Published on March 10, 2014
Fluid Contaminant Control as an Essential Technique to Implement Proactive Maintenance for Bearing Elements Umar Sidik* PT. Filtagreen Global, Indonesia *email@example.com Abstract Maintenance brings a work to ensure bearing element runs as its function. A good maintenance management system is able to prevent health and safety problems, result in low cost, and high quality of life. On the other hand, proactive maintenance is not like predictive/preventive maintenance due to proactive maintenance is aimed for failure root cause, not just symptoms. According to the bearing division of TRW that contamination is the number one cause of bearing damage that leads premature removal. Furthermore, the amount of damage caused by solid contaminant passing between the rolling and sliding surface of an anti-friction bearing is proportional to the size and concentration of contaminants. Therefore, this is important to do particle counting on lube oil samples. Fluid contaminant level must be frequently monitored to verify filter performance and to provide the essential “feedback” that gives integrity to a contamination control program. Keywords : Fluid contaminant control, proactive maintenance, failure root cause, particle counting, filter, bearing element 1. Introduction Commonly, operation and maintenance are an integrated process that covers the performance of work to deliver a proper function of bearing element. Maintenance brings a work to ensure the bearing element runs as its function. The maintenance scheme forms a maintenance management that covers planning, organizing, monitoring, and evaluating 1|PT. Filtagreen Global., 2014. White Paper
maintenance activities and their costs. Therefore, a good maintenance management system is able to prevent health and safety problems, result in lower cost, and higher quality of life. On the other hand, the symptom of failure in the bearing element masks the root cause of failure. For example, a sudden bearing failure is often blamed on poor quality lubricant. In the fact, the root cause is often contamination in lubricant (bad filter) of bearing (Figure 1). According to the bearing division of TRW that contamination is the number one cause of bearing damage that leads premature removal. Furthermore, Machine Design Magazine reports that less than 10 percent of all rolling-element bearings reach the fatigue limit because contamination usually causes wear earlier. Therefore, fluid contamination level must be frequently monitored to verify filter performance and to provide the essential “feedback” that gives integrity to a contamination control program. Figure 1. Contamination in lubricant (Harker., 2001) 2. 2.1 Basic theory Maintenance scheme Commonly, there are three categories in the maintenance such as corrective, preventive, and predictive maintenances. Corrective maintenance is intentionally withheld until bearing element stops working or starts falling, where maintenance is then performed as necessitated such as lubricate bearing when they become noisy or vibration occurs. In the corrective maintenance, a conscious decision is made to neglect bearing element falls. This maintenance strategy is referred to as “Run to Failure” (RFT). Whereas, preventive maintenance is a planned maintenance such as cleaning of machine, fuel, and oil. On the other hand, predictive 2|PT. Filtagreen Global., 2014. White Paper
maintenance is condition based maintenance such as indicator of oil pressure (lubricant stop). In the preventive maintenance, the bearing element is subjected to a regular of maintenance tasks such as inspections, cleaning, lubrication, and adjustment. The frequency of preventive maintenance is generally constant and is usually based on the expected life of the component being maintained. The preventive maintenance is carried out at predefined intervals in attempt to reduce bearing element failure or to ensure a consistent appearance of bearing element. As the bearing element age, the frequency and number of checkpoints may need to be re-evaluated. On the other hand, the predictive maintenance (also known as condition monitoring) delivers additional benefit over preventive maintenance. The main benefit of predictive maintenance is the availability of earlier warning reduces the number of breakdown catastrophic failure. Predictive maintenance is usually implemented concurrently with preventive maintenance. Furthermore, the proactive maintenance is the most important to achieve the predictable cost and better performance. The approach of proactive maintenance replaces the maintenance philosophy of “failure reactive” to be “failure proactive”. Proactive maintenance is not like predictive/preventive maintenance due to proactive maintenance is aimed at failure root cause, not just symptoms. 