Fire Protection :
sprinkler Systems:
A
sprinkler system is an integrated system of underground and overhead piping,
designed in accordance with fire protection engineering standards, and
connected to one or more automatic water supplies. The system is usually
activated by heat from a fire, and the sprinkler heads then discharge water
over the fire area. Sprinkler systems are nearly 100 percent effective. Many
sprinkler systems are supervised electrically from a central station, and
alarms are transmitted to a fire department whenever the sprinklers operate or
when a valve in the sprinkler system closes for any reason. If a fire-fighting
unit arriving at a fire finds that the sprinkler system is not receiving
sufficient water and pressure, a pumper is connected to the sprinkler system to
supply additional water.
Standpipe Systems:
Many
high-rise or other large buildings have an internal system of water mains
(standpipes) connected to fire-hose stations. Trained occupants or employees of
the building management operate the hoses until the fire department arrives.
Fire fighters can also connect their hoses to outlets near the fire.
Fire Extinguisher
I INTRODUCTION
Fire Extinguisher, portable device used to put out
fires of limited size. Such fires are grouped into four classes, according to
the type of material that is burning. Class A fires include those in which
ordinary combustibles such as wood, cloth, and paper are burning. Class B fires
are those in which flammable liquids, oils, and grease are burning. Class C
fires are those involving live electrical equipment. Class D fires involve
combustible metals such as magnesium, potassium, and sodium. Each class of fire
requires its own type of fire extinguisher.
Standards for the selection, placement, and testing of
portable fire extinguishers are issued by the National Fire Protection
Association, a nonprofit technical and educational organization in Quincy,
Massachusetts. The standards establish the minimum requirements for all types
and sizes of extinguishers that are listed and rated by testing laboratories
against standard test fires of the types they are designed to control. Each
extinguisher is rated as to both type and size of the fire extinguished. For
example, a 20-B extinguisher should extinguish a flammable-liquids fire that is
20 times the size of a fire that an extinguisher rated 1-B would extinguish.
Extinguishers that cannot extinguish the minimum size test fires are not listed
or rated. Some extinguishers will put out only one class of fire; others are
used for two or even three classes; none is suitable for all four classes.
Fire extinguishers may go unused for many years, but
they must be maintained in a state of readiness. For this reason, periodic
inspection and servicing are required, and that responsibility rests with the
owner. Fire department inspectors check at periodic intervals to see that
extinguishers are present where required by law and that they have been
serviced within the specified time period.
II EXTINGUISHERS FOR
CLASS A FIRES
Class A fire extinguishers are usually water based.
Water provides a heat-absorbing (cooling) effect on the burning material to
extinguish the fire. Stored-pressure extinguishers use air under pressure to
expel water. Pump-tank extinguishers are operated by a hand pump.
III EXTINGUISHERS FOR CLASS
B FIRES
Class B fires are put out by excluding air, by slowing
down the release of flammable vapors, or by interrupting the chain reaction of
the combustion. Three types of extinguishing agents—carbon dioxide gas, dry
chemical, and foam—are used for fires involving flammable liquids, greases, and
oils. Carbon dioxide is a compressed gas agent that prevents combustion by
displacing the oxygen in the air surrounding the fire. The two types of dry
chemical extinguishers include one that contains ordinary sodium or potassium
bicarbonate, urea potassium bicarbonate, and potassium chloride base agents;
the second, multipurpose, type contains an ammonium phosphate base. The
multipurpose extinguisher can be used on class A, B, and C fires. Most dry
chemical extinguishers use stored pressure to discharge the agent, and the fire
is extinguished mainly by the interruption of the combustion chain reaction.
Foam extinguishers use an aqueous film forming foam (AFFF) agent that expels a
layer of foam when it is discharged through a nozzle. It acts as a barrier to
exclude oxygen from the fire.
IV EXTINGUISHERS FOR CLASS
C FIRES
The extinguishing agent in a class C fire extinguisher
must be electrically non-conductive. Both carbon dioxide and dry chemicals can
be used in electrical fires. An advantage of carbon dioxide is that it leaves no
residue after the fire is extinguished. When electrical equipment is not
energized, extinguishers for class A or B fires may be used.
V EXTINGUISHERS FOR CLASS
D FIRES
A heat-absorbing extinguishing medium is needed for
fires in combustible metals. Also, the extinguishing medium must not react with
the burning metal. The extinguishing agents, known as dry powders, cover the
burning metal and provide a smothering blanket.
