THE COLLIERY GUARDIAN ________________________________________________________________________________ B18 September 10, 1915. specified for 250-volt, 100-ampere fuses by the National Electric Code. The fuse is so placed that it is accessible from outside the machine without removing any covers, but the controller handle must be in the “ off ” position before the fuse can be removed, and removal of the fuse locks the controller handle in the “off” position. Cable Reel.—The cable that connects the cable reel to the- power supply is permanently connected to slip rings which are enclosed in an explosion-proof casing The cable that connects the cable reel to the motor is provided with a plug which connects with the slip ring brushes in such a manner that arcs can not get outside the casing if the plug should be withdrawn while the current is flowing. Trailing Cable.—The trailing cable is clamped to the frame of the machine by an insulated clamp that sustains any strains that might otherwise come on the insulated binding posts by means of which electrical connect! m is made to the interior of the controller casing, These binding posts are specially designed to prevent the working loose of stranded conductors and are protected by a metallic shield. Where the trailing cable enters the machine frame and also where it is attached to the cable reel plug, the cable is protected by a flexible steel armour that bends easily to a minimum radius beyond which it will not go. This armour is designed to prevent the excessive wear that usually occurs where cables of this sort enter metallic frames. Complete Equipment.—The complete equipment (figs. 1 and 2) is built in accordance with the Bureau’s require- ments and recommendations as already set forth. All wires are enclosed in explosion-proof casings from the point where the connection to the trailing cable enters the casing of the starting rheostat. All bolt holes are bottomed or stud bolts are used, so that the omission of a bolt does not leave an opening through the explosion-proof casing. Tests.—Tests were made at the Pittsburg experiment station of the Bureau of Mines with the motor, starting rheostat, and cable reel, and no ignition was obtained with percentages of gas amounting to 7 and8’6 percent., with and without dust. The following maximum pressures were obtained: 126 lb. per square inch in the casing of the starting rheostat, 74*6 lb. per square inch in the motor casing, and 35 lb. per square inch in the slip-ring compartment of the cable reel. The fuse was tested 15 times by connecting it across the bus-bar of a 200-kilowatt, 225-volt, direct-current generator in series with a resistance equivalent to a circuit of No. 4/0 B. and S. gauge wire 530 ft. in length (one way). The fuse opened the circuit promptly, with practically no noise, and absolutely no evidence of flames or sparks. The test proved that the protection of the motor, starting rheostat, and cable reel was adequate at the time of testing. A factor of safety was produced by requiring changes in construction that reduced the maximum pressure from 126 lb. per square inch to less than 50 lb. per square inch in any part. It is considered that with reasonable care the equipment can be main- tained permanently in an explosion-proof condition. The equipment has therefore been approved by the Bureau as permissible for use in gaseous mines. SOUTH AFRICAN MINING IN 1914. According to the annua] report of the Department of Mines and Industries for the Union of South Africa, the mineral production in 1914 reached a value of £45,366,224, compared with £52,924,990 in 1913. 3 he reduction is almost wholly accounted for by the closing of the diamond mines on the outbreak of war. The output of coal, however, as will be seen from the following table, also fell off in volume, although there was an increase in value. The table shows sales :— Tons of 2,0001b. Per ton. Province. ^1913. 1914.”^ ^913. 1914? s. d. s. d. Transvaal ........... 5,225,036...5,157,268... 4 4*48... 4 5'55 Cape ................. 67,181... 53,621...11 5'82...11 7'50 Orange Free State ... 609,973... 699,217... 5 5*87... 5 5'58 Natal ............... 2,898,726...2,567,817... 6 1 83... 6 10'80 Totals .......... 