Note: Descriptions are shown in the official language in which they were submitted.
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Title: FIRE EXTINGISHING APPARATUS AND METHOD
FIELD OF THE INVENTION
The present invention relates to a fire extinguishing apparatus and method
using a non-
flammable liquid which is sprayed as a mist to extinguish a fire in a risk
area.
The present invention may also provide a replacement for an existing fire
extinguishing apparatus based upon the use of the now banned HALON.
Hereinafter, the present invention will be described with particular reference
to
use with the non-flammable liquid being water although it could be used with
other non-
flammable liquids which absorb heat as they vaporise.
BACKGROUND OF THE INVENTION
In fighting fires it is known that there are three major contributing factors
to the
continuation of the fire. These factors are heat, oxygen and fuel and the
interrelationship
of these factors is shown pictorially in Figure 6. Conventionally when
extinguishing
fires, fire fighters act to remove at least one of the three elements
necessary for
combustion. Typically, fire fighters use either water, COZ, halon, dry
chemical or foam.
Water acts by removing the heat from the fuel, whilst carbon dioxide works by
displacing
the oxygen.
Another aspect of combustion is a chain flame reaction indicated by a circle
which contains the triangle, as shown in Figure 6. The chain flame reaction
relies upon
free radicals which are created in the combustion process and are essential
for its
continuation. Halon operates by attaching itself to the free radicals and thus
preventing
further combustion by interrupting the flame chain reaction.
The main disadvantage of water is that considerable amounts of water are
required in extinguishing a fire which leads to considerable damage by the
water. Also,
in some instances suitable quantities of water to extinguish the fire are not
available.
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Carbon dioxide and halon both have the disadvantage that all people must be
evacuated
from the area in which they are to be used since it will become impossible for
the people
to breathe. For this reason, fire fighters using these extinguishing agents
must use
breathing apparatus. Also, for COZ and Halon to extinguish the fire any
ventilation of the
area must be shut down. Halon has a further disadvantage that it is highly
toxic and very
damaging to the environment. For those reasons, the use of halon in
extinguishing fires
has been banned in most circumstances.
The present invention overcomes the above disadvantages by using a non-
flammable liquid, such as water, to reduce the heat of the vapour around the
fuel, reduce
the heat of the fuel, displace the oxygen, and interrupt the flame chain
reaction. That is,
the liquid attacks all parts of the combustion process except for removing the
fuel. The
invention is based upon the generation of a relatively fine mist of liquid
(referred as a
mist), such as water, which displaces the oxygen, and upon heating evaporates
and
expands to fixrther displace the oxygen. Upon expansion the water mist absorbs
heat
from the vapour around the fuel and from the fizel. Also, the mist interrupts
the flame
chain reaction by attaching to the free radicals. The mist also has a
smothering effect and
a cooling effect upon the fire. For these reasons, the mist has the surprising
result that a
relatively small amount of water can safely be used to extinguish A, B and C
class fires
as well as electrical fires.
The mist generated by the fire extinguishing apparatus of the present
invention is
not a water on flame scenario. Its operation is more akin to gaseous fire
extinguishing
mediums such as C02 or halon.
These surprising results occur due to the very rapid evaporation rate possible
with
a fine mist of liquid (typically 50-500 microns), the heat absorption
characteristics of
water as it vaporises, the ability of the fine mist to reduce the convection
of heat from the
fire to surrounding objects and the ability of the mist to displace oxygen.
This is due to
the expansion ratio of water from liquid to vapour.
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In an embodiment of the fire extinguishing apparatus of the present invention
a
typical fire confined to a room or the like can be entirely extinguished, for
example,
within about 30 seconds with a number of nozzles each spraying about 0.4
litres/min of
water as mist at about 20 bar, with one nozzle per 2.65 m3. This is a very
small rate of
application of water to douse a fire when compared to the prior art.
The spray flux density in the above stated example can be readily calculated
as:
spray flux density = 0.4 litres/min = 2.65m3 = 0.15 litre/min/m3.
However, the present invention is not limited to operation at pressures of 20
bar,
and can operate at higher pressures, e.g. up to 250 bar.
The invention in its general form will first be described, and then its
implementation in terms of specific embodiments will be detailed with
reference to the
drawings following hereafter. These embodiments are intended to demonstrate
the
principle of the invention, and the manner of its implementation. The
invention in its
broadest and more specific forms will then be further described, and defined,
in each of
the individual claims which conclude this Specification.
