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by Rolly Angeles, Reliability Consultant
Contrary to the notion that most industries change their oil on a time dominated frequency which means that often times they replace oil based from its running hours. The question raised is, should oil really be change on a time dominated pattern or based upon its condition? Our typical belief on changing oil is that we are are led to believe that oil should be replace regularly since if oil will not be change then more parts will fail.
Let us go back with the basics, oil is made of up of 2 things it’s base which can either be petroleum based (extracted from nature) or synthetic (man-made oil) and then we have the additives. Base oil are then treated with chemicals and additives to form the different grades of lubrication to suit a wide variety of applications. Once the additives deplete, then there is no more reason to use the oil and therefore should be change.
But what cause the oil to breakdown ?
First and foremost, we have depletion of additives. Additives deplete due to contamination present in the oil. Contamination do not only come in the form of solid particles but presence of water and air are also a form of contaminant itself.
Second, is heat. Contaminants induce heat. One indicator of heat tolerance will be the oil’s Flash Point. The lower the Flash Point, the greater chance of vaporization loss. And once this happens viscosity increase and oil oxidization is imminent to happen. Oil therefore becomes acidic. This means that TAN (Total Acid Number) increase while TBN (Total Base Number) decrease.
Our belief about contamination :
Contamination is the main reason for oil degradation, hence, the need to change oil on a Time-Dominated Frequency is essential. More contamination means more failures and the need to change oil. But what is important is to analyze oil on the amount of contaminants present and not by the frequency of changing oil itself. By knowing what elements and contaminants are present in the oil, maintenance can strategize ways and means to improve fluid cleanliness and lengthen its drain interval. Remember that clean oil is not necessarily means new oil. New oil contains a lot of contamination even if the containers are sealed. The bottom line is that there is a direct relationship between the life of the oil and the amount of contaminants present in it, the more contaminants present in the oil the more chances of failure. Therefore, if oil can be maintained clean then there is no reason to change it and follow the OEM’s required change oil frequency. Here is a sample of a hydraulic oil magnified around 50x proving that new oil is not necessarily clean oil and contains a lot of contaminants in it.
Big industries studies shows a direct relationship between the amount of contaminants present & the lifespan of parts. General Motors Corporation shows that 82% of internal wear comes from abrasive particles 40 microns in size SKF Bearing states that improper lubrication account for 54% of bearing failure. Canadian National Research Council studies shows that contamination was found out to be the leading cause of wear in a variety of industries investigated. British Hydromechanics Research Association which covered a 3 year study on 117 hydraulic machines composed mainly of injection molding, machine tools, mobile, construction, marine, metals concluded a dramatic relationship between fluid contamination and its service life. Can contamination be removed in the oil ?
First, contaminants are measured in microns. One micron is about 39 millionths of an inch. Perhaps a grain of iodize salt is around 60 microns, hair follicle maybe will be in the range of around 100 microns, red blood cells is around 7 microns. An average human eye with a vision of 20/20 can only see particles in the range of 40 microns and above.
Hydraulic equipments, and engines primary defense against these contaminants will be their filtration system or what we call its oil filter. The typical function of a filter is to remove abrasive particles from the oil to achieve a desired level of fluid cleanliness. |
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This means that if we have around 100,000 particles entering the filter (upstream) and our filter rating is 50% or Beta of 2 then only 50,000 will be trapped by the filter and the remaining 50,000 will pass both through the filters upstream and downstream and goes back again to the system where there is a high probability that these particles can be trapped in between clearances that will cause abrasion to occur in our system.
Although there are many absolute filters today in the market, the intent of this newsletter is not to promote them but rather to let our readers understand how they function. Perhaps, this illustration will further prove my point :
Clearly from this comparison, we can see therefore where frequent failures can be experience. We also should take note that fluid pressure will play a critical role in the selection of the correct micron size filters. These high efficiency filters should not be used to replace the primary filter as a drop in pressure would definitely create havoc in your system. The role of these high efficiency filters is not to replace the original filters but rather to be part of a secondary filtration process most commonly known as by-pass filters.
