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Moving forward to the second area of concern, the chemical
reactions and consequences thereof.
The chemical reactions are complex and dependent on many
variables but what we do need to consider is that these reactions
result in the formation of acids in the refrigeration system.
A chemical reaction can occur between the moisture, oil
and refrigerant, bringing about a decomposition which results in
hydrochloric and hydrofluoric acids being produced. These acids
create a host of issues.
We know that it is almost certain that if acid formation has
commenced, there will be some air or oxygen present in the
system. This will allow corrosion to take place. The first issue is that
products of corrosion will break away or be flushed away by the oil
in circulation and will start forming a ‘grinding paste’ in the oil. This
results in accelerated wear in the machine.
Refilwe, do you see that when you return a compressor to a
supplier and they find acids, the finding will be that there was
moisture and or air in the system indicating poor installation
procedure and inadequate evacuation?
The next aspect is copper plating. The crankshaft journal pictured
below is not made of copper but has been copper plated in the
system.Copper plating is a situation that arises when moisture and
acids are present in a system which is operating at high temperature.
Copper is dissolved from copper and brass components, and copper
ACRA
Crankshaft journal
with copper plating.
plates out as a layer of copper onto rubbing metal surfaces and steel
or iron surfaces.
As the plating gets thicker clearances are reduced. Oil
clearances being reduced creates lubrication issues. Friction then
increases which results in the compressor starting to run hot. In
addition, the copper plating may tear away in the system. These
pieces of copper will easily cause more damage.
Copper plating has been known to seize compressors and to lock
up oil pumps, causing their drive shafts to shear.
Yet another aspect that we need to consider is varnish and
sludge formation. As we have increased temperatures caused by
increased friction and possibly not condensable, these increases
in temperatures can cause the formation of sludges and varnishes
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RACA Journal I September 2020
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