- What is a fire sprinkler system?
 A fire sprinkler
system is a method to limit the damage to life and property by
fire. A sprinkler system does not prevent fire, but rather works
to suppress a fire. A fire system uses pressure and flow rate
of water or approved designated chemicals through a pipe system.
At specified spaced intervals on these pipes, sprinklers (also
called sprinkler heads, or just heads) are placed to disperse
the fire retardant. Water is the most common type fire retardant
used in commercial and residential systems.
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- Contrary to the Hollywood depiction, most sprinkler systems
do not use a single sprinkler head to set off an entire system.
Most systems use require a single head that activates independently
and as needed. This method limits damage to property that is
not affected by fire, and helps to maximize the available water
pressure over the point of the fire's origin. So you can't just
hold up a lighter to one sprinkler head an expect the entire
system to activate.
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- How does a sprinkler system work?
- Sprinkler systems are designed to control a fire or to suppress
a fire. A control mode sprinkler system is designed to control
a fire to limit the spread of a fire, pre-wet combustible materials,
and prevent the physical collapse of the building. The system
controls the fire until the fire department arrives and effectively
extinguishes the fire and/or until burning combustibles are exhausted.
Early Suppression Fast Response (ESFR) systems (also known simply
as Suppression systems) are designed for sudden reduction of
fire and to completely extinguish a fire prior to manual intervention.
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- A typical sprinkler head for commercial use disperses about
20-40 gallons of water per minute. Suppression systems can release
a higher rate of flow at 100 gallons per minute. Compare that
to the stream of water from a fire hose which can disperse 250
gallons of water per minute.
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- Each sprinkler head is held closed by a glass bulb or a two-part
metal link. These 'links' or 'bulbs' use pressure to hold a cap
in place which acts as a plug in the system. These links are
designed to break at a specified temperature, releasing the plug
and allowing water to disperse over the flames.
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- What makes a sprinkler system so valuable is the amount of
time it takes to activate as opposed to suppression by the fire
department. A typical system will activate within 4 to 5 minutes.
Where as the local fire department can take between 5 to 10 minutes
to arrive at a fire and an additional 10 minutes to assess the
fire, set up equipment and apply water to the fire. This additional
time allows a fire to grow, thereby doing more damage and requiring
more water to suppress the flames. Which can cause additional
water damage to equipment and property. The additional time can
also create a greater danger for the loss of life.
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- Today's Fire Protection Systems
- There is very little Federal legislation regarding sprinkler
system design and installation. Building codes are generally
left to local jurisdictions and that includes the specifications
for sprinkler systems. The Federal government has used its funding
and monetary clout to strongly encourage fire safety standards.
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- In 1895 the National Fire Protection association (NFPA) was
founded in Boston by Frederick Grinnell,
a pioneer in the fire protection industry. It was the first time
anyone had set and implemented standards for the installation
of automatic fire sprinklers. His venture proved to be greatly
successful and the NFPA standards became the uniformed installation
requirements for the United States and Canada.
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 Even with all the
improvements and desires to protect life through fire prevention
and suppression systems, nothing impacts standards more than
a catastrophe. The MGM Grand Hotel fire in Las Vegas in 1980
was such an event. 85 guests and workers died during the fire
captured on TV by local, national and even worldwide news agencies.
The tragedy resulted in one of the nations first fire sprinkler
retrofit ordinances for high-rise buildings.
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- Many see this fire as the event that set off some of the
first federal legislation for building safety. In 1990 the US
Congress passed PL-101-391, better known as "The Hotel and
Motel Safety Act (of 1990)". This law requires that any
hotel, meeting hall, or similar institution that receives federal
funds (i.e. for a government traveler's overnight stay, or a
conference, etc.), must meet fire and other safety requirements.
Included in these conditions is the implementation of working
sprinklers.
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- Today fire sprinkler application and installation guidelines,
and overall fire sprinkler system design guidelines, are provided
by the standards set in several NFPA sections. The most common
standards are found in NFPA 13, NFPA 13D, and NFPA 13R, NFPA
14, NFPA 20 and NFPA 24. These specifications define the accepted
minimum requirements for building codes that are set by local
jurisdictions in the United States. Many local jurisdictions
add on to these requirements and various state jurisdictions
include additional requirements within state wide building codes.
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- How is a sprinkler system designed?
