Old...

A bit rusty valve.
Belonging to the high pressure feedwater pre-heater 7-B at unit EC 20.
Such a pre heater warms up the feedwater for the boiler.
This is done in a heat-exchanger with steam, extracted from the main steamturbine.
This valve can isolate te level transmitters of the pre-heater ( for instance when maintenance is necessary)

Better in LARGE....