Vacuum Evacuation And Moisture Removal - Danfoss MLM Series Application Manuallines

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PPLICATION UIDELINES
Compressor connection
Vacuum evacuation and
moisture removal
36
I
NSTALLATION
When brazing the compressor fi ttings, do not
overheat the compressor shell, which could se-
verely damage certain internal components due
to excessive heating. Use of a heat shield and/
or a heat-absorbent compound is highly recom-
mended. For brazing the suction and discharge
connections, the following procedure is advised:
• Make sure that no electrical wiring is connected
to the compressor.
• Protect the terminal box and compressor
painted surfaces from torch heat damage (see
diagram).
• Use only clean refrigeration-grade copper tub-
ing and clean all connections.
• Purge nitrogen through the compressor in order
to prevent against oxidation and fl ammable con-
ditions. The compressor should not be exposed
to the open air for extended periods.
• Use of a double-tipped torch is recommended.
• Apply heat evenly to area
temperature is reached. Move the torch to area
and apply heat evenly until the brazing tempera-
ture has been reached there as well, and then be-
gin adding the brazing material. Move the torch
evenly around the joint, in applying only enough
brazing material to fl ow the full circumference of
the joint.
• Move the torch to area only long enough to
draw the brazing material into the joint, but not
into the compressor.
• Remove all remaining fl ux once the joint has
been soldered with a wire brush or a wet cloth.
Remaining fl ux would cause corrosion of the
tubing.
Ensure that no fl ux is allowed to enter into the
tubing or compressor. Flux is acidic and can cause
substantial damage to the internal parts of the
Moisture obstructs the proper functioning of the
compressor and the refrigeration system.
Air and moisture reduce service life and increase
condensing pressure, and cause excessively high
discharge temperatures, which can destroy the
lubricating properties of the oil. Air and mois-
ture also increase the risk of acid formation, giv-
ing rise to copper platting. All these phenomena
can cause mechanical and electrical compressor
failure.
For these reasons it's important to perform a
vacuum dehydration on the system to remove
all residual moisture from the pipe-work after
assembly;
FRCC.PC.015.A4.02
system and compressor.
The PVE oil used in MLZ compressors is highly hy-
groscopic and will rapidly absorb moisture from
the air. The compressor must therefore not be left
open to the atmosphere for a long period of time.
until the brazing The compressor fi tting plugs shall be removed
just before brazing the compressor.
!
Before eventual unbrazing the compres-
sor or any system component, the refrigerant
charge must be removed from both the high
and low pressure sides. Failure to do so may
result in serious personal injury. Pressure
gauges must be used to ensure all pressures
are at atmospheric level.
For more detailed information on the appropriate
materials required for brazing or soldering, please
contact the product manufacturer or distribu-
tor. For specifi c applications not covered herein,
please contact Danfoss for further information.
MLZ and MLM compressors are delivered with
< 100 ppm moisture level. The required mois-
ture level in the circuit after vacuum dehydration
must be < 100 ppm for systems with an MLZ and
< 300 ppm for systems with an MLM compressor.
• Never use the compressor to evacuate the
system.
• Connect a vacuum pump to both the LP & HP
sides.
• Evacuate the system to a pressure of 500 μm Hg
(0.67 mbar) absolute.
• Do not use a megohm meter nor apply power to
the compressor while it's under vacuum as this
may cause internal damage.
Heat shield
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