Two Possible Principles for Automating Mine Fan Installations and the Layout of the Automation Scheme

G. P. Ksyonin

Docent, Candidate of Technical Sciences

Two possible principles for automating mine fan installations

We have previously expressed the opinion that the best means of ensuring reliable and, at the same time, economical ventilation of mines is the automation of fan installations¹. Speaking of the automation of fan installations, we previously had in mind only such automation in which, despite the change over time in the equivalent opening of the mine, the output of the fan installation is maintained strictly constant. The principle of automating fan installations in which the output is maintained constant could be called the principle of “constant delivery.”

The amplitude of variation of the value of the equivalent opening of the mine

\[ \lambda_{\max}=\frac{A_{\max}}{A_{\min}}, \]

which depends on operating conditions, in practice is never equal to 1 and not infrequently reaches the value 3.5 (usually \(1.2<\lambda_{\max}<1.7\)²). According to data of the brigade of Acad. A. A. Skochinsky³, solely as a result of changes in natural draft, the depression of a mine may vary by up to 45%. Consequently, solely due to natural draft, the change in the value of the equivalent opening of the mine may reach 20% (\(\sqrt{1.45}\simeq 1.2\)).

It is known that the so-called coefficient of relative opening \(\varphi\) is directly proportional to the value of the equivalent opening of the mine (of course, if the type and diameter of the fan runner—\(D_2\)—are specified). It is also known that the dependence between the delivery coefficient \(\delta\), on the one hand, and \(\varphi\), on the other (within the limits in which one may speak of using a fan of the given type and size), is almost linear. Finally, according to Rateau’s second law, the output of a fan \(Q\) (at constant peripheral speed of the runner \(u_2\)) is directly proportional to \(\delta\):

\[ Q=k\delta u_2\left(\frac{D_2}{2}\right)^2. \]

Thus, it may be considered that, when the value of the equivalent opening \(A\) changes, the output of the fan \(Q\) changes, roughly speaking, in proportion to \(A\). As follows from the equation

\[ P=\frac{0.38^2\cdot Q^3}{A^2\cdot 102\cdot \eta}, \]

the power at the fan shaft, in this case, if the change in its efficiency is neglected, varies in proportion to the first power of the fan capacity (not the third, since \(A\) varies in proportion to \(Q\)). It now becomes obvious how significantly the energy consumption by the fan changes in connection with a change in the equivalent orifice of the mine. It must be said that the possibility of a change in the equivalent orifice of the mine and of the related reduction in fan capacity is always taken into account in design. Usually, bearing in mind the practical difficulty of regulating the capacity of mine fan installations, the parameters of the fan installation are chosen so that the capacity of the ventilation installation prescribed by the “Safety Rules” is ensured under the most unfavorable conditions (i.e., with the minimum equivalent orifice). Thus, practically throughout the entire period of operation the fan works with excess capacity and with a considerable overconsumption of energy (by 100% and more). Even with stepwise regulation of the speed of a centrifugal fan—and this case, given the present state of mine ventilation installations, is the ideal one—the overconsumption of energy, owing to the reasons indicated above, is entirely unavoidable and must be no less than 10–15%. It is very difficult to judge how great in practice (on the scale of entire basins) the above-indicated overconsumption of energy is, since the operating conditions of ventilation installations are extremely varied, and there are almost no statistical data on the question of interest to us. Nevertheless, the individual figures available to us fully confirm the assumptions stated above. Thus, according to data of the Donetsk Mining-Technical Inspectorate of the NKTP, the total calculated capacity of all ventilation installations in the Donbas in 1937, referred to \(1\) t of average planned daily output, was \(2.75\ m^3/\min\) ⁴), whereas according to the “Safety Rules,” even for mines of category III with respect to gas (of which there are not so very many), it would have been necessary to supply (according to the 1937 standards) only \(1.5\ m^3/\min\) per ton of average daily output. It is obvious that here there was a definite overconsumption of energy, which must have been no less than 80%.

