Fire Protection in tunnels

The first major projects were for nuclear power plants, since the multiple electrical systems installed there also had to be protected against the consequences of any fires. By using PYROFIL safety cables in combination with PYROSYS installation and fixing systems supplied by Dätwyler, electrical functions could be maintained for a certain length of time in the event of fire (between 30 and 90 minutes, depending on requirements). On the basis of this experience an extensive range of safety cable systems came into being for use in buildings occupied by large numbers of people (such as high-rise buildings, office buildings, hospitals, airports, etc.), wherever the functioning of vital systems had to be maintained in the event of fire. The technological leadership of safety cable systems from Dätwyler is demonstrated by the fact that we are still No. 1 in Germany, our main market.

In principle, PYROFIL safety cables are also suitable for use in other fields where it is important to maintain electrical functions for a certain period of time in the event of fire. For example, PYROFIL cables are also installed in underground railways and other transport facilities. These applications have induced us to develop an actual "safety system" for tunnels, similar to that we have already produced for the construction sector. Our cooperation with the relevant government authorities, planners and engineering firms proved extremely beneficial in this context.

After the devastating fires in the Mont Blanc and Tauern tunnels, safety standards in Swiss tunnels were the subject of a detailed study conducted on behalf of the Department of the Environment, Transport, Energy and Communications (UVEK). As a first step, the safety of tunnels on Swiss motorways was investigated by the Federal Office for Roads (ASTRA) in 1999. In mid-September 1999 the Federal Transport Office (BAV) launched a study of safety in rail tunnels.

Analysis of rail tunnels 
(Report on safety in Swiss rail tunnels - BAV analysis dated January 22, 2001)

• 84% of the 689 tunnels reviewed are rated as problem-free as regards safety.
• Additional measures need to be examined in the case of 84 tunnels between 300 and 3000 metres long.
• In 26 tunnels, most of them over 3000 metres long, the BAV also considers additional measures to be warranted as regards facilities for rescuing oneself and others. These include:
  • footpaths and handrails 
  • (emergency) lighting
  • ventilation 
  • marked escape routes 

Analysis of road tunnels 
(ASTRA Tunnel Task Force - final report dated May 23, 2000)

It is apparent from the report by the ASTRA Tunnel Task Force that safety in road tunnels depends largely on the following four factors: "road users, infrastructure, operation, vehicles". In the "infrastructure" sector, which is of relevance for our products and services, the following principle was among those set out:

"The guidelines and requirements for equipping the tunnels must be updated to the latest state of the art. They include criteria for the employment and installation of tunnel equipment as well as a timetable for their implementation, and also stipulate so-called integrated functional tests. The guidelines include all components of the facilities, such as power supplies, lighting, ventilation, signal control, measuring and monitoring systems, central communications and information, cable connections, ancillary equipment and electromechanically related structural systems. An inspection is triggered by any new findings of a technical nature or of relevance for safety ".

Among experts it is also largely agreed that - in the "infrastructure" segment - tunnel ventilation plays a central role in preventing or limiting the spread of smoke or gas in the event of fire. The ventilation system is virtually the only immediate life-saving measure (presupposing the operation of the fire detection facilities) which can take effect immediately after a fire occurs. Equipped with individually adjustable flaps along the ceiling of the tunnel, a system of this kind can bring its entire capacity to bear exactly over the seat of the fire and thus efficiently extract smoke and toxic gases from the danger zone (see drawing). This itself is what then makes immediate evacuation and fire-fighting possible!

So what contribution can Dätwyler make with its products and services towards the implementation and ongoing improvement of safety systems in tunnels? The above extracts from experts' reports make it clear that electric cable installations in the segments of power supplies and data transmission are extremely important! In other words: What is the use of ingenious facilities to protect life and property, such as ventilation systems and flap controls, or monitoring, alarm, evacuation and fire-fighting systems in general, if power and data transmission break down in the event of fire and these very systems fail in an emergency?

National and international guidelines already exist on the subject of "the behaviour of electric cables in the event of fire", of course. However, these guidelines only define minimum standards for cables and do not enable conclusions to be drawn regarding other important aspects such as correct dimensions and installation, or regarding components such as mounting systems or fastening and attachment elements, etc.

Dätwyler Cables+Systems sets new standards here. It was already clear to us some years ago that only totally coordinated and tested cable systems can be fully effective in an emergency. In close cooperation with partners in the field of preventive fire safety, cable systems were developed which guarantee constant power and data transmission over a defined period of time in the event of fire and thus provide the backbone for integrated safety. The functioning of our systems can be demonstrated at any time by extensive series of tests in large-scale furnaces. At various technical conferences and certification courses Dätwyler Cables+Systems also offers the necessary support for the planning and professional installation of these systems.

To summarize: these complex tasks therefore require more than just safety cables complying with national or international specifications. What is called for is a cost/benefit-optimized, totally coordinated and tested cable system which also guarantees the functioning of "vital" safety systems in the event of fire!
The solution: PYROFIL safety cables combined with PYROSYS installation and fixing systems from Dätwyler.

The Dätwyler approach to integrated safety in rail and road tunnels!
The drawing illustrates our comprehensive "Fire Protection in Tunnels" system. This concept was based on our long-term, proven know-how in safety engineering in the construction sector. On this foundation we have developed existing solutions further in conjunction with experts from Swiss Federal Railways and ASTRA and adapted them to conditions specific to tunnels. The outcome is an innovative overall system in the field of electric cable systems with functional integrity which undoubtedly sets new safety standards and defines the current state of the art. In our case innovation does not, for example, stand for the development of a single component, but much rather for an integrated approach, coupled with the ability to analyze processes which are critical for safety, evolve relevant concepts as solutions and implement them in a reliable overall system.

With its trend-setting and proven PYROFIL/PYROSYS safety cable system, Dätwyler makes a major contribution to tunnel infrastructure and thus plays an essential part in minimizing the effects of disastrous fires such as those in the Mont Blanc, Tauern or Gotthard tunnels and ensuring the best possible protection of life and property.