fire fighting systems in power stations
TRANSCRIPT
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FIRE FIGHTINGSYSTEMS IN POWER
STATIONS
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Why, Where and How in a
Power Station
Basics of Combustion Process
Fire Tetrahedron
Oxygen
Fuel Heat of Ignition
Chain Reaction to Sustain Fire
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Sources Of Ignition
Electricity
Smoking
Incendiarism (strike, sabotage)
Cutting & Welding
Friction
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Classification of Occupancies by TAC
Light Hazard
Ordinary Hazard
High Hazard Electric
Generating
Station
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Major Fires in Fire Stations
Obra Thermal Power Station
Koradi Thermal Power Station
HVDC Transmission System of Rihand Dadri
Line.
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Resources of Designer
CODES- National Fire Protection Association(NFPA), Tariff Advisory Committee (TAC), Beuro OfIndian Standards (BIS).
Insurance Agency
Feed Back From Operating Stn. Latest Development in the Field.
Inert Gas System
Addressable Detection System
Multisensor Detectors
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Fire Risk Areas
Fuel Oil Storage & Handling System.
Coal Storage And Handling System
Cable Galleries
Steam Generator /WHRB
Transformers
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Fire Risk Areas- contd.
Lub Oil System
Generators
Control Room & CER
Air Pre-heaters
Gas Turbines
Gas Pressure Reducing Station
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Type Of Detectors
Heat Detectors
Smoke Detectors
Flame Detectors
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Heat Detectors +/-
Heat Detectors
Advantages
Simplest
Least Expensive Reliable
Lowest False Alarm Rate
Disadvantages
Slowest to Respond
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Heat Detectors in Power Station
Typical Heat Detectors are:
Quartzoid Bulb Detector
Spot Type Heat Detector
Linear Heat Sensing Cables
Infrared Heat Detector
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LHSC & Infra-red detectors
LHSC – Heat sensing cable comprises of
two conductors encased in heat sensitive
material Infra-red – Detects moving fires
Responds to “Infra-Red Band” of
Electromagnetic radiation
- Provided on conveyors coming from coal
stockyard
- going to coal bunkers.
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Use Of Heat Detectors
Used For Detection Of Fires In
Transformers
Coal Handling Plant
Fuel Oil Storage And Handling Plants
Boiler Burner Fronts
Lub Oil Storage Facilities
Battery Rooms
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Smoke Detectors +/-_
Smoke Detectors
Advantages
Fast Detection
Disadvantages More Costly
Require More Maintenance
Higher False Alarm Rate
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Other Details of Smoke Detectors
Types Are
Ionisation
Photoelectric
Multisensor
Used In
Control Rooms
Control Equipment Rooms
Office Areas
MCC/Switch Gears Rooms
Cable Galleries
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Smoke Detectors
Ionisation type Smoke Detector is more
snsitive as compared to Photoelectric type
Detector.
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Smoke Detectors
Ionisation type Detector
It is Responsive to both Visible and
Invisible products of Combustion with
very early response to Fires in theIncipient Stage
It can Detect Smoke Particles in the 0.01
to 10 Microne range .
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Ionization Detectors
Detector consists of ionizing chamber with
radio-active source
Smoke/Fire changes current in the ionization
chamber Used for general office application
To avoid the use of radioactive element, these
detectors have now been replaced with Multi-Sensor type detectors.
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Smoke Detectors
Optical/ Photoelectric
It is responsive to visible smoke
It can detect smoke particles in the
range of 0.5 to 10 microne
It is useful where an ionisation sensor is
too sensitive
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Photo-electric detector
Sensing element is an optical chamber
On fire/smoke, the light scattered in the
optical chamber varies Smolder fires (Suitable for PVC fire)
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History of smoke detection
Early version of smoke detector 1896
• Involved two birds in a cage
• When overcome by fumes, would fall into a funnel atthe bottom of their cage.
• The weight of their bodies would activate a circuit and
register an alarm.• Two birds were used so that in the event one died of
natural cause; the detector would not be triggered.
• This was the earliest form of false alarm protection
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The cross-zoning principle was designed to
avoid pouring expensive extinguishing
chemicals into the room in a false fire scenario.
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Addressable Analog Detection
System-1
Microprocessor based
Smart & intelligent
Any kind of Detector or Alarm may be
incorporated
Detectors are monitored every 3 seconds
including their status, sensitivity etc.
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Addressable Analog Detection
System-2
Based on above programmed action can be
taken by panel e.g.
