February 8, 1918. THE COLLIERY GUARDIAN. 275 ____________________________________________________________________________________________________ maximum distance of pull was first ascertained, the new position of the head and return end were then measured, and this was chalked on the roof. The belt was then uncoupled, rolled up, and pushed between the timber to the approximate position, the head and return drum were placed in the exact position, and the belt was coupled up and tightened. The belt was then set in motion in order to ascertain whether it was running in line, and any slight adjustment that was necessary was made.. Machine-cutting was quite satisfactory so long as cutting, filling, and pull- ing took place in different shifts. The belt was cut into 20 and 25 yd. lengths, and this shortened the through well-designed worm-gearing gives a very high efficiency and absolute silence. The average power taken by a 100 yd. belt con- veyor seldom exceeds 4 electric horse-power. The power required depends only on the length of face and the gradient, the actual load on the con- veyor making very little difference. The most satisfactory compressed air drive for a belt conveyor is by means of an air turbine. This combines a compact power unit, but being a com- pressed air machine, it is not as efficient economically as an electric drive, the air consumption being from 140 to 200 cu. ft. per minute. Fig. 16.—Two Conveyors Delivering on to One Mothergate, with Auxiliary Haulage. Fig. 18. Figs. 17 and 18.—Arrangement oe Belt and Shaker-Conveyor. The compressed air shaker conveyor uses the com- pressed air to the best advantage. Air is admitted for the forward stroke, and the weight of the troughing is utilised for the return stroke: as the number of strokes per minute averages 60, the air consumption is small. Owing to the intermittent working of the engine, actual air consumptions are difficult to obtain, but from figures obtained at a pressure of from 40 to 60 pounds per square inch, the air consumption varies from 70 up to 110 cu. ft. per minute. A comparison of these two types of conveyors shows that the most successful installations of shaker con- veyors have been in seams ranging from 20 in. to 6J ft., and where the gradient has been in favour <*f the load. The belt conveyors have been used chiefly in seams from 20 in. up to 4 ft. where the gradient has varied from 1 in 10 against the load to 1 in 10 in favour. The shaker type of conveyor is either a great success or a failure; whereas the belt conveyor is usually successful, as it will operate under conditions where a shaker would fail. > The following comparison was recently given by a colliery manager from actual experience between an electric shaker and a belt c< nveyor operating under the same conditions: — Belt Conveyor. Takes 2 men 2 hours to flit By reversing the conveyor, timber may be sent into the face ____________ The loader controls the conveyor and the tubs Requires two roads ...... Electric Shaker Conveyor. Takes 4 men each shift to flit. 1 man required to carry timber into the face. Nearly one man’s work to look after the gearing. Requires three roads, one of which is a blank gate in the middle of the face, to allow of the gearing to be kept there. time in pulling up by three hours or more, as it was impossible to remove the timber on account of the bad roof. No. 1 conveyor conveyed 33,000 tons of coal in a year and four months, and No. 2 conveyor 25,000 tons in one year and three months. But these faces gave very poor results for the first four or five months. No. 3 conveyor conveyed 17,000 tons in eleven months. The largest output on a belt in any one day of 10 hours has been 140 tons of hand-hewn coal. The reverse is the case with the shaker type of con- veyor. The electric drive consists of a motor attached to gearing for converting the rotary motion into reci- procating motion. The size of motor required for this purpose varies from 12 up to 30 horse-power in certain circumstances. Most of this power is absorbed in the gearing in the conversion from rotary to reci- procating motion. On the other hand, belt conveyors were tried in Lan- cashire in a case where the gradient is 1 in 3, but an electric shaker was found more satisfactory. A large amount of ripping was done, and the rock was stowed in the gob. It was found impossible with the belt conveyor to check the pieces of stone when stowing, even with planks nailed across, but with the shaker conveyor chains were attached to each side of the con- veyor to check the travel, and a throw-off plate was fitted. It was there found that the stones were dis- charged well into the gob. A combination of the two types of conveyors is sometimes an advantage, as shown in figs. 17 and 18, in which two 100 yd. face conveyors in a seam 3 ft. 3 in. high discharge the coal on to a belt conveyor which delivers it up the road against a gradient of 1 in 10. This equipment will shortly be at work. Installation. The lay-out of the haulage and also of the con- veyor face before the installation of the conveyor has a great deal to do with the success or failure of the installation. For example, with a hand-worked face the installation of the conveyor may mean an altera- tion of the timbering, as a space of 2± ft. wide and free from timber is required for the conveyor. It is also necessary to have a space not less than 2| feet wide from the belt or trough to the coal face, to enable the men to work when the conveyor is running. If a less space than this is allowed, and shots are fired in the