1330 THE COLLIERY GUARDIAN. June 25, 1915. CURRENT SCIENCE AND TECHNOLOGY. Characteristic Curves for Centrifugal Pumps. In a paper published in the Journal of the Western Society of Engineers (vol. xix., 8), Mr. F. W. Greve, junior instructor' in hydraulics, Purdue University, deals with the subject of characteristic curves to illustrate the performance of centrifugal pumps, so as to provide a basis of com- parison. One of the curves prepared by the author shows the relation between the head in feet and capacity in gallons per minute at constant speed. As might be expected, the head decreases with increase of capacity (except for small discharges), but the curves show that the maximum head does not occur at the minimum discharge, but at a point equal to about one-third of the CA&i&Ty w cpm -100 A CENTRIFUGAL PUMP CABACITY-HEAD—ISO-LEFICLENCY- CJJfiYES. , J constant srlld. SO SO 7d 60 50 * IS LO /5j? /2O UO /no SO SO 70 SO 50 40 50 20 /O ■150 120 maximum. On the same diagram, curves of horse- power input and output and efficiency are also plotted. An important fact is that the curves are parallel or con- centric, thus enabling a new curve to be sketched in for the desired speed. Up to a certain limit, variable for each size or make of pump, the maximum efficiency and capacity are found to increase with an increase of speed; the point of maximum efficiency moves to a point of greater capacity as the speed is increased. Testing Hammer Drills. A paper was recently read before the American Insti- tute of Mining Engineers by Benjamin F. Tillson, in which the author gives an account of the methods of testing hammer drills adopted by the New Jersey Zinc Company at its Franklin mines. The device adopted consists of a water-displacement air meter, comprising' two tanks half-filled with water, and made of 12-in. pipe with blank flanges, gauge glasses being mounted on one, a four-way cock connecting the compressed-air supply pipe with both tanks and the air line going to the drill. A summary of tests of representative drill types is given, which indicates the improvements in hammer drills during four years. In determining the relative merits of rock drills, the logical basis is one of cost. This the author terms the “ factor of desir- ability it is equal to the drilling speed, in inches per minute, divided by the power consumption, in cubic feet of free air, per inch drilled. The drills made during 1909 covered most of the well-known American makes of hammer drills at that time, and about 4% in. and 5 in. were the highest drilling speeds obtainable at about 90 lb. pressure, and with an air consumption of 60 to 90 cu. ft. of free air per minute, and for various drills the “ factor ” varied from 0-09 to 0-41. The advance is shown by examining the tests carried out during 1913 Symbol . for drill. Rotation. Control of piston. Style of feed. Shape of bit. Free air (cu. ft. p. m.) Drilling speed (in.p. m.) Free air per in. drilled. Factor. Px Hand Valveless... Dia. air... Raised crux 55’8 10’76 5’18 2-080 PT Do. Do. Do. ... Do 59’5 11 03 5’40 2’043 P, Do. Do. Do. ... Do 56-8 9’32 6’10 1’529 PT Do Do. Do. . . Flat crux 57’1 7’98 7’17 1'110 Q Auto rifle*.. Valve Rev. air... Raised crux 51’4 6-12 8’3.-) 0’730 Q Do. Do. Do. ... Double chisel 48’2 8T8 5’90 1’388 R Do. Do Do. ... Raised crux ’ 112’0 6’85 16’25- 0’421 R Do. Do Do. ... Flat hex 102'2 7’50 13’63 0’550 * Automatic rotation caused by a piston reciprocating as though it were controlled by a rifle bar. The air was measured by displacement of water; the rock was white crystalline limestone; the gauge of bits was lyj- to 1| in. The author discusses the physical phenomena relating to the process of drilling; the factors influencing the transmission of the kinetic energy of the piston to the rock; and other considerations entering into the per- formance of the drill. He also deals with the question of maintenance. Summarised, he finds that from 1910 to 1913 the cost per foot has been reduced as follows :— 1910. 1911. 1912. 1913. Dois. Dois. Dois. Dois. Drifting 5’33 .. . 4’92 .. .. 3’35 .. .. 2’70 Raising 2’95 .. . 2’31 .. . 1’88 .. .. 2’22 Storing Coal Under Water. A novel coal storage plant has recently been erected by the Indianapolis Light and Heat Company, of Indian- apolis, Indiana, in which provision has been made for submerging the coal under the water to prevent spon- taneous combustion. The plant has a total storage capacity of 30,000 tons, and provides against coal shortage due to strikes at the mines or on the railroads, and to car shortage on the railroads. The plant consists of a large concrete pit, 300 ft. long by 100 ft. wide and 28 ft. deep. It is 18 ft. below ground level, having a 10 ft. wall rising above the ground. Below the ground the wall slopes at an angle of 45 degs., this being done only to reduce the cost of construction. This makes the pit 72 ft. wide by 272 ft. long on the bottom. The concrete is from 12 to 18 in. thick, and is reinforced throughout with twisted | in. square rods to withstand any pressure from water that may rise in the gravel around the pit. Through the middle of the pit lengthways there is a row of concrete piers placed 15 ft. centres. These piers support a trestle, on which there runs a standard gauge track. A standard 