Governor problems.

Accumulator problems.

Extraction problems.

Surge control problems.

Compressor surge.

Bad speed pickup

Fluctuating compressor load

Fluctuating back pressure on the exhaust header

Unloaded compressor

It would help to know what kind of compressor and what kind of turbine (back pressure, extraction, or condensing) in what kind of service (recycle? refrig?).

The fluctuating speed means is it hunting? or it settles down after the spikes?

centrifugal steam turbine that uses 400psig saturated steam to drive a centrifugal single stage hi speed compressor. the compressor deliver combustion air. The problem is observed even when the turbine is uncoupled.

the fluctating dosn't settel. the flucating is btween 3450rpm and 3650rpm.

is the presence of condensate is a reason?how can we be sure about it?

is defects in steam traps (in the outlet of condensate lines ) is a rason in this problem?

i noticed som steam is leaking throgh the flange of the cover of the rotor(near the outbord carbon rings)

Why is this level of speed fluctuation a significant problem?

because it cause the turbine to trip on overspeed.

I doubt it is condensate, but it might be. Is this turbine way out on the end of the 400 lb header?

I would start with the governor, and the accumulator in the governor hydraulic system. It is probably a hysteresis issue.