Compared to engines for passenger cars, engines for commercial vehicles - in particular those equipped with heavily loaded diesel engines - differ both in terms of operating conditions and design.
Commercial vehicle engines typically operate under heavy loads and at higher temperatures than passenger car engines. From the point of view of wear of internal engine components, single particles with a diameter of 8 to 60 µm floating in the oil are of great importance, but small particles with a diameter of less than 1 µm are also important, especially when their concentration is high.
The construction and specificity of operation of these engines causes that a large amount of soot is generated in the process of fuel and oil combustion, e.g. as a result of exhaust gas recirculation. Soot increases the viscosity of the oil and reduces its lubricating properties. Soot particles are very small and their diameter is 100 times smaller than the diameter of a human hair. Also deposits and sludge as well as acidic pollutant compounds resulting from the combustion of fuel with a high content of sulfur are harmful to the engine. Particularly harmful is the low-temperature sludge formed in the winter, which clogs the pores of the oil filter. That is why commercial vehicles are equipped with an additional barrier for the finest particles - the so-called oil bypass filter. It is installed before the full flow oil filter.
In the place where the oil pressure is the highest, a small stream is branched off, through which 5-10% of the oil volume flows. This filter has a very fine filtration medium to filter out soot particles with a diameter of less than 1 µm (the size of soot particles is measured in nanometers, however, soot clumps are formed that can be separated mechanically). The bypass filter in commercial vehicles separates around 500 g of soot and fine particles between oil changes. In this way, particles are removed that, due to their small size, would get into the full-flow oil filter. If not, it would increase engine wear.
Mercedes Actros II Filter Module OM541/542Picture: Hengst Automotive
Another method used, among others, in Mercedes Actros, DAF, Deutz vehicles is the so-called centrifugal separators, popularly known as "centrifuges". Instead of a bypass filter, a free-flow centrifugal separator is installed, it is made of metal or plastic. This impeller is driven by engine oil pressure and rotates at 11,000 rpm. rpm and Hengst's patented helical blades inside the centrifuge ensure that the engine oil rotates at the same circumferential speed as the impeller. This creates a centrifugal force 2,000 times greater than the force of gravity, and metallic dirt particles such as soot and particles sucked in from the air are deposited on the inner walls of the impeller. In this way, the engine oil stays clean for longer and, due to the lower soot content, the oil change intervals can be extended.
Full-flow filters and "centrifuges" are integrated in the filtration module, which also houses the oil cooler, temperature and pressure sensor, solenoid valve and fuel filter. The precursor and creator of filtration modules is Hengst, a leading supplier of integrated filtration modules for the automotive industry. Filter modules are designed and cast from aluminum alloys at the Hengst factory in Nordwalde (North Westphalia, Germany).
Today's constructions are dominated by two-stage systems. That is, the full-flow filtration system is combined with a side-flow filter or a centrifugal separator, this solution gives the best effect. A long-life full-flow filter traps larger contaminants, while a bypass filter slowly and thoroughly filters the oil from the finest contaminants. 5-10% of the oil volume flows through this filter, because the rest is needed to supply the lubrication system. On the other hand, the advantage of centrifugal filters is that they achieve a good degree of separation of the smallest particles and that a very compact mass of these particles is formed on the inner walls, and it is easy to replace such a rotor with a new one.
Filter module DAF MX-11 engines. (Euro 6, 10, 8L.). DAF XF, CF, Kennworth models. Picture: Hengst Automotive
Is the oil filter technology keeping up with the technology of the oil itself? Do the oil filters withstand the high mileage specified by the high mileage oil manufacturers?
Depending on the engine design, we create appropriate filter media with varying degrees of pollutant absorption and service life. ACEA E4, E6, E7 and E9 quality oils, which are designed for extended mileage, have a package of additives that are intended to extend the life of the oil, but it must be said here that they are more aggressive compared to semi-synthetic oils and work on filter medium. Therefore, filter manufacturers have developed a suitable filter medium resistant to aggressive hydrosynthetic oils. In this case, it is recommended to use a medium with an extended life, i.e. a synthetic medium or a composite medium that retains particles with a size of 4 μm and separates particles with a diameter of 10 μm 20 times better. This results in cleaner oil in the lubrication system and better protection of engine components. Compared to the standard filter medium, the composite medium shows good chemical resistance and is distinguished by excellent separation efficiency and ability to absorb contaminants, which is important in the requirements for engine oil purity and extended drain intervals. The selection of appropriate layers determines the properties of the filter medium.
In a word, only a properly selected filter according to manufacturer's specifications guarantees smooth operation and filtering of the oil throughout its long service life. By using Hengst filters, you are guaranteed that there is a suitable filter medium inside, resistant to aging, high temperature and bursting (a measure of mechanical strength).
Therefore, a well-chosen oil and a good filter guarantee the achievement of extended mileage. A properly constructed filter with a synthetic filter medium, collecting impurities throughout the entire period of use, from replacement to replacement, guarantees engine cleanliness and extends its life.
