468 _______________________________________________________________________________________________________ THE COLLIERY GUARDIAN. September 3, 1915. a general way describe the Alley and MacLellan machine as adapted for a steam drive, but machines of their design specially adapted for a motor drive have also been supplied largely, and one of these is shown in the second photograph. Generally, it will be noted, such com- pressor is simply a steam-driven machine, lacking the steam cylinders and distance pieces, and this, it will be at once noted, makes a very compact and substantial motor-driven set. So far as the details, that is, the air cylinders, inter-coolers, valve gear in air cylinders, lubrication, are concerned, the above remarks as applying to the steam-driven compressor can also be taken as holding good for the motor-driven air com- pressor. When the question of the controlling—that is, the automatically adjusting of output of these large motor-driven sets to meet the fluctuation in demand in collieries or other large users—is considered, the methods are much more varied. In some collieries, even for units up to 400-horse power, electric automatic starting and stopping gears have been fitted; thus, when the pressure rose to a pre-determined point, both motor and com- pressor are stopped down until such time as the pressure again falls, say, 5 or 101b., whatever is determined upon as a reasonable allowable drop. The machine is then started up, and care is taken in the design and class of automatic gear supplied to ensure that when the machine is started up no excessive rush of current will be neces- sary, such as is not permissible sometimes in electrical systems. In other instances no such stopping and starting gear is supplied, the motor being a constant speed machine, and the controlling carried out entirely by opening or closing the air inlet to the compressor, this being done by the rise and fall of pressure in the system. The same result is obtained, of course, as in stopping and starting of the machine automatically, but there is always a continuous loss of power in having a large compressor or motor running round even light, as the light load does in some class of compressors represent somewhere about 40 per cent, of the full load power, although in the Alley and MacLellan class of machine, under such conditions, it has been possible to reduce this light load power down to a matter of not more than 20 per cent, of the full load. A special duplex class of air control is fitted, and it is only by its use, and more especially in this design of machine, that the full advantage of this controlling gear can be had. It will, therefore, be noted that there are open to any purchaser who may desire to instal electrically-driven compressors in collieries, one or two methods for the controlling, and it is only when a clear conception of the local conditions is obtained that it is possible to determine the best design to suit the local requirements. Experience which covers the whole of the period from the start of air-compressors being electrically driven goes to show that where, five, six, or ten years ago, it was very common to see electrically-driven compressors gear driven from motors, such method of drive has now practically ceased in all the newer installations. This, at any rate, may be taken as a fact so far as units ranging from 100-honse power upwards are concerned. An air-compressor is certainly not adapted for gear driving. First of all there is a continuous loss in power, which at the minimum must be accepted as about 5 per cent, of the full load power. Secondly, there is, and must always be, found necessary renewals of gearing, whether it is in the first year or in ten years; the gearing must wear out in time, and, further, there is the con- tinual noise and vibration accompanying a gear drive, that is, in making a comparison with a similar size of plant when direct coupled to a motor where no gearing intervenes. Thus, it may be taken that all present-day installations of the sizes mentioned are generally direct coupled to their motors, the flywheel on the air-compressor acting as one half coupling, and either a solid or flexible half coupling being fitted to the motor shaft. In the largest units where no combined bedplate is installed, the flexible type of coupling is sometimes adopted, but in smaller units of, say, 2,000 or 3,000 cu. ft. capacity, it is even quite common to have solid couplings and two-bearing motors, or even single- bearing motors and a combined bedplate carrying both motor and compressor. The third and last type of air compressor that may be mentioned, which, after all, is common in every respect to the motor-driven machine, is the air com- pressor direct-coupled to gas engines. This type of machine is similar to that supplied for direct coupling to an electric motor, with the difference only that no fly- wheel is fitted to the shaft, a half-coupling being fitted to the compressor shaft, and the flywheel fitted on the gas engine shaft. There is also a special