Real-Time Monitoring and Alarm System in Underground Coal Mines Using Smart Helmets (A Case Study: Tabas Coal Mine)

Regarding the hazard-prone working conditions in underground mines, synchronous monitoring and alarm system is vital to increase the safety. By analyzing the accidents in underground mines in Iran, it can be deduced that most fatalities are related to harmful gas leakage, objects drop off on the head, and not using helmets by the staff. Therefore, a smart helmet with the capability of measuring harmful gasses (regarding the type of the mine), detection of the existence of the helmet on the head, temperature and humidity measurement, and detection of blow on the head is designed and fabricated to eliminate the present dangers and problems. This system displays the evaluated data on a developed software through wireless data transmission hardware. The data transmission hardware is the primary link between the intelligent safety helmet and the software. To follow the idea, practical experiments have been performed in Parvadeh four and East Parvadeh of Tabas coal mine to confirm the validity of data transmission that culminated in successful results. The results were altered by the complexity of the design of the underground spaces so that in a straight direction, data transmission was held until 430 meters. However, further progress was not possible due to tunnel limitations. Data transmission was reduced to 190 meters in access horizons with curvatures or tilts. According to present standards, some thresholds are defined for each of the mentioned cases such that alarm protocol is activated by exceeding these thresholds in critical circumstances. Then the helmet user and the software’s operator will be informed of the occurred danger and will settle the problem.

AVAILABILITY SIMULATION AND ANALYSIS OF ARMORED FACE CONVEYOR MACHINE IN LONGWALL MINING

Since coal mining production systems are very complex, repairing equipment is expensive. If a system failure occurs, it will cause disturbances such as inoperable equipment, reduced operating time, increased production costs, and reduced equipment performance. Therefore, it is necessary to consider the availability of the coal mining industry more than ever. For this purpose, the Armored Face Conveyor (AFC) machine failure data was gathered over a period of 29 months from the Tabas Coal Mine. Descriptive statistics, trends, and serial correlation tests of the data were calculated. Then, the system’s mean and point availability were simulated. Based on the results, the mean availability (all events) and point availability (all events) at 360000 h are 96% and 95%, respectively. The mean time to first failure (MTTFF) of the AFC machine was about 23.61 h. The ReliaSoft Failure Criticality Index, ReliaSoft Downing Event Criticality Index, and ReliaSoft Downtime Criticality Index electrical equipping have the largest effect, whereas the main drive subsystem is the least important. Analysis showed that availability has a direct correlation to activity management and improvements in the quality, efficiency, and the product extraction.

DETERMINATION OF METHANE DESORPTION ZONE FOR THE DESIGN OF A DRAINAGE BOREHOLE PATTERN (CASE STUDY: E4 PANEL OF THE TABAS MECHANIZED COAL MINE, IRAN)

Underground coal mining is known as one of the major sources of methane emissions which mainly occurs after underground coal extraction. Rock strata in-situ methane can potentially be the most significant hazard in coal mining operations. To prevent or minimize the risks of methane emissions, methane drainage approaches have been adopted by coal mines. Rock mass methane drainage is the most efficient and effective approach toward controlling methane hazards as it prevents and reduces the frequency of methane emissions, outflows into the working area and sudden outbursts of methane and rocks. The method includes drilling boreholes from the tailgate side to the unstressed zone in the roof and floor strata above and below a working coal seam. The coal seam gas content in Tabas Parvadeh I is estimated to be about 16 m3 /t, which is relatively high. Based on exploration data, five distinct coal seams have been identified (B1, B2, C1, C2 and D) at the coal deposit and currently C1 is being worked. Considering the high value of C1 gas content and surrounding rocks, the Methane Drainage System (MDS) has been utilized for gas drainage. This paper tries to determine the desorption area which is essential and helpful for the selection of an effective drilling pattern into the adjacent coal seams. In this study, the methane drainage zone in the E4 panel of the Tabas coal mine was calculated using experimental equations and a drainage borehole pattern was determined.

RELIABILITY-CENTERED MAINTENANCE FOR SPRAY JETS OF COAL SHEARER MACHINE

Spray jets constitute one of the most important parts of each type of rock cutting machine, especially the drum shearer. This system cools the cutting picks and controls the dust emission. The blockage of spray jets causes the coal shearer machine to stop automatically. Therefore, the reliable performance of this system assists the achievement of a smooth coal cutting operation. Field's data shows that the maintenance of this system is time-consuming and causes major downtimes in the production process. Therefore, it is essential to find an optimum preventive maintenance task and intervals, to reduce the downtime and minimize the associated costs of the machine. The aim of this paper is to identify an applicable and effective maintenance task, with its associated interval, for management of the failure modes of the spray jets of coal shearers. A case study has been conducted on spray jets of double-drum shearer machine in Tabas Coal Mine in Iran. In the study, the RCM approach is used to select an applicable and effective maintenance task. The failure data were analyzed using a parametric approach to evaluate the reliability of the spray jets, and to estimate the reliability parameters. A reliability-based cost modeling has been implemented to identify the optimum maintenance interval and frequencies of restoration for the spray jets. In the study, a cost rate function (CRF) has been introduced in which an as-good-as-new (AGAN) effectiveness for restoration actions is considered. The CRF also considers restoration and repair times, and takes into account the costs associated with repair and restoration, and the opportunity cost of the equipment's lost production due to maintenance downtime, to arrive at the most cost-effective maintenance intervals. The results of the analysis have shown that the minimum cost per unit of time, $46.5/h, will be achieved within a range of intervals i.e., T = 210 h to T = 260 h .