Transmit Alarm
Closing Doors Suppression System
Printing records
Can Analyse & Adjust Sensitivity of Detector
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Components of Fire Alarm System
Detection
Protection
Annunciation Central Fire Control Panel
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Fire Protection
Agents
Should be most effective
Safest
Least damaging to particular operation orequipment
Pre-Planned
Equipment in Place
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Classification of Fires
Class-A
ORDINARY COMBUSTIBLES e.G. Wood,
Paper, Cloth& Plastics
Requires Cooling & Quenching Class-B
Flammable liquid e.g. Gasoline, Oil, Paints
Etc.
Requires Blanketing,Smothering Or Chemical
Inhibition.
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Classification of fires-contd.
Class - C
Electrical fires
Requires non conducting extinguishing agent
with cooling, smothering or chemical inhibitioncharacteristics
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Classification of Fires-contd
Class - D
Combustible Metal Fires e.g. Mg., Al, Na, K
ETC.
Requires special Dry Powder which Blanketsthe Fire and Exclude the Oxygen.
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Common Extinguishing Agents
Water
Oldest
Most Common
Abundant
In-expensive
Readily Available
Excellent Fire Extinguishing Properties
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Common Extinguishing Agents-contd.
Easily Transported or Moved.
Has Sufficient Surface Tension to allow it to
applied as a
Consolidated Stream Discrete Water Droplets
Fog or Spray
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Automatic Sprinklers & Electrical Fires
Characteristics of water spray pattern
Little danger of the transmission of hazardous
current
Unlikely that personnel will be in the waterdischarge area when sprinkler activates.
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Design aspects
Hydrant works as the back bone
Spray/sprinkler system provided for automatic
protection of transformers, coal handling plant,
cable galleries, fuel oil and transfer areas.
Foam protection system for fuel oil tanks,
Total flooding inert gas system for electronic
areas.
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TO SPRAYSYSTEM
TO HYDRANT
SYSTEM
FIRE WATER
STORAGE TANKS
JP
HP-
MD
SP-
DD
SP-
MD
HP-
MD
HP-
DD
JP- JOCKEY PUMP
HP- HYDRANT PUMP.
SP- SPRAY PUMP
MD- MOTOR DRIVEN.
DD- DIESEL ENGINE
DRIVEN
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MVW SPRAY SYSTEM
Provided to protect
Cable galleries/cable vault of
Main plant
ESP/ VFD building CHP control room
Switchyard control room
Cable galleries provided in any other area
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MVW SPRAY SYSTEM-Contd.
Coal conveyors
Transfer points and crusher houses
Fuel oil tanks (NAPHTHA/NGL/HSD)
Fuel oil pump house eqpts. Steam turbine bearing housing
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HVW SPRAY SYSTEM
Turbine oil tanks,coolers and purifiers
Turbine lube oil pipes
Boiler burner fronts
All transformers in transformer yard andtransformers of 10MVA and above in other
areas in the plant.
Oil canals
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General comments
Hydrant system is kept pressurised using Hydro-pneumatic tank, air compressors and jockey pumps.
Hydro-pneumatic tank works as a surge tank.
Air compressor helps in maintaining adequate pressure inthe system.
Jockey pump helps in meeting minor losses. Above system would work, if hydrant system is not used
for any other purpose.
It is observed that at site hydrant system is used forcleaning and floor washing.
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Such a practice is very dangerous
May result in inadequate pressure at place offire in emergency situation.
To overcome this problem Independent service water system with pumps
and piping network is being provided.
Jockey pump of higher capacity is beingprovided. ( earlier it was 20 to 30 Cum./Hr.now it is about 75 Cum./hr.)
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FIRE PROTECTION OFCONTROL ROOMS AND
CONTROL EQUIPMENTROOMS
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BACKGROUND
-Devastating fire at OBRA TPS IN OCTOBER1983
-C.E.A. Circulated the measures to be adopted
in fire fighting system in power stations.
-Recommendations-use Halon-1301 in control
room areas by total flooding system.
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BASIC REQUIREMENT
•These are electronic areas
• Agent requirements•High efficiency
•Non-toxic
•Non-damaging to equipment
•Non-conductor of electricity
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INTRODUCTION IN NTPC
HALON 1301- Meet all the above
Used as a total flooding agent
OBRA FIRE IN 1983
Cause for introduction of agent in NTPC
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-HALON-1301, an excellent fire extinguishing
agent,
- For total flooding application
- Safe for use in manned areas
- Harmless to equipment.
-Accordingly, HALON-1301 gas was introduced in
NTPC For protection of CONTROL EQUIPMENT
ROOM (C.E.R.) and UNIT CONTRL ROOM (U.C.R.)
in 1984.
Subsequently all NTPC Projects at that time were
provided with HALON-1301.
