Emerson Vilter VSH, Installation, Operation & Maintenance Manual

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Appendix C • Vibration Measurements - Single Screw Compressor
C − 3
VSS/VSM/VSH/VSSH • Installation, Operation and Maintenance Manual • Emerson • 35391SD
Figure C-3. Gaterotor Cross-Section VSS/VSR/VSMC Compressors
Evaluation
There are two evaluation criteria used to assess vibration
severity on various classes of machines. One criteria con-
siders the magnitude of observed broad-band vibration;
the second considers changes in magnitude, irrespec-
tive of whether they are increases or decreases.
Criterion 1: Vibration Magnitude
This criterion is concerned with defining limits for vibra -
tion magnitude consistent with acceptable dynamic
loads on the bearings and acceptable vibration trans-
mission into the environment through the support
structure and foundation. The maximum vibration mag-
nitude observed at each bearing or pedestal is assessed
against the evaluation zones for the support class. The
evaluation zones have been established from interna-
tional experience.
The following evaluation zones are defined to permit a
qualitative assessment of the vibration of a given ma-
chine and provide guidelines on possible actions.
• Zone A: The vibration of newly commissioned ma-
chines would normally fall within this zone.
• Zone B: Machines with vibration within this zone
are normally considered acceptable for unrestricted
long-term operation.
• Zone C: machines with vibration within this zone are
normally considered unsatisfactory for long term
continuous operation. Generally, the machine may
be operated for a limited period in this condition un-
til a suitable opportunity arises for remedial action.
• Zone D: Vibration values within this zone are nor-
mally considered to be of sufficient severity to cause
damage to the machine.
Numerical values assigned to the zone boundaries are
not intended to serve as acceptance specifications,
which shall be subject to agreement between Vilter
TM
manufacturing and the customer. However, these val-
ues provide guidelines for ensuring that gross deficien -
cies or unrealistic requirements are avoided. In certain
cases, there may be specific features associated with a
particular machine which would require different zone
boundary values (higher or lower) to be used