From what has been said it is clear what benefit can be provided by automation of mine fan installations even if one is guided only by maintaining the flow rate established in accordance with the “Safety Rules” (the principle of “constant flow rate”). However, another principle may also be made the basis for the automation of mine fan installations, one which could be called the principle of the “required flow rate” (as distinct from the previously considered principle of “constant flow rate”).

The capacity of the ventilation installations of coal mines which, with respect to gas, are assigned to the “supercategory,” according to the “Safety Rules,” is established on the assumption that the percentage of methane in the total outgoing stream should not exceed 0.75% by volume. In a similar way the capacity of non-gassy (in the usual sense) mines is established where the emission of carbon dioxide exceeds \(15\ m^3\) per \(1\) t of average daily output. In the latter case, as is known, the fan capacity must be such that the carbon dioxide content in the total outgoing stream does not exceed 0.75% (also by volume). It goes without saying that the ventilation installations of mines classified with respect to gas as “supercategory” and of mines with large emissions of carbon dioxide cannot be automa-

⁴) Prof. Dr. K. A. Ushakov, Prof. V. I. Polikovskii, Eng. M. I. Nevelson, Assoc. Prof. M. P. Tatarinov.—Mine Ventilation Installations. IONTI NKTP USSR, 1938, p. 13.

...be designed according to the principle of “constant flow rate,” since the release of $\mathrm{CH}_4$ or $\mathrm{CO}_2$ changes over time and, consequently, the required flow rate also changes.

In the first of the cases under consideration, the regulator of an automatically operating fan installation must respond to changes in the equivalent opening of the mine, and its task is to maintain constant output. In the second case, the regulator must respond to changes in the content of $\mathrm{CH}_4$ (or $\mathrm{CO}_2$) in the common outgoing stream, and its task is to change the output of the ventilation installation in such a way that the content of the indicated gases in the common outgoing stream remains constant. Automation of mine fan installations according to the first principle would be a significant step forward in the field of mine ventilation. However, automation according to the second principle—according to the principle of “required flow rate”—is the cardinal solution to the problem, quite apart from the fact that for certain categories of mines, as indicated above, it will also be the only solution to the problem. In fact, when a fan is regulated according to the principle of constant flow rate, the once-established output will be provided regardless of the magnitude of the mine’s equivalent opening, but it may always turn out that at particular moments it will not correspond to the magnitude of gas emission. According to the “Safety Rules” for nongassy mines, with carbon-dioxide emission of less than $15\ \mathrm{m}^3$ per ton of average daily output, as well as for mines assigned, with respect to gas, to categories I, II, or III, the latter is not required. But at particular moments this discrepancy will mean a certain overexpenditure of electric power. If automatic fan installations operating according to the principle of “required flow rate” are ever introduced into production and prove themselves in practice, then the “Safety Rules,” in the part concerning the norms for supplying fresh air to mines of various gas categories, could be revised. Automation of fan installations according to the principle of “constant flow rate,” as indicated above, is already a major step forward and, in addition, this variant will be technically the simplest and therefore will probably prove the most acceptable for small ventilation installations. We therefore consider it necessary in what follows to examine both possible principles of automation of mine fan installations, despite the greater technical perfection of the second of the variants under consideration, that is, automation according to the principle of “required flow rate.”

When considering the question of automation of mine fan installations, we shall be interested first of all in the question of the “sensor” (transmitter) of the regulator. It goes without saying that, depending on which principle is laid down as the basis for automating the fan installation, the principles of construction of the “sensors” also change. In installations regulated according to the principle of “constant flow rate,” the sensor must be one or another instrument that perceives changes in the dynamic effect of the flow. In installations regulated according to the principle of “required flow rate,” the sensor, as can be seen from what has been set forth above, must be a gas analyzer of one design or another. Instruments of both types, in a large number of variants, find application in the most diverse fields of technology. In the present article we set ourselves the task of establishing to what extent the existing instruments can be used for the purposes of automating mine fan installations and what changes will be required in their design. Of course, instruments pertaining to installations regulated according to the principle of “constant flow rate,” and instruments pertaining to installations regulated according to the principle of “required flow rate,” must be considered separately.

