Gents,

We have a few Mitsuvishi Heavy Ind. Steam turbines on site one of which one has started giving indications of a hot bearing on the steam inlet side of the turbine. I am after your experiences of other indications there might be that the bearing is actually having problems.

The Steam Turbine in question is two stage, impulse bladed driven with HP steam letting down to MP. Normal RPM is 5025. 1450kw.
Model number: CHL-220ARS

Other than the temperature gauge reading way off the scale I cant really find any other indications of problems with the bearing on the steam inlet side of the turbine.
Temperature readings from the oil inlet and drain ports near the bearing housing are nearly identical on both ends of the turbine. (48DegC supply & 60-62DegC drain) which also happens to be a lower temperature differential than readings from the same locations on its identical sister turbine (42DegC supply & 57-58DegC drain)
Radial vibration levels are low and stable at both bearings @ 12µm.
I have sent off a lube oil sample this afternoon which should indicate if we have increasing levels of wear metals.

Op's logs for the last couple of years indicate a fairly steady temperature at this bearing of about 47-52DegC. Now that it is reading around 120DegC+ I would have expected to see more indications of something going wrong. Possibly including elevated temperatures of lube oil draining away from the affected bearing. Although this particular drain line is seeing oil from both the radial and thrust bearings which would have the effect of buffering the hot oil.

Can anyone tell me if we should be seeing other indications such as warmer oil draining away from the housing or elevated vibrations?

The temperature gauge is a remote mounted expanding gas type, and the instrument tech's assure me it is reading correctly.
Original Post
increase from normal 58 deg c to 120++ deg C without any change in oil return temperature and radial/axial vibration indicates likelihood of non-genuine temp readout. you might want to get bearing casing skin temperature to further conclude. at normal, it should be below {ambient + 40 deg C}.

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