Monday 14 April 2014

RCM 2: Taxonomy and Core Principles.

Most organizations own hundreds or thousands of physical assets. These assets can be of different sizes, in only one site or spread in hundreds of locations, which can be fixed or mobile. Before any organization can apply RCM it must know what and where the assets are.

To perform equipment partitioning facilitates analysis and specifies analysis boundaries before starting the analysis. The MIL-STD-3034 standard recommends that care must be taken when defining what the boundaries of a single development will encompass so that no items are forgotten or are covered within multiple developments. Within this process, the assigned developers may still find it advantageous to subdivide the subsystem to simplify the analysis. This hierarchical approach to dividing subsystems enables the identification of an optimum level.

The ISO 14224 considers that a clear boundary description is imperative for collecting, merging and analyzing Reliability and Maintenance data from different industries, plants or sources. It also facilitates communication between operators and equipment manufacturers. Otherwise, merging and analysis is based on incompatible data. It is wise not to be too rigid about boundary definitions because as understanding grows during the RCM process, perceptions about what should or should not be incorporated in the analysis can change.

 It is possible to develop a hierarchy showing the primary functions of each of the assets in the assets hierarchy; it shows the relationship between functions at the same level. Then we must classify the assets and their elements into generic groups based on factors possibly common to several of the items (location, use, equipment subdivision, etc.). The name of this systematic classification is taxonomy.

Taxonomy ISO 14224
  The first five levels represent a high-level categorization that relates to industries and plant application regardless of the equipment units involved. This is because an equipment unit can be used in many different industries and plant configurations and, for analyzing the reliability of similar equipment, it is necessary to have the operating context.

The last four levels are related to the equipment unit with the subdivision in lower indenture levels corresponding to a parent-child relationship. The number of subdivision levels for the collection of Reliability and Maintenance data depends on the complexity of the equipment unit and the use of the data. A single instrument might need no further breakdown, while several levels can be required for a large compressor; the last level is only used in too complex equipment.

Once we already performed the taxonomy of equipment we can start the RCM analysis, but before we must keep in mind these core principles:

·         Failures happen.

·         Not all failures have the same probability.

·         Not all failures have the same consequences.

·         Simple components wear out, complex systems break down.

·         Good maintenance provides the required functionality for the lowest practicable cost.

·         Maintenance can only achieve inherent design reliability.

·         Hidden functions require special treatment.

·         Unnecessary maintenance takes resources away from necessary maintenance.

·         Good maintenance programs undergo continuous improvement.

These principles are very important because we always must think that to avoid all the failure are no possible and every failure is different, that the mission of good maintenance just provides the required functionality and reliability at lowest practicable recourses cost, deserving special attention to hidden failures.

Finally, we must consider that a good maintenance program undergo continuous improvement, so we never must finish our RCM program but we must refresh with new reliability data and new maintenance technologies. So we must include continuous improvement basics as the Deming Circle based:

Deming Circle used in Continuous Improvement programs.

  • Plan: Establishing the objectives of the RCM program.
  • Do: Implementing the program.
  • Check: Studying the actual results and compare against the expected results.
  • Act: Requesting actions on significant differences between actual and planned results.

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