Combined Cycle Procedures

The objective of this module is to draw attention to the need for establishing operating procedures for major equipment and auxiliary systems.Examples of operating procedures are examined, in particular those related to start-up of a typical gas turbine, HRSG and steam turbine, first in isolation and then in concert as a combined cycle unit.

After completion of this module, the participant will be able to understand the following concepts and apply them in day-to-day work activities:

• The objective of operating procedures.
• Preparation of operating procedures.
• Knowledge gained by operating personnel during preparation of operating procedures.
• Power plant general service systems.
• Procedure for priming piping systems and vessels.
• Effect of air in a fluid system.
• Procedure for priming a feedwater pump.
• Operation vents and drains on piping systems.
• Operation of steam piping systems.
• Dealing with piping expansion and condensation of steam in pipe work.
• Procedure for charging a steam pipeline.
• Control of pressure and temperature rise in piping systems.
• Generic procedure for start-up of a simple cycle gas turbine.
• Pre-start inspection.
• Gas turbine support systems.
• Start-up cranking system.
• Typical start-up curve.
• The need for purging.
• Factors affecting ignition and consequence of flame-out.
• Turbine warm-up.
• The significance of self-sustaining speed.
• Pre-synchronizing operations.
• Conditions required for synchronizing.
• Gas turbine minimum load.
• Generic procedure for a steam turbine generator start-up.
• Pre-start inspection.
• Steam turbine auxiliary systems.
• Starting up the circulating water system and priming the condenser.
• Pulling vacuum.
• Function of the turbine stop valve internal bypass.
• Partial arc steam admission to the turbine.
• Full arc steam admission to the turbine.
• Raising speed-start-up curve.
• Hot and cold start-up requirements.
• Condensate recirculation.
• Turbine supervisory monitoring.
• Expansion of turbine components with steam temperature and loading.
• The need for matching temperatures before admitting steam to the turbine.
• Turbine subsystem procedures.
• Generic procedures for start-up of a single pressure natural circulation HRSG.
• Control of heat input to the HRSG.
• Effect of gas turbine output on exhaust gas temperature.
• Function of the HRSG gas bypass.
• Function of the steam dump to the condenser via the steam bypass valve.
• HRSG water level control including the effects of shrink and swell.
• Coordination of the operation of major components during a combined cycle start-up.