utilization of visibility monitoring for fire detection
TRANSCRIPT
BASICS OF VISIBILITY MONITORING
Continuous measurement of visibility and CO-concentration has been used for ventilation control in road tunnels for almost 40 years
Visibility is measured in units expressing the extinction of light over a certain distance, E/m (extinction per meter) or, more convenient, mE/m (milli-extinction per meter)
1 mE/m means the light intensity is reduced by a factor of 10 over a distance of 1000 meters
BASICS OF VISIBILITY MONITORING: UNIT
BASICS OF VISIBILITY MONITORING:
TYPICALLY MEASURED VALUES & LIMITS
Normal Traffic < 5 mE/m
Heavy Traffic ~ 5 mE/m
Traffic Jam ~ 7 mE/m
Closing of the tunnel 12 mE/m
Fire > 15 mE/m
VISIBILITY MONITORING AND FIRE DETECTION: WHAT IS MEASURED?
Visibility measures:
In normal operation: Soot from exhaust fumes,
wear debris from the tires, dirt particles, etc.
In case of a fire: Soot particles and other
products produced by the fire
Fog / Water steam (not desired!)
Fire sensor cables measure the temperature and react either above approx. 50°C or at a certain temperature gradient. In case of a fire, these conditions are only achieved in an advanced stage.
Visibility monitoring also detects cold smoke, typically produced in an early stage, or in case of a smoldering fire
Advantage visibility monitoring: it enables earlier warning!
VISIBILITY MONITORING AND FIRE DETECTION: COMPARISON WITH FIRE SENSOR CABLES
The visibility values increase quite quickly over 15 mE/m, however, this information was not used for fire detection
In the worst case, more fresh air is pumped into the tunnel by the ventilation system, based on the assumption that the emission is too high
Consequences: the fire gets more oxygen and the smoke is distributed in the tunnel
VISIBILITY MONITORING AND FIRE DETECTION: EXPERIENCE FROM FIRE INCIDENTS
SMOKE DETECTOR FIREGUARD
Measuring principle: stray light
No moving parts Response time: T90 in 5
second Integrated temperature
sensor Fog elimination with
heating elements (option) Signal output via relays or
Profibus DP Installation on the wall,
ceiling or in the intermediate ceiling of the fresh air channel
CONSEQUESCES FOR THE VISIBILITY MONITOR: INSTALLATION POINT
Where is the most ideal place for the system installation?
CONSEQUENSES FOR VISIBILITY MONITORING: INSTALLATION POINT
Smoke is normally concentrated under the ceiling
In-situ instruments are normally already mounted about 3 meters above the ground
Suction points for extractive instruments should also be mounted at the same height (currently they‘re about 1.5 meters above the ground)
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0
mE
/m
17:08:3020.04.2007
17:08:45 17:09:00 17:09:15 17:09:30 17:09:45 17:10:00
3
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1
0
Relais
VisGuard FireGuard Wand FireGuard Decke 1 (3m) FireGuard Decke 3 (3m) FireGuard Decke 4 (3m) Geräte Vortunnel
Relais:3: normal2: Voralarm1: Alarm0: Störung
CONSEQUENSES FOR VISIBILITY MONITORING: INSTALLATION POINT
CONSEQUESCES FOR THE VISIBILITY MONITOR: ALARM LEVEL
What signal levels can be expected during normal operation and in case of an incident?
Brandversuch 26.05.06
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00:00 02:00 04:00 06:00 08:00 10:00 12:01 14:01 16:01 18:01 20:01 22:01 24:01 26:01 28:01 30:01 32:02
CONSEQUESCES FOR THE VISIBILITY MONITOR: ALARM LEVEL
Brandversuch 26.05.06
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00:00 00:30 01:00 01:31 02:01 02:31 03:01 03:32 04:02 04:32 05:02 05:33 06:03 06:33
Zeit [Min.]
ST
[m
E/m
]
CONSEQUESCES FOR THE VISIBILITY MONITOR: ALARM LEVEL
Zoom: after approx. 30 to 60 seconds, depending on the distance of the visibility monitor from the fire, a limit of 30 mE/m has been exceeded. At the same time it could be demonstrated, that 30 to 50 m/Em is a realistic threshold for a smoke alarm
FIREGUARD: FIELD TEST GOTTHARD
Zoom: The instruments FireGuard ceiling 1 und FireGuard prototype (wall) give an alarm more or less simultaneously; the instruments FireGuard ceiling 3 (200m distance) and 4 (300m) react with a delay of 22 and 58 seconds, respectively.
