SECTOR | ROAD TUNNELS/SAFETY
test method to document from tests also at Runehamar how, using SEM-SAFE®
, the required safety
and protection can be achieved. The successfulness of fire tests is measured based
on pass and fail criteria. The test method describes the mock-ups to be used to represent truck fires as well as tanker fires by implementing such internationally recognised methods as those of the Safety of Life in Tunnels 2 (SOLIT2) projects, the PIARC – World Road Association, and NFPA 502, which give recommendations on the peak heat release rates of fires in these vehicles. The NFPA 502 standard groups tunnels into 4 categories. More details are listed in Table 3. Tests on trucks and tankers have shown how
the system guarantees people both upstream and downstream of fires sufficient time to self-evacuate,
Table 1: Tunnel category definitions and FFFS requirements Tunnel category X A B C
Description <90m
90m +, <300m 300m+, <1km 1km+
Table 2: Dimensions of Runehamar test tunnel, Norway Description Width Height
Cross-section Length
to determine whether fire brigades can enter the tunnels and extinguish any remaining fires manually, and to evaluate the structural impacts. Although the aim was to provide people a minimum of 10 minutes for self-evacuation, the system gives extra minutes to get to safety.
Sustainability criteria taken into consideration were: ● people: visibility, temperature, heat radiation, exposure to gases (e.g., CO, CO2
)
● fire brigades: visibility, temperature, heat radiation, fire spread, heat release rate (HRR) maximum peak. all parameters were successfully kept below the threshold during the entire duration of the tests
● structure: HRR maximum peak, temperature. All parameters were kept on the safe side
Fixed Fire Fighting Systems (FFFS) Not required Not required
Required, except as specified in NFPA 502 Required
Dimensions
9m (7m paved for the two car lanes) 6m
50m2 1650m
Table 3: Peak Heat Release Rate (HRR) recommendations for different vehicle types per NFPA 502, and PIARC-World Road Association
Vehicle Type Passenger car
Multiple passenger cars Light duty vehicle Bus HGV
HGV <=25 tonnes HGV 25-50 tonnes Tanker
Peak HRR (MW) per NFPA 502
5-10 10-20 20-30 70-200
30-50 70-150
200-300 200-300
15 20
Peak HRR (MW) per
PIARC-World Road Association 5-10
All measured parameters were successfully kept below the threshold during the required time during the fire tests. The full-scale fire test documented that the
ventilation velocity can be reduced to approximately 1m/s while still preventing backlayering since the high- pressure water-mist system effectively suppresses fires. The test method and criteria for successfully passing
the tests were approved by Underwriters Laboratory (UL), an internationally recognised and independent verification and certification company, that witnessed the fire tests and verified the tests and their accuracy. The pipes of the Danfoss system are up to 70%
smaller than those of traditional systems used for protecting tunnels. This is due the fact that high-pressure water mist nozzles have low water consumption, and the pump unit is less sensitive to pressure loss. The system uses press fittings, eliminating welding, and the smaller pipes weigh less. Consequently, the system is faster and less expensive to install, uses less materials and water, can have lower maintenance costs, and its lifetime is longer than that of traditional systems.
SAMRUDDHI TUNNEL, INDIA The Mumbai-Nagpur Expressway project in Maharashtra state, India, is being developed over a very long distance – 778km – and an important part of its construction is the 8.2km-long twin-tube Samruddhi road tunnel. The tunnel is meant to facilitate India’s journey
towards urbanisation and economic growth. It was built with sustainability in mind to support the country’s green transition policy. The 17.6m-wide Samruddhi tunnel is one of the
widest and longest road tunnels in India, and also with Danfoss’ SEM-SAFE®
system is the first time that a high Above, figure 2: Danfoss’ SEM-SAFE® high-pressure water-mist nozzle spraying water 32 | July 2024
pressure water-mist extinguishing system has been employed for fire safety in the country’s road tunnels. The system (pump units, section valves, nozzles, pipes, and fittings) was installed by Danfoss as part of the fire safety package that also included technical design, engineering capabilities, and site supervision.
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