Valves

Used for supply of cooling steam during startup or for heating of the steamturbine before startup.
Sounds a bit confusing, I know.
But: as the gasturbine speeds up to 3000 rpm the steamturbine which is on the same shaft has to be cooled during that time otherwise the ventilation losses inside cause it to become overheated.
After the unit is connected to the grid we put the steamturbine into service.