A PRESENTATION

onInert Gas Extinguishing System

By: RAMESH KU. SHARMAMECHANICAL ENGINEER

Fire Protection in Electronics Areas (CR,CER,… )• Agent requirements

High efficiencyNon-toxicNon-damaging to equipmentNon-conductor of electricity

CLEAN AGENTSThe National Fire Protection Association (NFPA) defines, a “clean agent” as “an electrically non-conducting, volatile or gaseous fire extinguishant that does not have a residue upon evaporation”.

AS per NFPA-2001, Clean Agents can be classified into two categories:

H A L O C A R B O N S IN E R T G A S E S

C L E A N A G E N TS

Halocarbon agentsThis agent Contains one or more organic

compound containing one or more elements like Fluorine,Chlorine,Bromine or iodine.

These agents extinguish fire by combination of cooling action, oxygen depletion and chemical inhibition.

These agent are available with trade name as FM-200,FE13,CEA-410,NAF-Slll etc.FM-200 and NAF-Slll are used widely.

Halocarbon system safety disadvantageHalocarbon system safety disadvantage

HF for HumanHF for Human 10-minute human exposure to over 200 ppm can be lethal without 10-minute human exposure to over 200 ppm can be lethal without

medical intervention at increasing concentrationsmedical intervention at increasing concentrations

HF for PropertyHF for Property A computer card, after exposure to more than 500 ppm of HF, had a A computer card, after exposure to more than 500 ppm of HF, had a

total loss of functionalitytotal loss of functionality (by National Research Council Canada)(by National Research Council Canada)

Halocarbon gas produces Hydrogen Fluoride (HF) Halocarbon gas produces Hydrogen Fluoride (HF) that is corrosive byproduct from chemical reaction that is corrosive byproduct from chemical reaction with heat. with heat.

INERT GAS AGENTAn agent that contains as primary components one

or more of the gases helium, argon, nitrogen. Inert gas agents that are blends of gases can also contain CO2 as a secondary component.

INERGEN(IG-541)(N2-52%, ARGON -40%, CO2-8%) - TYCO USA, ANSUL USA, WORMOLD ASTRALIA.

ARGONITE (IG-55)(N2-50%, ARGON -50%)- GINGE-KERR, DENMARK.ARGOTEC (IG-01)( ARGON -100%)- MINIMAX,

GERMANYNITROGEN (IG-100)(N2-100%) - NOHMI BOSAI, JAPAN

OPERATING PRINCIPLE Inert gases extinguish fire by dilution of O2 concentration below

the level that does not support combustion.

Normal atmosphere in the room contains 21% oxygen.

To extinguish fire oxygen concentration should be less than 15%

Oxygen concentration less than 12% is not safe for human occupancy.

Inert gas bring down the O2 concentration in a protected space to around 12.5%, a level that is breathable but will not support flaming combustion.

safety for human and propertysafety for human and property

Human exposure time to low oxygen levelHuman exposure time to low oxygen level (from NFPA 2001)(from NFPA 2001)

Oxygen concentrationOxygen concentration Above 12%Above 12% 10 to 12%10 to 12% Below 10%Below 10%

Applicable roomApplicable room OccupiedOccupied OccupiedOccupied UnoccupiedUnoccupied

Limited human exposure timeLimited human exposure time 5 min.5 min. 3 min.3 min. 30 sec.30 sec.

Oxygen Inert gas Others

21% 78% 1%

12.5% 86.5% 1%

Before gas discharge

After gas dischargeComposition in the air

Inert gases used as extinguishing agent and puts out fire by Inert gases used as extinguishing agent and puts out fire by depleting oxygen concentration to around 12.5%depleting oxygen concentration to around 12.5%

Inert gas itself:Inert gas itself: Not toxicNot toxic No toxic byproduct generatedNo toxic byproduct generated

DESIGN FACTORS Design Concentration = flame extinguishing concen. X

S.F.

The flame extinguishing con. For Class ‘A’ fuels shall determined by test as part of a listing program (UL 2127).

For Class ‘A’ fuels: S.F. = 1.2 & For Class B Fuels = 1.3

Min. design con. For Class ‘C’ fire shall be atleast that for Class ‘A’ fire

DESIGN FACTORS The amount of inert gas agent required to achieve the

design con. : X (m3/m3) = ACF.(Vs/S)ln (100/100-C)

Where, ACF = Atmospheric correction factor =

P(hazard)/P(sea level)

• Discharge Time: Time required to discharge from the nozzles 95% of the agent mass necessary to achieve the min. design concentration.

Automatic Operation Fire signals from two detectors – beginning of extinguishing

sequence – PDI gives audio-visual indication in the hazard area.

Shutdown of A/C system & closure of fire dampers

Adjustable time delay for evacuation of people or to abort gas release function with the help of Abort switch.

Solenoid on the actuating/master cylinder valve energised – actuating cylinder valve opens – selector valve opens – storage cylinder valves open – Gas flows into protected space

Pressure Relief Damper SizePressure Relief Damper SizePressure relief openings During the flooding of a extinguishing zone with a gaseous extinguishing

agent this must be protected against positive pressure. This is carried out with pressure relief openings. The same mass flow resp.

flow rate (density-dependent), which is brought into the room via the gas extinguishing system, must to flow off through the opening.

A = 134 x Q / (P )½A = 134 x Q / (P )½A: Calculated area of Pressure A: Calculated area of Pressure Relief Damper [cm2]Relief Damper [cm2]Q: Maximum flow rate (= 1.6 x Q: Maximum flow rate (= 1.6 x design flow rate) [m3/min]design flow rate) [m3/min]P: Allowable strength of P: Allowable strength of enclosure [Pa]enclosure [Pa]

TOTAL FLOODING INERT GAS EXTINGUISHING SYSTEMADVANTAGESGases are environment friendly. Not subject to

thermal or chemical decomposition.Remote location of cylinders is possible.One bank of cylinders can protect more than one

hazard area which are separately located through directional valves

Cheap agent refill.Safe in occupied area, if discharged accidentally.Relatively simpler post-fire clean-up.

TOTAL FLOODING INERT GAS EXTINGUISHING SYSTEM DISADVANTAGESHealth and safety aspects should be obtained

from system provider for discharge with and without fire.

Requires much larger space for locating large number of cylinders.

Since a large volume of gas is introduced at high pressure, adequate venting has to be designed for protecting the equipment and room structure, especially glass.

CONCLUSIONINERT GAS SYSTEM APPEARS TO BE BETTERCHOICE IN COMPARISON TO HALOCARBONS

DUE TOFOLLOWING REASONS: INERT GAS WOULD BE EASILY AVAILABLE THROUGH OUT INDIA. REFILLING OF THE GAS WOULD ALSO BE EASY AND CHEAPER. INERT GAS BEING CLOSE TO NATURE, ITS

IMPACT ON ENVIRONMENT IS MINIMUM.

Environmental Health and Safety

THANK YOU