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ENVIRONMENTAL IMPACT
In 1991 due to adverse environmental impact
- further use of HALON was discontinued.
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HALON PHASE OUT
• In view of environmental considerations, itsuse was reviwed in NTPC in 1991 and it was
decided not to specify HALON System for
ongoing and future projects.
• Accordingly, only portable extingushers
were provided for control room and modular
CO2 Injection system was to be explored for
individual panels in CONTROL EQUIPMENTROOM (C.E.R.)
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• CO2 Injection system was not found suitable
because of objection raised by panel
manufacturers.
• Hence this system has not been provided in any
NTPC Projects for U.C.R. AND C.E.R.
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The issue of fire protection system in
control rooms and control equipmentrooms was once again reviewed in NTPC
in 1999
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National Fire Protection Association (NFPA)
USA has published a code NFPA-2001.
This code covers clean agent fireextinguishing system as an alternative to
HALON.
CLEAN AGENTS NOW AVAILABLE
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NFPA-2001
NFPA-2001,1996 MADE AVAILABLE FOR
CLEAN AGENT SYSTEMS
HALOCARBONS INERT GASES
CLEAN AGENTS
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COMPARISON OF CLEAN AGENTS
HALOCARBONS
Physical charact-eristics
CHEMICAL
SPEED OF EXTING-
UISHING Fast since total
agent discharge is in
10 sec.
INERT GAS Physical charact-eristics
INERT GAS
SPEED OF EXTING-UISHING
Relatively slower
since total gas
discharge time is
about 60 sec.
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COMPARISON OF CLEAN AGENTS
HALOCARBONS
Design concen-tration
to extinguish fire
7%
INERT GAS
Concentration required
to extinguish fire
34%
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COMPARISON OF CLEAN AGENTS
HALOCARBONS
CYLINDER STORAGE
4 TIMES MORE THAN
HALON
CYLINDER
PRESSURE
25 TO 40 BAR
INERT GAS
CYLINDER STORAGE
10 TIMES MORE
THAN HALON
CYLINDER
PRESSURE
150 TO 300 BAR
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COMPARISON OF CLEAN AGENTS
HALOCARBONS
GAS DISCHARGE
PRESSURE
5 BAR
VENTING DESIGN
NOT SIGNIFICANT
INERT GAS
GAS DISCHARGE
PRESSURE
25 BAR SPECIAL CARE IS TO BE
TAKEN IN ENCLOSURE
DESIGN WITH RESPECT
TO VENTING
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COMPARISON OF CLEAN AGENTS
HALOCARBONS
Location of cylinder:
should not be more
than 20m away from
the risk
INERT GAS
Can be loacted 150m
away from the risk
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COMPARISON OF CLEAN AGENTS
HALOCARBONS
No. of cylinder banks -
each bank can
serve only one fire risk
Refill cost very high
INERT GAS
One bank can serve a
number of fire risks
using directional valve
Refill cost cheap
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COMPARISON OF CLEAN AGENTS
HALOCARBONS
Undergoes thermal and
chemical decomposition
while extinguishing fire
INERT GAS
Not subject to any
decomposition.
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Halocarbon is a chemical agent. Hence,
possibility of its use being banned orrestricted in future can not be ruled out .
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INERT GASES
Normal level of oxygen -21% in atmosphere
To extinguish fire oxygen concentration should be less
than 15%
Oxygen concentration less than 12% is not safe for
human occupancy.
Inert gas reduces oxygen concentration ( to less than
15% but more than 12% and extinguish fire.
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HALOCARBONS-1
FM-200 - GREATLAKE CHEMICALS, USA
NAF-SIII- NORTH AMERICAN FIRE
GUARDIAN , CANADA, ITALY
FE-13 - Du PONT
CEA-410
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INERT GASES-1
INERGEN(N2-52%, ARGON -40%, CO2-8%)
ARGONITE (N2-50%, ARGON -50%)
ARGOTEC ( ARGON -100%)
NITROGEN (N2-100%)
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INERT GASES-1
These are mixture of freely available gases in
atmosphere
System design is proprietary
Refilling is cheaper Requires more cylinders
Directional valves can be used.
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INERT GASES-3
INERGEN - AVAILABLE FROM TYCO USA,
ANSUL USA, WORMOLD AUSTRALIA.
ARGONITE - GINGE-KERR, DENMARK.
ARGOTEC - MINIMAX, GERMANY NITROGEN - NOHMI BOSAI, JAPAN
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MONTREAL PROTOCOL
For India - eliminate HALON Consumption
completely by developing safer alternatives
by 2010.
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TH NK YOU
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