January 5, 1917. THE COLLIERY GUARDIAN. 31 _____________________________________________________________________________________________________________________________________________________ CHAIN BELT FOR COAL AND COKE * By A. A. Wegner. A substantial yet inexpensive coal and coke handling system has been installed at the North Avenue Fuel Company's yards in Milwaukee, Wisconsin. Coal and coke are received in bottom dump cars, which are switched over a steel track hopper located between the rails of the railroad track. The track hopper is level with the railroad track on top, and has a discharge opening at the bottom large enough for mine run coal. A large hinged gate, operated from the ground level by means of a lever, regulates the feed to the conveyor. The operator dumps the car, and the material flows by gravity from the track hopper to the conveyor beneath, which carries it to the storage pile. Both the track hopper and loading end of the conveyor are in a pit. The conveyor consists of two strands of steel roller chain belt, with a steel flight suspended between them. The chain travels upon a steel lined track in a groove, and hence does not come in contact with the material to any appreciable extent. The entire framework is of wood, and the trough along which the coal and coke are pushed by the flights is lined with steel. The con- veyor is set at an incline, and after attaining a height of 25 ft. runs horizontally. The horizontal portion is provided with slide valves, and below each slide valve is a rotating gate. This permits discharging coke on one side of a central partition, and coal upon the other. Chain Belt Distributing Coal. The various grades of coal are kept in separate bins, and by manipulating the valves and gates the discharge of material can be directed to any particular bin. A walkway gives ready access to any portion. An electric motor, controlled from the ground level, drives the conveyor, and the system has a capacity of 30 tons per hour. All gears are well guarded, and the simple construction of the entire system leaves small opportunity for accidents. When making deliveries out of storage, the material is loaded into wagons with a wagon loader. Thus, one man ordinarily can take care of the entire work con- nected with receiving coal by rail in bottom dump cars and loading wagons for delivery to customers. ________ ________________________________________________________ * Black Diamond. LETTERS TO THE EDITORS. The Editors are not responsible either for the statements made, or the opinions expressed by correspondents. All communications must be authenticated by the name and address of the sender, whether for publication or not. No notice can be taken of anonymous communications. As replies to questions are only given by way of published answers to correspondents, and not by letter, stamped addressed envelopes are not required to be sent. VISUAL AND AURAL SIGNALS. Sirs,—I note in your issue of the 22nd ult. a report of a paper read by Mr. D. M. Mowat on the “ Summer- lee ” visual indicator, wherein this gentleman states that “ a defect inherent to earlier visual signals was that a signal ‘ 1 ’ given while the engine is running remains uucancelled after the engine has stopped, and then conveys an entirely different meaning (viz., to raise the cage) which if acted upon might cause an accident.” I wish to point out that Mr. Mowat is under a wrong impression in stating the foregoing, which rather points to the fact that he is not well versed in the visual signals which aire on the market. I might instance the system of visual and aural signals made by John Davis and Son (Derby) Limited, where the well-known “Davis-Macdonald” ball-race release gear is employed. This clears the signal imme- diately the engine ‘1 starts, ’ ’ and also when the engine “ stops ”; but the “ men ” signal (which is shown on a flag appearing in a space cut in the dial) is not cleared on stopping, arrangements being made for this signal to be cleared only at starting, as the signal “ men ” is generally given when the cage is running. I might point out that the patent specification of the “ Davis-Macdonald ” ball-race gear appeared as far back as August 1914. I think this will tend to show that what Mr. Mowat considers as novel has been effected practically from the inception of visual and aural signals. Signals. January 2, 1917. THE MOVEMENT OF MINE GAS IN COAL AND SURROUNDING ROCK.