Diamond Wire Cutting Test in Nordic Winter Time

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1 Diamond Wire Cutting Test in Nordic Winter Time Seppo Leinonen Synopsis Wire sawing is becoming more common in dimension stone quarries in Finland. Wire cutting improves overall efficiency of block production and carbon dioxide foot print is considerably lower compared to that caused by drilling and blasting. Winter season in Finland lasts 4 6 months, average temperature varies from south coastal areas 5 o C to north areas 13 o C. So, freezing conditions set a big challenge to water using wire quarrying. Winter time wire cutting was tested by Geological Survey of Finland in project Resource Efficiency Development of Natural Stone Production. Project is funded by local municipalities, stone companies and European Regional Development Fund, ERDF. Experiences of wire sawing in Nordic winter time were positive and so far recommended to take the method to all seasons use in industrial production. Keywords Dimension stone, diamond wire, winter time, black stone, carbon dioxide. Background A significant development in the Finnish stone industry took place in the 1970s. The extraction techniques got notable efficiency and production cost per ton of stone decreased considerably. This was achieved with easily used plastic tubes packed explosives, also speeding the operations by hydraulic drilling rigs and large wheel loaders. For example, a hydraulic drilling equipment is three times faster than old pneumatic technique. Although the drilling blasting method is fast, it breaks the stone in all quarrying steps from primary extraction to final shaping the blocks, especially with black stones. Currently, more resource efficiency is being developed by stone saving methods, including diamond saw cutting (Medda et al., 2015). Although it makes sense to gain more block for sales and reduce CO 2 emissions in the production at the same, when taking wires in all seasons use in Nordic countries, there is still the major challenge, how water using method operates in freezing winter conditions. Test conditions Diamond wire sawing uses water for cooling and removing stone fines from the cut line. In Finland, winter time and frosts last for days, i.e. 4 6 months (Fig. 1). In order to completely take the diamond wire cutting as a main quarrying method, it should be found ways of quarrying also in freezing conditions (Fig. 2). In addition to develop winter time technologies, it was also examined differences of the cutting performance with two black stone types. Test periods were carried out in Kivilahti diabase and Oulainen gabbro quarries, of which the winter seasons test in Kivilahti. Test period in freezing conditions was made in the first weeks of December Temperature was below zero in all days, varying from 2 degrees Celsius ( o C) to 18. Temperatures in early mornings were typically some lower than daytimes. Lowest temperatures, when wire cutting has been done has been as low as 25 o C. At that cold conditions, it is also possible to make block shaping by dry cutting. During winter test flushing water was taken from a local river. Pipe line was dug below surface. The

2 freezing of the pipeline was prevented by pumping water continuously and emptying the lines at the end of the working day. Fig. 1 Winter time in Finland, in days (Ilmatieteen laitos, 2017). Fig. 2 A horizontal wire cut in frozen diabase at Kivilahti, air temperature 18 o C (photo 12 th December 2016). Black stone types Wire sawing performance was compared at two different black stones, Kivilahti and Oulainen (Fig. 3). Kivilahti formation, located in Ilomantsi East Finland is a diabase dyke; Oulainen black, located in West Finland is a gabbro intrusion. Both stone types are fine grained (average dimension 1 2 mm), mineral contents plagioclase, amphibole, pyroxene and Fe Ti oxides. Oulainen gabbro includes in addition 20% biotite. Mechanical properties varies quite much between these two stone types, of which Oulainen is a moderately (Mesimäki, 1994) and Kivilahti a high strength black stone (Pirinen, 2010), Table 1. Fig. 3 A) Kivilahti diabase and B) Oulainen gabbro. Size in both samples is 80 mm (width) x 40 mm (height). 2

