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  • 1.
    Eidissen Jensen, Ulla
    et al.
    NTNU Norwegian University of Science and Technology, Norway.
    Fjellgaard Mikalsen, Ragni
    RISE - Research Institutes of Sweden, Safety and Transport, Fire Research Norway. Western Norway University of Applied Sciences, Norway .
    Steen-Hansen, Anne
    RISE - Research Institutes of Sweden, Safety and Transport, Fire Research Norway.
    The effect of fire retardants on smouldering fires in loose fill wood fibre building insulation2017Conference paper (Other academic)
    Abstract [en]

    Building insulation products produced from renewable biomass is becoming increasingly common in buildings due to environmental lifecycle requirements. Biomass insulation products are combustible and can contribute to fires through flaming and smouldering combustion. Incidents have been reported where insufficient spacing between combustible insulation and heat-producing electrical appliances has led to smouldering and subsequent development of flaming fires. Insulation materials often contain fire retardants, though their performance with regard to smouldering fire is not well understood. [1, 2] This study investigates the temperature exposure needed to initiate self-sustaining smouldering fires in loose fill wood fibre building insulation, focusing on the effect of fire retardant content and fibre size. The study is a part of the EMRIS (Emerging Risks from Smoldering Fires) project. The test set-up is shown in Fig 1a [3]. The tested material was 100 grams, 34 kg/m3 spruce wood fibre loose-fill insulation with 4 and 9 % added ammonium polyphosphate fire retardant. Tests with short, fine fibres (Fig 1b) were compared to testst with long, thin fibres. The sample was heated from below until a given temperature was obtained 20 mm above the heater. Temperature and mass loss measurements as well as visual observations of the residue after test (Fig 1c) were used to characterize the onset of self-sustained smouldering. An iterative process was used, with 5 to 8 tests per product. It was found that a high level (9 %) of fire retardant gave an onset of smoldering at lower temperatures (225 °C) compared to a low level (4 %) of fire retardant (290 °C). The lower onset temperature indicates that the insulation with the highest fire retardant content is more prone to smouldering, which is contradictory to the expected performance of the fire retardant. For the same fire retardant content, the onset of self-sustained smouldering combustion was obtained at lower temperatures in insulation materials with smaller fiber sizes than in insulation with larger fiber size (225 vs 280 °C). This study is indicative, the absolute temperatures relate to the given test set-up. Further studies should include a range of fire retardant types and content, to obtain knowledge on their effect on smouldering fires.

  • 2.
    Eidissen Jensen, Ulla
    et al.
    NTNU Norwegian University of Science and Technology, Norway.
    Steen-Hansen, Anne
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Fire Research AS, Norge. Stord/Haugesund University College, Norway.
    Fjellgaard Mikalsen, Ragni
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Fire Research AS, Norge.
    Development of smouldering combustion in loose-fill wood fibre building insulation2016In: Book of Abstracts Nordic Fire & Safety Days 2016, 2016, p. 7-7Conference paper (Other academic)
  • 3.
    Fjellgaard Mikalsen, Ragni
    RISE - Research Institutes of Sweden, Safety and Transport, Fire Research Norway. Western Norway University of Applied Sciences, Norway; Otto von Guericke University Magdeburg, Germany.
    Fighting flameless fires: Initiating and extinguishing self-sustainedsmoldering fires in wood pellets2018Doctoral thesis, monograph (Other academic)
    Abstract [en]

    Smoldering fires represent domestic, environmental and industrial hazards. This flameless form of combustion is more easily initiated than flaming, and is also more persistent and difficult to extinguish. The growing demand for non-fossil fuels has increased the use of solid biofuels such as biomass. This represents a safety challenge, as biomass self-ignition can cause smoldering fires, flaming fires or explosions.

    Smoldering and extinguishment in granular biomass was studied experimentally. The set-up consisted of a cylindrical fuel container of steel with thermally insulated side walls. The container was closed at the bottom, open at the top and heated from below by a hot surface. Two types of wood pellets were used as fuel, with 0.75-1.5 kg samples.

    Logistic regression was used to determine the transition region between non-smoldering and self-sustained smoldering experiments, and to determine the influence of parameters. Duration of external heating was most important for initiation of smoldering. Sample height was also significant, while the type of wood pellet was near-significant and fuel container height was not.

