SubscribeThe latest generation of fuel line filtration technology is enabling truck and bus manufacturers to improve the performance and operating life of injection systems, while also reducing costs significantly over the lifetime of the vehicle, explains Adam Pearce of Parker Hannifin’s Racor Division.
As diesel engines continue to offer increasingly high levels of performance, their susceptibility to fuel contamination is also increasing considerably. With the high pressures typical of modern engines, contamination can create serious problems ranging from decreased efficiency to complete injector failure. Truck and bus manufacturers are now more aware of these problems than ever before, and many are now seeing the economic benefit of fitting their engines with pre-filtration systems in order to prevent contamination.
The most common contaminants are moisture and particulates, which together can be lethal for injection systems. Moisture ingress most commonly occurs inside storage tanks or vehicle tanks, with condensation on the walls of the tank mixing with the fuel, while particulate contamination can been picked up by the fuel at various points in the supply chain, even before the fuel is put into the vehicle's tank.
As well as causing the corrosion of injector nozzles and pumps, water contamination can also provide an ideal breeding ground for micro-organisms that grow in the fuel when the water has settled, resulting in contamination. Any water present in the fuel system will also inevitability have an impact on the properties of the fuel as a lubricant, which is vital for the smooth running of components such as injectors and pumps inside a diesel engine.
Particulate contamination can be picked up as dirt during transport, storage, from a vehicle's own tank or, as already mentioned, contributed to by water-borne micro-organisms and corrosion particles. Whatever the cause, it can spell disaster in a modern diesel engine. For example, with the extremely small tolerances in the design of injectors, particles as small as 5-10μm can lodge between valve faces, preventing them from closing properly and leading to leaks, reduced combustion efficiency and potentially injector failure.
In addition, modern advanced fuel injection systems can operate with fuel pressures as high as 2100 bar making the results of water and particulate contamination even more extreme. By the time the engine's performance shows signs of deterioration, the damage has often already been done, leaving only the option of replacing expensive injectors and high-pressure pumps. Almost all engine manufacturers have an OEM final particulate filter fitted to their engines, but the quality of this kind of filtration is arguably no better than that to be found at the refinery or the filling station. For this reason, many vehicle manufacturers are now striving to obtain a higher quality of filtration and water separation through the installation of in-line pre filter water separating fuel filters.
Parker Hannifin's Racor division is one company that manufactures fuel filters that combine the functions of a particle filter and water separator in one system. This technology is capable of offering filtration grades as low as 2μm. Products such as the latest 400 Series Spin-On filter/separators also incorporate many features that help them adapt both to the changing requirements of diesel engines and the variability in fuel quality. Some models are able to offer even finer level of filtration by warming the fuel before it is filtered. This can increase final fuel cleanliness by more than ten times in some circumstances, helping to extend vehicle service life significantly.
This method is particularly beneficial where biofuels are used. These alternative fuels are becoming increasingly popular in the light of government directives to reduce harmful emissions; one EC Directive, adopted in 2003, requires Member States to ensure that biofuels and other renewables amount to at least 5.75% of all transport fuels by the end of 2010, with an EU Green Book target of 20% by 2020. Likewise, the revised EN590 specification states that levels of sulphur in diesel will have to be reduced to 10ppm by 2009.
Biofuels are renewable, carbon-neutral, environmentally friendly fuels derived from biomass. Biodiesel, which can be used in diesel engines, originates from oils or fats, including virgin oil feedstock, waste vegetable oil, and animal fats, and can be used neat as 100% biodiesel (known as B100) in specially adapted engines, or blended with conventional diesel. Currently, the most common biodiesel blend is B20, a mixture of 20% biodiesel and 80% diesel.
Although biofuels offer significant environmental advantages over conventional fossil fuels, their use also raises a number of problems for designers and manufacturers of engines and components. One such problem is the way in which fuel filters used in diesel engines running on biofuels can quickly become clogged with wax crystals that form in the fuel if its temperature drops in cold conditions. Biodiesel can have a lowering effect on the cold filter plugging point (CFPP), the temperature at which a fuel causes a fuel filter to plug due to crystallisation, presenting problems for vehicles that are operated in colder climates, or even for those parked outside overnight. As wax crystals begin to form they can clog fuel lines and filters, potentially resulting in a break-down.
To overcome these problems, products such as the Parker 400 Series HH filter have been developed. This model can operate effectively at temperatures ranging from -40ºC to 80ºC on biodiesels, while the innovative filter head incorporates a positive temperature coefficient (PTC) heater that warms the fuel before filtering it. This feature, combined with the fine levels of filtration that the HH unit achieves, can increase the cleanliness of the fuel flowing through to the injectors and engine by a factor of 100 in some cases. The filter is equipped with a 10µm rated filter element, a high capacity see-through water collection bowl and a built-in primer pump, allowing it to cope with the typical levels of contamination that can be expected in a biodiesel.
More and more truck and bus manufacturers are now realising that the cost of adding a fuel line filter to a vehicle is easily outweighed by the cost of replacing an entire injection system that has been damaged by contaminated fuel. By taking a pro-active approach to fuel contamination, manufacturers are now able to help their customers significantly reduce long term operating costs.
