Ways to Reduce the Costs of Ventilating Mine Workings

B. M. Titov

In the report of the Central Committee of the Party to the Nineteenth Congress, Comrade G. M. Malenkov said: “The development of the national economy of the USSR is carried out at the expense of its own resources, at the expense of internal sources of accumulation. Therefore our Party has always devoted, and continues to devote, great attention to the struggle for the strictest regime of economy, as the most important condition for creating intra-economic accumulations and for the proper use of accumulated funds.”

One of the main sources of accumulation in the socialist economy is the systematic reduction of the cost of production. The reduction of the cost of production is achieved first of all on the basis of the broad introduction of new technology and, as a consequence, of the steady growth of labor productivity.

In carrying out the task set by Comrade Stalin—“…to surpass in the near future the achievements of science beyond the borders of our country,”¹—designers and scientists, in cooperation with workers of mines and plants of coal machine building, have created a number of entirely new high-performance machines and mechanisms.

Despite the great successes of Soviet mining machine building, which has outstripped the best achievements of foreign technology in the development of designs for electric and pneumatic fans for auxiliary ventilation (AVF), it must be emphasized that, from the economic point of view, due attention has still not been paid to the question of ventilating blind workings, although preparing new mines and horizons for operation is connected with the driving of a large number of development workings. For example, the plan for the development of the coal industry of the USSR in 1950 provided, in order to create the necessary line of stopes, for driving 5,740 km of mine workings and for obtaining from them 11.1% of the total coal production plan [1].

The costs of driving development workings account for a significant percentage of the cost of the mineral; thus, for example, in the coal industry the cost of driving one linear meter reaches 300 rubles, and each ton of coal obtained from development work is, on average, 25 rubles more expensive than that obtained from stopes [1].

One of the methods for reducing the cost of the mineral is to reduce the number of development workings per each 1,000 t of output and to reduce the specific expenditure of energy for ventilating them.

In order to reduce the volume and cost of development work, it is advisable, where mining technology permits, to abandon the driving of

of paired workings and for ventilating a single blind heading, VMPs should be used.

Abandonment of paired workings is possible if the length of the drift driven by a blind heading is brought up to the length of a Bremberg section or to the length of a pillar when mining a seam by paired longwalls.

Driving workings by a single blind heading is also dictated by considerations of fire safety, especially for seams highly prone to spontaneous combustion, since, according to statistics, most mine fires arise from spontaneous combustion of coal as a result of air leakage through the pillars left behind [2].

Under the Safety Rules [3] and the instructions on partial ventilation of development workings [4], [5], the use of auxiliary fans in gassy mines is essentially prohibited, and in non-gassy mines is permitted only in a very limited number of cases.

However, the practical requirements of everyday operation have changed these rules of technical operation (PTE), and the use of VMPs in driving development workings has become widespread.

At present, long development workings in non-gassy mines are successfully ventilated with the aid of high-pressure fans and rubberized fabric ducts of type M.

The driving of long workings by a single blind heading has radically changed the requirements imposed on the aerodynamic parameters of VMPs.

The new direction adopted by Giprouglemash in designing equipment for ventilating blind headings is characterized by “the use of high heads in partial-ventilation fans” [6; 19] and type M pipelines.

In accordance with this direction, Giprouglemash designed two-stage fans of the “Prokhodka” type with impeller diameters of 400, 500, and 600 mm, and discontinued production of the previously issued single-stage fans of types VM-1 and RVCh-5N.

In designing the “Prokhodka” fans, Giprouglemash proceeded from the assumption that a blind working 300–500 m long must be ventilated by a single fan.

For regulating the capacity of these powerful fans when used with short pipelines (workings), Giprouglemash proposes producing artificial air leakage through an opening in the pipeline near the fan. This “economical” method of regulation is based on the non-overload characteristic of the axial fan and permits a slight reduction in electricity consumption.

Without denying the expediency of regulating axial VMPs by leakage, we nevertheless believe that Giprouglemash’s orientation toward two-stage fans is unsuccessful, since it does not take into account the economic side of the question.

The driving of a working of any final length always begins with a few meters, and therefore the maximum fan head is required only at the end of ventilating the working.

The fan head, as is known, is always equal to the resistance of the ventilation pipeline, which depends on the quantity of air supplied, the length, diameter, and type of pipes used.

