In many industrial applications, tilting pad journal bearings (TPJBs) are increasingly used because they are very suitable both for high-speed and high external loads. Their study is fundamental in rotating machines and a compromise between accuracy and numerical efficiency is mandatory to achieve reliable results in a reasonable time. This paper mainly focuses on the development of efficient three-dimensional (3D) models of TPJBs, in order to contemporaneously describe both the rotor dynamics of the system and the lubricant supply plant in long simulations (from the initial transient phase to the steady-state condition). Usually, these two aspects are studied separately, but their interactions must be considered if an accurate description of the whole system is needed. The proposed model architecture considers all the six degrees-of-freedom (DOFs) between supporting structures and rotors and can be applied to different types of TJPB layout with different lubricant supply plants. In this research activity, the whole model has been developed and validated in collaboration with Nuovo Pignone General Electric S.p.a. which provided the required technical and experimental data.