old units will be removed and replaced during a
2. Valve alignmentAre the valves properly
ship repair availability (SRA) or overhaul. As a
aligned? Could the receiver discharge valve be
G S M , you will be limited primarily to the
closed?
performance of general maintenance (PMS) and
AIR PRESSURE IS TOO LOW. Check for the
minor repairs. In the following sections, we will
following conditions:
take a look at some of the components you will
1. Excessive usage or system leaksAre system
need to maintain.
leaks causing excessive use of air?
AUTOMATIC CONTROL VALVES AND
2. Relief valvesIs there evidence of premature
ASSOCIATED COMPONENTS
opening or leak-by?
3. Automatic blowdown valvesIs there evidence
Even before the conception of the gas turbine-
of leak-by?
powered ship, the Navy was using automatic
control valves and automated components. The
4. Injection water pressureIs it low? (Screw-type
need to develop better and more reliable auto-
LPAC)
matic systems came into play with the
ABNORMAL NOISE. Check for the following
i n t r o d u c t i o n of the unmanned engine room
conditions:
c o n c e p t to be implemented on gas turbine-
powered ships.
1. Compressor air inletIs there insufficient air? Is
the filter blocked?
In every gas turbine-powered ship, automatic
control valves and their associated components
2. CompressorIs it rotating properly?
play a very important role in the operations of the
3. Drive couplingIs it defective? (Screw-type
engineering plant. There is at least one automatic
LPAC)
control valve installed in every system in the
engineering plant. There arc so many different
4. Drive beltsAre the drive belts hose? Are they
types of automatic valves, however, we must limit
defective? (Reciprocating-type LPAC)
our discussion to some of the most prominent valve
5. BearingsAre the bearings defective in either
types and their various applications, such as
the motor or compressor?
controlling a tank liquid level, LO temperature, and
LO pressure. For the remainder of this section, we
LOW OIL PRESSURE. Check the following
will discuss some of the uses, operations, and
components and conditions:
maintenance of these valves and their associated
1. Oil pump suction pipingAre there loose
components.
connections?
2. Oil pressure gaugeIs it faulty?
Normal Operation
3. Oil level dipstickIs the oil level below the low
In any system, the type of valve used is normally
mark on the dipstick?
determined by the needs of the system. We will talk
about some of the more commonly used valves and their
4. Oil pump relief valveIs this valve faulty?
design and normal operating characteristics.
5. Oil pumpIs it defective?
AUTOMATIC TEMPERATURE CONTROL
Even though the problems we listed are not
VALVES. An automatic temperature control valve is
all-inclusive, they are probably the most reoccurring
i n s t a l l e d in the MRG LO system of a gas
problems you will face.
turbine-powered ship to maintain the oil temperature
within safe operating limits. The type of valve used for
Overhaul and Repair
this purpose is of the same basic design for all classes
The overhaul and major repair of an LPAC is
o f gas turbine-powered ships. The valve is
pneumatically operated via an externally mounted air
usually performed by a ship's repair facility. An
emergency situation, however, may require your
pilot controller. To function properly, the valve must first
s h i p to perform major repair work on the
receive the proper command air signal from the air pilot
compressor. Normally, the compressor will be
controller. In fact, without the proper command air
replaced from a pool of reconditioned units. The
signal from the controller, the valve is worthless.
