Hello,

Im Khafiz, i have a problem in my power plant. We have overhaul now. As per attachment attached, bearing no 3 for turbine end was
-Bottom half bearing white metal had
bad scoring.
-Two area had deep crack/hole
The vibration and temperature was stable for pass 4 years( last overhaul was 2006)

Machine info - Turbine Gas Siemens CC 110 MW 10.5 Kv 3000 rpm 50hz

Any idea how can this happen, based on last overhaul, we had same problem. We already upgrade our earthing system.

Trending.ppt (1,826 KB, 75 downloads) Finding

Starting the brain storm... input anyone?

Khafiz,

1. When you say this was found during the last overhaul and the turbine has been smooth during the last 4 years, any chance the old bearing was re-used?

2. Your PI trend only shows the last 365 days. Was this turbine was rolled up from zero during the last 4 years, without operating on turning gear?

3. Bearing is closest to the turbine, high back pressure?

4. Didn't your last shut down show abnormally high vibration? Even though you highlighted the previous 4, this one looks like it happened during coast down. Did your turbine come to stop rather quickly?

This message has been edited. Last edited by: CBM Novice,

ALTHOUGH IT DOES NOT SHOW ANY SIGN OF FLUTING, THE EARTHING BRUSHES SHOULD BE CHECKED. IT MAY BE COMBINATION OF FLUTING AND FATIGUE FAILURE OF BABBIT WITH TIME. WHAT IS THE THICKNESS OF BABBIT IN THE BEARING? HAVE YOU DONE UT OF BEARING BABBIT TO CHECK ITS BONDING STRENGTH?
IRSHAD

first of all, Irshad, why do you always use capital letter in your words? capital words means means you are shouting.. anyway, agree with you that it is related to electrostatic dish.

Khafiz, selamat pagi!.. instead of scoring, it looks to me the bearing surface is having frosted appearance which normally associated with electrostatic discharge attack or surface fatique.

110MW is hell of a beast. you should have online monitoring isnt? if so, look at the orbit timebase. you should see random spikes in it if it is electrostatic dish issue. if not, then it is surface fatique

Poor bonding of babbitt might have caused this.

Else look for the directional/eccentric movement of the shaft within the bearing. This may happen due to a minor imbalance (hence no high vibration) on the rotor due to deposits.

Because of the location of the damage I would guess you have a problem with your prelube system. Does your postlube last until the unit rolls to a stop?