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Places in a power station where drying is recommended
during shut down include:
Generator- it is important to keep the windings
dry to prevent corrosion and ensure a shorter starting
time. Dry air can also supplement generator heaters.
Condenser - must be kept dry after flushing to
allow recoating of water boxes and tube plates.
Re-heater - tubes are thinner than super heater
tubes and more susceptible to corrosion. Inter-granular
attacks on austenic stainless steel can be minimised
using dry air.
Feed & Condensate pipes - important to eliminate
internal corrosion on pipes as oxides can contaminate
feed water.
Boiler- surface temperatures of
fireside boiler tubing drop below the dew-point and
form condensate. The condensate reacts with sulphurous
parts of the ash and acid deposits and hydrolyses, forming
a highly acidic solution. The end result is rapid, localized
attack of the metal surface.
Reactor vessel - Where access is required, dry
air is required to purge out CO2, eliminate corrosion
and to dry the graphite prior to refilling with CO2.
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