Sensors of Regulators of the Output of Mine Ventilator Installations Based on the “Constant Flow Rate” Principle

The task of the sensor of a regulator operating on the “constant flow rate” principle, as was explained above, is to monitor the output of the ventilator installation, responding to its changes. Since the output \(Q\) can be expressed through the air velocity \(C\) and the cross-sectional area of the ventilation duct \(F\), the sensors of regulators of the type under consideration may be all instruments by means of which the velocity of the air stream is measured \((Q = F \cdot C)\). The following instruments for measuring air velocity are known: 1) mechanical anemometers, 2) thermoelectric anemometers, 3) throttling devices (orifice plates, nozzles, throttle grids), 4) pneumometric tubes (Pitot, Prandtl, Venturi tubes, etc.).

Of the various types of mechanical anemometers, as sensors of regulators for the variant of automation of ventilator installations considered by us, only those among them could be used which indicate velocity directly. Such anemometers include: a) centrifugal anemometers (an anemometer connected to a tachometer), b) electric anemometers (anemometers with electrical transmission from the wheel to the velocity indicator). From anemometers of the first type, if desired, sufficient forces can be obtained to produce a regulating action, but in this case the transmission from the sensor to the actuating mechanism of the regulator cannot be made sufficiently simple (the sensor must be placed in the suction duct of the ventilator, and the actuating mechanism in the machine room). Electric anemometers, in which the anemometer wheel is connected to a dynamo, and the velocity indicator is made in the form of a voltmeter, make it very simple to transmit from the sensor to the actuating mechanism. There is likewise no need here to doubt the magnitude of the forces, since everything will depend on the size of the anemometer wheel, which is, in essence, a wind motor. A drawback of anemometers as sensors of output regulators of ventilator installations is the presence in them of rotating parts. Being installed in the suction duct, in a stream of moist mine air containing much dust, sensors of this kind will not operate reliably⁴.

Thermoelectric anemometers, based on measuring the loss of heat by a heated wire placed in an air stream, could be used as sensors of output regulators only in non-gassy mines, since the burning out of the anemometer wire (which is always possible) in a gassy mine may cause an explosion. The readings of thermoelectric anemometers depend, as is known, on the temperature of the air. Since the temperature of mine air does not remain constant (although it does not vary very greatly), there can be no question of accurate regulation when thermoelectric anemometers are used as sensors.

The use of throttling instruments (diaphragms, nozzles, Venturi tubes) is, as is known, the most accurate and reliable method of measuring output, but this method, when applied to mine ventilator installations, would be very expensive, since its use reduces the energy reserve of the entire flow.

Since the pressure developed by mine ventilators is relatively small and usually lies within the limits from 40 to 200 mm water column, and for

in order to be able to make use, for regulation purposes, of the pressure drop obtained with the aid of throttling devices, this drop must be at least several tens of millimeters of water column⁶); it is clear, therefore, that the energy losses here will be relatively very large.

Usually, in mine fan installations, pneumometric tubes (Brabbée, Pitot-Prandtl, etc.) are used for control purposes. For regulation purposes these instruments can also be used successfully, but in order to obtain the proper sensitivity of the regulator it will be necessary here to resort to amplification of the dynamic effect of the flow, since at an air velocity in the suction duct of about 10–12 m/sec the dynamic head will be only 6–9 mm water column. Since we have already abandoned the use of throttling devices (such as plates and nozzles), there remains only one way to increase the sensitivity of the regulator—the use of a Rateau multiplier. As is known, the amplification coefficient of a multiplier consisting of three Venturi tubes, such as that shown in Fig. 1, can be brought in practice up to 25–75⁷), that is, with the aid of this instrument it is quite possible to obtain a sufficiently high sensitivity of the regulator.

Fig. 1

In automatic fan installations operating on the “constant delivery” principle, the best type of sensor is the Rateau multiplier, which, having no rotating parts and being exceptionally simple in design, ensures reliable, sufficiently accurate, and economical regulation.

