1854.] 



STEAM-BOILER EXPLOSIONS. 



81 



Steam-Boiler Explosions— Mr. Fairbairn's Experiments- 

 Proposed Associations for their Prevention. 



The emphatic declaration of the jury, in a remonstrance ap- 

 pended to their verdict, at the recent inquest, held at Rochdale, 

 on the bodies of the ten victims to the boiler explosion at Mr. 

 G. Williamson's weaving sheds in the Bidgefield Mill, near 

 that town, that they could not "separate without pressing on 

 the consideration of the owners and users of steam-boilers 

 throughout the kingdom the necessity there is that measures 

 should be taken by them to ensure a thorough and frequent 

 inspection of boilers, so as to prevent, as far as human foresight 

 can, the recurrence of explosions," demands from us a special 

 notice of the probable cause of that tragic occurrence. Peculiar 

 interest is attached to the enquiry, from the fact that Jlr. 

 William Fairbairn, the justly celebrated engineer, at the 

 solicitation of the coroner and jury, visited the scene of the 

 accident, inspected the premises, and investigated the origin 

 of the catastrophe. His report and evidence, therefore, furnish 

 a valuable commentary on the proper regulations of steam- 

 boilers, and may be considered a premonitory essay on the 

 shameless ignorance and frightful recklessness which, we fear, 

 are too often displayed in their management. He describes his 

 finding the buildings, steam engine, boiler, and machinery, a 

 heap of ruins ; the boiler torn into eight or ten pieces ; one 

 portion of the cylindrical part flattened and embedded at a 

 considerable depth in the rubbish ; the two hemispherical ends 

 burst asunder, and driven in opposite directions to a distance 

 of 30 to 35 ft. from the original seating of the boiler. Other 

 parts of the cylinder were projected over the buildings, and 

 lodged in a field distant 90 yards from the point of projection ; 

 to one of which parts had been originally attached the 2-in. 

 safety-valve, which was torn from the boiler by the force of 

 the explosion, and carried along with its seating over a rising 

 ground to a distance of nearly 250 yards. The other portion 

 of the cylindrical part of the boiler was found on the opposite 

 side in the bed of the river; and the hemispherical end of this 

 part furthest from the furnace was rent in two, and thrown on 

 each side to a distance from 30 to 35 ft. These two pieces had 

 evidently come in contact with the chimney, razed it to the 

 ground, and finally lodged themselves on the margin of the 

 river, while the 3-in. safety-valve and pipe attached to that 

 portion of the boiler imbedded in the river was broken from the 

 flange ; and with an extended range the 2-in. valve was pro- 

 jected over the river into a meadow at a distance of from 150 

 to 200 yards. Of the steam-engine not a Vestige was to be 

 seen, except the fly-wheel and a pump rod beside it, covered 

 with bricks. The springing of a mine could not have been 

 more destructive than this explosion; and we are thus enabled 

 to judge of its terrific force. 



The ta.sk of arriving at the extent of its violence was attended 

 with many difficulties, arising from the want of an accurate 

 knowledge of the state of the safety-valves, the density of the 

 steam at the moment of rupture, and the ultimate strength of 

 the boiler. Mr. Fairh.vir.n, accordingly, entered into a few 

 comparison.s, which he conceived would be useful to those en- 

 trusted with the management of boilers, and the employment 

 of steam of increased density and great ehustic power. Gun- 

 powder is calculated to impel a body with a force 244 times 

 greater than the pressure of the atmosphere, which, taken at 

 15 lbs., gives 244x15=3669 lbs. as the force upon a square 

 inch of surface — being nearly 30 tons upon a piece of ordnance 

 of 6 in. calibre. Bullets discharged ^vith this force, augmented 



by the elastic power derived from the heat generated in firing 

 gunpowder, will leave the muzzle of the gun at a velocity of 

 1700 ft. per second, or nearly 20 miles a minute; and although 

 the effects of boilers bursting with high-pressure steam may 

 not be equally appalling, they are, nevertheless, sufliciently so 

 to be placed in the same category as engines of destruction, 

 and ought to be treated in the same manner and with the same 

 precaution. 



Mr. Fairbairn found the boiler in question with hemisphe- 

 rical ends 1 8 ft. long, 5 ft. diameter, and composed of plates sup 

 posed to be 5-16ths of an inch thick — a thickness equal to a 

 pressure of 335 lbs. on the square inch ; but one of the plates 

 being under 5-16ths in thickne.ss, and as the thinnest part is 

 the measure of the strength of the boiler, he reduced its power 

 to 300 lbs., which he considered the force at which it would 

 burst. Taking 300 lbs. as the pressure on eveiy square inch 

 of the surface, and the superficies at 41,000 in., there was pent 

 up in this comparatively small space the enormous force of 

 41,000 X 300=^12,300,000 lbs., or 5491 tons of elastic force 

 compressed in an iron case of little more than a quarter of an 

 inch in thickness. 



The relative volume of steam at the pressure of the atmo- 

 sphere is 1700 times that of water. At higher temperatures, 

 and increased density, the volume is reduced in a given ratio 

 of its temperature and density; and it is impossible to increase 

 the temperature without increasing the pressure. In boilers 

 having an active fire burning under them, the engine standing, 

 safety-valves fast, it matters not how, the temperature will rise, 

 the pressure increase, and explosions ensue, unless relieved by 

 starting the engine, or letting off the dangerous accumulation 

 of temperature and pressure ; for which purpose the valves 

 must be looked to, the fires regulated, and the pressure kept 

 down below the dangerous point of resistance. Steam-boilers, 

 according to Mr. Fairbairn, of every desciiption should be 

 constructed of s^ifficient strength to resist eigbt times the 

 working pressure ; and a boiler should not be worked unless 

 provided with at least two, but he would prefer three, capacious 

 safety-valves. Two of these valves should be nearly equal to 

 double the area of the steam ports of the engine they are in- 

 tended to drive, and the other about one-fourth of that area, as 

 an indicator of the pressure. Nine-tenths of the boiler explo- 

 sions which have occurred in that district have taken place 

 when the engine was standing, or rather just after starting; 

 and it has been generally found that the safety-valves were 

 either of imperfect oonstmction, or fastened down, or accident- 

 ally shut. The generated steam and accumulated pressure 

 must, under these circumstances, have vent ; and in case it 

 cannot escape through the engine, or out through the safety- 

 valves, it is sure to make way for itself — not through the usual 

 outlets, but through the sides, ends, or bottom of the boiler. 

 It has been asserted that explosive gas is generated in several 

 cases where explosions occurred ; but jMr. Fairbairn utterly 

 repudiated the notion, being satisfied from experience and long 

 observation that gas had nothing to do with them — that they 

 were governed by a fixed and determined physical law, and that 

 law is neither more nor less than excessive pressure. In cases 

 where boilers explode from want of water, and the plates be- 

 come red-hot, then and then only does the spheroidical theory 

 of BoUTIGNY come into operation, in which instances largo 

 globules of water, containing immense central heat, are formed, 

 and bursting with great force and a loud report, might rupture 

 the vessel in which they are contained. This could not. how- 

 ever, take place unless water is pumped into the boiler suddenly-. 



