Vibration analysis at Vijajawada.pdf

7/28/2019 Vibration analysis at Vijajawada.pdf

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PROJECT: VIJAYAWADA TPS

PROBLEM: VIBRATION ANALYSIS OF UNIT 5, 210 MW

SIEMENS TURBINE - SIEMENS GENERATOR

VTPS unit 5 was rolled on 23-05-08 after rectification works carried

out for Generator Earth fault. Bently Nevada ADRE Vibration analyzer

system was used for vibration measurements and analysis. During coast

up of the unit, Generator front and rear vertical vibrations were

recorded. The coast up vibration values both amplitude in microns and

phase are given in figure 1. The bode plot shows that the run up of

generator rotor is very smooth.

Table 1 and 2 gives the bearing pedestal vibration levels for Turbine,

Generator and Exciter both in velocity and displacement units. The

table gives 1X running speed vibration component , corresponding

phase and overall vibration levels which is a sum of all vibration

frequency components. The bearing vibrations on all pedestals are

satisfactory except for exciter primarily in horizontal direction. Theexciter vibrations which were 85 microns peak - peak at 3000 RPM

showed a steady increase after synchronization and at rated load were

128 microns peak - peak. Figure 2 shows the velocity and displacement

spectrums of exciter bearing in horizontal direction. The spectrum

shows that the bearing vibrations are predominantly of running speed

component.


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Table 3 gives the control room vibration levels at rated load. The

Bearing and shaft vibrations are satisfactory except at exciter bearing.

The Exciter bearing vibrations are above alarm values . The increase in

exciter vibrations with time before stabilization could be because of the

following reason.

Design diametrical clearance between spigot and recess in Generator -

Exciter coupling should be 0.03mm to 0.05mm . But the measured

clearance at site is 0.12 mm . A 0.05 mm shim has been introduced

between recess in Generator rotor and Spigot in exciter rotor . This

was not providing a desired solution to the high exciter vibration

problem.

A permanent solution suggested would be to ream and introduce dowels

at 120 degrees apart positions on Generator Exciter couplings as

being followed in Hyderabad 120 MW units. Till such time customer

was advised to operate the unit with close monitoring of exciter

vibration levels.


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Fig 1. Generator Front Vertical and Rear vertical Bode Plot


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Figure 2. Exciter Pedestal Vibrations Horizontal, Velocity and

Displacement spectrums

Table 1. Bearing vibrations in Velocity and Displacement units at 3000 RPM


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Velocity in mm/sec Displacement in microns

pk-pk

1X Phase Overall 1X Phase Overall

Vertical 1.2 243?

6 7 333?

10Horizontal 1.0 171? 2 6 260? 8

HP

FrontAxial 1 228? 2.6 6 317? 9

Vertical 1.2 89? 3.8 8 176? 10

Horizontal 1.6 287? 2.1 10 16? 10

HP

Rear

Axial 0.4 98? 1.2 3 186? 5

Vertical 0.6 302? 1.5 4 32? 5

Horizontal 0.1 --- 1.2 1 --- 3IP

RearAxial 0.7 284? 1.1 4 14? 6

Vertical 1.8 358? 2.5 10 84? 12

Horizontal 3.6 163? 4.4 23 252? 26LP

RearAxial 5.2 294? 5.3 33 22? 34

Vertical 4.2 309?

4.2 26 41?

28Horizontal 2.4 297? 3.1 15 26? 16

Gen

FrontAxial 1.5 157? 1.8 10 246? 11

Vertical 4.4 142? 4.9 29 230? 30

Horizontal 2.3 52? 2.4 15 141? 16Gen

rearAxial 1.5 317? 1.9 9 49? 11

Vertical 0.4 180? 1.3 2 263? 5

Horizontal 13 22? 14 85 110? 86Exciter

Axial 6.2 32? 6.6 38 122? 40


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Table 2. Bearing vibrations in Velocity and Displacement units at 215 MW Load

Velocity in mm/sec Displacement in microns

pk-pk

1X Phase Overall 1X Phase OverallVertical 1.0 --- 3 7 313? 8

Horizontal 1.0 --- 3.5 6 242? 9HP

Front Axial 0.9 --- 3.0 5 295? 10

Vertical 0.5 --- 7 4 198 10

Horizontal 1.7 --- 4 10 51? 12HP

Rear Axial 0.8? 2 2 --- 5

Vertical 1.0 --- 0.3 7 120?

11Horizontal 0.5 --- 1.8 3 257 6

IP

Rear Axial 0.3 ---- 1.5 1--- 4

Vertical 4.0 330? 6.2 27 62? 29

Horizontal 5.4 177? 7.2 34 263? 35LP

RearAxial 11 161? 11 70 248? 72

Vertical 7.0 319? 7.9 46 51? 48

Horizontal 2.0 300? 3.6 12 36? 17Gen

Front Axial 2.6 156? 3.9 17 240? 19

Vertical 3.3 128? 5.4 21 213? 27

Horizontal 0.3 --- 3.2 4 146? 12

Gen

rear

Axial 1.3 ---- 2.3 9 47? 11

Vertical 1.7 ---- 3.3 10 339? 15

Horizontal 21 7 21 128 96? 128Exciter

Axial 7 33? 9 47 126? 53


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Table 3. Control room vibration values

24-05-0812.53 hoursLoad: 215.3 MW

Speed : 2954 RPM

Vacuum: -0.885 kg/cm2

Bearing Vibrations Shaft Vibrations

in microns peak

HP Front 1.3 47.3

HP Rear 2.5 39.9

IP Rear 2.4 38.7

LP Rear 2.5 56.0

Gen Front 18.4

Gen Rear 8.3

Exciter 43.4 89.7

Bearing temp

HP front Thrust HP Rear IP Rear LP Rear Gen Front Gen Rear Exciter

62.3 63.3 61.3 86.3 83.3 78.2 78.9 54.767.2 61.5 59.3 75.1 85.6 72.4 73.6 59.7

54.1 69.0 59.975.7 68.8 57.2

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Vibration analysis at Vijajawada.pdf