CONTROLLABLE PITCH PROPELLER
Pump Couplings
SYSTEMS
Other components that require cleaning and
Depending on the class of ship, your ship's
lubrication are the LO pump couplings. Even though the
propulsive thrust is provided by a hydraulically
couplings will not need as much attention as the valves,
actuated propeller system. Each propeller is driven by
frequent cleaning and lubrication are still very
one or two GTEs through a reduction gear assembly
important.
and line shaft.
The procedures for cleaning and lubricating LO
pump couplings are the same as those we described
NORMAL OPERATIONS
earlier in this chapter for the FO pump couplings. The
alignment procedures for LO pump couplings are also
The controllable reversible pitch (CRP) or
the same as those we described for FO pumps. The main
controllable pitch propeller (CPP) systems installed
difference is that the LO system has three pumps,
on all gas turbine-powered ships perform the same
whereas the FO system has two pumps. Because the
basic duties. For this reason, we will confine our
third LO pump is driven by the MRG, the alignment
discussion of the CRP/CPP systems to the major
procedure is much more difficult than the one for the
differences in the design features and operational
electric pump. For the MRG LO service systems found
characteristics found on the different ship classes. If
on the CG-47, DD-963, and DDG-993 class ships, the
y o u require additional information on the
alignment procedures for the third pump require a
fundamental design and operation of these systems,
we recommend you consult the applicable sections of
special short shaft assembly. This special shaft is not
GSE3/GSM3, volumes 1 and 2.
normally kept on board these ships. You must acquire
this tool and special assistance to use it from a SIMA or
T h e CRP/CPP systems were designed to
tender. On DDG-51 class ships, however, the attached
maximize the ability of the ship's propulsion GTE
to accelerate and decelerate rapidly and to enhance
LO pump is mounted on a pedestal in the horizontal
its maneuverability. To further enhance the
position and will not require any special tools for
systems' performance and to make them more "user
coupling alignment.
friendly," some subtle changes were made. These
changes have been installed on the newest gas
turbine ship platform, the DDG-51 class ship. In
REMOVAL AND REPLACEMENT
the following sections, we will tell you about some
OF COMPONENTS
of these changes and the contributions they make
to system performance.
All relief valves in the LO system are usually
After studying this section, you should have a good
inspected and tested annually. Just like the relief valves
understanding of the design, operation, and major
in the FO system, these valves are normally removed
system differences in the CRP/CPP systems installed on
the different classes of gas turbine-powered ships. You
and carried to a SIMA or tender for bench testing. They
should also have a basic understanding of your
can, however, be tested while they are being installed in
responsibilities for caring for and maintaining these
the system and they can be inspected every time the
systems properly.
system is placed in operation. As in the FO system, most
of the low pressure problems in an MRG LO service
system can usually be traced to a faulty pressure relief
DDG-51 Class Ships
or unloader valve.
You may need to remove and replace components
As an operator or technician, you should be aware
because of component failure. Whether you are partially
of the changes incorporated in the CRP/CPP systems
or completely removing a component for inspection,
installed on the DDG-51 class ships and the advantages
testing, cleaning, or lubrication, you should always
they offer in the performance and operation of these
follow the EOSS and other specific procedures required
systems. Let's take a look at some of the components
for your ship.
that have changed.
