Automatic Fire Sprinkler Systems Flashcards

1
Q

What is an Automatic Fire Sprinkler Systems

A

A fire suppression system consisting of a network of water pipes and sprinkler heads.

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2
Q

Fire suppression means meaning

A

To extinguish, control, or in some cases, entirely prevent fires from spreading or occurring.

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3
Q

Operation of Automatic Fire Sprinkler Systems

A
  • 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.
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4
Q

Main Functions of Automatic Fire
Sprinkler Systems

A

To detect a fire automatically, to deliver water to attack fire through sprinkler heads, sound an alarm & prevent spread of fire.

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5
Q

Main Features of Automatic Fire
Sprinkler Systems

A
  • (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.
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6
Q

Effectiveness of Automatic Fire Sprinkler Systems

A
  • 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.
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7
Q

Why sometimes sprinkler system ‘not effective’

A

Due to system being turned off for repair or closed too early when a fire is in progress.

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8
Q

Types of Automatic Fire Sprinkler
Systems

A
  • Wet Pipe Fire Sprinkler System
  • Dry Pipe Fire Sprinkler System
  • Pre-action Fire Sprinkler System
  • Deluge Fire Sprinkler System
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9
Q

Wet Pipe Sprinkler System

A
  • 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.
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10
Q

Why is wet pip useed to protect property that is maintained at a constant temperature of at least 5°C?

A
  • Water is constantly maintained throughout system.
  • So used where temperatures will not reach freezing levels
  • No danger of water freezing in pipe.
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11
Q

Dry Pipe Fire Sprinkler System

A
  • 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.
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12
Q

What is a pre-action fire sprinkler system?

A
  • Combines a dry pipe system and an alarm system.
  • Protects water-sensitive properties like libraries &storage areas for valuable artifacts.
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13
Q

How does the pre-action system work?

A
  • 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.
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14
Q

Advantage of Pre-action

A

delay affords occupants time to extinguish fire with portable fire extinguishers.

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15
Q

Use of Pre-action Fire Sprinkler system

A
  • 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.
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16
Q

Deluge Fire Sprinkler System

A
  • 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.
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17
Q

How Deluge Fire Sprinkler System works

A
  • 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.
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18
Q

Where are Deluge Fire Sprinklers used?

A
  • 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.
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19
Q

Provision of Automatic Fire
Sprinkler Systems: To be provided when…

A
  • 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.
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20
Q

Operation of a Wet Pipe Automatic
Fire Sprinkler System

A
  • 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.
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21
Q

Water Supply in Fire Sprinkler System

A
  • 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.
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22
Q

Pumps for Fire Sprinkler System

A

Three pumps installed
* Two main fire pumps
* Smaller size jockey pump

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23
Q

Main Fire Pumps

A
  • Pumps must be automatically driven either by electric motor or diesel type engine.
  • Electrical supply for electric motor driven pumps must be obtained from main power supply backed up by emergency power from building standby generator.
  • Can only be manually stopped after a fire operation.
24
Q

Main fire pumps used (2 types)

A
  • duty pump
  • standby pump.
25
Q

Jockey pump

A
  • Not required by Code but is installed as a practical requirement.
  • Used to maintain minimum pressure in fire sprinkler system to avoid non-emergency starting of main fire pump.
  • Makes up for small losses in pressure in the system due to leakage or water contraction.
  • Keeps main fire pumps from operating unnecessarily which shortens their life span.
  • During a fire, system pressure will continue to drop, and main fire pump will take over.
26
Q

How are Jockey Pumps designed?

A
  • Designed to start before main fire pump & return fire protection system to its minimum static pressure.
  • NOT designed to keep up with water flow demand in event of fire.
27
Q

Once main fire pump starts…

A

jockey pump will be switched off.

28
Q

Pressure Switch

A
  • Installed in main distribution pipe of sprinkler system to detect pressure changes of water in sprinkler system.
  • Each pump is controlled by its own individual pressure switch.
29
Q

What if there is a small drop in pressure caused by water leakage?

A

pressure switch of jockey pump will first start jockey pump to restore water pressure.

30
Q

What if there is a large drop in pressure caused by sprinkler head rupture?

A

jockey pump will not be able to cope with rapid pressure drop.

31
Q

What if duty pump fails to start?

A
  • water pressure will continue to drop further.
  • Drop in water pressure will be detected by standby fire main pump pressure switch and activates standby fire main pump to operate.
32
Q

Main Stop Valve

A
  • Normally located immediately below alarm valve.
  • Main gateway for water flow to system.
  • Water to entire automatic fire sprinkler system is supplied through main stop valve.
  • Normally locked open to allow water to be supplied to sprinkler system immediately during an emergency.
33
Q

Purpose of Main Stop Valve

A
  • Isolate system for maintenance & modification works to be carried out.
  • Shut down fire sprinkler system after fire has been put out to minimise water damage.
  • Status of main stop valve, whether open or shut, is electrically monitored by Main Alarm Panel at Fire Command Centre.
  • To avoid situation whereby main stop valve is switched off accidentally or deliberately for no reason.
34
Q

Alarm Valve location

A

immediately above main stop valve

35
Q

Alarm Valve

A
  • Separates sprinkler system from water supply system when system is operational but not operating.
  • Alarm valve is kept closed by water pressure above it.
  • To prevent water from sprinkler system back-flowing to potable water supply thereby causing contamination.
36
Q

