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Copyright © 1999 FleetWatch magazine and FleetWatch On-Line. No part of this publication may be reproduced without the prior written permission from the publishers. Views published are not necessarily those of the publishers. |
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August 1999
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Like many other 'hidden' components on a truck, the function and role of filters receives little attention with each filter being viewed in isolation rather than as part of a whole. Despite the fact that all filters - air, fuel and oil - have a symbiotic relationship in maximising engine wear reduction, there are few operators who have in place a comprehensive filtration approach to filter selection and practices. In this article, FleetWatch technical correspondent Dave Scott highlights this neglected area of trucking operations. What may work well in the truck markets of Europe, Japan and the USA is no guarantee of success on the roads of southern Africa. Every day there is a new device peddled to the local trucking fraternity - and every one brings with it the promise of being the ultimate fleet management solution. As one professional haulier wryly commented: "If I had fitted all the fuel economy devices offered to me, the cumulative total of all the percentages offered for fuel savings would mean my truck fleet could manufacture, not use, fuel!" The other problem is that devices are sold locally with tunnel vision objectives - the performance of each component is viewed in isolation rather than being seen as part of the whole. In the context of filtration, all filters - air, fuel and oil - effect the entire system. This view is endorsed in a well researched SAE Technical Paper No. 952557 titled: ‘Total FiltrationTM: The Influence of Filter Selection on Engine Wear, Emissions and Performance’ - by Marty A. Barris of Donaldson Company Inc. The conclusion of this document is that reducing engine wear will more likely be the result of a Total FiltrationTM approach to filter selection and practices than from a single filter approach. Throwing down the gauntlet This throws down the gauntlet to the individual suppliers of filters. Do they sit around a table with the end user and speak with a coordinated voice in solving engine wear problems? Or is it left to the confused transport owner to try interpret the agenda of each supplier who jockeys for most favoured position. Oh yes, don’t forget the fuel and oil suppliers whose products flow through those filters - they too are part of the equation. Our road transport operates in an environment of high sulphur diesel fuel - 0,55% of mass. While Sasol diesel is an ultra low sulphur fuel, one cannot rely on this as a constant in distribution channels and it is good practice to treat all diesel fuel as ‘high sulphur’. The sulphur forms acids that deplete the wear preventing additives in oil (see FleetWatch September 1998, SA Diesel - Fuel or Brimstone) The very best filtration cannot cope with degradation of oil quality. A further conclusion of Ian Barris’ SAE paper is that ‘lube oil change intervals impact on consumption through increased wear associated with depleted oil additive packages’. This view is reinforced locally through extensive tests carried out by the Centre for Automotive Engineering at the University of Stellenbosch. In a paper presented by Elzanne Retief at the South African Institute of Tribology seminar on Liquid Fuels, a major conclusion is that ‘fuel properties do have a considerable influence on the rate of degradation of the engine oil’. In addition, the Centre for Automotive Engineering strongly recommends that where possible, oil drain intervals should be based on total fuel consumption. If fleet owners have a system in place to monitor the fuel consumption, these records should be used to indicate the need for draining the engine oil. The length of the oil drain intervals would thus not be determined by the distance travelled but by the amount of fuel consumed by the engine. This automatically takes the vehicle’s work load into account. This is, by the way, also a specific recommendation of Cummins Engine Company Inc. But even this would not be sufficient for trucks travelling north to central Africa where they take on diesel fuel that may have even higher sulphur content levels. The service oil drain intervals would ideally differ for vehicles travelling beyond our borders where local diesel fuel specifications do not apply. Filtration aside, the problem that all South African bakkie users face is that small diesel engines suffer from severe sludging of the lubricant. The Stellenbosch University test report states that ‘a unique combination of local conditions were found to be responsible for the abnormal rate of the viscosity increase’. According to the same test, the extension of the oil drain interval is only possible if the bakkie, with a normally aspirated engine, ‘is equipped with an altitude compensation device if it is required to operate at higher altitudes’. It is obvious that over-fueling of diesel engines is causing lubrication dilution and this, in turn, is rapidly changing the lubricant characteristics and viscosity. Watch that air filter The SAE paper by Marty Barris offers two important conclusions:
The practice of removing an air filter element to blow it clean is plain stupid. This malpractice, which can lead to engine wear rates being trebled, still occurs on the false economy basis of trying to extend the service life of the air filter element. A well meaning but badly trained technician thinks he is being thorough in servicing the air filter, or replacing it prior to reaching the optimum life of the element. This happens in workshops without supervisors even being aware of it. Most modern diesel engines are fitted with air filter restriction indicators (AFRI). There is an appalling lack of knowledge on the benefits that this device holds for the operator:
