Transcript system operation
KURSUS PENGENALAN KEPADA PERKHIDMATAN MEKANIKAL DALAM BANGUNAN
AN INTRODUCTION TO FIRE FIGHTING DESIGN
CARBON DIOXIDESYSTEM
CONTENTS
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INTRODUCTION DESIGN STANDARDS SYSTEM OPERATION CARBON DIOXIDE CYLINDERS CARBON DIOXIDE CONTROL PANEL DISCHARGE NOZZLE AUTOMATIC DETECTORS AND ALARM BELLS PIPEWORK AND FITTINGS WARNING SIGNS
AUTOMATIC CARBON DIOXIDE SYSTEM
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Consists of CO2 cylinders, steel piping, discharge nozzles, heat/smoke detectors, gravity shutter, alarm system etc.
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Discharged after a time delay upon detection of fire.
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Usually for Transformer room, Switchroom, Standby Generator room and High Switch Gear room.
DESIGN STANDARDS
In the UBBL (1984), the By-laws relating to Carbon Dioxide is By-laws 235 and the applicable standard is: NFPA 12
SYSTEM OPERATION
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The protected area should be flooded with CO2, seconds, adjustable up to 60 seconds.
Total discharge shall not exceed 1 minute.
For deep seated total discharge shall not exceed 7 minutes or 30% discharge within 2 minutes.
Supply Voltage 240V A.C, 50 Hz.
A 24V D.C standby battery in case of mains voltage failure.
SYSTEM OPERATION
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The space protected by two or more heat or smoke detectors.
8. The indicator light on the control panel should illuminate and audible warning sounded via alarm bell.
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CARBON DIOXIDE CYLINDERS
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Where more than three cylinders are required, a pilot cylinder should be provided to activate the discharge from each cylinder.
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CARBON DIOXIDE CONTROL PANEL
Should indicate the operation of the system hazards to personnel, or failure of any supervised device.
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Complying with MS 1404 and BS 7273.
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Alarm should be provided to give warning of a discharge.
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A device should be incorporated into the system to shut down any exhaust fans and activate solenoid operated curtains across louvres before discharge.
DISCHARGE NOZZLE
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The discharge nozzle should consists of the orifice and any associated horn, shield or baffle.
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Discharge orifices should be of corrosion resistant metal.
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Permanenrly marked to identify the nozzle and to show the equivalent shield orifice diameter regardless of shape.
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Discharge nozzle should be provided with frangible disc
Automatic Detector and Alarm Bells
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The Automatic detection is usually by means of either heat or smoke detectors.
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Should be resistant to corrosion.
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The alarm bells should produce an alarm at least 65dBA or 5dBA.
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The bell should be of the trembling (not single stroke).
WARNING SIGNS
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Warning and instruction signs should be installed at entrances to and inside protected areas at prominent positions.
PIPE WORK AND FITTING
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The material of piping and fittings must be of non combustible heat resisting. 2.
Maintain its own shape in room temperature during the outbreak of fire.
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All piping should be of API Schedule 40/80 steel pipe.
SAMPLE CALCULATION FOR CO2 SYSTEM
PROJECT ROOM NAME : : NEW MORTUARY FOR PENANG HOSPITAL STANDBY-GENERATOR ROOM
STAND BY–GENERATOR ROOM
Area = Volume = 5.5 X 6.0m
5.5 x 6.0 x 4.15m
Nozzle coverage area Nos of nozzle required Flooding Factor Design Concentration Actual weight of CO¸ = = = = = = = = = 33m² 137 m³ 28.28m² 33/28.28 1.17 ~ 2 nos.
1.35kg/m³ 50% 137m³x1.35kg/m³ 185kg Nos of cylinder = = 185kg/45kg 5 nos Consider 30% volume of C0¸ to be used = = 0.3x137m³ 41m³
Design manual based on desired flow rate Therefore flow rate for 2 mins Q = 41m³ (exp.30°C) 0.56m³/kg = = @ 2mins = 73.2kg
2min Time of discharge of CO² at volume = = Pipe sizing for flow rate, Pipe size Q = = 0.56m³/kg @ 30°C 73.2kg
37kg/mins 185kg 37kg/min = 37kg/mins 20mm 5mins
SWITCH – BOARD ROOM
Area Volume Nozzle coverage area = = 5.5x4.5 5.5x4.5x4.15
= = = 25m² 103m³ 28.28m² 0.9 ≈ 1 no.
Nos Nozzle Flooding Factor weight CO² Nos cylinder 30% Volume Q = = = = = = 56kg/2mins @ 2mins 25/28.28 1.35kg/m³ @ 50% 139kg 139kg/45kg 03x103m³ = 31m³/0.56m³/kg (expansion 30°C) @ 0.56m³ = = = = Time Discharge Pipe sizing Q = 139kg/28kg/min = = = 3nos 31m³ 28kg/mins 5 min 28kg/mins 20mm