mycom 4032**C Series Instruction Manual page 111

12: Compressor generates abnormal vibration and/or sound (continued)
Direct cause
Foreign substances
entering the
compressor
Damaged thrust
bearings.
Resonance vibration
Compound 2-stage Screw Compressor 4032**C
Root cause
Welding spatter, etc.
flowing from upstream
side
Tools and/or waste
cloth left uncollected
after overhauling
Deterioration over time
(operated beyond
recommended time of
replacement)
Operation with liquid
flow-back
Entry of foreign
substances
Excessive thrust stress
other than above
・High suction
pressure/intermediate
pressure exceeding
the level set by
operating conditions
Faulty assembly
* Lock nuts tightened
insufficiently, lock
washer tooth not
bended, rotation
stopper not set to
thrust bearing gland,
gland not assembled,
etc.
This occurs when the
frequency of vibration
comes close to the
natural frequency of
any component in the
entire vibrating system,
including pipes and
supports.
6-11
2201Q4JE-MY-C9-N_2018.01.
Action
Check suction strainer and/or oil filters. Replace
element if defective.
Overhaul the compressor.
Collect foreign substances and identify their
sources. Then take necessary actions.
The time for replacement depends largely on
operating conditions (low pressure or high
intermediate pressure will make the life shorter,
etc.) and/or oil management conditions. In case of
a typical refrigeration application which basically
operates in a stable continuous mode, inspect and
replace them every 40,000 hours or 5 years,
whichever comes first.
For details, see Chapter 5, Section 5.2.3 in this
manual.
Refer to causes of "Liquid flow-back during
startup" and "Liquid flow-back during operation" in
item 12.
Refer to causes of "Foreign substances entering
the compressor" above.
Re-examine operating conditions, and improve if
possible.
If difficult to improve, review maintenance interval.
Tighten lock nuts by using specified torque or
torque angle (see Chapter 7, "7.3 Tightening
Torques for Bolts and Nuts" in this manual).
Be sure to record data on the assembly check
sheet to prevent omission of work steps.
In many cases, this symptom is caused by change
in installation environment (such as change in
piping routes or additive installation of devices in
the machine room, oil level change, etc.)
→If occurrence of resonance vibration is a
suspected, contact our service center.
Chapter 6 Troubleshooting