An aggregative simulation system that uses the time-slicing method to obtaining the numerical responses of complex mechanical system (CMS) is described in this paper. This class of system is represented by a few procedures: communication, calculation, visualization, linking and structure mapping. Some of these procedures have been used to estimate distributed controls of the steam-generating system (SGS). For the case in which both calculation and visualization processes are used, these control (input) profiles show which element of the SGS is more disturbed by means of an arrow. To memorize the local disturbance, a calculated window has been used in which it is possible to show some numerical and graphical characteristics of all the elements of a CMS. To complete the numerical simulation of a CMS, a general example is worked out to show how this simulation system helps to select some operating conditions of all the elements of SGS.