Practical Solutions to Machinery and Maintenance Vibration Problems
Chapter 3, Detuning and Proving Resonance
Section 23, Summary of Approaches to Cure a Resonance Problem
After locating the resonant vibration magnifier, several possible solutions will work to alter the resonance frequency. The analyst would too often visualizes a solution that will work, such as changing the design or bracing the resonant part to make it more rigid, thereby increasing the natural frequency range well beyond that of the source vibration frequency. Yet, with a little more thought, the same part's resonance frequency can be changed, perhaps more easily and at considerably less expense, by removing an existing brace and making the part more flexible.
Therefore, do not immediately accept the first solution that will work. Instead, take the time to list four or five possible means to detune the part or otherwise solve the resonance problem. Some examples are:
1. Raise the part's resonant frequency by shortening its length or span between supports; increase diameter or depth of beam; decrease weight.
2. Lower the part's resonant frequency by removing a support to increase the span, decrease its diameter or depth of beam or add weight.
3. Change rpm or the resultant frequency (such as changing number of vanes), and so on.
4. Use a dynamic absorber on the resonant part.
Visualize several solutions before choosing one; then, consider which method will be:
Caution: Very large structural members, such as large concrete bases and floors, very rigid beams and so on, usually are not best to detune. Instead, reduce the large vibration at its source. (See later sections: "Detuning Resonant Part vs. Reducing Vibration At The Source" and "Using Shaker To Determine If Fault Is Due To Weak Structure Or Vibration Source.)
This textbook contains only part of the information in our Practical Vibration Analysis seminar.