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How Does a PM Program Help Eliminate Component Failures?
By Mike Poland, Life Cycle Engineering
As appeared in the July 2009 Edition of Reliable Plant Mail e-newsletter
First we must define what PM stands for. According to Life Cycle Engineering’s RX Definitions, this could have one of many meanings. It could refer to Periodic Maintenance, Planned Maintenance, Predictive Maintenance (although normally abbreviated PdM), and Preventive Maintenance. Despite the definition of each and how they differ, they all relate to asset care. A properly cared-for asset will net much higher utilization at a much lower total cost of ownership. This is accomplished by establishing a program that mitigates or eliminates failure.
- Periodic Maintenance is the cyclical maintenance actions or component replacements carried out at known regular intervals. Usually intrusive, they are often based on repair history and regulated by current inspection results. Periodic maintenance includes inspecting, testing, partial dismantling, replacing consumables or complete equipment items, lubricating, cleaning and other work short of overhaul or renovation. This usually requires equipment to be scheduled out of service and may be done at intermediate intervals, usually ranging from monthly to annually.
- Planned Maintenance is, by virtue of cost, importance, extensive labor and materials required, etc., planned to ensure, when scheduled, that it can be completed with the least interruption to operations and the most efficient use of maintenance resources.
- Predictive Maintenance is the use of instruments and analysis to determine equipment condition in order to predict failure before it takes place so corrective maintenance can be done in a planned and scheduled fashion. Examples include vibration analysis, oil analysis, thermography, airborne ultrasonics, NDT, motor current signature analysis, trending of process parameters, etc.
- Preventive Maintenance is time or cycle-based actions performed to prevent system functional failure. This proactive maintenance type generally includes scheduled restoration and scheduled discard tasks.
To ensure proper asset care, we must first understand our asset’s place in the functional hierarchy and its criticality relating to production process or value stream. This will also yield our lowest maintainable component. We now have the linkage to work orders, bills of material, and reliability analytics. Once this is established, we then must understand the risk of the failures related to this component to determine the type of analysis we will use for developing our control plan to mitigate or eliminate these failures. This may direct us to a traditional Reliability Centered Maintenance approach, a simplified Failure Mode and Effect Analysis, to follow the manufacturer’s recommended maintenance, or to take no action since the component does not warrant any maintenance strategy due to a low risk ranking. In the event a hidden failure mode is identified for a critical component, a redesign would be required.
Once predominant failure modes are identified, controls must be put in place in the form of tasks. The preventive maintenance tasks must then be developed in the Task or Asset Activity module of the EAM system so that a work order can be generated, planned and scheduled. In order to be effective, this task must meet the following: 1) based on a predominant failure mode, 2) comprehensive, 3) organized, 4) repeatable, 5) value-added, 6) proper interval, and 7) valid duration. There also should be a method to identify the skill level and acceptance criteria necessary to accomplish the task. Finally, a business process must exist to provide feedback on the condition of the component, actual duration to accomplish, and reliability analytics in place to validate all of the above.
© 2009 Life Cycle Engineering, Inc.
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