Page 113 - Introduction to Marine Engineering
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100 Feed systems
Auxiliary
feed
pump
Overflow
Figure 5.1 Open feed system
contaminated feed or drains. The feedwater is then passed through
charcoal or cloth filters to complete the cleaning process. Any overflow
from the hotwell passes to the feedwater tank which provides additional
feedwater to the system when required. The hotwell provides feedwater
to the main and auxiliary feed pump suctions. A feed heater may be
fitted into the main feed line. This heater may be of the surface type,
providing only heating, or may be of the direct contact type which will
de-aerate in addition. De-aeration is the removal of oxygen in feedwater
which can cause corrosion problems in the boiler. A feed regulator will
control the feedwater input to the boiler and maintain the correct water
level in the drum.
The system described above can only be said to be typical and
numerous variations will no doubt be found, depending upon particular
plant requirements.
Closed feed system
A closed feed system for a high pressure watertube boiler supplying a
main propulsion steam turbine is shown in Figure 5.2.
