Dear sirs

we have Frame 5 LA unit very old unit after MI , can not be start , its stays on FSNL mode 2 minutes ,and vibration climbing till 25mm/sec and it trips
rotor float is 18 mils, all blades installed as per moment weight chart, bearing clearances and seals are ok
Vibration climbing from when it reaches to 5000 RPM , 4 and 5 mm/sec , then it climbing to 25 mm.sec it trips
tried to balance with with balancing engineer,
but didnt helped, it helped but little bit, but its climbing somehow till 25 mm/sec

please advice what can cause it ?
regards Adil

 

Despite balancing efforts, a residual rotor imbalance could still exist. Imbalance may worsen at specific critical speeds due to resonance. Verify that all blades are installed correctly per the moment weight chart and double-check weights and moments.

 

all buckets installed as per balance sheet
alignment is correct
bearing clearances is good
seals is also double checked
but after we reaches to 5000 rpm its climbing up till 25 mm/sec
after flame out it reaches to 40 mm/sec vibration
what can cause it

 

Despite balancing efforts, a residual rotor imbalance could still exist. Imbalance may worsen at specific critical speeds due to resonance. Verify that all blades are installed correctly per the moment weight chart and double-check weights and moments.

all buckets installed as per balance sheet
alignment is correct
bearing clearances is good
seals is also double checked
but after we reaches to 5000 rpm its climbing up till 25 mm/sec
after flame out it reaches to 40 mm/sec vibration
what can cause it