Home – Home – Jornals – Advanced Search

The authors report and discuss the experimental results on an air drill hammer with an elastic valve installed in the backstroke exhaust line for mechanical closing. It is approved that such air hammer is capable to ensure the wanted blow capacity at fixed blow energy by varying blow frequency through adjustment of cross section choke coupling the backstroke and front stoke chambers of the hammer. With larger cross section of choke coupling, the maximum blow frequency is achieved and remains the same later on.

The article presents a calculation procedure for limiting rotation frequency of an axial main mine fan rotor. The calculations are made for fan model VO-21. The suppositions that make the calculations simpler without considerable errors of the results are evaluated. The calculations use the finite element method and ANSYS software. The critical frequencies are determined from the Campbell diagrams plotted for the estimates with and without regard for the stiffness of the bearing assemblies of the rotor. The effect exerted by the rotor bearing assembly stiffness and by the gyroscopic moment of the fan impeller on the frequency of free bending vibrations of the rotor shaft under direct and back precession is illustrated. The estimated critical frequencies are compared with the analytical data obtained based on discrete two-mass models. For the preliminary engineering estimation, it is possible to use a discrete two-mass model of the fan rotor without regard for the yielding of the bearing assemblies and for the influence of the gyroscopic model; in the design model, it is required to replace the transmission shaft by the point mass. The calculation error will not exceed 7%.

The structural layout is presented for a hybrid unit for directional hydrofracturing with the description of operating principles of the unit in the mode of drilling and slotting. The kinematic parameters of the movable parts of the unit are calculated.

A formalized approach is proposed to evaluating design loads on shovels with compound kinematic chains, based on numerical estimates of response of primary structural members to unit forces. The practical implementation of the approach uses structural layout of a mine shovel with electromechanical push-bars of pressure and uplift drives.

The authors give theoretical and actual evidence of reduction in absolute methane release under higher rates of advance of production face in coal mines. The parabolic relation between methane release, feed speed and productivity of cutter-loader is evaluated.

The experimental studies allow determining efficient parameters of a technology meant for formation of pay zones in gold mine waste dumps. The technology is applicable to developing gold mine waste early assumed unprofitable.

The analytical research has yielded differences in composition of mineral species on the surface of natural diamonds of hyperaltered kimberlites under conditions of diamond ore occurrence and processing. The classification of the mineral species is based on the mineral origin, properties and attachment on the diamond crystal surf.

Under discussion is collectability of ethyl and butyl xanthate species resulted from non-stoichiometric interaction with oxidizer. It is visually proved that solution contains fine micro-drops stabilized by negative charge. The size and ζ-potential of micro-drops are determined together with the spreading velocity of emulsion over water surface. The mentioned velocity is higher than the spreading velocity of products of non-stoichiometric interaction between xanthate and heavy metal salt. The products of interaction between xanthates and oxidizers, at the moment of rupture of water film between mineral particle and air bubble, can detach from particle surface and attach to air-water interface (desorbable species DS). Spreading of a DS over the interface forces water out of the film. The forces applied to liquid in the film from the side of DS of ethyl and butyl xanthates are evaluated. The volume-flow rate of water from the film is related with the surface pressure of reagent species active at the air-water interface. The surface pressure of dixanthogen-xanthate emulsion is evaluated as a function on initial concentration of xanthate. Collectability of a reagent depends on the surface tension of solution of its DS and is governed by the structure of hydrocarbon fragment of the agent.

The authors report studies into adsorption of tannin and cow-parsnip extract components on stibnite, arsenopyrite and chalcopyrite using UV spectroscopy, scanning laser microscopy and measurement of air bubble detachment from mineral particle. It is found that tannin and the organic reagents are selectively adsorbed on the surface of the listed sulfide minerals and exert selective effect on adsorption of sulfhydryl collecting agent, which, in its turn, may result in efficient recovery of the minerals in the proper concentrates under complex gold ore flotation.

Under analysis is low efficiency of drum mills when dissociating higher strength aggregates of rebellious ore. It is shown that the main reason is insufficient destructive force. The structural-chemical characteristics of mineral aggregates and the role of defects in their dissociation are described. The author evaluates principles of estimating required energy input to dissociate aggregates composed of minerals with different types and values of interatomic and intermolecular bonds under high-power and high-velocity free impacts in disintegrators. By way of example, velocities of collision between minerals and disintegrator tools in dissociation of aggregates of sulfide and rare-metal ores and coal are given.