070.610-IOM (JUL 21)
Page 44
RWF II Rotary Screw Compressor Units
Maintenance
Grease compatibility
The motor nameplate will list the manufacturer’s recom-
mended grease. Use of grease other than recommended
by the manufacturer may result in premature motor failure
and denied warranty claims. The proper grease is available
through the Baltimore Parts Center or motor supplier.
Troubleshooting guide
Successful problem solving requires an organized ap proach
to define the problem, identify the cause, and make the
proper correction. Sometimes it is possible that two
relatively obvious problems combine to provide a set of
symptoms 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
problem effectively and make the necessary correc tions:
1.
Define 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 first step in effective problem solving is to define the
limits of the problem. If, for example, the compressor pe-
riodically 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 measure
would appear to be a readjustment of the liquid injection
system. Lowering the equalizing pres sure on the thermal
expansion valve would increase the refriger ant feed and
the oil temperature should drop.
If the high oil temperature was the result of high suction
superheat, 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 injection system may have a tendency to overfeed.
The high suction superheat condition, moreover, may only
be temporary. When system conditions return to normal
the unit’s liquid injection 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
normal operating conditions. If an Operating Log has been
maintained the log can help determine what constitutes
normal operation for the compressor unit in that particular
system.
The following list of
abnormal system conditions can cause
abnormal operation of the RWF II compressor unit:
1.
Insufficient 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
cooler.
7.
Liquid return from system (slugging).
8.
Refrigerant underfeed or overfeed to evaporators.
9.
Blocked tubes in water-cooled oil cooler from high
mineral content of water.
10.
Insufficient 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 operation. Delete any items
which do not relate to the symptom and separately list
Sensor
Voltage
200 psi
500 psi
Range - psig*
Range - psig*
Low
High
Low
High
1.0
29.92"
9.57"
29.92"
4.1
1.1
29.92"
0.3
29.92"
16.6
1.2
29.92"
5.3
17.10"
29.1
1.3
19.74"
10.3
4.1
41.6
1.4
9.57"
15.3
16.6
54.1
1.5
0.3
20.3
29.1
66.6
1.6
5.3
25.3
41.6
79.1
1.7
10.3
30.3
54.1
91.6
1.8
15.3
35.3
66.6
104.1
1.9
20.3
40.3
79.1
116.6
2.0
25.3
45.3
91.6
129.1
2.1
30.3
50.3
104.1
141.6
2.2
35.3
55.3
116.6
154.1
2.3
40.3
60.3
129.1
166.6
2.4
45.3
65.3
141.6
179.1
2.5
50.3
70.3
154.1
191.6
2.6
55.3
75.3
166.6
204.1
2.7
60.3
80.3
179.1
216.6
2.8
65.3
85.3
191.6
229.1
2.9
70.3
90.3
204.1
241.6
3.0
75.3
95.3
216.6
254.1
3.1
80.3
100.3
229.1
266.6
3.2
85.3
105.3
241.6
279.1
3.3
90.3
110.3
254.1
291.6
3.4
95.3
115.3
266.6
304.1
3.5
100.3
120.3
279.1
316.6
3.6
105.3
125.3
291.6
329.1
3.7
110.3
130.3
304.1
341.6
3.8
115.3
135.3
316.6
354.1
3.9
120.3
140.3
329.1
366.6
4.0
125.3
145.3
341.6
379.1
4.1
130.3
150.3
354.1
391.6
4.2
135.3
155.3
366.6
404.1
4.3
140.3
160.3
379.1
416.6
4.4
145.3
165.3
391.6
429.1
4.5
150.3
170.3
404.1
441.6
4.6
155.3
175.3
416.6
454.1
4.7
160.3
180.3
429.1
466.6
4.8
165.3
185.3
441.6
479.1
4.9
170.3
190.3
454.1
491.6
5.0
175.3
195.3
466.6
504.1
At 0 psig
1.094 V
1.494 V
0.968 V
1.268 V
*
Below 0 psig measured in inches of mercury.
Table 16: Pressure transducer voltage-psi conversion
