Vol 65 Iss. 1

During 1967–1970, the operation of wide- and narrow-cutting combines was studied at Norilsk mines. During the tests, the average and instantaneous values of power consumption P, current I, feed rate vₙ and feed force Fₙ were measured. Special sensors and recording equipment were manufactured to record these parameters. One of the tasks of the tests was to establish the dependence of combine productivity on the extracted thickness of the seam.

At present, mining machines operate with electro-hydraulic feed drives of the “Ural-33”, “Ural-37”, and G-404 types, the technical and dynamic properties of which have been studied insufficiently.

Productivity of mining combines largely depends on the efficiency of the feed drive, which ensures machine movement during operation and maneuvering operations. The complexity of the design, high precision of manufacturing and the need for high reliability, especially when working in mechanized complexes, require a thorough inspection of the feed drive as a unit before the machine is taken into the mine. Such a check can be carried out on test benches. Thus, at the ore-repair plant named after V. I. Lenin of the Tulaugol combine, repaired feed drives G-404 are checked very carefully.

Of great importance in the selection of hydraulic drive for mining machines is the development of more convenient methods of using the characteristics of the hydraulic drive. The main role in the transformation of speeds and torques of the hydraulic drive is assigned to two of its properties: the graphical representation of these two properties on the operational characteristics of hydraulic turbine transmissions has been called stiffness and non-transparency.

The dynamic character of the action of a hydraulic monitor jet on a monolithic massif is related to the well-known Bernoulli formula for the pressure force of a stationary jet on a plane perpendicular to it...

In the process of operation of the hydraulic monitor complex, the pressure at the nozzle of the hydraulic monitor varies during the shift due to switching on and off of consumers of high-pressure hydraulic energy. These pressure fluctuations affect the performance of hydraulic breaking.

Jet devices, or ejectors, are characterized by simplicity of design, reliability and ease of operation. Therefore, despite the relatively low efficiency, they are very widely used in various fields of technology as pumps, compressors, hydroelevators, fans, and vacuum pumps.

In calculations of horizontal and lifting belt conveyors, the value of the preliminary tension of the belt is determined, as a rule, by the condition of absence of slippage of the belt on the drive drum and is calculated by the well-known formula. Increasing the traction capacity of a single-drum belt conveyor drive is an important problem, the solution of which makes it possible to significantly reduce the maximum tensile forces in the belt by reducing its pretension. The use of atmospheric pressure to increase the traction capacity of the drive is one of the cardinal ways to solve this problem.

Studies of the movement through slurry pipelines of hydraulic mixtures with different degrees of concentration showed that this process is probabilistic; this is due to the random nature of the distribution of velocity pulsation frequencies and the occurrence of turbulent vortices in the flow. With increasing concentration of hydraulic mixture, the suspending capacity of the flow increases, while the intensity of its mechanical effect on the solid component increases, and the probability of collision of particles with each other increases.

Hydraulic transportation of ores is usually accompanied by a change in the particle size distribution of the transported material. This is especially characteristic for transportation of multi-fraction hydraulic mixtures along complex routes, with a significant difference in elevation of the beginning and end of the line.

The proposed form of the generalized equation of hydraulic resistance, while retaining the main properties of equations of this type, has the advantage of being oriented toward dependence on the rational flow velocity.

There are known cases when start-up processes of hydraulic transport plants were accompanied by accidents. The cause of such accidents is water hammer arising due to the formation of “plugs” and breaks of flow continuity at the moment of switching on subsequent stages in schemes with several pumping stations operating in series. “Plugs” in pipelines occur, as a rule, during previous stops.

Hydraulic transportation of bulk materials is finding increasingly wide application in various sectors of the national economy. Numerous studies conducted by various organizations show that the efficiency of hydraulic transport increases with increasing concentration. However, in many cases, due to technical and technological conditions, it is impossible to obtain high-concentration flows or use hydraulic mixture thickeners, as some of them cannot provide high concentration, while others, due to their design features (large overall dimensions, weight), cannot be used in continuous transport systems. Therefore, the creation and introduction into production of new types of thickeners is currently of great importance.

If an emergency stop of a mine train is required, the car inductor brakes and the mechanical brakes of the electric locomotive are applied simultaneously. Car inductor brakes act as absorbers of the maximum initial speed, due to the instantaneous distribution of braking force along the length of the train.

The study of operational reliability of heavy-duty dump trucks BelAZ-540 and BelAZ-548A was carried out in extremely difficult natural and climatic conditions of the apatite mine “Tsentralny”, located in the center of the Khibiny at an altitude of 1000 m above sea level. Reliability analysis was performed on the basis of data for 1970–71. Only relatively serious failures of vehicles, which required at least two hours for their elimination (including the time for fault detection, dump truck travel to the repair shop and the time of all operations related to repair), are taken into account, since there is practically no information on minor failures.

