Vibration: GE Power & Water
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katibraVibration: GE Power & Water
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katibraGE Power & Water
Vibration
Tim Maker, Principal Engineer
Combine Cycle Users Group (CCUG/STUG Conference | Orlando, Florida | August 24-27, 2015
Imagination at work
© 2015, General Electric Company. Proprietary information. All rights reserved.
GE Power & Water
© 2015, General Electric Company.
GE Proprietary Information - The information contained in this document is
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and shall not be used, disclosed to others or reproduced without the express
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All relative statements are with respect to GE technology unless otherwise noted. 2
© 2015, General Electric Company. Proprietary information. All rights reserved.
Vibration
© 2015, General Electric Company. Proprietary information. All rights reserved.
Vibration levels
Shaft
vibration
Common comments
• I just came out of an outage
with higher vibration levels
• My rotors were low speed Outage
balanced (or high speed) and
vibration is still high
• Can I operate at these levels?
Bearing
metal temp
Post outage, vibration levels will likely be different
© 2015, General Electric Company. Proprietary information. All rights reserved.
Vibration levels
3 primary GEK’s govern GE vs. ISO vibration limits
(Bearings > 10")
vibration protection for 15
GE steam turbines:
MILS (Pk-Pk)
10 11.6
9 9.6 10
• For journals < 10” GEK 100468 5 7 7.2
6 6
• For journals > 10” GEK 100469 0
• For 1500/1800 Rotors – Alarm (REL) Alarm (ABS) Trip (REL) Trip (ABS)
GEK 100469 ISO 7919-2
GEK 111107
GE vibration alarm/trip set-points are consistent with industry (ISO) standards
© 2015, General Electric Company. Proprietary information. All rights reserved.
Vibration levels
Post outage balance shot – D11 HP coupled pair
HP Bearing #1 HP Bearing #2
• Increased bearing #1 amplitude and no amplitude change for #2
• Excellent measured effect results
An enhanced balance program requires commitment and may take
more than one balance shot
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Sub-Synchronous
Vibration
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Sub-sync vibration
Oil wedge instability –
whip/whirl
• Almost instant on-off
• Can appear as a step change
• “Noise” in direct vibration
• Direct vibration > 1x levels
• Could be seasonal
• Often load limiting Vibration with step change
Detailed vibration data is needed to diagnose
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Sub-sync vibration
Oil wedge instability – whip/whirl
• Occurs near first horizontal natural resonance
• Often occurs on rotors with low vibration levels
1st H
1st V
Direct vibration
1X or synchronous
First vertical frequency
is often associated
with steam whirl
© 2015, General Electric Company. Proprietary information. All rights reserved.
Sub-sync vibration
Oil wedge instability – typical causes
• Lube oil quality – GEK 46506
− Water in lube oil
− Cooler leak
− Steam leak
• Alignment/bearing loading
− Recent outage
− Steam leaks
− Piping forces
• Excessive bearing clearance
− Bearing wipe
− New bearing
− Machined journals
10
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Sub-sync vibration
Oil wedge instability – corrective actions
Temporary:
• Adjust oil temperature/pressure
• Introducing a slight “stabilizing” unbalance
• Introduce a misalignment to increase bearing load
• Influence negative heat/alignment influences
Permanent:
• Restore lube oil properties
• Restore bearing clearances
• Verify and reestablish correct cold alignment
• Eliminate negative alignment influences
• Change bearing configuration (axial groove, tilt pad, oil
dams)
11
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Sub-sync vibration
Oil wedge instability – case study
Scenario:
• 5 bearing Steam Turbine-Generator, axial
flow, with a reported step change in
vibration, limiting load
• History of sealing steam leak,
contaminating lube oil
Temporary action:
• Add dryers to lube oil
• Lower lube oil temperature
Short term relief but symptoms
returned
Operational data required deep evaluation
12
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Sub-sync vibration
Oil wedge instability – case study
Operational data findings:
• Long term trend of decreasing
bearing metal temperature on the
generator inboard bearing
• Suggesting lower loading and
alignment degradation
Interim fix:
• 5 mil elevation change to load bearing
Long term:
• Cold alignment check and realignment Bearing metal temperature
• Potential thermal growth study
Finding root cause can be lengthy
13
© 2015, General Electric Company. Proprietary information. All rights reserved.
© 2015, General Electric Company. Proprietary information. All rights reserved.