1841.] 



THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. 



3-21 



instances of successive explosions hail occiirrcil in England, lie would not 

 at present enter npon an explanation of what he considered might have oc- 

 casioned these phenomena, hut he would express his conviction that the 

 practice of suddenly opening and closing the safety valves was extremely 

 dangerous. To be usehil as escape valves, they should he allowed to open 

 and to close in obedience to the steam's pressure only, not to be handled 

 more than was absolutely necessaPr'. 



None of the theories yet advanced appeared clearly explanatory of the 

 cause of the projection of heavy boilers from their seats, when in many cases 

 they contained abundance of water. He instanced a case in which a boiler 

 exploded, and carried to some distance a boiler connected with it, and in 

 which some men were at work. The boilers separated while in the air, and 

 the one which exploded attained a very considerable height, although it was 

 28 feet long by 6 feet diameter. The particulars of this explosion weie fur- 

 nished to him by Mr. Clarke, engineer to the Earl of Durham, but they could 

 not be properly appreciated or explained without the drawings and descrip- 

 tion. 



Explosion at Durham. — A boiler weighing about 2.J tons was projected 

 from its seat at Messrs. Henderson's M'ooUen Factory at Durham, in 1835 ; 

 it ascended to a considerable height, and fell 300 yards from the place where 

 it had been seated. 



Crenoer Mine. — A cylindrical boiler exploded at the Crenver iline in 

 Cornwall in 1812. It passed through the boiler house, and opened itself in 

 the yard outside, where it was described to have fallen " as fiat as a piece of 

 paper." 



Facts of this nature were replete with interest, and should lead engineers 

 to the consideration of causes and remedies. 



Boilers red hot. — Mr. Parkes then instanced several cases of boilers which 

 had become red hot, and had not exploded ; one example was a set of three 

 boilers, the tops as well as the bottoms of which were red hot, in consequence 

 of the house in which they were fixed being on fire ; yet they did not explode. 

 No water bad, however, been pumped into the boilers whilst so heated. 



Explosions of hydrogen gns. — He was in possession also of several curious 

 examples of ruptures and projections of vessels arising from causes very dif- 

 ferent to the foregoing. One case occurred in February 1837, at the Works 

 of Messrs. Samuel Stocks and Son, in the Township of Heaton Norris, near 

 Manchester. The boiler was 20 feet long, 9 feet wide, and 10 feet deep, and 

 weighed about 8 tons. On a Saturday night the water was blown out of it 

 through the plug-hole at the bottom, by the pressure of the steam, the man- 

 lid not being removed. On Sunday evening the fireman proceeded to take 

 off the man-hole cover to clean the boiler; on entering it with a candle and 

 lanthorn, a violent explosion occurred ; and the man was projected to some 

 distance and killed. On examining the boiler it was found quite dry, no fire 

 being alight, no traces of water near it, and it was quite cold : it had been 

 lifted from its seat up to the roof, which it destroyed, and the walls of the 

 building were thrown down. There was no difficulty in accounting for the 

 presence of a combustible gas, as hydrogen might be evolved from the de- 

 composition of the steam (which would remain in the boiler after the expul- 

 sion of the water) by the heated sides and bed of the boiler, and the atmo- 

 spheric air which entered through the plug-hole or through the man-hole, 

 when the lid was removed, was sufficient to form an explosive mixture. 

 The projection of the man was the simple effect of firing the gas ; but to ac- 

 count for the entire boiler being carried from its seat, was more difficult. 

 The figure of the boiler after explosion exhibited two distinct actions ; the 

 ends and sides had evidently been bulged outwards by the force of the ex- 

 plosion within it, and the bottom had been crushed upwards by the force 

 which raised it from its seat. 



Mr. Parkes thought the circumstances admitted of a satisfactory explana- 

 tion, but would not then enter upon it, as it involved the history and pheno- 

 mena of projections of vessels from their beds with a vacuum within them, 

 which he thought would be better understood after the reading of his paper 

 on the " Percussive Force of Steam and other Aeriform Fluids," then in pre- 

 paration for the Institution. 



The foregoing case of the formation of hydrogen gas in a boiler, after all 

 the water had been evacuated, was confirmed by one which took place in a 

 similar manner at the Sugar-house of Messrs. Rhodes and Son, in London, of 

 which all the particulars had been furnished to him by Mr. Henrickson, the 

 manager. .A man entering the boiler with a candle and lanthorn to clean it, 

 was projected to a great height. No rupture of the boiler took place, as the 

 quantity of hydrogen seemed to be comparatively small, f.nd to be confined 

 to the upper portion of the boiler, but a series of detonations occurred, like 

 successive discharges of cannon. 



These two remarkable instances showed the importance of attending to 

 minute circumstances in the management of boilers. The practice of com- 

 pletely blowing out boilers whilst the flues were intensely heated, was evi- 

 dently dangerous, nor should it be done without removing the man-hole 

 cover. 



Mr. Parkes felt that these notices of explosions were very imperfect with- 

 out drawings, and reference to documentary evidence, but, as the subject had 

 been brought before the Institution by Dr. Schaf haentl, he hoped that they 

 would be received as contributions to the stock of knowledge, and as illus- 

 trative of the precautions to be observed by attendants on steam engines. 



Mr. Seaward was glad to find the idea of the explosions of boilers arising 

 from the formation of hydrogen gas, so successfully combated by Dr. Schaf- 

 haeutl and Mr. Parkes. He perfectly agreed with the former in his opinion 



of the causes of the majority of explosions. In all that he had witnessed 

 the effects of, the lower parts of the boiler appeared to have suffered most. 



