Engineering Guidance for Water Based Firefighting Systems for the Protection of Road Tunnels

The advantage of Active Fixed Fire-Fighting Systems (FFFS)

Amr Mahmoud, MSc., EITSenior Fire Protection Engineer

Agenda• Background• Fires in Road Tunnels• Fire Alarm and Detection• Smoke Control Systems in Tunnels• Water Based Fire-Fighting Systems• Types of Water Based Fire-Fighting Systems• FFFSs Current Practice and Recommendations• Case Study – Underground Road Tunnel• Q&A

Background

Road Tunnels• Geometrically Simple – a Tube / Box

Road Tunnels Categorization – NFPA 5021) Category X - Where tunnel length is less than 90 m (300 ft)2) Category A - Where tunnel length is 90 m (300 ft) or greater3) Category B – Where tunnel length equals or exceeds 240 m (800

ft) and where the maximum distance from any point within thetunnel to a point of safety exceeds 120 m (400 ft)

4) Category C - Where tunnel length equals or exceeds 300 m(1000 ft)

5) Category D - Where tunnel length equals or exceeds 1000 m(3280 ft)

Fires in Road Tunnels

Fires on Cars/Truck in Road Tunnel• Fires continue to the adjacent cars• Not always possible to reach the source of fire• Truck catches fires in Tunnel• Cars accident in Tunnels

Protection Targets in Tunnels• Personal Safety• Structural Safety• Support/Facilitate Emergency Rescue• Fire Fighting

Purpose and Use→ What are you trying to achieve?

Provide Guidance for the incorporation of fixed water-based fire-fighting systems inroad tunnels.

→ What are the fire protection systems to use?Automatic Fire Detection Systems, Manual Fire Detection Systems, Smoke ControlSystems, and Water Based FFFSs.

→ What is the evidence of the effectiveness of the FFFSs?Fire Test Protocols , while there are not currently any standard fire test protocols forthe evaluation of fixed water- based fire-fighting systems intended for installation inroad tunnels, ongoing work in Europe has resulted in an “ad hoc” series of testsintended to quantify system performance

Fire Alarm and Detection Manual Fire Alarm Boxes – Shall be used in Categories B, C, and D

Manual fire alarm boxes mounted in NEMA Enclosure Type 4 (IP 65) or equivalentboxes shall be installed at intervals of not more than 90 m (300 ft) and at all cross-passages and means of egress from the tunnel.

Automatic Fire Detection Systems – Shall be used in Categories B, C, and D• Automatic fire detection systems shall be capable of identifying the location of

the fire within 15 m (50 ft).• Automatic fire detection systems shall be able to provide detection in the early

stages of a developing fire within the tunnel under anticipated air velocity.

Smoke Control Systems in Tunnels

Modelling of Tunnel Fires

Water Based Fire-Fighting Systems

• WFS use water in the form of droplets:• Very small droplets “High Pressure

Water Mist Systems”• Relatively large droplets “Deluge or

Sprinkler Systems”

• The main fire fighting effect are used by all WFS, depending on the droplet sizes:

• Cooling• Suffocation of the Fire• Separation Effect• Shielding Effect• Protection of the Tunnel Structure

Tunnel Closure and Traffic Control

The Role of Fixed Fire-Fighting System• Provide early suppression and subsequent

management of fire.• Delivery of sufficient water to the fire site• The fire bridge to manage the fire incident without

putting themselves at risk• Remove heat from the environs of the fire by cooling

the surrounding area during an incident• Limit the potential for fire to spread between

vehicles• Extend the available escape time for tunnel users

(ASET)• Reduce the extent of structural damage

The Effect of FFFSs in Tunnels

• Temperature and Radiant heat

Schematic view of area with high temperatures during a truck fire with FFFS

Schematic view of area with high temperatures during a truck fire without FFFS

The Effect of FFFSs in Tunnels• Progression and Spread of Smoke

Disappearance of the smoke layer with activated FFFS

Layer of smoke in a 30 MW liquid fire shortly after ignition

Types of Water Based Fire-Fighting Systems• Deluge Sprinkler System• Deluge Water Spray Systems• Deluge Water Mist Systems• Deluge Foam Systems

Selection of System Technology

Evidence of Effectiveness

• Full Scale Fire Test• 4-6 MW for cars (minimum 6

cars)• 100 MW for HGV• 200 MW for HGV with Hazards

Materials

FFFSs Current Practice and Recommendations• Nozzles are normally installed under the ceiling

or at the upper part of the side walls, pointing downwards or at the center of the tunnel.

• Nozzles are grouped into sections, each sections shall be shorter than 30 meters, and each section shall cover the tunnel “from wall to wall”.

• All sections are connected by section valves and a main water supply line to the pump unit.

• In the event of activation of the WFS at least two section valves will be opened accordingly.

• Standpipe systems shall be designed and installed as Class I systems in accordance with NFPA 14

• The water supply shall be sufficient such that the WFS provides the required flow rate of water for a minimum of 60 minutes

Case Study – Underground Road Tunnel

Case Study –Underground Road Tunnel• Tunnel Category: Category D

• Potential fire risk: HGV

• Level of protection: Fixed fire-fighting System

• Tunnel geometry: Flat ceiling with 6m wide and 6m in height

• Ventilation conditions during fire: Longitudinal ventilation

• Performance of a fire detection systems: Very Early Air Sampling Smoke Detection

• Activation mode of the WFS: Detection System or Manual

Case Study –Underground Road Tunnel• The whole tunnel is covered by

Deluge water spray system

• Tunnel divided to 36 sections butin no case sections shorter than 30meters.

• All sections are connected byDeluge valves.

• In event of activation of the WFS,three section valves will openaccordingly

• Water supply sufficient for 60minutes

Thank You!