Page 115 - Introduction to Marine Engineering

102 Feed systems

feed tank are present in the system to store surplus feedwater and
supply it when required. The drain tank collects the many drains in the
system such as gland steam, air ejector steam, etc. A recircuiating feed
line is provided for low load and manoeuvring operation to ensure an
adequate flow of feedwater through the air ejector and gland steam
condenser.
The system described is only typical and variations to meet particular
conditions will no doubt be found.

Auxiliary feed system

The arrangements for steam recovery from auxiliaries and ship services
may form separate open or closed feed sysems or be a part of the main
feed system.
Where, for instance, steam-driven deck auxiliaries are in use, a
separate auxiliary condenser operating at about atmospheric pressure
will condense the incoming steam (Figure 5.3). An extraction pump will
supply the condensate to an air ejector which will return the feedwater
to the main system at a point between the gland steam condenser and the
drains cooler. A recircuiating line is provided for low-load operation and
a level controller will maintain a condensate level in the condenser.
Where contamination of the feedwater may be a problem, a separate
feed system for a steam-to-steam generator can be used (Figure 5.4).
Low-pressure steam from the generator is supplied to the various
services, such as fuel oil heating, and the drains are returned to the
hotwell. Feed pumps supply the feed to a feed heater, which also acts as

Low pressure steam

Auxiliary
condenser

•*-) Extraction
*—pump
Drain to main
feed system
pumps
Figure 5.4 Steam-to-steam generator feed
Figure 5.3 Auxiliary feed system system