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  • 1.
    Hansen, Rickard
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, Framtidens energi.
    Analysis of methodologies for calculating the heat release rates of mining vehicle fires in underground mines2015Ingår i: Fire Safety Journal, ISSN 0379-7112, Vol. 71, s. 194-216Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Four different methodologies for calculating the ignition of different components on a mining vehicle in a mine drift were analysed. The results were compared with two full-scale fire experiments on mining vehicles. The four different methods are based on physical relations for fire spread between combustible components of the mining vehicles. The first two methods use a critical heat flux as ignition criterion while the other two methods use an ignition temperature. A sensitivity analysis was performed and the most influencing parameter of the methods was further analyzed. The calculated results were compared with the measured results from the experiments. The two methodologies applying an ignition temperature criterion were ruled out at as the surface temperatures of all fuel components never achieved the corresponding ignition temperatures. For the two methods applying a critical heat flux criterion it was found that the expression not including a flame radiation term was not suitable as it was found that the flame radiation played an important part with respect to spread mechanisms. The expression containing a flame radiation term was found to come very close to the observed ignition times, except in the case of the left, rear tyre of the drilling rig where it predicted a much higher ignition time than the one observed. The difference is unclear and would have to be investigated further. It was also found that the surface heat losses had none effect on the output results and could therefore be neglected in the calculations. In the case of the wheel loader the calculated heat release rate curves did not match the measured curve as well as in the case of the drilling rig. The difficulty in this case consists of accurately predicting the mechanical failure of a component - in this case a suction hose - that would initiate the very significant hydraulic oil pool fire.

  • 2.
    Hansen, Rickard
    Mälardalens högskola, Akademin för hållbar samhälls- och teknikutveckling.
    Design fires in underground hard rock mines2011Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    During several decades considerable research activities have been conducted with respect to fires in coal mines, but the research activities with respect to hard rock mines have been limited. As the hard rock mines are getting more complex the need for deeper understanding of fires in underground hard rock mines are getting more in demand. The more urgent demands are the need for more specific heat release rate curves as design fires, applicable fire experiments and any method that would allow for the calculation of the total heat release rate curve of an object. This thesis presents a number of examples on design fire curves applicable to underground hard rock mines; it also presents the results of model scale fire experiments and methods for calculating the total heat release rate of several objects at uniform as well as non-uniform conditions. Tests were carried out in a model scale tunnel using wooden pallets as fire load. The parameters tested were the distance between piles of pallets and longitudinal ventilation rate. It was found that an increasing ventilation rate also increases the peak heat release rate. When studying the curves of heat release rates it was found that when the distance between the ignited pile and the second pile increased to a certain level the delayed ignition of the second pile will result in that the peak heat release rate of the adjacent piles will not occur simultaneously. The ignition data indicated that the ignition time of adjacent piles decreased as the longitudinal ventilation increased.  A method using a critical heat flux as ignition criterion exhibited very good agreement with the corresponding experiments for both uniform as well as non-uniform conditions. The methods using the ignition temperature as ignition criterion did not agree very well with any of the corresponding experiments.

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  • 3.
    Hansen, Rickard
    Mälardalens högskola, Akademin för hållbar samhälls- och teknikutveckling.
    Design fires in underground mines2010Rapport (Övrigt vetenskapligt)
    Abstract [en]

    This report deals with the issue on design fires in underground mines.

    The main purposes of the report are:

    -          Describe different approaches to describe design fires.

    -          Develop suitable design fires for different systems, mines, warehouses, workshops etc.

    -          Discuss the position of the design fires with respect to adjacent installations, egress, interruptions in the production etc.

    -          Discuss the influence of ventilation on the fire growth and its influence when working out the design fires.

    -          Discuss the influence of fire fighting on the choice of design fires.

    The following conclusions were made based upon the findings of the report:

    The five selected and presented design fire curves of the report:

    -          Pool fire in the main ramp (involving a diesel tank).

    -          Vehicle fire (heavy vehicle) in a parking drift which is protected by a sprinkler system.

    -          Vehicle fire (loader/drilling rig) in the production area.

    -          Cable fire at the visitor museum, with no automatic fire alarm at the site of the fire.

    -          Bus fire at the visitor museum, with no automatic fire alarm at the site of the fire.

    The design fire curves represent various aspects and variables connected to an underground mine, such as active fire protection, ventilation, sensitive surroundings etc.

    In future work the main effort should be aimed at developing other representative design fires for underground mines than the suggested design fire scenarios in this report, this would serve as a powerful tool during the design process when working on an underground mine.

    In future work the three scenarios described in the report involving vehicles, design fire curves obtained by using physical models should be used. This means summing up the individual combustible components taking into consideration when ignition will occur.

    The five presented design fire curves should be included in a continued study where for example the smoke spread is calculated and simulated using fire modelling software, presenting the effects on the surroundings that the selected design fires will have.

