What is vibration analysis?
Vibration analysis is a technique that many field service providers and equipment end-users employ as part of their condition monitoring programs to support a "predictive maintenance" philosophy. This attempts to find a compromise between the typical extremes of "breakdown maintenance" - only performing repairs when absolutely necessary due to a failure - and "preventative maintenance" - performing overhauls at regular intervals regardless of necessity - by identifying potential problems as early as possible allowing for sufficient time to plan and act accordingly before they become potentially catastrophic. The ultimate goal is to reduce maintenance costs and increase operational availability without sacrificing reliability. Other complimentary technologies include ultrasonic analysis, infrared analysis, oil analysis, and electrical circuit evaluation / insulation resistance testing.
A significant portion of the technology as we know it today was originally developed for the US navy's submarine fleet during the Cold War to help their equipment run as smoothly and therefore as quietly as possible to help avoid detection. The advent of personal computers also contributed greatly towards bringing vibration analysis into the main-stream by providing systems which were sufficiently powerful yet compact and rugged but also cost effective and user-friendly enabling the transition from laboratory research and development applications to routine field level usage. It has since become one of the most widely adopted tools for maintenance, reliability, and engineering departments in process plants.
The general concept is to measure the vibratory response of a machine or structure, decompose it into frequency/amplitude content - typically represented by waveform and spectral data plots - and use this information to help identify the cause (or causes) of the vibration based on knowledge/assumption of the forces which may be present either in a healthy operating condition or due to defects. Vibration analysis is particularly suited to identifying mechanical faults in rotating equipment but also has applications for static equipment as well as identifying electrical faults. By regularly measuring vibration on equipment in a consistent fashion a trend can be developed to help distinguish normal versus abnormal vibration behavior and to monitor fault progression.
Among the most important components in a rotating system are the bearings as these form the interface between rotating and stationary parts. Therefore, evaluating the health of the bearings and identifying potential degradation is one of the primary goals of vibration analysis. The two most common types of bearings in rotating machines are "anti-friction" bearings (typically called rolling element bearings) and "hydrodynamic" bearings (typically called journal, sleeve or Babbitt bearings. Each type has its own characteristic fault frequencies which are a function of the geometry and design of the bearing. Other common sources of vibration in rotating machines include unbalance, misalignment, and looseness (either internal or external/structural). Specific types of equipment will also have additional forces which can cause vibration such as hydraulic/aerodynamic forces in pumps/fans and compressors, gear/belt forces in transmissions, as well as electromagnetic forces in generators and motors. Consequently, sound knowledge of the various components in the machine train is essential, namely the type and location of the bearings.
Want to learn more about vibration analysis or become certified in vibration analysis & alignment? We offer industry training at our NorthPoint Training Centre.