As for inspections, the bleed air regulating valves
For each of these systems, we will describe the major
and the overall system must be inspected and monitored
equipment, maintenance, and system similarities or
continuously by engineering personnel while it is in
differences among the ship classes.
operation.
Bleed Air Collection and Distribution System
TROUBLESHOOTING. Troubleshooting a
problem in the bleed air collection and distribution
The bleed air collection and distribution system
system is usually fairly easy to accomplish. Remember,
collects compressed air extracted from the compressors
the movement of air follows the same principles as
of all propulsion turbines and SSGTGs. It then
electricity: Air always takes the path of least resistance.
distributes the air to the four other systems as needed.
In the following paragraphs, we will describe a few of
This is the primary system and contains the bulk of the
the more common problems and some of the steps you
can take to isolate their probable causes.
hardware, consisting of regulating valves, isolation
valves, collection piping, the main header, distribution
Bleed Air System Pressure is Too High. When the
piping, and relief valves.
bleed air system pressure is too high, use the following
steps, in sequence, to isolate the problem:
The bleed air collection and distribution system
extracts compressed air from the customer bleed piping
1. Check and compare pressure readings
of the turbines through a bleed air shutoff valve. To
throughout the plant to verify gauge accuracy.
prepare the air for use throughout the system, a
2. Check the bleed air regulating valves. For CG-,
regulating valve reduces and regulates the extracted air
DD-, and DDG-class ships, if more than one
to 75 psi. Once regulated to 75 psi, the air enters the main
GTG is operating, you will need to alternate the
bleed air header and is distributed to the start air, masker
securing of the bleed air regulating valves to
air, prairie air, or anti-icing air system, depending on the
pinpoint which one is faulty. Also, because
valve configurations of these individual systems.
bleed air from the main engines is not used very
TESTS AND INSPECTIONS. Your respon-
often, t h e regulating valves tend to
sibilities for testing the components of the bleed air
overpressurize the system. For FFG-class ships,
collection and distribution system will be minimal. For
check the bleed air regulating and flow control
valve. If a start air compressor (SAC) is
example, if you are stationed on a twin-shaft ship, there
operating, you should check the start air
are only 13 valves outside of the main engine enclosures
system's isolation check valve for leak-by into
that will require some kind of testing. These valves
the main bleed air header.
include the three 14-stage bleed air valves, seven bleed
air regulating valves (three GTG valves and four GTM
Relief Valve is Lifting. When this condition
valves), the bleed air isolation valve, and two relief
occurs, check the following two areas:
valves. If you arc stationed aboard an FFG-7 class ship,
1. System pressure is too highFollow the
only two valves will require testing, one relief valve and
guidelines in the preceeding paragraph for high
the pressure regulator and flow control valve. For the
system pressure.
most part, all testing for these valves will be covered
under the PMS or as part of the Engineering Operational
2. System pressure is normalIs the relief valve
Procedures (EOP). According to the PMS, you will test
faulty? Is it improperly set?
the operation of the 14-stage bleed air valves and the
System Pressure is Too Low. If the system
relief valves. The PMS for the 14-stage bleed air valve
pressure is too low, take the following steps:
must be conducted quite frequently and usually in
1. Verify the accuracy of the gauge.
conjunction with a major propulsion plant inspection
(safety checks). According to the PMS, the relief valves
2. Check the relief valves for blowby.
must be periodically tested for proper lifting and
3. Check the system for leaks.
reseating pressure.
4. Check the pressure regulating valve for proper
Other tests and inspections will be more frequent.
operation.
For example, you must test the bleed air isolation valves
whenever the No. 3 SSGTG is started. You must test the
M A I N T E N A N C E . You must perform the
maintenance of all valves (electric or air operated) in the
other isolation valve (header) daily according to the EOP
bleed air collection and distribution system according to
to ensure proper operation.
