INTRODUCTION

The demanding requirements placed on modern rotating machines and equipment for example, electric motors and generators, turbines, compressors, and blowers have introduced a trend toward higher speeds and more stringent acceptable vibration levels. At lower speeds, the design of most rotors presents few problems which cannot be solved by relatively simple means, even for installations in vibration-sensitive environments. At higher speeds, which are sometimes in the range of tens of thousands of revolutions per minute, the design of rotors can be an engineering challenge which requires sophisticated solutions of interrelated problems in mechanical design, balancing procedures, bearing design, and the stability of the complete assembly. This has made balancing a first-order engineering problem from conceptual design through the final assembly and operation of modern machines.

This chapter describes some important aspects of balancing, such as the basic principles of the process by which an optimum state of balance is achieved in a rotor, balancing methods and machines, and definitions of balancing terms. The discussion is limited to those principles, methods, and procedures with which an engineer should be familiar in order to understand what is meant by "balancing." Finally, a list of definitions is presented at the end of it.

In addition to unbalance, there are many other possible sources of vibration in rotating machinery; some of them are related to or aggravated by unbalance, and so, under appropriate conditions, they may be of paramount importance. However, this discussion is limited to the means by which the effect...