SUMMARY OF THE INVENTION
In accordance with one aspect of the present invention there is a provided
fire
extinguishing apparatus for extinguishing a fire located in a risk area, the
fire
extinguishing apparatus comprising:
spray means for spraying non-flammable liquid therefrom into the risk area,
delivery means for passage of the non-flammable liquid for delivery thereof
under
pressure to said spray means,
detector means for detecting the presence of a fire in the risk area, and
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fluid delivery control means to allow delivery of the non-flammable liquid via
said delivery means to said spray means following actuation of said fluid
delivery control
means, wherein, in use,
said spray means sprays the non-flammable liquid therefrom to form a mist
having a median droplet size of substantially 500 microns or less,
said non-flammable liquid is sprayed from said spray means at a rate of
substantially 1 litre or less per minute per cubic metre of volume of the risk
area, and
said non-flammable liquid is sprayed from said spray means into said risk area
to
form said mist of the non-flammable liquid,
such that the said mist of non-flammable liquid droplets can be applied to the
fire
to extinguish the fire.
In accordance with another aspect of the present invention there is provided a
method of extinguishing a fire in a risk area comprising the steps of
detecting the presence of a fire in the risk area,
actuating fluid delivery control means for delivery of a non-flammable liquid,
delivering the non-flammable liquid under pressure to spray means, and
directing a spray of the non-flammable liquid from the spray means into the
risk
area, characterised by
spraying the non-flammable liquid into the risk area to form a mist having a
median droplet size of substantially 500 microns or less,
spraying the non-flammable liquid at a rate of substantially 1 litre or less
per
minute per cubic metre of volume of the risk area, and
spraying the non-flammable liquid into the risk area to form said mist of the
non-
flammable liquid,
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such that the said mist of non-flammable liquid droplets is applied to the
fire to
extinguish the fire.
Preferably, said non-flammable liquid is sprayed from said spray means at a
rate
in the range from 0.1 litre per minute per cubic metre of volume of the risk
area to 0.63
5 litre per minute per cubic metre of volume of the risk area.
It is also preferred that said non-flammable liquid is sprayed from said spray
means at a rate in the range from 0.15 litre per minute per cubic metre of
volume of the
risk area to 0.63 litre per minute per cubic metre of volume of the risk area.
It is further preferred that said non-flammable liquid is sprayed from said
spray
means at a rate in the range from 0.25 litre per minute per cubic metre of
volume of the
risk area to 0.44 litre per minute per cubic metre of volume of the risk area.
It is also preferred that said non-flammable liquid is sprayed from said spray
means at a rate in the range from 0.15 litre per minute per cubic metre of
volume of the
risk area to 0.32 litre per minute per cubic metre of volume of the risk area.
I S It is furthermore preferred that said non-flammable liquid is sprayed from
said
spray means at a rate in the range from 0.25 litre per minute per cubic metre
of volume of
the risk area to 0.32 litre per minute per cubic metre of volume of the risk
area.
Preferably, the median droplet size of the mist is between substantially 50
and 500
microns.
More preferably, the median droplet size of the mist is between substantially
250
and 400 microns.
Preferably, the non-flammable liquid is delivered from a storage reservoir
means
via the delivery means to the spray means.
Preferably, the storage reservoir means comprises a container.
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Preferably, propelling means propels the non-flammable liquid under elevated
pressure to the spray means.
Preferably, the propelling means propels the non-flammable liquid at a
pressure of
substantially 20 bar (2000 kPa) or less.
Preferably, control means is provided and enables actuation of said fluid
delivery
control means from a location remote from the fluid delivery control means.
Preferably, the control means is provided in operative association with the
detector means for controlling delivery of the non-flammable liquid to the
spray means.
Preferably, upon the detector means detecting the presence of a fire in the
risk
area, the detector means initiates said control means to actuate said fluid
delivery control
means.
Preferably, said fluid delivery control means comprises at least one valve.
Preferably, the spray means operates for substantially 90 seconds or less to
extinguish the fire.
Where the storage reservoir means comprises a container, the propelling means
may be provided as a gas, such as for example, dry nitrogen, in the container.
Preferably, the spray means comprises a plurality of nozzles and the number of
nozzles required for the risk area is determined as function of the air volume
of the risk
area, the flow rate of the nozzles and a compensating factor, the function
being:
N.N = [A.V. / C.F.] / 90FR
where - N.N. is the number of nozzles,
- A.V. is the air volume of the risk area
- C.F. is the compensating factor as defined herein, and
- 90FR is the volume of water which flows through one of the nozzles in
90 seconds.
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Preferably, the nozzles each discharge the non-flammable liquid at a rate of
less
than substantially 2 litres/minute.
Preferably, the nozzles each have a spray angle of greater than substantially
70°.
Preferably, the nozzles are spaced about 1 metre apart in the risk area.
