The centrifuge consists of a body with outer casing cover and a central spindle around which a rotor spins at high speed. It can be designed onto an engine as original equipment or retro-fitted to an existing engine.

 

The following is a schematic representation of the engine’s lubricating oil system. The by-pass oil cleaning device cleans a small proportion of oil being pumped to the engine and returns it to the sump.

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Oil at pump pressure enters the centrifuge body and continues to the cleaning chamber of the rotor via the centre spindle. Having passed through the cleaning chamber, the oil exits at the base of the rotor via two tangetially opposed nozzles. The oil exiting from the nozzles causes the rotor to spin at high speed. Dependent upon size a rotor may spin up to 10,000 rev/min. The resultant centrifugal force causes particles of contaminant to migrate outwards where they form a dense “cake” on the inner wall of the rotor. The compacted dirt may be removed simply with a spatula thus minimising waste disposal and maintenance labour costs. The centrifuge collects the tiny sub-micron particles present in the engine’s oil and isolates them to give greater protection than normal by-pass filters. In addition, unlike conventional by-pass filters, the centrifuge does not become blocked and therefore provides sustainable protection for the engine.

 

The following figure shows the change in engine oil pressure measured after the full flow filters at the maximum torque condition. During the tests the standard engine experienced an oil pressure loss of 28%, the engine fitted with the paper bypass filter experienced an 8% pressure loss and the engine fitted with the centrifuge experienced no pressure loss. The pressure loss is attributable to component wear mainly in the main and big end bearings and oil pump.

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The centrifuge is actually a separator and not a filter since it is mechanically driven. It has a number of advantages compared to media filter types. Contaminants are condensed into a dense “cake” and for a given size they have a much greater contaminant capacity than the media types. This leads to a major benefit in their relative rate of deterioration. Flow through centrifugal oil cleaners does not vary with ageing and whilst efficiency changes due to an effective reduction in bowl radius as contamination builds up, this normally only effects sub-micron particles. Centrifuges are not limited by pore size, and remove particles smaller than 0.1μm. Moreover centrifuges preferentially remove denser contaminants including the more abrasive materials, especially chrome and iron. The centrifuge has been also used to clean fluids other than engine lube oil (e.g hydraulic oils) with viscosity above 5cSt.

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