Diesel Fuel Cleanliness Guidelines
The overall cleanliness of diesel fuel, or lack thereof, coupled with poor storage and housekeeping practices is the next big problem that all industries in
particular transport and power generation will have to deal with. With increasing additions of bio-diesel this also creates additional hazards and responsibilities for storage and
housekeeping. The fuel cleanliness issues start at the refinery. There the fuel output filtration is typically between 50 and 80 micron. Particles smaller than this are unfiltered
and remain in the fuel. The contamination continues when the fuel is taken from the refinery as it may go through several more transfers before reaching the final tank, boats, tankers,
or barrels. These can all contribute to dirt and water ingress.
Much of the problem is related to micron filtration size and water accumulation in diesel fuel as it reaches pumps and injectors. Problems are likely to hit the
mobile industry first, as the diesel engine business is the first to deal with EPA's low exhaust emission regulations and with it, the families of new or redesigned engines and
especially pump and injection systems. Ten years ago, maximum diesel fuel system pressures rarely exceeded 3000 psi, however with today's advanced systems this can be as high as 30,000 psi and
therein lies the problem. Most engine fuel filters are nominal 15 or 10 micron and the most damaging particle size by volume is 5-10 microns.
Lab work revealed that particles in the 5 to 10 micron sizes were the most abrasive size group and were the cause of shortened component life. It turned out the
7 micron particle was the perfect fit between micro-machined clearances and would actually grind away on metal surfaces, causing accelerated wear resulting in a drop in pump pressures
and causing servo valve orifice erosion.
Water ingress to storage tanks is a major problem, particularly for companies who have to store large amounts of fuel for standby, back-up generator systems. Water
causes condensation through temperature changes and particularly with older storage tanks contributes to rust that forms within the void between the level of fuel and the tank. This rust
falls away and causes sediment within the fuel.
Other sources of water ingress are through poorly maintained manhole access points, these can fill with water and seepage can occur through filler caps, breather points
and tank lids and faulty seals.
Faulty tanks, cracked pipe work can all contribute to contamination problems within storage tanks.