Page 75 - Introduction to Marine Engineering

62 Steam turbines and gearing

content. The steam inlet nozzles are arranged in several groups with all
but the main group having control valves (Figure 3.10). In this way the
power produced by the turbine can be varied, depending upon how
many nozzle control valves are opened. Both impulse and reaction
turbines have steam inlet nozzles.

Uncontrolled
nozzles

Steam inn Scrap section A A
from
manoevurin;
valve
Section looking on nozzle plates
Figure 3.10 Nozzle control

Drains
During warming through operations or when manoeuvring, steam will
condense and collect in various places within the turbine and its
pipelines. A system of drains must be provided to clear this water away
to avoid its being carried over into the blades, which may do damage.
Localised cooling or distortion due to uneven heating could also be
caused.
Modern installations now have automatic drain valves which open
when warming through or manoeuvring and close when running at
normal speed.

Bearings

Turbine bearings are steel backed, white-metal lined and supported in
adjustable housings to allow alignment changes if required. Thrust