    The susceptibility of smoldering to changes in air supply was studied. With a small gap at the bottom of the fuel bed, the increased air flow in the same direction as the initial smoldering front (forward air flow) caused a significantly more intense combustion compared to the normal set-up with opposed air flow.

    Heat extraction from the combustion was studied using a water-cooled copper pipe. Challenges with direct fuel-water contact (fuel swelling, water channeling and runoff) were thus avoided. Smoldering was extinguished in 7 of 15 cases where heat extraction was in the same range as the heat production from combustion. This is the first experimental proof-of-concept of cooling as an extinguishment method for smoldering fires.

    Marginal differences in heating and cooling separated smoldering from extinguished cases; the fuel bed was at a heating-cooling balance point. Lower cooling levels did not lead to extinguishment, but cooling caused more predictable smoldering, possibly delaying the most intense combustion. Also observed at the balance point were pulsating temperatures; a form of long-lived (hours), macroscopic synchronization not previously observed in smoldering fires.

    For practical applications, cooling could be feasible for prevention of temperature escalation from self-heating in industrial storage units. This study provides a first step towards improved fuel storage safety for biomass. 

  • 4.
    Fjellgaard Mikalsen, Ragni
    RISE - Research Institutes of Sweden, Safety and Transport, Fire Research Norway.
    Studie av synlighet til høytmonterte markeringsskilt i brannrøyk2015Report (Refereed)
  • 5.
    Fjellgaard Mikalsen, Ragni
    et al.
    RISE - Research Institutes of Sweden, Safety and Transport, Fire Research Norway.
    Glansberg, Karin
    RISE - Research Institutes of Sweden, Safety and Transport, Fire Research Norway.
    Daaland Wormdahl, Espen
    RISE - Research Institutes of Sweden, Safety and Transport, Fire Research Norway.
    Stolen, Reidar
    RISE - Research Institutes of Sweden, Safety and Transport, Fire Research Norway.
    Jet fires and cryogenic spills: How to document extreme industrial incidents2019In: Sixth Magdeburg Fire and Explosion Days (MBE2019) conference proceedings, , 2019Conference paper (Refereed)
    Abstract [en]

    In industrial plants, such as oil platforms, refineries or onboard vessels carrying fuel, a rupture event of a pipeline could have dramatic consequences, as was demonstrated both in the Piper Alpha and Deepwater Horizon accidents. If surfaces are exposed to extreme conditions, both extreme cold (cryogenic spills) and extreme heat (jet fires), this can affect exposed surfaces, and can cause a domino effect of severe events.

  • 6.
    Fjellgaard Mikalsen, Ragni
    et al.
    RISE - Research Institutes of Sweden, Safety and Transport, Fire Research Norway. Western Norway University of Applied Sciences, Norway; Otto von Guericke University Magdeburg, Germany.
    Hagen, Bjarne C.
    Western Norway University of Applied Sciences, Norway.
    Frette, Vidar
    Western Norway University of Applied Sciences, Norway.
    Synchronized smoldering combustion2018In: Europhysics letters, ISSN 0295-5075, E-ISSN 1286-4854, Vol. 121, no 5, p. 50002-p1-50002-p2Article in journal (Refereed)
    Abstract [en]

    Synchronized, pulsating temperatures are observed experimentally in smoldering fires.The entire sample volume (1.8 l) participates in the pulsations (pulse period 2–4 h). The synchronylasts up to 25 h and is followed by a spontaneous transition to either disordered combustion orself-extinguishment. The synchronization is obtained when the fuel bed is cooled to the brink ofextinguishment. Calculations for adiabatic conditions, including heat generation from combustion(nonlinear in temperature) and heat storage in sample (linear in temperature), predict divergingsample temperature. Experimentally, heat losses to surroundings (linear in temperature) preventtemperatures to increase without bounds and lead to pulsations.

