Automatic Fire Sprinkler Systems Flashcards
What is an Automatic Fire Sprinkler Systems
A fire suppression system consisting of a network of water pipes and sprinkler heads.
Fire suppression means meaning
To extinguish, control, or in some cases, entirely prevent fires from spreading or occurring.
Operation of Automatic Fire Sprinkler Systems
- Water is fed to sprinkler heads through a network of water pipes, which are normally suspended from ceiling & spaced at regular intervals.
- Heat from a fire causes sprinkler head to rupture allowing water to be discharged from piping at or near seat of fire, due to water pressure in piping system.
- Alarm gong is operated at same time by water flowing from alarm valve.
Main Functions of Automatic Fire
Sprinkler Systems
To detect a fire automatically, to deliver water to attack fire through sprinkler heads, sound an alarm & prevent spread of fire.
Main Features of Automatic Fire
Sprinkler Systems
- (main function)
- electrically monitored in that fire signal is automatically sent to fire station through an approved alarm monitoring station when sprinkler head is activated.
Effectiveness of Automatic Fire Sprinkler Systems
- Extremely effective &have proven
- Automatic sprinkler systems are extremely effective and have proven to
excellent fire protection particularly high-rise buildings & warehouses. - Studies conducted between 1969 and 1979, out of 1394 fires it was found
that 63% of fires were extinguished by operation of one sprinkler, whilst 21% of the fires were extinguished by operation of two sprinklers.
Why sometimes sprinkler system ‘not effective’
Due to system being turned off for repair or closed too early when a fire is in progress.
Types of Automatic Fire Sprinkler
Systems
- Wet Pipe Fire Sprinkler System
- Dry Pipe Fire Sprinkler System
- Pre-action Fire Sprinkler System
- Deluge Fire Sprinkler System
Wet Pipe Sprinkler System
- Water is constantly maintained throughout system.
- Quickest reaction time, can apply water to a fire faster than any other systems cuz water is maintained in pipe.
- Heat from fire causes sprinkler head to rupture allowing water to be discharged from piping at or near seat of fire as alarm valve opens.
- Used in offices, shopping malls, factories and others.
Why is wet pip useed to protect property that is maintained at a constant temperature of at least 5°C?
- Water is constantly maintained throughout system.
- So used where temperatures will not reach freezing levels
- No danger of water freezing in pipe.
Dry Pipe Fire Sprinkler System
- Utilised to protect property in an environment that is susceptible to freezing temperatures.
- Water is not maintained in distribution pipes above alarm valve, instead air is maintained in pipes under pressure.
- When sprinkler head ruptures, pressurised air in system will be expelled before alarm valve opens & water is applied.
- Have slower reaction time than wet pipe systems.
- Used in freezing environments such as cold storage applications.
What is a pre-action fire sprinkler system?
- Combines a dry pipe system and an alarm system.
- Protects water-sensitive properties like libraries &storage areas for valuable artifacts.
How does the pre-action system work?
- Pressurised air maintained in distribution pipes above alarm valve.
- Smoke detection system connected to alarm valve.
- Two smoke detectors confirm with one another, activate when smoke is detected.
- Once smoke signal is received, it is transmitted to alarm valve.
- Signal causes alarm valve to open & pressurised air is expelled through exhauster.
- Water enters distribution pipes but is not discharged yet.
- Sprinkler heads will only rupture at set temperature and water will be applied after sprinkler head ruptures.
Advantage of Pre-action
delay affords occupants time to extinguish fire with portable fire extinguishers.
Use of Pre-action Fire Sprinkler system
- Water is only applied if human intervention fails to control fire.
- Used to protect property that are sensitive to water damage from leaked pipes
- Like libraries & storage areas for valuable artefacts as distribution pipes contain compressed air, not water, during normal circumstances.
Deluge Fire Sprinkler System
- Unique compared to other types as sprinkler heads are opened at all times.
- Sprinkler heads not connected to any glass bulb.
- Protect high hazard areas where fast-spreading fire is anticipated due to fire load.
How Deluge Fire Sprinkler System works
- Activated by smoke detection system connected to alarm or deluge valve.
- Smoke detectors sense fire, transmits signal that opens alarm valve.
- Water flows from all sprinkler heads, deluging protected area.
- Water applied to fire more quickly & over a wide distribution area compared to other systems.
Where are Deluge Fire Sprinklers used?
- Extra hazard occupancies where flammable & hazardous materials are stored & handled as such aircraft hangars, power plants etc
- Where flammable liquids/gases are present.
- Also suitable for installations that contain low flash point flammable liquids where fire may flashover before ordinary sprinkler head could operate including high-risk areas such as chemical storage.
Provision of Automatic Fire
Sprinkler Systems: To be provided when…
- Whenever compartmentation cannot be complied with regard to size limitation.
- Every level of a building, except Group I or Group II, where habitable height of building is more than 24m above ground level regardless of compliance with compartmentation.
- For all basement levels, except that of Group I/Group II, regardless of compartment size, except where basement storey is effectively cross ventilated to prevent smoke logging, basement storey can be exempted from providing automatic sprinkler.
Operation of a Wet Pipe Automatic
Fire Sprinkler System
- Fire ignites, smoke & gases generated rise to heat up fire sprinkler head.
- As temperature of smoke & hot gases rises to operating temperature of expansible liquid in glass bulb of sprinkler head, it will rupture.
- Water from sprinkler head will be released to extinguish fire.
- As water flows in distribution pipe, it activates flow switch, flow switch will in turn send signal to Main Alarm Panel of Fire Alarm System.
- From main alarm panel, fire signal will be transmitted automatically to fire service through an approved alarm monitoring station.
- As water flows out from sprinkler head, water pressure in pipe drops and a pressure switch will activate jockey pump to run.
- Subsequently main fire pump will operate to provide required water supply to fight fire.
Water Supply in Fire Sprinkler System
- Water is normally supplied to a fire sprinkler system by pump which draws water from suction tank.
- Suction tank is automatically refilled with water from PUB public water supply.
Pumps for Fire Sprinkler System
Three pumps installed
* Two main fire pumps
* Smaller size jockey pump