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REFRIGERANT PIPING WORK
Selection of Refrigerant Piping Size
The connection piping size for refrigeration unit is, in principle, as shown below,
but each installation should be determined by calculating pressure loss of the piping
and refrigerant flow speed and making sure no problem occurs in the cooling
capacity and oil return.
As refrigeration unit using CO2 refrigerant incurs pressure higher than when using
traditional refrigerants, it is necessary to choose adequate materials. Make sure that
piping's are connected to the appropriate pressurized equipment (EN378-2).
Prevent contamination of foreign objects
such as dust, metal powder, oxide scale,
etc.
Since the compressor consists of high precision components, contaminants
generate scratches on the sliding surfaces, thereby increasing gas leak,
deteriorating performance, and causing excessive wear and seizure.
–
Flow nitrogen gas during welding.
–
Piping inside and outside must be clean.
Dehydration of circuits
This operation must be carried out with all valves open (including solenoid
valves) with connection to a vacuum pump:
–
of the low pressure side
–
of the high pressure side
The quality of drying should not be judged by the speed at which the level of
vacuum is reached but on the effective time it is held (24 hours at 0.7 mbar is a
good standard).
The total increase in pressure after that period should not be more than 2.6 mbar.
The residual moisture in the system should be less than 10 ppm.
When the installation is under vacuum, an insulation check of the motor should
not be carried out nor should the compressors be started before at least 1 bar of
fluid pressure is reintroduced.
This is to prevent motor winding damage.
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