PPT ON FIRE FIGHTING SYSTEMS IN POWER STATIONS

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1.FIRE FIGHTING SYSTEMS IN POWER STATIONS

2.Fire – an introduction
Fire is a strange phenomenon
It behaves differently according to the combustible that fuels it.
And the environment in which it grows.
No two fire are the same.
However characteristics of two fires can be accurately identified when the two factors identified at a) and b) above are known.

3.The science of fire
There are four stages in development of a fire. They are:
Incipient stage ( seat of fire is very small & product of combustion is invisible)
Smoldering stage ( when smoke appears), rate of burn begins to increase at a more noticeable rate.
 flaming stage (flames appear)
Heat stage ( last stage)

4.The rate of development of fire through these stages varies dramatically depending on the nature of fire.
Fire can develop through these stages in fractions of a second as in case of an explosion.
While slower fires have known to smolder for days before breaking out.

5.For this reason heat detection is normally viewed as property protection startegy while smoke detection is applied strategically to protect lives.

6.Why, Where and How in a Power Station

7.Sources Of Ignition

8.Classification of Occupancies by TAC

9.Major Fires in Fire Stations
Obra Thermal Power Station
Koradi Thermal Power Station
HVDC Transmission System of Rihand Dadri Line.

10.Resources of Designer
CODES- National Fire Protection Association (NFPA), Tariff Advisory Committee (TAC), Beuro Of Indian Standards (BIS).
Insurance Agency
Feed Back From Operating Stn.
Latest Development in the Field.
Inert Gas System
Addressable Detection System
Multisensor Detectors

11.Fire Risk Areas
Fuel Oil Storage & Handling System.
Coal Storage And Handling System
Cable Galleries
Steam Generator /WHRB
Transformers

12.Fire Risk Areas- contd.
Lub Oil System
Generators
Control Room & CER
Air Pre-heaters
Gas Turbines
Gas Pressure Reducing Station

13.Type Of Detectors
Heat Detectors
Smoke Detectors
Flame Detectors

14.Heat Detectors
Advantages
Simplest
Least Expensive
Reliable
Lowest False Alarm Rate
Disadvantages
Slowest to Respond

15.Typical Heat Detectors are:
Quartzoid Bulb Detector
Spot Type Heat Detector
Linear Heat Sensing Cables
Infrared Heat Detector

16.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.

17.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

18.Smoke Detectors
Advantages
Fast Detection
Disadvantages
More Costly
Require More Maintenance
Higher False Alarm Rate

19.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

20.Smoke Detectors
Ionisation type Smoke Detector is more snsitive as compared to Photoelectric type Detector.

21.Ionisation type Detector
It is Responsive to both Visible and Invisible products of Combustion with very early response to Fires in the Incipient Stage
It can Detect Smoke Particles in the 0.01 to 10 Microne range .

22.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.

23.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
24.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)

25.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 at the 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

26.The cross-zoning principle was designed to avoid pouring expensive extinguishing chemicals into the room in a false fire scenario.

27.Flame Detectors
Flame Detectors
Very Sensitive
Expensive
28.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.

29.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

30.Detection
Protection
Annunciation
Central Fire Control Panel
31.Fire Protection
Agents
Should be most effective
Safest
Least damaging to particular operation or equipment
Pre-Planned
Equipment in Place
32.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.

33.Class - C
Electrical fires
Requires non conducting extinguishing agent with cooling, smothering or chemical inhibition characteristics

34.Class - D
Combustible Metal Fires e.g. Mg., Al, Na, K ETC.
Requires special Dry Powder which Blankets the Fire and Exclude the Oxygen.

35.Common Extinguishing Agents
Water
Oldest
Most Common
Abundant
In-expensive
Readily Available
Excellent Fire Extinguishing Properties

36.Easily Transported or Moved.
Has Sufficient Surface Tension to allow it to applied as a
Consolidated Stream
Discrete Water Droplets
Fog or Spray

37.Automatic Sprinklers & Electrical Fires
Characteristics of water spray pattern
Little danger of the transmission of hazardous current
Unlikely that personnel will be in the water discharge area when sprinkler activates.