The Underwriters' Laboratories, Inc., has available
lists of approved fire extinguishers that may be purchased from different
manufacturers. The extinguisher label gives operating instructions and
identifies the class, or classes, of fire on which the extinguisher may be used
safely. Approved extinguishers also carry the labels of
the laboratories at
which they were tested.
Fire Safety During Constructions :
1. General:
Buildings under
construction shall be in accordance with this Section.
2. Access
Roads:
Fire Department access
roads shall be established and maintained in accordance with Section 902 of
this code, as the building is constructed, before it exceeds grade level and
before the walls are erected.
2.a
Exception:
When approved by the fire chief, temporary access roads of a
width, vertical clearance, and surface such as to permit access by fire
department apparatus may be permitted only until permanent roads are installed.
3. Gradient:
The gradient for a fire apparatus access roadway shall
not exceed a maximum of 6 percent (6%) unless specifically approved for that
site by the fire chief.
4. Water
Supply:
Water mains and hydrants shall be installed and be
operational in accordance with Fire Fighting Systems Code, as the building is
being constructed, before it exceeds grade level and before the walls are
erected.
4.a
Exception:
When approved by the fire chief,
a temporary water supply for fire protection may be permitted, pending
installation of permanent fire protection systems.
5. Fire
Protection:
5.a General:
During the construction of a
building and until the permanent fire extinguishing system has been installed
and is in service, fire protection shall be provided in accordance to Section
8704.
5.b Fire
Extinguishers:
Fire Extinguishers shall be
provided for buildings under construction when required by the chief. The
number and type of extinguishers shall be as required by the chief, and the
type of extinguisher shall be suitable for the type of fire associated with the
hazards present.
5.c Standpipes:
5.c.1 Where
Required:
Every building with a
floor level that is located more than 55 feet above the lowest level of fire
department access or having more than three stories, whichever is less, shall
be provided with not less than one standpipe for use during construction. Such
standpipe shall be provided with fire department hose connections at accessible
locations adjacent to usable stairs and the standpipe outlets shall be located
adjacent to such usable stairs. Such standpipe systems shall be extended as
construction progresses to within one floor of the highest point of
construction having secured decking or flooring.
On each floor there shall be provided one minimum 2-1/2 inch valve
outlet for fire department use.
5.c.2
Temporary Standpipes:
Temporary standpipes are allowed to be provided in place of permanent
systems if they are designed to furnish 500 gallons of water per minute at 50
pounds per square inch pressure with a standpipe size of not less than 4
inches.
5.c.3
Detailed Requirements:
Standpipe systems for buildings
under construction shall be installed as required for permanent systems.
6.
Combustible Debris:
Combustible debris shall not be accumulated within buildings.
Combustible debris, rubbish and waste material shall be removed from buildings
as often as practical. Combustible debris, waste material and trash shall not
be burned on site unless approved.
7. Motor
Equipment:
Internal-combustion powered construction equipment shall be used in
accordance with the following:
1.
Equipment shall be located so that exhausts do not discharge against
combustible material,
2.
When possible, exhausts shall be piped to the outside of the building,
3.
Equipment shall not be refueled while in operation, and
4.
Fuel for equipment shall be stored in an approved area outside of the
building.
8. Heating
Devices:
Temporary heating devices shall be of a type approved by the chief,
located away from combustible materials, and attended and maintained by
competent personnel.
9. Smoking:
Smoking shall be prohibited, except in those areas approved by the
Chief. When required by the chief, a suitable number and type of NO SMOKING
signs shall be posted.
10. Cutting
and Welding:
Cutting and welding operations shall be in accordance with the code.
11. Flame-producing Equipment:
The use of torches or flame-producing devices for the sweating of pipe
joints shall be in accordance with Article code.
12.
Flammable Liquids:
The storage, use and handling of flammable liquids shall be in
accordance with Article 79. Ventilation shall be provided for operations
utilizing the application of materials containing flammable solvents.
13.
Open-flame Devices:
Open-flame devices and other sources of ignition shall not be located
in areas where flammable materials are being used.
14. Asphalt
and Tar Kettles:
Asphalt and tar kettles shall be located and operated in accordance
with this code.
15.
Temporary Electrical Wiring:
Temporary electrical wiring shall be in accordance with this code.
16. Building
Access:
When required by the chief,
access to buildings for the purpose of fire fighting shall be provided.
Construction material shall not block access to buildings, hydrants or fire
appliances.
17.