Sensors of capacity regulators for mine fan installations based on the “required delivery” principle

Regulation of mine fan installations according to the “required delivery” principle, as could be seen from what was said above, must essentially be based on gas analysis. In the practice of chemical analysis the following methods of gas analysis are used: a) by liquefying gases through cooling them and subsequent fractionation; b) by successive chemical absorption of the individual constituent parts of a gas mixture and measurement of the total volume of the mixture as a result of such absorption; c) by combustion with explosion of the ingredients of the gas mixture after adding definite volumes of oxygen (or hydrogen) to the mixture; d) by measuring the refractive index of the gas mixture and comparing it with the refractive index of a gas mixture of previously known composition; e) by measuring the electrical resistance of a platinum wire stretched in a chamber with one gas or another, or with a mixture of gases, which varies depending on the greater or lesser transfer by the wire of Joule heat to the gas surrounding it⁸). In technology, for continuous gas analysis (for example, for purposes of controlling boiler installations), of the gas-analysis methods listed above, by quite

⁶) The lost head even for Venturi tubes amounts to as much as 20% of the pressure drop obtained.

⁷) Prof. V. I. Polikovskii—Fans, blowers and compressors. ONTI Publishing House, 1933, p. 324.

⁸) Technical Encyclopedia, vol. I, 1928 edition (B. M. Berkengeim).

for understandable reasons, only the method of sequential absorption (Ayos, Eckardt PMSH gas analyzers, etc.) and the method of measuring the electrical resistance of a platinum wire placed in a mixture of gases (Siemens, Pirometer, Brown gas analyzers, etc.) found application. In addition to these methods, methods based on the use of the difference in the specific weights of gases (Krell, Schulze-Dosha, Ranarex gas analyzers) and methods based on the difference in gas densities (Unograph gas analyzer) were also used in engineering.

The operating experience of continuously acting gas analyzers used for monitoring boiler installations, and the conduct of scientific research in this field, have shown that, of all existing types of gas analyzers, the most sensitive and cheapest to operate are electrical gas analyzers, i.e., those based on the principle of measuring the resistance of a platinum wire placed in a mixture of gases⁵. The action of the Siemens gas analyzer is based on the fact that the thermal conductivity of gases depends on their chemical composition. As an instrument taking into account the difference in the thermal conductivities of different gases, Siemens used the Wheatstone bridge. The moment that disturbs the electrical equilibrium in the Siemens instrument is the unequal heating of two platinum wires placed in media of different chemical composition; the indicating instrument is a galvanometer. The principle of operation of the Siemens gas analyzer can be understood from Fig. 2.

Fig. 2

The advantages of electrical gas analyzers, if we speak of using them as sensors for regulators of mine fan installations, are obvious in comparison with other types of gas analyzers. Quite apart from their greater simplicity in comparison with other types of gas analyzers, electrical gas analyzers make it possible simply to connect them (electrically) with the actuating mechanisms of the regulator and, most importantly, provide the greatest accuracy. True, the accuracy provided by electrical gas analyzers in their usual design, ±0.5%, is not quite sufficient for our purposes. In our case the regulator must begin to act when the content of CH₄ (or CO₂) in the outgoing stream increases above 0.75%, which lies at the limit of accuracy of these instruments (at least for CO₂). In modern designs of electrical gas analyzers, the causes on which the accuracy of their readings depends are, in essence: 1) uneven suction of air by the ejector due to fluctuations of water pressure in the water supply system, 2) instability of the current in the branches of the bridge, and 3) inaccuracy of zero setting. The listed shortcomings of electrical gas analyzers are not organic shortcomings—

statics and can be eliminated in new designs. Thus, the ejector can be replaced by a centrifugal fan; constancy of the current strength in the branches of the bridge can be achieved by using kenotrons; and, finally, setting to zero cannot present any particular difficulties at all. It is also possible to increase considerably the accuracy of the readings of the electric gas analyzer if an electron tube is connected between the branches of the bridge, as an amplifier, according to the circuit shown in Fig. 3. In practice, electric gas analyzers of the type we are considering have found application as instruments for determining CO₂ and CO + H₂ in flue gases. Thus, there is no reason to doubt the possibility

