SUMMARY

Rotating machines are inherently vulnerable to many different faults; detecting these faults in real time can reduce costs and improve safety. A successful condition monitoring system must rely on accurate diagnostics gleaned from precise models of both the system and the faults. Furthermore, the pursuit to increase efficiency has heightened susceptibility to coexisting fault situations; comprehensive diagnostics should consider the possibility of multiple simultaneous faults. Previous studies have primarily considered the rotor and associated triboelements (e.g., mechanical face seals) as separate machine components. This work hypothesizes that rotor vibration transmitted to the mechanical face seal could serve as a convenient surrogate for rotor fault diagnostics. A comprehensive dynamic model is developed to study the dynamics of a mechanical face seal with two flexibly mounted elements, including axial, eccentric, and angular degrees-of-freedom. In addition, and for the first time, the model developed herein includes coupled rotordynamics, inertial maneuver loads, and transient dynamic excitation (i.e., start-up and shut-down). The faults investigated here include intermittent rotor-housing contact, a breathing shaft crack, and seal face contact. A novel model for intermittent contact is developed using a realistic surface roughness model founded on elastoplastic asperity contact. Exhaustive simulation is then used to identify hallmark dynamic fault signatures. Finally, the multiple fault scenario is studied using a synthesis of stationary and non-stationary signal processing techniques.