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Workshop on Fire Protection at Research Facilities

Join us at the workshop to learn about the status of the cable evaluation project at CERN, presented by Tristan Hehnen, doctoral student at CERN and Bergische Universitaet Wuppertal.

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Workshop on Fire Protection at Research Facilities

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  1. Workshop on fire protection at research facilities 21-22 January 2015 ESS, Tunavägen 24, Lund Status on cable evaluation project CERN By Tristan Hehnen Doctoral student CERN and Bergische Universitaet wuppertal Document reference

  2. Table of contents • Introduction • Situation at CERN • Brief overview • Introduction • Used literature • Simplified approach • Fire load calculation • Cable tray fire scenario • Ideas for further research • The Ph. D. thesis • Influence of input parameters on the fire simulation • Cone calorimeter simulation • Literature Document reference

  3. Introduction • Member of the Doctoral Student Programme at CERN • Work supported by the Wolfgang-Gentner-Programme of the German Federal Ministry of Education and Research (BMBF) • Doctoral student at the Bergische Universität Wuppertal • Department: Computer Simulation for Fire Safety and Pedestrian Traffic Supervisor: Saverio La Mendola Supervisor: Armin Seyfried Duration of the doctoral programm: from Nov. 2014 to Nov. 2017 Document reference

  4. Situation at CERN Brief overview • Huge amount of electrical equipment like electrical cabinets, server racks and cable trays • Thousends of kilometers cable length Pictures: CERN Document reference

  5. Situation at CERN Brief overview Pictures: CERN Document reference

  6. Situation at CERN Introduction • To assess the fire threat to a specific structure, CERN utilises fire codes and the basic literature in the field of fire science. • For specific situations, an investigation on this topic is conducted by reviewing the basic fire science journals and reports. • To cope with (possibly) reoccurring situations, simplified models and guidelines are created. • For more complex situations, simulations with different complexity (zone model, CFD) are conducted. Both: to make a risk assessment or to create simple models. Document reference

  7. Situation at CERN Simplified approach • For cable fires some work had been done by Fabio Corsanego DGS/SEE, based on the CHRISTIFIRE project conducted by U.S.NRC. Some examples of this are given here (see following slides for more details). • He derived a conservative and simple model to estimate the fire load of cables inside a tunnel (EDMS No.: 1405658 ver. 1). • He also derived guidelines for values to be used for design fires and simplified the FLASH-CAT code into an Excel-sheet to get ERR curves for design fires (EDMS No.: 1357073 v1.0). • A general idea for the future is to create a catalogue of design fires or simple models to cope with the different fire situations. Document reference

  8. Situation at CERN • Estimate the total transversal section of the cable • Calculate the specific cable mass per tunnel length (proposed: 2500 kg/m³) • Calculate the amount of plastic (proposed: 0.5) Fire load calculation (EDMS No.: 1405658 ver. 1) Document reference Pictures: CHRISTIFIRE, phase 1

  9. Situation at CERN Fire load calculation (EDMS No.: 1405658 ver. 1) • Calculate the fire load per tunnel length (proposed: 20 MJ/kg) • Calculate the fire load per floor surface Pictures: CHRISTIFIRE, phase 1 Document reference

  10. Situation at CERN Fire load calculation (EDMS No.: 1405658 ver. 1) • The proposed heat of combustion is a average value of 23 cables tested in the CHRISTIFIRE project (phase 2, table 4.1). The value is 17.6 MJ/kg and a standard deviation of 4.4 MJ/kg. • For the proposed density of the cable tray and the amount of plastic per cable the respective average for three different cable types (Hi current cables, power cables, signal cables) was calculated, according to the data of the cable producer. Picture: CHRISTIFIRE, phase 1 Document reference

  11. Situation at CERN Cable tray fire scenario (EDMS No.: 1357073 v1.0 ) • The cable tray fire scenario consists of horizontal cable trays which are stacked upon each other. The fire is expected to start in the lowest tray and spreads to the trays above. This is concidered as a worst case szenario. • Via CHRISTIFIRE a model was created to simulate this behaviour. It was adapted for CERN in an Excel-sheet. Pictures: CHRISTIFIRE, phase 1 Document reference

  12. Situation at CERN Cable tray fire scenario (EDMS No.: 1357073 v1.0 ) • In CHRISTIFIRE experiments in different scales were conducted: Micro-combustion calorimetry, tube furnace, cone calorimeter, radiant panel apparatus, full scale test Pictures: CHRISTIFIRE, phase 1 Document reference

  13. Ideas for further research The Ph. D. thesis • There are only few / simple models in use at CERN, like the horizontal and the vertical spread of flames. • Questions arise e.g. at the connections of both situations, when trays branch out, different tray geometry or at the connection of different electrical equipment (e.g. Electrical cabinet – cable trays). • A more detailed and general understanding of the geometrical relationship between flammable objects (cable trays) should be acquired. Picture: CERN Document reference

  14. Ideas for further research The Ph. D. thesis • As an approach fire simulations of different geometrical configurations are to be carried out. • A starting point are some of the findings of the FIPEC programme: the distance between single cables or bundles of cables influences the fire spread (fastest with one diameter spacing for vertical trays). • Are the same findings true for „higher dimensions“ like trays? • What happens with very large bundle diameters? • Based on this results simple models may be invented. Picture: CERN Document reference

