Pressure Vessel Design and Calculators
The following are equations and a calculator to determine the wall thinkness and working pressure of an ellipsoidal head with t/L greater than or equal to 0.002.
The require thickness of a dished semiellipsoidal head in which one-half of the "minor axis" (inside head minus the skirt) is equal to one-fourth of the inside diameter of the head skirt.
The following equations apply:
Do = outside diameter
tn = nominal thickness before forming
tf = thickness after forming
Ca = corrosion allowance
St = skirt length (straight section)
S = maximum allowable stress value
E = joint efficiency for, or the efficiency of, appropriate joint in cylindrical or spherical shells, or the efficiency of ligaments between openings, whichever is less.
For welded vessels, use the efficiency specified in UW-12. For ligaments between openings, use the efficiency calculated by the rules given in UG-53.
P = internal design pressure (see UG-21)
nt = tf - Ca = thickness with corrosion allowance removed
Di = D - (2nt) = inside diameter with corrosion allowance removed
h = D/4 = crown height
ho = h + nt = outside crown height
K = Interpolated from Table A (see Do/2ho
tr = Required design thickness
Po = maximum operating pressure
References: ASME Boiler and Pressure Vessel Code
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