Fluke 810 User Manual page 144

810
Users Manual
Balancing Resonance Speed(s). A rotating speed that
corresponds to a natural resonance frequency.
Balanced Condition. For rotating machinery, a condition
where the shaft's geometric centerline coincides with the
mass centerline.
Balancing. A procedure for adjusting the radial mass
distribution of a rotor so that the mass centerline
approaches the rotor geometric centerline.
Blocking. The installation of a permanently affixed
mounting block is known as "blocking" a machine.
Cited Peak. An abnormal vibration magnitude/level
identified (or cited) by the Fluke 810 diagnostic engine.
Cited Peaks are marked with red in the Tester and in the
Viewer Software. Each fault diagnosed can be related to
several cited peaks.
CPM. Cycles per minute. Cycles per minute is a measure
of the number of times a particular event occurs within a
one minute period. Used as the horizontal axes of the
spectra and time waveform plots within the Tester.
Displacement. When measuring machinery vibration,
displacement represents the actual distance the vibration
causes the part in question to move. It is measured in
thousandths of an inch (mils) in the English system and in
millimeters (mm) in the metric system.
C-2
Frequency. The number of events that occur within a
fixed time period, frequency is also calculated as the
reciprocal of time (for example, one divided by the time
interval). Frequency is typically expressed in terms of
Hertz (Hz), but can also be expressed as cycles per
minute (cpm) or revolutions per minute (RPM) when
multiplying Hz times 60. It can also be represented as
multiples of turning speed, or "orders," where frequency
in RPM is divided by the turning speed of the machine.
Frequency Domain. Since vibration exists within the time
domain, a vibration signal is represented as a time wave
form if viewed on an oscilloscope. If plotted, the time
waveform would represent a plot of amplitude vs. time. If
the waveform were transformed to the frequency domain,
the result would be a spectrum representing a plot of
amplitude vs. frequency.
Imbalance. A condition on rotating equipment where the
center of mass does not lie on the center of rotation.
Imbalance can severely reduce bearing life as well as
cause undue machine vibration.
Looseness. Mechanical looseness can be either of two
types: rotating and non-rotating. A rotating looseness is
caused by excessive clearance between rotating and
stationary elements of the machine such as in a bearing.
Non-rotating looseness is a looseness between two
normally stationary parts, such as a foot and a
foundation, or a bearing housing and a machine.