Increasing the efficiency of use of open-pit dump trucks is impossible without scientifically based estimation of their operational qualities, operating conditions and the level of organization of the technological process. Long experience of operation of heavy-duty dump trucks has shown that the operating modes under conditions of the North sharply differ from those at open pits located in more favorable climatic zones.

In the practice of operation of mining enterprises, there are widespread cases when the entire cargo flow from a group of mines to consumers follows through one marshalling station. In such a scheme, the total cost of transportation does not depend on the relationships of consumers and suppliers (at given volumes of production and consumption of individual production units).

In coal open pits, the most productive method of blast drilling, in which rocks are destroyed by the principle of cutting, is becoming more and more widespread. The main disadvantage of this principle is the rapid dulling of rock-destroying tools.

Semi-bunker storage with a slotted outlet is a type of modern automated large-capacity storage. The criterion for selecting the main parameters can be taken as the minimum cost of storage construction, since a change in the length L and cross-section F of the stockpile has a relatively small effect on operating costs.

Fan characteristics are widely used in both design and in the operation of ventilation systems of mines. Different interpretations of certain aspects of this issue have until now been given little importance. However, now, with the transition of industrial enterprises to new management principles and economic incentives, engineers must find reserves for saving material resources and reducing production costs. At enterprises, increasing importance is being attached to testing of mine fans, and it is here that contradictions are found in the theory and interpretation of certain issues related to the evaluation of the efficiency of main mine exhaust fans.

There is a very extensive literature on diffusers, and in modern scientific and technical sources this issue receives much attention. Most of these studies are related to the development of diffuser designs and are devoted to the determination of the optimum angle of diffuser opening behind centrifugal and axial fans, pressure losses in diffusers, optimal diffuser length, etc.

Experimental and theoretical studies carried out at the LMI to create a two-stage active hydraulic turbine with inclined-jet stages, the hydrodynamic scheme of which is shown in the figure, have shown that the characteristics of such turbines fully meet the objectives of turbine drives at hydraulic mines and have a number of advantages. The most important of them are the relatively low specific speed of the two-stage turbine motor, small radial size and the axial discharge of exhaust water characteristic of the motor. As shown by tests of an experimental prototype of such a turbine motor, with correctly specified design parameters, in terms of its efficiency it is not inferior to the currently used radial and bucket turbine motors.

Analysis of the operating process of the slant-jet hydraulic turbine on the basis of the Euler equation shows that the hydraulic efficiency of its impeller is expressed by expression (1). When calculating the efficiency and the nominal value of the peripheral velocity of the wheel of a slant-jet hydraulic turbine, hydraulic losses along the entire flow path in the turbine should be taken into account.

The total heating surface of a mine air heater is calculated by the maximum heat release required from it Qₜₘₐₓ (kJ/h), calculated by the absolute minimum of the outside air temperature for a given location from expression (1). ...

It is known that at the vast majority of mines located in areas with severe climate, in winter time part of the atmospheric air supplied to underground workings for their ventilation is heated. To this end, at shafts and adits where the ventilation air comes, steam air heater units with a multi-row arrangement of metal plate air heaters are usually constructed; the sequential movement of heated air in them provides the necessary air temperature drop...

The proposed method of thermal design of steam air heater units based on the temperature criterion allows for thermal design, layout, and selection of the model and size of the air heater with the most favorable economic performance during operation.

The actuating tracking mechanism consists of a two-piston servomotor, the pistons of which are connected to each other by a toothed rack that transmits motion to an output shaft and a wedge acting on the feedback sensor.

Ya. P. Grinberg believes that calculations of the possible productivity of coal mining machines based on their energy characteristics and on the characteristics of the electric motor or on specific energy consumption are inadmissible in practice, because they do not take into account the variable nature of the load and frequent switching of the motor, and recommends calculating by the root-mean-square current of the motor and its characteristics. Despite the novelty and scientific and practical value of this recommendation, the author's conclusion cannot be agreed with for a number of reasons. ...

Methods of calculating the performance of mining machines associated with the use of the energy characteristic and the motor characteristic have a number of significant disadvantages. Firstly, they do not take into account the significant load non-uniformity arising from random factors (variability of cutting resistance, non-uniform feed, finite number of cutters, etc.). Secondly, the energy characteristic does not provide information for predicting instantaneous values of maximum loads, which may be the cause of motor stalling. Thirdly, they do not take into account the additional heating of the motor during operation with reduced voltage, which is not uncommon in section electric networks.