Background Accidents related to slips, trips and falls represent roughly one fourth of the total accidents in the mining and quarrying industry in Finland. According to a recent estimate, in Finland, an accident involving a fall costs about 6000 € on average. Working in the northern open pit mines exposes the workers in harsh weather conditions where pedestrian walkways are often very slippery because they are covered by ice and snow. Therefore it is essential that the footwear used by the workers has good grip in those conditions.
Description of the problem Footwear selected to be used in the mine work is normally based on the risk assessment because some workers do occasionally work that includes welding the footwear are selected on those based on those criteria’s. Most commonly the footwear soles are selected so that they are resistant to hot contact (HRO) according the PPE-footwear standard. This leads to the selection of footwear which sole are made from dense materials like nitrile rubber. Using of those dense polymers like can be problematic in the arctic area because the slip resistance of the footwear soles made from dense materials is found to be poorer than footwear made from softer soling materials. The cold climate can increase the hardness of the soling material which makes footwear even more slippery.
Slip resistance, i.e. dynamic coefficient of friction (DCOF) of the footwear was measured in laboratory by using FIOH’s own laboratory device slip simulator. Measurements were carried out according the parameters defined in the standard EN ISO 13287: 2012 Personal protective equipment-Footwear-Test method for slip resistance. The standard method was modified only by using smooth ice surface as a test surface. Ten consecutive measurements were done by each footwear model. The mean value and standard deviation was calculated. In addition the footwear was pre-conditioned in the climatic chamber at the temperature of – 20 C° for four hours in order to see how the hardening of the sole materials affects to the slip resistance. Hardness of the sole was measured by using hardness tester with Shore (A) hardness scale.
Four different footwear were selected and collected form the mines participating in the project. Three of those footwear were safety footwear according EN ISO 20345: 2011 they were half-knee height leather footwear designed for winter conditions. One sample was rubber boot from Russia and it was not classified as safety footwear according to EN or ISO standards. Additionally six different safety footwear for winter conditions were selected in order to compare level of performance the slip resistance of footwear used in mines to the winter footwear available in the market.
Results Samples collected from the four mines got almost equal DCOF levels than the winter safety footwear selection from market when they were measured without pre-conditioning, but the DCOF values were 39% lower compared to winter safety footwear selection when the samples were pre continued in climatic chamber. Hardness of the footwear sole increased 26% in average because of the pre-conditioning in cold.
Conclusions Footwear currently used in the four mines have reasonable good slip resistance compared to footwear’s available in the market, but their fiction level is strongly dependent of the temperature. For safety reasons, it would be advisable to use footwear sole materials which are not so much affected by the temperature changes especially in the artic area mines.
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