38.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.

39.Design Criteria
Fire water storage and pumping system
Fire water storage capacity.
To meet simultaneous requirement of both hydrant and spray system
Storage provided/utilised from
Raw water reservoir
or RCC/ Steel over ground tank

40.Fire water pumps
Separate pumps for hydrant and spray system
Hydrant pumps
Capacity and head selected as per TAC
Atleast one diesel engine driven pump
Booster pump provided to meet minimum terminal pressure.

41.Spray pumps
Capacity selected considering the water required for largest risk area/ equipment.
At least one diesel engine driven pump
Jockey pumps  provided to keep the hydrant and spray system pressurised

42.Hydrant system provided through out the plant area to protect all the equipment/areas
Water monitors are provided near
ESP
Boiler area
TP’s of CHP
Coal conveyors
Coal stack yard
Fuel oil tank area

43.Classified in to MVW Spray and HVW Spary system
MVW Spray system
Spray density-10.2 LPM/SQ.M.
Terminal pressure- 1.4KG/CM2
HVW Spray system
Spray density- 10.2 LPM/SQ.M.
Terminal pressure- 3.5KG/CM2

44.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

46.Coal conveyors
Transfer points and crusher houses
Fuel oil tanks (NAPHTHA/NGL/HSD)
Fuel oil pump house eqpts.
Steam turbine bearing housing

47.Turbine oil tanks,coolers and purifiers
Turbine lube oil pipes
Boiler burner fronts
All transformers in transformer yard and transformers of 10MVA and above in other areas in the plant.
Oil canals

48.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 in the 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 for cleaning and floor washing.

49.Such a practice is very dangerous
May result in inadequate pressure at place of fire 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 being provided. ( earlier it was 20 to 30 Cum./Hr. now it is about 75 Cum./hr.)

50.HALON 1301- Meet all the above
Used as a total flooding agent
OBRA FIRE IN 1983
Cause for introduction of agent in NTPC

51.-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.

52.ENVIRONMENTAL IMPACT
In 1991 due to adverse environmental impact - further use of HALON was discontinued.

53.HALON PHASE OUT
In view of environmental considerations, its use 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 EQUIPMENT ROOM (C.E.R.)

54.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.

55.Since use of HALON was discontinued, the projects after 1991 were not provided with any fixed type fire protection system.
THE LIST OF PROJECTS, NOT PROVIDED WITH ANY FIXED FIRE PROTECTION SYSTEM, IS SHOWN ON NEXT SLIDE.

56.STATUS OF FIRE PROTECTION IN U.C.R. AND C.E.R. FOR PROJECTS EXECUTED SINCE 1991

57.STATUS OF NTPC PROJECTS

58.The issue of fire protection system in control rooms and control equipment rooms was once again reviewed in NTPC in 1999
59.FIXED FIRE PROTECTION SYSTEM FOR CCR & CER REQUIRED?
60.FIXED FIRE PROTECTION SYSTEM FOR CCR & CER REQUIRED?

61.FIXED FIRE PROTECTION SYSTEM FOR CCR & CER REQUIRED?

62.National Fire Protection Association (NFPA) USA has published a code NFPA-2001. This code covers clean agent fire extinguishing system as an alternative to HALON.

63.NFPA-2001,1996 MADE AVAILABLE FOR CLEAN AGENT SYSTEMS

64.COMPARISON OF CLEAN AGENTS
HALOCARBONS
Physical charact-eristics
CHEMICAL
SPEED OF  EXTING-UISHING
Fast since total agent discharge is in 10 sec.             

65.COMPARISON OF CLEAN AGENTS

66.COMPARISON OF CLEAN AGENTS

67.COMPARISON OF CLEAN AGENTS

68.HALOCARBONS
ADVANTAGES:
FAST FIRE EXTINGUISHING CAPABILITY
RELATIVELY SMALL STORAGE REQUIREMENT
IMPLICATIONS:
HEALTH AND SAFETY ASPECTS SHOULD BE OBTAINED FROM SYSTEM PROVIDER FOR DISCHARGE WITH AND WITHOUT FIRE.