Emergency Telephone:
When required by the chief, telephone facilities shall be provided at
the construction site for the purpose of emergency notification of the fire
department. The street address of the construction site shall be posted
adjacent to the telephone together with the fire department telephone number.
18. Fire-protection
Plan:
When required by the chief, a fire-protection plan shall be
established.
Fire, heat and light resulting from the rapid combination of
oxygen, or in some cases gaseous chlorine, with other materials. The light is
in the form of flame, which is composed of glowing particles of the burning
material and certain gaseous products that are luminous at the temperature of
the burning material. The conditions necessary for the existence of fire are
the presence of a combustible substance, a temperature high enough to cause
combustion (called the ignition temperature) and the presence of enough
oxygen (usually provided by the air) or chlorine to enable rapid combustion to
continue.
Fire
has been produced by two principal methods, friction and percussion. In the
friction method, friction raises the temperature of a combustible material
(kindling) to ignition temperature. The percussion method produces a spark to
set kindling afire.
In some cultures people have
used and still use chiefly the friction method, in which two pieces of wood
surrounded by combustible material are rubbed together until the ignition
temperature is reached. In the stick-and-groove method, a stick is rubbed in a
groove in another piece of wood. In the fire-drill method, a stick is rotated
rapidly in a pit in a stationary piece of wood. The stick is rotated by rubbing
it between the palms of the hands or by moving back and forth a wooden bow
whose string is wrapped around the stick.
The
most basic percussion method of producing fire is striking together two pieces
of flint, or by striking flint against pyrite. Later, steel was substituted for
the pyrite. The flint-and-steel method prevailed throughout the civilized world
until about 1827, when matches came into use. With matches, friction is used to
heat the tip of the match to the point at which chemicals in the match head
ignite.
Fire may also be produced by using a lens or
curved reflector to concentrate the rays of the sun on combustible material.
The
use of fire probably developed in four stages. First, people observed about
them natural sources of fire, such as volcanoes and trees set afire by lightning.
Second, they acquired fire from natural sources and used it for warmth, light,
and protection from predators. Third, they learned to make fire whenever they
chose. Finally, they learned to control fire for use in smelting metal ore, in
baking pottery, and in numerous other ways to help create new technologies and
make life more comfortable.
Fire Fighting :
Fire Fighting, techniques and equipment used to extinguish fires and
limit the damage caused by them. Fire fighting consists of removing one or more
of the three elements essential to combustion—fuel, heat, and oxygen—or of
interrupting the combustion chain reaction.
Most fire fighting consists of applying water to the burning material, cooling
it to the point at which combustion is no longer self-sustaining. Fires
involving flammable liquids, certain chemicals, and combustible metals often
require special extinguishing agents and techniques. With some fuels the use of
water may actually be dangerous
Fire Fighting System
Necessity of Fire Fighting system
• The fire fighting system in the sub station is very
essential
• Saves the equipment from damage
• Loss of life & loss of equipment can be prevented
• Regular trial operation of the system is necessary to
detect any fault /deficiency in the system.
Classification of Fire protection system
1. Fire Fighting system
• The extinguishing systems which are normally employed for protection of
various equipments/buildings:
• Portable and mobile fire extinguishers.
• Hydrant system
• High velocity water spray system.
• Sprinkler system
• Medium velocity water spray system
• Water mist system
• Total flooding system using co2.
• Drain and stir type system
1.Fire Fighting System
2. Fire Detection System
Fire detection
Fire detection
Detection of fire at incipient stage plays very important role as it enables in
suppressing the fire by means of the fire fighting equipments and prevent it
from developing in to a major fire.
Detection of fire
- visual (presence of personnel is required to communicate to the concerned
authorities)
-Automatic (with the use of detectors)
Fire Detection system
– This system will provide alarm signal at the initial stage of fire.
– Detectors are located at strategic positions in the area covered by this system.
– Detectors are arranged in zones so that the area of fire can be easily identified.
– If any of the detectors in a zone is actuated an audio cum visual signal will be
given to the control panel
Schematic of Fire Fighting
Hydrant system
• Hose pipes along with branch pipes and nozzles are kept in post
boxes located adjacent to hydrants points
• In case of fire, these hoses are coupled to the respective hydrant and
jet of water is directed towards the seat of the fire.
• The system is automatic to the extent that whenever the pressure in
the piping network drops the beyond a preset value, signal is given
to start the hydrant pump by means of pressure switch. However
the stopping of the pump is manual.
• Water for the hydrant service is generally stored in an easily
accessible RCC reservoir. The water for the hydrant system shall be
supplied from the nearest bore wells available in the substation.