Preferably, the non-flammable liquid is water or an aqueous solution.
Preferably, the non-flammable liquid contains additives.
The present invention may be used in risk areas where the invention provides a
satisfactory means of fire extinguishment. This includes, for example,
machinery and
equipment spaces, engine rooms, pump rooms, computer rooms and storage rooms.
The foregoing summarizes the principal features of the invention and some of
its
optional aspects. The invention may be further understood by the description
of the
preferred embodiments, in conjunction with the drawings, which now follow.
BRIEF INTRODUCTION OF THE DRAWINGS
An exemplary embodiment of the present invention will now be described with
particular reference to the accompanying drawings, in which:
Figure 1 is a perspective view, seen from above, of an engine room of a ship
shown fitted with an embodiment of a fire extinguishing apparatus in
accordance with the
present invention;
Figure 2 is a graph showing the fire extinguishing capabilities of the fire
extinguishing apparatus of Figure 1, in a test facility, for extinguishing
ignited
isopropanol, petrol and diesel;
Figure 3 is a graph similar to Figure 2 but showing a comparison of the
extinguishing capabilities of the fire extinguishing apparatus of FIG. 1 and
the use of
carbon dioxide on ignited petrol;
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Figure 4 is a graph showing typical maximum fire temperature characteristics
of
fires treated with the fire extinguishing apparatus of Figure 1;
Figure 5 is a cascade test facility for testing the fire extinguishing
apparatus of
Figure 1; and,
Figure 6 is a pictorial representation of the combustion triangle and flame
chain
reaction circle.
DESCRIPTION OF THE PREFERRED EMBODIMENT
In Figure 1 there is shown a fire extinguishing apparatus 10 comprising a
pressurised container 12, pipes 14 and 16, a plurality of nozzles 18, a
plurality of fire
detectors 20 and a control panel 22.
Also shown in Figure 1 is an engine room 100 having a surrounding wall 102
within which is located an engine 104, fuel tanks 106, an exhaust pipe 108, an
exhaust
muffler 110, a heat exchanger 112, and a propeller shaft well 114. The engine
room 100
is a typical layout of the engine room of a ship.
The container 12 is typically made from galvanised metal materials and capable
of withstanding pressures up to for example 3000 kPa. Typically, the container
12 has a
charge of distilled water maintained under pressure by a charge of dry
nitrogen.
Typically, the container 12 has a capacity between about 5 and 30 litres.
However, the
container 12 could have virtually any capacity, although by the nature of the
operation of
the present invention the container 12 may be much smaller than prior art
containers.
Typically, the pressurised container 12 is located proximate the surrounding
wall
102. The container 12 has a control valve 30 attached to its outlet for
controlling the
expulsion of the water under pressure from the container 12. The control valve
30 may
be actuated electrically or mechanically and the actuation may be automatic or
manual.
The pipes 14 and 16 form a plumbing network 36 attached to the flow rate
control
valve 32 and each carry a plurality of the nozzles 18. The pipes 14 and 16 and
hence the
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nozzles 18 are strategically located about the engine room 100, as described
hereinafter.
Also, the nozzles 18 are oriented in strategic directions from the pipes 14
and 16. For
example, the nozzles 18 are oriented so as to ensure that the pressurised
water from the
container 12 can be sprayed to all areas of the engine room 100 and to
concentrate on
areas of higher flame potential. Preferably, the pipes 14 and 16 are oriented
about a roof
of the engine room 100 and into the propeller shaft well 114. The nozzles 18
are then
oriented downwardly and/or outwardly from the pipes 14 and 16. Typically, the
plumbing network 36 is coupled to the pressurised container 12 by a flexible
water way.
Typically, the plumbing network 36 has a bore diameter not less than l2mm.
Also, the
plumbing network 36 preferably is capable of withstanding internal pressures
of at least
3000 kpa. Further, it is preferred that the plumbing network be of a looped
design and
that there be no ends in the lines of the plumbing network.
The nozzles 18 are typically formed from brass or stainless steel and include
a
swirl chamber and an elongate cone inlet filter. The swirl chamber increases
the
atomisation of water passing through it and the filter inhibits blockage of
the swirl
chamber by detritus material. The nozzles 18 typically produce a droplet size
between 50
and 500 microns, more particularly between 250 and 400 microns. The spray
pattern
from the nozzles 18 is typically substantially 70° or greater at a
pressure of 2000 kpa (20
bar) or less. Also, the nozzles 18 typically have a minimum orifice size of
about lmm2~
The nozzles 18 use the liquid pressure alone to produce very finely atomised
droplets in a
hollow cone spray pattern with uniform distribution for achieving high misting
performance. 'The water is sprayed from the nozzles 18 at 1 litre or less per
minute per
cubic metre of the volume of the risk area 100. This is reflected in the
example and tests
hereinafter described. The nozzles 18 may each discharge water at a rate of
less than
substantially 2 litres per minute.
The nozzles 18 used in the exemplary embodiment are typically those available
under the Registered Trade Mark LTNIJET. The following specific nozzles are
considered particularly useful:
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FLOW RATE (L/MIN) PRESSURE (BAR)
TYPE
0.65 20
TN-4
0.83 20
TN-6
0.96 20
TN-8
1.06 20
TN-10
The nature and size of the nozzles 18 to be used in a particular engine room
100
(or other risk area) depends upon a number of factors and can be calculated as
shown in
example 1.
5 EXAMPLE 1
To determine the quantity and type of nozzles 18 to use the following
calculations
can be performed.
The calculation is performed according to the following glossary of terms:
G.V. - the gross volume which represents the volume of the risk area (height H
x
10 width W x length L);
N.V. - the net volume which represents the gross volume of the risk area minus
all
solid objects within it - also referred to as the air volume of the risk area
or simply the
volume of the risk area and denoted A.V.;
W.R. - water required which represents the amount of water required in litres
to
be introduced into the risk area;
N.N. - the number of nozzles required to spray the mist into the risk area in
a
substantially uniform manner;
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90FR - a ninety second flow rate which represents the volume of water which
flows through each nozzle 18 in 90 seconds at 20 bar (typically 1.26 litres);
C.F. - a compensating factor which we have developed through experimentation
for each flow rate of nozzle 18 as shown below:
2.8 for TN-4 type nozzle 18
2.1 for TN-6 type nozzle 18
1.8 for TN-8 type nozzle 18
1.1 for TN-10 type nozzle 18
W.V. - water volume in cubic metres (i.e. W.R./1000)
P.V. - potential vapour which represents the expansion ratio of vaporisation
of
water, namely 1700 x W.V.;
P.F.B. - potential fuel by-products due to combustion and represents the
amount
of C02 and H20 which are released as gases during combustion of the fuel, for
example
212 grams of CIS H32 (diesel) produces about 1525 litres of C02 and H20 under
complete
combustion, and about 1284 litres of COZ and H20 for a similar mass of CBH~o
(xylene
petrol);
The water capacity and the number of nozzles 18 required is then represented
by
the following formula:
W.R. _ (N.V. / C.F.)
N.N. = W.R. / 90FR
Thus, the above formula, W.R. = N.V. / C.F., enables the compensating factor
(C.F.) to be determined through experimentation for each flow rate of nozzle
18 as
previously hereinbefore described. The experimentation is carned out in a risk
area 100,
where nett volume (N.V.) has been calculated, using given nozzles 18.
Performance
characteristics, e.g. flow rates, for given nozzles 18 can be readily obtained
from
manufacturers' performance data sheets. Experimentation is carried out to
determine the
amount of water required (W.R.) to extinguish a fire using given nozzles 18.
Through
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such experimentation the compensating factor (C.F.) is determined by using the
formula:
C.F. = N.V. / W.R.. Once the compensating factor (C.F.) is determined in this
way for a
given nozzle 18, it can be used in future calculations for fire extinguishing
apparatus
according to the present invention using such nozzles 18.
The compensating factor (C.F.) is also the minimum number that will achieve a
potential vapour (P.V.) of approximately 81% of the nett volume (N.V.). It is
also the
minimum number that will aid in achieving the number of nozzles (N.N.) capable
of
offering enough nozzles 18 to achieve approximate 1 metre minimum nozzle
spacings.
Thus, given a risk area 7m x 4m x 1.7m, with 3 obstructions one of which is lm
x
lm x lm and the other two obstructions being 1.8m x 0.9m x 0.8m, and using
nozzles 18
of the type TN-6 the number of nozzles 18 required is determined as follows:
G.V.=7x4x 1.7
= 47.6 m3
N.V.=G.V.-[(lxlxl)+2x(1.8x0.9x0.8)]
= 47.6 - 3.592
= 44.008 m3
W.R. _ (44.008/2.1 )
= 20.91
N.N. = 20.9 / 1.26
= 16.58 nozzles
N.N. = 17 NOZZLES
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NB: Always round up to the nearest whole number i.e. in this case N.N. is 17
and
the volume of water required W.R. must be adjusted accordingly (i.e. W.R. in
this
example is 21.4 litres).
In the above example, the spray rate (i.e. spray flux density) can be readily
determined by multiplying the nozzle flow rate (F.R.) by the number of nozzles
(N.N.),
which gives the total flow rate, and dividing by the nett volume (N.V.). For
the type TN-
6 nozzle used in that example, this gives: (0.83 litre/min x 17) = 44.008m3 =
0.32
litre/min/m3 of the risk area. Similar calculations can be made to determine
the spray flux
densities when the nozzle types TN-4, TN-8 and TN-10 are used from the data
previously
set out herein for those nozzle types. The results of such calculations are
spray flux
densities as follows: TN-4: 0.25 litre/min/m3; TN-8: 0.44 litre/min/m3; TN-10:
0.63
litre/mim/m3.
The fire detectors 20 include a fixed temperature fire detector 40 and a rate
of rise
fire detector 42. The fixed temperature detector 40 typically includes a
bimetallic strip
with an extension rod which elevates a diaphragm to make a contact when the
ambient
temperature increases above a predetermined temperature. Typically, the fixed
temperature is between 60 and 100°C. The rate of rise fire detector 42
typically includes
a diaphragm and an air chamber, wherein the chamber leaks air through a fence
tube in
the diaphragm at relatively low rates of rise in temperature but which causes
raising of
the diaphragm to make a contact at relatively high rates of rise of the fire
temperature.
Typically, the rate of rise fire detector 42 is set to be active when the rate
of rise in
temperature is greater than about 9°C per minute.
The detectors 20 also typically include smoke detectors. The smoke detectors
are
preferably located so as to detect air flowing out of the risk area to sense
any smoke
entrained in the air.
The control panel 22 is located so as to be easily accessed during a fire. For
example, the control panel 22 may be located on the outside of the surrounding
wall 102
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of the engine room 100. The control panel 22 includes a wiring fault detection
monitoring system and an activation system. The fault detection monitoring
system
monitors the wiring to the fire detectors 20 and the control valves 30 and 32
for open
circuits, short circuits and unstable wiring conditions. The control panel 22
also senses
the pressure in the pressurised container 12 and issues an alarm in the event
that the
pressure falls below a predetermined pressure. The activation system is of the
"detonator" type which causes the control valves 30 and 32 to release the
pressurised
water from the container 12. Typically, the control panel 22 includes a mist
release push
button having a lift cover placed over it. The mist release push button is
required to be
activated to manually release the water from the container 12. The control
panel 22 is
also connected to visual and audible alarms located in the engine room 100.
In use, the fire extinguishing apparatus 10 is installed into a risk area,
such as the
engine room 100, by first calculating the number of nozzles required, the type
of nozzles
to use and the volume of water required for example as shown in Example 1. The
nozzles 18 are then spaced about the engine room 100 along the pipes 14 and 16
to the
pressurised container 12 via the control valves 30 and 32. For example, the
nozzles 18
may be spaced about 1 metre apart in the engine room 100. However, other
suitable
spacings of the nozzles 18 may be used. The control panel 22 is located on the
outside of
the engine room 100 and wired into the fire detectors 20 and the control
valves 30 and 32
and the audible and visual alarms.
In the event of a fire or rapid increase in temperature in the engine room 100
the
fire detector 40 or 42 is triggered to initiate the control panel 22 to
operate the control
valves 30 and 32 to release water under pressure out of the container 12. The
pressurised
water passes along the pipes 14 and 16 to the nozzles 18. The water passes
through the
filters and swirl chambers of the nozzles 18 and forms a fine mist having a
median
droplet diameter between 250 and 500 microns. The median droplet diameter is
an
expression of the droplet size in terms of the volume of the liquid and is a
value where
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50% of the total volume of the liquid sprayed is made up of droplets with
diameters
larger than the median value and 50% smaller than the median value.
The following test procedures were performed in a test rig situated in a forty
foot
cargo container having its access doors open at one end and with a plurality
of the
5 nozzles 18 located mid way up the side walls of the container. Flammable
fluid was
placed in a tray located on the floor of the container intermediate of the
length of the
container. The results of the tests are as follows:
TEST 1 Purpose: VISUAL DEMONSTRATION--ISOPROPANOL
EXTINGUISHING MEDIUM WATER MIST
10 FUEL ISOPROPANOL
AMOUNT OF FUEL USED 3 1
SURFACE AREA OF FIRE 0.636 mz
DETECTION TIME 5 s
NOZZLE SIZE HF-16
15 ORIFICE SIZE 1.1 mm
CAPACITY EACH NOZZLE AT 20 BAR 0.683 1/min
CAPACITY ALL NOZZLES AT 20 bar 16.41/min
WATER PRESSURE 2000 kpa (20 bar)
SPRAY ANGLE 84°
NUMBER OF NOZZLES 24
NUMBER OF EFFECTIVE NOZZLES 14 TO 16
MEDIAN DROPLET SIZE 375-400 MICRONS
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TIME TO EXTINGUISH 23 s
RATE OF ABSORPTION 21.7°C./s
The number of nozzles 18 which were effective was less than the total number
of
nozzles 18 since the doors of the container were open.
