Monitoring, detecting, addressing combustion-dynamics anomalies
Challenge. H L Culbreath Bayside Power Station generates approximately 1800 MW of combined-cycle and 200 MW of simple-cycle power for Tampa Electric Co (TECO), an Emera company. The plant has seven 7FA.03 gas turbines (GTs) equipped with DLN 2.6 dry, low-NOx combustion systems. The GTs began commercial service in 2003 and 2004.
The two combined cycles are monitored remotely by GE Power Services’ Monitoring & Diagnostics (M&D) Center in Atlanta. GE, including the Atlanta M&D Center, has supported Bayside under a contractual services agreement since 2003.
In 2015, TECO began participating in a remote M&D pilot project spearheaded by GE’s Power Services business and its Intelligent Platform’s Smart Signal predictive diagnostics software and services team. As part of this cross-business M&D initiative, GE conducts weekly conference calls to update TECO team members on Bayside equipment performance. The M&D Center focuses on the station’s gas and steam turbines; Smart Signal on most of the balance-of-plant equipment, plus some turbine and generator data.
Prior to the existence of GE’s M&D Center, many combustion and other issues might not have been detected until they caused hardware damage or a unit trip. Up until a few years ago, most plants had to rely on their own M&D teams to detect and analyze issues such as combustion dynamics. Also, prior to the development of remote combustion tuning capability via the M&D Center, field specialists had to travel to the plant for this purpose.
The proactive collaborative relationship between utility and service provider to focus on remote M&D paid off in May 2015 when GE’s detection system identified combustion-dynamics anomalies in two Bayside GTs.
Solution. On May 21, GE’s monitoring analytics triggered an alert to the Atlanta M&D Center regarding elevated pressure pulsations in the combustion chambers (dynamics) on Unit 2D. A week later, the OEM’s proprietary analytics detected an anomaly in the exhaust temperature readings of Unit 1B. Because these anomalies involved GT combustion systems, the Atlanta M&D Center took the lead. It has the visualization and analytical tools to evaluate dynamics and other operational data, as well as staff experienced in data analysis.
The GE Remote Tuning Group, based at the Atlanta M&D Center, works with plants to remotely adjust fuel flows, thereby tuning the unit to achieve optimal emissions, combustion dynamics, and flame stability. M&D specialists collaborate with the remote tuning team to resolve combustion operability issues.
In response to the Unit 2D alert, an M&D specialist determined the unit required a seasonal retune to improve flame stability and reduce dynamics. The alert on Unit 1B was triggered by a shift in some of the exhaust thermocouples. M&D staff traced the exhaust-temperature anomaly to combustion can 12.
Upon receiving GE’s report, Bayside personnel collected NOx emissions data for Unit 2D (the M&D Center does not have direct access to this information) and presented it to an OEM combustion expert. The M&D Center’s initial conclusions were confirmed by these data and a remote seasonal retune was scheduled.
NOx data from Unit 1B also were reviewed, along with the unit’s operational, tuning, and inspection history. M&D experts concluded the temperature anomaly traced to combustor 12 did not merit action at that time. However, the analysis did reveal that the unit was operating with a relatively lean fuel-to-air ratio, like Unit 2D, so a remote tune was scheduled for that machine as well. In-service remote tuning of each unit took about six hours.
Results. Tuning successfully improved flame stability, thereby reducing the risk of unit trips from lean blow-out. It also reduced the elevated combustion dynamics on Unit 2D, which if not corrected, could have contributed to premature failure of the combustion hardware.
Quick response to the issues affecting both GTs enabled Tampa Electric to be proactive in keeping its Bayside plant operating during the critical summer months.
The retuned units contributed to Bayside’s record generation in July and August, 2015. The new record for July was more than 967 GWh; August nearly 939 GWh. The previous record for July, set in 2009, was 906 GWh.
- From Bayside, Chip Whitworth, manager of engineering and maintenance; Tiller Mills, maintenance specialist
- From GE Power Services, Justin Eggart, GM fleet management; Christopher J Held, engineering manager; M&D center team led by Mansoor Dar
H L Culbreath Bayside Power Station
Tampa Electric Co
1800-MW, gas-fired, two 3 × 1 combined-cycle units located in Tampa, Fla
Plant manager: Scott Cannon