• The Hydrant system is spread in the switchyard and the auxiliary
systems
• Large pipes of dia 300mm/250mm/150mm either underneath or
above the ground runs in the yard
• Identification – post office red painted
• The pressure in the line is maintained by the air compressor in auto
mode – 7Kg/cm2
• The hydro pneumatic tank maintains the pressure and loss of water.
• Jockey pump maintains the water level in the hydro-pneumatic
tank
• Two level switches detect the water level
Hydrant system
Pumps
GENERAL REQUIREMENTS:
• Pumps shall be exclusively used for the fire fighting purposes. The
pumps used for the fire protection system are of the following types
• Electric motor driven centrifugal pumps, or
• Compression ignition engine driven centrifugal pumps or
• Vertical turbine submersible pumps.
– In all the above cases, pumps shall be automatic in action.
– Pumps shall be direct-coupled, except in the case of enginedriven vertical turbine pumps wherein gear drive shall be used
– Belt-driven pumps shall not be used.
Pumps & Motors
• Electrical driven HVWS Pump – 410Cum/Hr Motor 125KW
• Diesel engine driven HVWS pump - 410Cum/Hr Engine 166BHP
• Electrical driven Hydrant Pump – 96Cum/Hr Motor 30KW
• Diesel engine driven HVWS pump - 96Cum/Hr Engine 57BHP
• Jockey pump – 10.8CuM/Hr Motor 7.5KW
• Air Compressor – 8Kg/Cm2 Motor 3KW
High Velocity Water (HVW) Spray System
• This system is used for the protection of transformers and reactors in the
substation.
• The High Velocity Water Spray System - for extinguishing of oil fires
• It is employed to bring about a fundamental change in the nature of the
inflammable liquid, which is converted temporarily into an emulsion which
cannot burn.
• High Velocity water spray system - network of projectors arranged around
the equipment to be protected.
• Water under pressure is directed to the projector network through a flow
control/deluge valve from a pipe network laid exclusively for the spray
system.
• The minimum running water pressure at any projector must in no instance
be below 3.5 bar.
Electrical HVWS / Diesel engine
Emulsification process
• A special type of nozzle – projectors discharges a cone of water in the form
of evenly distributed broken streams of high velocity and high momentum.
• The rapid movement of the broken streams of water is suddenly arrested at
the oil surface and the impact causes the oil to be broken up into tiny
globules to form an emulsion with water.
• In this manner, almost immediately the water from the projector strikes the
burning oil-in-water emulsion is formed which cannot burn.
• In addition, the dispersion of the oil in minute globules in the water gives
almost instantaneous cooling and thus, together with the extinguishment of
the fire, there is simultaneous cessation of the formation of the Vapour
• Detection of fire – Quartzoid bulbs fitted in the detection line
• The Quartzoid bulbs are broken at 79Deg C thus reducing the pressure in
detection line
Deluge Valve system
HVWS Maintenance
Water Spray Systems
WATER SUPPLIES:
• Water for the spray system shall be stored in any easily accessible
surface or under ground lined reservoir or above ground tanks of steel,
concrete, or masonry.
• Reservoirs/tank shall be in two independent but interconnected
compartments with a common sump for suction to facilitate cleaning and
repairs.
• Water for the systems shall be free of particles, suspended matters,etc. and
as far as possible, filtered water shall be used for the systems.
• Level indicator shall be provided for measuring the quantity of water
stored anytime.
• Water reservoir/tank shall be cleaned at least once in two years or more
frequently if necessary to prevent contamination and sedimentation.
• It is advisable to provide adequate inflow into the reservoir/tank so that the
protection can be reestablished within a short period.
Types of fire detectors
• Heat detectors
• Smoke detectors
• Flame detectors
Heat Detectors
• These are generally less sensitive than smoke detectors and are
unlikely to respond for smoldering fires.
• They are not suitable for the protection of places where small fires
can cause huge losses.e.g. Computer Rooms
• These are suitable for use in places where sufficient heat is likely to
be generated and damage caused the heat generated by fire
contributes top main hazards. E.g. Battery Rooms, Boilers etc
Smoke detectors
Two types are available
- Ionization type
- Optical Type
Ionization type :
These are based on the principle that the electric current flowing
between electrodes in an ionization chamber is reduced, when
smoke particles enter the chamber.
Optical type :
These operate by detecting the scattering or absorption of light by
smoke particles.
