February 7, 1913. THE COLLIERY GUARDIAN. 279 THE USE OF GASES FOR FIRE EXTINCTION.* By E. Kilburn Scott, A.M.Inst.C.E. The methods of extinguishing fires on board ship are:—1. Closing the hatches. 2. Flooding the holds with water. 3. Blowing in steam. 4. Blowing in an inert gas. The inert gases generally used are (a) carbon dioxide gas, (&) sulphur dioxide gas, (c) flue gas. Gas is the best medium for fire extinguishing. The gas must be a non-supporter of combustion, must not condense, and must not injure the cargo. Naturally carbon dioxide is the first one to suggest itself, and it is of interest to note that so long ago as 1875 Mr. J. Glover proposed its use. His method of preparing the'gas was not feasible, because he required about 4 tons of hydrochloric acid and chalk for every 1,000 tons of cargo. In 1900 Prof. Vivian B. Lewes suggested (“ The Spontaneous Ignition of Coal Cargoes,” Institute of Naval Architects Proceedings, vol. 31, p. 217) that liquid carbon dioxide might be used. It is clear that if by any means the air in a space, whether it Fig. 1.—Clayton Sulfhur-dioxide Apparatus. E R bLc END VIEW. .Q ToV J i 1 SIDE ELEVATION. Fig. 2.—Harker Apparatus. By means of the Gronwald valve and steam, a 401b. bottle can be emptied in five minutes, whereas with an ordinary reducing valve it would take half an hour. Each pound of liquid gas expands to about 8 cubic feet of gas at atmospheric pressure. A cylinder weighing about 1| cwt. contains 401b. of liquid or compressed carbon dioxide, and 50 cylinders will therefore provide about 16,000 cubic feet of gas. The Gronwald carbon dioxide apparatus has been fitted to 70 vessels. In the Clayton system, sulphur is burned in a generator, and the products of combustion are cooled and then forced through pipes into the ship’s holds. According to a Local Government Board report, the composition of the gas averages about 10’5 per cent, of sulphur dioxide, 80*5 per cent, of nitrogen, and about 9 per cent, of oxygen. According to these figures, a ton of sulphur will produce about 180,000 cubic feet of gas. The machine generally used for steamships measures 5 ft. 8 in. by 4 ft. 10 in., is 4 ft. 8 in. high, and weighs 33 cwt. It is illustrated in fig. 1. The generator is charged with ordinary roll sulphur, and when gas is required a handful of cotton waste saturated with methylated spirit is placed on the sulphur, and ignited. The generator door B is closed after first starting the engine C which drives the blower. Air is drawn into the generator through the suction pipe which connects with the upper part of the hold or compartment to be treated. The air thus extracted passes into the generator, where the oxygen, combining with the burning sulphur, forms a fire-extinguishing and germi- cidal gas, which passes out through the cooler to the blower. It is then forced through the delivery pipe leading into the lower part of the hold or compartment to be treated. The fire is thus deprived of the oxygen necessary for its support, and such oxygen is replaced by sulphur dioxide gas. One objection urged against sulphur dioxide is that it attacks the metal work and spoils some kinds of cargo. Over 200 steamships and 20 sailing vessels have been fitted with the sulphur dioxide system. Sulphur dioxide iron pipes (cast iron being chosen to prevent erosion), water also passes down at the same time, but at a quicker rate, so that an ejector effect is set up which reduces the suction head of the fan. The velocity of the gas is about 50 ft. a second and of the water about 120 ft. a second. As the water shoots through the gas it picks up the soot particles and they run off with the water at the bottom. The gas then returns to the top of the washer by a circular path, the whirl of which throws out more water and it then passes to the fan clean. About 3,000 gallons of water per hour are required to cool down 90,000 cubic feet of gas per hour to a temperature of 120 degs. Fahr. Under good working conditions 1 lb. of coal requires about 18 lb. of air, a quantity which at ordinary temperature and pressure occupies about 196 cubic feet. During combustion most of the oxygen combines with the carbon of the coal, and is converted into carbon dioxide gas, which, when cooled, occupies exactly the same volume as the original oxygen consumed. Hence about 450,000 cubic feet of flue gas are produced by burning 1 ton of coal. Flue gas from oil fuel is just as effective. The exhaust from internal- combustion engines may be used, and will require less cleaning than flue gases. ' As it is probable that within a very few years a large number of vessels will be propelled by internal-combustion engines, this is an important point. Such exhaust gases would contain very little oxygen, and be therefore very effective for fire-extinguishing purposes. One objection that has been urged against the Harker system is that the flue gas might contain sufficient carbon monoxide to form an explosive mixture with the air in a hold. Dr. Harker’s rejoinder to that is that if such a liability to explode exists, it ought to show itself whenever a fireman opens the door of a boiler furnace and allows the rush of air to mix with the supposed inflammable gases. Yet it is common knowledge that nothing of the kind ever happens. Experiment has shown that not less than 16 per cent, of carbon monoxide must be present in the mixture with the air before explosion is possible, while in ordinary experience the proportion in flue gas never reaches even 5 per cent., and is very rarely over 1’5 per cent. In good combus- tion it is absent altogether. Flue gas is incapable of exploding when mixed with any proportion of air what- ever. It has been so largely deprived of oxygen and contains so much inert gas—nitrogen and carbon dioxide—that it may be used to dilute a