Figure 1. Ameren’s 2,400 MW Labadie plant in Missouri.
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The first supercritical coal-fired boiler to have a scanner system installed was on PPL’s Unit 3 (800 MW) at Brunner Island, which was commissioned in early 2007. Two scanner monitoring areas use arrays of 81 and 91 sensor locations. The thermal monitoring capabilities of the scanner are used to detect and evaluate possible damaging fireside tube wall conditions that might be responsible for circumferential cracking of the tube walls, and is part of an EPRI-sponsored research project.
Martin Lake’s scanner application is similar to that of Brunner Island. It also is on a large supercritical coal-fired boiler (850 MW). However, the installation differs in that the unit uses water cannons to control wall slagging instead of steam sootblower jets. Martin Lake’s scanner system employs two arrays of sensors (56 and 77 locations) on two adjacent walls of the boiler (front and right). The scanner’s data is providing new insight into the boiler wall’s thermal behavior and the consequences and effectiveness of water cannon activity.
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underline;">Key takeaways: It is possible to instrument complete walls with a scanner to provide a comprehensive picture of thermal behavior. The scanner systems are proving to be useful tools in understanding the behavior of both sub-critical and supercritical boiler walls, and the impacts of wall cleaning and natural wall shedding. The systems help operators fine-tune boiler operations, optimize conditions and avoid unscheduled downtime for repairs.
Steam turbine-generators and auxiliaries
Case study: Ameren upgrades 43 steam turbines, using 5 turbine manufacturers, and summarizes the lessons learned One of Ameren’s plants, the 2,400 MW Labadie plant in Missouri, underwent a plant-wide improvement initiative during a 15-year period from 1988-2003. As part of the total upgrade, Ameren retrofitted its HP/IP steam turbines at Units 1 and 2, changing from a reaction to an impulse design, and from partial arc to full arc admission, resulting in a 27 MW unit increase. Units 3 and 4 subsequently were upgraded with new HP/IP and new LP turbines, giving a 56 MW unit increase. These changes were among 43 steam turbine retrofits Ameren has completed.
The goals for each unit scheduled for upgrade included:
Increase major outage interval to 12 years (100,000 equivalent hours)
Increase efficiency and reduce leakage
Restore aging loss – performance degradation
Decrease maintenance costs/problems
Reduce solid particle erosion
Increase moisture erosion protection
Reduce potential for stress corrosion cracking, and
Coordinate performance with all other plant projects
Key takeaways: Ameren accumulated a detailed history of “how to do” steps that ensure the upgrade project is as trouble-free as possible. In developing the list, Ameren’s staff was guided by several installation and operational problems that, for some units, had to be corrected before final completion. Ameren has identified key issues when retrofitting upgrades for steam turbines:
Ensure measurements are taken as maintenance outages allow so competitive bidding can occur
Develop a detailed specification for the retrofit, incorporating all the design parameters and desires needed
Thoroughly review all proposals and get answers to all questions prior to awarding the contract
After award of the contract, follow progress at manufacturing facilities to ensure the quality of the product is equal to expectations
Plan all aspects of the project, addressing potential risks and contingencies
Follow work closely with competent oversight during installation
Communicate/train all personnel prior to startup about what to expect and how to react when items outside of expectations come up
“Trust but verify” during all aspects of the project
