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Issue No. 49 - May 2011 |
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Since establishing this website last May of 2007, I have made many efforts to improve this site and provide some useful insights about our common link which is all about improving our equipment reliability and the way we do maintenance.
Finally should you be interested to contribute to our articles section or share any feedback, I encourage you to email me Click here to email me. 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 welcome to our May 2011 edition of our Monthly Reliability Newsletter and I hope that you enjoy reading and sharing with your people.
My Warm Regards,
Website : www.rsareliaiblity.com Inspired by Change . . . |
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RELIABILITY & MAINTENANCE CONSULTANCY FIRM
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Where the learning just never stops . . .
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RSA
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For our complete archive of previous reliability newsletter |
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You are receiving this newsletter and email because at some point in time you opted to be included in our Monthly Reliability Newsletter mailing list from our site.
Our newsletter will be sent out ones a month and provide you with quality issues and resources on our most common link which is all about reliability and maintenance, as well as regular updates about our site. I would like to personally invite you to regularly visit our website and check out updates on our articles and training courses. |
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Maintenance is not about shifting from a Preventive to a Predictive Maintenance nor transitioning from a Reactive to a Proactive Maintenance stage but simply understanding when to used these strategies simultaneously depending on the consequences of failure and this is done with the aid of a maintenance algorithm or decision diagram . . . . |
RELIABILITY NEWSLETTER |
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RSA |
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Inspired by change |
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• Gallery: New pictures for 2011 added from the gallery portion. • Newsletter: Aug. 2011 Edition finally released to our subscribers. Email me if you want to subscribe to our Newsletter. • 2012 Training Schedule: If you are interested to attend in any of our public workshop and master class for 2012. Send us an email or register online. • WCM Book: If you’re interested in buying the book on World Class Maintenance, The 12 Disciplines. Send me an email to reserve. WCM Book is now available. Get your copy now. • In-house Training :Should your industry be interested for in-house trainings we are now accepting regular schedules for in-house training for both local and international countries on courses that we currently offered. Contact us |
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World Class Maintenance Management - The Twelve Disciplines Book is now available here. This is not only about the technical jargon on reliability and maintenance, it is a book that makes every single maintenance proud that they belong to the maintenance function. If you have been living through the day to day pressures of doing maintenance then this is your story. If you are interested in this book, send me an email. Click Here ! |
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Select the courses of your choice and it can be made available in CD . Click Here ! |
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We are very much flattered and humbled by your feedback and testimonies. Your messages are the main reason for allowing us to stay in this business. With all humility we say thank you and rest assure that we are continuously improving. Without your support in our training there won’t be us. Read More ! |
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• Registration at this forum is done through administration only. Should you be interested to join send me an email and we will provide you with a user ID and password. Visit my discussion board and forum . .
• Share what you know. Come and join our RSA Maintenance Forum. Send me an email |
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• If your industry is interested to join and participate in any of our upcoming public training and workshop for this year 2012 you may send us an email or simply fill out the registration form provided on our schedule site. You may Click here to visit our schedule training for 2012 Schedule. |
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Our Reliability Newsletter will be provided once a month to our valued subscribers. It provides highlights as well as issues and lessons regarding our most common link which is all about improving the reliability of equipment. |
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REACTIVE MAINTENANCE
• A strategy which tells us that when a machine fails then it is time for maintenance to fix it. Maintenance is done at a point when there is repair or actual breakdown. It occurs when repair action is taken on a problem only when the problem results in machine failure. Reactive maintenance results in unplanned downtime. In its simplest definition, reactive maintenance simply means fixing it when it fails. Limitations of this strategy maintenance is that this cause unplanned downtime and production delays which results in revenue losses and extending the maintenance to work overtime to fix the equipment. Repairing the equipment after it fails usually creates the possibility of secondary damage which increase the maintenance costs. Allowing failures to occur can be applied to the asset if and only if the consequences of failure and the cost of repair is minimal and acceptable to both the user and maintenance