8,801,216...8,477,923... — ... — Further details are given in the following table :— Output of Coal in 1914. (1 ton = 2,000 lb.) 'o bi) “ s Area and ® 2'u province. g -fl £ § S g K ft Springs-Brakpan area ....... 5 ... 572,666...25-81... Coal sold. _______ _______ xn fl O fl g ’cg £< O s. d. 421,161... 4 10-45 Middelburg area 14 ... 4,577,407...11-34...4,008,944 .. 4 5’81 Other areas .... 6... 779,228... 3 35... 727,163... 4 1 28 Transvaal .... 25 ... 5,929,301.. 11-69 .5,157,268... 4 5'55 Cape........... 8... 67,603...20-74... 53,621...! 1 7’50 Heilbron_______ 2 ... 705,194... 4-49... 627,961 5 4'38 Kroonstad ...... 2 ... 85,239... 10-63... 71,256... 6 4 13 Orange Free Ste. 4 ... 79 *,433... 5-15... 699,217... 5 5'58 Dundee, Klip River, and Newcastle ... 17 ... 2,793,832.,.24’92...2,079,376... 7 3’51 Utrecht and Vry- heid ......... 4 ... 638,849...22-56... 488,441... 5 2'77 Natal ......... 21 ... 3,432,681...24’48 2,567,817... 6 10’80 Union of South Africa ...... 58 ...10,220,018... — ...8,477,923... — Year 1913 .... 61 ...10,732,653... - ...8,801,216... — Year 1912 .... 65 ...10,059,037 ,. —...8,117,078... — ______________________________ Shipments of Bunker Coals. — The quantity of coal, etc., shipped for the use of steamers engaged in the. foreign trade during August was 1,158,729 tons, as against 1,147,437 tons in August 1914, and 1,749,847 tons in August 1913. The aggregate so shipped during the eight months ending August 31 was 9,657,927 tons, as compared with 13,249,027 tons and 13,720,560 tons in the corresponding periods respec- tively of 1914 and 1913. The University of Sheffield.—In the Department of Applied' Chemistry, under the direction of Prof. L. T. O’Shea, M.Sc., M.I.M.E., the following courses of lectures will be given during the session 1915-16 :—Day lectures, coke manufacture and by-product recovery, tar and tar distillation; evening lectures, tar and tar distillation. The chemical laboratory is open daily from 10 a.m. to 5 p.m., except Saturday, and in the evening on Friday from 6 to 9 p.m. Instruction is given in analysis of fuel and by-products, in tar distillation, and analysis of mine air. For information, apply the Secretary, Applied Science Department, the University, St. George’s- square, Sheffield. In addition, 113 tons of coke, valued at £118, were produced in the Transvaal, and 6,380 tons, value £12,259, in Natal; 2,225 gallons of tar were produced by Transvaal coal companies, valued at £124. During 1914, 1,343,240 tons of coal were shipped as bunkers, as compared with 1,451,751 tons in 1913, and 651,210 tons were exported, as against 856,031 tons in 1913. In December 1914, 25,127 persons were engaged at coalmines, divided as follows :—Whites, 1,229 ; Asiatics, 3,575; natives and other coloured persons, 2D,323. According to province, the distribution of labour was :— Transvaal, 10,898; Cape, 859 ; Orange Free State, 2,203; Natal, 11,167. In salaries and wages, the coal mines paid out £35,601 more than in 1913, the total being £991,822. In addition, £643,158 was paid for machinery and stores, as against £643,256 in 1913. The total paid by all mines was £12,224,535, a decrease of £1,138,370 on 1913. Nearly half of this represents expenditure on South African products, coal accounting for £1,154,399, and explosives for £1,503,350. The gold mines consumed 21,297 tons of smelting coal, 1,768,931 tons of steam coal, and 23,507 tons of other coal. Accidents. Exports and Imports of Mining Machinery.—Imports and exports of mining machinery during August were as follow : August. Jan.-August. A 1914. 1915. 1914. 1915. Tons. Tons. Tons. Tons. Imports 189 90 . 1,119 ... 765 Exports 1,557 ... 1,414 . .. 15,126 ... 11,590 The value of the imported mining machinery in August was £7,157, as compared with £12,650; and, in the eight months, £58,206, as compared with £74,252. These figures are not inclusive of prime movers or electrical machinery. Accord- ing to destination, the value of exports was as under :— In 1914, 71 whites, five Asiatics and 667 natives and “boys” were killed in accidents at mines, of whom three whites, five Asiatics and 44 natives were killed at coal mines—of the total of 52, 26 in the Transvaal, three in the Orange Free State, and 23 in Natal. Last year’s accident death-rate of 3 05 for the Transvaal is the lowest on record. The Natal Collieries maintain a good record with a death-rate of 1’9 per 1,000. Although a number of mines suffered from gob fires, there have been no explosions during the year leading to a considerable loss of life. In addition to the 743 deaths, 2,273 persons were injured on mines within the Union during the year. The following table shows the principal causes of accident:— Cause. No. of deaths. Percentage. 