• Fire detection system is provided in the following areas:
• Control room with false ceiling and floor void)
• Relay room
• DCDB
• Cable vault
• Battery room
• MCC room
• Conference room
• AHU room
If false ceiling is used detectors can be provided above and below the false
ceiling.
Ionization type smoke detectors can be used in all rooms but in cable vault
a combination of ionization and photo-electric type smoke detectors are
recommended.
Smoke detectors shall be equipped with an integral LED which will
glow in the event of its operation.
Portable fire extinguishers
The different type of fire extinguishers and their application:
• Class of fire Suitable extinguisher
Class -A Fire on ordinary combustibles Gas expelled water types and
water buckets
Class-B Fires in flammable liquids, CO2 ,DCP and sand buckets.
paints, grease and solvents.
Class-C Fires in gaseous substances CO2 and DCP type.
under pressure including LPG
Class-D Fires in reactive chemicals Special type of DCP and
active metals. Sand buckets.
Necessity of Fire Fighting system
• The fire fighting system in the sub station is very
essential
• Saves the equipment from damage
• Loss of life & loss of equipment can be prevented
• Regular trial operation of the system is necessary to
detect any fault /deficiency in the system.
Classification of Fire protection system
1. Fire Fighting system
• The extinguishing systems which are normally employed for protection of
various equipments/buildings:
• Portable and mobile fire extinguishers.
• Hydrant system
• High velocity water spray system.
• Sprinkler system
• Medium velocity water spray system
• Water mist system
• Total flooding system using co2.
• Drain and stir type system
1.Fire Fighting System
2. Fire Detection System
Fire detection
Fire detection
Detection of fire at incipient stage plays very important role as it enables in
suppressing the fire by means of the fire fighting equipments and prevent it
from developing in to a major fire.
Detection of fire
- visual (presence of personnel is required to communicate to the concerned
authorities)
-Automatic (with the use of detectors)
Fire Detection system
– This system will provide alarm signal at the initial stage of fire.
– Detectors are located at strategic positions in the area covered by this system.
– Detectors are arranged in zones so that the area of fire can be easily identified.
– If any of the detectors in a zone is actuated an audio cum visual signal will be
given to the control panel
Schematic of Fire Fighting
Hydrant system
• Hose pipes along with branch pipes and nozzles are kept in post
boxes located adjacent to hydrants points
• In case of fire, these hoses are coupled to the respective hydrant and
jet of water is directed towards the seat of the fire.
• The system is automatic to the extent that whenever the pressure in
the piping network drops the beyond a preset value, signal is given
to start the hydrant pump by means of pressure switch. However
the stopping of the pump is manual.
• Water for the hydrant service is generally stored in an easily
accessible RCC reservoir. The water for the hydrant system shall be
supplied from the nearest bore wells available in the substation.
• The Hydrant system is spread in the switchyard and the auxiliary
systems
• Large pipes of dia 300mm/250mm/150mm either underneath or
above the ground runs in the yard
• Identification – post office red painted
• The pressure in the line is maintained by the air compressor in auto
mode – 7Kg/cm2
• The hydro pneumatic tank maintains the pressure and loss of water.
• Jockey pump maintains the water level in the hydro-pneumatic
tank
• Two level switches detect the water level
Hydrant system
Pumps
GENERAL REQUIREMENTS:
• Pumps shall be exclusively used for the fire fighting purposes. The
pumps used for the fire protection system are of the following types
• Electric motor driven centrifugal pumps, or
• Compression ignition engine driven centrifugal pumps or
• Vertical turbine submersible pumps.
– In all the above cases, pumps shall be automatic in action.
– Pumps shall be direct-coupled, except in the case of enginedriven vertical turbine pumps wherein gear drive shall be used
– Belt-driven pumps shall not be used.
Pumps & Motors
• Electrical driven HVWS Pump – 410Cum/Hr Motor 125KW
• Diesel engine driven HVWS pump - 410Cum/Hr Engine 166BHP
• Electrical driven Hydrant Pump – 96Cum/Hr Motor 30KW
• Diesel engine driven HVWS pump - 96Cum/Hr Engine 57BHP
• Jockey pump – 10.8CuM/Hr Motor 7.5KW
• Air Compressor – 8Kg/Cm2 Motor 3KW
High Velocity Water (HVW) Spray System
• This system is used for the protection of transformers and reactors in the
substation.
• The High Velocity Water Spray System - for extinguishing of oil fires
• It is employed to bring about a fundamental change in the nature of the
inflammable liquid, which is converted temporarily into an emulsion which
cannot burn.
