The assembly planning for a chemical engineering plant defines the position of the individual machines and articles of equipment in an appropriate grid (Fig. 1). Apart from the demands of pipe routing, numerous widely differing, partly contradictory, boundary conditions influence the assembly of a plant. These include, among other factors, investment and assembly costs, ease of maintenance and operation, as well as safety and environmental protection. Thus numerous specialist areas are involved in this planning work, with the definition of the "optimum" solution being based on individual studies and particularly on experience.