30
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5
0
mE
/m
09:22:0002.03.2007
09:22:30 09:23:00 09:23:30 09:24:00
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0
Re
lais
FireGuard Prototyp (Wand) FireGuard Decke 1 FireGuard Decke 3 FireGuard Decke 4 Geräte Vortunnel
Relais3: normal2: Voralarm1: Alarm0: Störung
FIREGUARD: FIELD TEST NORWAY
The Norwegian Road Authority conducted a fire test in Norway (Runehamar) to compare the reaction and sensitivity of fire detection systems based on optical cables and stray light. The test demonstrated that both system detect fire quickly and reliably. However, stray light instruments detected the start of the car fire 2 ½ minutes earlier (because there was only smoke in the beginning)
FIREGUARD: FIELD TEST NORWAY
Direct fire (untypical) of 1 MW: Immediate response of the sensor cable, followed by the FireGuard. Note: a competitive unit made a self-test during the start of the fire and missed it!
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0
Trü
bu
ng
swe
rt [
mP
LA
= u
g/m
3]
11:0508.03.2007
11:10 11:15 11:20 11:25
dat
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Te
mp
era
tur
Bra
nd
kab
el L
ios
[°C
]
Brandversuch 3
FG 62.5m Int 60s Int 1s FG 125m Int 60s Int 1s VisGuard Int 60s Int 1s Visic610 125m Visic620 62.5m Visic620 125m ST450 62.5m Int 60s Int 1s ST450 125m Int 60s Int 1s Temperatur Lios Zündung Frühestens bei 62.5m Frühestens bei 125m
FIREGUARD: FIELD TEST NORWAY
Direct fire (untypical) of 0.1 MW: Sensor cable and FireGuard give alarm at about the same time. However, the alarm level for the sensor cable is based on very small temperature changes, hence there’s a higher risk of a false alarm!
800
600
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0
Trü
bu
ng
swe
rt [
PL
A =
mg
/m3
]
09:2008.03.2007
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dat
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Te
mp
era
tur
Bra
nd
kab
el L
ios
[°C
]
Brandversuch 1
FG 62.5m Int 60s Int 1s FG 125m Int 60s Int 1s VisGuard Int 60s Int 1s Visic610 125m Visic620 62.5m Visic620 125m ST450 62.5m Int 60s Int 1s ST450 125m Int 60s Int 1s Temperatur Lios Zündung Frühestens bei 62.5m Frühestens bei 125m
FIREGUARD: FIELD TEST NORWAY
Car fire (realistic incident): FireGuard triggered alarm after approx. 40 sec. The sensor cable only after more than 3 minutes! This is because in the beginning there was only smoke (in 90% this is the case!)
800
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200
0
Trü
bung
swer
t [P
LA =
mg/
m3]
16:0008.03.2007
16:01 16:02 16:03 16:04
dat
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Tem
pera
tur
Bra
ndka
bel L
ios
[°C
]
Brandversuch 7
FG 62.5m Int 60s Int 1s FG 125m Int 60s Int 1s VisGuard Int 60s Int 1s Visic610 125m Visic620 62.5m Visic620 125m ST450 62.5m Int 60s Int 1s ST450 125m Int 60s Int 1s Temperatur Lios Zündung Frühestens bei 62.5m Frühestens bei 125m
FIREGUARD: FIELD TEST NORWAY
Car fire (realistic incident): This graph shows now the temperature signal.The sensor cable reacted just a little bit before the temperature sensor which is built in the FireGuard.
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Tem
pera
tur
[°C
]
16:0008.03.2007
16:15 16:30 16:45 17:00
dat
Brandversuch 7 FG 62.5m FG 125m ST450 62.5m ST450 125m Zündung Frühestens bei 62.5m Frühestens bei 125m 'Temperatur Lios'
Visibility monitoring is now used not only for the ventilation control, but also for early fire detection
It allows to detect smoke and smoldering fires in an early stage
Real fires are typically detected 2 to 3 minutes ahead of fire sensor cables
For the installation, new requirements concerning the instrument density and mounting place have to be considered
Alarm levels for fire detection must be defined individually for each tunnel.
VISIBILITY MONITORING IN ROAD TUNNELS: SUMMARY