GLOSSARY OF TERMS: Condition Monitoring

Nov. 13, 2012

Meggitt Sensing Systems, a provider of industrial sensing systems, contributed the terms and definitions for this word search.

ALIGNMENT: Positioning two or more machines so that the rotational centerlines of their shafts are colinear at the power of transmission point under operating conditions.

ALIGNMENT TARGETS: Desired intentional misalignment of MTBM (Machine To Be Moved) to compensate for thermal growth and/or dynamic loads. Most commonly specified as coupling target

ANGULARITY: The angle between two machine shaft centerlines. For spacers, the angle between each shaft and the connecting element (shaft) at each flex plane.

AVERAGE: In vibration analysis, an average usually refers to the process whereby the vibration software will, after converting waveforms into spectrums via FFT, add the resultant spectrums together and then divide by the number of spectrums added together. The result is an “averaged spectrum.”

BAND: A band is simply a range of frequencies, e.g. a band from 0 Hz, to and including 5 Hz, is a band that is 5 Hz wide.

BAND PASS FILTER: A filter that blocks all data above and below its defined band.

COPLANAR: Lying or acting in the same plane.

CONDITION MONITORING: The use of specialized equipment to deduce the actual condition of equipment as it pertains to its fitness for continued use. Condition monitoring is the foundation of Predictive Maintenance and the two terms are sometimes used interchangeably.

FMAX: Fmax stands for “maximum frequency.” It is the high frequency boundary for a set of data.

FMIN: Fmin stands for “minimum frequency.” It is the low frequency boundary for a set of data.

FREQUENCY MARKERS: These are visible marks that can be overlaid on a spectrum at specific frequencies to help identify likely machinery problems.

OFFSET: Distance between rotational centerlines at any given normal plane. For short coupling (short flex) usually displayed at the coupling center.

PEAK-TO-PEAK: The measure of vibration amplitude in a waveform, from the negative peak to the positive peak.

SHIM: A thin piece of metal material inserted between the base and machine feet to produce precise vertical adjustments of the machine centerline.

SOFT FOOT: A term used to describe any condition where tightening or loosening the bolt(s) of a single foot distorts the machine frame. Must be corrected prior to final alignment.

STAT: A short form of “stationary machine.” The stationary machine’s centerline is used as the reference line to measure the misalignment of MTBM (Machine To Be Moved).

THERMAL GROWTH: Movement of shaft centerlines associated with (or due to) a change in machinery temperature between the static and operating condition.

TOLERANCE: The maximum permissible deviation from a specified alignment position, defining the limits of offset and angularity.

UNBALANCE: A measure that quantifies how much the rotor mass centerline is displaced from the centerline of rotation.

WAVEFORM: In vibration analysis, a waveform is a display of vibratory energy over time.

LUDECA (, a provider of preventive, predictive and corrective maintenance solutions including machinery laser alignment, vibration analysis, and balancing equipment, provided the terms and definitions for this word search.

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