• Other terms used to denote Reactive Maintenance includes: run-to fail, run-to destruction, band-aid maintenance, firefighting maintenance, unplanned breakdown, power plants often called this corrective maintenance (note: TPM practitioners refers to corrective maintenance as performing improvement on the equipment), breakdown maintenance, Mc-Guyver maintenance, RCM often called this as no-scheduled maintenance. I think that’s all I can think of. |
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PREDICTIVE MAINTENANCE
• Condition-Based Maintenance or Predictive Maintenance checks the condition of an equipment through the use of sophisticated measuring non-destructive instruments with precision accuracy. Predictive Maintenance instruments are just a higher form of the human senses. These instruments simply allow us to determine the problem much more than our senses can either hear or see them. It allows us to make decisions once a potential failure is visible. Predictive Maintenance aids us in determining the potential failure or symptoms that an equipment is in the process of failing. Changes in the condition of the equipment can denote a potential failure. Specialized diagnostic instruments can aid in detecting these potential failure on the equipment such as increase in heat or temperature, increase in vibration, for electrical we have changes in resistance, changes in conductivity, increase in noise, change in pressure and flow rate, lubrication contamination, wall thickness decrement, rate of corrosion, leak detection, crack detection and so on.
• Since our goal in maintenance is to keep our physical assets in an existing state, prediction is a declaration in advance that something is going to happen and from the dictionary Predictive Maintenance is a proclamation or declaration in advance based on observation to preserve something from failure or sustain it against danger. Predictive Maintenance is a maintenance activity geared in indicating where a piece of equipment is on the critical wear curve and predicting its useful life.
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• If the failure is evident and does not affect safety nor the environment or if it is hidden but does not affect safety or environment then default decision is to allow it to fail. Duplicating the system or component failures are allowed or being tolerated through some form of redundant or when the asset has some form of duplicated functions. The presence of standby or redundancy which is an alternative means of production is a feature of the operating context which must be considered in detail when defining the functions of the asset in its present operating context. Often times termed as standby-unit and even with the same type of equipment, standby units can have different degree of maintenance requirement as the duty unit and most failures for standby unit are considered to be hidden in the first place. Therefore, when the consequences of failure will be limited to the direct cost of repair with minimum chances of secondary damages to the equipment, then the default task will be to allow the failure to occur. |
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If we place a bearing under reactive maintenance, there will be no replacement on the bearing to be done, maintenance will just wait for the bearing to seize. When this happens then the bearing will be replaced, production halts, downtime occurs and maintenance perform repair and replacement on the bearing. The strategy for maintenance will be to keep stock of the bearing on the stockroom to make sure that repair time will be on a minimum. The problem with this approach is that there is a possibility of having some secondary damage on the equipment or other parts may be affected, downtime can be excessive, cost of spare and maintenance are caught by surprise on the failure of the bearing |
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PREVENTIVE MAINTENANCE
• Preventive Maintenance is a basic maintenance performed on the equipment and facilities. The main goal of performing task on a scheduled basis is to extend the equipment life and to assure its capacity in support of plant’s goals and targets. In Preventive Maintenance, the basic law to consider is that the cost of performing PM must always have to be lower than the cost of not doing it which eventually will result to a failure.
• PM is also a series of tasks performed at a defined frequency dictated by the passage of time, the amount of machine hours or mileage that either extend the life of the asset or detect that an asset had a critical wear and is about to fail or break in operation. PM also called time-based maintenance are founded on the belief that given a history of failures of a given component failing after a certain number of hours used or other measurements but most parts based on this approach are usually based on averages. The problem with Preventive Maintenance is that this approach may carry out maintenance work at regular intervals and since most tasks are based on the average maintenance may carry out a work that is not required and the probability of replacing parts which are still in working condition. Since this is a time-based maintenance, studies have shown that most of equipment failures are not directly related to the number of hours or operating age of the part.