  • 7.
    Fjellgaard Mikalsen, Ragni
    et al.
    RISE - Research Institutes of Sweden, Safety and Transport, Fire Research Norway. Western Norway University of Applied Sciences, Norway.
    Hagen, Bjarne Christian
    Western Norway University of Applied Sciences, Norway.
    Emerging Risks from Smoldering Fires: Results from the EMRIS project2018Conference paper (Other academic)
    Abstract [en]

    Smoldering fires represent a severe, but often overlooked danger to society. Smoldering causes major economic losses for industrial facilities with production, transport and storage of biomass and biofuels worldwide. The smoke from post-flaming residual burning on the forest floor and in peatlands represents a major contributor to greenhouse gas emissions. [1]To prevent initiation of smoldering, and facilitate safe, efficient and complete extinguishment, a better fundamental understanding of smoldering is key. This is the aim of the research project EMRIS (Emerging Risks from Smoldering Fires). The consortium consists of 6 research institutes and universities in 5 countries, coordinated by Western Norway University of Applied Sciences in Haugesund, Norway. EMRIS started in 2015 and is now in its final stage. We will here present some points of interest from the project.Materials in the study include wood pellets, other biopellets, cotton, waste (wood chips), coal, wood fiber insulation and various pyrolysis products. Both experimental and modeling work has been done.Experimental work in small-scale has studied the sensitivity of smoldering ignition to a range of parameters [2], the impact of changes in air flow on the combustion [3], the effect of fire retardant content and fiber size [4], the transition from smoldering to flaming fire [5,6], early detection of smoldering [7]and heat extraction from the fuel bed with successfulextinguishment [8,9]. In medium scale experiments, initiationand propagation of reaction fronts have been studied [10]. TheEMRIS team also studies how particulate matter fromsmoldering fires can affect large scale phenomena, such ascloud formations, climate and public health.A cellular automaton model has been found to give a realistic representation of smoldering spread [11]. The method is based on a network of cells that mimic processes taking place in the material, which is easier to program and requires less computing power than traditional tools.The EMRIS project therefore represents progress within many different aspects of fire safety science. A continuation of the project is very much of interest, we welcome interested parties to discuss with us.

  • 8.
    Fjellgaard Mikalsen, Ragni
    et al.
    RISE - Research Institutes of Sweden, Safety and Transport, Fire Research Norway. Western Norway University of Applied Sciences, Norway.
    Hagen, Bjarne Christian
    Western Norway University of Applied Sciences, Norway.
    Steen-Hansen, Anne
    RISE - Research Institutes of Sweden, Safety and Transport, Fire Research Norway.
    Frette, Vidar
    Western Norway University of Applied Sciences, Norway.
    Extinguishing smoldering fires in wood pellets through cooling2017Conference paper (Other academic)
    Abstract [en]

    Extinguishing smoldering fires is a severe challenge for fire brigades, and has proven to be difficult even on the lab scale. In this study, the influence of a closed water cooling loop located within the fuel bed was investigated experimentally. Increasing the cooling led to a system less prone to intense combustion at an early stage, and eventually to complete extinguishment of self-sustained smoldering fires. Extinguishment was obtained in half of the cases with maximum cooling. Extinguishment occurred soon after smoldering had been established, giving a significant reduction in fuel consumption compared to the self-sustained smoldering fires that continued to complete burn-out.

  • 9.
    Fjellgaard Mikalsen, Ragni
    et al.
    RISE - Research Institutes of Sweden, Safety and Transport, Fire Research Norway. Western Norway University of Applied Sciences, Norway.
    Hagen, Bjarne Christian
    Western Norway University of Applied Sciences, Norway.
    Steen-Hansen, Anne
    RISE - Research Institutes of Sweden, Safety and Transport, Fire Research Norway.
    Frette, Vidar
    Western Norway University of Applied Sciences, Norway.
    Smoldering combustion- from pulsations to extinguishment2017Conference paper (Other academic)
    Abstract [en]

    Smoldering is known as a slow, but unpredictable form of combustion. In this study we have looked at how smoldering is affected by water cooling of the fuel bed without direct contact between fuel and water flow. The study is a part of the EMRIS project, and its findings have possible implications for preventing and suppressing fires in industrial storage units.

  • 10.
    Fjellgaard Mikalsen, Ragni
    et al.
    RISE - Research Institutes of Sweden, Safety and Transport, Fire Research Norway. Western Norway University of Applied Science, Norway; Otto von Guericke University Magdeburg, Germany.
    Hagen, Bjarne Christian
    Western Norway University of Applied Science, Norway.
    Steen-Hansen, Anne
    RISE - Research Institutes of Sweden, Safety and Transport, Fire Research Norway.
    Krause, Ulrich
    Otto von Guericke University Magdeburg, Germany.
    Frette, Vidar
    Western Norway University of Applied Science, Norway.
    Extinguishing Smoldering Fires in Wood Pellets with Water Cooling: An Experimental Study2019In: Fire technology, ISSN 0015-2684, E-ISSN 1572-8099, Vol. 25, no 1, p. 257-284Article in journal (Refereed)
    Abstract [en]

