Thermal insulation economic analysis for a system of pipelines insulated by different materials composite layers is studied. The analysis is based on an explicit nonlinear cost function that includes the annual energy losses and the insulation initial costs. Practical ranges of different insulation thicknesses are included as a set of inequality constraints. Furthermore, the analysis accounts for the safety limits required for the temperature of the outer surface of the insulation. A search procedure, modified Hook and Jeeves, is employed to find the optimum thickness for the least annual cost within the domain bounded by the constraints. The procedure has been verified against the analytical solution for a single pipeline with a single insulation layer. The analysis is employed for a system of pipelines (4-10" nominal size) [1] with flow of superheated steam. Furfural, crude oil, and 300-distillate. The results show significant cost saving with optimal insulation compared to the dimensions of engineering practice. Detailed data for these cases are presented and discussed.