1913. 1914. 1913. 1914. Falls of ground 315 . .. 275 .. . 31-76 ... 37-01 Trucks and tramways .... 50 .. .. 44 .. . 5’34 ... 5-92 Falling of material 85 .. .. 60 .. . 8’56 ... 8-07 Explosives 240 . .. 156 .. . 24-19 ... 2100 Machinery 39 .. .. 29 .. . 3’93 ... 3’90 To— Countries in Europe..... United States of America.. Countries in S. America ... British South Africa ... ,, East Indies ..... Australia .............. New Zealand .......... Other countries ........ August. Jan.-August. 1915. 1914. 1915. £ £ £ 1.225.. .118.113... 44,426 — ... 840... 113 721... 39,302... 10,910 24,875...200,385...172,458 . 6,297... 55,571 38,224 1.676.. . 31,869... 18,196 1.974.. . 10,138... 7,263 9.447.. .129.190...108.057 1914. £ 3.955.. . 101 . 10.238.. . 24.251.. . 5.325.. .. 2.171.. . 2,056... 9.980.. . Falling in shafts, excavations, etc ... 61 ... 47 .. . 6’15 ... 6’33 Travelling by cage or skip ... ... 51 ... 41 .. . 5’14 ... 5’52 Struck by skip, cage, etc. ... ... 31 M. 23 .. .. 3’13 ... 3-10 Other causes ... 120 .. 68 .. . 12-10 ... 9 15 Totals ... 992 ... 743 .. — — The extent to which the personal element affects accident occurrences is shown hereunder. Deaths. Causes. (-------A------- No. Percent. Danger inherent to work or misadventure 432 ... 58 1 cable exposed through abrasion of the insulation, three; contact with a conductor (signal wire) made live by its contact with a live cable exposed through abrasion of the insulation, one ; accidental contact with uninsulated live parts of apparatus—(a) with live parts normally exposed, three; (6) with live parts normally unexposed, but improperly exposed when live for adjustment, one; misadventure, one. Overwinds and Rope Breakages. During the year, in the Transvaal, there occurred 58 overwinds or runaways in shafts and winzes. In 14 instances death or serious injury to persons resulted. There were only two cases of overwind or runaway in the other provinces of the Union, neither of which caused serious personal injury. The total of 60 over- winds or runaways is 21 less than in the previous year, while the total casualties are greater, 42 cases in comparison with 37. The most serious of these accidents occurred at the Farrar shaft (55 degs. incline) of the Driefontein section of the East Rand Proprietary Mines on November 8. The man cage, while being raised from 22 station, had to call at 19 station. In attempting to stop there, the driver, who was working with only one drum at the time, lost control and allowed the cage to run down at great speed to the penthouse below 22 level. The engine driver disappeared after the accident, and has not been heard of since. The winding engine was found after the accident to be in good working order. Of the 60 overwinds or runaways (23 of which occurred with electrical hoists and 37 with hoists driven by steam or air) 56 occurred with winding engines licensed for the conveyance of persons ; 57 occurred with the engine in charge of certificated drivers, one with white uncertifi- cated driver, and the remaining two with native drivers. In 50 cases the certificated engine driver was considered to be at fault, there was one case of sudden illness, and in six instances the accident was due to some defect in the winding plant. These cases, together with the three previously mentioned where no certificated driver was present, comprise the total of 60 overwinds or runaways. With regard to the six overwinds or runaways that were adjudged to be due to defective plant, one was due to the jamming of reversing lever, three to indicator chains coming off the sprocket wheels, and in two cases the bridle of the skip broke. Detaching hooks were successful except in one case, where the overwind was at such speed that the supporting ring plate was