Abstract: In calcuation of the thickness of insulation for pipelining heated oil, for considering the time value of cuvrency which may exert influence upon the optimum insulation thickness, a reference discount rate is brought into the calculation formula and there is induced the one that gives consideration to the time value of currency.The article relates to the application of the formula to the selection of optimum insulation material and makes an analysis and discussion on the effect of the time value of currency on the optimum insulation thickness of heated oil pipelines, emphasizing that the calculation to determine the most suitable thickness is, in general, based on "dynamic" formula.