A number of sophisticated procedures for balancing flexible rotors have been developed during the past two decades. For a variety of reasons, none of these methods has gained general acceptance by practicing balancing engineers. Several of these balancing techniques require a great deal of operator insight and expertise. This has tended to discourage many potential users where this expertise was not already available in-house, particularly where balancing is required as a production operation. In other cases (for example large steam turbines), the machinery owner has had to rely on the manufacturer to provide this balancing expertise when it is needed often resulting in excessive downtime and maintenance costs.

Other balancing methods have been developed which are more systematic so as to reduce the level of expertise required of the user. Unfortunately, these methods have invariably required the collection of large quantities of data and very complex computations. Thus, originally, this data was taken by hand and transcribed for input to a large computer. The results of the balancing calculations were returned some time later for use by the balancing engineer. Such an operation was clearly not conducive to effective commercial application. With the development of minicomputers, the situation was alleviated to a certain extent through the use of more accessible, and even on-line computers to perform these calculations. However even with these minicomputers, in-place flexible rotor balancing facilities were expensive and inconvenient to assemble, and in situ balancing of flexible rotors was impractical if not impossible.

The subsequent development of the microcomputer has made in situ balancing of flexible rotors a possibility. This paper describes a completely portable, microcomputer-based flexible rotor balancing system that uses influence coefficient balancing and the Unified Balancing Approach two of the systematic methods which have been shown to be very effective for balancing flexible rotors. The results of a series of verification tests are also presented.

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