Process Equipment and Plant Design
Generally, elliptical dished heads

Resist half the pressure rating compared to hemi spherical head provided on the cylindrical shell of the same thickness and diameter
All of these
Are approximately as strong as seamless cylindrical shell having the corresponding I.D and O.D
Are manufactured on 2:1 ratio of major to minor axis and is recommended to be used for pressure vessels operating above a pressure of 1.5 MN/m²

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Process Equipment and Plant Design
Smoker's equation for the calculation of number of equilibrium stages in a continuous binary distillation column is used, when the

Relative volatility is close to one (e.g., separation of close boiling isomers)
Number of equilibrium stages required is likely to be very small
Feed is not at its bubble point
Number of equilibrium stages in only stripping section is to be calculated

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