Oil Separator

An oil separator removes oil from the discharge gas and returns it to the crankcase, instead of letting it travel around the circuit and collect in the evaporator where it reduces heat transfer and can starve the compressor.

The DOSA series is a detachable oil separator, meaning the internal element can be removed for cleaning or replacement without cutting the shell out of the line. On plant that runs continuously, that is the difference between a service job and a shutdown.

Sizes run from DOSA-5301 to DOSA-6305, with ODF connections from 1/2 inch to 2-1/8 inch, oil return connections in 1/4 inch or 3/8 inch SAE, and volumes from 1.70 L to 8.30 L. Pre-charge is 400 mL or 800 mL depending on size. Capacity is published at -40 C and +5 C for R404A/R507, R134 and R22/R407C, running from 5.31 kW to 108.6 kW - the wide spread reflects how much the separation efficiency and the gas density change across that temperature range.

Two installation points decide whether a separator works. First, the oil return line needs a restriction (a capillary or an orifice) sized to the compressor so that gas does not blow through it; an unrestricted return turns the separator into a bypass. Second, the return should go to the compressor crankcase at a point below the oil level, ideally through a sight glass so the return rate can be checked.

Mount vertically, flow downwards through the element, and keep the return line short and sloping towards the crankcase.