On R. N. Khadzhikov’s Book Mining Mechanics

B. M. TITOV, V. S. UDUT

(Presented by the scientific seminar of the Department of Mining Mechanics)

R. N. Khadzhikov’s book Mining Mechanics (Ugletekhizdat, 1956, 32 printed sheets, print run 25,000 copies) has been approved by the Administration of Educational Institutions of the Ministry of the Coal Industry of the USSR as a textbook for mining technical schools. In comparison with the two previous editions, the book has undergone a fundamental revision. Its volume has been considerably reduced by excluding descriptions of machines of obsolete design, certain secondary theoretical questions, and numerical examples, since special problem books on mining mechanics have recently been published. The structure of the book and the presentation of the material are more successful. Many questions are set out more fully than in the previous editions. For example, the description of automation schemes for fan, pumping, compressor, and hoisting installations, material on parachutes, reducers, etc. On the whole, the book is written at a sufficiently high theoretical and technical level and reflects the advances achieved by the domestic mining industry. The material is presented clearly. All sections of the course are illustrated with techno-economic calculations, which significantly facilitates the assimilation of the material.

However, despite the positive qualities of the textbook, it also has shortcomings. For example, in presenting the laws of proportionality of turbomachines (p. 32), no instructions are given on how to use them when there is static resistance in the network, i.e., when the network characteristic does not coincide with the proportionality curve.

The parallel operation of pumps is considered without taking into account the operation of the suction and discharge valves, and therefore it is incorrectly stated (p. 156) that the delivery of one of two pumps connected in parallel may be negative.

Of the various possible schemes for priming pumps, only one is given—with an accumulator tank (p. 179), which, as is known, is not entirely successful, since it reduces the useful suction head and somewhat increases the dimensions of the pump chamber.

The scheme for laying pipe strings shown in Fig. 102 does not permit the use of an overhead crane. The use, instead of a crane, of a turntable, a rail track, and six transverse beams with hoisting tackle is technically and economically inexpedient. This typical scheme of a pump chamber has become obsolete and has long been rejected by operating practice, but for some reason it is still reproduced in all textbooks as

standard solution. Both pipe strings should be laid on one side of the pump chamber and a movable crane beam should be used.

In the description of turbocompressors, not a single actual aerodynamic characteristic of a compressor is given, while the characteristic of the air pipeline is, for some reason, shown as passing through the origin (Fig. 130). This is incorrect, since in a mine pneumatic network there is always a static resistance in the form of the pressure of compressed air before the face mechanisms, and it never passes through the origin.

All the errors indicated above are systematic and occur in books by other authors.

In some cases the reduction in the size of the book has been achieved at the expense of the quality of the presentation of the material. For example, in considering the brakes of hoisting machines, nothing is said about the presence and purpose of locking devices, the characteristics, methods of adjustment, and requirements of the PB imposed on brakes. The method for calculating metallic rheostats of asynchronous motors should have been presented in the textbook, and not in the Collection of Examples and Problems in Mining Mechanics.

In determining the numerical value of the coefficient

\[ \lambda=\frac{1}{\kappa_k}, \]

an error was made in formula (174′), since the adopted value of this coefficient, 0.78, corresponds to a bar of steel with a specific weight of \(0.0078\ \text{kg}/\text{cm}^3\), and not to the fictitious specific weight of a rope, \(0.0098\text{—}0.0092\ \text{kg}/\text{cm}^3\).

In formula (175), the adopted dimension of the temporary resistance to wire rupture \((\text{kg}/\text{cm}^2)\) does not correspond to GOST.

In formula (183), the friction coils are not divided by the number of layers.

The method given in the book for determining the power of the electric motor of a hoisting machine is not fully justified, since it does not reveal the relation between the equivalent torque (force) and the heating of the motor, and does not indicate how to operate with negative forces. It should have been indicated that, with electric braking of the motor, negative forces are introduced under the radical of the equation for the equivalent force, whereas with mechanical braking they are not. The nominal power of the motor of a hoisting machine is always greater than the equivalent power, and therefore only the finally selected specific electric motor needs to be checked for overload.

The automation control scheme for a hoisting machine with an asynchronous drive described in the book is practically not used; therefore it would have been better to give a description of the automation scheme with relay-pulse final positioning of the conveyances, which is simpler and has been successfully used since 1954 (M. N. Vasilevskii, “On the question of automating hoisting with an asynchronous drive,” Ugol’, 1955, No. 11).

Among the more minor shortcomings, the following may be noted.

It would not have been necessary to introduce (p. 26) the concepts of the equivalent orifice and the like for the pipeline of a pumping installation, since they are practically not used.

The design of the VM-200 fan shown in Fig. 29 is distorted, since in reality the fan blades are not overlapped by the front fairing and the bushing of the straightening apparatus.

In the description of the design of the piston pump (Fig. 82), the devices for removing air from the cap on the suction side and for filling the cap with air from the discharge side of the pump are not indicated.

The chapter “Switching Circuits of Hoisting Installations” would more properly have been called “Control Circuits of Hoisting Installations.”

Questions of overhaul and testing of fans, pumps, compressors, and hoisting machines, in order to avoid repetition, should have been excluded from the theoretical course and given only in practical work.

The book has not been edited to the proper extent and contains a number of minor misprints (pp. 305, 321, 340, 375, 393, and 406).

Despite the shortcomings noted, the book under review can be used not only by students of mining technical schools, but also by students of mining higher educational institutions in operational specialties.

In a subsequent edition, for the further improvement of the book, it is necessary to provide a description of the design of self-sealing ventilation doors, water-separators, automatic condensation pots, schemes for laying main pneumatic pipelines with a counter-slope of the haulage working, characteristic drainage defects, the advantages of a scheme with sequential connection of circulation pipelines ahead of the parallel one, and the calculation and structural design of foundations.