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  • 4.
    Hansen, Rickard
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik.
    Estimating the amount of water required to extinguish wildfires under different conditions and in various fuel types2012Ingår i: International journal of wildland fire, ISSN 1049-8001, E-ISSN 1448-5516, Vol. 21, nr 5, s. 525-536Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In wildland fires where water is used as the primary extinguishing agent, one of the issues of wildfire suppression is estimating how much water is required to extinguish a certain section of the fire. In order to use easily distinguished and available indicators, the flame length and the area of the active combustion zone were chosen as suitable for the modelling of extinguishing requirements. Using Byram's and Thomas' equations, the heat release rate per unit length of fire front was calculated for low-intensity surface fires, fires with higher wind conditions, fires in steep terrain and high-intensity crown fires. Based on the heat release rate per unit length of fire front, the critical water flow rate was calculated for the various cases. Further, the required amount of water for a specific active combustion zone area was calculated for various fuel models. Finally, the results for low-intensity surface fires were validated against fire experiments. The calculated volumes of water can be used both during the preparatory planning for incidents as well as during firefighting operations.

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  • 5.
    Hansen, Rickard
    Mälardalens högskola, Akademin för hållbar samhälls- och teknikutveckling.
    Final recommendations - GRUVAN project2010Rapport (Övrigt vetenskapligt)
    Abstract [en]

    This report comprises the recommendations given in the earlier parts of the project.

    Based upon the findings, conclusions and recommendations of the individual parts of the GRUVAN project, the following recommendations were picked out as the most significant:

    -          Full scale fire experiments with respect to vehicle fires should be performed, resulting in heat release rate curves.

    -          Further studies and experiments should take place that vary additional parameters besides the distance between the individual fuel objects.

    -          The heat release rate curves of design fires involving all common vehicles should possibly be reconstructed using the potential theoretical methodology.

    -          The results from the full scale fire experiments should be compared with the corresponding results from one- or two-dimensional calculation models as well as three-dimensional CFD calculation models.

    -          The use of a CFD model together with a ventilation network simulation program should be further investigated. The results should be compared with corresponding fire experiments.

    -          Further studies of the applied mine ventilation network simulation program should be performed.

    -          Non-flammable hydraulic fluids are strongly recommended for use in underground mines.

    -          The lack of fire barriers should be investigated further and alternative methods should be looked into.

    -          During the work in the project it has been shown that the fire behaviour in loader cabs can be very rapid and have a large impact. Thus it is recommended that automatic extinguishing systems are installed in loader cabs that are manned.

    -          The research has shown that the time space for smoke spread during a large fire in an underground mine is larger than the minimum demand on the air supply in refuge chambers. Thus it is recommended that the minimum demand is revised and increased.

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  • 6.
    Hansen, Rickard
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik.
    Investigation on fire causes and fire behaviour: Vehicle fires in underground mines in Sweden 1988–20102013Rapport (Övrigt vetenskapligt)
    Abstract [en]

    This report is part of the research project “Fire spread and heat release rate of underground mining and tunnelling vehicles – BARBARA”, conducted by a research group at MälardalenUniversity.

    The project’s aim is to improve fire safety in mines and tunnels during construction in order to obtain a safer working environment for the people working for the mining companies as well as the tunnelling companies in Sweden or for visitors in mines open to the public.

    This report deals with the second step in the project: the investigation regarding fire causes and fire behaviour of vehicle fires in underground mines based upon material from GRAMKO (the work environment committee of the mine and mineral industry in Sweden).

    The main purposes of the investigation are:

    • To investigate and present fire causes, types of vehicles involved in fires, fire spread and fire behaviour of vehicle fires in underground mines.
    • To give recommendations on the continued work with the full-scale fire tests regarding the initial fire and its position.

    The conclusions were that:

    • With respect to vehicle fires involving only the start object, a typical fire occurs in a loader or a drilling rig and is due to electrical fault – for example short-circuit of cables – in the engine compartment, resulting in a slow and limited fire spread.
    • Regarding vehicle fires limited to the start object and an adjacent object is that it usually occurs in a loader and is due to electrical causes, resulting in a slow and limited fire spread. Typically, electrical cables would play an important role when it comes to the fire spread to adjacent objects.
    • Vehicle fires involving the entire vehicle usually occur in a service vehicle or a loader and are typically caused by diesel being sprayed – for example due to a pipe/hose coming loose – on the engine, resulting in a rapid fire spread.
    • In future full-scale fire experiments involving a diesel loader and a drilling rig, the vehicles will have to be ignited using a diesel fire – for example a pool fire under­neath or inside the engine compartment – that is shielded and positioned close to larger amounts of combustibles – such as tires or hydraulic hoses – and continuously distributed fuels – such as electrical cables – in order to achieve a rapid fire growth and fire spread that eventually engulf the entire vehicle. 
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  • 7.
    Hansen, Rickard
    Mälardalens högskola, Akademin för hållbar samhälls- och teknikutveckling.
    Literature survey – fire and smoke spread in underground mines2009Rapport (Övrigt vetenskapligt)
    Abstract [en]

    This report is part of the research project “Concept for fire and smoke spread prevention inmines”, conducted by a research group at Mälardalen University. The project is aimed at improving fire safety in mines in order to obtain a safer working environment for the people working for the mining companies in Sweden or for visitors in mines open to the public.This report deals with the first step in the project: the literature survey.

    The main purposes of the literature survey are:

    - To investigate and present what has been done in the non-coal underground mine firefield in the past.

    - To give recommendations on the continued work with regard to fire safety inunderground non-coal mines.

    A large amount of articles in scientific publications and material on internet were found duringthe literature survey. Most of the material was from USA, Canada, South Africa, Australia, Sweden, India, China, Russia and United Kingdom.