Let’s provide a typical example of by-pass filters, every single vehicle had its own primary full-flow filter. These filters are only capable of removing particles around 30 to 40 microns in size and higher, hence it cannot remove sooth, combustion by products and contaminants 20 microns and lower. In order to remove these abrasive particles, a secondary by-pass filter should be installed separately from the original full flow filter. Although I have seen how this type of filter works, one must fully understand its usefulness before installing them to your vehicle most specially on the economic point of view as these filters cost 5 to 20x the cost of the original full flow oil filter. These by-pass filters would be feasible to corporations with a large fleet of vehicles rather than having them installed on a single car. The oil filter cartridge once is clogged is replaced instead of the oil plus a regular oil analysis check These is the secret of extended oil drain, in which logically if the oil is maintained clean then there is no reason for the additives to deplete and moreover no need to change the oil itself. Once if you understand how this works then extending oil change is possible.
Does oil really wear out ?
The base oil really do not wear out, the additives only becomes depleted. We change our oil in our car, our generators, engines, hydraulic systems because it is our assumption that the oil is not fit for use anymore, maybe we are right but maybe we are wrong technically. Only an oil analysis check can dictate if our oil needs to be change or not, and even if the oil is dirty, we have so many ways to clean it and check it again if it is still fit for use. Such ways of cleaning oil includes electrostatic cleaning, centrifuge, and filtration with fine micron rating filters. I believe that if all vehicles are equipped with secondary by-pass filters and around 6 in 10 gas stations had an independent oil analysis laboratory where ordinary consumers like you and me can check their oil, then I believe that the 3000 miles oil change can be disregarded for good. Hence, to conclude this newsletter, if contaminants can be removed from the oil then there is no reason to change the oil itself.
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Gear Pump |
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Solenoid |
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Bearing |
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Particles entering the system |
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Particles entering the system |
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10 Micron Nominal Filtration Beta 2 / Eff @ 50% |
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10 Micron Absolute Filtration Beta 200 / Eff @ 99.5% |
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Oil Filter |
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New Oil from the barrel (ISO 20/18) |
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System with built in contaminants at around ISO 20/22 |
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System with typical hydraulic Filtration at ISO 18/16 |
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System with a Beta 200 Protective Filtration ISO 13/11 |
RELIABILITY NEWSLETTER |
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Welcome to your Reliability Monthly Newsletter for the month of December 2007. You are receiving this email because at some point in time and for reasons that you opted to be included in our Newsletter mailing list from our web at www.rsareliability.com
Our newsletter will be sent out once a month and provide you with quality articles and resources on our most common link which is reliability and maintenance, as well as regular updates on our articles. I would like to personally invite you to visit our new website regularly and check out updates on our articles and training courses.
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Finally should you be interested to contribute to our articles section or share any feedback, I encourage you to email me at rollyangeles@rsareliability.com. If for any reason you wish to unsubscribe from our newsletter, kindly send my a blank email with unsubscribe as the heading and we shall remove you from our mailing lists. Once again I hope that you enjoy reading our Reliability Newsletter.
My Warm Regards,
Website : www.rsareliaiblity.com Email : rollyangeles@rsareliability.com |
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Issue No. 8 - December 2007 |
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The typical function of a filter is to clean the oil but the real purpose is to reduce maintenance operating cost by reducing abrasive and fatigue wear on its components. But we need to understand that filter can be classified as nominal or absolute in ratings and there is a big difference between these two. The Absolute Rating of a filter refers to the smallest size particle that will be removed during filtration while a Nominal Filtration Rating will refers to the average particle size that will remain in the fluid after filtration. Test have shown that it is possible for a 200 micron size filter to pass through a nominal 10 micron rating filter. To understand what this means is that every filter have their corresponding rating and efficiency. An absolute filter rating will have its lowest efficiency of 98.5% or a Beta Rating of around 75 while a Nominal Filter Rating will have a Beta Rating of 2 or an efficiency of around 50%. |
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