Fig. 3

of applying them in the present case as well for determining CO₂. As for the use of instruments of this kind for detecting CH₄, in principle there is no difference in whether CO and H₂ or CH₄ are to be determined, since all these gases will burn equally on the heated platinum filament and, by raising its temperature, will create a difference of resistances in the branches of the bridge. (Recently, on this principle, so-called “methane relays”—instruments for detecting methane—have already been constructed.) Very great accuracy can evidently be obtained from gas analyzers of this kind by using thallium-sulfide photocells, which have especially high sensitivity to infrared rays. In this case the increase in the temperature of the platinum wire is registered by the photocell¹⁰).

Connection of the sensors with the actuating mechanisms

The type of sensor, depending on the principle adopted for automating the mine fan installation, will to a certain extent also determine the method of connecting the sensor with the actuating mechanism. A regulator operating on the principle of “constant flow rate,” as the connecting link between the sensor—which in this case, as established above, must be a multiplier—and the actuating mechanism, must necessarily have a device that measures the dynamic effect of the flow rate and produces the regulating impulse. Instruments of this kind may be divided into three groups: 1) float volumeters (draft meters, steam meters),

¹⁰) Acad. A. F. Ioffe. Semiconductors.—Journal Tekhnika molodezhi No. 8–9, 1940, p. 11.

2) membrane differential manometers and 3) U-shaped manometers with mercury filling and soldered-in contacts.

Of all these types of flowmeters, float instruments have become the most widespread and are manufactured in a large number of variants (Fuss and Debro volumeters, Dosh differential draft gauges, instruments of the Tizpribor plant, “Heat and Power,” Siemens steam meters, etc.). The simplest instrument of this type is shown in Fig. 4. The forces that can be obtained from such an instrument will, of course, be insufficient for direct action on the actuating mechanism of the regulator; however, with proper float dimensions they will be sufficient for shifting the spool of a servomotor or for closing and opening the electrical circuits of the control scheme.

Fig. 4

The wide use of float volumeters in engineering guarantees the possibility of using them also for automatic regulation of mine fan installations.

Membrane differential manometers are not as reliable as float instruments. The principle of operation of a membrane differential manometer can be understood from Fig. 5, which shows the use of such an instrument for purposes of regulating a steam-turbocompressor. The sensitivity of instruments of this kind can be considerably increased if the membrane is replaced by a system of flat hollow disks whose cavities are connected with one another (as is done in sensitive aneroid barometers). Such differential manometers (Fig. 6) are used for determining the flight speed of an airplane. The advantage of membrane differential manometers is their compactness; their drawback is lower reliability of operation. Since in our case there is no urgent need to strive to reduce the dimensions of the regulator, and reliability of operation plays the principal role, it may be supposed that float instruments will be more suitable for the purposes of automating fan installations.

An example of differential manometers with mercury filling and soldered-in contacts is the Galvaks automatic steam meter. Its construction is as follows: in one of the arms of a U-shaped tube filled with mercury, platinum contacts connected with a resis-

actuations (Fig. 7). When the mercury level in this knee rises, the resistance introduced into the counter circuit changes. The number of revolutions of the counter

Fig. 5

therefore depends on the pressure drop. By connecting a resistance into the circuit of an ohmmeter in the way this is done, for example, in a Siemens steam meter,

Fig. 6

…one may also judge the magnitude of the pressure difference from the ohmmeter readings. In our opinion, U-shaped manometers with soldered-in contacts and filled with mercury could successfully be used for the automation of mine fan installations according to the “constant flow rate” principle.

In installations operating according to the “required flow rate” principle, the connection of the sensors (especially if an electrical gas analyzer is adopted as the sensor) with the actuating mechanisms of the regulators can be accomplished only electrically. In this case, as was already stated above, it will be necessary to resort to amplifying the current in the bridge by means of electronic devices.

