Contamination Monitoring for Maximum Uptime

By: Drew Troyer

Improving profitability in an increasingly competitive manufacturing environment is a difficult challenge faced by most managers. Most manufacturers exist in a price-taker's market. In such a market, the only feasible way to improve profitability is to reduce operating costs, effectively reducing the per unit cost of production. Reducing the costs to maintain plant equipment still represents a bountiful opportunity for improvement and cost reduction. Aggressive managers are recognizing that aggressive maintenance management utilizing a PROACTIVE approach is paying significant dividends. The practice of reacting to breakdowns of critical production equipment is no longer an option for the firm that wishes to continue healthy and profitable operation. Diagnetics, Inc. is dedicated to providing its clients and customers with the most advanced PROACTIVE technologies, software and service solutions for achieving long term cost reduction and profit maximization.

Ensuring production uptime is the prime directive of the maintenance organization. In the past, this has been accomplished by building in redundancies and excess production capacity, or by following an aggressive schedule to rebuild or overhaul critical systems. Both approaches are inherently inefficient. Redundant systems and excess capacity tie up scarce capital that could otherwise be deployed in a producing activity.

Scheduled overhauls and rebuilds of critical systems and components offer managers peace of mind at a very high cost. Intuitively, it seems that rebuilding a machine on a schedule is the best way to avoid the costly effects of a breakdown. However, when one reviews this practice in more depth, it does have its risks. Most machines follow a probability of failure pattern called the bathtub curve. The bathtub curve simply displays a machines probability of failure over time. It has three distinct regions, the premature failure region, the random failure region and the wear out failure region. New and rebuilt systems enter their lives in the premature failure region. The probability of failure during this period is high because of all the variables associated with manufacturing, machining, assembling and installing a new or rebuilt system. Once past this critical period, the system enters a period during which failures are random and the probability of failure is statistically equal over time. At some point, all mechanical systems enter a wear out period during which the probability of failure increases. If a machine is rebuilt on a schedule, it is removed from the random failure region where the probability of failure is at its lowest, to the premature failure period where the probability of failure is at its highest. The bottom line is that scheduling the rebuild of a machine which follows the pattern of the traditional bathtub curve actually increases the overall probability of a failure! This is a very expensive activity which decreases the reliability of mechanical systems. Scheduled rebuilds and overhauls of critical equipment is in conflict with the objective of extending the average time between, and shortening the average length of, scheduled production down periods for which most organization today strive.

Condition-Based Maintenance

Advanced maintenance organizations, recognizing the high cost of scheduled rebuilds, have begun to utilize non-destructive testing techniques to identify failures very early so appropriate repairs can be scheduled only when the machine indicates that it is time for such an action. This approach to maintenance is called predictive maintenance. Predictive maintenance offers numerous advantages over a run-to-failure, or breakdown, approach to maintenance. And because maintenance activities are scheduled in real time, according to machine conditions and requirements, condition-based maintenance is far superior to traditional scheduled maintenance. Costly unplanned downtime is avoided and catastrophic chain reaction failures can be eliminated. With condition-based maintenance, overall reliability is improved while the total cost of maintenance is reduced. Some of the technologies applied in these predictive include vibration monitoring and analysis, wear debris analysis and thermographic analysis.

The limitation of predictive condition-based maintenance lies in the fact that it is failure oriented. Yes, it is more effective than traditional approaches, but it leaves on the table a considerable opportunity to improve reliability and uptime while reducing costs. These benefits are available only through PROACTIVE MAINTENANCE. Few machines merely fail for no reason. The majority of failures have one or more underlying root causes. Some of the root causes of mechanical machine failure include:

Faulty design. Faulty installation. Misalignment/imbalance. Excessive load. Excessive heat. Abrasive particle contamination in the lubricant. Moisture contamination in the lubricant.

The most common root cause of machine wear and failure is lubricant contamination by particles and moisture. Most failures which are attributed to "normal wear" are caused by lubricant contamination. The Canadian Research Council found that 82% of all wear across a variety of key industries was particle induced! Abrasive particles such as dirt, dust and debris slowly rub away critical machine surfaces until clearances are breached and the machine fails or must be shut down for repair. Moisture contamination degrades lubricant quality and results in a loss of the separation of machine surfaces normally afforded by a healthy, dry lubricant. Together, particle and moisture control represent the greatest opportunity to management for achieving quantum improvements in maintenance cost reduction. Controlling contamination and other root causes of machine wear and failure is the objective of PROACTIVE MAINTENANCE.

