13.5.1 First-stage reheat
The bled-steam to each reheater is conveniently sup¬plied from a bleed-off (usually the first) from one of the flows of the HP turbine.
Since the bled-steam is wet, the supply lines usually incorporate some form of water separation device, close to the HP turbine: to safeguard the HP turbine from any possible ingress of large slugs of this water, non-return valves are normally included. On the most recent machines, these non-return valves are often power-assisted and close in the event of a turbine trip or a load rejection. They may also be triggered to close from a signal initiated by an extra high water level in the associated reheater drains tank. Bled-steam lines to the reheater are rarely fitted with safety valves, but motor-operated isolating valves are always included which close if the water in the reheater drains tank rises to the extra high water level.