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Steam Plant
System Outline:
Feed Water System:
The steam plant uses a closed feed system with feed collecting in the
enclosed feed tank. In order to increase the steam cycle efficiency and reduce
oxygen in the feed water, the enclosed feed tank has a steam heating coil to
maintain the temperature in the tank at 90°C. This feed temperature should be maintained for both
auxiliary boiler operation and exhaust gas economizer operation. Vapor and air
are removed from the enclosed feed tank, to vent condenser by an exhaust fan.
The steam plant has two feed water pumps which pump feed from the
enclosed feed tank to the auxiliary boiler and economizer. Normally feed is supplied to the auxiliary
boiler from the main feed line and feed regulator. The auxiliary feed to the
boiler is used as an alternative feed supply in an emergency, or filling the
boiler for a wet lay up.
Normally the feed is supplied to the economizer through the main feed
line, and is heated in the pre-heater section of the economizer. All economizer
feed should pass through the pre-heater.
At the outlet of the pre-heater the feed water is separated into two
directions. Part of the feed water passes through the low pressure evaporator
flow control valve and is used to generate low pressure (4 kg/cm2)
steam in the L.P evaporator. The remainder of the feed passes through the feed
regulator into the high pressure steam separator.
Condensate System:
The condensate system consists of the turbo-alternator condenser, which
is cooled with sea water by one of the turbo-alternator condenser cooling sea
water pumps. The two pumps, pump condensate through the air ejector gland
condenser, the vent condenser and its by-pass orifice. The condensate system
must be operational at all times when feed system is in use.
If the turbo alternator is in operation the air ejector must be in use
to maintain a vacuum at the condenser. If the turbo-alternator is not is not in
use the condenser can be used as an atmospheric condenser and the steam side of
the air ejector need not be started.
Low Pressure Steam System (4 Kg/cm2):
When the auxiliary boiler is in operation the 4K steam is reduced from
7K steam through a reducing valve. When the exhaust gas economizer is in
operation the 4K steam is produced in the L.P evaporator section of the
economizer and the reducing valve will shut automatically. If the low pressure steam pressure falls to
3.9 Kg/cm2 the reducing valve open to make up pressure. If pressure
in the low pressure steam line rises to 4.1 Kg/cm2, the 4 Kg/cm2
dump valve will open and relieve pressure to turbo-alternator condenser. 4K
steam is used for tank heating, purifiers and main engine heaters, and steam
tracing service.
7 Kg/cm2 Steam System:
7K Steam is produced in the auxiliary boiler; it is used for soot-blowing
(auxiliary boiler) and for reducing to 4K steam service when the economizer is
not operational.
9.5 Kg/cm2 Steam System:
This high pressure steam is generated in the economizer high pressure
evaporator and is stored in the high pressure steam separator as saturated
steam. This saturated steam is used for economizer soot-blowing, air ejector
steam and saturated steam supply to the super heater. When the economizer is in
operation the excess steam in the high pressure steam system is relieved to the
turbo alternator condenser through the H.P dump valve. This is set at 9.5 Kg/cm2
.
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