FIXED FIRE FIGHTING SYSTEMS IN TUNNELS INTEGRATION AND COMPENSATION Stefan Kratzmeir*, IFAB Institute for applied fire safety research, Rostock, Germany Max Lakkonen, FOGTEC Fire Protection, Cologne, Germany ABSTRACT After several years of discussion and enamours efforts in research and development Fixed Fire Fighting Systems (FFFS) in Tunnel, particularly based on water mist technology, are an accepted measure to increase the level of safety in road tunnels. Most systems that are already in operation or in construction, e.g. A86 West, M30 in Madrid or the Virgolo Tunnel on the Brenner Highway, are increasing the level of safety as these tunnels are presenting a high risk potential. However, tunnel owners and operator are confronted with the problem of exorbitantly rising costs for tunnel safety. Therefore the aim for any further innovations should be either to increase the today s accepted level of safety with no extra costs or to reach the level of safety by reduced costs compared when using measures that are prescriptive. Former research work has shown that most likely by implementing FFFS based on water mist technology other safety measures can be compensated partly. This might be the case e.g. for ventilations systems, passive fire protection or emergency exits. Depending on the specific project, this may lead to a significant decrease of costs for the total safety system of the tunnel. After the success of the SOLIT research project, which was funded by the German government during 2004 2006 and the even more extensive project SOLIT² will focus on the integration of FFFS into holistic tunnel safety systems as well as the compensation of other safety measures. A major part of the project will be the development of a method to plan and evaluate compensatory measures in a modular way. This will include a basic risk analysis as well as the cost benefit analysis for the state of the art solution as well as the innovative solution. Furthermore a method how to proof the effectiveness as well as the same level of safety is under development to be finally approved by a consultant. Based on an example of a upgrading of a tunnel ventilation system, the paper will give a brief overview about the process and methods developed by the partners of the SOLIT² project of planning and evaluating the implementation of a FFFS to partly compensate the power of a tunnel ventilation system. The aim should be to reach a state of the art level of safety by decreasing the costs for the refurbishment and improvement works. Fixed Fire Suppression Systems; Compensation; Integration 323
Fourth International Symposium on Tunnel Safety and Security, Frankfurt am Main, Germany, March 17-19, 2010 STATE OF THE ART OF FIXED FIRE SUPPRESSION SYSTEMS IN TUNNELS Figure 1: Spray test with water mist system [1] During the last years several tunnels throughout Europe where equipped with fixed fire fighting systems (FFFS) mainly based on water mist technology. Also today in few tunnels, e.g. the New Tyne Crossing in Newcastle, such systems are in the installation process. Within Europe more than 35 km of tunnel are equipped with FFFS but these systems can be seen in most cases as ad-on safety measure. They were installed to increase the level of safety but were not required according to rules or standards. Refering to the opinion of many experts the benefits of these systems are obvious. According to the work of several research projects, e.g. UPTUN or SOLIT, the main aims of these systems are [2]: Protect the tunnel structure and minimize the damages on the tunnel Hampering fire spread to adjacent objects, e.g. other trucks Facilitate the work of the rescue services Improvement of the self rescue conditions for people inside the tunnel The layout basis for all systems are full scale fire tests with severe truck fire loads as it were used during the SOLIT research project or e.g. for the Roertunnel. General recommendations for the system layout and minimum technical requirements can be found in the UPTUN guidance R251 [3] as well as in the latest version of the NFPA 502 [4]. Also PIARC recently published some recommendations for FFFS in tunnels. PROMISING RESULTS POTENTIAL FOR COMPENSATION The focus of the research projects in the past was to study the effectiveness of water mist systems in tunnel fires regarding the fire suppression and cooling effect. However during analyzing the data received from the full scale fire test it turned out that there are promising results giving already clear hints to partly compensate some other safety elements by using FFFS. This will be further explained in the following examples [5]: Ventilation In particular during the SOLIT fire tests using class B fire load up to 40 MW with a strong smoke potential it turned out that the effectiveness of the longitudinal as well as semi-transversal ventilation system was increased during the activation of the water mist system. In the fire tests with a longitudinal ventilation of approx. 1,5 m/s a strong back layering effect was observed during the pre-burn time. Shortly after activation of the water mist system the area upstream of the fire was completely free of smoke without changing the ventilation regime. Similar observations were also made during tests with a semi-transversal ventilation system. 324
