PUMP LOGIC CALIBRATION
then to see the pulsations smoothed out by the filter. The
point where the signal stops or becomes distorted is the
One important and frequently performed task of the
place you should look for trouble.
GSE is to make sure the fuel oil and lube oil pumps cycle
Before you begin signal tracing, it is a good idea to
as designed. This action is called pump logic calibration.
measure the dc voltage. If you have no dc output voltage,
Pump logic calibration is accomplished according to
you should look for an open or a short in your signal
PMS. As a GSE, you must be able to recognize and
tracing. If you have low dc voltage, you should look for
correct any malfunctions that occur with pump logic.
a defective part. Keep your eyes open for the place
Your actions will help keep the engineering plant
where the signal becomes distorted.
operating at its maximum efficiency.
No matter what power supplies you may come
Each gas turbine-powered ship has different pump
across on the various classes of gas turbine-powered
logic settings. These differences are too numerous for
ships, they all do the same thing. They change ac voltage
us to cover in this TRAMAN. In this section, however,
i n t o usable dc voltage(s). For that reason, basic
we will discuss the basic elements of pump logic
troubleshooting and testing will be the same. Although
c a l i b r a t i o n . Remember, refer to the appropriate
technical manual for detailed descriptions of the proper
you may experience problems that have not been
covered specifically in this section, you should have
settings for fuel oil and lube oil pumps.
gained enough knowledge to localize and repair any
power supply problem that may occur.
PUMP LOGIC FUNCTION
During normal operation, the fuel oil booster pumps
ADJUSTMENTS
and lube oil pumps are automatically cycled by pump
control logic. They are cycled between off, slow, and
fast to maintain header pressure. Pump control logic will
Many console power supplies contain dc/dc
control the pumps to increase header pressure when
converters that require adjustment of their output levels.
pump output is inadequate to meet demand.
The adjustment variable resistor and the test points for
monitoring converter output are accessible when the
The cycling characteristics and pressures differ on
each class of ship. Fuel oil pump control logic prevents
power supply cover is removed. An example of a dc/dc
converter with test points, fault LEDs, and an output
loss of fuel to the gas engines by cycling the pump (or
adjustment resistor is shown in figure 5-33.
pumps) up to fast when the pressure drops. Sometimes,
fuel pump control logic cycles both pumps to stop if
Power supplies contain different types of de/de
pressure does not recover after a determined number of
c o n v e r t e r s . These converters vary only in their
seconds. This action prevents flooding of the engine
development of different outputs. The procedures for
room if a fuel leak develops.
a d j u s t i n g each converter will differ only in the
specification of the output level. When adjusting the
On some ships, the fuel pumps must be slowed or
converters of console power supplies, make sure they
stopped manually. Lube oil pump control logic prevents
are under normal load conditions. Some power supply
reduction gear damage by constantly providing positive
converters are wired in parallel pairs. Adjust these by
lube oil pressure to the gear. Pump logic usually cycles
alternately securing the power to one power supply,
the lube oil pumps up and down with respect to lube oil
while adjusting the other.
pressure.
Figure 5-33.--Power supply dc/dc converter.
5-43
