3.1.4 Three principles on refrigerant piping work
In case of using refrigerant R410A in the refrigeration cycle, the refrigeration oil should be of a synthetic type one.
In order to avoid oxidation, pay much careful attention to basic piping work control to avoid infiltration of moisture or dust
during the refrigerant piping work.
Three principles
Cause of failure
Presumable failure
Preventive action
1
Dry
Keep good dryness
•
Water infiltration due to insufficient
protection at pipe ends
•
Dewing inside of pipes
•
Insufficient vacuum pumping time
Icing inside tube at expansion
valve
(Water choking)
+
Generation of hydration and
oxidation of oil
↓
Clogged strainer, etc., insulation
failure and compressor failure
•
Pipe protection
1 Pinching
2 Taping
•
Flushing
•
Vacuum drying
-
One gram of water turns
into gas (approx. 1000
lrs) at 1 Torr
-
Therefore, it takes long
time to vacuum-pump by
a small vacuum pump
2
Clean
No dust inside of
pipes
•
Infiltration of dust or other through
the pipe ends
•
Oxidation film during brazing
without blowing nitrogen
•
Insufficient flushing by nitrogen
after brazing
Clogging of expansion valve,
capillary tube and filter
Oxidation of oil
Compressor failure
↓
Insufficient cooling or heating
compressor failure
•
Pipe protection
1 Mounting caps
2 Taping
3 Pinching
•
Flushing
3
No leakage
No leakage shall exist
•
Brazing failure
•
Failed flaring work and insufficient
torque of squeezing flare
•
Insufficient torque of squeezing
flanges
Refrigerant shortage
Performance decrease
Oxidation of oil
Overheating of compressor
↓
Insufficient cooling or heating
Compressor failure
•
Careful basic brazing work
•
Basic flaring work
•
Basic flange connecting
work
•
Air tight test
•
Holding of vacuum
3 Piping work and refrigerant charge
Piping work connection considerations
SMGB0091 rev.2 - 11/2015
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