  15. Ideas for further research The Ph. D. thesis • A „mock-up“ material ought to be created for FDS simulations. Cable fires are not easy to simulate because of their high amount of conductor material (e.g. Cu or Al). • By this method the simulations should be better comparable with fire experiments, which are thought to be done for validation. • A transfer of the findings to other situations could be possible, e.g. electrical cabinets. • The creation of the „mock-up“ material seems to be possible, concerning for example the work of C. Trettin (and also other who are not mentioned here). Picture: CERN Document reference

  16. Ideas for further research Influence of input parameters on the fire simulation • C. Trettin of the University of Wuppertal carried out some work to transfer experimental data to the Fire Dynamics Simulator FDS. • For the pyrolysis thermogravimetrical analysis TGA were conducted and simulated, as in the FDS User Guide proposed. Variation of: heating rate (5 K/min, 60 K/min to be comparable with cone), O2 concentration (21 %, 10 %) and material (ABS, PMMA, PU, particle board) Comparison of particle board simulation and TGA Picture: C. Trettin Document reference

  17. Ideas for further research Influence of input parameters on the fire simulation • To account for the thermal properties of the specimen cone calorimetry tests were conducted and in a simplified way simulated. • The heating rate in cone experiments was found in the literature to be between 60 K/min to 80 K/min at a heat flux of 50 kW/m². Comparison of particle board simulation and cone calorimeter Picture: C. Trettin Document reference

  18. Ideas for further research Cone calorimeter simulation • Detailed simulation of the Cone Calorimeter including the gas phase • Uniform mesh, cell size: 2 mm • Number of cells: 125,000,000 (whole), 1,969,920 (only cone and specimen) Pictures: T. Hehnen Document reference

  19. Thank you for your kind attention! Are there any questions? Document reference

  20. Literature Excerpt • Influence of input parameters on the fire simulation, Trettin, C., Hagemann, P., Werrel, M., Wittbecker, F.-W., PROCEEDINGS Fire and Evacuating Modelling Technical Conference (FEMTC) 2014, Gaithersburg, Maryland, September 8-10 • Babrauskas V. Ignition Handbook. Fire Science Publishers, Issaquah, WA 98027, USA, 1th edition, 2003. Co-published by the Society of Fire Protection Engineers. • Karlsson B., Quintiere J. G. Enclosure Fire Dynamics. CRC Press LLC, Boca Raton, Florida, 2000. • Drysdale D. An Introduction to Fire Dynamics. John Wiley & Sons, Southern Gate, Chichester, West Sussex PO19 8 Q, England, second edition, 1998. • Safety request form: “Request to characterize the burning behaviour of a vertical stack of horizontal cable trays.”, Answered by: F.Corsanego DGS/SEE, EDMS No.: 1357073 v1.0 • Technical Note: “Fire modelling tools: Parameters for vertical and horizontal cable tray fire modelling. Results from real-scale tests.”, F.Corsanego, DGS-SEE, EDMS No.: 1097020 ver. 1 • Guideline: “Fire modelling tools: Quick method to calculate the fire load of cable trays and cable ladders .”, F.Corsanego, DGS-SEE, EDMS No.: 1405658 ver. 1 Document reference

  21. Fire Performance of Electric Cables – new methods and measurement techniques, Final Report on the European Commission SMT Programme Sponsored Research Project SMT4 –CT96-2059, Interscience Communications Limited, West Yard House, Guildford Grove, Greenwich, London SE10 8JT, UK • Cable Heat Release, Ignition and Spread in Tray Installations During Fire (CHRISTIFIRE) Phase 1: Horizontal Trays, NUREG/CR-7010, Vol. 1, U.S.NRC, July 2012, McGrattan K., Lock L., Marsh N., Nyden M., Bareham S., Price M., • Cable Heat Release, Ignition and Spread in Tray Installations During Fire (CHRISTIFIRE) Phase 2: Vertical Shafts and Corridors, NUREG/CR-7010, Vol. 2, U.S.NRC, July 2012, McGrattan K., Lock L., Marsh N., Nyden M., Bareham S., Price M., • Coutin M., PlumecocqW., Melis S., Audouin L. Energy balance in a confined fire compartment to assess the heat release rate of an electrical cabinet fire. Fire Safety Journal, 52:34 – 45, 2012. • Dietmar Hosser and Volker Hohm. Application of a new model for the simulation of coupled heat transfer processes during fires to safety relevant objects in nuclear facilities. Fire Safety Journal, 62, Part B(0):144 – 160, 2013. Special Issue on PRISME – Fire Safety in Nuclear Facilities. Document reference

  22. F. Bonte and N. Noterman and B. Merci. Computer simulations to study interaction between burning rates and pressure variations in confined enclosure fires. Fire Safety Journal, 62, Part B(0):125 – 143, 2013. Special Issue on PRISME – Fire Safety in Nuclear Facilities. • Lee B. T. Heat release rate characteristics of some combustible fuel sources in nuclear power plants. Technical report, U.S. Department of Commerce, National Bureau of Standards, Gaithersburg, MD 20899, 1985. • Mangs J., Paananen J., Keski-Rahkonen O. Calorimetric fire experiments on electronic cabinets. Fire Safety Journal, 38:165 – 186, 2003. • Tewarson A. Characterization of the fire environments in central offices of the telecommunications industry. Fire and Materials, 27:131 – 149, 2003. Document reference

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