- Most of today's commercial/industrial sprinkler systems are
designed with a area and density approach. Early Suppression
Fast Response (EFSR) systems are designed with a special area
in mind. ESFR is calculated based on flowing 4 heads on 3 adjacent
lines. Residential systems are generally created in a room design
method. The building itself, how the building will be used and
what contents will be maintained or stored in the building all
determine the appropriate design of the sprinkler system. This
information is used to define the fire hazard classification
and the type of fire classification.
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- Fire Hazards:
- NFPA 13 defines fire hazards into 3 main groups, two of which
have sub-classifications.
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- • Light Hazard occupancy is defined as:
- • The Combustibility of the contents is low, and
- • The Quantity of the combustible is low, and
- • There are Low rates of heat release.
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- • Ordinary Hazard
- • Group 1 Hazard is defined as:
- • The Combustibility of the contents is low, and
- • The Quantity of the combustibles is moderate, and
- • The Moderate heat release rates, and
- • The Height of storage is 8 feet or less.
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- • Group 2 Hazard is defined as:
- • The Combustibility of the contents is moderate to
high, and
- • The Quantity of the combustibles is moderate to high,
and
- • The Moderate to high rates of heat release, and
- • The Storage height is 12 feet or less.
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- • Extra Hazard
- • Group 1 Hazard is defined as:
- • The Combustibility of the contents is very high, and
- • The Quantity of the combustibles is very high, and
- • The High rates of heat release, and
- • The Quantity of flammable and/or combustible liquids
small.
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- • Group 2 Hazard is defined as:
- • The Quantity of flammable or combustible liquids is
moderate to high, or
- • The Extensive shielding of the combustibles is present.
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- Fire Classifications:
- Jurisdictions often set classifications for the types of
fire hazards contained in buildings. These classifications are
basic definitions and maybe enhanced or further classified by
local jurisdictions and building codes. These classifications
help define the standard requirements for designing and implementing
fire protection systems.
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Type of Fire |
North America |
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Fires that involve flammable solids such as wood, cloth, rubber,
paper, and some types of plastics. |
Class A |
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Fires that involve flammable liquids or liquefiable solids such
as petrol/gasoline, oil, paint, some waxes & plastics, but
not cooking fats or oils |
Class B |
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Fires that involve flammable gases, such as natural gas, hydrogen,
propane, butane |
|
Fires that involve combustible metals, such as sodium, magnesium,
and potassium |
Class D |
|
Fires that involve any of the materials found in Class A and
B fires, but with the introduction of an electrical appliances,
wiring, or other electrically energized objects in the vicinity
of the fire, with a resultant electrical shock risk if a conductive
agent is used to control the fire. |
Class C |
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Fires involving cooking fats and oils. The high temperature of
the oils when on fire far exceeds that of other flammable liquids
making normal extinguishing agents ineffective. |
Class K |
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- System Calculations
- Once these classifications have been determined, the design
area and required density are defined, the system is then calculated.
Calculations are made to determine the sprinkler layout and pipe
sizes required to protect a building for a given occupancy hazard.
Calculations cover the pressure loss due to friction and elevation.
Calculations for gains occur if the flow goes through a fire
pump, or if there is a decrease in elevation. However it is pretty
rare for there to be a decrease in elevation.
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- What are the types of sprinkler systems?
- There are several types of sprinkler systems. Most are water
based, but some special hazards may require non-water spray systems.
Most jurisdictions require remote monitoring of all sprinkler
systems except 13-D types.
- Water spray
 All water based
systems are considered to be "Water Spray" systems.
These systems use specified spray patterns to control or suppress
a fire. Spray patterns can be oval (the most common), fan, full
circle and narrow jet. The amount of water dispersed often defines
the main characteristic of the type of water spray system.
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- Wet pipe systems
- These are the most commonly used water spray systems. Water
is fed into the piping and remains under pressure until a sprinkler
head is activated. When activated the pressure forces the water
out through the head and suppresses a fire. Larger wet pipe systems
are often monitored by a fire alarm control panel. Additional
types of communication control panels are available based on
hazard and need. For high rise buildings or buildings/hazards
that require higher than normal water pressure or volume, a wet
pipe system may include a fire pump.
