1 cxs490 chemical extinguishing system halocarbon extinguishing system

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CXS490 Chemical Extinguishing System

Halocarbon Extinguishing System

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Halons

1910, carbon tetrachloride startedto 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.

History

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Halons

Since about 1960, the twoagents widely used Halon 1301 & Halon 1211become more & morepopular for applicationsuntil the Montreal Protocol(the international agreement to protect ozone layer) stopped production in 1994 of halons & later of other ozone depleting substances.

History

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Halon Nomenclature System

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.

Naming Convention

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Halon Nomenclature System

FHalon 1301 F C Br Bromotrifluoromethane

CF3Br F

Halon 1211 F

CF2ClBr Cl C Br Bromochlorodifluoromethane F

F FHalon 2402 Br C C Br Dibromotetrafluoroethane

C2F4Br2 F F

Discuss - Carbon Tetrachloride (CCl4) &Methyl bromide (CH3Br)

Naming Convention

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Halon 1301 Exposure Limits

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 LevelLOAEL - Lowest Observed Adverse Effect Level

Human Exposure

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Halon 1301 Physical Properties

Boiling Point °F - 71.95Boiling Point °C - 58

Specific Volume 2.2062 + .005046 x t (Ft3/lbs) (t is °F)Specific Volume 0.1478 + 0.00057 x t (M3/Kg) (t is °C)

Vapour Pressure 199 psig@70°F

Halon Properties

k1 k2SV

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Halon Extinguishment 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 %

Extinguishing Mechanism

Primary

Secondary

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Halon 1301 Minimum Design Concentrations

Surface fires associated with the burning of solid material: 5%

Other Fuels Flame

Extinguishment InertingFuels (% by Volume) (% by volume)Acetone 5.0 7.6Benzene 5.0 5.0Ethylene 8.2 13.2Propane 5.2 6.7Methane 5.0 7.7

Where the possibility of achieving an explosive concentration of the fuel exits, the “Inerting Concentration” must be used.

Halon Design Concentration

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Discharge Duration10 seconds

To reduce increase of fire size &the resultant generation ofHF and HBr

True for Halocarbons & Halons

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Halon 1301 and the Environment

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.

Montreal Protocol

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Halon 1301 Design Standard

NFPA 12A is the applicable design standard for Halon 1301 systems.

Halon Standard

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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

New Technology Halocarbon Agents

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Halon Extinguishment Mechanism

The mechanism by which halocarbons extinguish fire is:

Cooling ~ 80 %Chain Breaking ~ 20 %

Halocarbon Extinguishing Mechanism

Primary

Secondary

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HALOCARBON DESIGN FACTORS - Specific Volume (Sv) Factors (*1)

Generic Trade k1 k2 k1 k2 Standard

Name Name Imperial units Imperial units SI units SI units (ISO)

(ft3/lb) (ft3/lb) (m3/kg) (m3/kg)

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

Halocarbon Extinguishing Agents

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This table illustrates the various requireddesign concentrations required (compared to halon 1301).

Halocarbon Extinguishing Agents - Design

HALOCARBON DESIGN FACTORS - Design Concentrations(*1)

Generic Name Trade Name

Minimum Class A Design Concentration Volume % (*2)

Minimum Class B Design Concentration Volume % (*2)

Inerting Concentration Methane/Air Volume % (#2)

ISOStandard

Halon 1301 Halon 1301 5 5 4.9 *HFC-23 (*1) FE-13 16.2 16.4 22.2 14520-10HFC-125 (*1) FE-25 11.2 12.1 - 14520-8HFC-227ea

(*1) FM 200 8.5 9.0 8.8 14520-9HFC-236fa (*1) FE-36 8.8 9.8 - 14520-11FK-5-1-12 (*1) Novec-1230 5.3 5.9 - 14520-5

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Halocarbon Exposure

NOAEL - No Observable Adverse Effect LevelLOAEL - 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.

HALOCARBON DESIGN FACTORS - Design Concentrations (*1)

Generic Name Trade NameNOAEL Volume% (*3)

LOAELVolume %

(*3)

Maximum Permitted Human Exposure

Concentration for 5 minutes (Occupied

Areas) Volume % (*4)

ISOStandard

Halon 1301 Halon 1301 5 7.5 5 *HFC-23 (*1) FE-13 30 >50 30 14520-10HFC-125 (*1) FE-25 7.5 10 10 14520-8HFC-227ea

(*1) FM 2009 10.5 10.5

14520-9HFC-236fa (*1) FE-36 10 15 12.5 14520-11FK-5-1-12 (*1) Novec-1230 10 >10 10 14520-5

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HALOCARBON ENVIRONMENTAL FACTORS

Generic Name Trade NameOzone

Depletion Potential

Global Warming Potential

(100 year)

Atmospheric Lifetime (years)

Halon 1301 Halon 1301 10 6,900 65HFC-23 (*1) FE-13 0 12,000 260HFC-125 (*1) FE-25 0 3,400 29HFC-227ea

(*1)FM 200 0 3,500 33

HFC-236fa (*1) FE-36 0 9,400 220FK-5-1-12 (*1) Novec-1230 0 1 0.01

New halocarbon agents do not posea threat to Stratospheric Ozone Layer.

Many have long atmospheric lifetimes andhigh global warming potential.

All, except FK-5-1-12 are substances included in the Kyoto Protocol on Climate Change.

Halocarbon Environmental

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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.

Halocarbon Technical Standards

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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.


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CO2 is not included as it is covered by other International Standards.


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All Gaseous system fire suppression NFPA standards assume the use of the standard by someone experienced in that area.


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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.

Halocarbon Technical Standards - NFPA 2001

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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.


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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.


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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.

Halocarbon Systems General Requirements

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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.


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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.


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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)

Design ofHalocarbon Systems

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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.

Design of Halocarbon Systems

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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.


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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


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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


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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


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8. Maximum discharge time : 10 seconds

9. Size of piping, # of nozzles, etc.: according to manufacturers' listed manual & computerized calculation programs


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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.


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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 areused as a second stage detectionmeans and automatic release onlyoccurs when a heat detection devicehas responded.


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Abort switches, when used, should beof “dead-man” type and installed onlywithin the protected area.

Manual pull stations should always becapable of overriding operation ofabort stations.

One manual release station should belocated outside of the protected enclosure.


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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.


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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.


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Halocarbon Calculation

Space with dimensions of11.43 m long by 10.69 m wideby 2.72 m high is to beprotected by Novec 1230.

The operating temperature range is 10 to 40OC.

Determine the required amount of agent and whether it is safe.

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Halocarbon CalculationDetermine necessary data input for agent

k1 = 0.0664 (p 14)k2 = 0.000274 (p14)c = 5.3 % (p 15)NOAEL = 10 (p 16)LOAEL = >10 (p 16)5 Minute Exposure = 10 (p16)

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Halocarbon CalculationWeight

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Halocarbon CalculationConcentration

Is it safe? Yes (why?).Less than the 10% (NOAEL & 5 minute human exposure)!

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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.


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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).


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For new technology halocarbon agentsrefer to either NFPA 2001 or ISO 14520.

For halon 1301Refer to NFPA 12A.

Acceptance Test

Design ofHalocarbonSystems

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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 space.

Inspection & Testing

Maintenance of Halocarbon Systems

1 cxs490 chemical extinguishing system halocarbon extinguishing system

Documents

br f halon

point f

halon extinguishment

history slide

digit number

br naming convention

f specific volume0

number of carbon atoms