Ring Oil Recirculation System The Nicholson Oil Recirculation System is an optional version of the Nicholson Air Seal Debarker Ring. The system lets you reuse the high quality ring air seal lubricants and provides a cleaner operating environment. The system also keeps the ring lubricants from contaminating the bark. Clean and oil free bark is much easier to market and is generally environmentally desirable. The option consists of a special Air Seal Ring containing an oil recovery scoop, and a pump/filter unit. As can be seen in the diagram to the left, a Nicholson Lubrication Pump first pumps oil from the drum to the air seal ring. The oil lubricates the air seal and the ring bearing.  The used oil is then pumped through a replaceable and easy to obtain automotive type 25-micron filter. The filtered oil is returned to the supply tank or drum to be used again. Oil Recirculation can be installed on existing air seal rings.  The ring must be sent to the factory for machining.