CH 555 - SURFACE SHIP FIREFIGHTING Flashcards
Fire zone boundaries confine a fire within a zone and provide protected staging areas
for
fire parties
The minimum tightness for a fire zone boundary is
fume tight
Recent ship designs have fire zone boundaries fitted with a fire insulation on one side that will retard heat transfer
from a fire on the insulated side for a minimum
30 minutes
The single-sided fire insulation system does not
retard heat transfer from a fire on the uninsulated side.
At repair party leader discretion, manning of fire boundaries may be
reduced where fire insulation is installed on the fire side.
What should also be secured to avoid the spread of smoke and fire to surrounding compartments.
Recirculation systems and air conditioning
systems
When a naval ship is put in material condition ZEBRA for
battle, most of the ventilating ducts are
closed
The firemain system is designed for maximum damage resistance with the following survivability features:
a. Multiple, independent pumps
b. Redundant seawater paths
c. Ability to segregate sections
d. Separation of redundant components
e. Resistance to shock
f. Capability for remote operation
This firemain consists of two single mains separated athwartship
as far as practicable, extending fore and aft on the damage control deck.
Horizontal loop system
This firemain consists of two single mains installed fore and aft in
an oblique (e.g. angled) plane, separated both vertically and athwartship, connected at the ends to form a loop
vertical offset loop system
This firemain consists of two service mains installed on the damage control
deck and separated athwartship, and a bypass main normally installed on a lower level near the centerline
composite system
What is installed in the discharge line for each fire pump to prevent back flow through the pump, to prevent the rotating assembly from rotating opposite of design and to prevent subsequent loss of firemain pressure in the
event of pump failure or inadvertent pump shutdown
Check Valve
To prevent overheating during low flow conditions, each
fire pump is equipped with what inwhich connects the pump discharge to either the pump suction line or overboard,
recirculation line
What permit isolation of
the pumps from the sea and the firemain for damage control purposes, and permit pump maintenance
valves
Fire pump is equipped with an orifice sized to pass approximately
5% of the pump’s rated capacity
Each discharge recirculation line for turbine driven centrifugal
fire pumps is fitted with a relief valve set at
125% of the firemain’s rated pressure.
Pumps are located below the water
line to provide a minimum positive static head of
3 feet under all conditions of load and a list of up to
15 degrees.
The standard fire pump can be procured in horizontal configurations
with how many interchangeable impellers to achieve various pressure heads and flow capacities
6
The Navy standard fire pump (NSTFP) is an electric motor
driven centrifugal, close coupled pump of what kind of material
titanium
The centrifugal pump design of the NSTFP is particularly suited for firemain service because
it will deliver a wide range of flow rates within a relatively narrow pressure range
The pump zero flow, or shutoff
head is limited to approximately
1.2 times its rated head to prevent large fluctuations in firemain pressure as
seawater demand varies and to prevent excessive firemain design pressure
Electric motors are preferred
over steam turbine drives because they are
a. more reliable because of less moving parts,
b. require less maintenance,
c. provide rapid start and stop control, and
d. are easier to install
A major disadvantage of motor driven pumps is that they often operate near their shutoff head
because
they operate at constant speed
What is the backup for firemains which have turbine driven fire pumps,
steam supply is a backup
to electric power for firemain supply.
