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Handbook of Turbomachinery Second Edition Revised - Ventech!

Handbook of Turbomachinery Second Edition Revised - Ventech!

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the turbine against overspeed. This valve is usually the last valve to receive<br />

the signal to close on overspeed, since when this valve closes, a complete<br />

restart will be required.<br />

Control Valves<br />

The control valve, which may also be called a governor valve or steam chest<br />

valve, provides for load control and is a variable lift type <strong>of</strong> valve. The<br />

operating sequence <strong>of</strong> the valve is designed to include balanced steam force<br />

loading on the turbine, the avoidance <strong>of</strong> double stock loading in the nozzle<br />

area, and an efficient heat rate at various loads.<br />

Steam is typically fed through several control valves and an equal<br />

number <strong>of</strong> inlet pipes to the double control stage as shown in Fig. 67. Four<br />

Figure 67 Steam turbine main steam nozzle and control stage inlet configuration.<br />

Copyright © 2003 Marcel Dekker, Inc.

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