Negative axial shifting in steam turbine

Any stresses from generator side? may be the thermal expansion is not compensated for.

In active pads are anyway much lower rated and hence will get damaged if subjected to high load.

The turbine reaction thrusts are not likely to be on this direction. Other parameters (vibration etc OK?)

One of the best way to find the source is the cut-off study

When the problem has started ?

What was done just prior to that (say within 15 days or so) and that includes the immediate neighbours too - eg BFP, Bolier etc.

Check what could have reversed the thrust direction.

(If it is a brand new then any way your supplier is responsible, else too you can contact him-- and keep us informed so that we can update our database)

Hi,

I do not know this turbine but I am familiar with LMZ 215 MW turbine. It is 3 rotor turbine.The steam flow is design in a way to compensate axial force in each part.

If you have the inactive pads at axial radial bearing, demaged they are overloaded. What is overload reason? It is hard to asses as we do not know what has been changed in turbine. Steam path at each part is the orginal one? Maybe some changes have taken place during ovehaul? Do the inactive pads have the right dimension? Is the cold state axial shift in both direction ok?

I put the LMZ 215 MW turbine picture as I think that 165 MW turbine is similar. You wrote it is double cylinder turbine, so no LP rotor for sure but the rest should be almost the same.Let us know more info, than we can give you any tips

Dear All,

thanks for all these informations and showing ur interest.

When we opened the HP (HP & IP), it is found that the shroud at the 3rd stage is severly damaged and also some blades. There are some dent marks on shrouds from 4th to 12th stage of HP. Though there is no solid reason why this happened but presence of some foreign materials from beginning is being expected.

Then LP casing is also opened for inspection and it is normal.

yet to fiind out the reason for axial shifting .

Thanks.

I would like to share some thoughts. I think that would be good idea to check the possibility of axial termal expansion. Maybe there is a problem with bearing pedestal movement. I know that one of modernization idea during turbines major outages is to install the Deva plates between the foundation and bearing pedestal. These plates have very low friction coefficient, so it is easier to get right termal elongation during the turbine operation.

If there is enough time please take into account to disassembly of rotors - the HP rotor's shrounds have to repaired, so parallel to this, the foundation and bearing pedestal can be inspected. Installation of Deva plates is easy and does not consume large amount of hours.