    The following conclusions were made based upon the findings of the literature survey:

    Starting with the statistical material, the most common fire cause in underground mines isflammable liquid sprayed onto hot surface, followed by electrical shorting/arcing and hot works.So based upon the statistics, a conclusion would thus be to focus on spray fires, fire caused byflammable liquid ignited by hot surface, vehicles fires (including rubber tires) and cable fires. Continuing on with the interesting locations in underground mines, mobile equipment workingareas would be first priority due to the high risk of fires in mobile equipment. Furthermore the types of mobile equipment to focus on should be: service vehicles, drilling rigsand loaders.

    There is at the moment no need for any extensive research with respect to the ignitability and flammability of pressurized hydraulic fluids, as an extensive work has already been conducted.Still the type of hydraulic fluid being used in the Swedish mines should be investigated and fire resistant hydraulic fluid should be recommended being used whenever possible.

    The results from the articles can be used when examining the equipment that is used containinghydraulic fluid (i.e. what potential ignition sources can be found on the equipment), what type ofhydraulic fluid being used and what actions that can be taken to minimize the risk of a spray fire.

    A major concern is the lack of documented fire experiments in vehicles/mobile equipment. This is essential knowledge when designing new mine sections and overlooking existing sections. Thus there is a great need for HRR curves, also due to for example the fact that a majority of the firesin underground mines involve vehicles/mobile equipment.

    Taking into account that conveyor belt fires are not a dominating fire cause in non-coal minesand the fact that a very intensive work has dealt with for example ignitability and flammability,HRR curves etc. The focus should not be on this type of design fire during the project.Nevertheless a relatively easy and effortless task would be to investigate and list the principalcauses of belt conveyor fires in underground non-coal mines.

    Another interesting issue would be to investigate the minimum ventilation velocity for beltsurface-to-roof distances much greater than 0.22 m, which is applicable for the LKAB mines.Research material so far has mainly dealt with cases where the surface-to-roof distances are equalto or less than 0.22 m.

    Taking into account the enormous volume of cables present in an underground mine and the factthat the statistics put cable fires high on the list, some efforts should be made with respect to thistype of fire.

    Generally there is a demand for investigation of the friction losses of fire gases in a mine drift (asnot all CFD models will be able to take this into account). Further work is needed within thisdiscipline.

    When performing full scale experiments in an underground mine, models and equationsdescribing the heat exchange between fire/fire gases and rock should be validated at the sametime. The articles Simplified method to calculate the heat transfer between mine air and mine rock /18/ andModelling of heat exchange between flowing air and tunnel walls /19/ contain methods for calculating theheat exchange that could be worth looking further into and validating during the future fire experiments.

    Regarding the movement of fire gases in a mine ventilation network, the earlier work will have tobe supplemented with fire experiments with more complicated and varying geometry (openingarea, inclination, aspect ratio), larger test area, reversing/increasing the ventilation, and larger,non-steady state fires are needed. Besides performing the fire experiments the results should alsobe examined against the results of corresponding CFD/ventilation network simulation program.A practical issue that would greatly affect the fire safety in production areas is the difficulty inpreventing smoke spreading from a fire affected production area, as no fire barriers are possible(the blasting taking place every day would destroy the fire barriers), other methods will have to belooked into.

    The use of a CFD model together with a ventilation network simulation program would be veryinteresting to investigate. The results should be compared with corresponding fire experiments.Ventilation network simulation programs could at the same time be validated for a non-coalmine.

    The work on CFD modelling in underground mines has so far been fragmentary; a moreextensive work is needed, where:

    - The geometry is varied (opening area, inclination, aspect ratio etc.) and made morecomplicated in the vicinity of the fire.

    - Non-steady state fires and larger fires.- Friction losses/obstacles.

    - Heat losses to surrounding rock.

    - Changes in ventilation (non-steady state ventilation).

    Besides the investigation of the above factors the investigation should also include theimplementation of CFD models and suggestions on improvements should be made.

    Conveyor belts, cables etc. are regulated with respect to their flammability but others are not. Inorder to get a good picture of the fire risk in Swedish underground an inventory and aninvestigation should be performed.

    The use of fire suppression systems and rapid fire detection systems should be considered formanned cabs in Swedish mines. The reason for this is the rapid fire behaviour of spray fires.

    A large part of the earlier mine safety research has been conducted with respect to detecting firesin mines and conveyor belts. No further work is identified at the moment.

    As organic material stored in abandoned, backfilled parts of mines could be applicable to touristmines, the risk of spontaneous combustion is a subject in these cases.

    During the search no material related to tourist mines was found.

    Finally, the three activities with the highest priority are:

    - Conducting fire experiments with respect to cab/vehicle fires, resulting in HRR curves.

    - Conducting an extensive work on CFD modelling (validating the results withcorresponding fire experiments), where:o The geometry is varied (opening area, inclination, aspect ratio etc.) and mademore complicated in the vicinity of the fire.o Non-steady state fires and larger fires.

    o Friction losses/obstacles.o Heat losses to surrounding rock.

    o Changes in ventilation (non-steady state ventilation).

    - Investigating the use of a CFD model together with a ventilation network simulationprogram. The results should be compared with corresponding fire experiments.

