There is 2MW backpressure steam turbine that I worked with before.

Previous major inspection during overhaul, revealed turbine thrust bearing pads inactive side experienced significant thrust load. While active side pads were fine.

This was not a surprise to me. Since the thrust probes (2 of them) keep showing us the rotor axial movement was loaded to inactive side. Both probes shown the same data.

During the major inspection, we checked the thrust pads at active side, still like new appearance, as if that very very minimum load or almost nothing.

However, when we looked at inactive side thrust pads, oil lacquering was observed on all pads of inactive side. To me it can be said the load was significantly high and heat generated can be said on high side (but we don't have PT100 installed on this package). So I can't tell you what were the temperatures...

Now, it started again. Same symptom, proximity probes (axial) showing the same reading after the major overhaul.

After 24 months,the axial probes read high-high trip. Machine shutdown and same findings. inactive pads experienced same conditions.

Why this rotor move to inactive side?
What is/are can be checked to support/explain this?

 

was the coating of "oil lacquering on the inactive thrust pad's face?
did you measure any wear or see any smearing of white metal on the inactive thrust pad?

was the thrust bearing pads to runner clearances (float) as per drawing?

what is thrust runners ID and OD and the float?

did you verify calibration polarity of the axial thrust probes by observing during the bumping of the rotor to determine float clearance?

does this turbine design have "balancing pistons"?

was there any major erosion in the steam path that reduced stage areas?

 

Hi Amin,

some questions, further to JFB's questions:

1. has the steam turbine been living with this problem from its 1st start, or did the phenomenon start lately?

2. is the steam turbine operated with inlet and exhaust steam pressure \ temperature as per design, or are you operating at a different operating point resulting in an unbalance of axial forces wrt original design?

3. is the steam turbine operated at a steady load or is it following a process with is continuously going up and down and thus the axial thrust on the steam turbine continuously changing?