Why are extraction valves fitted on some LP and HP turbines?

Extraction valves are utilized in some low-pressure (LP) and high-pressure (HP) turbines primarily to increase the efficiency of the steam cycle. By allowing a portion of the steam to be extracted from the turbine at various points in the process, these valves help to utilize the steam energy more effectively.

This method of extraction can be particularly beneficial when the extracted steam is used in auxiliary systems, such as heating processes or feedwater heating. By using steam from the turbine, the overall energy demands of the system are reduced, resulting in an increase in thermal efficiency. This optimization allows turbines to operate more effectively, ultimately decreasing fuel consumption and enhancing the overall efficiency of the steam cycle.

Moreover, this extraction of steam can lead to better control of the turbine operation and accommodate varying load demands, further contributing to efficiency gains within thermal power plants.