coal, the belt rollers or roller paths are liable to be buried, causing trouble when the conveyor is started up. The conveyor face must be kept in a straight line, otherwise the conveyor will be close to the face at one point and a considerable distance away somewhere else. Cases have occurred where too much roof has been exposed, thus causing it to break away and bury a part of the conveyor. The question of adequate arrangements for haulage is perhaps the most important. It must be kept clearly in mind that the conveyor should not stop during the filling shift, the reason, usually, for a stoppage being the shortage of tubs. Where possible, the empties should stand in a position where there is a slight gradient in their favour, so that the full tub can be knocked out by the empty tub with- out stopping the conveyor. One of the advantages of conveying is the concen- tration of output; but if the means of disposing of this output are not there, it is useless to consider the question of conveyors until this has been obtained. It would be interesting to know what is the limit to the time in which a single youth can handle the loading from a conveyor. As far as the author’s experience goes, one 10 cwt. tub in about 20 seconds appears to be the limit. In the case of a gate conveyor delivering a large output from the faces, it would be advisable to put in tub-stops. Conveyors can be built for any reasonable capacity, but the difficulty in moving the coal by means of tubs limits the present day output per conveyor to about 50 or 60 tons per hour, provided that the supply of empty tubs is maintained. Exceptional cases occur where the output is even greater where shaker con- veyors are employed and where the gradient is in favour of the load. In the installation of compressed air shaker con- veyors greater efficiency is obtained by placing a receiver as near as possible to the coal face for balanc- ing purposes, owing to the air demand being intermit- tent, and this is absolutely necessary in cases where the air pressure is low. APPENDIX I.—Conveyors in use at Lancashire Collieries. S £ 1. 2. 3. 4. 5. 1. 2. 3. 4. 5. 6. 7. Height of seam. 5 ft. and 3i ft. 3 ft................ 2 ft. 4 in. ..... 2 ft. 11 in....... 4 ft. 9 in. ..... 2 ft. 10 in. 2 ft. 11 in. 2 ft. 9 in. to 2 ft. 11 in. 3 ft. 3 in. ..... 2 ft. 11 in. . 3j ft. .......... 2 ft. .......... Inclination of seam. 1 in 3 in favour of conveyors. 1 in 3 in favour of conveyors. 1 in 6 in favour of conveyors. 1 in 10 in favour of conveyor. 1 in 4 in favour of conveyor. Drive of conveyor. Whether hand or machine-cut. Output per man before and after the use of conveyors. Net saving in cost per ton. Comparisons Between Belt and Shaker Conveyors. The belt conveyor is most economical when driven by electric power, as the rotary motion of the motor is maintained throughout. The reduction of speed Cross-arm drive; air-engine (shaker- conveyor). Electrically - driven shaker-conveyor. Shaker - conveyor ; cross - arm and side - drive ; air- engine. Shaker - conveyor ; cross - air drive ; air-engine. Shaker - conveyor; direct - drive air- engine, fixed under trough. Machine-cut Machine-cut Hand-holed... Machine-cut Machine-cut APPENDIX II.—Conveyors in 1 in 18; con- veyors d e 1 i- vering up and down this gradient. in 10 in favour of conveyor. 1 1 in 10 in favour of conveyor. 1 in 18 in favour of load. 1 in 15 in favour of load. Level ......... Level ......... 3|tons before, 9tons after; 1| tons bef or e, 5| tons after. 2| tons before, 7 tons after. 3 tons before, 4|tons after. 3 tons before, 6| tons after. 4|tons before, 11 tons after. use at Yorkshire Collieries. Approx. 3d.* See note f No saving. Men preju- diced against conveyors. Not available Not available Spiro-turbine a i r- motor (belt con- veyor). Air - engine ; cross- arm drive (shaker- conveyor). Shaker - conveyor; cross-arm drive; air-engine. Shaker - conveyor; side - drive and cross-arm drive; air-engine. Shaker - conveyor; side-drive ; air- engine. Shaker - conveyor; direct drive; coupled under the troughs; air-, engine. Electric drive (belt- conveyor. Machine-cut.. Machine-cut.. Machine-cut.. Hand-got ... Machine-cut Machine-cut Machine-cut Average 10 tons after the use of conveyors. 3| tons before, 8 tons after. 3 tons before, 7| tons after. 3 tons before, 6 tons after... 3| tons before, 6| to 7 tons after. 1*47 tons before, 4*70 tons after. Not available. Approx. 6d.t Approx. 5d.§ APPENDIX III.—Conveyors in use in Other Districts. 1. 2 ft. 10 in Flat Air - engine; cross- Machine-cut.. 2| tons before, 6 tons after.. 9d. 2. 2 ft. 7 in Flat arm and side drive. Air - engine; cross- Hand-cut 3’6 tons before, 7 tons after Is. 8d. 3. 2 ft 1 in 6 in favour arm drive. Electric - belt con- Hand-cut 7 tons per man with con- 2s. 6d. 4. 1 ft. 7 in of conveyor; 170 yd. face. 1 in 10 in favour veyor. Electric - belt con- Hand-cut veyor. lj tons before, 4» tons after 2s. 6d. 5. 2 ft. 2 in; of conveyor. 1 in 5 in favour veyor Air-engine; direct- Machine-cut.. 10 tons per man Is. 2d. of conveyor. drive shaker. i to 3s. Larger coal and less face-room required for larger output by installation of conveyors. f Faces could not be worked except by conveyors, owing to inclination and bad roof, which becomes better owing to rapid advancement by installing conveyors. X But better coal is filled on to the conveyor than would be filled into tubs ; the men also are more satisfied when filling on to the conveyor. § Better size of coal obtained, and roof controlled easier by moving evenly and often after conveyors were installed.