ABSTRACT
The purpose of all monitoring is the understanding of the current state of the plant. In order to place in context the work presented in other chapters, it is essential to discuss the manifestation of various types of plant fault. The way in which a given machine will respond to an error type is, of course, partly dependent on the geometry of the machine in question: nevertheless, several of the more important categories of fault may be described generically. Before embarking on a discussion of the more esoteric faults, it is important to examine the properties of rotor unbalance. In Chapter 3, imbalance was briefly described and used as an example to illustrate several techniques. As imbalance is the most prevalent of all rotor faults, further details are given of approaches to the identification and rectification of imbalance, but an important consideration in this is the flexibility of the rotor itself. We begin, therefore, with a discussion on the difference between rigid and flexible rotors as these issues have an important influence on the optimum approaches to rectify problems.