class of con- trolling gear and other small details in construction, but to all outward appearances and in general operation the machine would be as stated, similar to those for electric drive. It is, however, interesting, and certainly not common practice, to have larger units of this size gas engine driven and installed by a colliery company. In fact, gas engines so far have not found considerable favour with collieries, and it is interesting, and may be the forerunner to quite a number of similar plants being installed, and in this respect is worthy of notice. Coal Mines Inspection in 1914. YORK AND NORTH MIDLAND DIVISION. Mr. Thomas H. Mottram, in his report on mines under the Coal Mines Act, 1911, in the York and North Mid- land Division for the year 1914, states that the mines and other works employed during the first seven months of the year 274,196 persons, but owing to the outbreak of war and the consequent enlistment in H.M. Forces of considerable numbers of workmen, the persons employed at the end of December had fallen to 248,503. Owing to the war, the output, which otherwise would have been a record one, fell to 76,211,812 tons, and was therefore 6,286,562 tons less than that of the preceding year; the value of the minerals at the mines and quarries was approximately ^31,365,999. War operations on the Continent practically stopped the importation of timber, and for a time the collieries had to be supplied from stocks previously accumulated. After a time, however, additional supplies were obtained, but owing to high freights and scarcity of imports, the prices of timber rose as much as 40 and 50 per cent. This led to conservation of stocks at many mines by (1) exercising more attention to the withdrawal and re-use of timber from underground goaves, and (2) the using of steel supports. In some cases home-grown timber was also introduced as a temporary expedient. In this way all the pits were amply supplied with roof supports, and the stocks of timber are now being fairly well main- tained. Mining developments are still going on in different parts of the Division. In the Doncaster area, Rossing- ton, Thorne, and Hatfield undertakings are progressing, but the Harworth enterprise, controlled by the Northern Union Mining Company Limited, and financed by German capital, is now standing. The freezing process was in operation till the end of July, but was stopped on the outbreak of war, when all further operations were discontinued. Satisfactory progress has, however, been made at Earl Fitzwilliam’s new sinkings at Raw- marsh, near Rotherham, and also at Welbeck, in Nottinghamshire, and at Ruff ord, in the same county. These new undertakings should, along with underground developments at some of the newer collieries, maintain at a high figure the output capacity of the Division for many years to come. During the year 2,322 underground visits were made by the inspectors of mines, and 306 by the horse inspector, who visited 201 separate mines, and inspected 11,408 horses. The total number of underground inspections made in the Division was 2,628, and 1,055 quarries were visited. Persons Employed. The total number of persons under different ages employed in and about the coal mines and stratified mines of ironstone and clay under the Coal Mines Acts at the end of 1914 was 235,177, as compared with 257,252 in 1913. The figures up to the end of July were 260,870, showing a reduction of 25,693 due to men belonging to the Reserve being called up to serve in the Army, and to enlistment in H.M. Forces since the out- break of war. The persons employed in the Yorkshire and North Midland Division number 23 per cent, of the whole number employed in the United Kingdom. The following particulars relate to coal cutting by machinery :— N umber Statute tons driven by cut by Description Disc.......... Bar .......... Chain ........ Percussive____ Rotary heading ....... Elec- Com\ tricity. 175 ...1,531,152...2,120,180 60 ... 971,684 .. 894,594 35 .. 1,051,455... 397,574 99 ... — ... 158,983* 6 ... 2,119... 5,398 157 . 87 .. . 104 . 2 Persons employed. Elec- Com- tricity. ^rsed Total in 1914......... 350 ... 375 ...3,556,410.3,576,729* Total in 1913......... 331 ... 342 ...3,922,682...3,685,848f * Including 26,732 tons of fireclay and 275tons of ganister, f Including 8,694 tons of fireclay. The number of conveyors employed at the coal face was 116, as compared with 86 in 1913. Accidents. During the year notice was received of 1,435 acci- dents. Of these 204 proved fatal to 219 persons, the remaining 1,231 being non-fatal accidents, which caused injury to 1,284 persons. The death rates per 1,000 persons employed, based on the number of persons employed at the end of July, were as under :—Below ground, 0-92, in preceding year 1’25; above ground, 0-51 (0-68); above and below ground, 0-84 (1*13). Illus- trated in another way, one out of 1,081 persons employed below ground, one out of 1,938 persons employed on the surface, and one out of every 1,191 persons employed in and about mines lost his life by accident. The county