mycom 200VMD - Page 125

2205Q2JE-HO-S6-N_2020.01.
Chapter 6 Troubleshooting
SCV-series Screw Compressors
6-8
Trouble Direct causes Factors Actions
10
Capacity
control
malfunction
Capacity control
hydraulic line defect
Maladjustment of oil
flow controller valve
Readjust it.
Leak and clogging
in solenoid valve
gland and oil pipes
Remove factors. Check oil
contamination level and replace oil
as necessary.
Unloader piston
does not move.
(A defect of the
capacity control
hydraulic line is one
of the causes, but
described
separately.)
Damaged cap seal
for unloader piston
Check oil contamination level and
replace oil as necessary.
Replace O-ring, cap seal, etc.
Pinched cap seal
Replace O-ring, cap seal, etc.
Worn cap seal
Check oil contamination level and
replace oil as necessary.
Replace O-ring, cap seal, etc.
Refrigerant gas
retention in
unloader cylinder
Stop compressor. Operate oil pump
and repeat loading and unloading to
purge refrigerant gas from cylinder.
For liquid flow-back operation,
remove the causes.
For malfunction of oil heater and
other devices on control circuit,
replace them.
11
Abnormal
vibration
and/or
noise of
compressor
Insufficient
alignment between
compressor shaft
and motor shaft
If vibration value is
higher in the axial
direction,
insufficient
alignment might be
the cause.
Realign the shaft-center.
If abnormal vibration and noise fre-
quently occur in monocoque unit,
hot alignment is recommended.
(operate compressor at design
conditions once to increase shaft
temperature and realign before the
temperature decreases).
Large axial runout
of Male rotor
Uneven tightening
for thrust bearing
glands
If loose locknuts exist and no other
fault is found in parts such as thrust
bearing, tighten locknuts evenly.
Loose thrust
bearing
Forgetting to bend lock washer claw
or wear of thrust bearing rolling
element (ball) can be considered.
→Check for any defects in thrust
bearings. If there are any defects,
replace it. Then perform end
clearance adjustment as well as
axial runout check, and
reassemble it.
Imprecision in
dynamic balance of
rotors
If no other causes for abnormal
vibration are found, and if on-site
overhaul has been repeatedly
performed, imprecision in rotor
dynamic balance might be the
cause of abnormal noise and
vibration. If this is the case,
overhaul and inspect compressor
where rotor dynamic balance
measurerment and adjustment is
feasible.