Modelling and simulation software tools should be sustainable even if it is not definitely required for temporary research projects with a publication as outcome. Especially, when using modelling in simulation as an integrated tool supporting both engineering and operation of industrial processes — the models should sustain for the whole life cycle of the target process — from initial design to decommission, at least 60 years. The solution relates, first, to apply such formal specifications of the physical model that easily can be carried as simple text files between generations of computer and operation system platforms. Second, reliable simulation engines are needed that are programmed in high level language enabling for transportation to the new platforms and. Third, standardised procedures for re-verification of the computational functionality are required. Fourth, easy connectivity to concurrently developing engineering databases and graphics interfaces is needed, as well. The advance of multi core processors, even on laptop computers, calls for reconsideration of the mathematical methods used so far in order to make use of the inherent computing power. Companion model graphs are supposed to have a significant mission in automated computer model generation from semantic plant specifications, as well as in even distributing to computation load on available cores.