A basic principle of machinery vibration analysis is evaluating whether specific vibration amplitudes are excessive and, if so, to what degree. Many criteria provided by manufacturers and other entities simply say that no single spectral peak should exceed a prescribed amplitude. Others are even more basic and establish overall broadband limits for a given machine or test location. Still others get more specific and creative by establishing amplitude limits within each of a handful of frequency bands. There also are long-established severity charts that present contours of amplitude versus frequency, with provisions that account for machine type (reciprocating, etc.) and size.
A major problem with simplified approaches is that serious discrepancies can occur. One machine can appear to be bad because it produces one very high vibration tone, which is proven to be benign. Another machine can easily meet general amplitude criteria while producing a strong series of high-frequency ball bearing tones indicating serious bearing wear. The solution is to let the machines dictate what is acceptable.
The attached article is from the April 2010 issue of Plant Services. Take a read to see if this solution can apply to you.