Sleeve Bearing Problems

Sleeve Bearing Problems - Sleeve bearings are in some ways much more forgiving and easier to analyze than rolling element bearings since there are no fundamental defect frequencies and the like to analyze. However, sleeve bearings also demand different techniques and insights that do not apply to rolling element bearings. For instance: Measuring vibration on the housing of a sleeve bearing is unreliable since the housing moves only a small fraction (perhaps 10% or even less) of what the shaft is moving. Vibration is due to mechanical forces being generated by the machine's rotation. In the absence of such forces (slow rotational speeds combined with excellent alignment and balance, for example), extensive wear can take place with absolutely no indication on a vibration spectrum - especially if the readings are taken on the housing. Unlike greased bearings, sleeve bearings usually have an oil system. If the oil flow stops or the oil becomes severely contaminated, failure can occur very quickly. What should be done with sleeve bearings to alleviate these concerns ? Oil analysis - This will monitor bearing condition far more accurately than vibration analysis will. Direct Shaft Vibration Readings - Although sometimes impractical or impossible, taking readings with a proximity probe, a shaft stick or shaft rider will give far more useful vibration data than readings taken on the housing since these techniques measure what the shaft is doing - not the housing. Time Domain - Looking at the raw time signals will give information on exactly how the shaft is moving and give visual notice of problems such as rubs that spectra will not give.