Following are the maintenance strategies that are commonly applied in the plants. Breakdown Maintenance or Operate to Failure or unplanned Maintenance Preventive or Scheduled Maintenance ; Predictive or Condition Based Maintenance ; Opportunity Maintenance ; Design out Maintenance The equipment under breakdown maintenance is allowed to run until it breaks down and then repairing it and putting back to operation. This strategy is suitable for equipments that are not critical and have spare capacity or redundancy available.
In preventive or scheduled Maintenance, maintenance actions such as inspection, lubrication, cleaning, adjustment and replacement are undertaken at fixed intervals f numbers of hours or Kilometers. An effective PM program does help In avoidance of accidents. Condition monitoring (CM) detects and diagnoses faults and it helps in planned maintenance based on equipment condition. This condition based maintenance strategy or predictive maintenance is preferred for critical systems and for such systems breakdown maintenance is to be avoided.
A number of CM techniques such as vibration, temperature, oil analysis, etc. Have been developed, which gulled the users in planned maintenance In opportunity maintenance, timing of maintenance is determined by the procedure adopted for some other item n the same unit or plant. In design out maintenance, the
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It may be mentioned that a best maintenance strategy for each item should be selected by considering its maintenance characteristics, cost and safety. In addition to the above, new strategies concepts such as Proactive Maintenance, Reliability Centered Maintenance (ARC), Total Productive Maintenance (TEMP), etc. Eve recently been evolved to look it from different perspectives and this has helped in developing effective maintenance. In proactive maintenance, the aim is identify what can go wrong, I. E. By monitoring of parameters that can cause failures.
In ARC, the type of maintenance is chosen with reliability of the system in consideration, I. E. System functions, failures relating to those functions and effects of the dominant functional system failures. This strategy in the beginning was applied to critical systems such as aircrafts, nuclear and space applications. At present, this is being extended to critical systems in the plant. TEMP, a Japanese concept, involves total participation of all concerned. The aim is to have overall effectiveness of the equipment with participation of all concerned using productive maintenance system.
The two organization structures that are common are: Centralized and Decentralized. A decentralized structure would probably experience a lower utilization than centralized one but would be able to respond quickly to breakdowns and would achieve higher plant availability. In practice, one may have a mix of these two. A maintenance organization can be considered as being made up three necessary and interdependent components. 1 . Resources: men, spares and tools 2. Administration: a hierarchy of authority and responsibility for deciding what, when and how work should be carried out. . Work Planning and Control System: a that is needed for correctly directing the maintenance effort towards defined objective. It may be mentioned that maintenance / production system is a continuously evolving organism in which the maintenance organization will need continuous modifications in response to changing requirements. Moreover, it is required to match the resources to workload. Maintenance activities – be it preventive or condition monitoring, involve use of resources- men and materials including documents.
This requires coordination amongst the involved personnel so that these are timely undertaken. Work planning and control system under maintenance management in the plant ensures this and provides planning and control of activities associated with maintenance. This means application of general management principles of planning, organizing, directing and controlling to the maintenance functions, e. . To the establishment of procedures for development of maintenance strategy and to models for describing the flow of work through maintenance work planning department.