Analysis of connecting a forcing fan to a multiple fan ventilation network of a real-life mine

Abstract

Abstract The important role of ventilation in underground mines is to guarantee safety and proper environmental conditions in all accessible areas of a mine by applying national mining laws and regulations. A mining ventilation network changes all the time as a result of moving working areas. It frequently results in an increased length of primary intake and return routes, which in turn increases the equivalent resistance of a complex ventilation network. It is necessary to undertake activities to maintain needed airflow rates in branches of ventilation network. In the conditions that prevail in copper mines in Poland, the number of downcast shafts is usually greater than that of upcast shafts. Developing new mining areas in a mine is released by subsurface roadways. If developing of mining areas is realised by shafts the most commonly used ones are downcast shafts. It is difficult to obtain demanded air distribution in ventilation network of the mine due to the large distance between the downcast and upcast shafts. In one of the Polish copper mines, installing a subsurface main fans’ station at a downcast shaft, aimed at increasing airflow rates in the ventilation network, is being considered. The paper is devoted to the analysis of the possibility of increasing airflow rate in a ventilation network in this mine. The first example of building in a forcing fan in the ventilation system with a single downcast shaft and one upcast shaft is shown to illustrate the complexity of the issues in the real ventilation network of the mine. Then the impact of embodying the forcing fan to the ventilation network of the real copper mine with a multiple-fan network is analysed. Computer software can be used to solve the ventilation system for such an analysis. Most of the software is based on the model of air distribution in the ventilation network known as The Hardy Cross procedure. The principles governing such a procedure have been discussed in the article. The results of the analysis let us draw a conclusion that a significant increase in the total air supplied to the mine with a complex structure of the ventilation network is difficult to obtain using underground forcing fans. The only tangible benefit of the presented solution is a change in air distribution in excavations located a short distance from the downcast shaft at which a forcing fan could be installed. An increase in airflow rates in mining districts located near this shaft is possible. However, it must be remembered that connecting the forcing fan in one downcast shaft of the multi-shaft network decreases airflow into other downcast shafts.