Anders Pettersson divides his time between being a senior lecturer at Luleå University of Technology and working with R&D issues at Volvo CE in Eskilstuna
His focus area is machine elements and tribology, and he emphasizes the importance of knowing what you are doing when handling oils.
– There is always a risk when you are inside and tampering with a hydraulic system; a great deal can go wrong and lead to devastating consequences. The system’s performance can definitely deteriorate after an oil change if you do not know what you are doing, he states. Having a well-developed maintenance process therefore becomes central.
– The key is to avoid the human factor as far as possible, to have well-developed routines and training for all employees so that everyone knows what should be done and when. You need to be very careful and make sure that the oil entering the system is completely clean. If you have sensitive systems, you need to fill the oil through a filter, because contaminants may remain in the oil drum even if it has been cleaned before being filled with clean oil. In mobile hydraulics, there were major problems in the 1980s and 1990s with leakage in connection with hose changes in the field. Insufficient training and incorrect routines caused the oil to become contaminated.
– That is an example of how training and clear routines can take you very far. Today, those problems have decreased significantly thanks to the fact that everyone who works with such tasks has received proper education and training in changing hoses in the field. Anders Pettersson further explains that many today use condition-based maintenance, which places somewhat different demands on the maintenance process.
– In order to take advantage of such maintenance, you must be completely clear about which criteria determine when an oil change is needed. You need to understand your own system; you cannot use pre-set values. Every system has its own conditions and requires different oil cleanliness levels in order to function optimally. Therefore, the settings for condition-based maintenance must be adapted to each individual hydraulic system.
Different reasons why oil stops working
In his teaching, Anders Pettersson explains how different contaminants affect oil and cause it to no longer fulfill the function it is expected to perform. This includes everything from shear degradation to dirt entering from the outside. The main reasons why oil stops functioning as it should are:
• Shear degradation, which makes the oil too thin to retain its protective effect. What happens is that the viscosity index improvers, which are long-chain polymers, become overloaded so that they break and permanently lose their thickening ability.
• Oxidation
o Oxidation causes an increase in viscosity, which in turn can result in poorer low-temperature properties, for example.
o During oxidation, the oil can become aggressive toward components.
o The breakdown products formed during oxidation can create sludge or deposits on components.
• Different types of contamination
o Dirt entering from the outside gives the oil poorer performance.
o Wear-generated particles mean that the oil no longer protects the components as it should but instead causes abrasion.
o Fuel, coolant or other foreign liquids can enter the oil and impair its properties.
• Loss of functional properties
o Oil initially contains additives with anti-wear properties. If the oil is subjected to varying loads, local overloading can occur, which breaks down such additives. This in turn results in a loss of anti-wear properties and leads to increased wear on components.
o In the event of mechanical or chemical overloading, the oil can lose its friction properties, which worsens its performance. (Compare ATF in an automatic transmission: it starts to jerk or slip during shifting when the friction modifiers have worn out.)
Can prevent downtime
Since every hydraulic system is unique, because the conditions for each system are unique, it is important to gain a good understanding of your own hydraulic system in order to build the right maintenance process.
– Once you have operated your system for a while, you get a good sense of what that particular system’s weak link, or links, are and what you need to monitor more closely. Which they are depends on the parameters governing operation, such as temperature, load levels, the atmosphere around the system, and much more. If you have a good understanding of the system, you can build routines that prevent potential downtime and ensure that the oil always performs optimally under the given conditions.
– If you understand the system, you can read it and quickly notice deviations and take action in time to prevent acute downtime.
Standard oils are much better today
There has been a great deal of development on the oil side over recent decades. Anders Pettersson notes that standard oils / conventional oils have improved significantly compared with 15–20 years ago.
– Truly high-quality and expensive oils have existed for a long time, for example in the aerospace industry; the major development has taken place in standard oils. Today they have improved significantly, with better oxidation stability, shear stability and wear protection than before, among other things. At the same time, he notes that the use of ester-based oils that appeared on the market a number of years ago has not increased as quickly as many may previously have believed.
New legal requirements will affect environmental classifications
Development is also taking place in areas other than the oils themselves. Environmental and climate requirements are becoming more numerous and more extensive, and there is an ongoing discussion within the EU about which requirements should apply. Something that will affect everyone using oils in their systems going forward is the legislative work taking place specifically regarding oils.
– There is a tightening of legislation within the EU that will mean that certain oils which currently achieve environmental classifications will no longer be approved in the future for environmental reasons. This applies to both ester-based and fossil-based oils. This will affect many, but we do not yet know exactly how the new legal requirements will be designed. We will have to return to that during the autumn, he concludes.