2.2 Contamination Physically, wear occurs as a result of contamination due to dust, metallic particle, or condensation. Contaminant is inevitable in any non-sealed lubrication system. High contamination level is linear to the level of wear which cause a premature failure. Therefore, the increase of wear metal causes the abrasive process to be irreversible. The exorbitant wear metal level should have been detected after catastrophic failure. There are many types of contaminant-induced failures in machinery and the most common are wear, erosion, and corrosion. Contaminant involved includes solid particle, moisture, air, chemicals, and other materials foreign to the system (Figure 2). However, 3|PT. Filtagreen Global., 2014. White Paper
abrasive wear caused by solid particle is the result of particles (too small to be seen) that cut plow and sliding surfaces. Figure 2. Contamination in lubrication system (TESTOIL., 2012) Furthermore, contaminant is clearly the most common and serious failure culprit. According to Caterpillar that dirt and contamination are far the number one causes of hydraulic system failures. The amount of damage caused by solid contaminant passing between the rolling and sliding surface of an anti-friction bearing is proportional to the size and concentration of the contaminants. Therefore, J. I. Case states that the bearing element must be kept clean (spotlessly clean) in order to achieve the productivity they are capable of. Whereas, Oklahoma State University reports that when fluid maintained 10 times cleaner then hydraulic life can be extended by 50 times. 3. 3.1 Implementation Maintenance strategy In the fact, most machinery is fluid dependent system. Whereas, there are many types of contaminant-induced failures in machinery such as wear, erosion, and corrosion. Fluid (such as lubricant, hydraulic fluid, coolant, fuel, and air) brings contaminants into the bearing element and transports the contaminant within the bearing element. The most serious of contaminant is abrasive wear caused by solid particles. The abrasive wear is the result of particles (too small to be seen) that cut and plow rolling and sliding surfaces. 4|PT. Filtagreen Global., 2014. White Paper
Physically, high contamination is a correctable condition. The abnormal presence of contamination is a system can be described as an incipient failure, where the machine is not currently experiencing loss of performance or component degradation (the condition that leads to failure and shortened service life are present and untenable). On the other hand, the U.S. Department of Defense states that approximately 30 percent of all engine failure is caused by metal particulate contamination in lubricating oil system. The oil film thickness, between which particles can reach and attack surface are typically in the 10-micron range. Whereas, according to Cummins Engine, particles smaller than 10 microns generated about 3.5 times more wear (rods, rings, and main bearings) than 10 microns. In addition, in diesel engine, high local stresses associated with sliding contact wear in abrasive removal of material surface. When load is concentrated on the effective area of a small particle, the resulting surface stresses can be greater than 500,000 psi, far beyond the elastic limit of substrate materials. Therefore, filter with high efficiency is specified for engine lube oils (Figure 3). The lube oil contamination is the primary cause of engine wear that begins what is referred to as the chain reaction to failure. Figure 3. Filter for engine lube oils with high efficiency (TESTOIL., 2012) There are some considerations filter such as temperature change, fluid viscosity, pressure, flow (surge), vibration, and fatigue. Therefore, fluid contamination level must be frequently monitored to verify filter performance and to provide the essential “feedback” that gives integrity to a contamination control program. On the other hand, the challenge task is to remove particle from fluid at the same rate which they are entering (ingression). Other common problems such as filter bypass valves that get stuck open, damaged or missing filter 5|PT. Filtagreen Global., 2014. White Paper
