turbine thrust bearing temperature going high

Is your bearing cooled by oil? Check that pressure is good and oil is not overdue replacement or ports blocked.

Otherwise, it could mean excessive wear on the bearing.

Or, remotely possible is the bearing is the wrong one for application.

You would expect bearing temp to increase when there is more load on it, but as long as you are within tolerances for load it should be fine.

Drew

Thrust bearing temperature seems from your note to have a definite relationship to load. This is quite normal, but is magnified if the turbine is getting fouled.

- Check the efficiency across the machine and compare with the OEM curves.

- Check the trend of the after first stage wheel pressure. An increasing trend indicates downstream blade fouling which will increase thrust load.

- Check the trend of exhaust conditions - temperature and pressure/vacuum and compare to earlier readings. Deterioration is another indicator of blade fouling.

- Check oil condition. Varnish formation on the thrust pads can cause a temperature rise.

- Check oil flow, temperature and pressure.

- Check that the turbine is free to expand - no rust or over tight bolts preventing expansion.

- Check check and check everything again.

Also check boiler feedwater quality.

dear sir

there has been no change in first stage pressure and no change in exhaust condition. a fortnight bak the near by journal bearing was replaced due to the problem of flow of babbitt at the time of stopping. the thrust bearing temperature aws 87 deg before replacement of journal bearing rose to 92 deg initially and gradually it has crossed 100 deg yesterday. we may have to take out the unit in a day or two for inspection. the main concern is why it should rise so slowly and so sensitive to speed(grid frequency). The oil quality is ok and the vibration of other bearings are well with in the limits( 20 to 40 microns). since we have only one temperature probe we have to rely on its measurement. till now we have not faced any errors of any intrumentaion( almost after 18 yrs commissioning ).

is there any way can we control the rise. what could be the probable reasons.

sincerely yours

p k mohapatra

Change in bearing supplier? Bearing clearance factor the same? Quality of bearing? Don't know the history so i would start looking here as it seems to be last part replaced.

Is this a recent problem? have you done any recent maintenance on any of the plant?

Regards JD

my dear first of all check and calibrate the temp indicator i think that you have a tilting pad thrust bearing check and measure the inlet flow of oil of this bearing

The temperature rising with load and speed- indicates the unbalanced thrust. Check the steam paths whether there is an excessive unbalance exist.

The axial float (shift) within limit signifies the thrsut bearing (I assume the loaded side) is still alive.

Still 100+ degrees is a bit high for the bearing.

With your information, I think the bearing has problem.

Check also the TI right after lube oil return and comparing to previous data

If it is high then you have problem with the bearing

Are u driving a generator? If yes then check whether the gen was coupled at it's magnetic centre. If not then as gen load changes its axial position will change.

Temperature is rising it means there is low oil supply which is not sufficient to carry away the heat generating in the bearing, how ever other parameters are normal therefore concentrate on checking oil system for the bearing.

Plese check the followings

1. Lub oil temperature at inlet and outlet.

2. Lub oil flow to the bearing.

3. Inlet/outlet lub oil pipes for any blockage of flow restrition.

dear mr hari ram

many thanks . we have taken out the machine from grid and it is on the process of cooling down. we will check the oil supply and return after dismantling the bearing. In our system there is no orifice in the inlet and we do not have any provision for increasing the oil quantity. can you please suggest in case we do not get any abnormality then what should be the next best possible course of action.

i will be in touch as soon as it is opened for inspection.

p k mohapatra

If you have chance to shutdown then check the lube oil cooler

Possible oil vanish create a profile on cooler plate sheet resulting in bad heat transfer

For further investigation please concentrate on thrust pads. Check them for freeness, and clearance and surface finish of the bearing planes.

The thrust bearing has been dismantled and 6 pads have been checked for freeness. the pads are supported over pivots. the passage for oil has also been checked. Around 20% of the area of each pad has lost its shine. However these pads have been found ok on UT. the main concern is why these marks . Are the pads overloaded or is it due to oil starvation? The axial float has not changed since last inspection . The turbine was overhauled in 2004. Next overhaul is due in 2010.

can you please advise whether such behaviour is normal.

p k mohapatra

The tilting pad bearings do not usually take load uniformly over its serface eually (it tilts such that a suitable wedge action is formed)

The matty finish in the area is not important (I have seen much more area losing it)

In case of the problem you thought, the bearing would have lost the babbit (or at least there would have been pitting, only initially, before losing the babbit altogether)

Thsi will eb for oilstarvation too, and I have seen journals/ thrust collars blackening due to heat as well as discoloration on the pads. None of them exist for you.

The problem is not at your thrust pad,

Did you check up some sort of leakage taking place? I am not sure about the construction, but in certain models I know, in case of the seal air failure hot gases (steam for you) may enter the bearing zone.

Did you monitor the lube oil temperatures ?

<...what could be the probable reasons?...>

Here are two:

• A shortfall in maintenance activity at the facility
• A failure to shout for help earlier

How did the phone call with the <...116 mw steam turbine...>'s original manufacturer go?