July 31, 1914. THE COLLIERY GUARDIAN. 265 _________________________________________________________________ Colliery Consumption and Machine Economy at an Upper Silesian Colliery.* By Dr. KARL SCHULTZE.t (Concluded from page 199.) Consumption of Energy by the Winding Engines. As shown before, the stoppage losses alone amounted daily to 69-2 tons of saturated steam, equivalent to a reduction of the normal consumption of 44-8 lb. per horse-power hour. A daily radiation of heat amounting to 1,714,000 British thermal units was found in the summer, which corresponds with 8*7 tons of condensation water. Of this, 4-5 tons are apportioned to the piping leading to the winding engines, and 4-2 tons to the piping inside the boiler house. These values increased during the winter by 25 per cent. The heaviest loss was from leakage in the valve gear, stuffing boxes, and brake cylinders, which were much higher than the losses through leakage in the piping. The advantage of a condensing plant depends, to begin with, on the required power. Through the investigations made by the Dortmund Boiler Inspection Company, it was found that for a given plant the required power is nearly constant, and varies but little according to the output. With a plant only half utilised, the consumption of power is 10 per cent, less than with full output. This point is a very important one in connection with plants running an intermittent working such as a mine. The calculations for the existing working conditions showed that a real saving of power could take place only when the saving of steam by the vacuum was more than 12 to 14 per cent. The more economically a wind- ing engine works, the less important is the saving of steam, considering the small consumption compared with the expense of the condensing plant. It may be said that a condensing plant mainly for winding engines is not worth while. Electrical Plant. In order to determine exactly the distribution of the energy generated by the electrical plant, the Siemens- Schuckert Company placed five standard meters with suitable transformers for electric current and voltage, and also some instruments of precision at the writer’s disposal. The consumption thus ascertained had to be compared with the total production, which was deter- mined at the same time through the generator meters, and the consumption of every circuit was expressed in the percentage of the total consumption. Calculating further with this value, instead of with the absolute value, the variations of the production during the obser- vation time was taken into consideration to some extent. The values so found are recorded in the following table :— Consumption per year. Particulars. ' Kilowatt- T hours. Per cent Transformer for production of motor-current for the recipro- cating engines .............. 187,200 ... 1’38 Cooling-water pump of the turbo- generators ................. 27,100 ... 0’20 Central condensation plant .... 1,092,000 ... 8’05 Pumping plant for boiler-feeding and cooling water .......... 173,100 ... 1’28 Transformer for the production of current for the conveyor and the chain-grate ............ 31,000 ... 0’23 Lighting .................................... 308,100 ... 2’27 Pumping plant underground ... 5,716,900 ... 42’12 Hauling...................... , 419,300 ... 3’09 Ventilation .................. 687,500 ... 5’06 Washing and loading plant .... 968,800 ... 7’12 Gobbing plant................ 185,000 ... 1’36 Workshops .................. 45,800 ... 0’32 Other works .................. 3,201,500... 23’61 Sundries...................... 528,700 ... 3’91 Total production .......... 13,572,000 ... 100’00 The energy absorbed by the transformers was 5’5 per cent, of the energy produced, and the condensing plant amounted to five kilowatt-hours per ton of steam used. It was impossible to measure the quality of water raised, and so it was found by multiplication of the time during which the pumps worked, with the nominal out- put. The ascertained values are set forth in the follow- ing Table A. With a proportion of 42%, the pumping plants had the greatest consumption of energy of the mine. Table A. Particulars. Reidler pump 656-ft. level. Bergmann pumps 984-ft. level. 25 and 35 horse- power pump at the 984-ft. level. Old pumping plant at the 1,640-ft.level. New pumping plant at the 1,640-ft.level. Quantity of water raised, in cubic feet per minute Height n __ work done through raising water energy supplied to the motor Quantity of water raised, in cubic feet per year Effective work done through raising water, in horse-power-hours per year Consumption of electricity, in kilo- watt-hours per year 52’9 689 ft. 0’75 9,600,000 212,000 211,000 194T5 958 and 984 feet. 0’76 and 0’75 134,840,000 4,163,000 4,134,000 195,400 52’9 and 105’8 639’6 ft. O’7OandO’78 39,310,000 804,700 820,000 211’8 1,591 ft. 0’70 6,205,000 315,500 357,000 With regard to weight, the quantity of water raised to the surface was 4’15 times greater than the output of coal. Owing to the importance of these plants, the management had to consider seriously all the