carried away. The fatal accidents due to ropes, chains, or couplings breaking numbered five, with 10 deaths. These totals show a decrease on those of the previous year, when there were 15 accidents and 19 deaths. In each case it was the rope that broke, and not the chains or coupling. Of the five accidents, one occurred in a shaft, two in winzes, and two on inclined planes underground. In the first case the hoist was licensed for the transport of persons. The other four ropes broke from the following causes : Derailment of skip, rope probably kinked, slack suddenly taken up, rope worn out. The breakages of winding ropes (or their couplings) on plants licensed for the conveyance of persons numbered 12, seven in incline shafts and five in compound shafts. Of the 12 cases, 11 of which refer to the winding rope itself, only one resulted in casualties. Three were caused by overwind or runaway, six were due to derailment, jam, or collision, in shaft or tip, and one was due to the rope jumping off the sheave. The other two were instances of worn-out ropes, for which the resident engineers were held responsible. In addition io ihese cases of fracture, six winding ropes were seriously damaged owing to overwind or runaway. There were 14 breakages of winding ropes used exclusively for the raising of minerals, due to causes similar to those above mentioned. Mining Machinery. No particulars respecting machinery for 1914 have been collected, but it is stated that £1,018,285 was expended on new machinery during the year. The most important items comprise stamp mills and tube mills for the new mines on the Eastern Rand, winding plants for these mines, electric winders for other mines, and increases in the electric plant at central power stations. The actual number of rock-drill machines in com- mission on the Witwatersrand gold mines during December 1914 was 9.952, of the following types:— Large reciprocating piston machines. 5,115; small ditto, 2,446 ; air-feed hammer machines, 1,925 ; hand hammer machines, 466. The following ta ble shows the number of coal cutters in use in December 1914, the class of power employed, and the percentage of mining work accomplished by machines over the year :— No. of machines. Percentage -----a_.--------A of wor]j- done Compressed T f -1 to total ton- air.------------‘ nage mined. ... 293 ... 293 ... 63 86 — ... 4 ... 1446 13 ... 13 ... 1995 ... 122 ... 163 ... 56-85 ... 428 ... 473 ... 57 78 ... 433 ... 458 ... 5630 hoists licensed for transport of persons continues to increase. At the end of the year there were in operation 103 induction motor hoists with an aggregate horse power of 53,769, and 23 Ward- Leonard hoists with an aggregate horse-power of 25,575, The use of electrically-driven machinery continues to extend. In 1914, 451,988,177 electrical and 121,014,096 compressed air units were used for mining purposes. This refers to purchased power and does not include the outputs of power stations on the mines. The number of prime movers in 1913 was 7,349 (859,998 indicated horse- power), exclusive of 5,822 motors (298,123-horse power) - Elec- tricity. Transvaal ......... — Cape .............. 4 Orange Free State ... — Natal.............. 41 Union of S. Africa 45 1913............ 25 The number of electric Total .......... 58,077... 46,215...585,408...399,647 The following shows the values of prime movers other than electrical :— August. Jan.-August. 1914. 1915. 1914. 1915. £ £ £ £ Rail locomotives ....210,260...297,326...2,641,584...1,788,221 Pumping ............. 22,741... 14,585 .. 335,298... 318,263 Winding ............. 1,078... 2,801... 23,544 .. 12,036 Defective plant or material............ 9 ... 12 Fault of injured person— Carelessness ..................... 45 ... 6'0 Ignorance ....................... 15 ... 2’0 Disobedience to orders ............ 28 ... 3’8 Fault of management ................ 29 ... 3’9 Fault of gangers ..................... 106 ... 14‘3 ....................... Fault of others......................... 51 ... 6’9 Joint fault ........................... 28 ... 3’8.............. Last year there were nine separate accidents in con- nection with electrical plant at mines, causing four deaths, classified as follows : Direct contact with a live