mixture of explosive gases and prevent ignition. In America the Harker system has been investigated by a specially appointed Naval Board and passed through all the tests applied. The flue gas system undoubtedly stands first in effectiveness of operation, because the gas can be delivered into the holds at a much greater rate and the supply kept up for a longer period than the gases used in other systems. A pure CO2 gas supply is naturally limited to the amount carried in the steel bottles, and SO2 gas supply is limited by the amount of raw sulphur available, also by its speed of travel in a complicated piping system. be the hold of a ship, an oil storage tank or other space, can be displaced wholly or in part by some other gas not itself a supporter of combustion, so that the ratio of ■oxygen to other gases is reduced sufficiently low, the fire must be extinguished. Although the earlier attempts to use gas were not successful, the very obvious advantages kept the matter uppermost in inventors’ minds, and to-day there are three different systems at work. They are:— 1. The Gronwald system, using pure carbon dioxide, which is stored in steel cylinders. 2. The Clayton system, using sulphur dioxide, which is made from raw sulphur in a special apparatus. 3. The Harker system, using the waste flue gases from boiler furnaces. In the Gronwald system the fire extinctive gas is stored in steel cylinders under pressure, so no machinery is required to deliver it; steam or water is necessary to provide heat for the gas. A feature of the system is thst the gas acts not only as an extinguisher by diluting the air, but it also acts as a cooling agent, because of the low temperature produced. In the Gronwald apparatus the gas is not heated in its liquid state, but only after its issue in the vaporised condition. The heating medium is thus brought in contact with the gas in a fine state of subdivision, and consequently acts thereon without danger of the heat being carried back to the storage vessel. The heating medium may be steam or else water of ordinary temperature. * From a paper on “The Use of Gases on Ships for Fire Extinction and Fumigation,” read before the Institute of Marine Engineers on November 18, 1912. has been introduced into holds to prevent spontaneous combustion of coal cargoes; but as the gas is readily absorbed by moisture, forming an acid, it would not be suitable for any but a very dry coal. An ordinary fire receives its supply of oxygen from the air, of which this gas forms 21 per cent. When the oxygen content is reduced to about 15 per cent, the j combustion of ordinary substances ceases. It will thus be seen that flue gas is quite unable to support com- bustion, and it is the gas which is used in the system due to Mr. G. Harker, D.Sc. A typical example of flue gas follows:— Per cent. Nitrogen ............... 80’5 Carbon dioxide ......... 10*0 Carbonic oxide ........... *5 Oxygen................... 9 0 Fig. 2 indicates the details of the Harker apparatus. A is a De Laval turbine driving the fan B ; but of course an electric motor could be used instead of the turbine. A branch pipe C connects to the main funnel from the boilers or to the funnel of the donkey boiler, and it conducts the gas to the washer and cooler D. After being washed, the gas then passes to the fan, and by it is delivered to the gas main through E. Sea-water is pumped into the washer at F, and is formed into a fine spray, which takes out the soot as the gas passes on its way to the fan. At G there is a branch opening to the atmo- sphere, which is used when ventilating the holds. Disin- fectants can be drawn from tank J in a vaporised condition and carried along with the gas to all parts of the ship- The washing is effected in the following way:—The gases pass downwards through a nest of six-sided cast Hall Goal Exporti. - The official return of the exports of coal from Hull for the week ending Tuesday, January 28, 1913, is as follows:—Amsterdam, 940 tons ; Alexandria, 10,958; Antwerp, 1,235; Bremen, 3,575; Buenos Ayres, 2,418; Civita Vecchia, 3,757; Christiania, 1,903; Drontheim, 242; Guernsey, 125 ; Ghent, 406 ; Gothenburg, 656; Hamburg, 7,148; Harlingen, 783; Halmstadt, 621; Harburg, 2,089 ; Konigsberg, 3,324; Libau, 1,015; Malmo, 1,831; Odense, 2,176; Ostende, 1,043; Oxelosund, 1,523; Riga, 2,493 ; Reval, 2,683; Rouen, 3,904; Rotterdam, 5,943 ; Stockholm, 338; Santos, 5,726; Trieste, 202; Venice, 893 ; Zeebrugge, 2,112; total, 72,012 tons. Corresponding period January 1912, total 26,795 tons. The Lothians Mineworkers’ Ambulance" League.—A well-attended meeting, representative of the owners and men of the mines in the Lothians, was held in Edinburgh on Saturday, Mr, W. Walker, H.M. inspector of mines, in the chair. Lord Murray of Elibank was elected hon. president; Mr. W. Walker, H.M. divisional inspector of mines for Scot- land, president; Mr. R. Ramsay, general manager, Niddrie Collieries, Portobello, vice-president; Mr. H. J. Humphrys, H.M. inspector of mines, hon. secretary and treasurer. Constitutional rules for the league and rules for the com- petitions were agreed on, and will be circulated shortly. A shield has been presented by Lord Murray, and it was decided to invite subscriptions from those interested in the mines to defray the cost of badges for members of winning teams. Any mine or works in connection therewith in the Lothians is entitled to enter any number of teams for the competition, and preliminary competitions will be held in the three counties. Strong local committees have been appointed to carry out the arrangements for these prelimi- nary competitions, and it is hoped that they will be started some time next month. It is hoped that the competition will be a stimulus to the important work of ambulance training in the mines of the Lothians.