Introduction
RCM has so many benefits for reliability and cost optimization in the industry, that it is not fair not to apply RCM (Reliability Centered Maintenance) at all, either because they do not know the methodology, or because they do not “have the time or resources” to apply it or because they have had disastrous results applying it. Also, the approach of RCM by phases, a way to take advantage of the benefits of this tiered methodology, cannot be ruled out.
There is so much evidence of extraordinary results obtained through the proper use of the RCM methodology that there is no doubt about its effectiveness and very high cost-benefit ratio. John Moubray (author of the worldwide best-seller RCMII) wrote:
“The author and his associates have helped RCM companies in more than 1,500 sites spanning 44 countries and in almost every form of organized human endeavor. We have found that when RCM has been properly applied by well-trained people working on clearly defined and properly managed projects, the analyses generally pay for themselves within two weeks to two months. In fact, this is a very quick payback.”
One quickly reads that to obtain the benefits that any company would like to obtain in as short a time as two months requires three fundamental factors:
- Correctly applied, i.e., the right methodology.
- By well-trained people who understand all RCM precepts.
- In clearly defined and properly managed projects, i.e., managed with the support and direction of management.
The question arises as to what the experience of the readers of this article is, but from what we have seen in many organizations, some of what Moubray said is not true because many projects do not have successful results.
Why don’t we already decide to undertake projects applying these factors?
Well, the first thing is that when we examine the causes of equipment failures we find the following:
- Inadequate maintenance practices.
- Inadequate operation practices.
- Inadequate practices in the design and use of materials.
- Inadequate maintenance tasks.
In other words, we realize that the reason why we find ourselves in “putting out fires” mode has less to do with whether or not we have an optimal maintenance plan, and more to do with how we operate and maintain the equipment. And what types/quality of materials/spare parts we use. In other words, we have a lot of potential for improvement by attacking the root causes before we really need to optimize the plans. Of course, there will always be something to optimize in our maintenance plans to avoid the current high number of recurring failures in our equipment. This is reflected in item 4 of the above list “Inadequate maintenance tasks”.
Another reason why we don’t decide to undertake RCM projects is that we don’t know all the real benefits of RCM until we undertake a project, execute it fully, and wait and measure the results. Is it because it costs us too much to do this? The simple answer is, yes, we do. Why? Because we feel like we are putting out fires all the time and “we don’t have enough time or resources” to do something that “will pay off in two months”.
Exactly this case happened with a company, with which we reached an interesting agreement that has been the motivation for writing this article. The agreement was:
Perform a criticality analysis of their hundreds of industrial equipment, a process that their people enjoyed enormously by the way, and feed back the maintenance plans based only on the failure history. We would analyze the most important failures of this critical equipment and their causes. We would associate an RCM Failure Pattern to each failure (failure mode), review the current associated task to avoid the failure mode and then, only upon knowing the full nature behind the failure mode, take preventive or corrective action.
We will explain this method in more detail below.
Current options for RCM implementation
Since the development of RCM by Nowlan and Heap at the end of the 70s, different variants and ways of applying it have been developed. So much so that it was necessary for the SAE to create a standard to confirm whether a process could be called RCM or not (SAE JA1011). Even so, there are currently prevailing methodologies that their proponents call RCM, accompanied by some qualifier such as “accelerated (streamlined), reverse, simplified and others. Techniques offered to “obtain results faster than traditional RCM”.
In summary, the following options exist in the use of RCM:
- Apply RCM properly, with trained personnel and in well-managed projects, with management support.
- Apply RCM “well” and obtain all its benefits, at very high cost and use of resources.
- Apply RCM poorly, start it without completing it and get no benefits.
- Apply RCM derivations with good or bad results.
As we can see, all the options start by applying RCM, which seems not to be fully in tune with the causes of our equipment failures (list reviewed above). As we have seen, sometimes failures have more to do with how we operate and maintain the equipment than with selecting a specific optimal maintenance task at an optimal frequency. So what better than to start the analysis of our critical equipment by analyzing the causes of these failures and run these causes through the Failure Patterns and the RCM Decision Tree.
It would seem logical then that before moving on to a comprehensive plan review project we should consider that any investment of resources requires a cost-benefit analysis. For critical equipment, this relationship will most likely justify some level of RCM use to ensure the highest profitability and safety for operations. But it is also possible to advance by phases or levels.
PMO (Preventive Maintenance Optimization)
To understand the phases that we will explain below, we must understand one of the methodologies considered as “RCM in reverse”, known as the optimization of preventive maintenance (or planned in other references).
This methodology has 7 steps that we will list and explain briefly below. Steps 1 to 4 explain why it is called Reverse RCM and steps 5 to 7 are the same as “traditional” RCM. Each step will be documented in a Failure Mode and Effects Analysis (FMEA).
PMO steps
- Identify existing preventive maintenance (PM) tasks/frequencies: Here tasks and their frequencies should be extracted from any source. From preventive tasks, predictive plans (condition monitoring) to tasks executed by the operator.