3 Table 1 Mechanical properties of Kivilahti diabase and Oulainen gabbro. Kivilahti Oulainen EN Water absorption % EN 1936 Open porosity % EN 1936 Density kg/m EN Flexural strength MPa EN 1926 Compressive strength MPa Results In winter time test the total cut was 374 m 2, most of that in horizontal direction. The test was succeed. There was no technical problems and pipelines didn t froze even the water was taken straight from ice covered river without any heating. The most critical moment of stuck wire by freezing is when sawing starts on frozen bedrock surface. It is also very important to avoid stopping the wire, especially for horizontal cutting. The frozen wire is easier to melt in vertically line by warm water. When the wire is already running as a depth of 2 meter in the rock, the risk of freezing is significantly reduced because at this level the temperature is not any more below zero degrees Celsius, o C. Flushing water is able to take from local lakes, rivers or wells. It is also possible to bring water by tanks, in that situations heating should be arranged. It is recommendable to use heated water (+30 o C) always when the air temperature is below 10 o C or if there seem to appear any other risk of stuck wire. During the winter test water supply was liter per minute, about the same than in summer operation (Fig. 4). Fig. 4 Formation of ice on pulley and drive wheels. Photo was taken on 12 th December, daytime temperature was 18 o C. Wire saw unit is Huada 55 kw, powered by a diesel aggregate Iwego 175 kw. There is no significant difference in sawing performance comparing a single primary cut in summer and winter season at Kivilahti quarry. The speed of primary cut with a long wire was about 7.9 m 2 per hour (Table 2). The durability of wire is the same as in the summer operation, about 10 m 2 cut per wire meter. The optimal speed of wire was 30 meters per second (m/s) and an applied tension amps (A). The length of the wire loop was 80 m at the start of the cut. Comparing the saw performance of the Kivilahti diabase and Oulainen gabbro, there is a remarkable difference. Gabbro is able to be cut two times faster (20.6 m 2 ) in an hour than more strength having diabase, 293 MPa compressive strength (that of gabbro 210). The high cutting speed is also able to be explained by little lower Mohs 3

4 hardness 5.7 (that of diabase 5.9). Oulainen gabbro contains otherwise the same minerals but also soft mica about 20%. Used wire in both test places was Tyrolit GSF 5 (with specification for hard granite). The number of diamond beads, 11.3 mm in diameter, were 40 per meter. Table 2 Technical parameters of diamond wire sawing test in Kivilahti and Oulainen blacks. Kivilahti Oulainen Wire speed m/s Cutting performance m 2 /h Applied tension A Wire life m 2 /w m Energy consumption KWh Discussion Considering a single cut there are no significant difference in performance of summer and winter time diamond wire sawing. At Kivilahti diabase quarry it is able to saw 7.9 m 2 per hour with a long wire loop. Kivilahti black is an example of a high strength stone, 293 MPa compressive strength by EN The need for energy in the wire cuttings was about 50 kw in an hour. CO 2 emissions for example of 10 m 2 cutting is 13 kg CO 2. An average CO 2 value of electricity power output in Finland is kg CO 2 kwh. Wire sawing causes about 10 times smaller emissions than values of the drilling rig worked the same surface area, 110 kg. High CO 2 values of drilling machines comes from slow penetration in diabase ( meter/minute) and need to make holes in tight row, cm spacing. Comparing different black stone types, there is a major difference in cutting performance between Kivilahti and Oulainen. Kivilahti diabase represents a high strength black, instead Oulainen gabbro a moderately strength type (210 MPa) and able get great measurements as high as 20.6 m 2 opening per hour. Test results of wire sawing in Nordic winter time were positive and the method is recommended to take in industrial use, for all seasons. Acknowledgments The author would like to thank the owners of the quarries Kaivu ja Kuljetus Pyöriäinen Ay (Kivilahti diabase) and OK Graniitti Oy (Oulainen gabbro) to make the wire cutting tests possible. I also acknowledge The Regional Council of Pohjois Savo for funding the project. References ILMATIETEENLAITOS, Ilmasto/Vuodenaikojen tilastot/talvitilastot [online]. [viewed 9 October 2017] Available from: (in Finnish) MEDDA, P., LEINONEN, S., SELONEN, O., CAREDDU, N., SIOTTO, G., A feasibility study of a potential dimension stone occurrence of brown granite in Nopala (Finland). Marmomacchine, n. 242, aprile 2015, pp Ed. Promorama, Milan, Italy. ISSN: MESIMÄKI, P. Oulainen gabbro in Luonnonkivikäsikirja, Kiviteollisuusliitto, (in Finnish) PIRINEN, H. Mekaanisten ominaisuuksien määritys, 11C26/10. Stone Pole Laboratorio, (in Finnish) 4

5 About the author Seppo Leinonen, Head of Unit Industrial minerals Geological Survey of Finland, P.O. Box 1237, FI Kuopio, Finland. 5