Appendix C Vibration Measurements - Single Screw Compressor - Emerson VILTER VSS Installation, Operation And Service Manual

Appendix C • Vibration Measurements - Single Screw Compressor
Vibration Measurements - Single
Screw Compressor
Scope
The vibration criteria provided applies to broad-band
vibration measurements taken on the bearings and
housing of the Single Screw compressors under steady-
state operating conditions within the nominal operating
speed range in addition to the piping and tubing on the
compressor unit. They relate to both acceptance testing
and operational monitoring. The evaluation criteria is in-
tended to apply to both continuous and non-continuous
monitoring situations. The scope does not address the
diagnostic evaluation of the condition of the roller ele-
ment bearings. The criteria are applicable only for the
vibration produced by the machine itself and not for
vibration which is transmitted to the machine set from
external sources. Information used in this chapter was
taken from ISO Standard 10816-3, Mechanical Vibration
– Evaluation of Machine Vibration by Measurements on
Non-Rotating Parts – Part 3, First Edition, 1998.
Measurement Procedures and
Operational Conditions
Measurement Equipment
The measurement equipment shall be capable of mea-
suring broad-band rms vibration with flat response over a
frequency range of at least 10 Hz to 1000 Hz. Depending
on the vibration criteria, this may require measurements
Figure C-1. Compressor Bearing Vibration Measurement Location
VSS/VSR/VSM/VSH/VSSH Compressor • Installation, Operation and Service Manual • Emerson • 35391S
of displacement or velocity or combinations thereof.
Care should be taken to ensure that the measuring sys-
tem is not influenced by environmental factors such as:
• temperature variations;
• magnetic fields;
• sound fields;
• power source variations;
• transducer cable length;
• transducer orientation.
Particular attention should be given to ensure that the
vibration transducers are correctly mounted and that
such mountings do not degrade the accuracy of the
measurements.
Compressor Measurement locations
Measurements taken on the compressor will usually be
taken on exposed parts that are normally accessible.
Care shall be taken to ensure that measurements rea-
sonably represent the vibration of the bearing housing
and do not include any local resonances or amplification.
The locations and directions of vibration measurements
shall be such that they provide adequate sensitivity to
the machine dynamic forces. Typically, this will require
two radial measurement locations on each bearing cover
on the gate rotor housing support and back plate (near
the compressor shaft). Vertical and horizontal directions
are preferred for Single Screw compressors. The spe-
cific locations and directions shall be recorded with the
measurement.
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