• High Velocity water spray system - network of projectors arranged around
the equipment to be protected.
• Water under pressure is directed to the projector network through a flow
control/deluge valve from a pipe network laid exclusively for the spray
system.
• The minimum running water pressure at any projector must in no instance
be below 3.5 bar.
Electrical HVWS / Diesel engine
Emulsification process
• A special type of nozzle – projectors discharges a cone of water in the form
of evenly distributed broken streams of high velocity and high momentum.
• The rapid movement of the broken streams of water is suddenly arrested at
the oil surface and the impact causes the oil to be broken up into tiny
globules to form an emulsion with water.
• In this manner, almost immediately the water from the projector strikes the
burning oil-in-water emulsion is formed which cannot burn.
• In addition, the dispersion of the oil in minute globules in the water gives
almost instantaneous cooling and thus, together with the extinguishment of
the fire, there is simultaneous cessation of the formation of the Vapour
• Detection of fire – Quartzoid bulbs fitted in the detection line
• The Quartzoid bulbs are broken at 79Deg C thus reducing the pressure in
detection line
Deluge Valve system
HVWS Maintenance
Water Spray Systems
WATER SUPPLIES:
• Water for the spray system shall be stored in any easily accessible
surface or under ground lined reservoir or above ground tanks of steel,
concrete, or masonry.
• Reservoirs/tank shall be in two independent but interconnected
compartments with a common sump for suction to facilitate cleaning and
repairs.
• Water for the systems shall be free of particles, suspended matters,etc. and
as far as possible, filtered water shall be used for the systems.
• Level indicator shall be provided for measuring the quantity of water
stored anytime.
• Water reservoir/tank shall be cleaned at least once in two years or more
frequently if necessary to prevent contamination and sedimentation.
• It is advisable to provide adequate inflow into the reservoir/tank so that the
protection can be reestablished within a short period.
Types of fire detectors
• Heat detectors
• Smoke detectors
• Flame detectors
Heat Detectors
• These are generally less sensitive than smoke detectors and are
unlikely to respond for smoldering fires.
• They are not suitable for the protection of places where small fires
can cause huge losses.e.g. Computer Rooms
• These are suitable for use in places where sufficient heat is likely to
be generated and damage caused the heat generated by fire
contributes top main hazards. E.g. Battery Rooms, Boilers etc
Smoke detectors
Two types are available
- Ionization type
- Optical Type
Ionization type :
These are based on the principle that the electric current flowing
between electrodes in an ionization chamber is reduced, when
smoke particles enter the chamber.
Optical type :
These operate by detecting the scattering or absorption of light by
smoke particles.
• Fire detection system is provided in the following areas:
• Control room with false ceiling and floor void)
• Relay room
• DCDB
• Cable vault
• Battery room
• MCC room
• Conference room
• AHU room
If false ceiling is used detectors can be provided above and below the false
ceiling.
Ionization type smoke detectors can be used in all rooms but in cable vault
a combination of ionization and photo-electric type smoke detectors are
recommended.
Smoke detectors shall be equipped with an integral LED which will
glow in the event of its operation.
Portable fire extinguishers
The different type of fire extinguishers and their application:
• Class of fire Suitable extinguisher
Class -A Fire on ordinary combustibles Gas expelled water types and
water buckets
Class-B Fires in flammable liquids, CO2 ,DCP and sand buckets.
paints, grease and solvents.
Class-C Fires in gaseous substances CO2 and DCP type.
under pressure including LPG
Class-D Fires in reactive chemicals Special type of DCP and
active metals. Sand buckets.
A fire fighting system is probably the most important of the building services, as its aim is to protect human life and property, strictly in that order.
It consists of three basic parts:
A fire hydrant is a vertical steel pipe with an outlet, close to which two fire hoses are stored (A fire hydrant is called a standpipe in America). During a fire, firefighters will go to the outlet, break open the hoses, attach one to the outlet, and manually open it so that water rushes out of the nozzle of the hose. The quantity and speed of the water is so great that it can knock over the firefighter holding the hose if he is not standing in the correct way. As soon as the fire fighter opens the hydrant, water will gush out, and sensors will detect a drop in pressure in the system. This drop in pressure will trigger the fire pumps to turn on and start pumping water at a tremendous flowrate.
