Three Principles On Refrigerant Piping Work; Suspension Of Refrigerant Piping - Hitachi RAS-2-HVNP Service Manual

3. Piping work and refrigerant charge
3.1.2 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
•
•
•
1. Dry
Keep good dryness
•
•
2. Clean
No dust inside of
•
pipes
•
•
•
3. No leakage
No leakage shall
exist
3.1.3 Suspension of refrigerant piping
Suspend the refrigerant piping at certain points and prevent the refrigerant piping from touching weak parts of the building
such as walls, ceiling, etc. (If touched, abnormal noises may occur due to the vibration of the piping. Pay special attention
in case of short piping length).
A. Fire-proof section treatment.
B. Indoor unit.
In order to fix the piping to wall or ceilings use suspension and clamping systems as shown in the following figure.
54
Cause of failure
Water infiltration due to
insufficient protection at pipe
ends
Dewing inside of pipes
Insufficient vacuum pumping
time
Infiltration of dust or other
through the pipe ends.
Oxidation film during brazing
without blowing nitrogen.
Insufficient flushing by nitrogen
after brazing
Brazing failure
Failed flaring work and insuffi-
cient torque of squeezing flare
Insufficient torque of squeezing
flanges
SMGB0079 rev.0 - 01/2013
Presumable failure
Icing inside tube at ex. valve
(Water choking)
+
Generation of hydration and oxida-
tion of oil
↓
Clogged strainer, etc., insulation
failure and compressor failure
Clogging of expansion valve, capil-
lary tube and filter
→Oxidation of oil
→Compressor failure
↓
Insufficient cooling or heating com-
pressor failure
Refrigerant shortage
→Performance decrease
→Oxidation of oil
→Overheating of compressor
↓
Insufficient cooling or heating com-
pressor failure
Preventive action
Pipe protection
1 Pinching
2 Taping
↓
Flushing
↓
Vacuum Drying
• One gram of water turns into gas
(approx. 1000 lrs) at 1 Torn
• Therefore, it takes long time to
vacuum-pump by a small vacuum
pump
Pipe Protection
1 Mounting Caps
2 Taping
3 Pinching
↓
Flushing
Careful Basic Brazing Work
↓
Basic Flaring Work
↓
Basic Flange Connecting Work
↓
Air Tight Test
↓
Holding of Vacuum