Hi,

I try to understand what's the purpose of IPL (inlet pressure limiter) on steam turbine

GE documentations states that it avoid water induction through the steam turbine,
i don't understand how steam can condensate on sudden pressure drop, or low load
i don't understand either why it's better to keep admission pressure steady and reduce the opening of control valve:
to my point of view, closing the control valve to much, leads to steam expansion on the turbine side, and therefore cool it or lead to saturated state

(sorry for my broken english)

Does someone know how it works ?

 

If you have cold steam at low pressure, the steam can condense on a sudden pressure drop. This is usual in effect during startup when you are heating up the steam.
You need to have at least 100 degF of superheat to keep the steam from condensing while going through all stages of the steam turbine. As the steam runs through the steam turbine, it drops in pressure and temperature and therefore can create droplets that cause damage. This is another reason that there are limits to superheat vs shell temperature.
Hope this helps!