TROUBLESHOOTING
When troubleshooting, repairing, and maintaining
bleed air control valves, you must be aware of potential
hazards to personnel. Always follow specified electrical
Troubleshooting the fuel shutdown valves requires
safety precautions whenever you troubleshoot or repair
the same skills you need to maintain solenoids. Refer to
control valves. Since bleed air temperatures can range
chapter 5 of this TRAMAN for specific procedures for
from 100F to more than 900F, you must make sure the
troubleshooting solenoids and solenoid valves. Always
valve has cooled sufficiently before you begin working
use the appropriate technical manual when working on
on it. If possible, secure and tag out the bleed air system
any part of the gas turbine fuel system. Remember, when
before you start work on any bleed air valve.
you are called to troubleshoot the gas turbine fuel
system, make sure you get all the symptoms from the
operating personnel. Certain permissive must be met
GAS TURBINE FUEL SYSTEM
b e f o r e you can open the fuel shutdown valves.
The gas turbine fuel system regulates and
Sometimes an apparent problem will be nothing more
distributes fuel to the combustion section of the GTE to
than a misaligned system.
control gas generator speed. This system consists of a
W h e n troubleshooting and repairing the fuel
fuel pump, main fuel control, fuel shutdown valves,
shutdown valves, make sure you follow all electrical
pressurizing valve, fuel manifold, fuel nozzles, and
safety precautions. Refer to the technical manual for the
power lever angle actuator. The system also contains a
general gas turbine safety precautions to be used
p u r g e valve, variable stator vane actuators and a
whenever you are working on the engine. Remember,
compressor inlet temperature sensor.
the GTE must be secured and tagged out before you start
The GSE will be concerned mainly with the fuel
work on the fuel shutdown valves.
shutdown valves. There are two fuel shutdown valves
in the gas turbine fuel system. The fuel shutdown valves
MAIN LUBRICATING OIL SYSTEM
are pilot-valve actuated and electrically controlled.
The main lubricating oil system provides clean oil
OPERATION
at the proper temperature and pressure to the main
reduction gear (MRG). Lube oil supplied to the MRG is
The fuel shutdown valves are piped hydraulically in
used for lubrication and cooling of the reduction gear
series. They are operated in parallel by control logic at
bearings, pinions, and clutch and brake assemblies.
the control consoles during an automatic sequence.
Lube oil is used as a cooling medium in the gas turbine
They also can be operated manually at the control
synthetic lube oil coolers. The major parts of the main
consoles. Both valves must be energized to port metered
lubricating oil system are the MRG sump, service
fuel to the fuel manifold. De-energizing either valve will
pumps, a cooler, a duplex filter or strainer, an unloader
bypass the fuel back to the fuel pump inlet. Normally,
valve, and associated piping. As a GSE, you will mainly
both valves are de-energized to shut down the engine.
be concerned with the maintenance of the lube oil
The second valve acts as a backup should the first valve
service pump motors and the service pump controllers.
fail to function. The two valves may be operated
independently from the PLCC, SCU, PCS or the free
OPERATION
standing electronics enclosure (FSEE) as a maintenance
check.
The ship's main lube oil system on board gas turbine
ships is normally operated and monitored by the ECSS,
MAINTENANCE
PCS, or MCS. On the DD-963, DDG-993, and CG-47
class ships, the lube oil system controls and indicators
Y o u should check the fuel shutdown valves
are located on the PACC and the PLCC. On the FFG-7
according to PMS. Preventive maintenance of the fuel
class ships, the lube oil system controls and indicators
shutdown valves consists of running the GTE and
are located on the PCC. On the DDG-51 class ships, the
activating one of the fuel check switches on the control
lube oil system controls and indicators are located on
c o n s o l e . If the engine shuts down, the valve is
the PACC and the SCU.
satisfactory. Check the other fuel shutdown valve the
The lube oil service pumps are controlled from the
same way. If one of the valves fails to secure the GTE,
you, the GSE, will be called to investigate the system.
control consoles. The consoles provide for stopping and
You also will be called if the valves fail to give the proper
starting of the lube oil pumps. From the control
status indication on the control console.
consoles, you can place the pumps in slow (low), fast
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