A sprinkler is a nozzle attached to a network of pipes, and installed just below the ceiling of a room. Every sprinkler has a small glass bulb with a liquid in it. This bulb normally blocks the flow of water. In a fire, the liquid in the bulb will become hot. It will then expand, and shatter the glass bulb, removing the obstacle and causing water to spray from the sprinkler. The main difference between a hydrant and a sprinkler is that a sprinkler will come on automatically in a fire. A fire hydrant has to be operated manually by trained firefighters - it cannot be operated by laymen. A sprinkler will usually be activated very quickly in a fire - possibly before the fire station has been informed of the fire - and therefore is very effective at putting out a fire in the early stages, before it grows into a large fire. For this reason, a sprinkler system is considered very good at putting out fires before they spread and become unmanageable. According to the NFPA of America, hotels with sprinklers suffered 78% less property damage from fire than hotels without in a study in the mid-1980s.
It consists of three basic parts:
A fire hydrant is a vertical steel pipe with an outlet, close to which two fire hoses are stored (A fire hydrant is called a standpipe in America). During a fire, firefighters will go to the outlet, break open the hoses, attach one to the outlet, and manually open it so that water rushes out of the nozzle of the hose. The quantity and speed of the water is so great that it can knock over the firefighter holding the hose if he is not standing in the correct way. As soon as the fire fighter opens the hydrant, water will gush out, and sensors will detect a drop in pressure in the system. This drop in pressure will trigger the fire pumps to turn on and start pumping water at a tremendous flowrate.
A sprinkler is a nozzle attached to a network of pipes, and installed just below the ceiling of a room. Every sprinkler has a small glass bulb with a liquid in it. This bulb normally blocks the flow of water. In a fire, the liquid in the bulb will become hot. It will then expand, and shatter the glass bulb, removing the obstacle and causing water to spray from the sprinkler. The main difference between a hydrant and a sprinkler is that a sprinkler will come on automatically in a fire. A fire hydrant has to be operated manually by trained firefighters - it cannot be operated by laymen. A sprinkler will usually be activated very quickly in a fire - possibly before the fire station has been informed of the fire - and therefore is very effective at putting out a fire in the early stages, before it grows into a large fire. For this reason, a sprinkler system is considered very good at putting out fires before they spread and become unmanageable. According to the NFPA of America, hotels with sprinklers suffered 78% less property damage from fire than hotels without in a study in the mid-1980s.
An electric fire pump located in a fire fighting pump room.
FIRE STORAGE TANKS
The amount of water in the fire storage tanks is determined by the hazard level of the project under consideration. Most building codes have at least three levels, namely, Light Hazard (such as schools, residential buildings and offices), Ordinary Hazard (such as most factories and warehouses), and High Hazard (places which store or use flammable materials like foam factories, aircraft hangars, paint factories, fireworks factories). The relevant building code lists which type of structure falls in each category. The quantity of water to be stored is usually given in hours of pumping capacity. In system with a capacity of one hour, the tanks are made large enough to supply the fire with water for a period of one hour when the fire pumps are switched on. For example, building codes may require light hazard systems to have one hour’s capacity and high hazard 3 or 4 hours capacity.
The water is usually stored in concrete underground tanks. It is essential to ensure that this store of water always remains full, so it must have no outlets apart from the ones that lead to the fire pumps. These tanks are separate from the tanks used to supply water to occupants, which are usually called domestic water tanks. Designers will also try and ensure that the water in the fire tanks does not get stagnant and develop algae, which could clog the pipes and pumps, rendering the system useless in a fire
The water is usually stored in concrete underground tanks. It is essential to ensure that this store of water always remains full, so it must have no outlets apart from the ones that lead to the fire pumps. These tanks are separate from the tanks used to supply water to occupants, which are usually called domestic water tanks. Designers will also try and ensure that the water in the fire tanks does not get stagnant and develop algae, which could clog the pipes and pumps, rendering the system useless in a fire
FIRE PUMPING SYSTEM
Fire pumps are usually housed in a pump room very close to the fire tanks. The key thing is that the pumps should be located at a level just below the bottom of the fire tank, so that all the water in the tanks can flow into the pumps by gravity.
Like all important systems, there must be backup pumps in case the main pump fails. There is a main pump that is electric, a backup pump that is electric, and a second backup pump that is diesel-powered, in case the electricity fails, which is common. Each of these pumps is capable of pumping the required amount of water individually - they are identical in capacity.
There is also a fourth type of pump called a jockey pump. This is a small pump attached to the system that continually switches on to maintain the correct pressure in the distribution systems, which is normally 7 Kg/cm2 or 100 psi. If there is a small leakage somewhere in the system, the jockey pump will switch on to compensate for it. Each jockey pump will also have a backup.