TEST 2 Purpose: VISUAL DEMONSTRATION--PETROL
EXTINGUISHING MEDIUM WATER MIST
FUEL PETROL
AMOUNT OF FUEL USED 3 1
SURFACE AREA OF FIRE 0.636 m2
DETECTION TIME 3 s
NOZZLE SIZE HF-16 x 16
HF-32 x 8
ORIFICE SIZE HF-16 = 1.1
mm
HF-32 = 1.5
mm
CAPACITY ALL NOZZLES AT 20 bar 21.81/min
WATER PRESSURE 2000 kpa (20
bar)
SPRAY ANGLE HF-16 = 84
HF-32 = 91
NUMBER OF NOZZLES 24
NUMBER OF EFFECTIVE NOZZLES 16
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MEDIAN DROPLET SIZE HF-16 = 375-400 micron
HF-32 = 350-375 micron
TIME TO EXTINGUISH 13 s
RATE OF ABSORPTION 1.123°C./s
TEST 3 Purpose: VISUAL DEMONSTRATION--DIESEL
EXTINGUISHING MEDIUM WATER MIST
FUEL DIESEL
AMOUNT OF FUEL USED 3 1
SURFACE AREA OF FIRE 0.363 m2
DETECTION TIME 12 s
NOZZLE SIZE HF-16
ORIFICE SIZE 1.1 mm
CAPACITY EACH NOZZLE AT 20 bar 0.6831/min
1 S CAPACITY ALL NOZZLES AT 20 bar 16.41/min
WATER PRESSURE 2000 kpa (20
bar)
SPRAY ANGLE 84
NUMBER OF NOZZLES 24
NUMBER OF EFFECTIVE NOZZLES 24
MEDIAN DROPLET SIZE 375-400 MICRONS
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TIME TO EXTINGUISH 6 s
RATE OF ABSORPTION 0.33° C./s
TEST 4 Purpose: COMPARISON OF MIST
WITH COZ
EXTINGUISHING MEDIUM WATER MIST
FUEL PETROL
AMOUNT OF FUEL USED 21
SURFACE AREA OF FIRE 0.636 m2
DETECTION TIME 5 s
NOZZLE SIZE HF-16
ORIFICE SIZE 1.1 mm
CAPACITY EACH NOZZLE AT 20 bar 0.683 1/min
CAPACITY ALL NOZZLES AT 20 bar 16.41/min
SPRAY ANGLE 84
NUMBER OF NOZZLES 24
NUMBER OF EFFECTIVE NOZZLES 24
MEDIAN DROPLET SIZE 375-400 MICRONS
TIME TO EXTINGUISH 12 s
This is hereinafter referred to as the "mist test".
TEST 5 Purpose: COMPARISON OF MIST WITH C02
EXTINGUISHING MEDIUM CARBON DIOXIDE
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FUEL PETROL
AMOUNT OF FUEL USED 21
SURFACE AREA OF FIRE 0.636 m2
DETECTION TIME 5 s
QUANTITY OF COZ 32 kg
NUMBER OF NOZZLES 6
NUMBER OF EFFECTIVE NOZZLES 6
TIME TO EXTINGUISH 17 s
This is hereinafter referred to as the "C02 test"
As previously described herein, the above described tests 1 - 5 were conducted
in
a forty (40) foot cargo container. This is a standard container having
dimensions (in
metres) of approximately 12m x 3m x 3m. This gives a volume of 108m3. The
spray rate
(i.e. spray flux density) can be readily determined by dividing the total flow
rate of the
nozzles 18 (which is referred to as the "CAPACITY ALL NOZZLES AT 20 bar" in
the
test data hereinabove) by the volume of the risk area, i.e. 108m3.
For Tests 1, 3 and 4 this gives: (16.4 litre/min = 108m3 = 0.15 litre/min/m3,
whilst
for Test 2 this gives (21.8 litre/min) = 108m3 = 0.20 litre/min/m3.
