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.
2010. , p. 65