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Literature survey – fire and smoke spread in underground mines
Mälardalen University, School of Sustainable Development of Society and Technology. (Safety Science Lab)ORCID iD: 0000-0002-8326-2860
2009 (English)Report (Other academic)
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.

Place, publisher, year, edition, pages
Västerås: Mälardalens högskola , 2009. , 72 p.
Series
Studies in Sustainable Technology / Forskningsrapport, 2009:2
Research subject
Energy- and Environmental Engineering
Identifiers
URN: urn:nbn:se:mdh:diva-9624OAI: oai:DiVA.org:mdh-9624DiVA: diva2:320392
Projects
Concept for fire and smoke spread prevention in mines
Available from: 2010-05-25 Created: 2010-05-25 Last updated: 2014-01-07Bibliographically approved

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