Page 359 - Practical Machinery Management for Process Plants Major Process Equipment Maintenance and Repair

338 Major Process Equipment Maintenance and Repair

6. Are extraction check valves in working condition?
7. Are turbine rotor glands sealing properly?
8. Has there been any change in control system readouts?
9. Is the control system stable?
10. Will governor hold speed at no load, full steam pressure and nor-
mal exhaust pressure?
11. Are other control devices operating satisfactorily?
12. Does automatic overspeed trip function at correct speed?

Off-Line inspection

1. Without major disassembly

Determine “bump-to-bump” thrust clearances.
Alignment check-See chapter 5, Volume 3.
Boroscope (endoscope) inspection.
Inspection of casing keys and base plates.
piping anchors--See chapter 3.
Determine radial bearing clearance.
2. Major disassembly. Table 8-3 shows all necessary inspection opera-
tions following major disassembly.

Documentation

Written documentation and photographs of all inspection results are of
the utmost importance.
Subsequent inspection schedules should be based on what is found at
the last inspection, the “case history,” and the operating log. Periodic
checks of the lubricating system, control system, throttle valve, and auto-
matic features are important. As we saw, test data at some fixed ref-
erence, load on steam flow, and intermediate stage steam pressures
checked back to the early operation of the turbine may detect the pres-
ence and extent of blade deposits or mechanical damage. Similarly, vari-
ations in the stage enthalpy measured by steam pressure and temperatures
in the superheat zone may detect any important change in internal stage
efficiency. Table 8-4 suggests how often we should do all this, but our read-
ers are encouraged to establish these frequencies for their own installation.