1. During turbine bypass operation, the valve is opened to allow cooling steam to flow thru the turbine. In this mode of operation desuperheated steam from bypass flows back through the HP section of the turbine to prevent overheating.

2. When the turbine trips, or as a result of load rejection, the steam in the turbine HP section becomes bottled up and, due to windage losses, may overheat that section. To prevent overheating cold reheat steam flows back through the HP turbine.

3. Advantages in maintenance, hard packing structure, no need gland packing.

4. Reinforced sealing system between body and bonnet by hot bolting connection.

5. Operated by hydraulic actuator.