The Locomotive

PRESENTED BY \\r ftjv^vew C^^^ê. Sfe l0r0W0tfet PUBLISHED BY THE NEW SERIES. Vol. I. SECOND EDITION HARTFORD, CONN. 1880. 0t0m0ttM. PUBLISHED BY THE HARTFORD STEAM BOILER INSPECTION AND INSURANCE COMÂHY. New Series—Vol. I. HARTFORD, CONN., JANUARY, 1880. No. 1. Explosion of the "Lehigh." From the records of the coroner's court held in Hoboken, N. J., November, 1879, it appears that the Lehigh, which exploded in that city on the 28th of October, 1879, killing the engineer and fireman, was a passenger locomotive that had been remodeled in 1874. at which time the boiler was new. It had been in constant service, except while undergoing slight repairs, since May, 1874, on the Morris & Essex division of the D., L. & W. R. R. It was rebuilt under the direction of the master mechanic of the division, and was stayed in an extraordinary manner, having over fifty sling stays from the arch of the wagon top to the crown bars of the furnace, arranged in four rows, set as near radial to the arch as prac- ticable, Figs. 1 and 2. There were also horizontal cross stays from side to side of the shell between the crown bars, one to about every 5£ inches, and the crown bars were spaced the same distance apart, and consisted each of two broad parallel bars seated edgewise on the edge of the side plates of the furnaces andêcured to the crown sheet by bolts, washers, and gibbs in the usual manner. See Fig. 1. The shell of 5 the boiler was made of T g iron plate, marked C. H. No. 1, and the pressure was limited to 130 lbs. per square inch. There were two " " pop safety-valves and a steam gauge ; the latter was tested by the master mechanic after the explosion, and he swore that it was Fig. 1. correct and its connection to the boiler free from obstructions. The iron was tested at the Stevens Institute and found to have a good degree of tensile strength, viz. : 46,000 lbs. The accompanying cuts are intended to illustrate the construction and the character of the defect from which the explosion arose. Only such parts of the boiler as were supposed to be concerned in the explosion are shown in the cuts. The only plate involved was the crown plate of the wT agon top, which wr as about 6x7 feet in area, out of which a piece o£xl£ was torn from the right side and blown away a considerable distance, the reaction overturning the engine upon its left side. The opening is bounded by the fastenings of the cross stays on the lower side, by the fastenings of the ri^ht-hand row of sling stays on the upper side, at the forward end by the waist seam of rivets, six of which were sheared off, and at the back end by the foot of a short head brace, shown in Fig. 2. Fig. 1 is a section back of the dome, and Fig. 2 is a side elevation of the wagon top and dome, all other parts omitted in drawing (not torn off by the explosion). Fig. 3 is a full-size section of the plate and seam at c, d, Fig. 2, where indications of a recent leak were observed, shown by dots, Fig. 2. At c, Fig. 3, is seen the char- 78603 THE LOCOMOTIVE. [January, acter of the defects. Fig. 4 is cut from a sketch, full-size, of the edge of the plate c, d, shown in plan. The lines v, ®, indicate the worn edges of the lamina? of the plate covered with old iron oxides and clayey sediment from the interior of the boiler. The line 2V, 0, represents the inner boundary of the new fracture indicated by its sparkling and bright appearance, and the dotted area below the line 2V, 0, represents its area as compared with that of the old fracture above the line. This appearance was observed to extend a considerable distance each way from the points c, d, the proportion of old fracture varied, in general rather diminishing each way. It is probable that the fracture began at this point and extended forward and backward, reaching the waist girth seam forward, when a sufficiently long line was forced from its proper connections with the adjacent part below, it was bulged outward by the force of the expanding water, and the strain thus produced sheared the rivets of the seam. The progress of the explosion is now plain and natural. The gushing of the entire contents of the boiler, 4 « ei—.« c. Hu »s ts 3 a—r3~f ,y i—s-or B~~ » 3 3 9 9 s 9 o o S 5 » » S S « 5 « B o~.S Q a B O fat 9— — — —£x )•- • • •; :'CM- fy ' • • I Fig. 2. now relieved of superincumbent pressure, out of this opening, strips the plate along its supported boundaries and it is blown away, while the machine is capsized by the reaction of the issuing stream. The pressure on this area of 7^ square feet was but little less than 70 tons at the maximum pressure of 130 lbs. per square inch, and something like this force would react on the machine to overturn it if the opening had been made instantaneously, which would have been quite sufficient not only to overturn the machine when applied to its side, but to lift it bodily in the air if it had been applied at its centre of gravity and issued downward. The time that elapsed between the initial break and the entire separation of the piece of the plate that was blown away allowed the internal pressure to fall somewhat, but the time was something like that which expires between the lighting of the cartridge and the rending of the rock ; and not- withstanding the force was to some extent employed in breaking the plate, still enough remained, reacting on the atmosphere, to upset the engine. The balance of the force that was employed in overturning the engine must therefore have been tremendous in velocity to have done this work. The problem as to the cause of the defect from which this explosion arose is a little more difficult to solve. It is proper, however, to ask what is the legitimate office of the extra stays that we find in this boiler, and since there are, according to the evidence 1830.] THE LOCOMOTIVE. adduced in this case, thousands of locomotives in which they are not found, we may well ask whether they are needed at all when crown bars in sufficient number and size are applied to support the top of the furnace. It may be difficult to understand just how the extra expansion of the furnace could, by thrusting the shell outward in all directions, cause the development of a crack on the inner surface of the plate, but knowing that expansion has a sufficiently forcible character (though of its actual extent, dynamically, we do not know, since the problem involves the actual average temperature of the furnace side plates or else a practical experiment to deter- mine the extent of the motion of the crown upward on being heated up), we may with tolerable fairness suspect that unequal expansion of the parts was the cause. The question naturally arises in this connection, Would the fibres of the inner surface which suffer compression when sharply bent along the line of a rigid support, when the side or horizontal thrust is outward and the radial thrust is upward, flattening the arc between, on returning to the form it had when cold, be more readily wasted or acted on chemi- cally by the water in the boiler than those fibres of the outer surface which suffer distention during the same action of bending ? However this may be answered, the fact remains that a large number of defects of this character have been discovered and are on record ; but generally they are found close to the edge of the inner overlap of the seam. Another question presents itself in this practical case : Would not the thrust of the upper furnace stay-bolts moving the plate of the shell outward tend to utilize the cross stays as a pivot or fulcrum around which the point c, Fig. 3, would move inward, thus causing distention of the inner fibres at the defective point. Sometimes defects located as this one is and those in the two following reports do not assume the form shown in these three cases, but the wasting THE LOCOMOTIVE, [Januara. extends some distance above and below, thinning the plate by the formation of a furrow or groove, but always on the wet side of the plate so far as observed or recorded If we find that a boiler has its shell and furnace rigidly stayed together with the ends of stays set with round pins fitting nicely in round holes, and the stays sufficiently strong and numerous to act as struts, then every motion of the furnace will be communicated to the shell. In this particular case the^ number of the ex- treme thermal changes corresponds with the number of times that steam has been raised during a period of about 2,000 days, from May 1, 1874, to Oct. 28, 1879. Deducting the idle days, we have a fair statement of the number of the motions due to unequal expansion. We should hardly expect to find so many stays each bearing its exact proportion of the stress, and under unfavorable circumstances of construction they might be set so that a little additional distention or compression of the arch of the wagon top might be accom- plished with each stay or even row of stays.

Load more