CXS490 Chemical Extinguishing
System
Halocarbon Extinguishing System
1
Halons
History
1910, carbon tetrachloride started
to be used in a “glass grenade
("Pyrene") as an extinguishing agent.
Due to its toxicity and a number of accidents related to
its use, agent was prohibited as a fire extinguishant in
the late 50's.
1930, (same "family"), methyl bromide (CH3Br) began
use as extinguishing agent, but due to toxicity, its use
as extinguishing agent has been discontinued.
2
Halons
History
Since about 1960, the two
agents widely used
Halon 1301 & Halon 1211
become more & more
popular for applications
until the Montreal Protocol
(the international agreement to protect ozone
layer) stopped production in 1994 of halons &
later of other ozone depleting substances.
3
Halon Nomenclature System
Naming Convention
Halon system for naming halogenated hydrocarbons was devised
by U.S. Army Corps of Engineers to provide a convenient and
quick means of reference to candidate fire extinguishing agents.
• First digit (number) represents number of carbon atoms
in compound molecule;
• Second digit represents number of fluorine atoms;
• Third digit represents number of chlorine atoms;
• Fourth digit represents number of bromine atoms; and
• Fifth digit represents the number of iodine atoms.
In this system, terminal digits, if equal to zero, are not expressed.
4
Halon Nomenclature System
Naming Convention
Halon 1301
CF3Br
Halon 1211
CF2ClBr
Halon 2402
C2F4Br2
F
F C Br
F
Bromotrifluoromethane
F
Cl C Br
F
Bromochlorodifluoromethane
F F
Br C C Br
F F
Dibromotetrafluoroethane
Discuss - Carbon Tetrachloride (CCl4) &
Methyl bromide (CH3Br)
5
Halon 1301 Exposure Limits
Human Exposure
Original Concentration Guidelines:
up to 7%: < 15 minutes exposure
7 to 10%: < 1 minute exposure
(inhalation)
10 - 15%: < 30 seconds
> 15%: prevent inhalation exposure
Current Guidelines:
NOAEL (Volume %) - 5%
LOAEL (Volume %) - 7.5%
Maximum Permitted Human Exposure for 5 minutes - 5%
NOAEL - No Observable Adverse Effect Level
LOAEL - Lowest Observed Adverse Effect Level
6
Halon 1301 Physical Properties
Halon Properties
Boiling Point °F
Boiling Point °C
SV
Specific Volume
Specific Volume
- 71.95
- 58
k1
k2
2.2062 + .005046 x t
0.1478 + 0.00057 x t
(Ft3/lbs) (t is °F)
(M3/Kg) (t is °C)
Vapour Pressure 199 psig
@70°F
7
Halon Extinguishment Mechanism
Extinguishing Mechanism
The mechanism by which halons extinguish fire is not
completely understood.
However, it has been established that these products act by
"breaking" the chemical flame chain reaction.
Chain Breaking ~ 80 %
Cooling
~ 20 %
Secondary
Primary
8
Halon 1301 Minimum Design Concentrations
Halon Design Concentration
Surface fires associated with the burning of solid material: 5%
Other Fuels
Fuels
Acetone
Benzene
Ethylene
Propane
Methane
Flame
Extinguishment
(% by Volume)
5.0
5.0
8.2
5.2
5.0
Inerting
(% by volume)
7.6
5.0
13.2
6.7
7.7
Where the possibility of achieving an explosive concentration
of the fuel exits, the “Inerting Concentration” must be used.
9
Discharge Duration
10 seconds
To reduce increase of fire size &
the resultant generation of
HF and HBr
True for Halocarbons & Halons
10
Halon 1301 and the Environment
Montreal Protocol
CFC's and halons destroy the stratospheric ozone that
protects the earth from damaging ultraviolet radiation.
An international agreement - the Montreal Protocol - was
signed in September 1987 and was subsequently amended to
require a phase-out of halon production in developed countries
on January 1, 1994.
This environmental problem has had a major impact on the use
of halons.
No substitute is available at present that offers a “drop in
replacement” (same space and weight advantages) required
for applications such as on-board aircraft systems or use within
the crew compartments of military tactical vehicle.
11
Halon 1301 Design Standard
Halon Standard
NFPA 12A is the applicable design standard for Halon
1301 systems.
12
New Technology Halocarbon
Agents
New technology halogenated agents do not contain bromine
or chlorine and are fluorocarbons. Fires extinguished by the
cooling action required to fracture fluorocarbon molecule.