- Identify which failure modes the PMs address: Understanding that each task is aimed at avoiding or mitigating a failure mode. Assuming that the maintenance plans are mature, we are interested in knowing the critical failure modes of the equipment. Pretty sure we will find them (and also the less critical ones).
- Identify in-service failures: All failures should be listed in the Failure Modes column, also with their causes and their Failure Patterns.
- Identify possible hidden failures and other credible failure modes: The last class of failure modes to be considered in the analysis. Identify potential hidden failures that are not being addressed by any maintenance task (step 2) or noted in the equipment failure history (step 3).
- Evaluate the consequences of each failure: Determine the consequences of each failure mode, such as safety risks, environmental impacts, production losses and costs.
- Identify proactive tasks for each critical failure mode.
- Identify other actions (fault finding, change or operate to failure).
This methodology is very attractive and logical for optimizing existing maintenance plans with adequate failure history data. It is applicable for plans with relatively few maintenance tasks. It seems almost totally inconvenient for plans with a very high number of maintenance tasks. The reason for this is that we would most likely be analyzing an excessive amount of tasks that should never have been written in the plans. In conclusion, we would be doing a monumental and in many cases unnecessary work and, paradoxically, we would be working much more than with the real RCM.
Implementation of RCM by phases
We begin by assuming the premise that those who wish to apply RCM in phases, which allows them to obtain high benefits with the least use of time and resources, is precisely because they are in “fire-fighting” mode and do not have the time or resources to embark on a comprehensive RCM project.
Moreover, these companies know that their big problem is not the maintenance plan itself, since the one they have is not adequately applied. Rather, they feel that there are really few adjustments they need to make to their plans in order to avoid the recurrence of current failures (without having to optimize all the plans).
We propose the following levels of RCM application:
Note: Each of the levels outlined in this segment requires sufficient knowledge of the RCM methodology. From the understanding of the Failure Patterns (new logic to understand maintenance), the FEA and the RCM decision diagram. And this can only be achieved through a formal training of the RCM methodology.
Level 1: Apply the PMO only from step 3 (Identify service failures) and then steps 5 to 7
This level makes a feedback of the maintenance plans but using RCM philosophies. A Pareto of the most recurrent failures is performed, reaching the level of component failure modes. The cause of the failure is analyzed, its failure pattern and based on these factors the appropriate policy is selected to prevent or mitigate the failure mode.
This policy can range from enforcing a specific torque procedure for a component whose failure mode (loosening) responds to Failure Pattern “F” (Infant Mortality) to changing a current cyclic replacement task for a component whose failure pattern is Random “E” to one of replacement by condition, more suitable for this pattern.
The meetings that take place to carry out this review are totally enriching for the team of people involved in the plans, all of them expressing total satisfaction with the process. They feel that they gain a lot with little effort, finding that the cost-benefit ratio motivates them to continue the analysis with other critical teams. Management sets achievable plan optimization goals and the analysis groups set their meeting schedules to meet these goals.
Level 2: Review of the congruence of critical replacement tasks with failure patterns
Review the replacement tasks that have the greatest impact on maintenance costs and/or require the most intrusive interventions on equipment. Be fully aware of the congruence between critical equipment PM tasks and RCM failure patterns. This means that a failure mode with random failure pattern, in any of its types D, E or F, cannot have a cyclic replacement task associated with it. This violates the “Law of RCM Congruence”.
In cases of random failure patterns, condition-based maintenance will be privileged in its two possible forms: Inspection (usually the equipment stopped) and condition monitoring (usually with the equipment in operation).
This super basic level of application of RCM philosophies will have a great impact on the optimization of your maintenance plans.
Level 3: Applying PMO to low or medium-criticality equipment
The PMO method explained above can be very well applied in teams where three conditions are met:
- That the equipment is of low or medium complexity.
- That it has mature maintenance plans, i.e. it has enough time to apply them and where all critical failure modes are covered. The condition of point 1 ensures that we know the critical failure modes.
- That you have a reliable failure history and/or personnel with experience on the equipment who can list the most common / critical failure modes of the equipment.
Level 4: Apply traditional RCM
This level can be started at any time. From before exploring some of the previous levels, or once we have gained experience and early wins by applying at least level 1.
This level will have to answer the seven RCM questions, performed in an appropriate manner, by trained personnel and directed by people with proven ability to conduct successful RCM studies.
Conclusion
We subscribe to the words of John Moubray “Since RCM was developed it has become apparent that there is no other comparable technique for identifying the true and safe minimum of what must be done to preserve the functions of physical assets. As a result, RCM has been used by thousands of organizations spanning almost every major field of organized human endeavor.”
We truly believe that applying RCM is the best cost-benefit decision for any organization and even for any criticality of equipment. Its benefits will far outweigh the resources and time spent. However, experience has given us the opportunity to take some “low-hanging fruit” and gain experience with the critical RCM topics such as failure patterns, the logical decision tree and a part of the FEA. These ripe fruits are achieved with some basic levels of analysis that only sufficient knowledge of RCM will help to discern.
References
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