Remember, even though more than one work center
support bearings. Because of the similarity in shafts,
may be involved, your own work center is ultimately
bulkhead seals, and support bearings among the various
responsible for the readiness of the propulsion shafting.
classes of gas turbine-powered ships, our discussion will
In the following paragraphs, we will describe some of
be in general terms.
the key maintenance requirements and helpful hints you
Normally, the propulsion shaft operations and
can use to maintain the propulsion shafting in peak
maintenance you will encounter will be related to the
main engine room (MER) to which you are assigned.
For example, if your MER drives the port shaft, then the
shaft, all bulkhead and stern tube seals, and support
bearings on that shaft will be your responsibility,
Depending on the delegation of responsibility on
your ship, the responsibility for cleaning the propulsion
shafting and its components could be assigned to the
We know that when the GTE is coupled to the MRG,
MER personnel or to the personnel in the machinery
it transmits its rotation and torque through a series of
space through which the shaft passes. The external parts
gears to reduce its speed. This rotation and torque is then
of the shaft, bulkhead and stern tube seals, and line shaft
relayed to the propeller through the propulsion shafting.
bearings only require general cleaning, such as wiping
But, as this power is transmitted, another force develops.
down, and preservation against rust and corrosion. The
This force is referred to as thrust. The propeller
internal cleaning of the line shaft bearings and bulkhead
generates this thrust that pushes the ship through the
and stern tube seals, however, will be required
water. To react to this thrust, a thrust bearing is required
occasionally according to the PMS. As a GSM, you may
on the propeller shaft to prevent the shaft from being
be assigned the responsibility for cleaning these
pushed into the hull of the ship. As we described in detail
in GSE3/GSM3, volume 1, the main thrust bearing
LINE SHAFT BEARINGS. The line shaft
transmits thrust to the hull and properly positions the
bearing sump may need to be cleaned periodically for
shaft axially relative to the hull.
the following reasons:
Without all of the complexity and to a lesser degree,
1. If the oil is contaminated and requires changing
the line shaft bearings perform many of the same
either by the results of a visual inspection or an
functions as the main thrust bearing. The line shaft
bearings maintain the shaft in axial alignment and guide
the workable rotational speed to the propeller. The
2. If a temperature sensor fails, the oil must be
bulkhead seals do not assist in shaft alignment. In fact,
drained and the inspection covers removed.
they have quite the opposite effect because they are
3. If a casualty has occurred and an inspection is
aligned to the shaft to maintain a watertight seal between
machinery spaces to prohibit progressive flooding. The
stern tube seal is also aligned to the shaft so it can
4. When major work has been completed on the
maintain a watertight seal where the shaft penetrates the
5. Any time cleaning is required by the PMS.
BULKHEAD SEALS. The bulkhead seals should
MAINTENANCE OF EQUIPMENT
be periodically cleaned according to the PMS. This
procedure includes the complete disassembly of the seal
for cleaning, lubricating, and inspecting. The only other
As we mentioned earlier, there may be more than
reason for seal disassembly would be a condition caused
one work center involved in the maintenance of the
by a casualty.
propulsion shafting, depending on the class of your ship.
STERN TUBE SEALS. The stern tube seal and its
Whenever more than one work center is involved, team
components are normally cleaned as part of a general
work and coordination are critical. All work centers
cleanup in the space where this assembly is installed.
involved should get together to plan all maintenance
Other cleaning requirements may have to be performed
related to the propulsion shafting and to make
to the internal parts of this assembly as apart of the PMS
arrangements to provide each other with assistance as
or when a casualty occurs.