Conical picks of mining machines with increased utility properties – selected construction and technological aspects

Shearers and roadheaders are commonly used to extract useful mineral deposits, especially hard coal, and for drilling roadways in underground mines, tunnels and other underground buildings in civil engineering. As the primary working process of this type of machines, mechanical mining of rocks is carried out by cutting. These machines' working units are equipped for this purpose with picks, usually conical (point-attack). They have the form of an axially symmetrical body consisting of a steel shaft and a tip usually made of tungsten carbide, connected by a hard brass solder. Due to the possibility of spontaneous rotation in the pick holders and even wear and tear of their tip around the entire perimeter, conical picks have a much longer service life compared to radial picks. Their life, especially when cutting hard and sharp abrasive rocks, is, however, still unsatisfactory. Rapid wear of the picks leads to a decrease in mining efficiency, an increase in this process's energy consumption, and an increase in dynamic surplus to which the cutting machine is subject. Among many forms of wear and tear of the conical picks, attention was paid to the problem of asymmetrical abrasive wear of the tips, pulling out the connection of the soldered pick tip and fatigue breaking of the pick shafts in the transition zone of the shank into the shoulder. The article presents original propositions of modification of the construction of the roadheaders/shearers conical pick shafts and the method of fixing the tip in the pick shaft in order to increase their operational durability significantly. The technologies and devices necessary to manufacture conical picks of the proposed structure were described. The developed modifications significantly contribute to the improvement of functional properties, including the reliability of conical picks, used in particular for hard rock mining.

Machines for Mechanical Mining of Hardly Workable and Abrasive Rocks

Mechanical mining is a widely used method for separating material from mined rock in the mining branch, tunnelling, road and construction industries. Depending on the mechanical properties of rocks, most often defined by uniaxial compressive strength, various machines and tools are applied. Apart from rock strength, the efficiency of the mining process is determined by abrasiveness, which affects the rate of tool abrasive wear. Currently, disc mining by static pressure or rear undercutting are the most developed methods. Undercutting can be supported by high pressure water jet or disk oscillation. Mining with drills also utilizes static pressure. In addition to discs, conical picks are applied; they are mounted on cutterheads. In underground mining and tunnelling, there is an increasing need to cut abrasive rocks with a strength of more than 120 MPa in places where explosive materials cannot be used. In the article, the recently applied and developed methods of cutting abrasive rocks characterized by high strength, such as copper, gold, tungsten or platinum ores and diamond deposits, have been presented. Next, the latest machines and machine systems used for their mining are reviewed. Leaders in the mining machinery industry, such as Joy (Komatsu), Epiroc (Atlas Copco), Sandvik and Aker Wirth are developing proprietary designs of cutting machines based on both well-known and completely new ideas.

Methods of Mechanical Mining of Compact-Rock—A Comparison of Efficiency and Energy Consumption

This paper compares the methods of mechanical mining of rock in terms of their efficiency, energy consumption, and the durability of the tools they involve. It presents the advantages of mechanical heading-driving methods. In the first part, we described the methods used to assess rock workability, and the influence of rock types and parameters on mining efficiency. Furthermore, we discussed the compact-rock mining process in terms of the energy it consumes. We provided the description of the most common mechanical methods, such as milling, static crumpling and undercutting, including the tools involved, and the requirements and limitations for the use of these methods. The paper presents unique machinery solutions designed to reduce the energy consumed by mining processes. In the final part of the paper, we propose a solution to select the mechanical method of rock mining as a function of rock type and parameters.

Simulation Study on Energy Feedback for Flame-Proof Integrative Variable-Frequency Motor

In order to meet mechanical mining demand of China's thin coal seaming, the power electronics and motor control system in hardware and software integration is presented, which replace traditional variable-frequency system applied to mining, planning and transport occasions. Solving braking resistor large volume and heat dissipation problem of the variable frequency system is very necessary. Accordingly, energy feedback based on fuzzy PI control type system to replace the traditional energy consumption braking was designed in this paper. Through the system simulation, it is shown that this system has high power factor, small feed current harmonics and effectively absorb the feedback energy, especially can realize four quadrant operations.

Hard Kaolin High Yield and Stoping Technology in Suoli Mine

The backward blasting of the mine technology and stoping technology will lead to a long time of blasting, high labor intensity and low production efficiency, which also cause roof collapse and the blast of fly rock, support fall and overthrowing the chain-trigger, which cause a larger hidden of production. Through using the mechanical mining technology of the high yielding and efficiency of kaolin, which fundamentally improve the working conditions of workers and safety working condition, will laid the foundation for the increasing of production and efficiency. The production has been promoted from 250-300t/d to 550-650t/d now, which the efficiency is increasing more than 120%. Meanwhile, the optimal of blasting parameters is benefit to roof control after blasting, which can improve the efficiency of blasting, reduce the unit consumption of dynamite, which can save about 0.115kg/ m3; and reduce the intensity of the workers and the damage of the support. This construction technique can provides a reference significance for safe and efficient construction of the mine under similar geological conditions.