ON THE EXPLOSION AND RUPTURE OF STEAM BOILERS.
The remark, that it is the lot of mortality to have good united to evil, has been made a thousand times, and applies with peculiar force to the case of Steam Engines. A great drawback upon the profit and con venience derived from the powerful agency of steam, and from the satisfaction consequent on the facilities and rapidity of travelling afforded by steam-boats, and the comforts enjoyed on board of them, is the fear of the explosion of their boilers, or the rupture of their steam tubes. It has been thought proper therefore on the present occasion to collect all the in formation possible on the subject, to examine and de tail the circumstances under which they have occur red, to state the causes of the accidents, and to point out the means most likely to prevent their occurrence. The causes which are known to have produced these explosions and ruptures, are as follow: I. The continued application of heat to a boiler, while any part of it is uncovered with water, or in which it is expended.
2. The steam being prevented from passing off, owing to, 1. The rusting of the safety valve. 2. Its adhesion to its scat. 3. Stopping the steam pipe by the valve, owing to the improper form of the pipe. 4. Overloading the safety valve, or of fastening it down, so as to increase the power of the steam beyond the maximum point which the force of cohesion in the metal of the boiler would bear, or while the engine was stopped from working. Small size of the valve.
3. Want of proper precautions to strengthen the boiler, when first made.
4. The use of internal flues in boilers.
5. The use of improper metal in the construction of the boiler.
6. The use of metals for boilers, of different ex pansive powers.
7. 'Weakness of the boilers from long use, or un equal thickness in the metal, and raising the steam to a height beyond its strength.
8. Faulty form of the boiler.
9. A collection of earthy or saline sediments on the bottom of the boiler.
10. Tile sudden increase of the pressure of steam on a boiler.
1. Loss of water in the boilers.
The cases embraced under the first cause are, the loss of water in or around the boiler or boilers, from, a. leaks; b. neglect of a supply of it; c. the heeling of the vessel from the concourse of passen gers on one side, thus forcing the water from one or more of the boilers, when several are in use ; or caus ing the boat to heel so much to one side as to render the guage cocks useless; d. obstructions in the pipe or pipes feeding one or more boilers.
It is believed that most of the explosions of steam boilers may be ascribed to the first cause, and its several modifications. The neglect to supply boil ers when leaky, or to keep those filled which are sound, admits of no excuse : and misfortunes arising therefrom, to passengers on board of boats, affords as just and legitimate grounds for an action of damages, as those that occur in stage-coaches from racing, mismanagement, intemperance in the driver, or his wilful indifference in any way, to the safety of travel lers.
The explosion in one of the high pressure boilers of the Union Rolling Mill at Pittsburgh, a few years since, can be ascribed only to this cause. There were three cylinder boilers, each of thirty inches di ameter, one of which had been observed for some time to be getting red hot; but as the other two had supplied a sufficiency of steam for the works, it was disregarded until it exploded, and shooting through the air, at an angle of forty-five degrees with the hori zon, fell into the river two hundred yards from the works.* The over heating of the exploded boiler can not be ascribed to any other cause than the want of water in it. Boats on the western waters are particularly exposed to danger from this cause. Many of them have several boilers connected with one another; when one of these boats leaves port with a full cargo of passengers, goods, and a supply of wood, she sinks deep in the stream, and the boilers are all surrounded with water to the proper height. In the course of her voyage wood is consumed, passengers and goods are landed, the forward portion of the ves sel rises a little from the weight of wood being re moved, and when a landing place is reached, all the passengers invariably rush to the side next the land, and thus cause the boat to heel, and the water to run out of the boilers on the opposite side. The same ef fect is produced by 400 or 500 passengers sometimes sitting on one side of the boat in summer, to avoid the sun. In the meantime the fire is kept up, the empty boiler becomes red hot, and when the boat recovers her trim, the heated water rushes into the empty boilers, highly expansive steam is instantly gene rated, and when the throttle valve, or safety valve is opened, the water mounts up with the steam, and fill ing the boiler, presses on the weakened metal beyond its power of cohesion; an explosion therefore must take place. The awful disaster on board the Helen
M'Gregor, March 1830, is a case in point. The ex plosion took place at Memphis in Tennessee. The engine was on the high pressure principle. She had six or eight boilers, and was full of passengers ; nearly all of whorn,when at the landing, came to the side near the shore, and of course caused her to heel great ly, and to drive the water from the boilers on the other side into those next the land. The fire was kept up during her stoppage, and thus must have rendered the empty boiler red hot. The explosion instantly follow ed the opening of the throttle valve to set the engine in motion. Between 60 and 80 persons were killed, scald ed and wounded, and the boat was reduced to a mere wreck. The boat Chief Justice Marshall was another instance of the same kind: " the main internal flue gave way when the engine was set in motion after a stop page at Newburgh, North River; the safety valve was either open, or had just been closed; one of the persons on board remarked a peculiar shrillness in the sound of the escaping steam, that can only be ascribed to its being intensely heated, having a corres ponding density. Another observed that it had a violet hue, which may perhaps be explained by sup posing it to have been heated until would have been luminous at night. In opposition to the opinion that the water had fallen too low, and left the flues bare, it was stated by the captain, that the guage cocks had been tried, but on examination it was found that they were situated on the side of the boiler nearest the landing; and hence the influx of passengers to that side changed the level of the boat so much as to ren der the guage cocks, when so situated, useless as a test of safety. It is also possible that the fireman, who was a new hand, and by no means skilful, may have mistaken the water ofcondensation in the tube for that coming from the boiler. This last mistake is one that ought to be carefully guarded against by leaving the cock open several seconds."* It would appear from the following statement, that besides the probable over heating of the boiler, the steam had been permitted to collect in quantity beyond the cohesive powers of the boiler. • The editor of the New York American vouches for the respectability of the writer.
From the New York .9merican,.9pril 24, 1830.
Mr. Editor,—I perceive the captain of the Chief Justice Marshall says, that the steam was blowing off continually while landing. I doubt the correctness of this statement. My own very strong impression is, that no steam was going off while she was approach ing the dock, nor while she was taking in the New burgh passengers, of whrtm I was one, and that it was not permitted to escape at all, till within about three minutes of the explosion. For three or five minutes before this took place, I was standing at the door of the captain's office; and having nothing else to do, di rected my whole attention to the steam; it was going off at that time, but so very slowly as to make but a slight murmuring sound. This continued three or four minutes, and was exchanged for the shrillest and most piercing whistle I ever heard; so that I immedi ately made the reflection (whether correct or not I do not know), " The steam is excessively high!" Still it appeared to me that very little steam was es caping, and as if it passed through an exceedingly small aperture. This sound continued a few seconds; it suddenly ceased, and, almost simultaneously, the boiler exploded! My own opinion is, that the steam was suffered to accumulate in the boiler in a very im proper manner; and, as all the disasters of this kind have happened while boats have been lying at or leav ing the dock, is it not fair to conclude, that it is owing to this cause—the improper accumulation of steam in the boilers ? Why the steam is kept there pent up, I know not; but it seems to me it cannot be done without danger. No law on this subject would probably contribute more to the safety of passengers than one which should provide, that the moment the steam ceased to he employed by the piston, it should be let off in the same proportion at the safety-valve.