September 27, 1918. THE COLLIERY GUARDIAN. 653 THE CHANCE ACETYLENE SAFETY LAMP.* By William Maurice, F.G.S., M.I.E.E. In June 1917 the writer submitted some notes on acetylene mine lamps, f and in the course of the subse- quent discussion the desire was generally expressed that something should have been said concerning the present position of the acetylene safety lamp. It was not, however, then practicable to describe anything new, as experiments and manufacture had been delayed owing to the war. The lamp now described presents many interesting features, and although it is not claimed to have reached the final form for regular mine service, it marks distinct progress. It would seem that if a lamp can be designed which will give a much better light than any lamp now in use, and be as safe as other flame lamps, the prime cost and maintenance charges being low, it would merit the close attention of the mining industry. Safety being assumed, the whole question of new lamps turns on the amount of extra light they will give. It is therefore essential that a more satisfac- tory basis of comparison should be adopted. Compari- sons in terms of candle-power convey next to no infor- mation, for of two lamps giving the some photometric candle-power one may be immeasurably superior to the other in practical use. Candle-power tests are nearly always made under laboratory conditions, whereas in practice the illu- minating value of any pit lamp follows a descending curve, which is more rapid in the mine than that due to the inherent defects of the lamp, so that at the end of a shift the value may be only half or a quarter of that with which it started. The new unit of luminous flux, the “ lumen,”! will enable more satisfactory com- parison to be made, but no results can be of much value unless they are determined under working condi- tions and curves are shown for each hour of .the shift. There has not yet arisen an opportunity to deter- mine the lighting value of the Chance lamp in lumens, but as a general indication some figures have been cal- culated on the assumption that oil safety lamps will range between 0-3 and 0*8 candle-power, averaging 0-6, and that electric lamps will give about 0-5 mean spherical candle-power and about 1-2 candle-power across the path of light thrown by the reflector, this path subtending an angle of about 130 degs. On this basis oil lamps will average 7*5, electric lamps 10-7, and the new Chance lamp 37-7 lumens, or about five times the illuminating value of the average oil lamp and three and a half times that of the average electric lamp. This increased lighting value will enable the miner to perform his work under conditions of greater efficiency, will tend to reduce—or, at any rate, to make more inexcusable—the filling of dirt, and will un- doubtedly lessen the risk of all those accidents which, more or less directly, are the result of ineffective lighting. A satisfactory acetylene safety lamp should possess the following qualities: (1) Be strong, and so con- structed as to withstand considerable rough handling without injury or deformation; (2) be simple as to closing and operation; (3) be compact in shape without any projecting parts liable to damage; (4) be reason- ably light in weight; (5) give a better light than any alternative type of lamp; (6) be so designed that it can be inclined or even laid on its side for a few moments without going out or without causing exces- sive production of gas; (7) be self-regulating, so that, once lit, the regulation of the flame does not require attention; (8) be convenient in use, well balanced, fitted with suitable handle or hook, and, preferably, about the same weight and dimensions of lamps ordinarily in use; (9) be capable of detecting inflam- mable gas and deficiency of oxygen, and, generally, comply with the usual official tests for safety lamps; (10) it should generate gas evenly under all ordinary working conditions; (11) it should not be a source of danger in itself, either by liberation of a dangerous volume of unconsumed acetylene or by forcing methane ignitions through the gauze; (12) cost of maintenance should lie within reasonable limits, having due regard to the fact that effective lighting is a source of profit both to owners and miners. The Chance acetylene lamp, which is a combination of the American type of Wolf lamp with the Mueseler principle, adapted to burn acetylene by means of several ingenious advances on earlier practice, can be used to detect the presence of firedamp in the mine air and to indicate deficiency of oxygen. As already seen, it gives considerably increased illumination. It is, moreover, provided with a special roof reflector, which furnishes sufficient illumination of the roof without tilting the lamp, and allows a proper exami- nation to be made. Accidents from falls of roof are probably more often related to inadequate inspection than is generally recognised. Any advantage gained in this direction may thus reasonably be set against the more remote * Paper read before the Institution of Mining Engineers at Nottingham, September 13, 1918. t Trans. Inst. M.E., 1916-1917, vol. liii., page 227. ! The lumen has been defined by Mr. F. W. Willcox as follows : “ The lumen is strictly defined as the unit of luminous flux, and luminous flux is radiant power evaluated according to its visibility—that is, its capacity to produce the sensation of light. The lumen is the unit of the quan- tity of light flowing from a luminous source. The value established for the lumen is the amount of light from a unit source falling upon a unit surface, all points of which are at a unit distance from the source. Assume a source of one spherical English candle, and place this at the centre of a sphere of 1 ft. radius. It follows that the lumen is the amount of light which is falling upon 1 sq. ft. of surface of this