Thrust Bearing - Steam Turbine

Check all these issues....

https://canteach.candu.org/Content%20Library/20042414.pdf

....report back....

you can even cheat and search on 'Thrust' to get to the good stuff...

Then there is this .pdf (dates to circa 1975, so it is probably old enough to matter), as the basic principles have not changed.

TAMU tilt plate thrust bearing paper 1975?

#1 Lesson: Do not exceed the design envelope of speed and thrust.

#2 Lesson: Maintain optimal oil pressure and quantity, and maintain optimal oil quality. (this includes keeping water out of the oil, BTW).

#3 Lesson: refer back to #1 and #2 if still confused.

Lubrication?

Overrated.

Now the turbine has cooled down enough to examine the bearings and associated bearing supports, cooling systems, etc what have you found out?

It would be uneconomic to do so. If supplementary lighting equipment is required, it is best sourced locally.

What happened is that the control system worked correctly to protect the equipment from damage due to an over-temperature condition.

It is amazing how many individuals would rather ask a bunch of complete strangers about such things over the internet than pick up the telephone and talk to the equipment manufacturer directly. No. Not amazing. Staggering would be a better word.

Did anyone hear any sharp, loud noises near the turbine exhaust? Maybe you pulled too much vacuum, caused insufficient back-pressure, and got condensation in the final stage of steam turbine. This, as I recall, can result in loss of material by impingement, and will upset the thrust balance point of the turbine, resulting in rapid heating of the thrust bearing with trip.

At the minimum, you should go over the logs, or sequel server, and find out what happened operationally right before that. If vibration monitors are present, did you get any vibration alarms?

Inspection: Visually or bore scope examine the exhaust stage of the LP turbine. Look for new spalling, missing metal, etc.

What happened to thrust bearing oil pressure during these events? You need to examine that as well.

I will assume the bearing or the shaft has some sort of cooling? probably water cooled. check that the cooling system is working.

Yes, also check for coolant blockage on the side with higher temperature, when testing things.

Dear Member,

The reasons could be

1. Improper sensor, cable. Wrong calibration

2. Some blockage in quantum of oil surrounding the sensor - which will allow temp. to shoot up.

3. A portion of oil by-pass the sensor which makes to accumulate heat in that zone and cause problem.

It is not advisable to re-start the turbine with out opening and inspection and sort out the issue.

Otherwise the damage may be catastrophic

DHAYANNADHAN.S

I can agree with everything except the usage of the word "quantum", I think dhayanandhan meant the smallest volute, or smallest volume of based on the Latin root meaning of the word, as this is nothing to do with quantum in the modern context.

Not to be nose picking, but that is certainly an interesting booger.

Figure out (1) what was the history of all recorded data

(2) what is the status of all instrument associated, are they correct?

(3) is there metal in the oil now

Then you will have scratched the diagnostic surface, and may have to delve (dig) deeper to find the truth.

- The oil temperature did'nt change (we have sensor - Thrust return oil temperature)

- The pressure of oil didn't change

- The axial position was in +0,2mm, in the moment of trip it goes to -0,4mm, (I think it's ok, because the bearing load goes down in the moment of the trip - Governor valves and Stop valves close)

- We have two sensors in the same side , both increase temperature in the seconds before trip until trip. one more than other

Then you best start looking for whatever increased the thrust load on that bearing right before the trip. I think you are in for a complete inspection of rotor, blading, and diaphragms. Also look at the other bearings to make sure they are not showing signs of machine misalignment.

How was heat rate looking in the days prior to the trip? Any noticeable changes? Hours before? Every piece of data you can pull up right now is your friend.

In the other bearings - 6 journal bearings - everything ok, we didn't have changes..

Some days before it happens, The eccentricity becomes high and we think that the problem was the sensor.. But maybe it wasn't the sensor of eccentricity..

Maybe the eccentricity was really high

See what I mean? Sometimes we tend to write things off as nonsense, when the real message is the real message.

but what can cause a problem to increase the eccentricity?

Have you checked the sensor and its mount?

Is your sensor mount loose or structure the sensor mount is mounted to perhaps flexing? Perhaps a foundation issue? Perhaps this is the source of the increased eccentricity measured.

Best to confirm the sensor is functioning correctly before looking at the bearings in too much depth.

in what plane and relative to what is the eccentricity? Thrust bearing or shaft?

How old is the unit? What means or method is used to control the lube oil quality? Do you filter and centrifuge the lube oil to remove water or just filter? Do you send out samples to insure proper lubricating properties of the oil? Eccentricity due to excessive wear on the journal bearings from poor oil properties can result in rotor clearances changing prior to making contact and resultant catastrophic failure. Would think that they would change more slowly than you indicated though. If it is a Kingsbury type thrust bearing, failure of an individual shoe might cause a rapid indication as you mention. What type thrust bearing is it?

Google feed water effect on steam turbine thrust?

https://www.google.com.au/search?q=turbine+feed+water+effect+on+turbine+thrust&rlz=1T4GGHP_enAU411AU411&site=webhp&tbm=isch&tbo=u&source=univ&sa=X&ved=0ahUKEwjM_OztmrnTAhUJF5QKHWKkCjsQsAQIJg&biw=1152&bih=493#spf=1

A few unanswered questions. What were the unit conditions prior to the trip; constant load for minutes/hours/days, load following, ramping up/down, sudden load shifts, changes in steam inlet/turbine outlet/condenser backpresssure conditions, etc., etc.

Since it's unlikely that you had multiple sensor failures (that's why you have multiple trip inputs into redundant protective systems), then you should be looking at what would cause the turbine shaft to unexpectedly grow laterally, or perhaps bow due to uneven temperature differentials across the shaft/casings.