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  • 8.
    Hansen, Rickard
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik.
    Methodologies for calculating the overall heat release rateof a vehicle in an underground structure2012Ingår i: Proceedings from the fifth international symposium on tunnel safety and security", New York, USA, March 14-16, 2012 / [ed] Anders Lönnermark & Haukur Ingason, 2012Konferensbidrag (Refereegranskat)
    Abstract [en]

    Most common type of object involved in fires in underground structures such as underground minesare vehicles [1-3]. A major concern is the lack of documented fire experiments in vehicles/mobileequipment, which is especially the case for working vehicles such as loaders, drilling rigs etc. Theresulting heat release rate (HRR) curves are essential knowledge when designing new tunnel or minesections and overlooking existing sections, thus there is a great need for HRR curves.This paper encompasses the measurement of the HRR for two full-scale fire experiments with vehiclesrepresentative for underground structures and the reconstruction of the measured HRR by investigatingwhat methodology that fits the measured values best. The main purpose of the methodologies is toprovide HRR curves without having to perform full-scale fire tests of the vehicles, which would be ofconsiderable value.

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  • 9.
    Hansen, Rickard
    Mälardalens högskola, Akademin för hållbar samhälls- och teknikutveckling.
    Overview of fire and smoke spread in underground mines2010Ingår i: Proceedings from the fourth international symposium on tunnel safety and security, Frankfurt am Main, Germany, March 17-19, 2010 / [ed] Anders Lönnermark & Haukur Ingason, Borås: SP Fire Technology , 2010, s. 483-494Konferensbidrag (Övrigt vetenskapligt)
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  • 10.
    Hansen, Rickard
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik.
    Regression analysis of wildfire suppression2012Ingår i: Proceedings from the third international conference on modelling, monitoring and management of forest fires", New Forest, United Kingdom, May 22-24, 2012 / [ed] Brebbia C.A. & Perona G., 2012Konferensbidrag (Refereegranskat)
    Abstract [en]

    One of the most important aims of forest fire research is how to better controlforest fires. One way to attain this aim is to develop better decision tools forestimating how much water is required for extinguishing a fire with a specific setof conditions. There has in the past generally been little research conducted withrespect to water requirements when suppressing a wildfire. A number ofexperiments were conducted in the early ‘70s where a spray rig with a nozzlearrangement was used in order to apply water uniformly across a fuel bed. Twostudies regarding the required duration of water application related to fires inbuildings were conducted in the past. Both studies were based upon statisticaldata from fire brigades; the duration of water application was determined as afunction of the fire area. This paper encompasses an analysis of more than64,000 wildfires occurring in Sweden between 1996 and 2009. The valuescalculated from the obtained formulations with regression analysis were found tobe in good agreement in the following cases: The amount of water as a functionof the extinguishing time, the extinguishing time as a function of the fire area;and the fire area as a function of the flame height. It was observed that thederived equations from the analysis in the above cases could provide an accuratecomputation. These relationships could be of considerable use when developingdecision tools for wildfire suppression, optimizing the use of resources duringthe suppression activities.

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  • 11.
    Hansen, Rickard
    Mälardalens högskola, Akademin för hållbar samhälls- och teknikutveckling.
    Site Inventory of Operational Mines - fire an smoke spread in underground mines2010Rapport (Övrigt vetenskapligt)
    Abstract [en]

    This report deals with the second step in the project GRUVAN: the site inventory in operational mines.

    The main purposes of the inventory are:

    -          To get a clear picture of the risks in the different mines.

    -          To get a clear picture of the protective measures of each mine.

    -          Optimize the choice of design fires for each mine.

    The site inventories were conducted through actual visits to the two LKAB mines in Sweden and through e-mail correspondence with LKAB personnel responsible for the different sections and areas. During the inventories, predefined forms for each type of item were used in order to facilitate the work. The following items were examined:

    -          Combustible materials in general, for example large amounts of wood.

    -          Vehicles

    -          Cables

    -          Fire barriers

    -          Ventilation systems

    -          Extinguishing systems

     

    Besides the above items, earlier fires and fire incidents were also examined.

    As the two LKAB mines are tremendously large with a large amount of equipment etc, only the most common vehicles were listed and examined further. Also, only the sites with the largest amount of cables and other combustible materials were listed.

     

    The following conclusions were made based upon the findings of the inventory:

    -          With respect to earlier fires and fire incidents for the two LKAB mines, the most common causes and the causes to focus on are: electrical cause, flammable liquid or material on hot surface, hot works and equipment running hot.

    -          Both the production area and the infrastructure part should be regarded in the future studies as fires are almost identically frequent in both areas.

    -          When it comes to combustible material in general, the amount of combustibles seems to be more frequent in the Malmberget mine. In the Kiruna mine, the places with wood and conveyor belts seems to be interesting enough for further investigation. Even though self extinguishing conveyor belts means a limited fire in size, the amount of smoke emitted can be quite extensive. Also the storage of tyres at the contractor’s depots could be worthwhile investigating due to the sensitive surroundings.

    -          Regarding the Malmberget mine, the sites with wood combustibles, tyres and conveyor belts are all interesting for further investigation due to the large amount of combustibles and the surroundings.

    -          With respect to flammable liquids:

    - The tank stations in the Kiruna and the Malmberget mine should be looked          into with respect to potential pool fires.

    - The larger workshops and warehouses in the Kiruna mine and the Malmberget     mine should also be investigated with respect to pool fires.

    - The crusher levels and draw points in the two mines should be investigated          with respect to spray fires.

    - The diesel tanks in the main ramps and the production areas should be investigated with respect to pool fires.

    - The media drifts, distribution levels, shaft hoisting levels and pumping stations    should be investigated with respect to pool fires.

