Plates, Shells, and Cylinders Machinery's Handbook, 31st Edition
294
1386
F p #
D
6
@
h
^
+
t
=
, 86 670
in which D = outside diameter of flue or tube in inches; t = thickness of wall in inches; p = working pressure in pounds per square inch; F = factor of safety. The formula is applicable to working pressures greater than 100 pounds per square inch, to outside diameters from 7 to 18 inches, and to temperatures less than 650 ° F. The preceding Formulas (29) and (30) were determined by Prof. R. T. Stewart, Dean of the Mechanical Engineering Department of the University of Pittsburgh, in a series of experiments carried out at the plant of the National Tube Co., McKeesport, Pennsylvania. The apparent fiber stress under which the different tubes failed varied from about 7000 pounds per square inch for the relatively thinnest to 35,000 pounds per square inch for the relatively thickest walls. The average yield point of the material tested was 37,000 pounds and the tensile strength 58,000 pounds per square inch, so it is evident that the strength of a tube subjected to external fluid collapsing pressure is not dependent alone upon the elastic limit or ultimate strength of the material from which it is made. Tubes Subjected to External Pressure Outside Diameter of Tube, Inches Working Pressure in Pounds per Square Inch 100 120 140 160 180 200 220 Thickness of Tube in Inches. Safety Factor, 5 7 0.152 0.160 0.168 0.177 0.185 0.193 0.201 8 0.174 0.183 0.193 0.202 0.211 0.220 0.229 9 0.196 0.206 0.217 0.227 0.237 0.248 0.258 10 0.218 0.229 0.241 0.252 0.264 0.275 0.287 11 0.239 0.252 0.265 0.277 0.290 0.303 0.316 12 0.261 0.275 0.289 0.303 0.317 0.330 0.344 13 0.283 0.298 0.313 0.328 0.343 0.358 0.373 14 0.301 0.320 0.337 0.353 0.369 0.385 0.402 15 0.323 0.343 0.361 0.378 0.396 0.413 0.430 16 0.344 0.366 0.385 0.404 0.422 0.440 0.459 16 0.366 0.389 0.409 0.429 0.448 0.468 0.488 18 0.387 0.412 0.433 0.454 0.475 0.496 0.516 Dimensions and Maximum Allowable Pressure of Tubes Subjected to External Pressure
Thick ness of Material, Inches
Thick ness of Material, Inches
Thick ness of Material, Inches
Max. Pressure Allowed, psi
Max. Pressure Allowed, psi
Max. Pressure Allowed, psi
Outside Dia., Inches
Outside Dia., Inches
Outside Dia., Inches
2
0.095 0.095 0.109 0.109
427 380 392 356
3 3 3 3
0.109 0.120 0.120 0.120
327 332 308 282
4 4 5 6
0.134 0.134 0.148 0.165
303 238 235 199
2 1 ∕ 2 1 ∕ 2 3 ∕
1 ∕ 1 ∕ 3 ∕
1 ∕
4
4
2
2
2
4
4
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