1. Unit 6 Turbine Vibration Investigation - Observation by PMT

2. Polar plot of IP and LP rotor when turbine load was 280 MW
and worsen vacuum condition
Out of phase
pattern between bearing 3/4
and bearing 5/6
Bearing no. 3
Bearing no. 4
Out of phase
pattern
Bearing no. 5
Bearing no. 6

3. Compared to past record in Aug 04
Bearing no. 3
Bearing no. 4
Bearing no. 5
Bearing no. 6

4. LP bearing vibration increase Test 1 Throttle mode and control vacuum
Throttle mode and normal vacuum
LP bearing
vibration increase

5. When go to worsen the vacuum, the vibration reduce significant
Bearing no 5 & 6 vibration
280 MW
220 MW
Vac 720 mmHg
Vac 740 mmHg

6. Opposite vector effect between bearing no. 5X and 6X
Phase shift position at high vibration
Phase shift position at high vibration
Low vibration position
Low vibration position
Opposite vector effect between
bearing no. 5X and 6X
when the vibration increase
under normal vacuum
Bearing no. 5
Bearing no. 6
Phase shift position at high vibration
Phase shift position at high vibration
Low vibration position
Low vibration position

7. Rotor movement direction
Bearing no. 6
Vector sum
direction
6Y vector
6X vector
B side
LP rotor
Vector sum
direction
5X vector
A side
5Y vector
B side
Bearing no. 5

8. Orbit plot show enlarged when vibration increased
Bearing no. 5
Bearing no. 6

9. Past record in Aug 04 High vibration orbit Bearing no. 5 Bearing no. 6
Traditional phase pattern from
technical paper
Bearing no. 5
Bearing no. 6

10. Bearing no. 5
speed
Vibration
Run down
Shaft centerline

11. Bearing no. 6
speed
Vibration
Run down
Shaft centerline

12. Turbine vibration when bearing lube oil temp control changed +/- 2ºC
LP vibration still appeared

13. after LP rotor balancing
Run down on 11 April 07
No significant change in
critical speed
Run down on 07 April 06
after LP rotor balancing

14. LP rotor bearing vibration related to vacuum change
Vibration was very sensitive to condenser vacuum change
Vector effect direction of bearing no. 5 & 6 was opposite
Out of phase pattern on IP and LP rotor as compared with past data
Orbit show special preload symptom.