Less efficient on a weight/space basis than halon 1301 and
when exposed to fire they produce greater quantities of
hydrogen fluoride (HF) than halon 1301 did.
Stored in equipment that is similar to that used for halon 1301
systems, however flow rates are required to be slightly higher
to accomplish discharge within 10 seconds.
Where the possibility of achieving an explosive concentration
of the fuel exits, the “Inerting Concentration” must be used
13
Halon Extinguishment Mechanism
Halocarbon Extinguishing
Mechanism
The mechanism by which halocarbons extinguish fire is:
Cooling
Chain Breaking
~ 80 %
~ 20 %
Primary
Secondary
14
Halocarbon Extinguishing
Agents
HALOCARBON
DESIGN FACTORS Specific Volume
(Sv) Factors (*1)
Generic
Trade
Name
Name
k1
k2
k1
k2
Imperial units Imperial units SI units SI units
(ft3/lb)
(ft3/lb)
(m3/kg)
(m3/kg)
Standard
(ISO)
Halon 1301
Halon 1301
2.2062
0 .005046
0.1478
0.00057
HFC-23 (*1)
FE-13
4.7302
0.010699
0.3164
0.0012
14520-10
HFC-125 (*1)
FE-25
2.722
0.006376
0.1825
0.00073
14520-8
HFC-227ea (*1)
FM 200
1.879775
0.0046625
0.1269
0.000513
14520-9
HFC-236fa (*1)
FE-36
2.0978
0.00514
0.1413
0.0006
14520-11
FK-5-1-12 (*1)
Novec-1230
0.9856
0.002441
0.0664
0.000274
14520-5
15
Halocarbon Extinguishing
Agents - Design
This table illustrates the various required
design concentrations required (compared to halon 1301).
HALOCARBON DESIGN FACTORS - Design
Generic Name
Trade Name
Halon 1301
HFC-23 (*1)
HFC-125 (*1)
HFC-227ea (*1)
HFC-236fa (*1)
FK-5-1-12 (*1)
Halon 1301
FE-13
FE-25
FM 200
FE-36
Novec-1230
Concentrations (*1)
Minimum
Minimum Class
Class A DesignB Design
Concentration Concentration
Volume % (*2) Volume % (*2)
5
16.2
11.2
8.5
8.8
5.3
5
16.4
12.1
9.0
9.8
5.9
Inerting
Concentration
Methane/Air
Volume % (#2)
4.9
22.2
8.8
-
ISO
Standard
*
14520-10
14520-8
14520-9
14520-11
14520-5
16
Halocarbon Exposure
HALOCARBON DESIGN FACTORS - Design
Generic Name
Trade Name
Halon 1301
HFC-23 (*1)
HFC-125 (*1)
HFC-227ea (*1)
HFC-236fa (*1)
FK-5-1-12 (*1)
Halon 1301
FE-13
FE-25
FM 200
FE-36
Novec-1230
Concentrations (*1)
Maximum Permitted
NOAEL
LOAEL
Human Exposure
ISO
Volume
Volume %
Concentration for 5
Standard
% (*3)
(*3)
minutes (Occupied
Areas) Volume % (*4)
5
7.5
5
*
30
>50
30
14520-10
7.5
10
10
14520-8
9
10.5
10.5
14520-9
10
15
12.5
14520-11
10
>10
10
14520-5
NOAEL - No Observable Adverse Effect Level
LOAEL - Lowest Observed Adverse Effect Level
All halocarbon agents have a maximum discharge time is
10 seconds to minimize unwanted production of hydrogen
fluoride from flame contact by the agent.
17
Halocarbon Environmental
New halocarbon agents do not pose
a threat to Stratospheric Ozone Layer.
Many have long atmospheric lifetimes and
high global warming potential.
All, except FK-5-1-12 are substances included in the Kyoto
Protocol on Climate Change.
HALOCARBON
ENVIRONMENT
AL FACTORS
Global
Ozone
Atmospheric
Warming
Generic Name Trade Name Depletion
Lifetime
Potential
Potential
(years)
(100 year)
Halon 1301
Halon 1301
HFC-23 (*1)
FE-13
HFC-125 (*1)
FE-25
HFC-227ea (*1)
FM 200
HFC-236fa (*1)
FE-36
10
0
0
0
0
6,900
12,000
3,400
3,500
9,400
65
260
29
33
220
18
Halocarbon Technical
Standards
ISO 14520 and relevant sub-parts. ISO 14520 is not
applicable to explosion suppression. ISO 14520 is not
intended to indicate approval of the extinguishants listed
therein by the appropriate authorities, as other extinguishants
may be equally acceptable.
