Safety standards for tunnels
Take, for example, the Mont Blanc tunnel. With a length of 11.6 kilometers, it is currently the seventh longest mountain passage in the world. Before it reopened in March, a number of stipulations (that were not required for operation from the time of its opening in 1965 until the fire in 1999) now had to be fulfilled. These included additional escape and rescue routes. In this respect it was lucky that a tube running parallel to the tunnel already existed, although it had only been used as an access for maintenance work. This tube can be reached via 37 connecting corridors along the main tunnel and can now serve as a potential rescue route.
Hopefully, the tunnel will never have to be used as an evacuation route, but should the occasion arise, experts have to ensure that they can find their way. The 37 escape corridors to the emergency tunnel must therefore be well lit. The French company Comatelec was asked by the architects to design a lighting system for the Mont Blanc service and emergency tunnel. In fact, Comatelec has been responsible for the lighting systems in more than 85 percent of France’s tunnels.
In their efforts to comply with the regulations, the lighting specialists remembered a project they worked on together with SCHOTT’s subsidiary, SCHOTT-Rohrglas GmbH. Comatelec had chosen glass covers developed by SCHOTT glass for the lighting fittings they designed for the service tube of the Eurotunnel between England and France.
Restrictions regarding fire behavior
“Just as with the Eurotunnel, the lighting system in the Mont Blanc tunnel had to comply with all restrictions regarding fire behavior,” explains Philippe Gandon-Léger, Technical Director of Comatelec. For this reason, plastic was ruled out as an engineering material for the lamps. It had to be glass. Borosilicate glass from SCHOTT-Rohrglas is particularly heat- and chemical-resistant and is therefore used to produce various laboratory glassware.
The optical properties of the glass tubing are also important. “The lamps should not cast a beam of light just anywhere in the tunnel,” stresses Gandon-Léger. “What we needed was an evenly distributed illumination of the evacuation routes so that people can find their way. There should not be any dark areas.” With the help of a specially devised profile – in the form of prismatic grooves on the inside of the semi-cylindrical glass protector – the light is optimally and evenly dispersed in all directions, and the light loss is kept to a minimum.
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