Engineered Maintenance by Waqas Ali Tunio


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Engineered Maintenance by Waqas Ali Tunio

Presented by me in subject of Maintenance Engineering, in my 8th semester of Mechanical Engineering of 2007-Mechanical Batch on 3rd Nov, 2010.

Department of Mechanical Engineering,
Quaid-e-Awam University of Engineering, Science & Technology, Nawabshah - Pakistan

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Engineered Maintenance by Waqas Ali Tunio

  1. 1. Engineered Maintenance<br />“Maintenance - The work of keeping something in proper condition; upkeep.”<br />By Waqas Ali Tunio (07ME34)<br />Department of Mechanical Engineering<br />Quaid-e-Awam University of Engineering, Science & Technology, Nawabshah - Pakistan<br />
  2. 2. Objectives of Maintenance Engineering<br />• Improvements in the specific asset environment (physical plant and equipment)<br />• Improvements in resource utilization (people, materials, services and Enterprise Asset Management System (EAM System)<br />• Improvements to the maintenance management processes – including the decision support and management systems.<br />
  3. 3. Introduction<br />Maintenance Engineering is the discipline and profession of applying engineering concepts to the optimization of equipment, procedures, and departmental budgets to achieve better maintainability, reliability, and availability of equipment.<br />Maintenance, and hence maintenance engineering, is increasing important due to rising amounts of equipment, systems, machineries and infrastructures. Since the Industrial Revolution devices, equipment, machinery and structures have grown increasingly complex, requiring a host of personnel, vocations and related systems needed to maintain them<br />
  4. 4. Reactive Maintenance<br />Reactive maintenance is basically the “run it till it breaks” maintenance mode. No actions or efforts are taken to maintain the equipment as the designer originally intended to ensure design life is reached. <br />
  5. 5. Preventive Maintenance<br />Actions performed on a time- or machine run-based schedule that detect, preclude, or mitigate degradation of a component or system with the aim of sustaining or extending its useful life through controlling degradation to an acceptable level.<br />
  6. 6. Corrective Maintenance<br />Equipment is maintained after break down. This maintenance is often most expensive because worn equipment can damage other parts and cause multiple damage.<br />
  7. 7. Predictive Maintenance<br />Measurements that detect the onset of system degradation (lower functional state), thereby allowing causal stressors to be eliminated or controlled prior to any significant deterioration in the component physical state. Results indicate current and future functional capability. Basically, predictive maintenance differs from preventive maintenance by basing maintenance need on the actual condition of the machine rather than on some preset schedule.<br />
  8. 8. Reliability Centered Maintenance<br />“A process used to determine the maintenance requirements of any physical asset in its operating context.”<br />It recognizes that all equipment in a facility is not of equal importance to either the process or facility safety. It recognizes that equipment design and operation differs and that different equipment will have a higher probability to undergo failures from different degradation mechanisms than others.<br />It is generally used to achieve improvements in fields such as the establishment of safe minimum levels of maintenance, changes to operating procedures and strategies and the establishment of capital maintenance regimes and plans. Successful implementation of RCM will lead to increase in cost effectiveness, machine uptime, and a greater understanding of the level of risk that the organization is presently managing.<br />
  9. 9. Maintenance Reliability<br />Most misunderstood about maintenance is the true objective of the function. The objective of maintenance is to maintain the assets of a company so that they meet the reliability needs at an optimal cost.<br />In Webster’s dictionary it defines maintenance as:<br />Maintenance<br /><ul><li>To maintain
  10. 10. Keep in existing condition
  11. 11. Preserve, protect
  12. 12. Keep from failure or decline</li></ul>The ultimate goal of maintenance is to provide optimal reliability which meets the business needs of the company.  Many people do not know the definition of reliability and it is:“The probability or duration of failure-free performance under stated conditions”<br />
  13. 13. Reliability Engineering<br />Reliability engineering is an engineering field, that deals with the study of reliability: the ability of a system or component to perform its required functions under stated conditions for a specified period of time. It is often reported as a probability.<br />
  14. 14. Design for Reliability (DfR)<br />Design For Reliability (DFR), is an emerging discipline that refers to the process of designing reliability into products. This process encompasses several tools and practices and describes the order of their deployment that an organization needs to have in place to drive reliability into their products. Typically, the first step in the DFR process is to set the system’s reliability requirements. Reliability must be "designed in" to the system.<br />Reliability design begins with the development of a model. Reliability models use block diagrams and fault trees to provide a graphical means of evaluating the relationships between different parts of the system. These models incorporate predictions based on parts-count failure rates taken from historical data. While the predictions are often not accurate in an absolute sense, they are valuable to assess relative differences in design alternatives.<br />