Whilst the approximate dimensions of a 40 foot cargo container are 12m x 3m x
3m, a forty (40) foot cargo container is available in two specification sets,
namely 8'6"
and 9'6", with a slight variation in the dimensions of the containers in each
set. The
dimensions (length x width x height) of the containers in the 8'6" set are
within the
ranges: (12.009m -12.041m) x (2.345m - 2.356m) x (2.359m - 2.395m). The
dimensions (length x width x height) of the containers in the 9'6" set are
within the
CA 02144540 2006-O1-09
ranges: (12.024m - 12.035m) x (2.346m - 2.352m) x (2.681m - 2.700m). These
dimensions give lower and upper values for the volumes for the 8'6" containers
of
66.43m3 and 67.94m3; and for 9'6" containers the lower and upper values for
the volumes
are 75.63m3 and 76.43m3. The spray rate (i.e. spray flux density) can be
readily
5 determined by dividing the total flow rate of the nozzles 18 (which is
referred to as the
"CAPACITY ALL NOZZLES AT 20 bar" in the test data hereinabove) by the volume
of
the risk area, i.e. the volume of the container.
For Tests 1, 3 and 4 this gives:
10 16.4 litres/min = 66.43m3 = 0.25 litre/min/m3
16.4 litres/min = 67.94m3 = 0.24 litre/min/m3.
16.4 litres/min = 75.63m3 = 0.22 litre/min/m3
16.4 litres/min = 76.43m3 = 0.21 litre/min/m3.
15 Whilst for Test 2 this gives:
21.8 litres/min = 66.43m3 = 0.33 litre/min/m3
21.8 litres/min = 67.94m3 = 0.32 litre/min/m3
21.8 litres/min = 75.63m3 = 0.29 litre/min/m3
21.8 litres/min = 76.43m3 = 0.29 litre/min/m3."
20 In the test procedures each of the fuels was ignited and allowed to flame
up for
between 25 to 60 seconds, after which time the fire extinguishing apparatus 10
was
activated to extinguish the fire. The temperature inside the container was
monitored from
the time of ignition of the fuel until after extinguishing of the fire
produced thereby.
These results are shown graphically in Figures 2 and 3. Figure 2 relates to
tests 1 to 3,
and tests 4 and 5 are shown graphically in Figure 3. An arrow indicated "I"
represents
the point in time at which the fire extinguishing apparatus 10 was activated
(or initiated)
and an arrow indicated "E" indicates the point in time at which the fire was
extinguished.
CA 02144540 2006-O1-09
21
The result of each of the tests of the fire extinguishing apparatus 10 is that
the fire
was extinguished in a relatively short period of time typically less than the
25 seconds. It
should also be noted, particularly as shown in Figure 3, that the temperature
reducing
effect of the fire extinguishing apparatus 10 is greater than that of carbon
dioxide. This
occurs because as the temperature in the risk area increases the volume of the
water mist
increases dramatically as it changes state from water mist to water vapour.
Water vapour
has a volume which is 1700 times greater than the volume of the water from
which it was
produced. Hence, the water vapour further displaces the oxygen from the risk
area and
inhibits the risk area from maintaining combustion. Also, in the change of
state of the
water from liquid to gas it absorbs heat 540 times greater than that of the
liquid phase.
Further, the increase in temperature of the risk area decreases the specific
gravity of the
water which increases its velocity, decreases its droplet size and increases
the flow of the
water throughout the risk area. That is, the water mist is more effective with
increase in
temperature of the risk area. This does not usually occur with other fire
fighting
1 S mediums.
In Figure 4 there is shown a graph of temperature versus time showing the
minimum operational characteristics of the fire extinguishing apparatus 10.
The graph
shows a pre-burn period denoted P, a stabilising temperature period denoted ST
(which is
typically 90 seconds) and at the end of which the fire extinguishing apparatus
10 is
activated. Thereafter, the fire is extinguished within an extinguishing period
denoted E
which is typically less than 60 seconds and the container 12 is fully
discharged within a
discharge period denoted D which is typically greater than 90 seconds. During
the pre-
burn period the risk area typically reaches a temperature in excess of
300° C., which
temperature is maintained during the temperature stabilisation period ST.
Typically, the
temperature in the risk area is reduced to 60% of the temperature in the
stabilised
temperature and period ST before the container 12 is fully discharged.
Typically, the final
temperature within the risk zone is less than 250°C. The tests shown in
Figures 2 and 3
show that these results are achievable with the fire extinguishing apparatus
10 of the
present invention.
CA 02144540 2006-O1-09
22
The abovementioned tests were conducted using a cascade apparatus 200 shown
in Figure 5. The cascade tray 204 is designed to simulate fizel leaking onto a
hot
manifold. The cascade apparatus 200 comprises a relatively large box tray 202
having an
area of approximately 1 square metre, a flat cascade tray 204 having a surface
area of
approximately 0.5 square metres, upon which is located a relatively small box
tray 206.
