Profroid MiniCO2OLcompact Notice D'instructions page 72

11.4.2 Oil management and oil trap
The specificity of the ejector system is that all MT compressors are connected on their suction side to the upper, part of the receiver. They thus
suck oil free vapors. The oil (100% miscible with CO2) remains inside the liquid receiver. Although the system is equipped with oil separation system
using high efficiency coalescent filter on the discharge line of the MT compressors, a small portion of the oil goes into the refrigeration lines and
comes back through the ejector into the liquid receiver.
The consequence is an increase in oil concentration inside the receiver, and a lower oil level inside the oil receiver and ultimately inside the
compressors, which can lead to severe issues after a high number of running hours.
The solution to avoid this phenomenon is to position an "oil trap" at the connection from the consumers, right before the ejectors in order to
capture the oil and deliver it back to the compressors.
In reality, the oil fraction collected in the oil trap is injected into the suction line of the LT compressors, which will inject it into the suction side
of the MT compressors (specific version of booster compressors for LT application)
See below schematics
to ejector
MT suction from consumer
oil pocket
V15
MT
Compressor
LT
Compressor