  15. 15. Design for Reliability (DfR)<br />Design Techniques<br />Redundancy: This means that if one part of the system fails, there is an alternate success path, such as a backup system. <br />Redundancy significantly increases system reliability, and is often the only viable means of doing so. However, redundancy is difficult and expensive, and is therefore limited to critical parts of the system.<br />Physics of failure:Relies on understanding the physical processes of stress, strength and failure at a very detailed level. Then the material or component can be re-designed to reduce the probability of failure. <br />Component derating:<br />Selecting components whose tolerance significantly exceeds the expected stress, as using a heavier gauge wire that exceeds the normal specification for the expected electrical current.<br />
  16. 16. Design for Reliability (DfR)<br />Reliability consideration has tended to be more of an after-thought in the development of many new products. Many companies' reliability activities have been performed primarily to satisfy internal procedures or customer requirements. Where reliability is actively considered in product design, it tends to be done relatively late in the development process. Some companies focus their efforts on developing reliability predictions when this effort instead could be better utilized understanding and mitigating failure modes, thereby developing improved product reliability. Organizations will go through repeated (and planned) design/build/test iterations to develop higher reliability products. Overall, this focus is reactive in nature, and the time pressures to bring a product to market limit the reliability improvements that might be made.<br />
  17. 17. Design for reliability (DfR)<br />Finally, the company should begin establishing a mechanism to accumulate and apply "lessons learned" from the past related to reliability problems as well as other producibility and maintainability issues. These lessons learned can be very useful in avoiding making the same mistakes twice.<br />Specific Design for Reliability guidelines include the following:<br /><ul><li>Design based on the expected range of the operating environment.
  18. 18. Design to minimize or balance stresses and thermal loads and/or reduce sensitivity to these stresses or loads.
  19. 19. De-rate components for added margin.
  20. 20. Provide subsystem redundancy.
  21. 21. Use proven component parts & materials with well-characterized reliability.
  22. 22. Reduce parts count & interconnections (and their failure opportunities).
  23. 23. Improve process capabilities to deliver more reliable components and assemblies.</li></li></ul><li>Maintainability<br />Maintainability is defined as the probability of performing a successful repair action within a given time. In other words, maintainability measures the ease and speed with which a system can be restored to operational status after a failure occurs.<br />
  24. 24. Design for Maintainability<br />Design is the transformation of an idea into a product, process, or service that meets both the designers requirements and end users needs. Second, maintainability is the degree to which the design can be maintained or repaired easily economically and efficiently. We can now define design for maintainability as a design strategy, involving both the designer and end user, with the following objectives:<br /><ul><li>Identify and prioritize maintenance requirements.
  25. 25. Increase product availability and decrease maintenance time.
  26. 26. Increase customer satisfaction.
  27. 27. Decrease logistics burden and Life Cycle Costs.</li></li></ul><li>Design for Maintainability<br />Consideration of product maintainability/serviceability tends to be an after-thought in the design of many products. Personnel responsible for maintenance and service need to be involved early to share their concerns and requirements. The design of the support processes needs to be developed in parallel with the design of the product. This can lead to lower overall life cycle costs and a product design that is optimized to its support processes. When designing for maintainability/serviceability, there needs to be consideration of the trade-offs involved. In high reliability and low cost products or with consumable products, designing for maintainability/serviceability is not important. In the case of a durable good with a long life cycle or a product with parts subject to wear, maintainability/serviceability may be more important than initial product acquisition cost, and the product must be designed for easy maintenance.<br />
  28. 28. Design for Maintainability<br />Basic design rules<br /><ul><li>Identify modules subject to wear or greater probability of replacement.
  29. 29. Design these modules, assemblies or parts so that they can be easily accessed, removed and replaced.
  30. 30. Use quick fastening and unfastening mechanisms for service items.
  31. 31. Use common handtools and a minimum number of handtools for disassembly and re-assembly.
  32. 32. Minimize serviceable items by placing the most likely items to fail, wear-out or need replacement in a small number of modules or assemblies. Design so that they require simple procedures to replace.
  33. 33. Use built-in self-test and indicators to quickly isolate faults and problems.
  34. 34. Eliminate or reduce the need for adjustment.
  35. 35. Use common, standard replacement parts.
  36. 36. Mistake-proof fasteners so that only the correct fastener can be used in re-assembly.
  37. 37. Mistake-proof electrical connectors by using unique connectors to avoid connectors being misconnected.</li></li></ul><li>Maintainability of Piping Systems<br />Mechanical piping systems offer a reduced need for maintenance, while providing speed and ease in accessibility and a safe environment for workers and building occupants. Allowing workers to perform maintenance procedures quickly, easily, and safely makes mechanical piping a valuable option for projects that require regular maintenance procedures or when productivity cannot be interrupted for maintenance work.<br />
