In the present paper, the problems related to the adoption of a hybrid paradigm for the modelling and simulation of process control systems are addressed. First, a comprehensive modular modelling technique is introduced, which encompasses the main phenomena characterising hybrid control systems. Then, it is shown how such a hybrid model can be evaluated by means of simulations. In particular, the gPROMS simulation tool has been selected for its flexibility and numerical robustness. Finally, a significant portion of an hydraulic plant is studied as an application example, in order to illustrate the features and problems of the modelling and simulation of different hybrid phenomena, and how they can be faced and solved.