Unit trips on spreads @100mw. When coming up unit has runbacks between 30 and 50 mws. This has been on going and doesn't happen every time. Changed cans per ge and unit continued to have same issues over a year but fine once units gets in mode 6. Baseloaded plant 24/7. We tripped recently and unit had a back fire type noise that has never been heard before keep this in mind. We have tried starting back up 4 times now and results in the same issues. We don't hear back fire noise any more but we still have the run back issues and now a new issue. When sitting between 90&110 mws trying to blend unit spreads are in 30s. After sitting still 2 or 3 mins we start to hear a train like noise and after about 5 mins the windows start to shake bad. Monitors on wall start shaking. Vibs go from .1 to .3 or .4. Nothings crazy or unusual. Igv go to 17 degree the vsv are a lil off from the other unit but igv on the other unit with same load are 30 degrees. And are last start that was good this unit was at 30 also. When we moved load to 115 they were at 6 degrees. Then all of a sudden spreads go 3 or 400 out while sitting still not moving load at all. Unit trips and we get several vsv and gas valve alarms. Hyd. Psi shows stable 1575 no drop. But when we stroke the vanes offline lift psi drops 1k or more and trips off tg but control stays good no swing. No dynamic issues. Tuner says combustion looks great. Anyone ever experienced anything similar? Thanks

 

When we stroke and calibrated igv and vsv there was a discrepancy but has since been cleared and everything passes as normal.