Principles of Operation
When helium gas leaves the compressor capsule, the gas contains heat and compressor
lubricant. Both must be removed. From the compressor capsule, the hot gas with its entrained
oil flows out of the shell and through the bulk oil separator. The gas next flows through one
circuit of a three-circuit, water cooled, heat exchanger, where it is cooled. Next, the gas passes
through the final oil separator and the adsorber for oil and moisture removal. From the adsorber,
the high-pressure helium gas flows to the cold head through the 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 relief valve (IRV) connects the high-pressure line to the low-
pressure line. The relief 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 gravity when the gas passes
through the bulk oil separator. The second stage is in the final 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 oil separators flows back to the compressor capsule through capillary tubes
and orifices. The differential gas pressure across the system is the moving force, and the
restriction 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.
Before being returned to the compressor capsule, the oil separated in the bulk oil separator
flows through the heat exchanger where it is cooled. It is then injected into the low pressure
side of the compressor capsule to adsorb heat and lubricate the compressor capsule.
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