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.
The flushing lines should be opened periodically to flush out any debris and
prevent excessive pressure loss through the strainer.
Y-type strainers are installed in firemain branch lines for services such as AFFF to protect
the control valves of these systems
Suction lines of the fire pumps are protected by
hull plate strainers
Due to weight
saving advantages, high performance butterfly valves are allowed as WILLIAM cutout valves for sizes
of 2-1/2 inches and above
What installed on the discharge side of centrifugal
fire pumps, to prevent back flow and resultant reverse rotation of secured pumps
check valve
When firemain pressure increases
because of low demand from installed services, the pressure regulating valve will
open to divert flow overboard
As
firemain pressure drops due to additional services being energized,
the flow overboard is reduced
Which valves are installed on the recirculation line downstream from turbine driven
pumps.
Relief valves
A combination vacuum and pressure gage is installed on the
suction piping of each fire pump.
On a fire pump, the pressure gage is installed on the
discharge piping
The authority to start or stop fire pumps resides
with
the Engineer of the Watch (EOOW) underway, and the Duty Engineer in port.
A medium or small firemain break and or when the intended service being placed on line will be noticed by the as
a drop in pressure
The firemain should be operated at
the lowest pressure sufficient to meet the
needs of the connected services
During operation, a pressure increase in the firemain will be due to a pump being started or
service being secured
At extremely high flow rates, the pump may
cavitate and lose suction
To raise the firemain
pressure, place additional pumps on line or
secure services
The automatic sprinkling systems are
equipped with
flow switches.
When pressure is regained, the rupture or ruptures will be downstream
of the
last valve closed
Pipe sizes are based on
copper-nickel pipe
The valve(s) in the AFFF concentrate suction line(s) when the firemain is
returned to service should be
open
Fixed AFFF sprinkling systems, the high capacity AFFF stations supply
various
1-1/2 and 2-1/2 in AFFF hose station
AFFF service outlets installed for below decks use are
equipped with
a 1-3/4 inch or 1-1/2 inch hose (50 - 175 feet)
Navy standard fire hose
150ft
The flow rate setting for the
1-1/2 inch nozzle is
125 gpm (95 gpm in machinery spaces.)
The flow rate for the 2-1/2 inch AFFF nozzle is
250gpm
Each washdown/firefighting zone supplies up to
1,000 gpm of seawater/AFFF
Overhead AFFF sprinkling systems are installed to extinguish
class B pool fires located on the deck
On the AFFF hose station, the pushbuttons are enclosed in a watertight boxes with hinged covers painted
red/green strips
A power distribution
system is provided for electrical control of the AFFF proportioning system. The electrical system is divided into
several units, consisting of
2 to 21 distribution centers
Root valves in the firemain branches to the AFFF proportioner stations are classified
WILLIAM and
shall be kept open at all times.
A bell switch may be provided at each outlet for ringing the injection station to man up the
X50J
Carbon dioxide (CO2) is a colorless, odorless gas that is naturally present in the atmosphere
at an average concentration of
0.03%
The amount required to extinguish fire with CO2 concentrations is
30 to 70 percent
Carbon dioxide for fire fighting is maintained as a liquid
at high pressure
At the concentrations
expected after discharge of CO2, Dizziness, increased respiration rate and headaches will occur at low
concentrations and loss of consciousness will occur in less than
15-35 seconds
Each
system is designed such that a single discharge of Halon 1301 will provide a concentration of
5 to 7 percent halon 1301
Sufficient
Halon is required so that the concentration will remain at a minimum of 5 percent for
15 minutes
HFP
systems for spaces with diesel, JP-5, or gasoline fuels are designed such that a single discharge will provide a
minimum average concentration of 8.5%, which must be maintained for
15 minutes
The sprinklers are the
closed head type and will actuate automatically when exposed to heat, typically at
175 degrees
