mechanical, then solving those problems would not
be that difficult. Unfortunately, a start air system is
The two SACS are attached to the front end of the
highly reliant on electronic interfacing with the
SSDG. One is installed in the No. 2 SSDG enclosure.
control consoles. With so many different variables
The other one is installed in the No. 4 SSDG
associated with the control consoles and the start air
enclosure. In this system, the air is treated in much the
system, such as FO, LO, air permissive, and so forth,
same way as it is in the DD-963 system. Hot
in most cases you will need to call upon a GSE to assist
compressed air is supplied by one of the SACs. The
you in troubleshooting this system. Occasionally,
air is then split into two flow paths before reaching
however, you may get lucky and encounter a problem
the starter. Part of the air will remain hot; the other
that is strictly mechanical. With this in mind, we
part will be routed through a cooler. The hot air will
will discuss some of the mechanical and minor
then be mixed with the air that was routed through the
electrical problems you might encounter in `the start
cooler. The mixing of air takes place in the
air system and some methods you can use to
temperature regulating valve (similar to the DD-963
identify the faulty components.
mixing valve), which will regulate the start air
temperature to 400F.
Air Valve Will Not Cycle. If the air valve will not
The third method, referred to as cross-bleed
cycle, perform the following checks:
starting, is not very frequently used. In fact, you will
use it only when performing the PMS or during a
1. Check the valve's actuating air supply. On the
casualty. Remember, this method can only be used if
DD-963 and DDG-993 class ships, the actuating air is
the other GTM is already running with a gas generator
supplied from the bleed air system. In all the other
(GG) speed of 7,500 rpm or greater. The reason the
ship classes, the activating air is supplied from the
GG speed has a specific set point is because at a lower
ship's LP air system. If activating air is available,
GG speed, sufficient air volume cannot be supplied to
check the pilot air inlet fitting and its filter to see if
the GTM for starting.
they are clogged.
2. Check the pilot actuator assembly. Most of
TESTS AND INSPECTIONS You must carry
the valves for this assembly are equipped with a
out all tests and inspections for all the start air systems
m a n u a l override device. First, activate the
according to the PMS. Generally, there are two tests you
override. If the valve operates, you have narrowed
will conduct on these systems. The first test is checking
the problem down to a faulty solenoid, a faulty or
for the proper operation of the HP/LP start air reducing
loose cannon plug, or loss of the command signal.
stations installed on the CG-, DD-, and DDG-51 class
If the valve still does not operate, it may be jammed
ships. Because the reducing stations are not used very
or the actuating piston seal may be leaking by and
frequently, they must be tested periodically.
the resulting pressure may be insufficient to over-
come the spring pressure.
Another periodic inspection you must make is
on the SACs installed on the FFG-7 class ships.
3. Check the cannon plug connection. If the
Even though the SACs on the FFG-7 class ships are
connection is clean, dry, and tight, then have a GSE
used and tested more frequently than the reducing
check the solenoid and the control circuit.
stations installed on the CG-, DD-, and DDG-51
c l a s s ships, you must still inspect them
Faulty Air Valve Appears to Operate
periodically. As a GSM, you should keep in mind
Properly. This situation will occur occasionally when
the pin that connects the pilot actuator with the valve
used to start your turbines, but the maintenance and
stem shears. When this occurs, the actuator will move
upkeep of these compressors may not be your
properly but the valve stem will not. For a good
responsibility. As a watch stander, however, you
example of this situation, visualize attempting a start
will be responsible for reporting any discrepancies
on a DD-963 class ship. During the start attempt,
you might observe during the operation of these
monitor the start air manifold pressure. It will likely
units.
read normal. Notice, however, that once the GTM
start valve opens, the air pressure drops to zero. When
TROUBLESHOOTING. At times, your proce-
this occurs, you will need to either replace the valve
dures for troubleshooting a start air system can be quite
or, if time permits, disassemble the valve and install
difficult. If all the problems that might arise were
a new pin.
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