- Reduced fiddling with air cleaner elements - Minimising risks of premature engine wear - Maximising the life of the air cleaner element - Containing operating costs Many truck sales people, drivers, technicians and supervisors do not comprehend the features and benefits of the AFRI and they fall into the trap of recommending premature servicing of the air cleaner. Beware the dipstick disaster! Procedural discipline and attention to using the correct air and oil filter elements falls apart when a dirty oil rag is used to check oil levels. On the one side, everything is done to ensure that the ingress of silicone into working parts is prevented. On the other side, the absence of hygiene and training of drivers and pump jockeys in correct measurement and topping up procedures can destroy an engine. Over-filling of coolants and lubricants also has inherent technical threats to the life and operation of drivelines. Few drivers and technicians are aware of this. Record the incidents The frequent replacement of fuel filters should be seen as a signal being sent. When the pressure to deliver the goods over-rides the delays that blocked fuel filters can cause, the filters are often by-passed by being removed from the system. This temporary, crisis-driven measure is overlooked and becomes a permanent feature until the next major service but by then, the damage to fuel injectors has accelerated. Low grade maintenance simply reacts to the problem by replacing blocked filters. An effective approach on the other hand, asks what is causing the fuel filters to block and how to fix the cause? Another important conclusion offered in the SAE paper by Marty Barris is that ‘high efficiency fuel filtration can reduce fuel injector wear by at least a factor of two in typical cases’. Worn fuel injectors lead to over-fueling which in turn leads to degradation of the lubricants and accelerated engine wear. Filter and expel water Fuel injection equipment is also very sensitive to water and efficient fuel filtration takes into account the separation of water out of diesel fuel. If one follows through on the concept of the Total FiltrationTM model, then a natural extension of this policy is to apply filtration to what is going into fuel storage tanks. Instead of struggling to filter contaminants out of diesel engines, start by taking control of storage facilities. In many fleets, the fuel pump is hidden in the corner of the yard where it is exposed to all the weather elements. In this environment, the fuel gun collects dust and water - two prime enemies in the fight against engine wear. In this kind of environment, storage tanks are most likely to be contaminated. There are more than 1 600 fungi that grow in fuel tanks and some of this contamination cannot be filtered out, to the detriment of driveline working parts. Air brake systems First prize for any truck air brake system has got to be an air drier. This filter device not only extracts moisture - the enemy of air brake valves - but also other debris such as oil and particles. If you protect the air brake valves and stop the system from leaking, this will result in less engine idling time, less lubrication dilution and longer lubricant life. An air brake compressor also has a finite life and continuous engine idling to supply leaking brakes overloads the compressor duty cycle. It seems that the Marty Barris’ Total FiltrationTM solution has endless possibilities. Service intervals - how long? Any service interval set for a truck must be the outcome of the Total FiltrationTM model. This appears to have been recognised by Mercedes-Benz in the new Atego model launched in July. While Mercedes-Benz announced that the Atego now comes with an extended service interval of 22 500 kilometres for long distance haulage, this hardly compares with intervals of 45 000 which is the benchmark for transport users in Germany. The unique operational conditions of southern Africa make it impossible to achieve the service intervals offered in the German market. A service interval of 22 500 kilometres is meaningless for a concrete mixer operation where much of the time the vehicle is not on the road but powering the mixer on a building site. Fuel consumption, or engine hours, are the only yardsticks for establishing service intervals in this type of operation. Gizmos & Lilly the Pink’s muti The subject of lubrication, engine wear, fuel consumption and filtration have attracted legions of inventive minds, con artists, peddlers and consultants since the first fossil fuel powered vehicles rolled into the 21st Century. I am even adding to my income by writing this article. The problem with truck manufacturers, fuel and lubricant refiners, filter manufacturers, environmentalists and legislators, is that they never sit round a common table in the planning phase. The agenda of the original equipment manufacturer (OEM) is perceived to drive the system - all the suppliers of components and lubricants used by trucks complain of the pressure placed on them as a result of the design concepts placed on them by the truck OEM. One sure thing is that not one truck OEM approves of the addition of friction modifiers to driveline lubrication systems. This is bad news for the vast number of muti doctors out there - all they can do is rely on the aftermarket and play on the ignorance and expectations of users. The other problem is that users generally do not approach the servicing of trucks on an integrated basis taking into account the interaction of all fuels, oils and filtration systems in the specific operating environment. And this is what makes them vulnerable to the supplier of one item that promises to take away the problem. Alternative Articles |
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