Firefighter Speed and Tunnel Fire Testing: Insights and Innovations
Carrying out large-scale tunnel fire tests can be challenging but interesting for those involved. We asked two of RISE’s team members to give us some insight into their experiences.
The very first time Robert Harley Mostad set fire to hundreds of wooden pallets inside a repurposed road tunnel, he was taken by surprise by the forces created by the fire. Years later, Robert leads tunnel fire test projects and the fire extinguishment team in Norway. He says it is both an interesting and sometimes overwhelming feeling to start a working day in the tunnel, since there are many unknowns and things to consider.
Burn It to Learn It
Starting in fall 2021, Robert was joined by one of RISE’s then newest team members, Jan Erik Andersen, on-site in the Runehamar test tunnel in western Norway to perform large-scale fire and suppression tests. Jan Erik volunteered to go to the tunnel since it sounded like something unlike any experience he’d had before. After weeks of working in the tunnel as a technician, he says the experience to “burn it to learn it” has been awesome—or “knall” as Norwegians say.
Firefighter Speed in Rail Tunnel Experiments
In addition to tunnel fire tests, large-scale experiments have been conducted to study the searching speed and moving speed of firefighters without simultaneous hose build-up in a modern rail tunnel. The results support continued development of fire and rescue methods without secured water supply in smoke-filled tunnel environments further away from the fire.
Different activities during the experiments. A) search under train carriage, B) search from the rescue trolley, C) assisted movement with a stretcher and D) assisted movement with the rescue trolley.
Firefighting operations in underground environments can be complex and require significant resources. Firefighters can generally orient themselves easier in rail tunnels as the traffic requires relatively straight tunnels without major inclinations. If the tunnel has not been fitted with flammable condensation insulation, the surface and properties of the rock or concrete make the risk of flashover negligible except, for example, inside a train carriage or in technical enclosures. This means that the need for extinguishing water for self-protection further away from the fire is small and that the need for rapid and efficient movement during search and rescue motivates movement without simultaneous hose build-up.
Within the East Link project, a firefighting operation concept has been developed, where the firefighters’ movement mainly takes place in a parallel service tunnel, and where movement towards the fire in the affected tunnel tube is only performed from the nearest cross tunnel. The movement from the cross tunnel towards the fire is proposed to take place without simultaneous hose build-up when it can be done without risk to the individual firefighter. The concept for the East Link railway also considers the different technical installations inside the tunnel that are installed to assist the evacuees in case of emergency, such as handrails and walkway lights, which the fire and rescue services can use during movement in the tunnel.
Large Fire Size
The purpose of the tests was to document the efficiency of a water mist suppression system for Danfoss Fire Safety A/S. In the tests, with a potential 150 MW fire load according to SOLIT2 (Safety of Life in Tunnels) guidelines, 408 Euro wood pallets were stacked in the shape of a truck, combined with a 9-meter by 2-meter pool fire using diesel as fuel. The first fire was designed to represent a Class A fire of heavy goods vehicles (HGV). The largest fire load used involved several hundred pallets and diesel fuel. A large number of measurement points were used, both upstream and downstream from the fire. Heat release measurements were positioned downstream.
Large Fires Controlled
The results from the 150 MW potential fire tests showed that the fire load was reduced to below 44 MW after the activation of the water mist system. Moreover, the system prevented fire spread to a target placed 5 meters from the fire source. Key measurements included gas temperature, gas concentrations (CO, CO2, O2), visibility, heat release rate, and heat flux. The performance of the suppression system was evaluated according to SOLIT2 guidelines and NFPA 502, meeting the acceptance criteria.
After the Test is Complete, the Water Mist System is Turned Off, and Manual Extinguishing of Any Residual Fire is Performed. In the Centre of the Picture are the Wood Pallets Stacked into a Mock-Up that Simulates the Fire Load of a Heavy Goods Vehicle (HGV) Photo: RISE Fire Research.
The tests followed SOLIT2 guidelines, with some measurements adjusted for accuracy under the test conditions. Tunnel fire testing not only evaluates water mist system performance but also provides detailed and unique data for research and development in full-scale fire scenarios.
Artur Storm
artur.storm@ri.se
Robert Harley Mostad
robert.mostad@risefr.no
Mia Kumm
mia.kumm@ri.se
Jan Erik Andersen
robert.mostad@risefr.no
Lei Jiang
lei.jiang@risefr.no
Visit www.ri.se/en for more information.
