An analysis of selected jet fans used in chambers of KGHM mines with respect to the air stream range

Abstract

The ventilation hazards occurring in the mining of Polish copper ores are related to environmental conditions and exhaust gas emissions from mining machines and equipment.Mitigation of these hazards requires adequate ventilation of underground excavations. The main sites for the exploitation of copper ore are the chambers excavation, ventilated by means of jet fans. The prevailing gas and thermal conditions at the chambers require the provision of an adequate air supply. The air stream supplied to a chamber must ensure that the gases generated in the production process are diluted to concentrations not exceeding the limit values specified in the regulations, and that the air temperature does not exceed the limit value.The article presents the results of parameters measurement of 6 jet fans installed in a chamber excavation. The axial-flow jets had diameters 400–800 mm, nominal air flow rates from 3.4 m3/s to 11 m3/s and nominal pressure increase 670–1770 Pa. The following parameters were measured: the flowing air velocity, total and dynamic pressure, and air physical parameters. The measurement of air velocity was performed at the excavation cross-sections at distances of 20, 40 and 60 m from the fan outlet. Based on the results obtained, the fan parameters were determined, such as air volumetric flow, draft strength and air stream power. The following parameters were defined in the measurement cross-sections: velocity fields, average and maximum velocities. Determination of the range of air streams generated by the fans being tested accounted for an important aspect of the study. The in situ research was carried out in the chamber excavation located at the KGHM copper mine at Rudna.Based on the results obtained, it was found that the maximum air velocities reached, respectively: 20 m from the fan outlet - from about 1 m/s to 3 m/s, 40 m from the fan outlet - from 0.15 m/s to 0.42 m/s, whereas only thermal movements of the air were observed at 60 m from the fan outlet.According to Polish regulations, only two fans can be used for chamber excavations of up to 60 m in length. The other fans have an airflow range below the required 45 m value. It was also found that the outlet volumetric flow, the outlet air stream power, shape and compactness of the stream constitute a significant factor influencing the range of the air stream.