Page 358 - Practical Machinery Management for Process Plants Major Process Equipment Maintenance and Repair

Steam Turbines and Turboexpanders 337

On-Line Monitoring Results

Measurement of steam consumption. Comparison with the result of a pre-
vious measurement makes it possible to find out if there was a change in
efficiency.

Determination of internal efficiency. If a measurement of steam consump-
tion is too costly, measure inlet, intermediate and final steam pressures
and temperatures.

Measurement of stage pressures. Measure pressures as a function of
steam flow and compare with those obtained with a “clean” machine.
This will give an indication of blade deposits or deformation.

Vibration monitoring. Review vibration history. Review bearing and cas-
ing vibration frequency spectra. Perform vibration signature analysis, di-
agnosis and prognosi~.~

Review shaft positlon history.

Revlew bearing pressure and temperature readings. A reduction in inlet
pressures may indicate increased bearing clearances. A rise in bearing
metal temperature may indicate a change in bearing geometry.

Obtain answers to these questions:

1. Is there oil leakage?
In the piping?
At bearing oil seals?
At hydraulic lines?

2. Do the emergency and auxiliary oil pumps start when the oil pres-
sure fails?
3. Is there steam leakage at

Joints?
Valve stems?

4. Do throttle and governor valves close promptly when tripped?
5. Does the throttle valve stop the unit when tripped?