possibili- ties of improvement, as here a slight alteration might influence the economy of the whole machinery. The daily and nightly working of the mine, gives a much better load-curve of voltage than, for instance, for a municipal electrical station. As disturbing elements, there are only the stoppages of the winding, of the washery, of the gobbing plant, and of the con- nected works, and also the starting of the large motor in the rolling mill. But, considering the often intermit- tent working of the pumping plant, it should not be difficult to form a working scheme wherein the consumption of electricity of the pumps fits well in the curve of electricity consumption of the other consumers. As, further with an increase of the electrical plant the variations in the electric current caused by the rolling mill motor will become more insignificant, it may be expected that the voltage curve (already a good one) may be improved upon, and together with careful arranging and surveying may guarantee an excellent economy of the whole work. Compressed Air Plant. Compressed air serves not only for ventilation through air jets, but also for driving hammer drills, rock boring machines, conveyors, hoists, and pumps. The whole plant was started only two years ago, which explains the increasing number of engines working. During the observation time there were in action 77 to 103 hammer drills, four to 13 boring machines, 12 to 29 oscillating conveyors, two to three winches, and two pumps. The percentage of losses through leakage is a very high one, despite the normal utilisation of the plant. But, having regard to the extent of the piping—88,500 running feet—the enormous quantity of the measured losses is easily understood, especially considering that the piping had constantly to be enlarged, owing to the progress of the workings, and, therefore, it was very difficult to obtain satisfactory measurements. The management tried to lessen these losses through a very careful inspection, but only succeeded temporarily in decreasing the losses from 25 to 17 per cent. A large quantity of air is also lost after shot firing by the miners when they tried to clear the place of fumes by opening a cock or even unscrewing a flange. With a total efficiency of the compressed air motor at 35 per cent., the proportion between effective work of the machinery and the indicated useful work of the compressor apportioned to the machinery amounted to 0’215. In order to produce an effect of 1-horse power hour by the secondary machinery, it is therefore neces- sary that the compressor should produce 4’65-horse power hours hourly, and the boiler house in this case 83’6 lb. of steam. The consumption of compressed air in jets for sweep- ing out gases and fumes in the workings has been referred to, and it accounts for a considerable waste of expensive compressed air, out of all proportion to its efficiency. Without denying that there may be occa- sions on which the use of a jet is convenient, it is certain that to allow the miners to make use of compressed air for this purpose at their own discretion is most extrava- gant and undesirable. At the Ferdinand Pit where air tubes of about 8 in. in diameter and air jets of about in. diameter were used, the highest pressure was about 901b. per sq. in. The efficiency of this was calculated by Arlt to be 0’2 per cent. Cost of Coal. To put a proper value on the boiler fuel consumed is important, not only for the calculation of the cost price, but also for estimating the economy of power. The management regarded the coal to be of such low value as to be unsaleable, as the Upper Silesian Coal Syndicate fixed the lowest price for this coal at about 3s. 6d. per ton. The fact is that, when trade is bad, * From a paper read before the Midland Institute of Mining, Civil, and Mechanical Engineers. t Translated by Mr. G-. Blake Walker and Mr. Arthur Franks, and revised by author. The paper, which appeared originally in Gluckauf (1913, vols. xliii., xliv., and xlv., pp. 757 et seq.f has been reproduced in an abbreviated form by permission of that journal. there is not sufficient demand for this coal at the price mentioned, and it was necessary to carry large quantities to the heaps, where it crumbled away, and was used later as material for gobbing. About 20,000 to 30,000 tons of coal were thus lost every year. But also at other times the management was not anxious to sell this coal, as it was feared that it would enter into competition with good coal which realised a price three or four times higher. The question therefore arose whether it was more economical to sell the available low-priced coal, or to increase the output and let the inferior coal go to waste. For a long time it has been usual for the Kattowitz Company to utilise this small coal more and more in supplying their own works, that is, for the rolling mills, electro steel furnaces, electro-chemical factories, etc., and in this way an amount is realised which is at least equal to the lowest market value of the small coal. Taking, therefore, the value of Is. 