Fuel Polishing is actually the technical cleaning process used to remove or filter microbial contamination from oil and hydrocarbon fuel in storage. It is essentially the removal of water, sediment, and microbial contamination from such fuels as diesel, red diesel, and biodiesel.
Regular testing of fuels is required to protect equipment, and should be done on a regular basis. Discovering a problem at the onset will allow an easier process to restore the fuel than if it is allowed to progress. It also will prevent you from filling up a tank for an engine with dirty fuel, which could cause damages or losses.
Storage tanks are usually of two types: those used to fill working machinery on a regular basis, such as at a warehouse, factory, mine, or other location where the large machines do the work, or tanks storing fuel for an emergency function, such as a hospital, school, or airport, where the shutdown of power is not only scary, but could put lives in jeopardy.
Contamination of fuels can be sourced to the fuel itself at the site of origination, or it may be due to problems in the storage tank. Cloudy, murky, foul-smelling fuel is caused by water, bacteria, yeast, fungus, and contaminants. This fuel can render a working engine as scrap, and the goal of every investor who has thousands of dollars tied up in his equipment or machinery is to put good fuel into them.
Tanks filling machinery are in a constant state of emptying and filling, and the frequent fills by opening covers allows water to run in and other contaminants to be kicked in or dragged in by hoses. These risk contamination by use.
Tanks sitting stagnant and waiting for the moment of use are in danger of contamination through corrosion, condensation or lack of attention which may allow a small problem to go unnotice.