Fig. 7

Arrangement of the Individual Elements of the Automatic Control Circuit for a Mine Fan Installation

The arrangement of the automation circuit as a whole, apart from the selected type of sensor—which depends on what principle is made the basis of the automation—should be influenced most substantially by the type of the fan installation itself. At present one may speak of two types of fan installations: 1) fan installations with centrifugal fans, and 2) fan installations with axial fans.

In our opinion, as the drive for mine fan installations with centrifugal fans, whose regulation must be carried out by changing the number of revolutions, it would be rational to use direct-current motors supplied from controlled mercury rectifiers (at high powers) or from thyratrons (at low powers). For automatic installations this will probably be virtually the only possible type of drive. For axial fans, whose regulation could be carried out without changing the number of revolutions, in our opinion it is rational to use synchronous motors (at high powers) and asynchronous motors (at low pow—

...carrying capacities). These thoughts have already been expressed by us earlier ¹¹) and do not diverge from the “Resolutions of the Conference on the Electrification of the Coal and Mining-Ore Industry,” held in Kharkov on 17–22.XI.1939 (published in 1940).

To change the speed of a direct-current motor supplied from a controlled mercury rectifier or from thyratrons, it is at present considered most convenient to use a phase regulator connected into the grid circuit through a peaking transformer. Thus, the task of regulation in installations with centrifugal fans will be reduced to turning the rotor of the phase regulator in one direction or the other. Regulation of axial-flow fans in automatic installations is most conveniently accomplished by turning the blades of the impeller at a constant speed. In existing designs of axial-flow fans, turning the impeller blades is a complex operation and cannot be performed without stopping the fan. However, it presents no difficulties to design such an axial-flow fan in which the impeller can be turned without stopping the fan (“while running”). At present Kaplan hydraulic turbines with adjustable blades, submarine propellers with adjustable blades, and even airplane propellers with adjustable blades (so-called variable-pitch propellers) are already being built. Experience in designing variable-pitch propellers (VPP) should be of great benefit in designing axial-flow fans with adjustable blades. An analysis of modern designs of propellers with pitch variable in flight readily shows that some designs of these propellers, such as, for example, Hamilton-Standard propellers, as well as KhIZ propellers, cannot be used at all in our case; among those that can be used as a prototype for creating a fan with adjustable blades, the most applicable will be the Smith propeller (with mechanical drive), shown schematically in Fig. 8. It is also possible to use the propeller design of Eng. Lysenko (TsIAM) with a hydraulic drive (a variant of the Gloster type), ¹²) but this design is more complex and its use in designing an axial-flow fan with adjustable blades is not necessitated. As can be seen from Fig. 8, in the case of automatic regulation of axial-flow fans with adjustable blades, as also in the case of centrifugal fans, the regulating impulse can be given in the form of rotary motion. However, another solution to the problem is also possible, in which the blades will be turned by displacement of the piston of an oil servomotor (Fig. 9).

Fig. 8

On the basis of the above analysis of possible variants of automation for mine fan installations, certain (preliminary) conclusions may be drawn. In regulation according to the principle of “constant-

¹¹) Assoc. Prof. G. P. Ksyunin, “Automation of Mine Fan Installations,” journal Avtomatika i Telemekhanika, No. 3, 1939.

¹²) B. L. Minukhin, Investigation of a Propeller with Pitch Variable in Flight, TsAGI Publishing House, 1934.

of the “constant-flow” principle for a ventilation installation with centrifugal fans (drive from a DC motor supplied by a controlled mercury rectifier or by thyratrons), the best type of sensor will be a multiplier consisting of several Venturi tubes. The transmission from the multiplier to the regulator, which is a phase regulator connected into the grid circuit, is best accomplished by means of a U-shaped manometer with mercury filling and soldered-in contacts. In the absence of any moving parts, this device will be the most reliable in operation and, moreover, makes the regulator as compact as possible. The circuit of such a regulator is shown in Fig. 10. As can be seen from Fig. 10, if the difference in mercury levels in both limbs of the U-shaped manometer is greater than the prescribed value, contact 1 closes, which, by means of contactor \(k_1\), acts