    Smoldering fires in stored or transported solid biofuels are very difficult to extinguish. The current study has explored heat extraction from the combustion zone as a method for extinguishing such flameless fires. Heat extraction from the sample was made feasible using water flowing through a metal pipe located inside the sample. The fuel container was a steel cylinder with insulated side walls, open at the top and heated from below. Wood pellets (1.25 kg, 1.8 l) was used as fuel. Results from small-scale experiments provide proof-of-concept of cooling as a new extinguishing method for smoldering fires. During self-sustained smoldering with heat production in the range 0 W to 60 W, the heat loss to the cooling unit was in the range 5 W to 20 W. There were only marginal differences between non-extinguished and extinguished cases. Up-scaling is discussed, cooling could be feasible for preventing smoldering fires in silos.

  • 11.
    Fjellgaard Mikalsen, Ragni
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Fire Research AS, Norge.
    Haraldseid, Ingunn
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Fire Research AS, Norge.
    Villacorta, Edmundo
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Fire Research AS, Norge.
    Hagen, Bjarne C.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Fire Research AS, Norge.
    Steen-Hansen, Anne
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Fire Research AS, Norge.
    Frette, Vidar
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Fire Research AS, Norge.
    Emerging Risks from Smoldering Fires2015Conference paper (Other academic)
  • 12.
    Fjellgaard Mikalsen, Ragni
    et al.
    RISE - Research Institutes of Sweden, Safety and Transport, Fire Research Norway.
    Sæter Bøe, Andreas
    RISE - Research Institutes of Sweden, Safety and Transport, Fire Research Norway.
    Glansberg, Karin
    RISE - Research Institutes of Sweden, Safety and Transport, Fire Research Norway.
    Sesseng, Christian
    RISE - Research Institutes of Sweden, Safety and Transport, Fire Research Norway.
    Storesund, Karolina
    RISE - Research Institutes of Sweden, Safety and Transport, Fire Research Norway.
    Stolen, Reidar
    RISE - Research Institutes of Sweden, Safety and Transport, Fire Research Norway.
    Brandt, Are W.
    RISE - Research Institutes of Sweden, Safety and Transport, Fire Research Norway.
    Energieffektive bygg og brannsikkerhet2019Report (Other academic)
  • 13.
    Reitan, Nina Kristine
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Fire Research AS, Norge.
    Fjellgaard Mikalsen, Ragni
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Fire Research AS, Norge.
    Sikker brensellagring i Norge2015In: Brandposten, no 52, p. 24-25Article in journal (Other academic)
  • 14.
    Reitan, Nina Kristine
    et al.
    RISE - Research Institutes of Sweden, Safety and Transport, Fire Research Norway.
    Friquin, Kathinka
    SINTEF, Norway.
    Fjellgaard Mikalsen, Ragni
    RISE - Research Institutes of Sweden, Safety and Transport, Fire Research Norway.
    Brannsikkerhet ved bruk av krysslaminert massivtre i bygninger – en litteraturstudie2019Report (Other academic)
    Abstract [en]

