Vacuum Pump Maintenance - Electrolux 5995502399 Service Manual

Sealed System

Vacuum Pump Maintenance

It is absolutely essential to maintain your vacuum pump
according to the manufacturer's instructions, includ-
ing required oil changes at the recommended intervals.
Vacuum pump oil should always be changed after
evacuating a contaminated system. Vacuum pump
performance should be checked periodically with a
micron gauge.
Vacuum pump suppliers may or may not recommend
changing the vacuum pump oil to the same type that's in
the system being evacuated. Some manufacturers may
recommend a vacuum pump that's dedicated to
R-134a systems.
Robinair has stated that their current and discontinued
vacuum pump models, using mineral oil currently
specified for use in their vacuum pumps, can be used to
evacuate R-134a/Ester oil systems. Robinair also states
that it is acceptable to alternate between evacuating
R-12/mineral oil and R-134a/Ester oil systems without
adversely effecting the vacuum pump's performance.
For other brands of vacuum pumps, check with the
manufacturer for restrictions and guidelines when using
with R-134a.
If you use a vacuum pump with mineral oil to
evacuate an R-134a system, it is ABSOLUTELY
ESSENTIAL to have a shut-off valve between pump
and your manifold gauge set. The hand valve must
be closed during all times when vacuum pump is
not operating. This will prevent migration of
mineral oil vapor into R-134a/Ester oil systems. If
the vacuum pump should stop during evacuation
for any reason, the hand pump shut-off valve must
be closed immediately.
VACUUM CHART
Vacuum
Inches Hg.
28.940
29.530
29.832
29.882
29.901
29.915
29.917
29.919
To achieve the required 29.9 inch (500 micron) vacuum,
a properly maintained two-stage vacuum pump in good
condition is required. A two stage pump can reach a
deeper vacuum than a single stage because the exhaust
from the first pumping stage is discharged into the
second pumping stage. This means the second stage
begins pumping at a lower pressure so a lower ultimate
vacuum can be achieved.
Figure 7-22. Two Stage Vacuum Pump
7-22
Boiling Point
Microns
of Water °F
25000 77.9
10000 52.0
4600 32.0
1000 1.0
500 -11.2
150 -32.8
100 -38.2
50 -49.0