RMP Free Fuel Trial - Filtering |
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FILTERING - Health Warning! Using waste vegetable oil in a diesel engine does work. However, waste vegetable oil may contain water, fat globules and various particulates all of which can cause harm to the engine. If you don't filter the oil carefully enough before putting it into the fuel tank, the engine fuel prefilter will clog and no more fuel will reach the engine. You may also permanently destroy the fuel distributor and the injectors.
You can filter low-tech and slow, or high-tech and quick, whichever you need. Antony needs to be able to filter his oil quickly, probably every day, preferably overnight, while he's on the road. Other waste oil users might be able to leave the oil filtering away slowly in the garage. We've investitated both methods: click here for low-tech methods, or read on for Antony's solution.
Antony is filtering his fuel, preheated to over 55 degrees C, down to 5 microns using a pressure filter constructed under "Garden Shed" principles. He heats the oil in a tea urn to 55 degrees, then prefilters it down to 10 microns through a cloth filter (see "Filter Stage 1" below), then polishes it through a 5-micron water filter under 20 p.s.i. air pressure from a small compressor (see "Filter Stage 2"). The whole process takes about 5 minutes to filter 25 litres of, after the oil has reached the right temperature.
Filtering Stage 1:
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Filtering Stage 2:
25 litres of hot oil flows freely through the 10-micron filter bag in stage 1. Antony uses a "J" cloth to screen out the bigger lumps which would clog the filter bag. Then he pours the still hot oil into the pressure vessel (an ordinary brewing bin with a car tyre valve sealed into the lid!) in stage 2. Pumping the pressure vessel to 20 p.s.i. with the small compressor (a foot pump would do as well, but slower) pushes the oil through the standard 5-micron water filter quite quickly. |
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