Filter Assemblies
NORMAL OPERATIONS
On the CG-47, DD-963, and DDG-993 class ships,
In the case of most gas turbine ships, the LO
the filter assembly consists of a single wire mesh strainer
system supplies oil to the MRG through one of the two
basket in each tower. On the DDG-51 and FFG-7 class
electric pumps. The electric pumps supply oil to the
ships, the filter assembly consists of multiple filter
system when the propulsion shaft is stopped and
elements in each tower. After the oil leaves the filter
augment the attached pump at low shaft speeds. After
assembly or the cooler, depending on the ship class, it is
the oil leaves the pumps, it fills the main header piping
then sent to the MRG.
where it will travel toward the LO unloader valve and
the LO cooler. One exception to this design is the LO
service system on the DDG-51 class ships in which
Headers
the oil goes to the main LO filter assembly before it
goes to the cooler.
Lubrication and cooling is provided to the MRG and
its accessories through the main LO headers. The
headers are located at the top of the gear case. Gear and
Unloader Valves
pinion teeth are lubricated and cooled by spray nozzles
arranged to direct oil across the full face width at the
On the DD-963, DDG-993, and FFG-7 class
gear mesh. Oil flow to the journal bearings and main
ships, the unloader valves are pneumatic pilot-type
thrust bearings is controlled by orifice plates. When the
valves. On the CG-47 and DDG-51 class ships, the
lubrication and cooling process is complete, gravity then
unloader valves are the hydraulically operated
drains the oil back to the sump where the cycle starts
(Cla-valve) design. Although the unloader valves are
over again.
of different designs for the different ship classes, they
all perform the same job. They maintain proper design
oil pressure throughout the system by maintaining the
MONITORING AND TROUBLESHOOTING
required pressure as sensed at the most remote
PROCEDURES
bearing. Depending on the ship class, the oil will pass
through the unloader valves to either the oil cooler or
Now that we have discussed some of the basic
the oil filter assembly. As we mentioned earlier, most
design features of the MRG LO systems of the different
ships have the cooler as the next component in the
ship classes, let's talk about some general monitoring
l i n e . Because of this, we will discuss this
and troubleshooting procedures.
configuration first.
Monitoring equipment performance is the key to
identifying early equipment failures. As a GSM, you
will be the primary technician and watch stander. You
Lube Oil Coolers
should be knowledgeable in the normal operating
parameters of this system and be able to identify most
All the LO coolers used on gas turbine ships are
abnormalities. Once you have identified a problem, you
basically the same. The only differences exist in the
must use sound troubleshooting procedures to isolate the
way in which the oil temperature is regulated. On the
faulty component or components before you can make
DDG-51 and FFG-7 class ships, the oil flow is
the appropriate repairs. In troubleshooting the MRG LO
regulated at the inlet of the cooler to maintain the oil
service system of your ship, you can use the same
temperature. On the CG-47, DD-963, and DDG-993
g e n e r a l procedures we described earlier for
class ships, however, the seawater flow is regulated to
troubleshooting the FO service system. In the following
maintain the oil temperature. The placement of the
paragraphs, we will provide you with some additional
seawater regulating valve, however, is different for
guidelines you can use as tools to help you maintain the
each of these ship classes. On the CG-47 class ships,
MRG LO system of your ship effectively.
for example, the regulating valve is installed on the
inlet side of the cooler. On the DD-963 and DDG-993
TESTS AND INSPECTIONS
class ships, the regulating valve is placed on the cooler
outlet. Regardless of the class of ship, after the oil
The safe operation and performance of the LO
leaves the cooler, it enters a duplex filter or strainer
system on board your ship must be constantly
assembly.
