The developers of RCM took the unusual view that the goal of computer maintenance should be to keep the computer doing what its users want it to do, rather than preventing failures for the sake of preventing failures.

With this emphasis on preserving what the user wants, one definition of RCM is:

A process used to determine what needs to be done to ensure that any physical asset continues to do what its users want it to do in its current operating context.

It is therefore not surprising that determining the operating context and what the user wants the equipment to do is the starting point for the RCM process, which is applied by asking and answering the following seven questions:

   • What are the functions and associated performance standards of the asset in its current operating ?    

   • In what way does it not fulfill its functions?

   • What causes each functional failure?

   • What happens when a failure occurs?

   • How does each failure matter?

   • What can be done to predict or prevent each failure?

   • What should be done if a suitable proactive task cannot be found?

SELECTION OF MAINTENANCE TASKS

Once each failure mode has been categorized according to failure consequences, structured decision logic is used to select maintenance tasks. The RCM decision logic first looks to see if it is appropriate to perform a scheduled task to predict when the failure mode will occur.

If such a task is not appropriate, RCM then considers whether the failure should be prevented by periodic restoration of the element's original strength before it fails, and if not, whether a scheduled replacement of the element (before it fails) is appropriate.

Failure Prediction:

This involves monitoring the equipment to identify a detrimental change (ie, a warning) that indicates the failure is in the process of occurring (early enough that action can be taken before the failure actually occurs). This is known as condition-based maintenance or condition monitoring.

The frequency with which the equipment should be monitored is governed by the time it would take from when the warning can be identified to the point where total failure occurs. This is illustrated in the following diagram: warning is displayed at point P (potential failure) and total failure occurs at point F (functional failure).

The monitoring task must be carried out in an interval that is less than the time between P and F (known as the P-F interval). If it is practical to monitor point P and the P-F interval is long enough to take action to reduce, avoid or eliminate the consequences of the failure, then it may be possible to perform the condition monitoring task.

Failure prevention:

If the failure cannot be predicted when it starts to occur, then RCM looks to see if it can be prevented from occurring. This would mean performing some kind of intervention even before a failure starts.

In the RCM task selection logic, the available options are:

   • Scheduled Restore – This is where the computer is checked at a fixed interval, regardless of its    condition at the time.

   • Scheduled Discard – This is where a component is retired, discarded, and replaced (with a new one) at a fixed interval, regardless of its current condition.

Scheduled restoration and scheduled decommissioning are performed before the wear zone (ie, toward the end of “life,” which is the age when your conditional probability of failure begins to increase rapidly).

Sometimes these tasks are performed earlier (that is, the task is performed more frequently) if the consequences of the failure are very serious. This will increase the frequency of the scheduled task and provide a "safety factor".

What should be done if a suitable proactive task is not found?

RCM's task selection logic ensures that proactive tasks are identified for only those failure modes that require them. When no suitable proactive task can be found, there remains the question of what else could be done to manage the failure mode.

In addressing this question, RCM takes special note of the consequences of the failure. For example, when the consequences are purely economic, RCM allows no scheduled maintenance (or operation to failure) as a valid default action; however, doing nothing is not an option if the failure mode has environmental or safety consequences.

Possible default actions are:

•  No Scheduled Maintenance – These failure modes are allowed to occur and then are repaired. RCM allows this default action only when the consequences of the failure are economic (i.e. operational and non-operational consequences)
•  Bug detection: This applies only to bugs that have hidden consequences. The protection device or system is tested at regular intervals to see if it still works or not (and repaired if it fails).

Redesign: RCM recognizes that sometimes maintenance cannot satisfactorily handle a failure mode and that a one-time change (in the equipment, the way it is used, or the people who use it) may be required. Redesign is mandatory if no proactive task can be found for failure modes that have environmental or safety consequences, while redesign is optional for failure modes that have only economic consequences.

RCM APPLICATION

It is not possible for one person to answer all the questions that RCM asks. The solution is to bring together a group of people (the “RCM analysis group”) who have technical knowledge about the equipment, knowledge of its operation (within its current operating context), and a basic understanding of RCM itself (through of adequate training).

A strong understanding of the RCM process is also required to guide the RCM review group through the RCM process and achieve consensus in answering questions. This role is fulfilled by an RCM facilitator.

Members of the RCM analysis group come from equipment maintainers, operators, possibly manufacturers/suppliers, and occasionally specialists. The most important factor is that they know and understand the equipment being tested using the RCM process.

The goal is to reduce the size of the "black hole" in knowledge (ie, the black area that represents "everything there is to know about the team"). Inevitably, there will be some gaps in the group's combined knowledge, but by the end of the RCM analysis each member of the group will have gained useful knowledge about the equipment from other members of the group.

RCM Application

Under the guidance of the RCM facilitator, the group follows the RCM process.

The results of the analysis are:

• A list of maintenance tasks to be performed by maintenance personnel at specific intervals
• A list of tasks to be performed by operational staff at specified intervals
•  A list of redesigns to consider for implementation.

When the RCM analysis is complete, the result should be audited by whoever has overall responsibility for the equipment or system. This is so you can ensure that the analysis has been carried out correctly and that it is sensible and defensible.

The final step is to implement the results of the RCM analysis when the audit is complete.

WHAT RCM ACCOMPLISHES

RCM has been applied in a wide range of industries in most countries of the world. Properly applied, RCM produces an optimized maintenance schedule for the equipment in its operating context; the goal is to achieve inherent levels of equipment reliability and availability. The maintenance derived from RCM and the process itself provide the following benefits:

• Safety - Increased safety and environmental protection: improved maintenance of existing protection devices, systematic review of the safety implications of each failure, implementation of clear strategies to prevent failure modes that may affect safety or violate regulations environmental damage due to failures caused by unnecessary maintenance
• Performance - Improved operational performance: an emphasis on maintenance requirements for critical items of equipment, extension or elimination of overhaul intervals, shorter and more focused maintenance tasks resulting in less extensive and costly downtime, fewer maintenance problems "burned out" after maintenance (by eliminating unnecessary maintenance actions) and the identification of unreliable components
• Profitability - Increased Profitability: Less unnecessary routine maintenance, prevention or elimination of costly failures, clearer operating policies, and clearer guidelines for purchasing new maintenance technology
• Quality - Improved quality due to a better understanding of equipment capability and capacity, clarification of equipment specifications and configuration requirements, confirmation or redefinition of equipment operating procedures, and clearer definition of tasks and objectives of maintenance
• Life Cycle Cost – Reducing life cycle costs by optimizing maintenance workloads and providing a clearer view of spare parts and staffing requirements
• Equipment Life: Increased life of expensive equipment due to increased use of condition maintenance techniques.
• Maintenance Data – A comprehensive maintenance database that:

        -  Provides a better understanding of the equipment in its operational context

        - Leads to more accurate drawings and manuals

        -Allows maintenance programs to be more adaptable to changing circumstances

                    - Documents the knowledge that people have about each team

• Motivation - Greater motivation of people, particularly those involved in the review process. This provides a better understanding of the equipment in its operating context and a broader "ownership" of the resulting maintenance schedules.
• Teamwork – Improved teamwork brought about by the highly structured group approach to discussing and addressing maintenance issues.

Conclusion

RCM produces results very quickly; most organizations can complete an RCM review on existing equipment and achieve substantial benefits in a matter of months.

It is also an ideal approach to determining maintenance requirements for new equipment of all types. When applied correctly, it transforms both the maintenance requirements themselves and the way the maintenance function as a whole is perceived.

Author: Mario Jimenez

Publication Date: 27/06/2022