Laying out for boiler makers and sheet metal workers; a practical treatise on the layout of boilers, stacks, tanks, pipes, elbows, and miscellaneous sheet metal work . dish the more the pressure allowed, until thehead is hemispherical and then it reaches its limit. It iscustomary to make the radius of the dished head equal tothe diameter of the dome or shell to which it is attached. The United States rule for convexed heads, as amended January, 1907, is SXT = P Where P = Pressure allowable per square inch in pounds, T=: Thickness of head in inches, 5 = One sixth of the tensile strength, i? = O
Laying out for boiler makers and sheet metal workers; a practical treatise on the layout of boilers, stacks, tanks, pipes, elbows, and miscellaneous sheet metal work . dish the more the pressure allowed, until thehead is hemispherical and then it reaches its limit. It iscustomary to make the radius of the dished head equal tothe diameter of the dome or shell to which it is attached. The United States rule for convexed heads, as amended January, 1907, is SXT = P Where P = Pressure allowable per square inch in pounds, T=: Thickness of head in inches, 5 = One sixth of the tensile strength, i? = One-half the radius to which the head is 20 percent when heads are double riveted to the shelland all holes fairly drilled. Substituting values we have for the head under considera-10,000 X -375tion ^ pounds. Adding 20 percent for 13 double riveting we have X = pounds, pressureallowed. According to a different rule, ifT = Tensile strength, s T= Thickness of plate in inches, /? = Radius to which the head is dished, F^=FactoT of safety, F^ Pressure allowed, T^XT then P = RXF Referring to previous work we find that our factor with. FIG. 43.—MANHOLE, WITH CAST IRON REINFORCING RING. holes reamed was We will therefore use this factor in 60,000 X -375 our example ^ 206 pounds. 26 X 4-2 It will be seen that neither of these rules figure on the netsection of plate at the rivet joint where the head is attachedto the shell. The United States rule allows different valuesfor single or double riveting, but does not mention whatefficiency is required. We will assume that it is expectedthat the net section of plate and rivets compare favorably. Assuming that the head is dished so the weakness is at thenet section of plate, we will figure this out to ascertain whatfactor we will have. Using the constant as in previouswork, we have X -375 + 1-625 ^ inches, approximate
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Keywords: ., bookcentury1900, bookdecade1900, bookidl, booksubjectsteamboilers
