# Performance Evaluation of Heading-and-Winning Machines in the Conditions of Potash Mines
## 2 Performance Evaluation Procedures for Heading-and-Winning Machines in Potash Mines  
The task of assessing the efficiency of the use of heading machines for potash mines is possible through the development and implementation of automated on-board systems that monitor the operating parameters of mining machines. Such systems should be based on scientifically grounded methods of collecting and analyzing recorded data, aimed at ensuring trouble-free operation and increasing the productivity of mining equipment [6; 7; 8; 9; 10; 11; 12; 13; 14; 15; 16; 17; 18; 19; 20; 21; 22]. The technical literature indicates that the most informative and simple method of monitoring the performance of mining combines is continuous monitoring of the load on the drive motors, carried out by measuring currents, voltages and active and full capacity. It is also necessary to monitor the movement, feed rate and productivity of the combine and relate these indicators to absolute time. It is known that the performance of extracting machines in real operating conditions can be reliably evaluated by correlating the basic (nominal) and actual values of energy indicators describing their operation. For combines operating in potash mines, one such indicator is the specific energy consumption for the potash ore mining process \(H_{w}\)[23; 24; 25; 26]. The basic value of the specific energy consumption for the destruction of the potash formation by the combines' cutters and for ore loading is calculated by the formula:  
\[H_{wb}=\frac{\Sigma P_{r}}{60\text{Q}}\, \tag{1}\]  
Figure 1: Ural-20R-11 Combine (general view). where \(H_{wb}\) is the base value of specific energy consumption for the destruction of the potash formation by the combine's cutters and for ore loading, kWh/t; \(\Sigma P_{r}\) is the rated power of actuating units of the combine's final elements, kW; \(Q\) is the combine's technical performance, t/min. For example, according to the results of calculations carried out for latest and most productive domestic combines Ural-20R with a productivity \(Q\) = 8 t/min and ore cutting resistance \(A_{\text{c}}\) = 450 kN/m, the base value of specific energy consumption for the extraction of potash ore is \(H_{wb}\) = 1.16 kWh/t. The index of potash ore cutting resistance \(A_{p}\) is related to the ultimate compression/shear strength of the ore by empirical dependences  
\[f_{c} =0.09A_{c}; \tag{2}\] \[\tau =0.33f_{c}, \tag{3}\]  
where \(A_{\text{c}}\) is the cutting resistance of potash ore, kN/m; \(f_{c}\) is the ultimate compression strength of potash ore, MPa; \(\tau\) is the ultimate shear strength of potash ore, MPa [5]. The actual values of the specific energy consumption for the analysed time period \(T\) of the combine operation are based on the data on the energy consumption and the mass of ore mined during this period:  
\[H_{wa}=\frac{T\Sigma P_{a}}{G}\ \, \tag{4}\]  
where \(H_{wa}\) is the actual value of the specific energy consumption for the extraction of potash ore during the operation of the combine in the analysed time period, kWh/t; \(T\) is the duration of the controlled period of the combine's operation, h; \(\sum P_{a}\) is the sum of the average values of the effective power of the combine's electric motors over the controlled period \(T\), kW; \(G\) is the mass of mined ore, t.  
The ratio of the base value of specific energy consumption to the actual value is used to calculate the energy efficiency coefficient of the heading-and-winning machine \(k_{e\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\! \!\! The quantitative values of the coefficients for productivity and energy efficiency define, respectively, the technological and technical levels of organisation of the potash ore mining process. Comparison of the quantitative values of the considered complex indicators provides for a cumulative assessment of the performance of heading-and-winning machines, taking into account the specifics of their functioning conditions [7; 24].