  38. 38. Maintainability of Piping Systems<br />Three types of maintenance are performed on piping systems: routine periodic inspections, physical changes or expansions to a piping system, and unscheduled repairs. Routine periodic inspections are performed to ensure that a system is intact and operating at peak efficiency. Physical changes or expansions to a piping system are performed to adjust existing installations, add to an existing system, or replace old piping. Unscheduled repairs are the most pressing and time sensitive type of maintenance because they are unplanned and, in most cases, require immediate action. Causes of these repairs can include erosion; corrosion; cracks; leaks; weld failure, such as pinholes and incomplete fusion; and material failure, such as pipe defects.<br />
  39. 39. Wind Turbine Maintenance Cost<br />Modern wind turbines are designed to work for some 120 000 hours of operation throughout their design lifetime of 20 years. That is far more than an automobile engine which will generally last for some 4 000 to 6 000 hours.<br />Experience shows that maintenance cost are generally very low while the turbines are brand new, but they increase somewhat as the turbine ages.<br />
  40. 40. Lack of Maintenance Leads to Costly Repairs<br />The main component causing downtown for turbines is the gearbox, which if it fails can cost 15-20% of the price of the turbine to replace. Furthermore, failure to monitor and replace oil as needed can lead to wear on bearing and gears, causing greater financial loses than simply replacing the part.<br />
  41. 41. Boiler Maintenance<br />The purpose of maintenance is reliability and cost control. We ensure reliability of the equipment and systems in the boiler plant by limiting or preventing wear, vibration, erosion, corrosion, oxidation, and breakdown. Proper maintenance prevents failures of equipment that can result in significant repair costs. Maintenance includes many activities but the most important are monitoring and testing performed by the boiler operator.<br />There are many forms of maintenance and, contrary to many opinions, each one has its place. You choose which form of maintenance to use depending on the degree of reliability you want or can afford. Maintenance methods fall into three general categories, breakdown maintenance, preventive maintenance, and predictive maintenance. Despite what you may have heard, all three methods should be used to maintain your boiler plant. <br />
  42. 42. Boiler Maintenance<br />Between those two extremes are all sorts of variations on monitoring and maintenance but most of them relying on the skill and dedication of the boiler operator. Each round of the boiler plant you will look and listen to the feed pump, noting its condition, look for signs of vibration or shaft leakage, possibly feel the motor and pump bearing housings to get a sense of their temperature; all that is predictive maintenance. When you add oil or grease to bearings you’re performing preventive maintenance.<br />Breakdown maintenance has the advantage of low cost because we basically do nothing to prevent a failure. Preventive and predictive maintenance require an expenditure of effort and materials which represent an investment in reliability. <br />
  43. 43. Boiler Maintenance<br />Water treatment and lubrication are the two principle preventive maintenance activities in a boiler plant. Those activities prevent failures by maintaining conditions that do not allow corrosion, scale, or friction to occur. Proper operation of some systems can also be called preventive maintenance when they prevent erosion by ensuring velocities do not get too high.<br />Water treatment, properly performed, can prevent very expensive and catastrophic failure and the probability of such a failure if water treatment is avoided or ignored makes it the principle concern in all plants.<br />Predictive maintenance consists of monitoring, examinations and tests to reveal problems that will, if allowed to continue, result in failure. Annual inspections of steam boilers and less frequent inspections of other pieces of equipment are conducted to detect formation of scale, corrosion, vibration, wear, cracks, overheating and other problems that can be corrected to prevent eventual failure.<br />
  44. 44. Boiler Maintenance<br />Of course there’s that one instrument in the plant that is the best investment in predictive maintenance, the operator’s ear. An operator can detect many problems indicating imminent failure and react to prevent the failure. An operator can detect changes in sound, vibration, temperature (by simply resting a hand on the equipment) that would require a considerable investment in test and monitoring equipment. Constant attendance by a boiler plant operator is one investment in predictive maintenance that helps ensure no surprises consisting of major equipment or system failures. <br />A schedule and a record of the work being done is the best evidence that you are doing your job and a failure will not reflect on your performance. If you’ve done a good job planning and executing the maintenance plan you shouldn’t have any failures.<br />Every piece of equipment that requires preventive or predictive maintenance should have that maintenance scheduled. You have to generate the maintenance schedule for your plant because your plant is unique. The best place to start working on that schedule is the operating and maintenance manuals, doing what the manufacturer recommends until you get some track record to find what you have to add and what requirements you can extend beyond the recommendations. Be certain you got everything because failing to maintain something can be hazardous.<br />
  45. 45. Engineered Maintenance<br />To constantly improve the way maintenance gets done so that plant and equipment are more reliable, produce at better quality or higher quantity, and that costs less to maintain.<br />If your maintenance engineering function is not adding measurable financial value to your bottom line, get it to do so, or replace it with one that can, and will.<br />
  46. 46. Engineered Maintenance<br />“Maintenance - The work of keeping something in proper condition; upkeep.”<br />By Waqas Ali Tunio (07ME34)<br />Department of Mechanical Engineering<br />Quaid-e-Awam University of Engineering, Science & Technology, Nawabshah - Pakistan<br />