Frick RWB II, Установка, эксплуатация и обслуживание

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RWB II ROTARY SCREW COMPRESSOR UNITS
MAINTENANCE
S70-200 IOM
Page 34
PE-1 PE-5 PE-2 PE-3 PE-4
ISOLATION VALVES
PIPE PLUGS
GAUGE/PURGE VALVES
TROUBLESHOOTING GUIDE
Successful problem solving requires an organized ap proach
to defi ne the problem, identify the cause, and make the prop er
correction. Sometimes it is possible that two rel a tive ly ob vi ous
problems combine to provide a set of symp toms that can
mislead the troubleshooter. Be aware of this possibility and
avoid solving the “wrong problem”.
ABNORMAL OPERATION
ANALYSIS and CORRECTION
Four logical steps are required to analyze an opera tional
prob lem effectively and make the necessary correc tions:
1. Defi ne the problem and its limits.
2. Identify all possible causes.
3. Test each cause until the source of the problem is found.
4. Make the necessary corrections.
The fi rst step in effective problem solving is to defi ne the
lim its of the problem. If, for example, the compressor pe ri -
od i cal ly experiences high oil tempera tures, do not rely on
this observation alone to help identify the problem. On the
basis of this information the apparent corrective mea sure
would appear to be a readjustment of the liquid in jec tion
system. Lowering the equalizing pres sure on the thermal
expansion valve would increase the refriger ant feed and the
oil tem per a ture should drop.
If the high oil temperature was the result of high suction
su per heat, however, and not just a matter of improper liquid
injection adjustment, increasing the liquid feed could lead to
other problems. Under low load conditions the liquid in jec tion
system may have a tendency to overfeed. The high suc tion
superheat condition, moreover, may only be tem po rary. When
system conditions return to normal the units’ liq uid in jec tion
will overfeed and oil temperature will drop. In solving the
wrong problem a new problem was created.
When an operating problem develops compare all operat ing
information on the MAIN OPERATING SCREEN with nor mal
op er at ing con di tions. If an Operating Log has been main tained
the log can help determine what constitutes normal op er a tion
for the com pres sor unit in that par tic u lar system.
The following list of abnormal system conditions can cause
abnormal operation of the RWB II compressor unit:
1. Insuffi cient or excessive refrigeration load.
2. Excessively high suction pressure.
3. Excessively high suction superheat.
4. Excessively high discharge pressure.
5. Inadequate refrigerant charge or low receiver level.
6. Excessively high or low temperature coolant to the oil
cool er.
7. Liquid return from system (slugging).
8. Refrigerant underfeed or overfeed to evaporators.
9. Blocked tubes in water cooled oil cooler from high min er al
content of water.
10. Insuffi cient evaporator or condenser sizing.
11. Incorrect refrigerant line sizing.
12. Improper system piping.
13. Problems in electrical service to compressor unit.
14. Air and moisture present in the system.
Make a list of all deviations from normal plant operation and
normal compressor unit op er a tion. Delete any items which
do not relate to the symptom and sep a rate ly list those items
that might re late to the symp tom. Use the list as a guide to
fur ther investi gate the problem.
The second step in problem solving is to decide which items
on the list are possible causes and which items are ad di tion al
symp toms. High discharge temperature and high oil tem-
perature readings on a display may both be symptoms of a
prob lem and not casually relat ed. High suction su per heat or
a low receiver level, however, could cause both symp toms.
The third step is to identify the most likely cause and take
action to cor rect the problem. If the symptoms are not re lieved
move to the next item on the list and repeat the pro ce dure
until you have iden ti fi ed the cause of the prob lem. Once the
cause has been identi fi ed and con fi rmed make the nec es sary
correc tions.
SERVICING THE COLD-START VALVE
DO NOT ATTEMPT TO SERVICE
THE COLD START VALVE. PLEASE
CON TACT THE FRICK SER VICE
DE PART MENT.
PRESSURE TRANSDUCERS - TESTING
Pressure transducers, Figure 31, are located on a covered
manifold near the microprocessor console.
1. Shut down the compressor and allow pressures to
equal ize.
2. Isolate suction transducer PE-4 from the unit and de pres -
sur ize. NOTE: Recover or transfer all refrigerant vapor,
in accordance with local ordinances, before opening to
at mo sphere.
3. Measure the voltage of PE-4 on connector P4 (terminals
WHT and BLK) on the SBC with a digital volt me ter.
4. The voltage reading should be 1.48 VDC to 1.72 VDC at
standard atmospheric pressure (14.7 PSIA or 0 PSIG). When
checking transducers at higher elevations, an al low ance in
the readings must be made by subtracting ap prox i mate ly 0.02
VDC per 1000 feet of elevation above sea level. There fore,
if PE-4 is measured at 5000 feet elevation under rel a tive ly
nor mal weather conditions, the output voltage should differ
by 0.10 VDC to read between 1.38 VDC and 1.62 VDC.
Figure 31