normal operation, and when you are troubleshooting for
pressure demands or stop in the event of a large leak in
the system. All of these functions are controlled by
system pressure problems.
means of cooperating system components, consisting of
In any inspection or test of the FO system, your most
a timing circuit card, pressure transducer, and
important tools are (1) your knowledge of the system
detroit-type pressure switch. In most cases if the timing
and its normal operating characteristics, and (2) your
is off, you will have to replace the circuit card. (This is
understanding and ability to detect the signs and
because you cannot adjust the circuit card.) If the
symptoms of abnormal operation. Once you detect the
transducer or detroit switch should activate the pressure
problem and trace the cause of abnormal operation, your
alarms or pump control signals at the wrong pressure,
next logical step is to remove and replace the faulty
however, you can adjust these components for proper
operation.
components.
Relief Valves
REMOVAL AND REPLACEMENT
OF COMPONENTS
All relief valves in a ship's FO service system are
usually inspected and tested annually. These valves are
Normally, you will need to remove and replace
normally removed and carried to an intermediate
components because of component failure. At times,
maintenance activity (IMA) for bench testing. You can,
however, you may be required to perform a partial or
however, test these valves while they are installed in the
complete removal of a component to satisfy the
system and you can inspect them every time the system
guidelines of a required maintenance procedure. To
is placed in operation. Remember, most of the low
perform an inspection of a FO flexible coupling, for
pressure problems in a FO service system can usually
be traced to a faulty pressure relief or unloader valve.
example, you will need to perform a partial disassembly
or removal of the coupling components to complete the
Prefilter
P Alarm Operation
task. If you must test a FO pump relief valve, however,
you must completely remove the relief valve from the
Normally, you will test the alarms associated with
system so it can be properly tested. The removal and
the FO prefilter during system start-up, propulsion plant
replacement procedures you will perform will be based
inspections, and filter element changeout. Your
on the specific inspections, tests, troubleshooting, and
inspection procedure, however, will be limited to a lamp
preventive and corrective maintenance required for the
status check.
FO system of your ship.
Separator/Coalescer P Alarms and
Changeover Valve Operation
MAIN REDUCTION GEAR LUBE OIL
SERVICE SYSTEM
Depending on the class of ship, these two tests will
On any gas turbine-powered ship, the primary
likely be performed either according to the PMS or
function of the main reduction gear (MRG) lube oil (LO)
according to the authorized procedures for a particular
ship. The tests you will be required to perform will
service system is to supply oil to the MRG and its
depend on the design of the FO equipment and system
accessories. In the majority of the gas turbine ship
on your ship. Although FO equipment and systems may
classes, there are three LO service pumpstwo are
differ among gas turbine-powered ships, the testing
electric and one is either gear or air driven for each
procedures and alarm set points are almost identical.
MRG. In the case of the LCACs, however, each gearbox
These tests are usually performed as required or for a
has its own pump or pumps. No matter how big or
propulsion plant inspection.
complex the MRG service system maybe on your ship,
you will need to know the primary components and
Unloader Valve
functions of this system and what your responsibilities
as a GSM will be to maintain them. In maintaining any
The unloader valve does not have a specific test or
system, your most important tool will be your thorough
inspection. The only maintenance that you will normally
knowledge of normal operational characteristics.
perform will coincide with the valve maintenance
Because of this, let's briefly discuss these systems and
program (lubrication). Normally, you will inspect the
operation of this valve during system start-up and
how they work under normal operating conditions.