Fig. 9

Fig. 10

on the actuator of the regulator in the sense of lowering the number of revolutions of the motor. When the difference in levels in the limbs of the U-shaped manometer decreases, closing of contact 2 and switching on of contactor \(k_2\) produce the reverse action. In regulation according to the “constant-flow” principle for a ventilation installation with axial fans (drive from a synchronous or asynchronous motor), as in the preceding case, the best type of sensor will be a multiplier. However, since here there is no need to act upon the electrical part of the installation and only mechanical action is required from the regulator, the transmission is more conveniently carried out through a float volometer, according to the scheme shown in Fig. 11, which is so simple that it requires no explanation. Finally, in regulation according to the “required-flow” principle, when the regulator sensor is an electrical gas analyzer, regardless of the type of fan, the connection of the sensor with the actuator can only be electrical. The circuit for switching on the regulator, both with a centrifugal and with an axial fan, may be one and the same, since (as is evident from what was said above) in both cases the actuator must receive the regulating impulse in the form of rotational motion. The schematic diagram of the regulator for this case is given in

Fig. 12. As can be seen in Fig. 12, a change in the content of \(CH_4\) (or \(CO_2\)) in the common outgoing stream will affect the readings of ammeter \(A\), which, through an amplifier (an electron tube), is connected with a Siemens-type gas analyzer (the gas analyzer and amplifier are not shown in the diagram).

Fig. 11

Fig. 12

is connected with the pointer axis of this ammeter (the Siemens ring), filled halfway with mercury and provided with soldered-in contacts 1, 2, and 3. When the content of CH₄ (or CO₂) deviates from the established limits, either contact 1 or contact 2 will close, and regulating pulses will be issued in the same manner as was described above in considering the circuit of Fig. 10.

The main task in automating mine fan installations is to regulate their output. But a mine fan installation can also be made fully automatic; i.e., provision can be made both for remote starting of the operating fan and for automatic transfer to the reserve fan (in the event of an accident of the operating fan), including the repositioning of the dampers of both fans. (A sketch of such a scheme was given by us in the article “Automation of Mine Fan Installations” in No. 3 of the journal Automation and Telemechanics for 1939.)

In our opinion, the automation of mine fan installations not only presents nothing impossible, but can be carried out quite easily, at least in its simpler version (according to the principle of “constant delivery”). As for the economic side of the matter, if one takes into account that mine fan installations consume no less than 15–20% of all the energy going to the production needs of mines, and that losses in modern (non-automatic) installations are very substantial, this question should leave no doubt as to the necessity of automating ventilation installations. What has been said may be illustrated by the following example: the cost of the energy expended on ventilating a mine reaches, as is known, 20–30 kopecks per ton.¹³ Let us assume, for caution’s sake, that the cost of the energy expended on ventilation averages 10 kopecks per 1 t. If we now accept that the over-expenditure of energy due to the absence of delivery regulation amounts to only 25% of the normal value, then even in this case we would have a saving in energy expenditure, due to automation, of 2.5 kopecks per ton. For a mine with an output of 300,000 t per year (of average capacity), the saving would amount to 7,500 rubles per year. For all the mines that are to be put into operation in the Third Five-Year Plan, this saving would be somewhat more than 4 million rubles per year.

¹³ Prof. Dr. K. A. Ushakov, Prof. V. I. Polikovskii, Eng. M. I. Nevelson, Assoc. Prof. M. L. Tatarinov. Mine Fan Installations, GONTI, NKTP USSR, 1938, p. 15.

1. Doc. G. P. Ksyonin, “Automation of Mine Fan Installations.” Journal Avtomatika i telemekhanika, No. 3, 1939. ↩

2. Prof. G. M. Elanchik, Turbomachines, vol. I, pp. 263, 324. ↩

3. Ibid., p. 185. ↩

4. Anemometers of the types described are sometimes installed on airplanes as indicating instruments. ↩

5. V. L. Temkin and V. D. Sherentsis.—Monitoring the Operation of Boiler Installations. ONTI Energoizdat, 1934, p. 181. ↩