19
Halocarbon Technical
Standards
ISO 14520 specifies requirements and gives recommendations
for the design, installation, testing, maintenance and safety of
gaseous fire fighting systems in buildings, plant or other structures,
and the characteristics of the various extinguishants and types of
fire for which they are a suitable extinguishing medium.
It covers total flooding systems primarily related to buildings, plant
and other specific applications, utilizing electrically non-conducting
gaseous fire extinguishants that do not leave a residue after
discharge and for which there are sufficient data currently
available to enable validation of performance and safety
characteristics by an appropriate independent authority.
20
Halocarbon Technical
Standards
CO2 is not included as it is covered by other International
Standards.
21
Halocarbon Technical
Standards
All Gaseous system fire suppression NFPA standards assume
the use of the standard by someone experienced in that area.
22
Halocarbon Technical
Standards - NFPA 2001
Agents in standard were introduced in response to
international restrictions on the of certain halon fire
extinguishing agents under the Montreal Protocol signed
September 16, 1987, as amended.
Standard is prepared for the use and guidance of those
charged with purchasing, designing, installing, testing,
inspecting, approving, listing, operating, and maintaining
engineered (only) clean agent extinguishing systems, so that
such equipment will function as intended throughout its life.
23
Halocarbon Technical
Standards - NFPA 2001
Standard is intended to not restrict new technologies or
alternate arrangements provided the level of safety prescribed
by this standard is not lowered.
NFPA 2001 does not provide all the necessary criteria for the
implementation of a total flooding clean agent fire extinguishing
system. Technology in this area is under constant
development, and this will be reflected in revisions to this
standard. The user of this standard must recognize the
complexity of clean agent fire extinguishing systems.
Therefore, the designer is cautioned that the standard is not a
design handbook.
24
Halocarbon Technical
Standards - NFPA 2001
Standard on Clean Agent Fire Extinguishing Systems, is
available to Seneca students by following the link to the
Seneca Library from the My Seneca home page.
25
Halocarbon Systems General
Requirements
Halocarbon extinguishing systems are generally of the
total flooding type. The commonly used halocarbons
vapourize and mix with air very efficiently making
them ideal total flooding agents.
However these same characteristics make them
generally unsuitable for use in local application type
systems.
26
Halocarbon Systems General
Requirements
Total flooding halocarbon systems
Total flooding systems may be used where there is a fixed
enclosure about the hazard that is adequate to enable the
required concentration to be built up and maintained for
the required period of time to ensure the effective
extinguishment of the fire.
27
Halocarbon Systems General
Requirements
Two types:
1. Modular systems (agent storage at point of discharge)
Usually employs spherical containers connected to a maximum
of four nozzles by short length of pipe. Often use explosive
squibs for agent release (for valve opening). Different sizes of
containers may be used in a single hazard
2. Central Storage Piped Systems
Uses cylinders of equal size, containing equal weight of
halon. These cylinders are piped to a manifold, with check
valve at each manifold inlet connection.
28
Design of
Halocarbon Systems
The following elements have to be taken into account in the
design of a halocarbon system: (refer to NFPA 12A for halon
1301 and NFPA 2001 or ISO 14520 for new technology
halocarbon extinguishing systems)
1. Configuration of the hazard: dimensions (area, height,
volume) of the hazard, nature of the separation before the
risk and the surroundings areas. Volume used as a based for
the computation of the quantity of agent, the nature of the
enclosure will determine the extent of the protection (all
areas that may be involved in a single fire incident must be
simultaneously protected)
29
Design of Halocarbon Systems
2. Hazard ventilation: ventilation systems should be
automatically shut down upon system actuation.
3. Hazard fuels : fuel involved in the hazard must
be identified in order to determine the minimum
required concentration.
30
Design of Halocarbon Systems
4. Hazard temperature range: From a
given quantity of agent, the
concentration that will be achieved in a
given volume will vary with temperature
in this volume. The lowest temperature
is used to calculate minimum amount of
agent needed to obtain the required
concentration.
The highest hazard temperature is used
to verify that the maximum possible
concentration that could be obtained is
still acceptable for personnel safety.
