Once the combustion process has occurred, the water has boiled and the steam has been generated, the next requirement is to ensure that the temperature of the steam that is delivered to the turbine or heat load is maintained at the correct value. In the next chapter we shall look at the control and instrumentation systems that are employed for this purpose.

Chapter Contents:

• Part 1: controls
• 6.1 Drum level and feedwater control
• 6.2 One, two, three and four-element control
• 6.2.1 Two-element feedwater control
• 6.2.2 Three-element feedwater control
• 6.2.3 Four-element level control
• 6.3 Feedwater valve control
• 6.4 Storage vessel-level control in a once-through boiler
• 6.5 Once-through super critical additional systems
• 6.5.1 Sub-cooling line
• 6.5.2 Economiser vent line
• 6.6 Basic enthalpy control
• 6.6.1 Enthalpy control process considerations
• 6.6.2 Enthalpy control logic considerations
• 6.7 Deaerator control
• 6.7.1 Steam pressure control
• 6.7.2 Level control
• 6.7.2.1 Spill control
• 6.7.3 Integrated-level control
• Part 2: feedwater instrumentation and control mechanisms
• 6.8 Measuring and displaying the drum level, steam and feed flows
• 6.8.1 Some words of caution
• 6.8.2 Using an external water column
• 6.8.3 Statutory requirements
• 6.8.4 Discrepancies between drum-level indications
• 6.8.5 Drum-level gauges
• 6.9 Feed-flow measurement
• 6.10 Steam flow measurement
• 6.11 The mechanisms used for feedwater control
• 6.11.1 Valves
• 6.11.2 Quick opening
• 6.11.3 Linear
• 6.11.4 Equal percentage
• 6.11.5 The valve sizing coefficient
• 6.11.6 Fail-safe operation
• 6.11.7 Selecting the valve size
• 6.11.8 Specialised valve trims
• 6.12 Pumps
• 6.12.1 Variable-speed pumps
• 6.12.2 Pump controls
• 6.12.3 Boiler circulation pumps
• 6.13 Summary

Inspec keywords: combustion; power generation control; steam power stations; boilers; instrumentation

Other keywords: heat load; instrumentation systems; combustion process; feedwater control; turbine; steam generation

Subjects: Control of electric power systems; Steam power stations and plants; Measurement equipment and instrumentation systems