69.IN THE PROCESS OF EXTINGUISHING A FIRE, SMALLER MOLECULES LIKE HF, COCl2 ARE PRODUCED WHICH ARE TOXIC AND CORROSIVE IN HIGH ENOUGH DOSES.
CYLINDERS HAVE TO BE LOCATED VERY NEAR TO THE AREA PROTECTED.
THE DESIGN CONCENTRATION OF GAS IN CASE OF DESCHARGE IN THE ENCLOSURE CAN NOT BE HELD FOR MORE THAN 10 MINUTES. HENCE POSSIBILITY OF RE-IGNITION OF FIRE.

70.Halocarbon  is a chemical agent. Hence, possibility of its use being banned or restricted in future can not be ruled out.

71.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.

72INERT GAS
ADVANTAGES:
Gases 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

73.Cheap agent refill.
Safe in occupied area, if discharged accidentally.
Minimal fogging in protected enclosure on discharge. Hence, good visibility inside the room allowing easy escape.
Relatively simpler post-fire clean-up.

74.IMPLICATIONS
Health and sfety aspects shold 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.

75.FM-200 - GREATLAKE CHEMICALS, USA
NAF-SIII- NORTH AMERICAN FIRE        GUARDIAN , CANADA, ITALY
FE-13 - Du PONT
CEA-410

76.They are all chemicals
NAF-SIII- Has small ODP
Proprietary in nature
Refilling is expensive
Directional valves can not be used- expensive
Availability in india, FM-200 M/S Kidde, NAF-SIII STEELAGE , AGNICE

77.INERT GASES
NOAEL - NO OBSERVED ADVERSE EFFECT LEVEL - O2 LEVEL OF 12% AGAINST NORMAL ATMOSPHERE O2 LEVEL OF 21%
LOAEL - LOWEST OBSERVED ADVERSE EFFECT LEVEL - O2 LEVEL 10%.
TO EXTINGUISH THE FIRE O2 CONCENTRATION SHOULD BE
LOWER THAN 15%
NOT LOWER THAN 12% TO PERMIT THE PROTECTED AREA TO BE OCCUPIED.
CO2 CONCENTRATION CAN BE UP TO 4% AGAINST NORMAL LEVEL OF LESS THAN 1% IN ATMOSPHERE.

78.INERGEN(N2-52%, ARGON -40%, CO2-8%)
ARGONITE (N2-50%, ARGON -50%)
ARGOTEC ( ARGON -100%)
NITROGEN (N2-100%)

79.These are mixture of freely available gases in atmosphere
System design is proprietary
Refilling is cheaper
Requires more cylinders
Directional valves can be used.

80.Cylinders can be located at one place
Refilling can be done at any authorised air separation unit e.g. SUPERIOR AIR PRODUCTS, BRITISH OXYGEN ETC.

81.INERGEN - AVAILABLE FROM TYCO USA, ANSUL USA, WORMOLD AUSTRALIA.
ARGONITE - GINGE-KERR, DENMARK.
ARGOTEC - MINIMAX, GERMANY
NITROGEN - NOHMI BOSAI, JAPAN

82.All indian F.P. Suppliers can supply any of the above system.
Due to its advantages NTPC has decided to go in for inert gas systems for all its projects.

83.SCHEME OF INERT GAS SYSTEM

84.MONTREAL PROTOCOL

85.SCHEME FOR HALOCARBONS

86.CONCLUSION
INERT GAS SYSTEM APPEARS TO BE BETTER CHOICE IN COMPARISON TO HALOCARBONS DUE TO FOLLOWING REASONS:
A)INERT GAS WOULD BE EASILY AVAILABLE THROUGH OUT INDIA. REFILLING OF THE GAS WOULD ALSO BE EASY AND CHEAPER.
B)INERT GAS BEING CLOSE TO NATURE, ITS IMPACT ON ENVIRONMENT IS MINIMUM.