utilization of visibility monitoring for fire detection

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UTILIZATION OF VISIBILITY MONITORING FOR FIRE DETECTION

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UTILIZATION OF VISIBILITY MONITORING FOR FIRE DETECTION

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

FIREGUARD INSTALLATION: WALL MOUNTING

FIREGUARD INSTALLATION: MOUNTING ON THE CEILING

FIREGUARD INSTALLATION: MOUNTING IN THE INTERMEDIATE CEILING

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)

40

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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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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.

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mE

/m

09:22:0002.03.2007

09:22:30 09:23:00 09:23:30 09:24:00

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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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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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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

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A =

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/m3

]

09:2008.03.2007

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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!)

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bung

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t [P

LA =

mg/

m3]

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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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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