Page 262 - Steam Turbines Design, Applications, and Rerating

Reaction vs. Impulse Type Steam Turbines 241

boiler stop valve may then be opened and the turbine brought up to
speed. The turbine may also be shut down entirely and started up by
normal procedure.
During the entire procedure, the unit should be carefully watched for
signs of rubbing or other distress.
To accomplish full-speed wash (Fig. 12.18), the operator would slowly
open the feedwater valve to the atomizer chambers. This valve would
then be adjusted to supply water to the atomizer chamber in quantities
to reduce the steam temperature at the recommended rate until 10 to
15°F (6 to 9°C) superheat is reached at the turbine inlet. During the
washing cycle the exhaust steam would be discharged to the sewer.
The washing may be continued until tests of either the condensate or
exhaust steam indicate that no further deposits are being dissolved.
This is neatly illustrated in Fig. 12.19 and 12.20.
The same precautions concerning the trip-throttle valve and piping
between boiler and turbine apply.
The turbine may be restored to normal steam conditions by increas-
ing the steam temperature at the previously recommended rate (25°F
or 14°C increase per 15 min) by slowly closing the feedwater valve to
the atomizer chamber.
During the entire procedure, the unit should be carefully watched for
signs of rubbing or other distress. Instrumentation such as vibration
probes and thrust temperature detectors are invaluable during this
period.