* By M. N. Charnitzyn. One of the most interesting questions connected with mine gas is undoubtedly that of the causes which make different deposits, similar in chemical composition and geological conditions, differ sharply in regard to the quantity of gas they liberate. In all such cases, the most probable explanation is that the conditions in which the less gaseous deposits exist have favoured the liberation o.f their contained gas into* 1 surrounding rocks.f The conditions which co-operated in exhausting the deposits in respect to gas might have existed in the earlier periods of the formation of the deposits, or may have come into operation later. No sufficient material is available at present to afford a complete elucidation, and the task of the investigator is restricted to collect- ing facts. Loss of Gas Through Porous Rock. A certain portion of the methane may escape to the surface through fissures in the cover of the seam and overlying rock. The absorption of the gas through microscopic pores in the rocks in mines is equally pro- bable, particularly if the pores are not filled with water. The extent of this process cannot be estimated, and may vary considerably, according to local conditions and the properties of the rock. In order to illustrate the point, the author took a sample of light grey clayey schist 5 sazhens} above’ the very gaseous Vladimir seam of the Ivan mine. A large piece of this schist was broken into small lumps up to J in. in diameter, which were placed in a receptacle, in order to extract the gases in vacuo by the aid of a Sprengel pump. Under such conditions of test, it can be understood that it was impossible to obtain all the gas contained in a whole lump, and some part no doubt escaped while the schist was being crushed. After continuous extraction for a week, the liberation of gas ceased. The total quantity of methane was 10’3 c.c. per kilog. of schist. The quantity of carbon dioxide amounted only to 1'1 c.c. A second sample was taken, at a distance of about 20 to 25 sazhens, from the same bed. It consisted of lumps of large-grained, almost white sandstone. Under the same conditions of test, 1 kilog. yielded 3 c.c. of carbon dioxide, and only 0'3 c.c. of methane. The sandstone was rather moist. A third sample was taken from the Capital shaft of the Ekat. Mining Company in a section between two hard, gassy seams. In the schist from which this sample was taken, 0’7 c.c. of carbon dioxide and 0-2 c.c. of methane per kilog. were observed. Thus only the first sample, taken 5 sazhens from the seam, contained a large quantity of gas extractable in vacuo. Samples from places more' remote disclosed, under the same conditions, merely traces of methane. Dissolving Out the Methane with Water. Water dissolves methane only in small quantities (0’034 part per volume), and it is therefore hardly to be expected that it can take up any great quantity of the gas. For this to be done, there would be required a very considerable quantity of water, which would perhaps only be present in the very earliest periods of the existence of the deposit. In order to obtain infor- mation on this point, four samples of water were taken.: one from a fissure in a section of the Ivan shaft between seams 40 sazhens apart, and two others from worked seams at the Almaz and Berestoff shafts of the Italia mine, a fourth sample being taken from a borehole made in the Makeieff bed. The gases dissolved in the water were given off when the water was boiled under reduced pressure. The results of the tests are given in the following table, showing the quantity of gas in c.c. per litre of water :— Table I. Sample CQ CH,. No. 1 ..... 6’4 ..... 2’4 2 ..... 8’3 ..... 5’7 3 ..... 14’0 ..... 3’0 4 ..... 18’2 ..... U7 __________________ ______ * Gorno-Zavodskoye Dyelo. f Another explanation may lie the dissimilarity of the processes that accompanied the conversion of the vegetable substances into coal, or differences in the mother substance from which the deposits were formed; but in the present state of our knowledge of coal, no definite light can be shed on the question. t Sazhen = 7 ft. As the table shows, in no case did the quantity of methane absorbed by the water reach the theoretical limit (34 c.c. per litre). Movement of Gas in a Coal Seam. Part of the mine gas may escape upwards directly through the coal deposit, from its lower levels to its upper levels. The permeability of coal for gases, depending to a large extent on the density of the coal itself, may, in certain circumstances, play a charac- teristic practical role in this method of freeing the deposit from gas. No sufficiently accurate method of determining the permeability of coal is at present available, but an approximate idea may be obtained by observing the oozing of the gas from the standing