Figure 5-1.-Grid-type flexible coupling.
HUB. You should check for damaged or worn
it, however, the most important thing you should do
at this point is to ask yourself this question: How long
teeth on the coupling hub. Normally, the coupling
has this coupling been operated with an insufficient
hub teeth will not show symptoms of damage or wear
grease supply? Improper lubrication can easily cause
unless the hub was improperly installed on the pump
a fuel pump coupling to become damaged because of
or motor shaft. (This usually happens when a hub has
the heat that is generated during normal operation.
been hammered onto the pump or motor shaft.) The
hub teeth can, however, become damaged if they
GRID. The coupling grid is a shaped spring steel
become fatigued or overheated. As in the case of the
grid, you will notice a bluish tint on the metal when
band that interlocks the coupling hub gear teeth. The
these conditions occur. Each coupling hub is attached
grid is usually coated or painted. You should check
to its respective shaft by a key. Although the key does
the grid for deterioration or wearing of the coating or
not fail very often, you should check to make certain
paint. The condition of the coating or paint can
the hub fits snugly on the shaft. If the hub moves at
provide you, at a glance, with a clue to the condition
all on the shaft, then you should check the hub inside
of the coupling. If the coupling has been operated
diameter, the shaft key way, and the hub outside
with insufficient grease, the coating or paint may be
diameter for wear.
worn off and the metal will have a bluish appearance.
The bluish color on the metal means that the metal
Fuel Pump Logic
was allowed to become too hot. This is a good
indication that the component is possibly fatigued
Normally, the logic circuits of a ship's fuel pumps
and requires replacement. The coating or paint can
are tested semiannually or during scheduled
also provide you with an indication of coupling
propulsion plant inspections (safety checks). During
misalignment. If you detect an uneven wear pattern,
this maintenance check, you will test the pump logic
there is a good possibility the coupling is misaligned.
circuit to see if the pump will cycle up in speed with
increased