The Human Body Parallel To Machine Maintenance

The human body represents an excellent parallel to mechanical machinery to better understand the opportunity which lies in PROACTIVE maintenance. A breakdown, or run-to-failure approach to maintenance is analogous to a heart attack or stroke. Waiting until this dire indication of trouble in a human body or a machine results in the need to perform a quick diagnosis and act immediately. There is scarcely enough time to carefully acquire and analyze condition information and make a thorough diagnosis of the situation. This leads to prescribed actions which have a higher than normal probability of failure. It is a situation which all physicians and maintenance mangers prefer to avoid.

Maintenance Strategy Technique Needed Human Body Parallel Proactive  Maintenance Monitoring and correction of failing root causes, e.g., contamination Cholesterol and blood pressure monitoring with diet control Predictive Maintenance Monitoring of vibration, heat, alignment, wear debris Detection of heart disease using EKG or ultrasonics Preventive Maintenance Periodic component replacement By-pass or transplant surgery Breakdown Maintenance Large maintenance budget Heart attack or stroke

In reviewing the human body parallel to machine maintenance, the inefficiency of a scheduled preventive maintenance program becomes clear. No physician would suggest that critical body components be replaced or rebuilt just because a certain age is reached. It seems equally illogical to prescribe an overhaul or rebuild of a mechanical system based solely on a schedule, without the assistance of machine condition data.

Most surgical activities, such as heart surgery, are scheduled when non-destructive testing information, such as an EKG, suggests that a problem is present. This information allows the physician to acquire corroborating test information and diagnosis, and to schedule and plan surgical activities under non-emergency circumstances, greatly enhancing the probability of a successful outcome. This is exactly the objective of predictive maintenance. By gathering machine condition information, an effective diagnosis can be made, and activities scheduled logically and with sufficient time to plan.

Most physicians today recommend a PROACTIVE approach to human body maintenance. It is widely published that cholesterol and high blood pressure are precursors to heart failure and other human ailments. While the presence of either, or both, does not in itself represent heart disease, they represent the underlying root causes of heart failure, strokes, etc. By making an investment in controlling these root causes today, an individual can reduce his risk of a failure later. Physicians recommend regular checks to quantify the presence of these contaminants which are harmful to the human body. When acceptable levels are exceeded, prescriptive actions are taken to remedy the root cause condition, not the component itself. This is PROACTIVE health care. Machines can be maintained in the very same way. By regularly monitoring particle and moisture contamination (cholesterol to a mechanical system), corrective action can be take to remedy the presence of the contamination, eliminating the risk to machine reliability which they represent.

Proactive Fluid Contamination Control

Intuitively, it makes sense that lubricants which are free from contamination will provide better service to the machine. And in turn, properly lubricated machines will provide better, more reliable and profitable service to the owner or operator. Why then don't more maintenance programs have aggressive contamination control programs? Largely, it is due to a lack of understanding of contamination and its control. Additionally, being PROACTIVE requires a long term investment in machines and people. Pouring a thimbleful of dirt into a system today may not lead to any instant halt of operation today, or even this year. But, invariably, the machine's life has been shortened. When the machine does finally fail, it is difficult to know that additional life would have been available had the dirt not been added. It is perhaps even more difficult to trace the loss of life to the dirt in the thimble.

Controlling fluid contamination requires a clear plan of action and a substantial amount of diligence. The steps to PROACTIVE contamination control are:

Set machine specific target levels for all systems. Achieve cleanliness targets with contamination exclusion and removal. Monitor contamination levels regularly to assure conformance to standard.

Target cleanliness levels should be set in accordance to the machines inherent sensitivity to contamination, the various costs of failure, the severity of the application and the environment in which the machine operates. Typical OEM suggestions may be insufficient to meet your specific needs and productivity goals. Careful analysis of each situation should go into the establishment of target levels.