    -          With respect to fire barriers, as the main ramps of each mine does not contain any fire barriers the impact of a vehicle fire in the main ramp would be interesting to investigate. It would also be interesting to validate the ventilation strategy in the Malmberget mine regarding preventing smoke spread to adjacent compartments.

    -          With respect to vehicles, all the common heavy vehicles listed in this report would be worthwhile to try to reconstruct a possible fire scenario for each type of vehicle. The reason for this is to have better tools when working on possible scenarios of each mine.

    -          Regarding cables, all listed sites with a high load of electrical cables would be interesting to investigate. Even though the immediate surroundings are not sensitive, an extensive smoke spread would make a large impact on a large portion of the mine.

    -          When looking into the ventilation system of the Kiruna mine, both the mine production area and the infrastructure part should be investigated due to the differences in each system and their surroundings. Also, the difference in systems whether you are below or above level 775 should be considered. The function and impact of oversteering should also be included in the investigations.

    -          The impact of a ventiflex PVC-tube being burned up on the fire behaviour in a production area should be investigated. The different fire scenarios in a production area depending on the position of the fire with respect to the ventilation should also be investigated.

    -          One scenario should put the fire right at the end of the intake air tube, other scenarios should be at a certain length interval from the end of the intake air tube. The likelihood of the power cables to the intake and exhaust air fans being burned off should be looked into. The impact on the surroundings should also be investigated. The return air fan capacity should be examined with respect to fires, such as vehicle fires.

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  • 12.
    Hansen, Rickard
    Mälardalens högskola, Akademin för hållbar samhälls- och teknikutveckling.
    Smoke spread calculations for fires in underground mines2010Rapport (Övrigt vetenskapligt)
    Abstract [en]

    This report is part of the research project “Concept for fire and smoke spread prevention in mines”, conducted by a research group at Mälardalen University.The project is aimed at improving fire safety in mines in order to obtain a safer working environment for the people working for the mining companies in Sweden or for visitors in mines open to the public.This report deals with the issue on smoke spread calculations for fires in underground mines.The main purposes of the report are:- Using both one- or two-dimensional calculation models as well as three-dimensional CFD calculation models.- Positioning the design fires (a pool fire, a fire in a loader, a fire in a loader in a sprinklered drift, a cable fire and a bus fire) at various sites with respect to for example the ventilation system.- Investigating the complexities of the various models, their limitations and deficiencies etc.- Comparing the results from the calculation models with each other and with experimental data where applicable and available.The work in this report started with describing smoke spread in underground mines in general and then continuing with describing three types of calculation models used in this report. After that calculations and simulations were conducted – using the three models – for the five designated design fire scenarios and the results were presented for strategic sites with respect to egress safety and the intervention of the fire and rescue services. The results from the CFD simulations were thereafter validated with respect to flame temperature and grid size convergence. It is misleading to fully compare the outputs of the three calculation models with each other without considering the differences and limitations of the three models as they are based upon different assumptions that differ considerably. For example the hand calculation expressions and the mine ventilation network simulation program assume unidirectional flow in the drifts compared with FDS that account for multi directional flows in the drifts. Also the hand calculation expressions and the mine ventilation network simulation program both assume complete mixture of air and fire gases while FDS does not make that assumption. Visibility is not one of the output parameters of the mine ventilation network simulation program, thus limiting the available data for comparison. But one of the purposes of this report was to investigate the complexities, limitations and deficiencies of the involved models.The advantage of the one- and two-dimensional models is the fact that the computational requirements are considerably lower than compared with a CFD model. Also with Ventgraph it is possible to obtain fast and transient solutions even though the simulated system of mine drifts is vast and complex. The advantage of FDS is the fact that it will model the area closest to the fire most accurately of the three models, for example accounting for multi directional flows in the near area of the fire. The disadvantages of the models are for example that it is not possible to fully account for the highly variable heat release rate of for example a fire in a tyre or in a vehicle when using a mine ventilation network program, as the ramp up to the maximum heat release rate is assumed to be linear and that every fire in a branch is assumed to be constant after reaching the maximum heat release rate. This does not apply to heat release rate curves that are uniform in shape such as a pool fire; in this case the heat release rate values used will be practically the same in all three types of calculation models.Also the time periods of the simulations differ between the three models as the simulations in FDS will become impractically long as the time to simulate increases due to higher computational requirements. Thus only the first 10-20 minutes were simulated in FDS and so the chance of comparison in for example the case of the fire in the loader is strongly limited.When comparing the results of the three calculation models the following conclusions can be made:- The mine ventilation network simulation program generally shows higher temperatures at the measuring points compared with the outputs of the other two models. One probable reason for this is that the heat release rate could not be represented as adequately as for the other two models; in all cases the heat release rate levels were higher for the mine ventilation network simulation program.- Generally the hand calculations showed much lower visibility figures than the CFDmodel. One reason for this – besides the fact that we are dealing with two models withvastly different approaches - is most likely in the difference in the types of smokecharacteristic factors used in the two types of models.- The FDS simulations generally showed small changes in temperature when comparingwith the other two models. This could be attributed to the fact that the measuring pointsare positioned at fairly large distances from the fire and thus the fire gases will coolconsiderably. Also the maximum heat release rate of some of the fires was small - ~1MW – and thus the impact on the nearby environment will be limited.- The results of the hand calculations with respect to the visibility is a good approximationfor the design fires with fairly low maximum heat release rate as the stratification in thiscase will be almost nonexistent and thus the smoke spread can be assumed to be equal tothe ventilation velocity in a drift (one dimensional smoke spread).- With respect to the egress safety the visibility will be the critical factor. In the case of thepool fire (design fire) the visibility will start to decrease at an early stage of the fire bothaccording to the hand calculations and the FDS simulation. After approximately a fewminutes the visibility in a large section of the connecting main ramp will be affected dueto the open nature of the area. Thus the egress will have to take place at an early stage inorder to ensure safety. Regarding the fire in the loader, the fire in the parking drift andthe cable fire the hand calculations indicate a sharp decline in visibility after a fewminutes, but the facts that the FDS simulation showed no differences in visibility and thatthe heat release rate is relatively small in all three cases (<1 MW) would indicate that thevisibility would be affected but in a limited manner and thus the egress safety will not belargely affected during the first 10-20 minutes due to for example the large spaces in themine drifts. With respect to the bus fire the same conclusions are drawn as in the case ofthe pool fire except that the FDS simulation predicts a much slower smoke spread thanthe results from the hand calculations.- With respect to the intervention from the fire and rescue services the visibility will also bethe critical factor as for the egress safety. The loader fire in the sprinklered drift and thecable fire should generally not pose any large problem to the intervention of the fire andrescue service, as the maximum heat release is small and the smoke spread largely limited.But the pool fire, the loader fire and the bus fire will be problematic to the interventionof the fire and rescue service as the maximum heat release is large and the smoke spreadis extensive affecting a large area before the arrival of the fire and rescue service (>30minutes). Thus the fire and rescue service will have to start the intervention at a largedistance from the site of the fire and work its way towards the fire. This will take a longtime and will decrease the chance of rescuing any personnel left in the area.As no data from conducted full-scale fire experiments were found that were applicable to any ofthe five design fire scenarios, future work should deal with validating the results of the threemodels with experimental results from conducted full scale fire tests corresponding to any of thefive design fire scenarios. In this case more profound comparisons and conclusions can bedrawn. The work and reflections from this report can be used when working on the full-scale fireexperiment.Measuring points should be placed in the near vicinity to the fire as well as sites further awayfrom the fire (> 50 m), this in order to effectively investigate and compare the results of one- andtwo-dimensional models versus a three dimensional model.Also further and deeper studies of the applied mine ventilation network simulation programshould be performed, investigating for example the assumptions and calculation models behindthe specific software.

