data in the frequency domain (see FFT) and may also include the study of time domain (time waveform) data.  Such analysis may be undertaken routinely as an integral part of a vibration based Predictive Maintenance program.  It may also be undertaken for ad-hoc analysis of suspect rotating machinery, irrespective of the machine's inclusion in a formal monitoring program. Vibration Monitoring Regular monitoring of machinery vibrations undertaken as part of a Predictive Maintenance Program.  Readings are compared with past levels, with significant change as an indicator of developing machinery faults. The objective is to provide valuable lead-time for maintenance planning.  A comprehensive monitoring program usually includes vibration analysis. Visual Inspection Visual inspection refers to subjective inspection of machinery, and employs only the human senses. Sometimes it is referred to as "look-listen-feel" checks. Warning Time Warning time is considered equivalent to the P-F interval. See P-F interval . Wear (abrasive) Abrasive wear (often referred to as wear) is the progressive removal of material, which results from the ingress, and presence of (foreign) particles (three-body wear). The surfaces become dull to varying degrees. In the case of very fine particles (dust), the surface may become shiny (polished). Wear (adhesive) Adhesive wear (also referred to as smearing, skidding, galling) is defined as the transfer of component surface material from a location on one contacting surface to a location on the other contacting surface.  The process requires surface-parallel motion (sliding) in the contact, and is often accompanied with high friction heat.  Little, or bad lubrication,