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Excerpt from The Locomotive, Vol. 18: January, 1897 The difficulty of discovering a crack of this kind is obvious enough, because the crack is entirely out of sight, and as it does not often run into a rivet-hole, it cannot be detected by leakage, until it has actually perforated the plate in some spot. These hidden fractures can sometimes be detected by the presence of radiating, hair-like branch cracks, extending out from under the inside lap. These faint indications might easily be overlooked by the most careful and competent inspector, especially as the joints that are thus affected are often in such a position that minute examination of them is not possible; and too frequently the radiating cracks do not exist at all, so that there is no human means of knowing the true state of the joint, without cutting out the rivets, and separating the plates, - a proceeding altogether too heroic to be in favor among boiler owners, unless there is some tangible reason for suspecting the defect. The dotted lines in Figs. 4, 5, and 6 show where the edge of the inside plate came, in each case. Numerous explosions have been caused by hidden cracks of this kind, with the most disastrous consequences; and hence it is important to discover their cause, if this be possible, and to take precautions against them. If the plates are hard, or tend toward brittleness, they may be so weakened by punching the rivet-holes that a subsequent fracture of some kind, along the joint, may be reasonably expected. It is, therefore, of the first importance to build the boiler of material that has proper ductility. Most of the fractures of the plate at the joint, however, are undoubtedly due to bending the plates in the rolls. From thirty to forty percent, of the sectional area of the plate is removed, along the line of the joint, by the act of punching or drilling the rivet-holes; and when the part that is thus weakened is passing through the rolls, the curvature of the plates at this point is sensibly increased, owing to the greater readiness of the weakened spot to yield to the stress imposed by the rolls. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.
