Thrust Pad Temperature Rise

Thrust pad temperature rise is most likely (almost entirely) due to loss of lubrication

This may happen due to-

a) Lubrication failure

b) Excessive axial loading (film squeezed out)

It is assuming it was behaving well till 160MW, you must be of course raising the load slowly and most likely there was no signal on the operations - temperature of thrust pad/vibration/...

How is the physical appearance of the pads? (except wear out - discoloration/pitting etc?)

about .1mm of metal removal in all pads

When I said visual - what was the surface of the thrust pad looking like - and what was the collar like?

The material removal is uniform? ie are there any serrations- pittings,... or the face is still as polished ?

Is there a possibility of unbalanced thrust due to the type of trip?

The thrust bearing is new or the old one? Are you sure the wearout has taken place due to this trip ? it might as well be due to natural causes?

Most likely overload.

What did the turbine speed do during the boiler trip? What did the pump suction pressure and temperature do?

turbine speed 2950 rpm .auxilary lub oil pump starts.oil pressure 2.14 bar ,53 deg .c

So you were running on turbine driven lube oil pump, and when boiler tripped it switched over to electric motor driven lube oil pump?

If so, then that is your problem!! Your lube consol is not operating properly and you had a momentary lack of lube oil during the switch over.

A very common problem. You need to optimize the controls on your lube oil consol and check out the pump switching.

Got to go along with Steve. You may also want to fit a bladder vessel if not already there, and if there is one then check that it is correctly charged. This helps to smooth the pressure dip when changing over pumps.

Normally the thrust pad git wore thats may due of number of time of run and stop the machine and you have to avoide to do this phenomena because time of start up and shudown lead the rotor to possess back and forth movement till arest to its running position.

Also you have to check the oil vescosity and monthly doing analysis and git the result.

you have to check the lube oil pump strainer if there any forigen materials accumelated and cause decrease to the oil supply as well as to check the oil filters.

Your machine actually should have voting system to allow the machine trip befor gitting to high tempreture.

you have to do vibration analysis to know the real problem if its umbalance or preloaded or misalingment and etc...

All the best

thank you vcm inspector. now we are doing all the recommendations given by you. some other areas also we are going to concentrate. after completion of these things ,if same thing occurs ,i will contact you.

Ummm, did you read my post, because I really am pretty sure you have a problem with the pump switch over..

Unit was running to 160 MW it means that all parameters during rolling and loading of the set was normal, after AOH very extensive attention required as during coasting down period set passes through the critical speed, during this period vibrations of T.G. set rise, and bearings settle at position. In this case it is suspected that T.G. set remains in critical zone for long time that result in thrust bearing failure, however by opening vacuum breaker i.e reducing condenser vacuum , coasting down period can be reduced and there is possibility to reduce the damage to the thrust bearing.

Sitting a long time in the critical absolutly does not have anything to do with thrust bearing damage.