Page 119 - Introduction to Marine Engineering

106 Feed systems

Nozzle holder

nd stage steam nozzle

ivision plate

2nd stage condenser
Condenser tubes

Stay rod
Distance piece

I Air
I Cooling water
Water box baffles
Expanded tubes
Cooling water Cooling water
inlet outlet
Figure 5.7 Air ejector

steam and gases are mostly condensed. The condensed vapours and
steam are returned to the main condenser via a drain and the remaining
air and gases pass to the second stage where the process is repeated. Any
remaining air and gases are released to the atmosphere via a
vacuum-retaining valve. The feed water is circulated through U-tubes in
each of the two stages. A pair of ejectors are fitted to each stage,
although only one of each is required for satisfactory operation of the
unit.

Heat exchangers
The gland steam condenser, drains cooler and low-pressure feed heater
are all heat exchangers of the shell and tube type. Each is used in some
particular way to recover heat from exhaust steam by heating the
feedwater which is circulated through the units.