31
Design of Halocarbon Systems
5. Specific Volume: The specific volume is calculated using
the following formula:
Sv units are m3/kg or ft3/lb
T is temperature in OC or OF
32
Design of Halocarbon Systems
6. Agent quantity: The required agent quantity is
calculated using the following mass formula:
Mass flooding formula:
where WLT = weight of halon
V
= enclosure volume
C
= Concentration
SvLT = specific volume
33
Design of Halocarbon Systems
7. Agent Concentration: The resulting agent concentration
calculated using the calculated weight from lowest
temperature and the specific volume from highest
temperature.
NOT REQUIRED IF NO TEMPERATURE VARIATION!
where C
= Concentration
WLT = weight of halon
V
= enclosure volume
SvHT = specific volume
34
Design of Halocarbon Systems
8. Maximum discharge time : 10 seconds
9. Size of piping, # of nozzles, etc.: according to manufacturers'
listed manual & computerized calculation programs
35
Design of Halocarbon Systems
10.
Detection and control:
A) Computer Rooms, Control Rooms,
Telecommunications Facilities,
Transformer vaults, etc.
Facilities often utilize high air change rates using conditioned air.
High air flow rates and chilled fresh air make it difficult to utilize
heat detection as the sole means of fire detection to cause
release of the halon. More often smoke detection devices are
used.
36
Design of Halocarbon Systems
In some cases, alarm from one such device will provide
warning to occupants and cause shut-down of air
handling systems.
Alarm from a second device of the same or similar type
results in automatic release of halocarbon.
In other cases, heat detectors are
used as a second stage detection
means and automatic release only
occurs when a heat detection device
has responded.
37
Design of Halocarbon Systems
Abort switches, when used, should be
of “dead-man” type and installed only
within the protected area.
Manual pull stations should always be
capable of overriding operation of
abort stations.
One manual release station should be
located outside of the protected enclosure.
38
Design of Halocarbon Systems
B) Hazards that include flammable liquids or gases
Detection devices should be of either the explosion
proof type or be intrinsically safe.
Heat detection devices or optical flame detection type
devices are most often used for fire detection in these
applications.
39
Design of Halocarbon Systems
It is not necessary that the control equipment and halon
system be of the same manufacturer, however, both the
NFPA 12A standard and the NFPA 2001 standard requires
that the control equipment and releasing devices are
compatible and that evidence of compatibility is provided.
40
Halocarbon Calculation
Space with dimensions of
11.43 m long by 10.69 m wide
by 2.72 m high is to be
protected by Novec 1230.
The operating temperature range is 10 to 40OC.
Determine the required amount of agent and
whether it is safe.
41
Halocarbon Calculation
Determine necessary data input for agent
k1
k2
c
NOAEL
LOAEL
5 Minute Exposure
0.0664
= 0.000274
= 5.3 %
= 10
= >10
= 10
=
(p 14)
(p14)
(p 15)
(p 16)
(p 16)
(p16)
42
Halocarbon Calculation
Weight
43
Halocarbon Calculation
Concentration
Is it safe?
Yes (why?).
Less than the 10% (NOAEL & 5 minute human exposure)!
44
Design of Halocarbon Systems
Plans shall be to an indicated scale and reproducible.
Sufficient detail to enable an evaluation of hazard and
the effectiveness of system. They shall show a detail of
the material involved in the hazard enclosure.
45
Design of Halocarbon Systems
Plan Details of system shall include:
•
•
•
•
•
•
•
•
•
information and calculations on amount of halon 1301
container storage pressure,
internal volume of the container(s) ,
location type and flow rate of each nozzle
(including equivalent orifice area)
location, size and equivalent length of pipe, fittings and hose
location of the storage containers
location and function of detection devices
Auxiliary equipment and
Electrical circuitry (if used).
46
Design of
Halocarbon
Systems
Acceptance Test
For new technology halocarbon agents
refer to either
For halon 1301
Refer to
NFPA 2001 or
ISO 14520.
NFPA 12A.
47
Maintenance of Halocarbon
Systems
Inspection & Testing
Annual: Complete inspection of system & non-destructive test
Semi-Annual: Check agent quantity and pressure
Every 5 Years: Hydrostatic test of all hoses
Frequency Approved schedule level: Visual inspection
It is also important to identify any change to the protected
space, such as, reconfigured layout, added ventilation, etc. to
ensure that installed system remains adequate for protected
48
space.