SPM Machine Guard MG4-REF11A, Инструкция по эксплуатации

Страница: 24 / 32

22 Machine Guard MG4-REF11 A
SPM Instrument AB • Box 504 • SE-645 25 Strängnäs • Sweden Technical data are subject to change without notice.
Tel +46 152 225 00 • Fax +46 152 15075 • info@spminstrument.se • www.spminstrument.com ISO 9001:2000 certified © SPM 2017-09. 71947 B
VIB – Vibration severity monitoring
Machine vibration is a complex oscillating movement which can be measured as displacement,
acceleration, or as velocity. The original ISO standard 2372 concerning machine condition monitor-
ing by means of vibration measurement defines
vibration severity as the RMS (root mean square)
value of vibration velocity, measured over a frequency range of 10 to 1000 Hz. The revised ISO
standard 10816 basically recommends the same type of measurement but allows variations of the
frequency range.
Vibration severity is the best indicator of the energy contents of machine vibrations and thus of
the destructive forces acting on the machine structure. The measuring unit is mm/s (inch/s). The
RMS value displayed by the MG4-REF11A is a good general indicator of machine condition, but
it does not allow conclusions as to the causes of excessive machine vibration. The cause can be
unbalance, misalignment, structural weakness or a combination of these.
The measuring point has to be selected so that the transducer delivers a representative signal.
Normally the transducer is mounted on a bearing housing. In most rotating machines, the radial
forces are dominant and are measured in horizontal direction. Some machine structures are weaker
in the axial direction, so a measurement in axial direction will yield a more representative signal.
The ISO standard also contains a table of limit values for different machine classes (see next page)
which allow an evaluation of the vibration severity measured on a particular machine. MG4-REF11A
uses the ISO limit value as alarm level A1 (max) for the lower limit of “unacceptable” vibration and
for status indication (green/red). The alarm level A2 (min) is default 0.5 mm/s (green/red alarm).
mm/s RMS
Measuring time
1–15 seconds
0