Steam turbine alignment
Steam turbine alignment
(OP)
Hi everyone,
In a coupled steam turbine alternator arrangement (3000RPM, 10MVAe) should the DE bearings be slightly lower than the two NDE bearings? That is should both the turbine shaft and alternator shaft be slighly angled downward towards one another at the coupling? If this is so why is it done?
Many thanks to all in advance who humor a somewhat mystified electrical person.
In a coupled steam turbine alternator arrangement (3000RPM, 10MVAe) should the DE bearings be slightly lower than the two NDE bearings? That is should both the turbine shaft and alternator shaft be slighly angled downward towards one another at the coupling? If this is so why is it done?
Many thanks to all in advance who humor a somewhat mystified electrical person.





RE: Steam turbine alignment
I do Know other companys do not use the curve for setting there bearings, maybe they design the coupling shafts more felixable.
RE: Steam turbine alignment
1) shows two uncoupled rotors with the bearings in line. the coupling face is open on the top.
2) shows the coupling bolted together with bearings in line. the deflection to close the coupling will be a cyclic stress when spinning.
3) to make the coupling face fair, the out board bearings are raised. when the coupling is bolted together with the bearings in a curve, the cyclic stress at the coupling is reduced
some other related comments
The generator bearings are set to have its coupling face vertical. The turbine bearings may require addition "cold" off set to achieve proper alignment at rated. there is usually a compromise between fair coupling and magnitude of coupled deflection.
RE: Steam turbine alignment
Many thanks for your replies, I now understand this. I tried to respond to you with a note of thanks after your first reply (I agree entirely a white board makes this much easier). I could not work out how to get an email to you so I hope you get read this.
Many thanks once again
RE: Steam turbine alignment
While turbine bearing loading and alignment is not my expertise, I can't see where a 10MW unit would have enough rotor sag to require to get fair coupling alignment. Do you know how much are your bearings offset? I would only expect about 0.0002 X span, ie a 100" span between bearings might need about 0.020" offset.