He was at the I'olgooth Mine immediately after the explosion theie. when 

 seventeen persons were killed. In that case, he was told that the boilers 

 were moved a distance of 7 or 8 feet from their seats, before any detonation 

 was heard. 



At the Hurlam Mine (which Trevithick had undertaken to drain for a cer- 

 tain sura) an engine with a cyUnder of 40 inches diameter was erected im- 

 mediately over the shaft. Its power was not sufficient for the work re- 

 quired ; the pressure of steam was therefore gradually increased as tue depth 

 became greater. At length the boiler, which was of an immense length, was 

 observed to have a constant tremulous or sinuous motion at each stroke of 

 the engine, and eventually it exploded. 



Boilers in London. — It appeare<l that there were fewer explosions of boilers 

 in London, in proportion to the number employed, than in any other district. 

 One reason for this might be, that fuel being exjiensive, it n'as used econo- 

 mically, by maintaining a slow rate of comb\istion, and a regular supply of 

 steam, avoiding the intense action of the fire, which, in the event of the' en- 

 gine standing still for a time, had a tendency to produce an explosion. 



Mr. Parkes attributed the small number of explosions of boilers in the 

 vessels on the Thames to the practice of allowing the steam to act upon the 

 safety valve, instead of the engineer lifting it when the engine was stopped, 

 as on board vessels in the north. The sudden closing of the valve had in 

 many cases produced an explosion. 



While on this subject, he felt it necessary to comment upon what he con- 

 sidered fallacious reasoning of Tredgold on the formation of hydrogen gas in 

 toilers.* The passage he alluded to was couched thus: — "Hydrogen gas 

 may be, and frequently is, formed in steam boilers through the water being 

 in contact with a part of the boiler which is red hot ; and it seems to be 

 regularly produced during the formation of steam at very high temperatures." 

 Dr. Schafhaeutl had shown, that the eflfect of water coming suddenly in con- 

 tact with a part of the boiler which was red hot, was only to disengage in- 

 stantaneously a large volume of steam of very high elasticity. Mr. Parkes 

 contended, that an instance of the sudden production of hydrogen gas in a 

 boiler under such circumstances was unknown, and he much doubted the 

 possibility of such an occurrence. Again, allowing such an event to be pos- 

 sible, an explosive mixture of gases must be formed before the boiler could 

 be destroyed ; and this could not take place so long as a sufficiency of water 

 was present, from which any considerable quantity of steam could be gene- 

 rated. 



ilr. Donkin did not entirely agree as to the non-formation of hydrogen in 

 boilers under peculiar circumstances. He conceived the explosions which 

 occurred in iron fonnderies, on the contact of the melted metal with wet 

 sand, to be analogous. He believed, that when water was thrown suddenly 

 npon red-hot plates, decomposition did occur. 



He bad once examined a wagon-shaped boiler which had exploded ; the 

 top was thrown to some distance, and the bottom was depressed throughout 

 its entire length. He believed, that by intense firing the water had been 

 nearly all evaporated ; the bottom had then become red hot, the pressure of 

 the steam had forced the bottom downwards when weakened by the heat ; 

 the water on each side then suddenly flowed on to the heated part, and an 

 explosion instantly occurred. 



Mr. Seaward had known instances of the internal tube of a boiler being 

 collapsed without any injury to the external part or body of the boiler. He 

 had always ascribed such occurrences to a deficiency of water ; but Dr. 

 Schaf haeutl's explanation of the rapid transmission of force through the wave 

 to the bottom would sufBciently account for the eft'ects which had been 

 observed. 



Mr. Donkin believed, that in almost every case the unequal pressure upon 

 the exterior of the tube, arising firom its not being perfectly cylindrical, was 

 the cause of its collapsing. 



Mr. Field was inclined to attribute aU the explosions which he had wit- 

 nessed to simple pressure. I 



When steam, or a small quantity of water, was suddenly admitted into a 

 dry heated vessel, hydrogen gas was readily formed. He had made several 

 sets of apparatus for the purpose. A strong wrought-iron tube was heated, 

 and, being filled loosely with fragments of iron-turnings, steam was intro- 

 duced and the gas was rapidly evolved. 



He agreed with Mr. Parkes in condenming, generally, the fallacy of the 

 opinion of Tredgold, previously mentioned, as to the formation of hydrogen 

 gas. Still, in a large boiler, almost dry, and of which a portion was red hot, 

 he conceived, that on the admission of a small quantity of water, hydrogen 

 gas might be evolved. 



Elevation of boilers Jrom their seats. — The President was unwilUng that 

 this conversation should terminate without endeavouring to explain the cause 

 of the elevation of the boilers from their seats. In his opinion, this might 

 be satisfactorily accounted for by the action of atmospheric pressure. 



When an explosion took place in a boiler, a considerable body of highly 

 elastic fluid was disengaged ; a partial vacuum was thus created above the 

 boiler, whilst the full pressure of the atmosphere was exerted beneath it. 

 This would cause the boiler to rise from its seat, provided the atmospheric 

 air did not at the same instant rush into it, in which case the bottom would 

 be pressed downwards, and the upper part being torn asunder, as had been 

 described, would then rise into the air with the elastic fluid. 



' Tredgold on the Steam Engine, vol. i. p. 251. 



Edition by Woolhouse. 

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