7-J-d. per ton put by the mine management in the calculated net costs as too low, and calculating with an estimated value of 3s. 7|d. per ton, the writer must protest against the idea that the net cost price should be chosen as the lotvest value. This idea rests upon an erroneous sup- position that it is more advantageous to reduce the output than to sell under the net cost price. At first sight, the mining industry has this characteristic feature, as contrasted with other industries, that the product of high value costs as much as the product of low value, and that it is impossible to obtain the better kinds of coal without large quantities of coal of lower value. As the separate energy costs are given in the following section of the paper, it will be easy to compare the net cost price also with other coal prices. Working Expenses. Although it was necessary, for the purpose of fixing the amount of the invested capital, to look through the books for a period of more than 20 years, the writer succeeded in ascertaining the net cost prices per ton on the cost of the plant with sufficient accuracy, taking no account, of course, of the land values. The latter were acquired so long ago that, if taken into con- sideration, they would not now have any economic interest. It would also be difficult to distribute these costs to the different departments of the mine, and it appeared, therefore, more useful to examine them separately from the other expenses in the same way as working expenses. As interest on the investments a rate of 5 per cent, was taken, but as interest on the sinking fund only 4| per cent. These costs are enumer- ated in Table B on next page. A further table (C) sets forth the yearly working costs. The different efficiency of the two plants was apparent, not only with regard to the coal consumption, but also in the same proportion to the other items. Water from the district water supply cost Is. 6d. per 1,000 gals. The average price of water was about 6d. per 1,000 gals. The coal consumption of the boiler plants, inclusive of the quantities consumed from the boilers on the Ludwig Pit for the baths and the winding engine, amounted to 8*5 per cent, of the output per year. In order to ascertain the consumption only of the mine, 23’4 per cent, of the consumption of the battery of twin boilers (which corresponds to the electricity supplied to other works) is to be deducted from the above amount, so that the remainder is only 7’1 per cent. On the basis of a steam production of 230,000 tons in the twin boiler plant, and of 139,000 tons in the Lancashire boiler plant, the cost of steam amounted to Is. 7d. and Is. l|d. per ton respectively. The stores cost of the turbines was 0’00114(1., and of the reciprocating engines 0’04d. per kilowatt-hour. This very unfavourable comparison (which is on an average about 1 : 10) is explained by the alternate working of the reciprocating engines, some of which, therefore, always had to stand idle, whereas the working of the turbines was continuous. The cost of repairs was also greater with the reciprocating engines than with the turbines, being 1-319 10s. against .£69 10s. The expenses of the central condensing plant, which were 4’425d. per ton of steam, were very high, owing to the great waste of electricity and constant repairs. The cost price for electricity was 0-447d. per kilowatt-hour. This value is to be taken as a middle value between the price of generated electricity and the electricity trans- formed to 2,000 volts, which was about 0’0025d. dearer. The cost price for compressed air at the compressor was 0’27d. per 35 cu. ft., or 0’36d. per indicated horse power hour. The consumption of engine oil and waste was very high : it amounted to more than £1 per day. The oil was refined again as far as possible, and used again. In calculating machine economy, the mistake has often been made of reckoning with only slightly higher costs at the utilisation point of the compressed air than at the cost of production. But the investigation has proved that the cost increased by more than double in transmission. To these figures must be added the losses through leakage, amounting to 21’5 per cent, of the production. The actual costs at the working point were 0’709d. per 35 cu. ft., or 0’95d. per horse-power hour. The pro- portion of the compressed air which was lost in leakage and jets amounted to 31’5 per cent., and 68’5 per cent, was left for the coal production. And here it became evident that the jets, despite their small value for ventilation, accounted for approximately half of the total cost of the ventilating plant, fans included. Not only was the cost of the working of the ventilators (fans) examined, exclusive of air shafts, air roads, etc., but also the expenses of the whole ventilating plant (excluding air jets). Effectively, 462,000-horse power hours were performed, and 10,484 millions cu. ft. of air exhausted. The expenses of the former amounted to 0’874d., and those of the latter to 2’08d. per horse- power hour. The cost of effective work in the raising of the water