15-ton Brown- hoist locomotive crane travels back and forth on this trestle, handling the coal on both sides with a Brown- hoist 2-yd. coal grab bucket, suspended on a 40-ft. boom. The crane and bucket are operated by one man from his stand in the cab. Being self-propelled and equipped with master car builders’ trucks, couplers, and steam brake, the crane does the switching of the cars off and on the trestle. The coal cars are run out on the trestle with the crane and dumped. And when the coal is required in the power house it is loaded into cars by the crane, and carried to the boilers. Forty-pound rails are embedded in the bottom of the pit, on 18in. centres, with |in. of the head standing above the surface of the concrete. When the grab bucket is working on the bottom of the pit, the rails prevent the bucket from striking the concrete. The pit is filled with water up to the ground level, and covers 13,000 tons. The water is pumped into the dit by a 4 in. centrifugal pump, taking the water from the power house supply well, and the water enters the pit at the' ground level. Through the centre of the pit, and beneath the trestle, there is a trough 12 ft. wide and 1ft. deep, which serves as a drainage. It is fitted with a drain pipe, which carries the water to either of two manholes—one at each end of the pit. The outlet openings are protected by gratings to prevent any coal from entering the drain pipe. Clinkering of Bituminous Coals. The Science Abstracts contains a summary of a paper on “ Laboratory Tests for Clinkering of Bituminous Coals,” contributed by F. C. Hubley to the Engineers’ Club-of Philadelphia (Proc. 32, pp. 35-85, January 1915). The paper describes a new method and apparatus for carrying out fusion tests on the ash of coal. As regards the need for a new method of making such tests, the author states that while the cone method appears quite feasible, and in two years’ actual use in a commercial laboratory was productive of definite results, the length of time required to carry out the test, as well as the personal equation of the operator entering into the judg- ment of results obtained, prevented this test from becoming a standard one. In attempting to devise a more rapid and accurate method, it occurred to the author that if a sample of ash be formed into a hard pellet under considerable pressure, and this pellet be placed in a furnace under a very slight compression, the variation in thickness of the pellet under a steadily increasing’ temperature would be a measure of the rate of softening at any temperature. In order to perform such a test, an instrument called the fusiometer has , been devised. In experiments carried out by the writer, a gas heated furnace was used. The carbon is pro- tected for a part of its length from the direct action of the flame by a porcelain tube. When this method of heating is used, the carbons slowly reduce in diameter, and from time to time must be replaced by fresh rods. From six to eight tests may be completed with one pair of rods, without excessive reduction of the rod diameter. Temperature measurements are made with a Pt-Rh thermo-couple. The porcelain protecting tube for this couple is placed so that the couple bead is in close proximity to the ash pellet. With the ash pellet and carbons in position, and the pointer “ V ” adjusted midway between zero and 1-00 on the scale, the furnace is gradually heated up at the rate of from 50 to 100 degs. Fahr, per minute, simultaneous temperature and scale readings being made at half-minute intervals. As the heat is increased, negative movement of the pointer will indicate carbon expansion up to a temperature where the first softening of the ash pellet is indicated by a positive movement of the pointer. The experi- ment is continued till the final collapse of the pellet is indicated on the scale. These results, if plotted—the temperatures as abscissae, and the scale movement as ordinates—produce a curve, an ordinate of which at any point is a measure of the relative rate of softening of the ash pellet at that temperature. This curve is parallel to the temperature axis at the first softening of the ash, becoming parallel to the scale axis at or near the melting point, thus giving a diagram of the complete fusing range of the ash under test. In summarising the results obtained by this method of examination the author states that :— (a) To grade coals properly as to their steaming value, it is just as essential to perform a fusion test on the ash as it is to make a calorific determination of the coal; (b) if 2,700 degs. Fahr, or over is specified fpr the ash fusion, and this figure is strictly adhered to in pur- chasing coal, the buyer will be protected from excessive or troublesome clinker formation in the boiler fires. If the lower temperature is specified, viscosity of the melt as well as temperature of fusion should be considered, keeping the former as low as possible; (c) the curve developed from the fusiometer indicates : (1) fusing range, (2) melting point, and (3) relative viscosity of the melt; (d) in ash fusion, long softening is gener- ally accompanied by high viscosity; (e) the cone method for determining the fusing point of ash, while being fairly accurate, cannot be put into general use on