IN THIS PRESENTATION 1.MAINTENANCE 2.OBJECTIVE 3.GOAL 4.CHALLENGE TO INDUSTRY 5.MAITENANCE STRATEGY 6.REACTIVE MAINTENANCE--FAILURE BASED 7.PREVENTIVE MAINTENANCE- INTERVAL BASED 8.PREDICTIVE MAINTENANCE –CONDITION BASED 9.PROACTIVE MAINTENANCE 10.RELIABILITY CENTRED MAINTENANCE. 11.MAINTENANCE TECHNIQUES 12.PRINCIPLES OF MAINTAINABILITY DESIGN
1.MAINTENANCE Past & current maintenance practices in industry would imply that maintenance is action associated with equipment repair after it is broken. The dictionary defines maintenance as follows: “the work of keeping something in proper condition; upkeep.” This would imply that maintenance should be actions taken to prevent a device or component from failing or to repair normal equipment degradation experienced with the operation of the device to keep it in proper working order.
2.OBJECTIVE To Reduce unplanned downtime To Extend machinery life To Minimize Equipment damage/repairs TO reduce Overtime To Reduce repair cost To Reduce parts inventory requirements To Improve reliability
3.GOAL To preserve the functions of physical assets throughout their technologically useful lives To the satisfaction of their owners, of their users, and of society as a whole . By selecting and applying the most cost- effective techniques For managing failures and their consequences With the active support of all the people involved.
4.CHALLENGE TO INDUSTRY Industries, are being pressured by competition, the economy, regulatory branches, and other forces to reduce operating and maintenance costs without decreasing reliability or availability. Plant Maintenance is generally ecognized as the single largest controllable cost. As a result, many Industries are being encouraged to downsize their employee and budget levels. This environment presents a challenge that is management to reevaluate their maintenance strategies.
6.REACTIVE MAINTENANCE--FAILURE BASED In the earlier part of this century most maintenance resources were used to react to equipment breakdowns that had caused major operational losses. From this practice the terms “reactive”, “breakdown”, “corrective”, and “run-to-failure” maintenance descriptions were coined for naming the principal maintenance technique that formed the maintenance strategy.
REACTIVE MAINTENANCE Reactive Maintenance can be either good or bad. When applying this maintenance technique, maintenance, equipment repair, or replacement occurs only when the deterioration in the condition of the equipment causes a functional failure. This type of maintenance assumes that failure is equally likely to occur in any part, component, or system and failure is age-related.
REACTIVE MAINTENANCE This type of maintenance assumes that failure is equally likely to occur in any part, component, or system and failure is age-related. Examples of components where Reactive Maintenance is applicable are non-critical electric motors less than 7.5 HP, comfort cooling, restroom exhaust fans, small, low temperature water heaters, and items where the consequences of failure are negligible.
REACTIVE MAINTENANCE Advantages Lower initial cost, Requires fewer staff Disadvantages Increased cost due to unplanned downtime of equipment. Increased labor costs especially for untimely repairs and replacements. May result in secondary equipment or process damage. May increased costs associated with repairs and replacements Is an inefficient use of staff resources.
7.PREVENTIVE MAINTENANCE--INTERVAL BASED Preventive maintenance (PM) uses regularly scheduled inspections, tests, services, repairs, replacements, and other tasks to reduce the frequency and impact of equipment failures. These maintenance activities are performed on a calendar or operating time interval basis to extend the life of equipment and prevent premature failure.
PREVENTIVE MAINTENANCE Preventive maintenance is one of the first major breakthroughs that resulted in a significant reduction in maintenance costs, while simultaneously resulting in an increase in reliability and availability. One of its benefits is the identification of the early stages of equipment deterioration that, unless remedied, would result in secondary damage at failure.
PREVENTIVE MAINTENANCE Preventive Maintenance schedules drawn on the basis of manufacturers (OEM) guidelines need to be updated to specific requirements based on utilities operational experience, equipment behaviors & past data of similar utilities. These schedules could be based on fixed time or running hour’s basis depending upon service conditions & criticality of requirement.
PREVENTIVE MAINTENANCE For example, a common practice has been to replace or renew bearings after a specified number of operating hours, assuming that bearing failure rate increases with time in service. Preventive maintenance is usually more efficient than reactive maintenance.
PREVENTIVE MAINTENANCE Advantages Is cost effective in many capital intensive processes and equipments. Provides flexibility for the adjustment of maintenance periodicity. Increases component life cycle. Reduces equipment failures. Results in an estimated 12% to 18% cost saving over that found in a reactive maintenance program. Disadvantages Does not eliminate catastrophic failures. Is more labor intensive. Includes performing unneeded maintenance activities, which has the potential to result in incidental damage to components.
8.PREDICTIVE MAINTENANCE-CONDITION -BASED Predictive Maintenance (PDM) is a systematic approach to determining the need for equipment repair or replacement, and limiting maintenance activities to only those that are required to prevent costly major repairs or unscheduled downtime.
PREDICTIVE MAINTENANCE Various monitoring systems are used to detect and analyze incipient faults. Such conditions as temperature changes, vibrations, insulation resistance degradations, oil deteriorations, combustion product releases, metallurgical microstructure changes and many other detectable indicators can provide an early warning signal that failure is imminent unless maintenance is performed.
