MESSES. EDITORS:—Referring to your remarks on the Harrison steam boiler, published in your number of April 20th, I wish to say a word in regard to the strength of this boiler. In making many experiments to test the bursting strength of the spheres under hydraulic pressure, no sound casting ever gave way under fifteen hundred pounds to the square inch; It was not unusual for them to resist two thousand pounds, and this, too, when made of iron of no greater strength than the best brands of Scotch pig metal In a practical experience of several years with boilers varying from 5 to 300 horse power, explosions have never happened under any circumstances. Extreme proesure will open its joints before any thing gives way, thus making each joint a safety valve. A cracked sphere may produce a leak, but a boiler under pressure has never been suddenly emptied from such a cause. Instances have once or twice occurred where a cracked sphere has been continued for sometime after the fracture was discovered, with no troublesome consequences from the leakage, and no necessity for instant repairs.
There have been but four fractures of spheres in all the boilers mentioned in the advertisement now in your journal, and in every case these could be fairly traced to special causes not connected with pressure. In my experience with the boiler, several have been burnt, or, in other words, tendered unfit for service for the moment by overheating after the water had fallen too low. The result in such case is obvious; spheres with no water inside and intense heat outside, are soon heated to redness and warped go much that the integrity of the joints is destroyed, causing the boiler at the injured parts to leak badly, but nothing like an explosion occurs. With great facility and little cost of time or money, the injured parts, in such a case, can be taken out and replaced by new ones, without even the use of highly-skilled workmen, alter which the boiler is as good as before the accident. Some of these boilers are working daily at 180 pounds pressure to the square inch; and a good evidence of their value is shown in the fact that several parties, who have used the boiler longest in this country, have already in use, or have sent me orders for, a second one.
With this boiler on our Western steamboats, to which it can be easily adapted, such wholesale destruction or human life as took place on the Sultana a few days ago, cannot possibly occur.
JOSEPH HARRISON, Jr., patentee.
Philadelphia, Pa., May 2, 1885.
Harrison, Joseph, Jr., Letter to the Editor, “The Harrison Steam Boiler,” The Scientific American, May 13, 1866. New York: Munn & Company, New Series, Volume 12, Issue 20
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