KURSUS
PENGENALAN KEPADA
PERKHIDMATAN
MEKANIKAL DALAM
BANGUNAN
AN INTRODUCTION TO FIRE FIGHTING DESIGN
CARBON DIOXIDESYSTEM
CONTENTS
1.
2.
3.
4.
5.
6.
7.
8.
9.
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
1.
Consists of CO2 cylinders, steel piping, discharge
nozzles, heat/smoke detectors, gravity shutter,
alarm system etc.
2.
Discharged after a time delay upon detection of fire.
3.
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
1.
Quantity of agent should be sufficient to ensure
rapid extinction.
2.
The protected area should be flooded with CO2,
concentration of 50% at 21C, with period of 30
seconds, adjustable up to 60 seconds.
3.
Total discharge shall not exceed 1 minute.
4.
For deep seated total discharge shall not exceed 7
minutes or 30% discharge within 2 minutes.
5.
Supply Voltage 240V A.C, 50 Hz.
6.
A 24V D.C standby battery in case of mains voltage
failure.
SYSTEM OPERATION
7.
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.
CARBON DIOXIDE CYLINDERS
1.
Gas stored in a liquefied form at ambient
temperatures.
2.
Working pressure of 59 bars at 21C and pressure
tested at 228 Bars.
3.
Name plate specifying the number, filling weight
and the pressurisation level.
4.
All cylinder supplying the same manifold outlet for
distribution.
5.
Where more than three cylinders are required, a
pilot cylinder should be provided to activate the
discharge from each cylinder.
CARBON DIOXIDE CONTROL
PANEL
1.
Should indicate the operation of the system
hazards to personnel, or failure of any supervised
device.
2.
Complying with MS 1404 and BS 7273.
3.
Alarm should be provided to give warning of a
discharge.
4.
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
1.
The discharge nozzle should consists of the
orifice and any associated horn, shield or baffle.
2.
Discharge orifices should be of corrosion
resistant metal.
3.
Permanenrly marked to identify the nozzle and
to show the equivalent shield orifice diameter
regardless of shape.
4.
Discharge nozzle should be provided with
frangible disc
Automatic Detector and Alarm
Bells
1.
The Automatic detection is usually by means of
either heat or smoke detectors.
2.
Should be resistant to corrosion.
3.
The alarm bells should produce an alarm at least
65dBA or 5dBA.
4.
The bell should be of the trembling (not single
stroke).
WARNING SIGNS
1.
Warning and instruction signs should be installed at
entrances to and inside protected areas at
prominent positions.
PIPE WORK AND FITTING
1.
The material of piping and fittings must be of noncombustible heat resisting.
2.
Maintain its own shape in room temperature during
the outbreak of fire.
3.
All piping should be of API Schedule 40/80 steel
pipe.
SAMPLE CALCULATION FOR
CO2 SYSTEM
PROJECT
:
NEW MORTUARY FOR
PENANG HOSPITAL
ROOM NAME
:
STANDBY-GENERATOR
ROOM
STAND BY–GENERATOR ROOM
Area
=
5.5 X 6.0m
Volume =
5.5 x 6.0 x 4.15m
Nozzle coverage area
Nos of nozzle required
Flooding Factor
Design Concentration
Actual weight of CO¸
Nos of cylinder
=
=
=
=
=
=
=
=
=
33m²
137 m³
28.28m²
33/28.28
1.17 ~ 2 nos.
1.35kg/m³
50%
137m³x1.35kg/m³
185kg
=
=
185kg/45kg
5 nos
=
=
0.3x137m³
41m³
Consider 30% volume of C0¸ to be used
Design manual based on
desired flow rate
Therefore flow rate for 2 mins
Q = 41m³ (exp.30°C)
0.56m³/kg
=
0.56m³/kg @ 30°C
=
73.2kg
@ 2mins = 73.2kg
=
2min
Time of discharge of CO² at volume
=
Pipe sizing for flow rate,
Pipe size
Q
37kg/mins
185kg
37kg/min
=
=
37kg/mins
=
20mm
5mins
SWITCH – BOARD ROOM
Area
Volume
Nozzle coverage area
=
=
5.5x4.5
5.5x4.5x4.15
Nos Nozzle
Flooding Factor
weight CO²
Nos cylinder
30% Volume
=
=
=
=
=
25/28.28
=
1.35kg/m³ @ 50%
139kg
139kg/45kg
=
03x103m³
=
Q
=
=
=
= 31m³/0.56m³/kg (expansion 30°C) @ 0.56m³
= 56kg/2mins @ 2mins
=
Time Discharge
Pipe sizing Q
=
139kg/28kg/min
25m²
103m³
28.28m²
0.9 ≈ 1 no.
3nos
31m³
28kg/mins
=
5 min
=
=
28kg/mins
20mm
SCHEMATIC DRAWING FOR CO2
SYSTEM