The small box tray 206 has a plurality of holes 208 for allowing diesel from
the box tray
206 to fall onto the flat cascade tray 204. The cascade tray 204 has legs 210
spacing it
above the tray 202, and the tray 206 has legs 212 spacing it above the cascade
tray 204.
Typically, the tray 202 has petrol and/or isopropanol located in it. In use,
the cascade tray
204 becomes extremely hot and causes ignited fizel from the tray 206 to
explode and be
projected off the cascade apparatus 200.
A further test of the fire extinguishing apparatus 10 of the present invention
was
conducted in a risk area having a volume of SOOm3 (1 Om x lOm x Sm) with 190
of the
same nozzles 18 as used in the previous test. In this test 90 litres of fuel
was used having
an area of 7m2. The fuel was contained in the cascade tray 204 and 6 other
trays including
pool fires and a diesel oil pressure fire (representing a fire from a ruptured
fizel line). All
of the trays were ignited and allowed to burn for two minutes before
activation of the fire
extinguishing apparatus 10 of the present invention.
During the test it was observed that the colour of the combustion by-products
changed from thick black to white immediately the fire extinguishing apparatus
10 was
started. The results of the test was that all of the fires were extinguished
within 30
seconds and observers walked into the risk area before the completion of the
90 second
period over which the mist is released into the risk area. The observers
experienced no
difficulty in breathing during that time. It appears from this test that the
fire extinguishing
apparatus 10 led to suppression of smoke and causes combustion by-products to
fall out
of the air.
The spray flux density in this example can be readily calculated as follows.
The
nozzles 18 used in this test are the same nozzles as used in the previous
test, i.e. nozzles
CA 02144540 2006-O1-09
23
each having a capacity of 0.683 liter/min. The number of such nozzles 18 used
was 190
and the volume of the risk area was SOOm3. Accordingly, the spray flux density
is given
by:
spray flux density = (0.683 litre/min x 190) =SOOm3 = 0.26 litre/min/m3
The fire extinguishing apparatus 10 of the present invention has the advantage
that it can use water mist to fill a risk area so as to interrupt the flame
chain reaction in
the combustion cycle so as to prevent combustion within the risk area. Also,
the water
vapour has the effect of greatly reducing the heat within the risk area and
displacing
oxygen within the risk area due to the change in the state of the water from a
liquid to a
vapour (mist). Hence, the fire extinguishing apparatus 10 of the present
invention has the
surprising result that it can use a relatively small quantity of water to
extinguish a flame
caused by a relatively large quantity of highly flammable liquid. In Table 1
there is
shown a comparison of the benefits of the fire extinguishing apparatus 10 of
the present
invention (referred to as MISTEX) with conventional fire extinguishing
systems.
TABLE 1 - COMPARISONS
SPRINKLER HALON C02 MISTEX
NON-TOXIC YES NO NO YES
EXTINGUISH NO YES YES YES
A & B CLASS FIRES
ENVIRONMENTALLY YES NO NO YES
FRIENDLY
REQUIRED FIRE PUMP YES NO NO NO
LIGHT WEIGHT NO YES NO YES
CA 02144540 2006-O1-09
24
SERVICE ACCESSIBLE NO NO NO YES
BY CREW
HIGH HEAT YES NO NO YES
ABSORPTION
COST EFFECTIVENESS NO YES NO YES
RUNNING TIME N/A NO NO YES
(IN-BUILT SAFETY)
NO EVACUATION YES NO NO YES
PLAN REQUIRED
SERVICE AND REFILL N/A NO NO YES
COST EFFECTIVENESS
EFFECTIVE IN SEMI- YES NO NO YES
VENTILATED AREAS
Modifications and variations such as would be apparent to a skilled addressee
are
1 S considered within the scope of the present invention. For example, a
commercially
available heat absorber and fuel emulsifier could be added to the water to
increase its fire
extinguishing capabilities. Also, any form of fire detector could be used in
the fire
extinguishing apparatus, such as, for example, radioisotope based fire
detectors, ionic
chamber detectors, beam detectors, ultraviolet detectors or the like.
CONCLUSION
The foregoing has constituted a description of specific embodiments showing
how
the invention may be applied and put into use. These embodiments are only
exemplary.
CA 02144540 2006-O1-09
The invention in its broadest, and more specific aspects, is further described
and defined
in the claims which now follow.
These claims, and the language used therein, are to be understood in terms of
the
5 variants of the invention which have been described. They are not to be
restricted to such
variants, but are to be read as covering the full scope of the invention as is
implicit
within the invention and the disclosure that has been provided herein.
