Sealing escape routes against fire hazards 24 Aug 2017

Managing the risk of transporting hazardous materials through tunnels is high on the fire life safety agenda of operators. Disasters and near-accidents over recent times have imposed strict requirements on the fire-resistance and fire-protection of tunnels used to transport hazardous goods such as oil, petrol, gas or chemical products.

Sealing joints and openings is part of a comprehensive fire safety system

Fire-resistance of a tunnel must cover the systems used to seal escape route doors, openings for cables and pipes and fully seal escape routes from the dangers of smoke, heat, flames and toxic fumes.

Beele Engineering of Aalten in the Netherlands provides a wide range sealing materials including Nofirno which combines a high degree of fire resistance for sealing openings for cables and pipes against gas, water and smoke.

For the cut-and-cover Victoria Park road tunnel in New Zealand, Beele developed a special fire-resistant sandwich system, known as Actifoam Ultra, to seal the joints between the internal dividing wall of precast concrete panels and between the precast concrete wall panels and the roof. With 4,000m of the material incorporated into the tunnel, the system ensures that, in the case of fire, the escape routes will stay clear of smoke, heat, flames and toxic fumes.

Atifoam Ultra consists of several layers of Actifoam and Rise Ultra rubber, which together guarantee the best degree of fire resistance. The material is easy to process and can be pressed in so that it clamps securely into openings. Fire resistance can be improved still further by finishing the edges of the sandwich sheets with Nofirno sealant. In the case of fire, this sealant forms a ceramic protective layer which ensures that the Actifoam Ultra material remains intact and can do its work.

Escape routes must be protected from fire, smoke, heat and toxic fumes

To guarantee security and safety within the escapes routes, the fire-resistant sandwich system has been subjected to stringent two-hour fire tests. These hydrocarbon fire tests mimic real life situations that can occur in tunnels where hazardous materials are being transported. Burning tankers or trucks with chemicals can very quickly reach temperatures of up to 1,100°C. This rapid and extreme heat rise imposes heavy demands on fire-resistant sealing systems.

In contrast to the usual tests, which normally take an hour, the Actifoam Ultra material has been tested successfully for fire resistance through a two-hour period and at temperatures of up to 1,250°C. The sealing remained intact throughout the fire test, with no gaps appearing. After two hours of exposure to extreme temperatures, the temperature on the other side of the wall rose by only 10°C.

The flexibility of the sandwich construction ensures that the changing loads and traffic vibrations are absorbed, and that protection is offered against the water pressure arising from the water table.