sphere. The total area of a sphere with 1 ft. radius is 12-57 sq. ft. As each sq. ft. repre- sents a value of one lumen, there will be 12-57 lumens on the total sphere. It follows from this that the lighting value in lumens of any luminous source is obtained by multiplying the mean spherical candle-power of the source by 12-57.” possibilities of gas-ignition, which apply to all flame safety lamps. Other desirable qualities possessed by this lamp will be easier to recognise after an account of its construc- tion and mode of operation has been given. The upper part follows the construction of the ordinary Wolf- Mueseler lamp, with corrugated shield, double gauzes, and Mueseler chimney. The latter has the usual hori- zontal gauze at the base and protecting disc at the upper end of the cone. The novelties are in the design of the generator and in the use of a special form of burner. Hitherto, the only acetylene lamps which have come into general use have been Wolf lamps or designs based upon these models. The last to be developed, so far as is known, was the Wiede lamp, which itself possessed many points of interest, the chief of which was the provision of a cooler for reducing the tempera- ture of the products of combustion. In all these, how- ever, the mode of producing gas was by the use of superimposed vessels, the upper one dropping water slowly into the lower one, which contained the carbide. In the present model the “ contact ” system has been adopted, with some interesting modifications. In the “contact” system a vessel containing carbide (closed at the top, save for the gas-exit, and closed at the bottom, except that provision is made for the slow percolation of water through it) is immersed in water. Owing to the pressure due to head, the water enters the carbide chamber and thus generates gas. When working, the gas-pressure inside the carbide chamber controls the admission of the water, more or less water being admitted as the gas pressure falls or rises. In the figure the outer shell A (made of cast-aluminium alloy) forms the water-vessel. The carbide container con- sists of the inner cylinders B, B1, the cover B being screwed into the water-vessel from above. Cylinder B is open at the bottom, which is screwed to fit cylinder B1, the latter forming the carbide holder proper. Con- centric with these vessels there is a gas-regulating valve C, operated by the hand-screw D, situated in the base of the lamp. This valve arrangement permits of raking of the carbide by movement of the valve- stem C1 acting through the water-feed tube E at the base of the container. This has been found to be of great use in preventing stoppage of the water-feed. The water attacks the carbide from below, in the manner already explained, and by this means many of the difficulties of drip generation are overcome. The enlargement of the water vessel near its middle, as shown at A1, is for the purpose of securing a more uniform head during the working of the lamp. The spring me- chanism F, on the left of the illustra- tion, is a water filling valve similar to the spring filling valve commonly used on oil safety lamps. The gas generated by the upward percolation of water through the annular space be- tween the stem C1 and tube E passes through the upper layers of carbide, filters through the felt pad D2, and into the burner-tube I by way of the side hole G in the valve- tube. The valve serves to shut off gas or to lower the flame for methane-testing. There is no water valve, the gas con- trol being automatic. When the valve is partly closed the gas pressure increases, thereby pushing back the water into the outer vessel. If the gas-pressure is not sufficiently relieved in this way, water is forced out of the lamp by way of the overflow tubes, of which there are two. One of these is shown at J. It may happen, if the gas pressure is greater than can be counterbalanced by the head of water, or than can be relieved by the overflows, that gas itself will escape by the same means. The orifices have therefore been made to lead into the open air downwards, so that any gas which may be discharged will be delivered as far from the air inlet (which is above the glasses) as practicable. In use, it has been found that the lamp practically never over-generates. Even if it did, it appears to be impossible for such a volume of acetylene gas to escape into the mine air as would form either an explosive mixture in itself or be the means of bringing a methane air mixture which was below the lower limit of explosibility up to danger-point. The brass tube D shown surrounding the valve-stem C, and resting on the enlargement C1 at the base of this stem, is intended to prevent carbide from falling into the water feed tube when the lamp is being charged. During charging this brass tube slips down into the water feed tube E, and is lifted therefrom by the en- largement C1 on the valve stem to the position shown in figure, when the carbide container is assembled in the water vessel. It will be observed that the lamp is not dependent for safety on the presence of a rubber or fibre washer at any point. The gas is water sealed, with the addition of the mechanical seal formed by the screw thread at the upper end of the carbide con- tainer. It is believed that this is the first acetylene I I I I D 1-E Hl I Section of Double-Glass Type of Chance Acetylene Safety Lamp. Line A—A indicates.line of rays reflected to roof. lamp in which washers are not used. The washer between the carbide container and the reflector ring is merely a mechanical cushion, and has nothing to do with the effectiveness or safety of the lamp. A considerable objection to the use of acetylene lamps in the past has been that they may, owing to a little inattention, to concussion due to shot firing, or to air pressure resulting from the sudden closing of ventilation doors, go out. The risk then arises of lamps continuing to generate acetylene which is not consumed and which escapes into the mine air.