Urs A Ruferner describes the design, installation and maintenance of fire systems in six road tunnels housing new stretches of motorway in Switzerland.
Siemens Building Technologies division has provided the fire safety systems for all the tunnels in one of largest road infrastructure projects of recent years in Switzerland: the A3 Zurich-West bypass and the A4 connection to Zug through the Knonau district. These two stretches of the motorway network – most of which runs underground – have a significant regional importance: the new sections (respectively 10.6 km and 15.6 km) offer quicker connection between Zurich and central Switzerland, a reduction of through traffic in numerous municipalities and in the city of Zurich, as well as new potential for public road transport.
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Linear heat detection is used through the tunnels |
The new motorway sections run through six tunnels, including the Uetliberg tunnel (4,400 m long) and the Islisberg tunnel (4,950m), the opening of which in the autumn of 2009 marked the completion of this decade-long project. All in all, a total of 27.8 kilometres of tunnel tubes were constructed.
Fire safety systems
Safety was a central consideration in the design, construction and subsequent operation of the tunnels. In order to simplify installation, operations, maintenance and services, the requirement was for similar technical equipment to be used throughout all the tunnels. The fire safety systems, therefore, had to be adaptable and scalable enough to provide each tunnel with the levels of safety performance required by Swiss Federal Roads Office (FEDRO) regulations, while catering for the specific challenges of each tunnel.
Due to the confined environment, early fire detection and accurate location is essential to safety and reducing the potential for the spread of fire. In total, Siemens installed 36.5 kilometers of FibroLaser linear heat detection cable as well as 24 FibroLaser II controllers, which are connected with six segment controllers (one per tunnel). These segment controllers are networked with the overall tunnel control systems. This enables a coordinated response to any incident, through interaction of the fire safety systems with the lighting, ventilation, smoke extraction, traffic control, video surveillance and communication systems. For example, the detection of a fire inside the tunnel will trigger the ventilation system to switch to ‘emergency mode’, so it extracts air from the affected area to prevent the build-up of smoke.
The redundant fibre optic cable FibroLaser can detect a fire within one minute and pinpoint its location with an accuracy of three metres of the ignition point - a performance which exceeds the most stringent European road and rail safety standards. The system is constantly tested during operation, ensuring high system availability. For routine service, system tests are carried out away from the tunnel tubes, and therefore do not require tunnels to be closed.
Nerve centres
Systems and electromechanical equipment vital to the safe and smooth operation of the tunnels are housed in around 500 technical rooms, of which approximately half are fitted with distribution and control cabinets. Siemens also equipped all the technical rooms of the tunnels with separate systems consisting of 1500 Sinteso C-LINE smoke detectors and alarm signaling devices. In case of an emergency, they shut down any local ventilation system in order to enable alarm verification and to prevent a high air flow from fuelling a fire. They also alert the tunnel control centre in Urdorf as well as the traffic control center via the superordinate control system and the emergency response system.
The protection of critical operational systems from damage by fire is ensured through Siemens as part of its Advantage Services offering. These comprehensive services optimise the systems’ operational efficiency while reducing the probability of any disruptions. For these tunnels, the services include life-cycle management, operational services and alarm management as well as preventive and corrective system maintenance, knowledge services (sharing expertise with customers through consulting, professional services, or training) – along with a guaranteed repair time within 24 hours. The services are designed to create real system value over the whole life-cycle of the tunnels, keeping systems running at optimal efficiency and increasing reliability and ongoing tunnel availability.
Urs A. Ruferner is responsible for tunnels within the fire safety applications & offering team, Siemens Building Technologies