Without subjecting the theoretical aspect of ventilating blind workings to special consideration, let us compare the operation of a two-stage fan of the “Prokhodka-500-2M” type with that of a single-stage fan. The characteristic of the single-stage fan (Fig. 1) is obtained by reducing by half the head produced by the “Prokhodka-500-2M” and the power it consumes.

We shall take the final length of the development working as 300 m, and the rate of advance of the face in coal as 150 linear m per month.

When a two-stage fan operates on a type M pipeline with a diameter of 500 mm and a length of 300 m (Fig. 1), the quantity of air delivered to the face is:

\[ Q_{\text{face}} = Q_v \cdot p = 180 \cdot 0.83 = 150\ \text{m}^3/\text{min}, \]

where \(Q_v\) is the fan capacity, \(\text{m}^3/\text{min}\);
\(p\) is the delivery coefficient, according to Fig. 1.

Let us assume that precisely this quantity of air is required for ventilating the blind working.

Fig. 1. Characteristics of rubberized type M pipelines and fans.

1 — “Prokhodka—500-2M” fan;
2 — single-stage fan.

When a single-stage fan operates on a type M pipeline with a diameter of 500 mm, but with a length of 150 m, the air reaching the face will be:

\[ Q_{\text{face}} = Q_v \cdot p = 175 \cdot 0.9 = 157\ \text{m}^3/\text{min}. \]

Consequently, when ventilating this working with single-stage fans, the second fan will have to be connected in series with the first only after 150 linear m of the working have been driven, or, at the adopted rate of face advance, after one month. Thus, by using single-stage fans, the total consumption of electric power associated with ventilating the entire working can be reduced by 25%, or in absolute terms by

\[ W = \frac{(N_2 - N_1)\,T}{L} = \frac{(8.2 - 4.1)\cdot 24 \cdot 30}{300} = 9.8\ \frac{\text{kWh}}{\text{linear m}}, \]

where \(N_2, N_1\) are the powers consumed by the fan motors (Fig. 1), kW;
\(T\) is the operating time of the single-stage fan before a second single-stage fan is connected to it in series, hours;
\(L\) is the total length of the working, linear m.

When workings of shorter length are ventilated by a two-stage fan, the specific overconsumption of energy increases in inverse proportion to the maximum length of the working.

The overconsumption of energy obtained, insignificant at first glance, amounts to a considerable sum for the coal industry as a whole, if one takes into account that the length of preparatory workings driven annually is measured in thousands of kilometers. In addition, it should be noted that the specific energy consumption increases in inverse proportion to the rate of advance of the blind heading.

Regulation of capacity by other methods can be carried out with equal success both for two-stage and single-stage fans; therefore, in comparing the specific consumption of electric power, it is not taken into account by us.

The percentage ratio among the various preparatory workings depends on the mining systems used, on the methods of driving the workings, and changes as these change. Docent A. V. Vol'kenau gives [2, 12] the following ratio among preparatory workings (local ventilation fans), Table 1.

Table 1

Workings more than 300–400 m long are encountered rather rarely, and therefore are not included in the table.

Thus, for ventilating more than 50% of preparatory workings, two-stage fans are not required at all, since the length of their ventilation pipelines does not exceed 75 m.

Taking the foregoing into account, it must be supposed that it is more expedient to replace two-stage local ventilation fans with single-stage ones designed for ventilating workings 75–100 m long. The structural design of these single-stage fan sections should permit their direct sequential connection into a block (without additional branch pipes) for ventilating workings of greater length. The inlet coupling to the motor of the fan section should be placed outside the casing and made through-flow, so that fans connected in series (arranged side by side) can be switched on from one starter and interlocked with the face electric mechanisms.

Single-stage fan sections make it possible to use them for ventilating long workings both with canvas and metal pipelines. With canvas pipes of type M, single-stage fans, when connected in series, should be installed side by side at the beginning of the pipeline; with metal pipes, they should be installed at a distance from one another in order to reduce air leakage at the joints of the pipeline.

The sequential operation of two or more fans installed in a row on the intake air stream must be regarded as the operation of a single fan and should be permitted even in mines hazardous for gas and dust. The installation of a second fan (when metal pipes are used) inside a blind working in gassy mines may be permitted only if it has a pneumatic drive.

When pneumatic auxiliary ventilation fans are used in gassy mines, the driving of long workings by a single blind face should be permitted. It seems to us that the question of whether to drive a working by single or paired faces must be decided on the basis of the purpose of the working and the technical-and-economic indicators of its driving.