    © RISE Research Institutes of SwedenAbstractFire safety in cross laminated timber buildings; a reviewKey words: Cross laminated timber; CLT; fire safety; exposed CLT; auto-extinction; charring; delamination; detailingThis literature study presents recent research on fire safety in cross laminated timber (CLT) buildings. Results from large fire experiments and other studies in the period 2010 - 2018 are summarized, with focus on the following research questions:• How do constructions consisting of protected or exposed CLT contribute to the fire development in a room?• How can contribution to the fire development from detailing of CLT be avoided?There is an increasing desire to use wooden structures in tall buildings, as a substitute for more traditional construction materials. However, the use of combustible construc-tions in buildings in Norwegian Fire Class 3 (usually five floors or more) is not pre-accepted in the guideline to Regulations on technical requirements for construction works (TEK17), and fire safety must therefore be documented by analysis in such structures. When designing tall and complex timber buildings, it must be taken into account that a fire involving a timber construction may have more severe consequences than in buildings with constructions of steel or concrete, if the fire design of the construction and detail solutions is insufficient. Several studies show that fire exposed CLT, or CLT with insufficient protection, can cause a fire to develop faster, be more intense and last longer than a fire where the only fuel is the furniture and fixtures in the fire room. It is shown that the amount of fire exposed timber in a room may have impact on the extent and duration of a fire, but the knowledge has not yet been sufficient enough to be used in fire modeling, design and analysis.Research on charring rates, delamination and auto-extinction, all of which are factors that can have major impact on fire development and the fire resistance of the construction, takes place in Europe, Australia and North America. Although extensive research has been carried out, it is based on few large fire experiments, and the literature is still pointing to several knowledge gaps. However, the research projects have increased the knowledge of fire in timber buildings, and have contributed to the design of detail solutions, guidelines and development of models for function-based design. Revision of EN 1995-1-2 is under preparation and expected to apply from 2022. A knowledge base for the audit can be found in the network COST Action FP1404 Fire Safety Use of Bio-Based Building Products (COST FP1404) Working Group 2 (WG2). They have published several guidelines relevant for the fire design of CLT, including e.g. calculation methods for the prediction of charring rates and depths, determination of reduced CLT cross-section, design of CLT detailing and a suggested test method for evaluating adhesive performance.Based on the literature review, the following conclusions and recommendations are given for CLT constructions:• The design phase must sufficiently consider protection of the construction and con-tribution of the construction to the fire energy, and to a greater extent include the assessment of detailing and ventilation conditions. It should be considered whether analytic fire engineering design also should be required for buildings in the Norwegian Fire Classes 1 and 2 where more than one CLT wall is exposed.• By protecting all CLT surfaces of the structure with cladding, the construction may retain the stability and the load bearing capacity during the required time of fire resistance.• In buildings with only one exposed CLT wall in each fire cell, it may also be appropriate to use solutions that satisfy the pre-accepted performances, but one must consider whether a somewhat longer and more intense heat radiation and flame exposure on the facade outside window openings will require measures beyond the pre-accepted performances given in the guideline to TEK17.• Rooms where two or more CLT walls in addition to the ceiling are exposed, are configurations that should be avoided.• The risk of delamination can be reduced by using heat-resistant glue.• There is generally a need for relevant documentation for fire-resistant solutions for joints between CLT walls and floors and service penetrations in CLT constructions.• Test methods for testing of joints and penetrations in CLT constructions should be standardized. For example, there exists no standardized test for corner joints. Tests of penetration seals for CLT constructions are scarce, although they can be tested according to EN 1366-3. However, CLT is not a standard supporting construction according to EN 1366-3, and this must be taken into consideration when the test results are evaluated. Joints in glulam constructions should also be tested because they are often used in conjunction with CLT elements.

  • 15.
    Steen-Hansen, Anne
    et al.
    RISE - Research Institutes of Sweden, Safety and Transport, Fire Research Norway.
    Bøe, Andreas G.
    RISE - Research Institutes of Sweden, Safety and Transport, Fire Research Norway.
    Hox, Kristian
    RISE - Research Institutes of Sweden, Safety and Transport, Fire Research Norway.
    Fjellgaard Mikalsen, Ragni
    RISE - Research Institutes of Sweden, Safety and Transport, Fire Research Norway.
    Stensaas, Jan P.
    RISE - Research Institutes of Sweden, Safety and Transport, Fire Research Norway.
    Storesund, Karolina
    Hva kan vi lære av brannen i Lærdal i januar 2014?: Vurdering av brannspredningen2014Report (Refereed)
  • 16.
    Steen-Hansen, Anne
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Fire Research AS, Norge.
    Bøe, Andreas Gagnat
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Fire Research AS, Norge.
    Hox, Kristian
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Fire Research AS, Norge.
    Fjellgaard Mikalsen, Ragni
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Fire Research AS, Norge.
    Stensaas, Jan P.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Fire Research AS, Norge.
    Storesund, Karolina
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Fire Research AS, Norge.
    Evaluation of Fire Spread in the large Lærdal Fire, January 20142015In: Conference proceedings from Fire and Materials 2015, 2015Conference paper (Other academic)
  • 17.
    Steen-Hansen, Anne
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Fire Research.
    Fjellgaard Mikalsen, Ragni
    Hansen, Per Arne
    Wighus, Ragnar
    Hva tåler en brannvegg?2015In: Brandposten, no 52, p. 34-35Article in journal (Other academic)
  • 18.
    Steen-Hansen, Anne
    et al.
    RISE - Research Institutes of Sweden, Safety and Transport, Fire Research Norway.
    Fjellgaard Mikalsen, Ragni
    RISE - Research Institutes of Sweden, Safety and Transport, Fire Research Norway. Stord/Haugesund University College, Norway.
    Jensen, Ulla Eidissen
    NTNU Norwegian University of Science and Technology, Norway.
    Smouldering Combustion inLoose-Fill Wood Fibre Thermal Insulation: An Experimental Study2018In: Fire technology, ISSN 0015-2684, E-ISSN 1572-8099, Vol. 54, no 6, p. 1585-1608Article in journal (Refereed)
    Abstract [en]