When alarm valve operates…

A
  • When sprinkler operates, water pressure above alarm valve drops.
  • As pressure below alarm valve is higher, alarm valve will open allowing
    water to flow upward into system to feed ruptured sprinkler head.
  • At same time, some water also flows to an alarm gong, raising an alarm.
37
Q

Water Distribution

A
  • Water flows from main stop valve to vertical riser and to main distribution pipes at ceiling.
  • From main distribution pipes, it passes to distribution pipes and then to range pipes where sprinklers are attached.
  • Water is then discharged at sprinkler heads which have been ruptured by hot rising smoke and gases from fire.
38
Q

Water Proving Facility

A
  • Located above alarm valve.
  • Consists of a test pipe arrangement, an orifice plate as flow meter and pressure gauges.
  • Allows design flow rate to be simulated for verifying that water flow
    rate is sufficient.
39
Q

Fire Service Breeching Inlet

A
  • Allows fire service to back-up water supply to fire sprinkler system.
  • Breeching inlet is fitted with a non-return valve to prevent water from sprinkler system running back to contaminate water supply from hydrant system.
40
Q

What is a Fire Sprinkler Head

A
  • Basically a glass bulb containing heat sensitive liquid which expands when heated.
  • Orifice of sprinkler head is closed by a disc & held in place by glass bulb which is temperature sensitive.
  • In liquid is a small air bubble to accommodate small changes in volume of liquid due to normal temperature changes.
41
Q

How Fire Sprinkler Head wprks

A
  • Heat from high temperature fire causes the liquid to expand sufficiently to absorb the bubble.
  • Thereafter the resultant pressure shatters glass bulb removing disc to discharge water from orifice on to deflector to produce a spray over a specified area below.
  • Installed on range pipes over protected area.
42
Q

three main types of sprinkler water distribution patterns

A
  • Pendent
  • Upright
  • Sidewall
43
Q

Pendent Type

A
  • Water is directed downward from pipe & sprayed radially.
  • Pendant design minimises effect of water pipe on spray distribution.
  • Wider deflector is used to produce a hemispherical distribution practically below the sprinkler with little or no water reaching the ceiling.
44
Q

Upright Type

A
  • Installed above water pipe
  • Designed to spray water radially to fall to area below without necessarily
    wetting ceiling.
  • Still for upright designs, pipe interferes with distribution of spray as
    droplets fall downward.
  • If depth of false ceiling space exceeds 800 mm, it must be protected by second layer of fire sprinkler heads.
45
Q

Why if depth of false ceiling space exceeds 800 mm, it must be protected by second layer of fire sprinkler heads?

A

Voids of this depth can be a potential storage space.

46
Q

Sidewall Type

A
  • Gives a skewed quarter spherical distribution below the sprinkler throwing much of its discharge back to the room.
  • Designed for use at side of rooms or corridors, so that the water spray will be projected into the centre of room or corridor to be protected.
47
Q

Major considerations for sprinkler head maintenance are:

A
  • Remove coatings from sprinkler
    heads
  • Remove high objects from beneath
    sprinkler heads
48
Q

Remove coatings from sprinkler
heads

A
  • Over time, sprinkler heads can gather a coating of dirt that delays rupture of sprinkler heads especially where sprinklers are in areas where grease accumulates such as kitchens.
  • Coatings can be removed from sprinkler heads by washing them with a non-residue, non-corrosive degreasing solution.
  • Above all, painting of sprinkler heads should be avoided when ceiling of a room is painted.
49
Q

Remove high objects from beneath
sprinkler heads

A
  • Technically, removing high objects from beneath sprinkler heads is not a maintenance measure.
  • However, removing them helps ensure that sprinkler heads distribute water evenly throughout the room.
  • Rooms in which tall or stacked objects block the spray of sprinkler heads are essentially fire hazards.
50
Q

Fire Sprinkler Pipe Layout

A
  • Range pipe is a pipe on which
    sprinklers are attached either directly or through a short arm which do not exceed 300 mm in length.
  • Distribution pipe is a pipe feeding directly to range pipes.
51
Q

Water Monitor Fire Extinguishing
System are used in…

A

atriums with ceiling heights exceeding 18m

52
Q

atriums w ceiling heights below 18m use…

A

fire sprinkler system

53
Q

Why atriums w ceiling heights more than 18m need water monitor?

A
  • water spray from fire sprinkler system may not be effective
  • due to spread of water spray as it falls onto the ground level, losing its momentum & unable to knock out fire
  • need water monitor’s extended-throw & able to cover entire atrium space
54
Q

Operation of Water Monitor Fire Extinguishing System

A
  • Has infra-red sensor together with
    computerised control built into device.
  • When fire occurs, infra-red sensors will detect the fire and activate water monitor.
  • Water monitor will rotate to locate exact location of fire & direct nozzle
    of water monitor at fire.
  • Water will then be discharge from nozzle, in form of a water jet, into fire.
  • Device able to locate exact position of fire & direct water discharge at fire within 30s of fire detection
55
Q

What happens when fire is extinguished by water monitor

A
  • Water discharge will be stopped manually.
  • Monitor will reset, then automatically return to its standby mode.
  • If fire re-ignites or there is another fire, water monitor will activate again.