Once target levels are set, activities should focus on achieving the targets. Contamination control goes way beyond installing expensive filters. In fact, it cost ten times as much to remove a particle once it is in the machine's fluid as it does to keep it out in the first place. Contamination control begins when fluid reaches the receiving dock. New fluid, while typically very healthy, is not necessarily clean. In fact, it rarely is clean enough to be put in service immediately. The logistic process of transporting lubricants from the refiner to the mixing house, and finally to your door imposes a risk for contamination ingestion. Standards and procedures must be put in place to manage new oil as it arrives. Additionally, how the fluid is stored in bulk and the manner in which machines are filled or topped-off will have a great impact on total contamination levels in your machines. Next, tank vents and breathers should be inspected and upgraded if necessary. Often, minor design modifications can have a huge impact on contamination control. Seals changes, shields, boots and other methods for keeping contamination away from, and out of the, system should reviewed. New and rebuilt machines and components carry large quantities of built-in contamination, standards of cleanliness must be set and enforced. There are hundreds of small changes which can have a dramatic impact on contamination control. Each should be reviewed and implemented if feasible.

Contamination removal is the responsibility of filters and filtration systems. Once contamination exclusion options have been exhausted, filters and the filtration system design should be reviewed next. Upgrades should be implemented to reach the target cleanliness level. This may not mean using the best or most expensive filter. It may simply mean that a moderate filter used in the correct manner will provide the desired results. Even systems which have not historically been filtered, such as critical gearboxes, can be effectively filtered while the machine is running with a little bit of creative know-how.

Contamination  Monitoring: The Critical Feedback Loop

Once cleanliness targets are achieved, they most be monitored regularly to assure that the targets are maintained. This is the heart and soul of PROACTIVE MAINTENANCE. In order to implement contamination control, contamination levels must be checked at several critical points, including:

New oil arriving from the supplier. Bulk tank or stored lubricants. Oil as it enters the systems during change-outs or top-offs. Flushing or packing oil from new components. Oil which is in service in the machine.

Just as a physician does not assume that cholesterol levels are static in the human body, maintenance managers must implement aggressive contamination monitoring to assure control of contamination in machines.

Effective contamination control requires standards, procedures and measurements. Standards must be written in a "cradle to grave" fashion. Because new oil is scarcely ever clean enough to enter the system, standard requirements must be established and communicated to the oil supplier. If the standards are extremely rigorous, expect to pay a premium to the supplier for removing particles and moisture upon delivery. Then, establish procedures to check for conformance. This requires particle counting and moisture detecting devices on-site. If requirements are not met, document the findings, report them to the supplier and reject the shipment. If one supplier can't, or won't, meet the requirements set forth, another one most assuredly will.

Once in the plant, the management of the new fluid becomes the responsibility of the user. Standards for bulk stored lubricants must be established. In most cases, changes in the way they are stored or the environment in which they are stored must be changed. In some cases, filtration systems for polishing stored lubricants will be required. These changes should take the form of operating procedures to be followed by all. Again, monitoring of the contamination levels is necessary to insure process control.

Oil being transported from bulk storage to the machine in which they will be placed into service represents the greatest risk for contamination ingestion. Often, open oil pails are scattered about the facility for operators to top off systems. These procedures must be tightly controlled. Cleanliness standards for lubricants going into a system during change-outs or when topping off a system must be established for each machine or class of machines. Procedures must be established for achieving the cleanliness targets. In most cases, filtration transfer carts should be used when adding oil to a system. These procedures must be specific and detailed, down to the way in which the reservoir cap is removed. Again, without appropriate particle and moisture detection instruments, process control cannot be assured.

Conventional wisdom suggests that new oil is clean oil. This is rarely the case. New oil is a significant source of contamination. Contamination enters new oil from a variety of sources. Lubricants begin their lives at a refinery. The fluids leaving the refinery are not filtered and may carry contaminants. Next, they go to the mixing house, the lubricant supplier, and eventually, they arrive at the customers receiving dock. Their are numerous opportunities along the logistic chain where particles and moisture can enter the system. It is important to establish standards of cleanliness and to communicate those standards to your oil supplier. If the standards are rigorous, the supplier may charge a service fee for meeting the requirement. Regardless of the rigor set forth in the requirements, fluids must be tested for levels of particle and moisture contamination at the receiving dock. This is the only way to assure the quality of the new lubricants.

