Steam Power And Co-Generation

The objective of this seventh module is to present and discuss the major features of steam turbine operation, protection and control. Particular attention is paid to the effect of changes in load or steam temperature on mechanical operation of the turbine, and consequent need for supervisory instrumentation and automatic protection devices.

After completion of this module the participant should be able to understand the following concepts and apply them in day-to-day operation:

• Operation of the turbine hydraulic control system.
• Governor operation.
• The function of turbine control valves and stop valves.
• The function of reheat intercept valves and reheat stop valves.
• Location of steam chest(s).
• Operation of drains on steam piping, stop valve, steam chest, turbine shell.
• The need for turning gear.
• Start-up procedure.
• Limitations to rate of raising speed.
• Critical speeds.
• Full-arc and partial arc steam admission.
• Matching steam temperature to turbine metal temperature.
• Turbine steam by-pass.
• Minimum load requirements.
• Effects of turbine expansion.
• Supervisory equipment: eccentricity, vibration, differential expansion, metal temperature, shaft position, pedestal position.
• Prevention of water ingress to the turbine.
• Function of protection devices, overspeed, low vacuum, thrust bearing failure, loss of lube oil pressure, boiler-generator-turbine intertripping, steam pressure deloader.
• Turbine trip function.
• On-load testing of protective devices.
• Exercising stop valves.
• Control room layout.
• Significant monitoring points.