Process Equipment and Plant Design
Seamless pipe is made

By forging a solid round, piercing it by simultaneously rotating & forcing it over a piercer point and further reducing it by rolling gas drawing
From rolled strips formed into cylinders and seam-welded
By extrusion & casting into static and centrifugal molds
Both B and C

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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

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

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