Vol 47 Iss. 1

In mining practice, pipeline transportation of liquids and gases is becoming increasingly widely used. When calculating complex air piping networks, as well as pipelines for hydraulic coal mining, it is of great importance to ensure a specified pressure at the consumers. The technical performance of the machines and the economic efficiency of the entire installation depend on this.

Three-link screw mechanisms converting translational motion into rotational motion are widespread due to their compact design. They are used in pneumatic drilling hammers and perforators, the annual production of which for the mining and construction industry only in our country counts hundreds of thousands of units. Development of the national economy puts forward the tasks of increasing the productivity of this equipment and increasing the efficiency of the perforator mechanisms.

A pneumatic percussion machine is a piston heat engine in which the potential energy of the working fluid (compressed air) is cyclically converted into the kinetic energy of the piston. The piston (striker) of this machine moves reciprocatingly under the action of compressed air pressure alternately supplied to the cylinder cavities by a special air distribution device. The kinetic energy of the piston is transferred to the working tool (drill, pick, chisel, etc.) upon their impact at the end of each cycle. Therefore, when studying the working processes of pneumatic percussion machines, one should choose a method that reflects both the nature of the thermodynamic processes occurring over time in the cylinder cavities and the nature of the piston motion. This leads to the necessity of jointly solving the system of differential equations of the energy balance of open thermodynamic systems in the cylinder cavities and the equation of motion of the piston.

A number of difficulties arise in the theoretical study of working processes of pneumatic impact machines. The complex character of thermodynamic processes occurring in the cylinder of a pneumatic machine necessitates the introduction of simplifying schematization. On the other hand, the approximate mathematical methods used to solve the system of differential equations of the working process of these machines introduce additional errors in the final result of the study. Moreover, it is impossible to separately assess these errors and prove or disprove the correctness of the adopted schematization of physical phenomena.

Pneumatic motors are used only in the mining industry and, despite this relatively narrow area, in their production there is an economically unfavorable multiplicity of models with the same operating parameters, but different sizes of the active part (rotors, pistons). For example, G. I. Petrovsky plant (Donetsk SNH) serially produces gear pneumatic motors type BSH2-1-5 and PSH-7A with the same operating characteristics (pressure 3.5 kg/cm², power 7 hp, compressed air flow rate 6.8–7 m³/min), but different sizes of rotors: the first has a rotor width of 150 mm and center-to-center distance of 100 and 75 mm, the second respectively 120 and 145.3 mm. Darasun plant (Chita SNH) and the Communist Plant (Krivoy Rog) serially produce piston engines DR-10 and MP-5, also identical in operating characteristics (5 kg/cm²; 10 hp; 10 m³/min). But the diameter and stroke of the pistons in the DR-10 engine are 101×62 mm, and MP-5 100×80 mm. These are not isolated examples.

Currently, the main types of traction elements of conveyors and elevators are chains and rubberized belts. The use of a rope traction element is limited by the lack of a convenient design for attaching the working element (scrapers, plates, buckets) to the rope. The existing types of attachment require pitch adjustment when the rope stretches and special devices for passing couplings over the drive pulley. The fastening of these devices must be systematically controlled, since tightening is done with bolts. However, the rope traction element has a number of advantages compared to the chain one: weight is 6–8 times lower, lower cost, greater operational reliability and strength. At the same time, the design of pulleys, especially drive pulleys, is complex and therefore relatively unreliable in operation. Pulleys for ropes with clamping couplings have a number of significant disadvantages and are used to a limited extent in industry.

In accordance with the current safety regulations, the braking torque for service and safety braking must be at least three times the static torque for lifting or lowering the design load. At the same time, the deceleration of the system during safety braking must be no less than 1.5 m/sec² when the design load is lowered and no more than 5 m/sec² when it is lifted. The last requirement is imposed by the Safety Rules on systems with drum hoisting machines, but nowadays such norms are adhered to for friction pulleys as well (MacNII, plant named after XV-anniversary of LKSMU and others).

With the use of multi-rope hoisting systems with friction pulleys, there is a need for new materials suitable for lining the grooves of rope driving pulleys of hoisting machines. The most common lining materials – wood (oak) and rubber-fabric conveyor belt – have insufficient coefficient of adhesion with steel rope (respectively 0.17 and 0.25) with unsatisfactory service life (3‑5 months). The coefficient of adhesion of lining materials with steel wire rope should not be lower than 0.3 and should not decrease when the rope is wetted; allowable specific pressure on the lining should not be lower than 25 kg/cm²; service life of lining – at least 5 years; lining should not wear out the ropes and catch fire during prolonged slippage of ropes and should be elastic enough.

As is known, the complex mechanism of unsubmerged jets is not sufficiently studied and the results of the corresponding experimental studies are still poorly amenable to hydromechanical interpretation. Under these conditions, the need for practical calculations has led to the necessity of studies designed to develop empirical formulas with a narrowly limited, specific area of application. Such an approach to the study of jets, when used in advance without a sufficiently rigorous hydromechanical justification of the patterns obtained from experiments, can only conditionally be considered correct.

In modern practice of hydrotransport of ore, concentrate and tailings slurries the most common are centrifugal sand pumps and dredgers with open or closed impellers. As is known, in this type of pump, the entire flow passes through the impeller and the head is increased by the operation of centrifugal forces.

In order to maximize energy savings and reduce capital costs of dewatering, the nominal parameters of mine pumps (capacity, head and speed) should be selected to provide maximum effect over the entire range of possible capacities and heads. Large-scale pump production and cost reduction are possible with a minimum number of pump sizes.

The heating surface is the most important technical parameter of a mine calorifier plant. Analysis of the heating surface area of this surface is made on a large body of project data of mine calorifier plants of various Giproshakht institutes (Mosbaosgiproshaht, Lengiproshaht, Donetskgiproshaht, Uralgiproshaht, etc.). As a specific criterion of comparison, taking into account the numerous factors influencing the size of the required heating surface, it is advisable to consider the technical indicator of mine calorifier plants. Let's call it specific heating surface, i.e. the number of square meters of the heating surface of the mine calorifier plant, per 1000 kcal of heat transferred to the air per hour.

In the design and operation of mine heater installations, the amount of electricity consumed and the installed power of the fan drive are of great importance. Let us analyze these data using the example of several Giproshakht institutes.

The theorem on differential inequalities of S. A. Chaplygin and its further generalizations give the possibility of evaluating the unknown solution of a differential equation by two comparison functions from above and below. This method is very effective for approximate determination of the motion trajectory of electromechanical systems or for estimation of additional motion caused by deviation of actual values of the system parameters from the calculated ones. However, the widespread use of methods based on the theorem of S. A. Chaplygin is hindered by difficulties in determining its limits of applicability.

In the mechanisms of percussive-rotary drilling (pneumatic and hydro-impactors, etc.) energy transfer for rock destruction is carried out from the piston-impactor or directly to the rock-destroying tip - bit, or through an intermediate link - drill rod, drill pipe - drill bit.