By Adam Pearce, Product Manager, Parker Hannifin
When it comes to the effective and reliable filtration of diesel for HGVs, there are a number of challenges to negotiate. This has been true since the first diesel engine, persisting through to modern-day common rail injection systems featuring ultra-small injection orifice diameters and uber-high pressures. In short, the common objective for filtration technology in every generation of diesel engine has been to improve system cleanliness and, in turn, boost engine reliability and reduce emissions.
Emissions have today become one of the primary drivers of diesel engine development, and thus fuel filtration. Although emissions regulations vary around the world, since the late 1990s there have been dramatic cuts to the allowable quantities of NOx (nitrogen oxides) and PM (particulate matter) that can exit the exhaust. For instance, Euro VI only permits 0.4 g/kWh of NOx and 0.01 g/kWh of PM for heavy-duty diesel engines found in the truck and bus market. These limits have had a notable bearing on engine development, leading ultimately to the latest high-pressure (>2,500 bar) fuel injection systems.
A further vital element in the successful development of effective filtration technology is fuel quality. Knowing the exact composition of common fuels is essential in designing the appropriate filters. With this thought in mind, Parker Racor leverages data from a global fuel survey that features over 900 fuel samples taken from 100 countries. The analysis concentrates on solids contamination, water, bio-content, inorganic content and cold characteristics.
With today’s fuel injection systems offering clearances of typically less than 3 µm, it is easy to envisage the potential damage that contaminants can cause, which is why fuel cleanliness demands continue to escalate. The single 8-10 µm diesel fuel filters of yesteryear would simply not be suitable for the truck and bus market in 2019. Any contamination that is allowed to permeate downstream can promote wear mechanisms such as abrasive flow wear, where particles rub against walls as sections narrow and flow accelerates, and abrasive contact wear, which begins when particles get trapped between moving components.
Water is the enemy
Overnight temperature changes with nearly empty fuel tanks are another common issue, as this scenario causes water to condense. Many cite water as an engine’s worst enemy as it displaces the lubrication properties of diesel, which in turn damages injection components. In addition, iron oxide (rust) is a primary contributor to injector wear, while the development of algae or ‘diesel bug’ can block the fuel system and filter, compromising engine life.
Water and other impurities can have a severe impact on engine efficiency, as well as service and maintenance requirements. Uncontrolled fuel impurities increase fuel and service costs, cause damage to expensive engine components and reduce the useful life of vehicles such as trucks, buses and construction machinery.
As a result of the industry’s drive towards sustainability, cleanliness and efficiency, today’s fuels are ever more complex, containing significantly increased levels of additives. In particular, bio-diesel fuels made from vegetable oil, tallow and waste animal oils/fats present problems for effective water separation due to low interfacial tension (IT) and these fuel’s ability to blend with water.
To avoid costly engine and fuel system component damage in the latest high-pressure common rail systems, advanced multi-stage filtration is recommended.
Among recent developments in this area is Racor’s new coalescing filtration media, which represents a technological step change in diesel fuel filtration. Unlike conventional barrier water separators, which separate water from fuel with a single hydrophobic barrier filter element, Aquabloc3D elements use three distinct stages to ensure only clean fuel passes to the engine.
Aquabloc3D has been designed as an upgrade and replacement for existing water separator spin-on filters used in Parker’s industry-leading products found on a wide range of HGVs. The technology stems from Parker’s extensive experience in the field of multi-stage coalescer elements found in many airports, refineries, marine applications and power generation.
Parker Racor’s Aquabloc3D coalescing filtration systems are purpose-designed to enable operators to meet the challenges of dealing with increasingly sophisticated fuel. Moreover, they offer longer service life and considerably improved water separation in bio-diesel fuels.
As fuel technology continues to develop, vehicle operators must ensure that their filtration solutions keep pace.
For more information: Parker Hannifin