Recycled oil by post
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EQUIPMENT for recycling engine oil has been designed by the Midlands Postal Board's mechanisation and development division, which maintains some 4,500 vehicles.
In trying to reduce lube oil costs, three principal objectives were identified : 111 The reduction of lubricating oil consumption by, means of a recycling process; E Ensuring by some positive means that sump levels could be more easily maintained by drivers; II Eliminating the need for oil filters as engine equipment, and thus saving material and labour costs.
The Postal Board's solution has been to design its own equipment which can be operated by the drivers to extract the used oil, filter it for recycling and refill the sump to the prescribed level with the reclaimed oil. A prototype is on field trials at the Worcester Head Post Office.
The principle of operation is to extract the used oil by a pressure differential created by a partial vacuum. The oil is then forced under pressure from a compressed air source through a series of moisture and micro-solid particle filters to be discharged as filtered oil into the main body of replenishment oil held in the reservoir.
The level of oil in the reservoir is kept constant by daily additions of new oil— the volume added representing that used by vehicle operations over one day. A proportion of new protective additives is thus added each day to compensate in part for the chemical deterioration. Therefore, claims the Post Office, the rate of additive loss and chemical deterioration of the main body of oil held in the reservoir is sufficiently retarded to .permit the oil to be continually recycled until a chemical analysis indicates that the whole of the reservoir oil should be changed.
The increased frequency of oil changes and the high efficiency of the filters used in the equipment—the solid particle filter is rated down to two microns—has made it possible to dispense with oil filters as engine equipment and thereby to eliminate the costs of filter element replacement and the associated labour costs. Operation of the equipment The dispensing equipment consists of a standard compressed air-operated pump which forces the oil via a recording meter into the sump. Initially, the reservoir is filled with new oil to a defined level.
The line valves are closed and a hose line is connected to the engine sump via a snapon valve fixed to the vehicle. When the valve (4) is opened, the system is pressurised from the compressed air source. Opening valve (5) allows the pressurised air to flow through the venturi which is in connection with the air space in the used oil receiving vessel.
The increase in kinetic energy of the air column in the venturi results in a drop in pressure energy which creates a partial vacuum in the vessel and results in a pressure differential arising between the vessel and the engine sump. The excess of atmospheric pressure acting on the surface of the sump oil over the pres sure in the used oil vessel causes the used oil to be transferred.
When all the oil has been extracted from the sump, there is no longer an hermetic seal to the used oil vessel and the partial vacuum is thus destroyed. Closing valve (5) causes the air space in the used oil vessel to be pressurised. This pressure acts on the surface of the used oil to force it through the various filters and to discharge into the main body of oil.
When valve (6) is opened, fresh oil under pressure is passed via the recording meter into the engine sump.
The time taken for a complete oil change for a vehicle with a one gallon sump is approximately Iwo minutes.