gaskets, and filter which installed backward or crooked. The logical first-approach to proactive maintenance is the implementation of rigorous contamination control programs for lubrication fluid, hydraulic fluid, coolant, air, and fuel. Simplify, this is important to do particle counting on lube oil samples. Furthermore, wear metal analysis and elemental analysis are too often confused as being indicative of actual particle sizes and concentrations in lube oils. Therefore, only accurate particle counting devices can determine this. 3.2 System monitoring The fundamental purpose for contamination control and contamination monitoring is to achieve greatly extended mean time between failures (MTBF). Furthermore, there are three baselines in the system monitoring, such as: 1. Routine contaminant monitoring to deliver the major system monitoring requirements 2. Set the contaminant level scale to represent the abnormal condition for further analysis 3. Description of the contamination source 3.3 Steps to implement proactive contamination control maintenance Furthermore, there are four steps to implement proactive maintenance, such as: 1. Using the Contamination Life Index to assist the target fluid cleanliness level 2. Select and install filtration system to achieve the target cleanliness level 3. Monitor fluid cleanliness at regular intervals to verify that target is achieved 4. Adjust filtration to stabilize the target cleanliness 6|PT. Filtagreen Global., 2014. White Paper
4. Result and discussion This paper appears that the contaminant level is extremely dynamic. Whereas, fluid contaminant monitoring can be accomplish in the field or plant by extracting samples of fluid into bottles for lab analysis or by portable instruments used at the machine. Recently, there has been a trend away from bottle sampling and lab analysis for routine contaminant monitoring due to costly, reduced accuracy, and time delay. The use of portable monitors that receive fluid directly delivers on-the-spot analysis. For example, the digital Contam-Alert (dCA) from Diagnestic is a portable instrument for routine contamination monitoring. This instrument allows a small sample of fluid to flow into the sensor for particle counting. The result of particle counting will be sent to computer through satellite connection (Figure 4). Figure 4. Contamination monitoring using portable instrument through satellite connection (Murakami et al., 2002) Furthermore, the unit can be used with a variety of different fluids such as lube oils, hydraulic fluids, and coolants. After each test, the handle on the sensor is depressed to expel the sample which making it immediately ready for reuse. Finally, the result of particle counting can be easily stored in the computer, print out with a portable printer, and downloaded into a personal computer. 7|PT. Filtagreen Global., 2014. White Paper
5. Conclusion Proactive maintenance is presented as an important mean to cure failure root causes and extend machine life. In the implementation, contaminant monitoring is being a key to achieve proactive maintenance through its contamination control. Therefore, fluid contaminant control is established as an essential technique to implement proactive maintenance. On the other hand, the use of real time or portable instrument for contaminant monitoring has been effective to recognize the symptoms of impeding machine failure. Expert system software combined with strategically located sensor and transducer to provide a comprehensive contaminant monitoring for sophisticated machines and applications. Furthermore, outside of its usefulness as a proactive maintenance tool, contaminant monitoring can be equally effective as a first-alert to impending machine failure. Therefore, the use of portable contaminant monitor provides easy in-the-plant or in-the-field proactive maintenance for bearing elements. Bibliography [a] Chichester, Chad., “Lubrication beyond Oil and Grease: How Anti-Seize Pastes and Anti-Friction Coatings Reduce Wear, Optimize Friction and Perform Under Extreme Environmental Conditions”, Dow Corning Corporation, 2012 [b] Fitch, J. C., “Proactive Maintenance Can Yield More Than a 10-Fold Savings Over Conventional Predictive/Preventive Maintenance Programs”, [c] Technical Information Document., “Maintenance Management System”, RPS for INAC , TID-AM-01, October 2000 [d] Information Bulletin., “What is Maintenance”, Vol. 5 [e] Murakami, Taku., Saigo, Takaichi., Ohkura, Yasunori., Okawa, Yukio., Taninaga, Tadashi., “Development of Vehicle Health Monitoring System (VHMS/WebCARE) for Large-Sized Construction Machine”, KOMATSU, Technical Report, 2002 [f] TEST OIL., “Filter Debris Analysis Report”, 2012 [g] Harker, D. E., “Lubrication of Clarifier Drives, Why Oil is Preferred over Grease”, Walker Process Equipment, Division of McNish Corporation, 2001 8|PT. Filtagreen Global., 2014. White Paper
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