    A bench-scale experimental setup has been used to study the conditions necessary

    for smouldering ignition in four types of loose-fill wood fibre thermal insulation, and

    to study the development of the smouldering process. The products varied with regard to

    wood species, grain size and fire retardant chemical additives. The test material was

    placed in an insulated open top container and heated from below. Temperatures within

    the sample and mass loss were measured during the tests. Both the fibre size and the level

    of added fire retardant seem to influence the smouldering ignition. Two different types of

    smouldering were identified in this study. Materials undergoing smouldering Type 1

    obtained maximum temperatures in the range 380C to 440C and a total mass loss of

    40 wt% to 50 wt%. Materials undergoing smouldering Type 2 obtained maximum temperatures

    in the range 660C to 700C and a total mass loss of 80 wt% to 90 wt%. This

    implies that Type 2 smouldering involves secondary char oxidation, which represents a

    risk for transition to flaming combustion and thereby a considerable fire hazard. This has

    been an exploratory project and the results must therefore be considered as indicative.

    The findings may, however, have implications for fire safety in the practical use of loosefill

    wood fibre insulation in buildings, and further experimental studies should be performed

    with this in mind to obtain more knowledge about the topic.

  • 19.
    Steen-Hansen, Anne
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Fire Research AS, Norge.
    Storesund, Karolina
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Fire Research AS, Norge.
    Fjellgaard Mikalsen, Ragni
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Fire Research AS, Norge.
    Stensaas, Jan P.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Fire Research AS, Norge.
    Bøe, Andreas Gagnat
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Fire Research AS, Norge.
    Hox, Kristian
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Fire Research AS, Norge.
    The Large Fire in Lærdal, January 2014. How did the Fire Spread and what Restricted the Fire Damage?2015In: Natural Disasters and Societal Safety / [ed] R.H. Gabrielsen & S. Lacasse, Oslo: Novus Forlag, 2015, p. 99-112Chapter in book (Other academic)
  • 20.
    Stolen, Reidar
    et al.
    RISE - Research Institutes of Sweden, Safety and Transport, Fire Research Norway.
    Fjellgaard Mikalsen, Ragni
    RISE - Research Institutes of Sweden, Safety and Transport, Fire Research Norway.
    Heat flux in jet fires: New method for measuring the heat flux levels of jet fires2018Conference paper (Other academic)
    Abstract [en]

