a relatively small distance a disk is located at one end of the annular chamber with a bubble fence surrounding the disk and an annular space between the disk and the bubble fence conveying the excess oil to the drain line the second annular space outboard of the first annular space collects the oil for supply to the exterior equipment fig1 is a sectional elevation view of the swirl vessel operating at straight level flight fig3 is a sectional elevation of the swirl vessel operating at knife edge flight fig4 is a sectional elevation of the swirl vessel operating at inverted flight and fig5 is a sectional elevation of a tank containing the swirl vessel exterior to the equipment shown there is an oil pump receiving oil from supply line 10 for supply to an engine and equipment treating the oil which is then returned through return line 12 this oil enters the swirl vessel 14 and passes to an annular inlet 16 fig2 where it is distributed around the circumference the oil then passes through a plurality of flat plate injectors 18 and directed tangentially into a substantially cylindrical chamber 20 having a chamber wall 22 this oil forms a free vortex surface 24 with a high level 26 in oil tank 28 or vortex surface 30 with low level 32 in oil tank 28 the oil supply is taken from annular space 34 through supply line 10 a centrally located swirl vessel drain 36 permits excess oil to drain into the interior of tank 28 a centrally located disk 38 is supported.