• Preventive Maintenance activities includes equipment inspection and checks, scheduled parts replacement, overhauls, routine cleaning, lubrication, planning and scheduling, preparing work orders, managing spares inventory, CMMS and so on. In addition, workers can record equipment deterioration so they know to replace or repair worn parts before it cause system failure. Applicability of Preventive Maintenance tasks are technically feasible if first, there is an identifiable age at which the item shows a rapid increase in the conditional probability of failure which means that the part have a useful life and most of these items survive to that age and they restore the original resistance to failure of the item. |
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Hence when we place a bearing under Preventive Maintenance it is assumed that 95% of bearings will reach its desired life and probability of failure is high. If this is the case then it is a good decision to place the bearing on a Time-Dominated Frequency or Preventive Maintenance. But in reality, or perhaps based from previous failure history record on bearings, record shows that majority of bearings fails every 2 yrs or 24 months, therefore, maintenance decided to replace the bearing when it reached the 23rd month of continuous use placing it on Time-Based. The problem with this approach is that in reality especially in a reactive world we experience a lot of premature and unexpected failures encountered before the PM schedule is due and maintenance is not guaranteed that even if the bearing reached its 23rd month if it is still fit for use or really needs to be replaced. |
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• CBM tasks entails checking for potential failures, so that action can be taken to prevent a functional failure or to avoid the consequences of a functional failure. Predictive Maintenance aids in detecting potential failures in equipment with the aid of specialized instruments. Maintenance is based on the condition of the equipment which differentiate it from Preventive Maintenance. There are many failure modes that give some sort of warning that they are on the process of occurring hence, the P-F curve shows how a failure starts, deteriorates to a point where it can be detected (Point “P”), and if it is not detected deteriorates at an accelerating rate. |
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If we place a bearing under Predictive Maintenance, an ailing bearing will produce signs and symptoms or potential failure, that it is in the process of failing, therefore, maintenance department will try to use CBM / PdM Techniques such as Oil Analysis and Vibration Analysis to detect a potential failure from the bearing such as increase in vibration or contaminants. Although this is a good strategy, the problem with this approach is that since imminent failures can be predicted, production can be notified but still we need to replace the bearings and the life of the bearing might not be actually been reached. Although it is good enough that both operations and maintenance are not caught by surprise on the failure |
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PROACTIVE MAINTENANCE
• Proactive Maintenance is about analyzing why failures occur so that its recurrence can be finally eliminated, and thereby extending the life of the part or component. Proactive Maintenance is when maintenance or a group of cross-functional team analyzes the failure with problem solving tools and analytical techniques such as Root Cause Failure Analysis, FMEA, Ishikawa diagram, P-M Analysis, Fault-Tree Analysis and so on which are used to better understand why the failure occurred in the first place. In Preventive Maintenance we replace the part that we think is in the process of wearing out because our thinking is that replacing the part will bring the equipment back to its original condition, we have not taken into account the need to analyze further why a certain part keeps on failing.
• Proactive Maintenance is used in order to reduce the probability of failure mode occurring to a level which is acceptable example replacing component with stronger or more reliable replacement making the failure no longer a threat to safety and to the environment.
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If we place this bearing under Proactive Maintenance a group of cross-functional people will study and analyze the failure on the bearing and ones they determine the cause of the problem they will provide a permanent solution not only to prevent its recurrence but also to increase the life of the bearing. Hence, if we place the bearing under Proactive Maintenance, after the analysis on the bearing the team found that the cause of premature failures was due to severe oil contamination. After adopting oil analysis and application of absolute filtration, finally the bearing life improved. Studies made by different tribologist indicates that there is a direct relationship between the life of a bearing and the number of contaminants present in the oil. After the improvement not only did the bearing reached its life but it tripled its life as well |
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• Every failure has a specific set of consequences, being PROACTIVE has something to do about reducing or eliminating the consequences of failure to a minimum rather that completely eliminating the failure itself. The best maintenance strategy to adopt will always have to be based upon the consequences of the failure itself. The first thing to ask in the event of a failure will be what is the consequences of the failure if it occurs on its own and will the failure be acceptable to the user or not. |
