Fuel polishing is the process of removing water and particulates from fuel to ensure that the fuel quality remains in-line with fuel specifications. Ideally, fuel should have an ISO particle code of 18/16/13 and a dissolved water content no greater than 200 parts per million. There should be no free or emulsified water present.

How often should fuel be polished?

If you have standing fuel, and if no ‘on tank’ fuel polishing system is fitted, then it’s recommended that fuel should be polished every 6 months. When doing so, where fuel is being drawn from and returned to the same tank, the entire volume of the fuel should be run through the polishing system 4 or 5 times to ensure that all contamination is removed. If transferring fuel to another holding tank, one pass through the polishing system is sufficient.

Will fuel polishing remove all fuel tank contamination?

Fuel polishing will remove free and emulsified water as well as solid particles (size dependent upon the filter element being used). If there is microbial contamination in the tank any free floating biomass will be removed. However, if the tank is badly contaminated and a biofilm has formed – a biofilm is a colony of microbes that have adhered to the tank surfaces – fuel polishing may be only partially effective. In such instances tank cleaning will be required.

Are fuel polishing systems suitable for tank cleaning?

Generally no. Fuel polishing is designed to maintain the quality of fuel by removing free floating contaminants and emulsified and free water. As mentioned above, fuel tanks can become contaminated by biofilms which cannot be removed by fuel polishing alone. Where a light biofilm is established this can be killed with the application of fuel biocide, where a heavy biofilm is established or there is a heavy layer of sludge in the tank bottom, tank cleaning using abrasive techniques or jetting could be required. Where a biocide is used, ALWAYS cycle the fuel through a fuel polishing system as the biocide will have killed the contamination and could have dislodged chunks of biomass which could block on engine filters.