Fig. 2: Smoke in the upstream area: Above during pre-burn time; below after activation of the FFFS Temperatures: The main fire fighting effect of water mist systems is the cooling effect. Due to the huge reaction surface in relation to the volume of the droplet a significant reduction of the temperature can be observed during activation of the FFFS. Even in a worst case the area of high temperatures can be limited to only few metres directly above the fire. During a free burning fire usually temperatures of 1200 C or even more can be expected in this area at the ceiling. After activation of the water mist system, the temperatures are immediately reduced to below 400 C in some tests and even below 50 C in distance of 10 m from the fire as it can be seen in Fig. 3. Figure 3: Temperatures along the tunnel during a fire test. FFFS activated after 4 min. Due to the lower temperatures the heat impact on the tunnel structure and infrastructure is significantly less. Therefore a reduction of the damages can be expected. Gas concentrations: Due to the limitation of the fire size and the fire suppression effect of the FFFS also gas concentrations are also reduced compared to an open fire. Therefore the effects on people are also reduced. The following table shows gas concentrations measured in fire tests with truck fire loads in comparison with fixed limit values from the literature and free burning fires. 325
Min./Max. concentration at breathing height Vol% during a fire test Fixed Limit Value for 30 min. exposure Vol% Free burning Fire (150 MW) Vol% O 2 19,41 15 CO 2 1,53 6-7 7-9 CO 0,22 0,14 0,16 0,4 3,0 By applying fractional effective dose models (FED) to the planning process of the overall safety concept, the time available for the self-recue of people can be estimated. COMPENSATION OF STANDARD SAFTEY ELEMENTS In general the term compensation in the field of safety engineering can be defined as achieving the same level of safety by other measures or methods than described in rules or standards. Prescriptive rules and guidelines were often used in the past and usually are now defining the accepted level of safety in the tunnel. Particularly for extensive projects standard measures may lead to a high complexity or high costs. Furthermore if the safety level should be increased, e.g. due to new knowledge or for better social acceptance, the costs are usually increasing disproportionately. Therefore the trend to a performance based design of safety systems is obvious. The aim the will be, as shown in Figure 4 that the safety level can be increased with the same costs or that same level of safety can be kept by reducing the costs. Safety level Increasing Safety Level same costs Todays accepted safety measures (prescriptive) Increasing Safety Level higher costs Same Safety Level less costs Costs of the safety system Figure 4: Correlation between the safety level and the costs of a safety system (schematic) The general chance from a prescriptive way of planning complex tunnel systems to a holistic approach opens the possibility to individually design the tunnel safety system. Based on a risk analysis the safety system can be build up with from a tool box of measures e.g. containing passive fire protection, ventilation systems, self-recue concepts, active fire suppressions system and the rescue services. Even 326
the EU tunnel directive gives the chance to use innovative measures as long as it can be proven that the same level of safety as defined in the standard will be achieved. Of course for performing a holistic approach in designing an overall tunnel safety concept the effectiveness of all measures and the potential of compensation must be checked. In particular for FFFS this information is only available in a qualitative way but there is still a lack of quantitative and reliable data. In a second step an overall cost analysis must be performed. This is not only including the cost for implementing any system but also the life-cycle-costs of the system. In a third step questions regarding reliability of the systems should be examined and systems should be compared to each other. Up to now, even for systems that are well know since years, hardly any data is available for this task up to know. It can be summarized that test results already showed a great potential in reducing costs or increasing the level of safety by partly compensating today s used standard safety measures with FFFS. But still some data is needed for FFFS as well as for other systems. PROSPECTS AND FUTURE WORK Its was clearly identified by in the expert world that future research work must be carried out to create a reliable base for integration of FFFS into the tunnel safety system and compensation of other safety measures. The German government just recently launched the new research project SOLIT² (further information: www.solit.info). A consortium including FOGTEC, STUVA, BUNG, University of Bochum and TÜV Süd will deeply investigate the possibilities of including FFFS into the risk analysis process and therefore compare the effects of FFFS and other safety measures in a holistic process. To verify the models and methods developed within the project an extensive fire test program will be carried out during 2011. Furthermore the focus will be set on life cycle cost models for FFFS and in comparison with other safety measures. This will be a helpful tool to decide the most cost effective combination of safety measures seen over the whole life time of the systems and the tunnel. After finalizing the project works the results will be published as an engineering guidance to assist consultants, tunnel owners, operators and authorities that are dealing with tunnel safety. Up to now, there are no fixed rules and methods how compensation of safety measures in tunnels should be determined. But it can be assumed that this will be change within a very short period of time and also organisations as PIARC or NFPA 502 will include these topics in their procedures and recommendations. REFERENCES 1. FOGTEC Fire Protection, Cologne 2. Kratzmeir, S. and Starke H., SOLIT Safety of Life in Tunnels: Forschungsbericht, Bundesministerium für Wirtschaft und Technologie, 2007. Not public 3. UPTUN Guidance R251: Engineering Guidance for Water Based Fire Fighting Systems for the. Protection of Tunnels and Subsurface Facilities. 2006 4. National Fire Protection Association: NFPA 502 Standard for Road Tunnels, Bridges, and Other Limited Access Highways. Issue 2008 5. Kratzmeir S. Substitution Promising results, challenge for the future ITA-COSUF / IMWA workshop Fire Suppression in Tunnels: 2.3-4.3.2008 Munich 327