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  • 13.
    Hansen, Rickard
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, Framtidens energi.
    Statistical expressions on water based wildfire suppression in Sweden, 1996-20112015Ingår i: International Journal of Safety and Security Engineering, ISSN 2041-9031, E-ISSN 2041-904X, Vol. 5, nr 2, s. 124-141Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Little research has been conducted with respect to water requirements for wildfire suppression. An exploratory and robust regression analysis was conducted on statistical material extracted from a Swedish database, focusing on data related to the fire suppression. The variables included are the amount of water applied, application rate of water, extinguishing time, flame height, and the total fire area. The results of the analysis with potential relationships are described, discussed, and compared with results from earlier research. After initial outlier detection, a robust regression analysis was performed and relationships developed. It was found that the developed relationships could predict the dependent variable very well; this was especially the case with the extinguishing time as a function of the total fire area. The relationship with the lowest ability to predict the dependent variable was the application rate of water as a function of the total fire area. The large number of parameters and their included uncertainties could be an explanation to the increased inability to predict the dependent variable. When comparing the control times of earlier conducted building fire studies with the extinguishing times of developed relationships, it was found that the control times were much longer than the corresponding extinguishing times. The reason behind was most likely due to the difference in the fire area applied in the equations. The resulting relationships for the grass fuel type were found to have lower ability to predict the dependent variable. The reason behind this is unclear and needs to be investigated further.

  • 14.
    Hansen, Rickard
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, Framtidens energi.
    Study of heat release rates of mining vehicles in underground hard rock mines2015Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    A unique study on fire safety in hard rock underground mines with focus on heat release rates of mining vehicles is presented. A literature inventory was conducted with respect to fires in underground hard rock mines, which revealed that the most common fire cause in underground mines was flammable liquid sprayed onto hot surface and the most common fire object was a vehicle. A major concern was the lack of documented fire experiments in mining vehicles and heat release rate curves. It also revealed the limited research carried out on fire safety and fire development on vehicles found in hard rock underground mines.

    In order to fill the gap of knowledge lack on heat release rates, fire experiments were carried out on wood cribs and wooden pallets in a model-scale tunnel with longitudinal ventilation where the distance between the fuel items were kept constant as well as varied. Different ignition criteria were applied in the ensuing calculations. It was found that the critical heat flux criterion generally showed very good agreement with the corresponding results of performed fire experiments but tended to have too short ignition times when the distance between the fuel items was increased. The ignition temperature criterion generally performed poorly compared with the measured results, but it was found that the accuracy improved considerably as the distance between the fuel items and the amount of energy accumulated on the fuel surface was increased.

    As a final approach, two full-scale fire experiments were carried out in an operative underground mine using a wheel loader and a drilling rig respectively. The resulting heat release rates of the experiments were compared with calculated overall heat release rates applying the different ignition criteria. It was found that the critical heat flux criterion resulted in ignition times very close to the observed ignition times. The ignition temperature criterion resulted in surface temperatures that never achieved the corresponding ignition temperatures. Some difficulties were experienced when calculating the heat release rate curve of the wheel loader, as it was difficult to accurately predict the mechanical failure of a significant part initiating the highly significant fire in the hydraulic oil. Additional heat terms were added to the heat balance, where the added flame radiation term was found to have a large impact on the output results while the heat loss terms were found to have very little effect.

