inlet louvers and the demister panels. The inlet
SILENCERS. --The main engine intake duct
louvers are arranged in sections. They are located
silencers are located about halfway clown the duct.
in the sides of the high hat assembly. The design
The silencers are vertical vane assemblies
and arrangement of the louvers aresuch that they
constructed of sound-deadening material. The
will shed sea spray. The louvers are electrically
intake ducts are encased in perforated stainless
h e a t e d to prevent icing. These heaters
steel sheet. The vane assemblies are arranged in
type and are located on the back of the louver
modules which are removable to aid in the
surface. The heaters are controlled from the
removal of the GTEs through the intake duct.
engine control consoles. The demisters are the
two-stage, mesh-pad type and are mounted
ANTI-ICING SYSTEM.--This system pre-
vertically behind the louvers. Water, separated
vents the formation of ice in the intake duct.
from the inlet air as it passes through the
High-temperature bleed air from the GTEs is
piped to a manifold. This manifold is located
demisters, is collected in scuppers and drained
inside the duct between the cooling air extraction
overboard. The demisters will remove 70 percent
of the particles that are 1.7 to 5 microns in size
port and the silencers. From the manifold the
bleed air is discharged into the inlet airstream. The
and 90 percent of the particles that are 5 microns
bleed air is mixed with the inlet air, raising the
and larger.
temperature enough to prevent the formation of
BLOW-IN DOORS.--The blow-in doors are
ice. When enabled from the PAMCE or the
PLOE, an electromechanical control system
located just below the inlet louver Then
regulates bleed air flow to maintain the inlet air
function is to bypass the moisture seperation
temperature at about 38F. This prevents the
system. They provide an unrestricted inlet airflow
formation of ice. A temperature sensor in the
to the engines if the moisture separation system
stack provides an ANTI-ICING INSUFFICIENT
becomes blocked. They are designed to open by
signal. This alarm activates when the anti-icing
solenoid-operated latch mechanisms, and will
system has been enabled and the temperature
open if the inlet airflow becomes too restricted
drops below 36F.
for normal engine operation.
On the DD-class ships, a controller
COOLING AIR DUCT.--Main engine cooling
is located in each engine room to provide for
air is extracted from the main intake duct. It is
manual or automatic operation of the doors. This
taken at a point between the blow-in doors and
is done by a selector switch and a push button on
the main duct silencers. It is then ducted to the
the controller door. On the CG-class ship this
engine enclosure. The cooling air duct contains
controller is in the helo hangar. The push button
a silencer and a cooling air fan. The cooling
on the CG-class is located on the high hat
system will be discussed in more depth later in this
assembly. In manual operation, you can only open
chapter.
the doors by depressing the push button. In
automatic operation the doors open by operation
ENGINE REMOVAL SYSTEM.--Sometimes
of a pressure switch. The switch operates on low
a main propulsion GTE must be removed from
duct pressure. This pressure switch also provides
the ship for maintenance/overhaul. At the time
a DUCT PRESSURE LOW signal to propulsion
of engine removal, a set of channel-shaped
auxiliary machinery control equipment (PAMCE)
maintenance rails is installed in the engine
and propulsion local control equipment (PLOE).
enclosure. These are put adjacent to each side of
The pressure switch operates when duct pressure
the engine. A set of rollers, which fit into the
falls below 8 inches of water. If the doors open,
rails, is attached to each side of the engine. The
the doors must be manually reset closed.
removable maintenance rails extend into the
enclosure inlet plenum. They then turn 90 degrees,
from horizontal to vertical attitude. They mate
Ducting
with permanently installed rails that extend up
the intake duct. In the FFG-class ship, the uptake
See figure 2-12 as we discuss the ducting. It
rails must be installed each time the engine is
allows the air to travel from the high hat assembly
removed. The engine is removed through the
intake duct. In the inlet plenum, three sets of
of the ducting include the silencers, the anti-icing
maintenance rails interface with three sets of
piping, the cooling air duct, and the engine
permanently installed rails in the ship's intake
removal system.
2-12