Twentieth century hand-book for steam engineers and electricians, with questions and answers .. . sistance is P — 2D x T x + A x S, or 15 — (.9375 x2) x .5 x 60,000+ .69 x 45,000 = 424,800. It appears that the weakest part of the joint is at theouter row of rivets, where the net strength is 421, strength of the solid strip of plate 15 in. widebefore drilling is P x T x , or 15 x .5 x 60,000 =450,000, and the efficiency is 421,875 x 100 ?*? 450,000 = per cent. Staying Flat Surfaces. The proper staying or bracingof all flat surfaces in steam boilers is a highly importantprobl
Twentieth century hand-book for steam engineers and electricians, with questions and answers .. . sistance is P — 2D x T x + A x S, or 15 — (.9375 x2) x .5 x 60,000+ .69 x 45,000 = 424,800. It appears that the weakest part of the joint is at theouter row of rivets, where the net strength is 421, strength of the solid strip of plate 15 in. widebefore drilling is P x T x , or 15 x .5 x 60,000 =450,000, and the efficiency is 421,875 x 100 ?*? 450,000 = per cent. Staying Flat Surfaces. The proper staying or bracingof all flat surfaces in steam boilers is a highly importantproblem, and while there are various methods ofbracing resorted to, still, as Dr. Peabody says, thestaying of a flat surface consists essentially in holdingit against pressure at a series of isolated points whichare arranged in regular or symmetrical pattern. Thecylindrical shell of a boiler does not need bracing forthe very simple reason that the internal pressure tendsto keep it cylindrical. On the contrary the internalpressure has a constant tendency to bulge out the flat THE BOILER 311. FIGURE 101. surface. Rule 2, Section 6, of the rules of the U. Inspectors provides as follows: No bracesor stays hereafter to be employed in the constructionof boilers shall beallowed a greaterstrain than 6,000 sq. in. of sec-tion. The method to beemployed in stayinga boiler depends upon the type of boiler and the pressureto be carried. Formerly when comparatively low pres-sures were used (60 to 75 lbs. per sq. in.) the diagonalcrow foot brace was considered amply sufficient for stay-ing the flat heads of boilers of the cylindrical tubulartype, both above and below the tubes, but in the presentage, when much higher pressures are demanded,through stay rods are largely employed. These aresoft steel or iron rods i}( to 2 in. in diameter, extend-ing through from head to head, with a pull at rightangles to the plate, thus having a great advantageover the diagonal stay in that
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