and 5, and free standing-blades for the last two rows. In addition, the last stage stationary blading utilizes a curved forward design, or {open_quotes}banana{close_quotes} blade, that distributes steam flow across the airfoil more evenly. The retrofit outages of the units had a duration of approximately 6 weeks each. Unit 4 and 5 returned to service in May and December 1994, respectively. The low pressure sections were retrofitted with the reliable Siemens design and achieved unit heat rate improvements of 2.3% and 2.7%, respectively.
- OSTI ID:
- 405665
- Report Number(s):
- CONF-951208--
- Country of Publication:
- United States
- Language:
- English
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