* On the Continent of Europe, in all the Colonies, and in most of the mining areas of the United States of America, the Wolf internal igniter is used to reignite flame safety lamps. In Great Britain the electrical method of relighting is the only permissible one. The Chance lamp has a specially designed automatic re- igniting burner L, which does not appear to present any of the disadvantages of other means of re- lighting. Advantage is taken of the low tempera- ture at which acetylene ignites, and the Chance burner is so constructed that a temperature sufficient to ignite the gas is maintained—partly in the burner itself, and partly in the burner protecting shield N. The Chance lamp combines the use of the Mueseler chimney with that of the double glass safety lamp, and is thus practically two safety lamps in one. If the outer glass be broken, the lamp flame is still protected, and cannot cause ignition of the outer air. The inner glass chimney is virtually spring supported, so that falls or blows which might break the outer glass have little or no effect on the inner one. The objection to the use of double glasses in ordinary flame lamps—that the inner glass is liable to become smoked—does not apply to this lamp. The air feed is from the lower portion of the bonnet downward in the annular space between the glasses and through the bottom horizontal gauze to the flame. This arrangement increases the lighting efficiency by preheating the inlet air. The weight of the double glass lamp shown in the illustrations is approximately 4 lb. 2 oz. uncharged, and 5 lb. 4 oz. when charged for a 10 hour shift. The weight of earlier acetylene safety lamps is approxi- mately: Wolf lamp, 4 lb. 10 oz. uncharged; Tombe- laine lamp, 4 lb. | oz. uncharged; with a burning time of about 10 and 8 hours respectively. The weight of the Chance lamp when charged is less than either of the older types would be when charged to burn 10 hours. The Chance lamp requires a charge of from 7| oz. to 8 oz. of carbide for 10 to 10J hours’ burning time. After about four hours’ working, it is desirable that the water vessel should be refilled, through the spring plunger filling hole. Actually, the water vessel con- tains enough water to run a full shift, but during the later hours the gas pressure drops if more water is not added. The lamp is of the lead rivet locking type, with slip ring. The one lock completely secures both the whole of the generator parts and the internal fittings of the lamp itself. A minor advantage of the acetylene lamp is that it can be stored ready charged, precisely the same as an oil or benzine lamp, and will be immediately ready for use when required. The points in favour of the Chance acetylene safety lamp appear to be as follows: (1) Increased illumina- tion; (2) availablity as a gas detector; (3) facility afforded for roof inspection; (4) reduced risk of ex- tinction; (5) increased safety; (6) absence of perish- able joints; (7) portability and absence of deteriora- tion during storage. * The writer has already shown (see Trans. Inst.M.E., 1916-17, vol. liii., p. 234) that this is a purely theoretical and not a sound practical objection, but in everyday life it is not so much facts which require to be made convinc- ing as prejudices that have to be overcome. Non-Ferrous Metal Industry.—The Board of Trade draws the attention of holders of licences under the Non- Ferrous Metal Industry Act to the fact that these licences do not dispense the holders from complying with the regulations which have been made under the Defence of the Realm Act with respect to the sale or purchase of non-ferrous metals. The necessary permits under these regulations must be obtained from the Ministry of Muni- tions in respect of any sales or purchases of non-ferrous metals in the same manner as before the licences under the Act were granted. Miners, Coal Owners, and Excess Profits.—An official report of the recent war wage conference between heads of Government departments and the Miners’ Federation representatives has been issued. It was alleged that under the Government agreement the coal owners were working the collieries in a way calculated to increase the output in the future rather than just now. Sir Albert Stanley, the President of the Board of Trade, answering these statements, said : Under the very fair agreement between the Government and the mine owners, 80 per cent, of any excess profits went to the State. Of the remaining 20 per cent. 15 per cent, went to the Coal Controller’s account. Thus only 5 per cent, of any possible excess profits went to the mine owners. Any deficit on pre-war profits had, under certain conditions, to be made up by the Controller (that was, the State) out of the 15 per cent. The Con- troller’s financial advisers told him some time ago that there would be a deficit in the then price of coal, and that was why the Government authorised an advance of 2s. 6d. a ton, and 5s. to the Allies, in order that his balance sheet should not throw any additional burden upon the State. There was no advantage that he knew of that would accrue to the mine owners as a result of 2s. 6d. advance, beyond the possible 5 per cent, out of their excess profits, which was a very, very small figure indeed. He (Sir Albert) felt there should be no room for misunderstanding, and if there was a belief on the part of the men that there was any exploitation on the part of the mine owners, by all means let it be known and the misunderstanding removed. The Federation were free at any time to acquaint themselves with the financial position of the control. The Government would like the miners to feel that their extra efforts were not going to accrue to the benefit of the mine owners, but to the State.