Recently I have commissioned 600 MW Reheat Turbine. It is having tilting pad bearing. Second time bearing No. 5 has been damaged. This time the spring of the upper tilting pad was found broken and from the upper pad corners, white metal was vanished.

Can anyone tell me regarding the problem. Can rolling the machine without barring gear can cause this problem or it is merely erection fault?

 

Mani... what was duration (days, weeks, months) between failures?

Regards, Phil Corso

 

> what was duration (days, weeks, months) between failures?

Two weeks

 

Mani... please bear with me, but I want to be sure we understand each other! Therefore, I am taking a few steps at a time!

Q1) What was the duration (in weeks) from startup to the 1st failure?

Q2) Do you have pictures of the failure(s)?

Q3) Has a metallurgical analysis been made?

Q4) Has the machine been running with a substantial load? Or has there been a significant variation of load?

Q5) What are its electrical parameters, Stator-kV & Amps, PF, Field-Voltage and Amps, Rpm?

Phil Corso (cepsicon[at]AOL[dot]com)

 

Mani, you don’t provide us the type of bearing used such as directed type or flooded type and axial or journal. We will assume that this bearing is journal bearing directed type. Rushing to find answers without collecting and reviewing the bearing operating data (drain temperatures, lube oil supply pressure, vibrations, gland-steam data etc.) and performing RCA, it will be only guessing to find the root cause. Can you also share with us how initially the Turbine was preserved and stored? If the Turbine was stored for extended period without applying extended preservation, the bearings might be rusted and the springs jammed or displaced.

Did you also verify the bearing clearances?

Was the second time bearing failure (spring broken) same as the first time? The contributing factor for the spring could be due to, premature failure, improper pre-loading force on the pads and / or improper installation.

Did you also inspect the bearing (second time) prior installation?
Is the first and the second bearing same batch from the same manufacturer (S/N, material nr etc.).

As regard rolling the machine without barring system, it may be possible for short time (for pre-commissioning checks etc) as long as you ensure that the bearings are provided with lube oil. The normal operation procedure should be utilizing the barring system in automatic mode. Rolling the machine manual (applying external force to move the rotor, via the load Gear box?) might result in unbalanced forces which in turn will result in unbalanced bearing loading!

Good Luck...
A. Oztas

 

Dear Sir,

The bearing type is journal and the lube oil pressure, gland steam temperature and the casing drains every thing was maintained according to the procedure.

The astonishing thing was that the machine was running on 10% load and during the spring failure, no vibration was observed in CCR panel. But one can hear a little knocking sound in bearing number 5 which gave me some doubt and i tripped the machine.

Second time bearing supply was also from the same supplier. Now the bearing has been replaced and the machine is running normal.

I cannot find the cause.