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- Dry pipe systems
- A dry pipe sprinkler system uses pressurized air, rather
than water within the piping system. this s often used in places
where the temperature outside or around the pipe has the potential
of freezing the water within the pipe. Obviously this would be
a bad thing as it would render the sprinkler system inoperable
and/or could potentially cause the pipes to rupture creating
a catastrophic failure of the system. Not to mention the subsequent
water damage.
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- In a dry pipe system, the air pressure holds a valve (known
as a dry pipe valve) in the closed position. The dry pipe valve
is protected by being located in a heated space. When a fire
causes one or more of the sprinkler heads to activate, air pressure
is released which activates the dry-pipe valve. The valve opens
and allows water to enter the pipe, flowing through open sprinklers
onto the fire.
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- Dry pipe systems are typically installed in unheated spaces,
such as attics, unheated warehouses, commercial freezers or for
outside loading docks.
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- Deluge systems
- This is the Hollywood example of a complete system activation.
Deluge systems work pretty much like the name implies. They douse
an area quickly with a deluge of water to quickly suppress a
fire. They are typically used in extra-hazard areas such as power
generation stations, petrochemical facilities, aircraft hangers
and other similar warehouse or storage areas. Deluge Systems
can include a manual, pneumatic, hydraulic, or any type of electric
detection/release system.
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- Water is not present in the piping until the system operates.
A deluge valve holds back the water from the open piping system.
The deluge valve is activated by a fire alarm system that has
been initiated by a fire detection device (smoke detector, heat
detector, or optical flame detector). The initiating device signals
the fire alarm panel, which in turn signals the deluge valve
to open. The detection device used is determined by the type
of hazard within the building.
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- The deluge valve is used at the water supply connection and
mechanically latched. When activated the valve stays open, meaning
it cannot be reset and stays open once it's tripped.
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- Pre-Action Systems
- Pre-action Systems are most frequently used to protect against
accidental water discharge is of great concern. They are often
used in museums, libraries, data centers or where electrical
or computer equipment are used. Pre-action systems are hybrids
of wet, dry, and deluge systems. There are two primary sub-types
of pre-action systems: single interlock and double interlock.
The only practical pre-action system is the double interlock
design, primarily because the point of pre-action is to make
absolutely sure there's actually a fire before operating.
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- Double-Interlocked Pre-action Systems require activation
of both the detection system and a sprinkler before allowing
water to flow into the piping system. When the alarm system and
a sprinkler both activate, the pre-action valve will trip and
water ill enter the open piping system and disperse water on
the coverage area. Double interlock systems are considered as
dry systems in terms of water delivery times, and similarly require
a larger design area.
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- The Single-Interlocked Pre-action System utilizes a pre-action
valve which is mechanically latched similar to a deluge valve.
The pre-action valve will not open due to loss of air pressure
in the pipe system. Activation of the pre-action valve occurs
when a detection system (fire, smoke alarm etc.) denotes a fire.
Water then flows into the pipes, changing the piping system from
a dry system to a wet system. Water is held in the system until
a sprinkler opens and allows water to flow into the coverage
area. This method of delivery protects against the accidental
loss of air pressure in the piping system.
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- Foam water sprinkler systems
- A foam system is a special application system using a mixture
of water and low expansion foam concentrate to suppress a fire.
These systems are used for special high hazard fires such as
flammable liquids, in airport hangers and alike. Additional components
are added to the sprinkler system for foam operation. This includes
bladder tanks that hold the foam concentrate and are connected
to the sprinkler system riser. Concentrate control valves are
used to isolate the sprinkler system from the foam until activation.
Pro-portioners are used for mixing the appropriate amount of
foam with the water supply before dispersal.
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- Non water based sprinkler systems
- Special hazards may require the use of non water based sprinkler
systems. These hazard areas include places where water will increase
the chance or size of a fire, instead of suppress it. These systems
maybe used in electrical switch gear rooms, where lithium, sodium
or other sensitive chemicals are stored. For example, when exposed
to water lithium will ignite.
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- INTEGRITY
has designed several commercial, industrial and residential sprinkler
systems for our clients. We have the knowledge and experience
to help you lay out a plan and design a system that's right for
your business or home. You can learn more about INTEGRITY, our experience and
services by visiting our Home page
or calling us at 704.888.5510
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- Copyright 2010 - Integrity Fire Services Inc.
- Duplication of any material, in whole or in part, is strictly
prohibited.
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