Figure 4-7.-DD-963 start air system (simplified).
GTG Starting. If you reexamine figure 4-7, you
If you trace the system shown in figure 4-7 and
compare it with the following listing of the five valves
can see that the valve alignment for a GTG start or
and their positions, you will see the proper valve
motor should be same as for a GTM motor. The only
alignment for GTM LP starting and motoring.
exception is that it does not matter what position the
motor air regulating valve is in.
VALVE
VALVE POSITION FOR:
TYPE
STARTING MOTORING
HP and LP Starting. As we mentioned at the
beginning of this section, there are two methods of
MASKER XFR
START
START
starting--using either HP or LP air. Again, if you
study figure 4-7, you can see that the HP air system
MASKER CLR
OPEN
OPEN
interfaces with the start air system just before the
motor air regulating valve. Notice also in figure 4-7
HI TEMP BLEED
OPEN
CLOSE
that the HP-to-LP air reducing valve pressure and
the orifice are configurations that only apply to DD-
MOTOR AIR REG
OFF
ON
963 ships.
MIXING BYPASS
CLOSE
OPEN
The CG-47 ships share this basic system design,
but the CG-47 HP/LP reducing station has a lower
outlet pressure (45 psig), which eliminates the need
Now that you have seen the valve alignment for
for the orifice pack. Because of the location at which
GTM LP starting and motoring, let's discuss the
the HP air enters the system, there is only one valve
valve alignment for GTG starting.
that must be aligned, the motor air regulator.