In the technical-and-economic calculation it is necessary to take into account, in addition to the expenditure of energy for ventilation, the rates of driving the working, the danger of spontaneous combustion of coal, and the additional costs of driving and maintaining a parallel working.

The advisability of ventilating blind workings by auxiliary ventilation fans is also confirmed by the results of the investigations of Engineer Pertsev [7], according to whose data, when crosscuts were ventilated by fans through pipes, a considerably larger quantity of air reached the face than when ventilation was carried out through breakthroughs, although the latter, in order to combat leakage through the stoppings, were constantly plastered with clay. When local-ventilation fans were used, the cost of 1 m³ of air delivered to the face, according to Engineer Pertsev’s data, was 60% cheaper than when ventilating through breakthroughs.

When single-stage sectional fans with impeller diameters of 300, 400, 500, 600, and 800 mm are used, it will always be possible to assemble a fan with such pressure and capacity as are necessary for the economical ventilation of workings of any cross section, both short and long.

Local-ventilation fans must operate in two modes: normal and forced, for rapid ventilation of the working after blasting the boreholes. The fan has to be selected for the forced mode, although it is required for only 20–30 min per shift, or 1.5–2.0 hours per day. Consequently, the second source for reducing the expenditure of energy on ventilating workings is the creation of adjustable single-stage local-ventilation fans.

Regulation of the operating mode of an axial auxiliary ventilation fan with an electric drive is most expediently and structurally possible by simultaneous turning of all the blades of the guide apparatus.

A fairly simple, yet at the same time reliable, design of a mechanism for turning the blades of the guide apparatus was developed by P. M. Emel’yanov, a student of the higher engineering courses.

For supercategory mines, pneumatic sectional fans should be developed with regulation of the operating mode by changing the quantity (and not the pressure) of the compressed air supplied to the motor.

This method of regulation has already been applied and has proved itself well in the modernized VP-4M fan, which was developed by TEMZ jointly with the Department of Mining Mechanics of the Tomsk Polytechnic Institute named after S. M. Kirov.

The aerodynamic parameters of sectional fans, when they are designed, should be chosen so that they ensure reliable ventilation of workings of the corresponding cross section driven by paired faces, i.e., so that they deliver to the face the required quantity of air through a pipeline 75–100 m long. In workings of greater length, they should be connected in series into a block.

Increasing the efficiency of local ventilation fans also helps reduce energy consumption, but, given the continuously changing equivalent opening of the network, it is not the principal determining factor.

By comprehensively mobilizing the internal reserves of production, we shall be able more rapidly to accomplish the tasks set before the mining industry by the fifth five-year plan for the development of the USSR for 1951–1955.

Conclusions

1. Certain paragraphs of the rules for technical operation and safety must be revised in order to bring them into conformity with the wide use of LVFs for ventilating blind workings in mines.

2. In deciding how to drive a working—with a single face or with paired faces—as a rule, one must proceed from its purpose and from the technical and economic indicators of driving the working.

3. Instead of two-stage LVFs, it is most expedient to design and manufacture single-stage fan sections with regulation of the operating mode and with impeller diameters of 300, 400, 500, 600, and 800 mm.

4. The aerodynamic parameters of fan sections should be selected so that they ensure reliable ventilation of workings driven with paired faces, taking into account the size and type of ducting used.

Literature

1. Valentinov A. M. For a further reduction in the cost of coal. Ugol’, No. 6, 1951.

2. Ventilation of blind workings. Ugletekhizdat, Moscow, 1949.

3. Safety rules in coal and shale mines. Ugletekhizdat, 1951.

4. Instruction on partial ventilation of preparatory workings. Ugletekhizdat, Moscow, 1948.

5. Ventilation of hard-coal mines. MakNII. Ugletekhizdat, Moscow–Leningrad, 1951.

6. Klornkyan S. Kh. and Levi G. M. New equipment for ventilating blind faces. Journal Ugol’, No. 5, 1951.

7. Protsenko V. P. Ventilation of rising workings in the mining industry. Journal Bezopasnost’ truda v gornoi promyshlennosti, No. 8, 1936.

1. I. Stalin, Speeches at Pre-Election Meetings of Voters of the Stalin Electoral District of Moscow on December 11, 1937 and February 9, 1946. Gospolitizdat, p. 22, 1953. ↩