Start Air Systems
TROUBLESHOOTING. Neither the masker or
prairie air system will have a vast number of
The start air systems installed on all gas
components to cause the system to fail. This means
turbine-powered ships serve the same purpose: To start
troubleshooting a problem with either system should be
all the ship's propulsion or electric plant turbines. Even
fairly simple. Let's take a look at some problems that
though the start air systems have the same goal, the start
may occur and their possible solutions.
air system in each ship class will accomplish this goal
Incorrect Masker Air System Pressure. In the
in its own individualized way. Except for the DDG-993
masker air system, when the air pressure is either too
class ships, all gas turbine-powered ships have two
high or too low, use the following steps:
methods of starting each propulsion or electric plant
1. Check the pressure gauge for accuracy.
turbine: (1) LP start air and (2) HP start air. In the
DDG-993 class ships, the start air system has only LP
2. Check the bleed air header pressure.
start air capabilities for the propulsion turbines.
3. Check the regulating valve for the proper setting.
Because there are several differences in the start air
Incorrect Prairie Air System Pressure. If the air
systems installed in the different ship classes, we will
pressure in the prairie air system is too high or too low,
first discuss the basic system installed on the CG-47,
take the following steps:
DD-963, and DDG-993 class ships. We will then discuss
1. Check the pressure gauge for accuracy.
the differences.
2. Check the bleed air header pressure.
CG-47, DD-963, AND DDG-993 CLASS
SHIPS. The start air systems installed on the CG-47,
If there is no air pressure in the prairie air system,
DD-963, and DDG-993 class ships use hot bleed air
take the following steps:
from the bleed air header and cool masker air from the
1. Check the pressure gauge for accuracy.
masker air system to provide each turbine with LP
starting air. These start air systems were designed to use
2. Check the system supply cutout valve to make
a bleed-air/masker-air combination because the
sure it is open. Sometimes this valve will
propulsion turbine and GTG starters consume a lower
indicate OPEN and will actually be closed if the
amount of air when the air temperature is increased.
pin connecting the actuator to the valve should
shear. A sheared pin will allow the actuator to
There are three modes of operation for the starter air
move, but not the valve.
system: (1) normal, (2) motor, and (3) emergency. With
Incorrect Masker or Prairie System Airflow.
the bleed air system in the automatic mode, the normal
Incorrect airflow in either system can be caused by the
position for starter air is the primary method of operation
following conditions:
for GTM starting and the motor position is the primary
method of operation for GTM motoring. Also, with the
1. Improper system pressureIs the regulating
bleed air system in the automatic mode, the ECSS logics
valve faulty or improperly set?
for the start air system valves will automatically align
2. Misaligned manual belt cutout valves
for either starting or motoring the GTM. When a GTG
is started, however, its start air system does not interface
3. Blocked holes in the masker belts or propeller
with the ECSS logics. This is why a manual air valve
High Masker or Prairie System Air Tempera-
alignment must be used for GTG starting.
ture. If the air temperature is too high in either the
GTM Starting and Motoring. In the start air
masker or prairie air system, take the following steps:
system for a GTM start, there are five valves that must
1. Check the gauge for accuracy.
be aligned before the GTM start air valve can open:
2. Check the masker or prairie air coolers.
1. MASKER XFR
a. Is the seawater cooling system pressure
2. MASKER CLR
insufficient?
3. HI TEMP BLEED
b. Are the cooler tubes clogged?
4. MOTOR AIR REG
Any of these conditions could be the cause of high air
temperatures in either system.
5. MIXING BYPASS
