contains the supply of oil for the main LO
at 60 psig discharge pressure and 1220 rpm (about
service system. It collects and retains oil as it
168 shaft rpm (srpm)). The attached pump is
returns from the MRG, main thrust bearing, and
supported by a bracket immediately above the LO
sump top. It is driven by the MRG lower inboard
propulsion turbine synthetic LO system coolers.
The LO return from the MRG to the main sump
second-reduction pinion shaft through a right
has a convoluted flexible connection bolted
angle drive. The angle drive is equipped with a
between the MRG oil pan and the top of the
manually operated disconnect device that may be
sump. The normal operating capacity is 1500 to
used to disconnect the attached pump when the
1550 gallons, and the low operating level is 1400
main shaft is stopped. The attached pump takes
gallons. When the sump is filled to the operating
suction from the sump through an individual
level, the pump suction bellmouths will be
suction line and discharges into the LO service
submerged under all operating conditions. The
piping system. The pump speed is proportional
pump suctions are located away from the
to shaft speed; therefore, the attached pump does
turbulent area so the oil is permitted to deaerate
not deliver enough oil by itself to lubricate the
before entering the suctions. The sump is designed
MRG and to cool the GTE synthetic oil until
to allow free drainage of pockets formed by
higher shaft speeds are reached. The attached LO
stiffeners inside the sump and to allow access for
pump is engaged or disengaged by a lever attached
inspection and cleaning. Lube oil return drains
to the pump coupling.
are located as far as possible from suction
The motor-driven pumps supply oil to the
bellmouths. Structural members in the tank act
system when the propulsion shaft is stopped and
to smooth the turbulence in the oil return area.
augment the attached pump at low shaft speeds.
The sump is equipped with a sludge pit located
The motor-driven pumps are controlled by the
at the lowest point. It is also equipped with a
ECSS pump logic as a function of pressure at the
liquid level transmitter, an RTE, pump and
inlet to the MRG lube oil header. The output of
purifier suction connections, and oil return
the attached pump is not controlled and is
connections.
proportional to shaft speed. Primary system
pressure regulation is accomplished by the
unloader valve. When the ship's speed increases
Lube Oil Pumps
and the total pump output exceeds the regulating
Three positive-displacement LO pumps are
capacity of the unloader, MRG inlet pressure
used to supply oil to the MRG and the LOSCAs
increases. The ECSS pump control logic then
for the propulsion GTEs with an adequate
sequences the motor-driven pumps to change to
a slower speed or secure to maintain oil pressure
amount of filtered, heated, and purified oil
during normal ship operations.
in the normal operating range. When the pump
control logic has sequenced both motor-driven
CG, AND DD LUBE OIL PUMPS.--
pumps to secure, the attached pump supplies the
Three positive-displacement LO pumps are
total LO system requirements. A similar control
sequence operates to maintain oil pressure when
installed in each engine room. There are two
shaft speed decreases. As shaft speed decreases
electric-motor driven LO pumps and a third LO
and LO pressure drops, the ECSS pump logic will
pump that is attached to and driven by the MRG.
Each of the electric-motor driven units has a
start the appropriate pump(s) and control their
vertical screw, positive-displacement pump that
speed to maintain normal LO pressure.
The pumps may be controlled locally at their
is flexibly coupled to a two-speed electric motor
respective controllers. With the LOCAL-
mounted on a common steel bracket. Resilient
REMOTE selector switch in LOCAL, the STOP-
mounting is used between the bracket and the
SLOW-FAST selector switch is operative. With
ship's structure. The pump is rated at 700 gpm
the LOCAL-REMOTE selector switch in the
at high speed and 250 gpm at low speed at a
REMOTE position, control is transferred to the
discharge pressure of 60 psig. The pumps take
ECSS.
suction from the MRG sump through a common
suction line and discharge to the LO service
FFG LUBE OIL PUMPS.--This class of ship
piping.
The attached LO pump is of a similar design
also has three LO pumps. Two of the LO pumps
are two-speed, motor-driven, vertically mounted,
to the motor-driven pumps. The principal
screw-type pumps. The third LO pump is an air-
difference is in the larger size and greater rated
motor driven, vertically mounted, screw-type
capacity. The attached pump is rated at 1140 gpm
4-8
