Grace's Guide

British Industrial History

1862 London Exhibition: Catalogue: Class VIII.: E. T. Wright

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Diagonal-seam Steam Boiler

2032. WRIGHT, E. T., Goscote Iron Works, near Walsall.

MODEL OF A CYLINDRICAL STEAM BOILER, constructed with Wright's patent diagonal seams, by means of which, longitudinal joints are altogether avoided, and 40 per cent. additional strength is required.

It is but recently that attention has been directed to the inequality in the resisting forces in the transverse and longitudinal sections of cylindrical steam boilers. Mr. W. Fairbairn, in his book, "Useful Information for Engineers," says:— "If we refer to the comparative merits of the plates composing cylindrical vessels subjected to internal pressure, they will be found in this anomalous condition, that the strength in their longitudinal direction is twice that of the plates in the curvilinear direction. This appears by a comparison of the two forces, wherein we have shown that the ends of the 3 ft. boiler, at 40 lbs. internal pressure, sustain 360 lbs. of longitudinal strain upon each inch of a plate in. thick; whereas plates of the same thickness have to bear, in the curvilinear direction, a strain of 720 lbs." And, it being a well ascertained fact, notwithstanding the vulgar notion to the contrary, that the ordinary or single riveted joint possesses but half the strength of the solid plate, it results that the longitudinal seams are the weakest parts of ordinary cylindrical boilers, however good the workmanship may be; and that sound principles of construction demand the abandonment of the common method of making them.

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