death rates from all accidents per 1,000 persons employed above and below ground were :—Derbyshire, 0-78, in preceding year 0-79; Nottinghamshire, 0*65 (1-25); Yorkshire, 0-90 (1’21); Lincolnshire, nil (nil). Compared with the previous years, deaths from explo- sions show an increase of 10, due to the Wharncliffe Silkstone disaster, in which 12 persons were killed; deaths by falls in mines, a decrease of 51; deaths by shaft accidents, a decrease of 22; deaths by miscel- laneous underground accidents, a decrease of 1; deaths by surface accidents, a decrease of 8. It will be seen that last year the death rate per 1,000 persons employed showed a decrease of 0-29; and a decrease of 0-70 per 1,000,000 tons raised. The following is a summary of fatal and non-fatal accidents, classified according to place and cause :— Non-fatal accidents reported to __________ Place and cause. Underground— Explosions of fire- damp or coal dust Falls in mine ..... ........ Shaft accidents ... Miscellaneous under- ground .......?.. All non-fatal accidents disabling for more than 7 days. Fatal acci- dents. eg CD A 2.. . 13... 100.. .103... 7.. . 7... 68.. . 68.. 12... 18... 7... 11 512.. . 516... 12,549... 12,600 20 .. 57... 77... 109 527.. . 530...21,620...21,638 Total underground 177...191...1,071..1,121..34,253...34,358 On surface ...... 27... 28... 160... 163... 3,108 .. 3,111 Mines County. at work. Derby............ 112 Lincoln .......... 1 Nottingham....... 37 Yorks (W. Riding)... 322 Below Above ground, ground. (----------A------- Males. Males. ... 44,571 ...10,843... 4 57 ... 26... — ... 32,684 ... 8,334... 2 ...129,291 ...35,013... 15 Below and above ground. ... 55,418 83 ... 41,020 ...164,349 Total in 1914 ... 472 ...206,603 ...54,246... 21 ...260,870 Total in 1913 ... 635 ...203,996 ...53,238... 18 ...257,252 Output of Minerals. The total output of minerals from mines working under the Coal Mines Acts was 67,374,083 tons. In last year’s report there were 23 separate colliery com- panies in the Division, producing 1,000,000 tons per annum. Owing to reduced output consequent upon the war there were in 1914 only 19 companies with a yearly output ranging from 1,000,000 to 2,550,504 tons. The following table shows the quantity and value of mineral raised :— Gross total in 1914 204 ..219...1,231...1,284...37,361...37,469 Total in 1913...... 260...291... 1,369 . 1,407...40,280...40,354 * Includes (a) accidents causing fracture of head or limb, or dislocation of limb, or any other serious personal injury; (6) accidents caused by explosion of gas or dust, or any explosive, or by electricity, or by overwinding, and causing any personal injury whatever. f Including those injured by accidents which proved fatal to their companions. Explosions of Firedamp.—The most serious explosion was that which occurred on the afternoon of May 30, at Wharncliffe Silkstone Colliery, near Barnsley, and resulted in the death of 12 persons, and injury to other three. This accident has been the subject of a special report. The only other fatal explosion occurred at the Haigh Colliery, belonging to Messi's. G. Fountain and Son Limited, near Barnsley, on June 22, and by it a deputy, named John England, 59 years of age, received injuries which proved fatal 14 days afterwards. The doctor’s view was that the deceased caught cold at the time of the accident, and that he died from exhaustion due to septic absorption following burns, and from pneumonia of the right lung of a couple of days’ duration. Falls of Roof and Side.—By falls of ground there were 100 fatal accidents and 103 deaths, as compared with 149 fatal accidents and 154 deaths during the preceding year. The decrease in the number of deaths was there- fore 51. Part of this decrease was no doubt due to fewer men having been employed during the last five _____________________________ Hull Coal Exports.—The official return of the exports of coal from Hull to foreign countries for the week ending Tuesday, August 24, 1915, is as follows :—Amsterdam, 686 tons; Bona, 300; Calais, 1,719; Dieppe, 696; Dunkirk, 1,611; Gothenburg, 2,022; Gefle, 2,194; Harlingen, 1,019; Harnas, 1,584; Honfleur, 619; Havre, 749; Rouen, 20,826; Rotter- dam, 2,638; Tuborg, 1,312—total, 37,975 tons. The above figures do not include bunker coals, shipments for the British Admiralty, nor the Allies’ Governments. Corresponding period August 1914, total, 24,190 tons. County. Coal. Fireclay. Ironstone. Other minerals. Total. Derby Lincoln Nottingham. Yorks (W.R.) Total, 1914 ... Total, 1913 ... Tons. 15,754,756 11.510,230 39,542,637 Value. £ 6,894,812 5,030,288 18,268,292 Tons. 34,464 418 313,870 Value. £ 7,417 102 95,324 Tons. 25 54,544 24,229 Value. £ 2 * 26.143f Tons. 2,053 245 106,612 Value. £ 669 98 35,319 Tons. 15,791,298 54,544 11,510,893 40,017,348 Value. £ 6,9(2,900 * 5,030,488 18,425,0781 66,807,623 72,951,841 30,193,392 33.422,308 378,752 344,060 102,843 92,823 78,798 86,645 26,145 29,513 108,910 1 7,213 36,086 39,480 67.374,083 73,499,759 30,358,466 33,584,124 * Included in Yorks. f Including value of Lincoln ironstone.