WDPF instrument termination enhancement
Blackhawk Station
Owned by Borger Energy Associates LP, Operated by NAES Corp
230-MW, gas-fired, 2 × 1 combined-cycle cogeneration facility located in Borger, Tex
Plant manager: Craig Courter
Key project participants: Bryan Stout, maintenance supervisor; Steve Nelson, operations supervisor; Alan Bull, project manager
Challenge.
Blackhawk Station had experienced numerous thermocouple failures since beginning commercial operation in 1999. These failures caused countless turbine trips from load over a 12-yr period, resulting in lower than desired reliability.
Solution.
Bryan Stout, maintenance supervisor, has worked at Blackhawk for seven years in several roles including operator and I&E technician. During his time at Blackhawk, he played an instrumental role in troubleshooting several design issues related to the site.
One of the most prominent issues that the site was dealing with was recurring thermocouple failures in the gas turbines. Operators continually reported blade-path thermocouple failures following startup and during normal runs.
Maintenance technicians had tried multiple times to correct the issue and had actually gone as far as moving the wiring harnesses away from the turbines and replacing all thermocouples and pulling new signal wire to remedy the issue. This did not result in any improvement. Technicians then tried replacing input cards but still had the same recurring failures.
Stout had been one of the lead technicians in troubleshooting this issue prior to his promotion. He was convinced that the issue could be resolved and challenged his team to understand the issue and began recording what was done in every instance of failure.
The team then started looking into the design of the instrumentation cabinet (half shell). What they found was that the I/O card connectors were of the push-on type (Fig 94). They were able to mimic a failure by moving these connections in place. They would check each of the connections and screw tightness on the opposite side of the chassis following each failure. This would clear the faulty input. However, upon start up the site would still experience failures.
Stout directed his team to develop a procedure to solder the connections in place. During the following outages they began to solder each connection associated with shutdown points of the combustion turbines. This was a very time consuming process consisting of many connections in a tight place.
Results.
This improvement was started in April of 2010 and was completed on both units in June 2010. The site has not experienced a thermocouple failure since. This is a great achievement as the site has never operated for this long a period without thermocouple failures since COD.