ship's bleed air system. The ISOLATE push button,
continuously at both the PACC and the PLCC, but
located on the PACC, will illuminate when the valve is
control is available only at one of the consoles at a time.
closed and the No. 3 GTGS has been isolated. On the
At the PACC, lube oil control consists of either manual
CC-47 class ships, the GTGS solenoid-operated bleed
or automatic control of the two lube oil service pumps.
air valves can be controlled from a bleed air valve
The function of these pumps is to provide additional oil
control panel next to the EPCC in the CCS.
to the lube oil pump that is attached to the main reduction
gear.
Now let's examine the bleed air system in terms of
its four distinct subsystems:
For the operator to be able to enable the pump
controls at the PACC, the local control switches on the
1. Starter air
pumps must be in the REMOTE position. Then, the
2. Masker air
operator can obtain individual manual control of each
of the two pumps by using the three push-button
3. Prairie air
indicators on the PACC. Setting the pump mode
4. Anti-icing air
auto/manual logic switch to MANUAL allows the
operator to control pump speed. When the operator
We will briefly discuss each of these subsystems in the
depresses the push-button indicator at the PACC, the
following paragraphs.
associated command goes to the PLCC circuitry and
Starter Air System.-- The starter air system has
then to the pump motor controller. Setting the pump
three operating modes available at the PACC: (1)
mode switch to either the A LEAD or B LEAD position
normal, (2) emergency, and (3) motor. Let's first look at
sets up the automatic control circuits, allowing the
the normal start air mode.
operator to select a lead pump and a standby pump. From
Normal start air is used during a normal start
this point, pump control becomes a function of header
sequence. The start air for the GTM is controlled by the
pressure and time.
motor air regulator valve. This valve is controllable at
Lube oil control can be transferred from the PLCC
the PACC and can provide either one of two functions:
to the PACC by depressing the control transfer switch
a valve-opened, nonregulated (start) position or a
at the PLCC. Then, the control commands can go from
valve-opened, regulated at 22 psi (motoring) position.
the PACC over the serial data bus to the PLCC. The
In the GTM, the last valve in the start air flow is the
PLCC pump control circuitry then initiates the proper
starter air valve. The operator at the PACC can control
signals to the pump motor controllers.
this valve either manually or automatically as long as
GTM control has been transferred to the PACC. The last
Air System
valve in the GTGS start air flow is through one of the
There are two main air systems associated with the
two starter air valves, either high pressure or low
GTMs and the gas turbine generator sets (GTGSs): (1)
pressure, depending on which is selected. Once the
the bleed air system, and (2) the high-pressure air
valve is selected, then the start air control is maintained
system. These two air systems are interconnected by
by the GTGS's system throughout the start sequence.
piping and valves. Both systems are monitored and
The operator at the PACC can start the emergency
controlled at the PACC. Control for both systems is
start air by depressing the EMERGENCY push button.
available continuously and simultaneously at both the
This action allows air from the high-pressure storage
PACC and the PLCC. Let's now look at each of these
flasks to be made available for GTM starts. The
systems separately, starting with the bleed air system.
exception to this is in the case of the DDG-993 class
BLEED AIR SYSTEM.-- There is a separate bleed
ships, which do not have a high-pressure/low-pressure
(HP/LP) air reducing station for GTM starting. The
air line to each GTM. Located in each of these lines is a
motor-operated bleed air valve. The position of the valve
high-pressure air is reduced and enters the GTM start air
system upstream of the motor air regulator valve.
can be controlled manually at the PACC as long as GTM
control is transferred to the PACC. The valve can also
Masker Air System.-- The operator can align the
be controlled automatically by the start/stop sequence
masker air system from the PACC. The masker air
logic circuits. The status indicator lights on the PACC
system causes the valves of the start air system to line
will show the position of each bleed air valve.
up to either one of two possible positions, depending
upon whether the masker air is ON or OFF and whether
The GTGS No. 3 has a bleed air isolate valve that
the air system is in the automatic control mode. With the
can isolate the GTGs No. 3 bleed air from the rest of the
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