Factorial Techniques applied in Chemical Plant Cost Estimation

Abstract

Economic aspects are a major player in assessing design alternatives for chemical plants. The study focusses on capital cost estimation by factorial techniques originating from the early works of Lang and Hand. A literature study is conducted on consecutively developed techniques, these are categorised and compared among others on the basis of appliance strategies, cost item inclusions and statistical backing. Similarities were observed: It was found that methods are especially proximate in estimating off-site costs and indirect costs, and systematically lack statistical analyses. The latter may be overcome in future methods with the help of cost estimation software. Quantifiable results were obtained from case study experiments with six factorial techniques applied to twelve cases. The chance that a technique successfully estimated the actual construction value, measured with reference values, appeared to be more dependent on case type than factorial method type; the database behind the method had a larger influence than factors applied.