    Jet fires are ignited leakages of pressurized liquid or gaseous fuel. In jet fire testing for the offshore industry, heat flux is the defining factor for the accidental loads. NORSOK S001 [1] defines two different heat flux levels of 250 kW/m2 and 350 kW/m2 depending on the leak rate of hydrocarbons. These heat flux levels are used in risk analysis and define what type of fire load bearing structures and critical equipment need to be able to resist in a given area. Examples of such ratings can be “250 kW/m2 jet fire for 60 minutes”, “350 kW/m2 jet fire for 15 minutes” or any other combination based on calculations in the risk assessment. Combined with critical temperatures this defines the performance criteria for the passive fire protection. Each configuration of the passive fire protection needs to be tested and verified. Manufacturers of passive fire protection request fire tests to document their performance against jet fires with these various heat flux levels. The challenge is that the standard for testing passive fire protection against jet fires [2] does not define any heat flux level or any method to define or measure it. We have developed a method for defining and measuring the heat flux levels in jet fires. This method can be used when faced with the challenge of testing passive fire protection against specific levels of heat flux. The method includes a custom test rig that allows jet fire testing with different heat flux levels. A large number of tests have been performed to verify the reproducibility and repeatability of the method. Heat flux is defined as the flow of energy through a surface. The heat flux from a fire to an engulfed surface of an object is dependent on both the engulfing flame and the properties of the surface. The properties of the surface may change during the exposure to the flame as it heats up and changes its surface properties. At some point the object inside the flame will reach a thermal equilibrium with the flame where the net flow of energy into the object is balanced by the energy emitted from the object. The heat flux for an object can be calculated as incident heat flux, emitted heat flux or net heat flux. A definition of heat flux needs to include parameters of the receiving object. These variations give a lot of degrees of freedom when calculating heat flux in a fire. Special water cooled gauges are designed to measure heat flux to a cooled surface, but these have proved to be very unreliable when placed inside a large fire. A more robust and easily defined method is to measure the equilibrium temperature inside an object placed inside the flame. This is the principle used in plate thermocouples used in fire resistance furnace testing [3]. In our experience, these plate thermocouples are often damaged during high heat flux jet fire tests. This raises questions to how long into the tests such measurements are reliable. Several other types of objects have been tested and the most convenient and reliable type was found to be simply a small 8 mm steel tube that is sealed in the end and has a thermocouple inside. One key difference between this small tube thermocouple and the plate thermocouple is that the plate thermocouple is directional and the tube is omnidirectional. Current works and tests will optimize the measuring objects in order to get the most relevant equilibrium temperature while still maintaining the robustness of the sensor during the test. The suggested heat flux calculation is to follow the Stefan-Boltzmann relation of temperature and heat flux. For a black body this gives 350 kW/m2 for 1303 °C and 250 kW/m2 for 1176 °C. A lower emissivity may be defined for the surface of the sensing object giving higher temperatures for the same flux levels. This method gives a simple, robust and reproducible correlation between heat flux levels and temperatures that can be measured during jet fire tests. The method does not differ between the varying convective and radiative heat transfer in the flame, but it is a representative measurement for the temperature that an object would reach when placed inside the flame.

  • 21.
    Stolen, Reidar
    et al.
    RISE - Research Institutes of Sweden, Safety and Transport, Fire Research Norway.
    Fjellgaard Mikalsen, Ragni
    RISE - Research Institutes of Sweden, Safety and Transport, Fire Research Norway.
    Glansberg, Karin
    RISE - Research Institutes of Sweden, Safety and Transport, Fire Research Norway.
    Daaland Wormdahl, Espen
    RISE - Research Institutes of Sweden, Safety and Transport, Fire Research Norway.
    Heat flux in jet fires : Unified method for measuring the heat flux levels of jet fires2018In: Nordic Fire and Safety Days (NFSD2018) Conference proceedings (with peer-review),, 2018Conference paper (Refereed)
    Abstract [en]

    Passive fire protection materials are used to protect critical structures against the heat from fires. In process plants with pressurized combustible substances there may be a risk of jet fires. Through risk analysis the severity of these jet fires is determined and these result in fire resistance requirements with different heat flux levels for different segments. The relevant test standard for fire resistance against jet fires does not include any measurements or definitions of the heat flux in the test flame which the tested object is exposed to. This paper presents methods for reaching different heat flux levels and how to measure them in a jet fire with limited deviations from the established jet fire test standard.

  • 22.
    Stolen, Reidar
    et al.
    RISE - Research Institutes of Sweden, Safety and Transport, Fire Research Norway.
    Fjellgaard Mikalsen, Ragni
    RISE - Research Institutes of Sweden, Safety and Transport, Fire Research Norway.
    Stensaas, Reidar
    RISE - Research Institutes of Sweden, Safety and Transport, Fire Research Norway.
    Solcelleteknologi og brannsikkerhet2018Report (Other academic)
    Abstract [en]

    The use of photovoltaic (PV) technology in Norway is increasing. In this study, fire safety challenges of PV technology are studied. Fire ignition, fire spread and fire extinguishing are investigated. The study forms a knowledge base for safeguarding fire safety during assembly, operation and during firefighting efforts, and to form unified and clear regulations. The results show:

    Fire ignition: PV installations contain many electric connections which can be potential ignition sources, as well as a small volume of combustible materials. These provide everything needed to initiate a fire. It is important that all connections in a PV installation are robust and can withstand the stress they are exposed to throughout their lifetime, without causing malfunction that could cause a fire.

    Fire spread: For building attached photovoltaics, there are cavities between the module and the building. If there is a fire in this cavity, the produced heat could be trapped, which could lead to a more rapid and extensive fire spread than if the building surface were uncovered. In large scale tests with PV modules mounted on a roof covering, the fire spread under the whole area covered with modules, but stopped when approaching the edge. This demonstrates the importance of sectioning when mounting PV installations, to avoid fire spread to the whole roof. An option is to use materials with limited combustibility as roof covering below the PV module, to withstand the increased heat exposure from the PV modules. The cavity between module and building could potentially also alter the air flow along the building, which in turn could affect the fire spread.