PREDICTIVE MAINTENANCE Predictive Maintenance is accomplished by combining and using all available information: diagnostic and performance data; maintenance histories; and operations logs and design data to make timely decisions about the maintenance requirements of plant equipment . The goals of predictive maintenance are to reduce maintenance costs and to extend the effective operating life of machinery through informed engineering decisions.
PREDICTIVE MAINTENANCE Preventive Maintenance (PM) can be deferred if PDM monitoring shows the PM procedure is not yet necessary. This can lower the overall parts and labor expenditures significant. (If it aint broke, dont fix it) Equipment with indications of probable failure prior to a scheduled PM activity can be identified and scheduled for maintenance prior to failure. This avoids unscheduled equipment downtime.
PREDICTIVE MAINTENANCE Advantages Provides increased component operational life and availability. Allows for preemtive corrective actions Results in decrease in equipment downtime Lower costs for parts and labor. Provides better product quality. Improves worker and environment safety. Raises worker morale. Increases energy saving. Results in an estimated 8% to 12% cost saving over that found in a preventive maintenance program. Disadvantages Increases investment in diagnostic equipments Increases investment in staff training.
9.PROACTIVE MAINTENANCE Proactive is the opposite of Reactive. Proactive maintenance is an activity performed to detect and correct causes of failure i.e. actions taken to correct conditions that could lead to material degradation. Instead of investigating material and performance degradation factors to determine the extent of incipient and impending failure conditions, proactive maintenance concentrates on identifying and correcting abnormal causes of failure that create unstable operating conditions.
PROACTIVE MAINTENANCE Proactive maintenance improves maintenance through better design, installation, maintenance procedures, workmanship, and scheduling. The characteristics of proactive maintenance are: Using feedback and communications to ensure that changes in design or procedures are rapidly made available to designers and managers. Employing a life-cycle view of maintenance and supporting functions. Ensuring that nothing affecting maintenance occurs in isolation. Employing a continuous process of improvement. Optimizing and tailoring maintenance techniques and technologies to each application. Integrating functions that support maintenance into maintenance program planning. Using root-cause failure analysis and predictive analysis to maximize maintenance effectiveness.
PROACTIVE MAINTENANCE Proactive maintenance employs the following basic techniques to extend machinery life: Specifications for new/rebuilt equipment Commissioning Precision rebuild and installation Failed-part analysis Root-cause failure analysis Reliability engineering Rebuild certification/verification Age Exploration (AE) and the relationship with Replacement of Obsolete Items Recurrence Control
PROACTIVE MAINTENANCEBenefits: • Providing enhanced utilization of available resources • Avoiding unnecessary disruptions • Ensuring objective problem solving • Facilitating development of a comprehensive set of solutions • Predicting other problems • Identifying, assembling, and integrating contributory circumstances • Focusing on preventing recurrence, as well as providing immediate corrective action • Identifying improvement opportunities Achieving these goals will provide the focus for corrective actions.
10. RELIABILITY CENTRED MAINTENACE HISTORICAL EVOLUTION OF RELIABILITY CENTRED MAINTENACE In the case of aircraft it was also commonly assumed that all reliability problems were directly related to operating safety. Over the years, However, it was found that many types of failures could not be prevented no matter how intensive the maintenance activities. Moreover, in a field subject to rapidly expanding technology it was becoming increasingly difficult to eliminate uncertainty.
RELIABILITY BASED MAINTENANCE Reliability-Centered Maintenance (RCM) integrates Preventive Maintenance (PM), Predictive maintenance and Proactive Maintenance to increase the probability that a machine or component will function in the required manner over its design life-cycle with a minimum amount of maintenance and downtime. These principal maintenance strategies, rather than being applied independently, are optimally integrated to take advantage of their respective strengths, and maximize facility and equipment reliability while minimizing life-cycle costs.
RELIABILITY CENTRED MAINTENANCE Advantages Efficient. Increased system reliability. Lowered costs due to no unnecessary maintenance. Minimized overhauls. Reduced sudden equipment failures. Maintenance focused on critical components. Incorporates root cause analysis. Disadvantages Significant initial costs for training, and equipment. Savings potential not readily seen by management.
11.MAINTENANCE TECHNIQUES Reactive maintenance comes naturally from the need to repair failed equipment. However, the high cost of repairs and the need for better reliability stimulated the search for new ways to reduce failures. Over the years, the analysis of equipment failures led to the adoption of preventive maintenance techniques that would prolong the mean time between failures and enhance the probability that equipment would be available when needed. These PM practices, such as oil changing and periodic parts replacement, lowered maintenance costs and increased reliability.
MAINTENANCE TECHNIQUE As the pressure grows to decrease maintenance costs and make do with less resources, predictive techniques that prescribe the minimum maintenance at the right time are added to the strategy when a failure indicator can be identified and monitored economically. Proactive maintenance is added as failure modes are analyzed and causes can be identified and eliminated. Now, the plant maintenance strategy integrates the use of corrective, preventive, predictive, and proactive techniques as appropriate for specific equipment
Cost of Maintenance Programs (Piotrowski 2001)in $per horse power per year18161412 REACTIVE10 PREVENTIVE 8 PREDICTIVE 6 RCM 4 2 0
12.PRINCIPLES OF MAINTAINABILITY DESIGN Great maintenance procedures cannot overcome poor equipment design. Every maintenance point should be directly visible and fully accessible to the maintainer. Special tools are rarely available when maintainers need them, so design all maintenance tasks to eliminate the need for special tools.