The pumps are controlled by pressure sensors. When a fire fighter opens a hydrant, or when a sprinkler comes on, water gushes out of the system and the pressure drops. The pressure sensors will detect this drop and switch the fire pumps on. But the only way to switch off a fire pump is for a fire fighter to do this manually in the pump room. This is an international code of practice that is designed to avoid the pumps switching off due to any malfunction in the control system.
The capacity of the pumps is decided by considering a number of factors, some of which are:
Like all important systems, there must be backup pumps in case the main pump fails. There is a main pump that is electric, a backup pump that is electric, and a second backup pump that is diesel-powered, in case the electricity fails, which is common. Each of these pumps is capable of pumping the required amount of water individually - they are identical in capacity.
There is also a fourth type of pump called a jockey pump. This is a small pump attached to the system that continually switches on to maintain the correct pressure in the distribution systems, which is normally 7 Kg/cm2 or 100 psi. If there is a small leakage somewhere in the system, the jockey pump will switch on to compensate for it. Each jockey pump will also have a backup.
The pumps are controlled by pressure sensors. When a fire fighter opens a hydrant, or when a sprinkler comes on, water gushes out of the system and the pressure drops. The pressure sensors will detect this drop and switch the fire pumps on. But the only way to switch off a fire pump is for a fire fighter to do this manually in the pump room. This is an international code of practice that is designed to avoid the pumps switching off due to any malfunction in the control system.
The capacity of the pumps is decided by considering a number of factors, some of which are:
THE DISTRIBUTION SYSTEM
The distribution system consists of steel or galvanised steel pipes that are painted red. These can be welded together to make secure joints, or attached with special clamps. When running underground, they are wrapped with a special coating that prevents corrosion and protects the pipe.
There are basically two types of distribution systems
Automatic Wet systems are networks of pipes filled with water connected to the pumps and storage tanks, as described so far.
Automatic Dry systems are networks of pipes filled with pressurized air instead of water. When a fire fighter opens a hydrant, the pressurized air will first rush out. The pressure sensors in the pump room will detect a drop in pressure, and start the water pumps, which will pump water to the system, reaching the hydrant that the fire fighter is holding after a gap of some seconds. This is done wherever there is a risk of the fire pipes freezing if filled with water, which would make them useless in a fire.
Some building codes also allow manual distribution systems that are not connected to fire pumps and fire tanks. These systems have an inlet for fire engines to pump water into the system. Once the fire engines are pumping water into the distribution system, fire fighters can then open hydrants at the right locations and start to direct water to the fire. The inlet that allows water from the fire engine into the distribution system is called a siamese connection.
In high-rise buildings it is mandatory that each staircase have a wet riser, a vertical fire fighting pipe with a hydrant at every floor. It is important that the distribution system be designed with a ring main, a primary loop that is connected to the pumps so that there are two routes for water to flow in case one side gets blocked.
There are basically two types of distribution systems
Automatic Wet systems are networks of pipes filled with water connected to the pumps and storage tanks, as described so far.
Automatic Dry systems are networks of pipes filled with pressurized air instead of water. When a fire fighter opens a hydrant, the pressurized air will first rush out. The pressure sensors in the pump room will detect a drop in pressure, and start the water pumps, which will pump water to the system, reaching the hydrant that the fire fighter is holding after a gap of some seconds. This is done wherever there is a risk of the fire pipes freezing if filled with water, which would make them useless in a fire.
Some building codes also allow manual distribution systems that are not connected to fire pumps and fire tanks. These systems have an inlet for fire engines to pump water into the system. Once the fire engines are pumping water into the distribution system, fire fighters can then open hydrants at the right locations and start to direct water to the fire. The inlet that allows water from the fire engine into the distribution system is called a siamese connection.
In high-rise buildings it is mandatory that each staircase have a wet riser, a vertical fire fighting pipe with a hydrant at every floor. It is important that the distribution system be designed with a ring main, a primary loop that is connected to the pumps so that there are two routes for water to flow in case one side gets blocked.
In more complex and dangerous installations, high and medium velocity water-spray systems and foam systems (for hazardous chemicals) are used. The foam acts like an insulating blanket over the top of a burning liquid, cutting off its oxygen. Special areas such as server rooms, the contents of which would be damaged by water, usegas suppression systems. In these an inert gas is pumped into the room to cut off the oxygen supply of the fire.
When you design a fire fighting system, remember the following:
When you design a fire fighting system, remember the following:
