1. What is the MW capacity of your steam turbine? single shaft 620 NMw
2. At what ambient temperature will your steam turbine begin to lose generating capacity? 80 deg F
3. Please provide any typical data correlating ambient temperature and lost MW, including the typical maximum temperature at your plant and the corresponding maximum MW loss.
80 deg F – 25 NMw derate
85 deg F – 50 Mw derate
9p deg F – 65 NMw derate
4. Please provide operating backpressures that correspond to the data in item 3.
All cases above back pressure at 13 In Hg
5. Describe actions taken to manage high backpressure in the ACC as temperatures approach and exceed problem levels..
Installed Gale Breaker wind screens, impact no noticeable, EPC skipped the upper perimeter wind screen which provided most the benefit during FEA modeling
Installed air removal piping orifice to balance air removal and prevent recirculation of air into other HX. No noticeable improvement.
Performed air in leakage testing, very tight, less than 5 SCFM non condensable ejection. No noticeable improvement.
Other degradation in performance corelated to increase windspeed and to higher solar radiation. 20 mph increase in wind speed usually produces a 2 In Hg increase in BP. Solar radiation increase of 70 w/m2 on low windspeed increases BP by 3.5 In Hg.
Other ACC issue includes excessive fan bridge vibration; gearbox oil breakdown. Performed FEA on ACC structure, including modal analysis, to develop a fan bridge modification to cut seismic vibration by 40%. Greatly reduce gear box seal leaks over time.