    Firefighting: Firefighters need information on whether there is a PV installation in the building, and where there are electrical components. During firefighting efforts, the fire service must consider the danger of direct contact, and danger of arcs and other faults that could lead to new ignition points. Fresh water can be used as an extinguishing agent. This must be applied from at least 1 meter distance with spread beam and at least 5 meters distance with a focused beam. PV modules can complicate fire extinguishing as they represent a physical barrier between the fire fighter and the area to extinguish, and by creating areas which should be avoided due to danger of components with voltage. When these points are considered, building attached photovoltaics should not be a problem.

    Further work: For building attached photovoltaics, there is little research on vertical mounting (on facades), and on how changed fire dynamics could affect fire spread and extinguishing. Also, today there is an increasing use of building integrated photovoltaics, which could potentially give many new challenges for fire safety and for regulations, as these are a part of the building and at the same time electrical components. German statistics indicate that there is an increased fire risk for these types of installations, compared to building attached photovoltaics, making this an important focus area for further work.

  • 23.
    Storesund, Karolina
    RISE - Research Institutes of Sweden, Safety and Transport, Fire Research Norway.
    Ishol, Herbjörg M.
    RISE - Research Institutes of Sweden, Safety and Transport, Fire Research Norway.
    Rømning i brann: funksjonen til ulike visuelle ledesystemer2014Report (Refereed)
  • 24.
    Storesund, Karolina
    et al.
    RISE - Research Institutes of Sweden, Safety and Transport, Fire Research Norway.
    Fjellgaard Mikalsen, Ragni
    RISE - Research Institutes of Sweden, Safety and Transport, Fire Research Norway.
    Evaluating particle and gas transmission through firefighters’ clothing2019In: Interflam 2019: Conference Proceedings, 2019Conference paper (Refereed)
    Abstract [en]

    The goal of this project has been to establish new knowledge and methods for testing the penetration of hazardous soot and smoke particles into fire clothing. The aim has been to provide the basis for the development of new fire-fighter clothing with better protection against particle penetration. In cooperation with fire services, authorities and protection clothing producers, needs, requirements and recommendations have been investigated. For the documentation and relevant classification of protective clothing, test set-ups in small and larger scale have been developed. The aim has been to be able to achieve representative and repeatable fire- and smoke exposure for accurate measurement of the particle penetration into clothing and trough clothing layers for screening materials and design solutions. With regard to the performance of the clothing, the small-scale tests give indications of the textiles’ ability to block gases and particles from penetrating into the clothing. The large-scale tests give indications to how the design of the clothing as a whole is able to prevent intrusion of gases and particles.

  • 25.
    Valdés, Virginia
    et al.
    NTNU Norwegian University of Science and Technology, Norway.
    Fjellgaard Mikalsen, Ragni
    RISE - Research Institutes of Sweden, Safety and Transport, Fire Research Norway. Stord/Haugesund University College, Norway.
    Steen-Hansen, Anne
    RISE - Research Institutes of Sweden, Safety and Transport, Fire Research Norway.
    Smouldering fires in wood pellets: the effect of varying the airflow2017Conference paper (Other academic)
    Abstract [en]

    Smouldering is a flameless form of combustion, deriving its heat from heterogeneous reactions occurring on the surface of the fuel when heated in an oxidizer environment. Smouldering is of interest both as a fundamental combustion problem and as a practical fire hazard, for instance in industrial storage units [1]. Many materials can sustain a smouldering reaction, among them wood pellets, which are becoming more widely used as an alternative to oil -fired central heating in residential and industrial buildings. Smouldering fires are difficult to detect, becoming a hazard that must not be underestimated [2]. The influence of varying the airflow, using two different configurations of smouldering combustion was studied: reverse and forward propagation. These are defined according to the direction in which the smouldering reaction front propagates relative to the oxidizer flow. In reverse smouldering, the reaction front propagates in the opposite direction to the oxidizer flow. In forward smouldering the front propagates in the same direction as the oxidizer flow: convective transport is in the direction of the original fuel ahead, preheating it before the smoulder zone is reached.

1 - 25 of 25
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