Principles of Operation
When gas leaves the compressor, the gas contains heat and compressor lubricant. Both must
be removed. From the compressor, the hot gas with its entrained oil flows over the motor
winding, where the gas loses some of its suspended oil, then out of the shell and through one
circuit of a three-circuit heat exchanger, where it is cooled by circulating coolant (water/30%
ethylene glycol). Next, the gas passes through the oil separator and the adsorber for oil and
moisture removal. From the adsorber, the high-pressure gas is supplied to the cold head
through gas lines.
Through the system gas return line, low-pressure gas from the cold head flows into the
compressor.
A gas line containing an internal by-pass solenoid valve connects the high-pressure line to the
low-pressure line. The by-pass valve will open to prevent overloading the motor when the
system gas lines are not connected to the compressor.
Oil is separated from the gas in three stages. The first stage is by precipitation when the gas
passes over the motor windings. The second stage is in the oil separator whose element
collects oil mist from the gas; oil is agglomerated and returned to the compressor. The third
stage is the adsorber that removes any remaining oil the gas is carrying.
Oil collected in the separator flows back to the compressor through a capillary tube. The
differential gas pressure across the system is the moving force, and the capillary size limits
the amount of gas bypassed. The small amount of oil collected in the adsorber remains there
and is removed only by replacing the adsorber.
Oil in the compressor capsule also collects heat. The shell-wrapped heat exchanger removes
heat from the compressor motor and from the warm oil by direct conduction through the
compressor shell. Gas pressure pushes oil through the heat exchanger’s outer tubes that cool
the warm oil from the compressor. This cooled oil is then reinjected into the gas return line,
which returns the oil to the compressor to reabsorb heat and lubricate the compressor.
The circulating coolant is cooled by room air moved by a fan through an air heat exchanger and
out the top of the compressor unit.
The coolant system is sealed and requires no regular maintenance.
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