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  • 15.
    Hansen, Rickard
    et al.
    Mälardalens högskola, Akademin för hållbar samhälls- och teknikutveckling.
    Ingason, Haukur
    Mälardalens högskola, Akademin för hållbar samhälls- och teknikutveckling.
    An Engineering tool to calculate heat release rates of multiple objects in underground structures2011Ingår i: Fire safety journal, ISSN 0379-7112, E-ISSN 1873-7226, Vol. 46, nr 4, s. 194-203Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Simple theoretical calculations of the overall heat release rate (HRR) of multiple objects have been carried out. The results were compared to fire experiments in a model tunnel using wood cribs placed at equal distance from each other. Three different methods are presented which are based on physical relations for fire spread between the wood cribs. The first method uses a critical heat flux as ignition criteria while the other two methods use an ignition temperature. The method using the critical heat flux as ignition criteria shows very good agreement with the corresponding experimental results used. The two methods using the ignition temperature as ignition criteria did not agree well with the corresponding experimental results. The prerequisites, that the methods should be kept relatively simple to be of practical use and that the burning objects should not necessarily have to be of uniform composition, were fulfilled.

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  • 16.
    Hansen, Rickard
    et al.
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, Framtidens energi.
    Ingason, Haukur
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, Framtidens energi.
    Full-scale fire experiments with mining vehicles in an underground mine2013Rapport (Övrigt vetenskapligt)
    Abstract [en]

    This report comprises two full scale fire experiments in a mine drift in Sala, Sweden,involving a loader and a drilling rig respectively.

    It was found in the experiment involving the loader that the front part of the vehiclenever ignited. The maximum measured heat fluxes at the front tyres were found tonever exceed the critical heat flux of natural rubber and thus ignition never occurred.Furthermore, the maximum temperature recorded at the hydraulic hoses in the waistwas 381 K, thus the low temperatures did not allow for further fire spread. The maximumheat release rate from the experiment was 15.9 MW and it was attained approximately 11 minutes after ignition. The resulting heat release rate curve of the wheel loaderfire displays a fire that is dominated by initially the sudden increase when primarily the first tyre is engulfed by flames and then by the slowly declining heat release ratesof the large tyres of the vehicle. Still, the stop of fire spread from the waist and forward clearly shortened the duration of the fire considerably.

    It was found in the experiment with the drilling rig that the entire vehicle had participated in the fire and the combustible material had been consumed – except for the hydraulic hoses approximately two meters in front of the cab and forward, some amount of hydraulic oil and most of the low voltage cable on the cable reel. The maximum heatrelease rate from the experiment was 29.4 MW and it was attained after 21 minutes. The resulting heat release rate curve of the drilling rig displays a fire with high heat release rates and relatively short lived.

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  • 17.
    Hansen, Rickard
    et al.
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, Framtidens energi.
    Ingason, Haukur
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, Framtidens energi.
    Heat release rate measurements of burning mining vehicles in an underground mine2013Ingår i: Fire safety journal, ISSN 0379-7112, E-ISSN 1873-7226, Vol. 61, s. 12-25Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Heat release rates from two full-scale fire experiments with mining vehicles in an underground mine are presented. The mining vehicles involved were a wheel loader and a drilling rig typical for mining operations. The calculated peak heat release rate of the loader was 15.9 MW and occurred after approximately 11 min from ignition. The calculated peak heat release rate of the drilling rig was 29.4 MW and occurred after approximately 21 min from ignition. The heat release rate was calculated from measured data of gas concentrations of oxygen, carbon monoxide and carbon dioxide, measured gas velocity and measured gas temperatures. The fuel load of the wheel loader consisted mainly of the tyres, the hydraulic oil and the diesel fuel. The fuel load of the drilling rig consisted mainly of the hydraulic oil and the hydraulic hoses. The calculated heat release rate curves were controlled by comparing the summed up energy contents of the participating components with the integrated heat release rate curves. © 2013 Elsevier Ltd.

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  • 18.
    Hansen, Rickard
    et al.
    Mälardalens högskola, Akademin för hållbar samhälls- och teknikutveckling.
    Ingason, Haukur
    Mälardalens högskola, Akademin för hållbar samhälls- och teknikutveckling.
    Heat Release Rates of Multiple Objects at Varying Distances2012Ingår i: Fire safety journal, ISSN 0379-7112, E-ISSN 1873-7226, Vol. 52, s. 1-10Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Simple theoretical calculations of the overall heat release rate (HRR) of multiple objects at both constant and varying distances have been carried out. The results were compared to both fire experiments in a longitudinal ventilated model tunnel (scale 1:15) using piles of wooden pallets placed at varying distance from each other and with model scale fire experiments (scale 1:4) conducted with a freight truck commodity without roof over the piles of wooden pallets. Two different methods are presented which are based on physical relations for fire spread between the piles of wooden pallets. The first method uses a critical heat flux as ignition criteria while the other method uses an ignition temperature. The method using the critical heat flux as ignition criteria shows very good agreement with the corresponding experimental results used. The method using the ignition temperature as ignition criteria did not agree well with the corresponding experimental results. The prerequisite that the burning objects should not necessarily have to be positioned at equal distance was fulfilled.

