Capital cost estimation techniques in the chemical process industries (CPI) largely rely on scaling relationships. Understanding how scaling relationships relate to equipment characteristics enables them to be more effectively used, even when specific data is not available.
Empirical scaling exponents have not yet been published for every type of plant and equipment, but the same scaling principles apply. Follow the process described for the process vessel above. First, break down the total cost into its major components and estimate their relative contributions. Then, choose a representative capacity parameter and determine how you would expect each component to scale. The blended scaling exponent will be the contribution-weight average of the component exponents.
This kind of analysis is valuable even with approximation and guesswork. It provides a framework to probe and understand the fundamental relationships connecting scale, form, function, and cost.