With the development of sensors, fiber optics and
computer techniques, it is possible to do something that
was impossible to do in the past, i.e. condition
monitoring of some equipment. However, it is not
appropriate to perform on-line monitoring or on-line
detection for every kind of equipment. Necessity,
technique feasibility and cost performance ratio must be
analyzed first. Complete consideration must be
performed in order to get better profit and service
reliability. The flow chart for predictive maintenance
strategy classification is shown in Fig. 3. As for the
cases where the faults or failures are paroxysmal, it is
hard to acquire the feature parameters timely and trace
the evolving tendency. Therefore, it is quite difficult to
conduct predictive maintenance for such faults.