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  • 19.
    Hansen, Rickard
    et al.
    Mälardalens högskola, Akademin för hållbar samhälls- och teknikutveckling.
    Ingason, Haukur
    Mälardalens högskola, Akademin för hållbar samhälls- och teknikutveckling.
    Model scale fire experiments in a model tunnel with wooden pallets at varying distances2010Rapport (Övrigt vetenskapligt)
    Abstract [en]

    This report is part of the research project “Concept for fire and smoke spread prevention in mines”, conducted by a research group at Mälardalen University. The project is aimed at improving fire safety in mines in order to obtain a safer working environment for the people working for the mining companies in Sweden or for visitors in mines open to the public.

    This report comprises a number of model scale fire experiments conducted in a model tunnel at SP facilities in Borås, Sweden.

    The main purposes of the report are:

    - Obtain data which can validate models to calculate the total heat release rate of multiple objects

    - To investigate the influence on the heat release rate curve that a varying distance between the fuel objects will have.

    - To investigate the influence on the heat release rate, fire growth rate and time to ignition for adjacent fuel objects. The effects of ventilation are taken into account in the model..

    The work in this report started with describing the theoretical basis of scaling theory and the determination of heat release rate at fire experiments, continuing with describing the experimental setup with the fuel load and instrumentation used. After that the experimental procedure and the experimental results were described and analysed. The results from the experiments were thereafter discussed and finally conclusions were drawn.

    The findings and conclusions of the study were as following:

    It was found that an increasing ventilation rate slightly increases the maximum heat release rate, which is in accordance with earlier research.

    The ventilation rate will have an influence on the fire growth rate. In the tests with the highest ventilation rate, a slower fire growth rate was displayed compared to the other two cases. This could possibly be explained by the fact that the height of the pile of wooden pallets (205 mm) was practically equal to the short side of the pile (200 mm) and the fire was started on the long side, thus as the longitudinal ventilation is increased less fuel area is exposed to the tilted flames resulting in that less parts take place in the combustion during the growth phase and thus the fire growth rate decreases.

    When studying the graphs of the various heat release rates it was found that when the distance between pile #1 and pile #2 increased to a certain level the ignition of pile #2 will be delayed resulting in that not all piles are burned with their maximum heat release rate at the same time.

    The delay in ignition of adjacent pallet can be distinguished by a “hump” before the peak value in the heat release rate curves. In cases with short distances between the piles the ignition of 3 adjacent piles took place almost simultaneously and resulting in a total heat release curve where the pallet piles burn at their maximum at nearly the same time, i.e. the effects of the delay of ignition is not really showing up in the time to reach maximum heat release rate.

    It was also found that the peak value of the heat release rate decreases as the distances between the piles are increased – from ~500 kW down to ~450 kW – as the curve is stretched out in time.

    The ignition data indicated that the time to ignition of adjacent piles would decrease as the longitudinal ventilation was increased.

    Further validation work should take place with respect to validating the experimental data with output data from theoretical models.

    Further studies and experiments should take place that vary additional parameters besides the distance between the individual fuel objects. This in order to make further comparisons with calculation models to predict the total heat release rates of complex objects, such as for example a vehicle.

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  • 20.
    Ingason, Haukur
    et al.
    Mälardalens högskola, Akademin för hållbar samhälls- och teknikutveckling.
    Hansen, Rickard
    Mälardalens högskola, Akademin för hållbar samhälls- och teknikutveckling.
    Kumm, Mia
    Mälardalens högskola, Akademin för hållbar samhälls- och teknikutveckling.
    Nyman, Hans
    Mälardalens högskola, Akademin för hållbar samhälls- och teknikutveckling.
    Koncept för skydd mot brand och brandgasspridning i gruvor: Slutrapport2010Rapport (Övrigt vetenskapligt)
    Abstract [sv]

    Målsättningen med projektet var att ta fram information om brandutveckling och rökspridning igruvor. Resultaten skulle användas för att ta fram rekommendationer för de deltagandegruvföretagen. Resultaten skulle också användas som underlag i framtida riskanalyser och i detsystematiska brandskyddsarbetet. Metoder och verktyg för att bestämma brandutveckling ifordon och rökspridning skulle valideras och utvärderas. Kunskapen skulle kunna användas inomgruvindustrin, men även för andra områden så som bränder i tunnlar under byggnation. Projektetska förstärka forskningsprofilen inom högskolan när det gäller brandsäkerhet iundermarksanläggningar och resultaten skall implementeras i grundutbildningen.

    Projektarbetet har varit delvis fokuserat mot gruvföretag och delvis mot konsultföretag somarbetar inom området. Bra samarbete och diskussioner med de företag i projektet som ansvararför gruv- eller besöksdrift har varit viktigt. Gruvföretagens behov av att få ordning på sinbrandskyddsdokumentation, förståelse för säkerhetsutrustning och insatsplanering samt sittsystematiska brandskyddsarbete, har haft stor betydelse för detaljutformningen av projektet ochpå vilket sätt det har slutligen genomförts. Samarbetet med konsultföretagen har haft en annaninriktning, där fokus istället varit erfarenhetsöverföring när det gäller scenariospel, brandtekniskdimensionering och ventilationsteknik. Deras stöd och hjälp har haft stor betydelse förgenomförandet av projektet.

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