account of the length of time and labour required pro- perly to perform such a test; (/) on account of the multi- plicity of possible combinations of the ash constituents in the original coal, the ultimate analysis of the ash can give only an approximate idea of the possible clinkering qualities of a coal. THE GERMAN AND AUSTRIAN COAL AND IRON TRADES. We give below ’further extracts from German periodicals that have reached us, showing the course of the coal and iron trades in Germany and Austria:— Iron Market in Rhenish Westphalia. On the whole the works continue to be fully occupied and the demand is extremely brisk, so that prices keep firm and in excess of the rates fixed by the Conventions. The nature of the demand has, however, changed to some extent, war material figuring more prominently because other products are in smaller request as a result of the increased prices, whilst the Italian crisis is causing merchants and consumers to hold back. Italy had been buying freely before entering on hostilities, and the cessation of these orders will considerably relieve the home market. The chief raw materials have gone up and a further advance is expected, in which case the finished products will necessarily follow suit. The only way to ease the situation in this respect would be an increase in the amount of labour available, the future state of the market being entirely a question of labour. In the ore market the position remains unchanged, the mines having as much as they can do to satisfy the demand anything like completely. The Siegerland Ironstone Association has not put up its rates any further at present; but sales for the second half of the year have not yet been commenced, no agreement as to future prices having been reached. For the moment Siegerland raw ore is quoted at 13’80 to 14’20 mk., and roasted ore at 21’50 mk. per ton. Nassau red ironstone has advanced from 18’50 mk. to 19 and 19’50 mk.; minette costs 4-4’20 mk. per ton, but the former specifi- cations as to iron content are no longer strictly main- tained. Haematite ore sells at 46-48 mk. The demand for pig iron is very active, and taxing the resources of the works. Exports are confined to Luxemburg pig, which fetches better prices among neutrals than in the home market, and it is in good request as being cheaper than English pig. Prices in the home market are likely to advance again shortly, especially for haematite iron and other high grades. On the other hand, the scrap market has weakened, the fear of scarcity having proved unfounded. The abundance of the supply is largely due to the fact that more scrap is produced in making war material than in ordinary industrial products, whilst a good deal of war scrap is coming in from the fronts, and the railways also are sending in large quantities. Prices have therefore receded, so that heavy broken castings can be bought for 70 mk. per ton, machine castings scran for 78 mk., cast and wrought iron turnings 44-45 mk., railway shop turnings 45-46 mk., and lighter material 42’50 mk. Core scrap is selling is 55 mk., railway repair shop scrap at 58-60 mk., fresh heavy scrap at 62-63 mk., and lighter at 58-60 mk., all delivered at works. In semis there is little change, prices remaining as before, with 15 mk. extra for open-hearth material. The stoppage of exports to Italy will be felt, especially by the basic works. In other respects the home and foreign demand is maintained. Makers wish to advance prices in order to cover the higher cost of raw material, and as soon as this point has been settled, sales for the third quarter will commence. In the bar iron market, enquiries have quieted down a little, but delivery specifi- cations on old contracts come in regularly, and the works have so many orders in hand that they stipulate for pro- tracted delivery in cases of new business. The Convention prices are being exceeded, especially for, small parcels for early or prompt delivery, both for home and export. Ordinary bars sell at 140-145 mk. and more, net cash, ex-works; structural iron at about 155 mk.; universal iron at 140-145mk.; even higher rates being obtained for export. Welding iron, rivet iron, chain material and horseshoe bars are in active request. Inland business in girders and sections is stagnant, but neutrals are buying as usual, owing to the difficulty of obtaining supplies from England except at higher prices. For the time being, girders are fetching 120 mk. ex-Diedenhofen, with the customary differences for zonal delivery and commercial discounts. The tube market is rather quiet, but the Convention prices are maintained. The course of business in the plate market is, in the main, in correspondence with the movements in in the bar iron market. The demand keeps ahead of the supply, and prices are firm, the Convention rates being taken as minimum. Thus the rate of 140 mk. for heavy plate, ex Essen. Siegen or Dillingen, is considerably exceeded, about 145 mk. being obtained in the home market and 155 mk. for export; ships’ plates fetch 147’50 mk. and up to 165 mk. respec- tively ex Essen; and more than the fixed prices of 155 mk. and 165 mk. is being obtained for boiler plate. A very active demand prevails for fine plate, large quantities of which are required for war material, and