coal through holes bored therein. This method of experiment was adopted in the Ivan shaft and in the Novosmolyaninoff mine. Tn the Makeieff seam (thickness 7 ft. 4 in.) three holes of 1 in. diameter were bored in the middle bed of coal. The holes were bored in the wall of the incline leading to the pillars. This incline started 100 sazhens from the bottom road, and throughout the. whole length there was no intermediate working. The depth of the seam in this place was about .150 sazhens; it was very hard, and so was the roof. The hole was 2|m. deep, and | in. tubes, each with a gauge, were inserted. In order to insulate the hole from the open air, the mouth was widened, and then cemented. The object of the test was to ascertain the pressure of the gas inside the hole, the changes in this pressure with time, and the variations in the quantity of gas liberated from the hole when opened. The first two holes were made at a dis- tance of two arshines* apart, and the third was three sazhens from the second. Pressure of Gas in the Holes. Immediately after closing the first and third holes the pressure began to rise, and in about 15 minutes reached an approximately permanent level. This was also observed after periodic openings of the holes for short spaces of time. The pressure of gas in hole No. 1 began at about 17 funts (I funt = 0’9 lb.). During the first four days it gradually rose, and reached 26 funts at the end of that time. Then the hole was opened for 20 minutes, dur- ing which about 30 litres of methane escaped. In the succeeding 11 days the pressure fluctuated between 19 and 20 funts, reaching 24 funts very rarely (the register was taken six times per 24 hours). On the 15th day the tube was opened again for 30 minutes, and 48 litres of gas were obtained. At the same time, the tube was drawn from hole No. 2, and the gas was allowed to escape freely through it into the working. This circumstance brought about a reduced pressure in hole No. 1, but on the following day, having risen on the preceding one to 18 funts, the pressure fell to 13 funts, and again to 11 funts in the succeeding 24 hours. It remained at this level for 20 days, where- upon a rise to 14 funts occurred, which was maintained for another 12 full days. The tube was then opened for 30 minutes and again closed; five minutes after this the pressure wais nine funts, and 15 minutes later 14 funts. This movement corresponded to the 48th day. In the course of the subsequent 51 days, the pressure fell to 10 funts; on the 107th day a fresh decline to eight funts occurred, and remained thereait until the 132nd day. Hole No. 2 was two arshines distant from the pre- ceding one in the same seam. The pressure did not reach a- limit that could be registered by the gauge (two funts), though the total escape of gas in this hole was greater than in hole No. 1. The explanation of this may be found in the presumption that the coal near this hole was rather porous, and that the gas could more easily escape through the outer wall of the mass. After 15 days the tube was taken out of the hole, which emitted a droning sound during the whole course of the experi- ments. Hole No. 3 was bored three sazhens away from the second, 15 days later than the first two holes. After 24 hours the pressure in the tube reached seven funts, and remained thereat for nine days, when a rapid rise to 17 funts was observed, and a further rise to 20 funts in the following 24 hours. This pressure continued for two days more; then, the gauge being injured, the insu- lation of the hole was destroyed, and the gas was able to escape through small fissures in the concrete. On the 116th day the pressure in this hole was less than two funits. Liberation of Gas from the Holes. This was measured with short-period discqnnec- tions of the gauges. The quantity of gas liberated is shown in Table II. In calculating it, no account was taken of the gas that escaped from the tube immediately after it was opened. In hole No. 1 the pressure reached the maximum on the 15th day, and a corresponding increase in the libera- tion of gas was observed in that period of the test. Later, as the pressure declined, the accumulation of gas weakened. Table II. Quantity of Gas per Hour in Litres. Day. Hole No. 1. Hole No. 2. Hole No. 3 1st 30 180 60 5th 30 90 — 15th 48 36 — 23rd — — 30 38th 36 ” — — 79th — —— 16 95th 20 ” — — 116th — — 5 131st 20 — — In hole No. 2. as already stated, the pressure was too small to be registered at all. However, the libera- tion of gas from this hole was the greatest, and its decline in course of time was more intense. * Arshine = 2 ft. 4 in.