When repairs and component change outs are required, special care is required to assure that the new seals, bearings, pumps, hoses and other components are free from contamination. Procedures for cleaning and testing components prior to installation, and controlling the manner in which they are installed can significantly reduce early life wear and failure. Again, measurement instruments provide the vital information to assure that procedures are effective.

During operation, all mechanical systems are dynamic. Particles and moisture are ingested at alarming rates. If detected, the root causes of ingestion such as faulty seals and breathers can be corrected before wear and component degradation occurs. Much like a physician recommending exercise and diet control to correct a condition of high cholesterol, maintenance technicians can correct contamination ingestion, avoiding the otherwise inevitable wear which leads to machine failure. Again, contamination monitoring is the feedback loop. It is analogous to the routine cholesterol check performed by the physician. Additionally, when ingestion is controlled, particle count provides an extremely early warning when wear is being caused by abnormal mechanical stress, lubricant degradation, or any other root cause of machine wear.

Predictive Aspects of Contamination Monitoring

Invariably, all machines wear and eventually fail, even when all reasonable efforts are made to be PROACTIVE and control root causes. In these situations, contamination monitoring, especially particle counting is an invaluable part of a predictive maintenance program. Especially, when the capability to differentiate ferrous wear from non-ferrous debris is added to the equation.

Wear debris, regardless of the wearing process, results in an increase in particle count. Once discovered, the diagnostician can use the on-site particle counter so critical to proactive maintenance for on the spot troubleshooting. With a wear debris separator attached to the particle counter, the diagnostician can determine immediately if the reason for the increased particle count is wear generation or dirt ingestion. If the debris is wear, the diagnostician moves to the next level of analysis. By sampling from different points in the system, the source of the wear debris can usually be pinpointed. Additionally, by testing at close time intervals, a rate of change analysis can be made to determine the severity of the situation. Common sense takes over from there. For instance, by comparing the rate of change of ferrous versus non-ferrous particle counts for a journal bearing on a compressor which is shelling out material, the diagnostician can estimate the severity of the problem. For instance, if the bearing is bronze and the ferrous particle count is high, and escalating rapidly, the diagnostician would conclude that serious damage to the shaft is occurring. Operations can then be presented with a decision to shut down the compressor or to continue operation. The suggestion to shut down would be fact based and logical. Supporting those difficult decisions is, after all a primary purpose for machine condition monitoring. In a very short time, the diagnostician has identified a problem, localized the problem, estimated residual life and or damage being incurred, and reported to management the findings, all because contamination monitoring equipment was on-site and available.

Moisture contamination monitoring, while not offering the robust predictive power of particle contamination monitoring, is very effective in identifying heat exchanger leaks, a common failure of lubricated systems.

Education: The Critical Link To Success

Education is critical to successful implementation of a contamination control program. Managers, technicians and operators must all be educated as to their roles in the process. Top managers must understand the long term benefits of controlling this important root cause of machine failure and degradation and the short term, predictive and decision support benefits of contamination monitoring funds can be allocated to implement the program. Sufficient data to support a thoughtful and thorough proposal to management is readily available. And, after all, the thought that lubricants which are clean and dry will provide better service is intuitively obvious.

Technical people must be thoroughly informed as to the intricacies of setting up a contamination control program. Standards for cleanliness, procedures for implementation, and other details must be attended to. Those involved must be well prepared for the task with a thorough education in the basics of lubrication, contamination control, contamination monitoring, sampling procedures, oil and wear debris analysis and many other fundamentals. Also, they are typically responsible for the important aspects of establishing and managing a data management system.

Operators, mechanics, and others responsible for implementing the program must have knowledge as to the effects of contamination on the lubricant and the system, where it comes from, how it is controlled and how they impact the equation with their day to day actions.

Conclusion

The benefits of an aggressive program to control contamination can pay significant dividends. The sacrifice is one of diligence. It is not easy to implement a meticulous lubricant cleanliness program. Standards and procedures must be written and an investment which will pay off in the future requires a long term outlook on one's business. But increasing machine reliability and reducing maintenance costs by orders of magnitude is the pay-off which awaits those that buckle down and get the job done.

This story reprinted courtesy of Diagnetics.

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