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The SAE JA Standard on Evaluation Criteria for Reliability Centered Maintenance RCM Process has an interesting background including disappointing and successful stories before its principles were conceived and eventually incorporated into an international engineering standard.
There exist international standards on quality ISO 9, , risk ISO 31, , environment ISO 14, and, energy ISO 50, management and many other fields providing information and guidance on the practices, methods and processes designed by groups of highly qualified international experts. Trial and error is no longer acceptable out of the laboratory any more today. But, lessons learned from its practice in conjunction with regretful real-life incidents and accidents provide knowledge on their risks, mitigation and, prevention.
Most asset and maintenance management best practices and techniques are standard driven meaning they have been carefully defined and established. Comprehensive time-based maintenance tasks regimes were not able to provide sustainable operations any longer as the commercial aviation industry was about to undergo a major crisis.
Maintenance and reliability professionals were not able to find a clear relation between applied PM maintenance hours and components reliability. Furthermore, some maintainers experienced that applying less pm hours at longer time intervals resulted in improved reliability.
Aviation companies needed to comply with certain maintenance plans to retain their airworthiness certifications. Almost all recommended maintenance tasks consisted in overhaul of parts before they reached a useful life expressed in operating hours. The fact that the US Federal Aviation Administration FAA denied permission to manufacture the aircraft model to Boeing raised a major alarm in the aviation industry.
It was thought that a larger size plane with three times passenger capacity would require much more maintenance and operating costs than its predecessors. This new design denial in conjunction with a poor safety record of nearly 60 crashes for every 1,, take offs and high operating costs demanded new aircraft design, operation and maintenance perspectives which led the creation of RCM.
Efforts to understand non-structural aircraft components failure patterns led Stanley Nowlan and Howard Heap, both from United Airlines, to develop a new approach towards maintenance. They documented their methodology for developing failure consequence management policies in a report published by the U. Department of Defense in Their process was called Reliability Centered Maintenance RCM and was based on a common-sense procedure with a decision diagram for creating Maintenance strategies to protect assets functions.
RCM is defined as a process to determine what must be done to keep assets doing what their operators want them to do in their current operating context. Since its origins, RCM has been used in many industries, and in almost every industrialized country in the world. The standard provides the criteria to establish if a given process follows the creeds of RCM as originally proposed.
It can also serve as a guide for organizations seeking RCM training, facilitation or consulting. The very first step for applying RCM to a physical asset, entails defining its operating context and required functions under it. The logical starting point to design a maintenance or failure management strategy or an asset management policy as the Standard calls it is understanding clearly what is being demanded from the asset.
This represents a change in perspective for maintainers. Often the maintenance department is not involved in determining why any particular asset is actually there. If we are to sustain performance of specific functions, we need to know exactly what the functions are as well as the operating parameters that define the performance levels needed to fulfill operational demand.
In order to properly define the operating context, the RCM team must describe functions following this structure in accordance with the standard:. It is instrumental to have a perfect understanding of the asset functions and the desired performance level to determine functional failures.
There could be total or partial functional failures. That means, the asset may not be able to fulfill a function at all or that it may perform it at a lower than the desired performance level. The SAE standard asks that all the failed states associated with each function be identified so that we can identify all the relevant failure causes. A failure mode is a single event, which causes a functional failure to occur and each failure mode usually has one or more causes.
So, we need to brainstorm on all possible events causing assets to impair their ability to perform each specific function to the desired levels of performance. The standard recommends not being too superficial in the causation level of the failure modes. When listing failure modes consider:. The standard recommends several relevant considerations to help understand how serious each failure cause might be.
Failure effects help determining the extent to which each failure mode is relevant by taking into consideration the following:. Failures effects are classified into categories based on evidence of failure, impact on safety, the environment, operational capability, and cost. We should be able to decide which of the four categories apply to each failure mode effects. Only one category must be chosen — whichever is most severe.
Hidden and evident failure modes must be clearly separated. Failures with safety or environmental impact must be distinguished from those only having economic impact either by operational or non-operational consequences. Like every step within the RCM process, failure consequence determination is critical. Maintenance strategies are carefully selected for every critical failure cause based on a decisional procedure using the failure consequence as the starting point.
The most likely predominant failure pattern for each identified failure should be considered at the time of recommending any failure management strategy. Failures modes may occur with age or usage or randomly. They may also occur prematurely or following a wear out pattern after some significant operating time.
Care must be taken to recommend maintenance tasks based on actual predominant failure patterns. SAE JA acknowledges 5 possible maintenance strategies that must be applied to mitigate the consequences of any given failure. They are the following:. When formulating maintenance tasks appropriate frequencies must be assigned for them to effectively address failure effects.
Some math and statistical formulas are used to support the task interval decision. Thus, it is wise to have a knowledgeable internal auditor evaluate and accept recommendations made as part of the RCM process.
It is particularly useful to people who wish to get RCM services training, analysis, facilitation, consulting, etc.
Successful RCM implementation requires trained multidisciplinary groups to apply the process with the guidance of a certified facilitator who masters its execution. Successful implementations report significant reduction of applied pm man-hours, improved safety performance, and enhanced asset reliability and availability resulting in significant financial performance.
Email address:. View All Events. Determine how an asset can fail to fulfill its functions functional failures. Define the causes of each functional failure failure modes. Describe what happens when each failure occurs failure effects.
Classify the consequences of failure failure consequences. Determine what should be performed to predict or prevent each failure tasks and task intervals. Decide if other failure management strategies may be more effective one-time changes.
The Operational Context and Functions The very first step for applying RCM to a physical asset, entails defining its operating context and required functions under it. In order to properly define the operating context, the RCM team must describe functions following this structure in accordance with the standard: The conditions in which a physical asset or system is anticipated to operate shall be defined, recorded, and available. All function statements shall contain a verb, an object, and a quantitative performance standard whenever possible.
The performance standards used in function statements shall be the level of performance desired by the user of the asset in its current operational context. The design capability should not be used in the function statement. The SAE standard asks that all the failed states associated with each function be identified so that we can identify all the relevant failure causes Failures Modes A failure mode is a single event, which causes a functional failure to occur and each failure mode usually has one or more causes.
When listing failure modes consider: All failure modes reasonably likely to cause each functional failure shall be identified. Usually consensus is used to decide which failure modes to analyze and which ones to discard.
The level of causation for failure modes must be exhaustive enough so appropriate failure management policies can be assigned to manage them. Failure modes listed in the analysis must consider events that have happened before, the failure modes being prevented in the existing PM program and other events that are likely to occur in the actual operating context but has never happened.
Human and design errors causing failure event must be included in the failure mode list unless they are being addressed by other analysis methods.
Failure effects help determining the extent to which each failure mode is relevant by taking into consideration the following: Is there any evidence that the failure has occurred?
What is the potential impact to the failure poses on the personnel safety? What is the potential impact to the failure poses on the environment? How is production or the operations affected? Is there any physical damage caused by the failure? Is there anything that must be done to restore the function of the system after the failure?
Failure Consequences Failures effects are classified into categories based on evidence of failure, impact on safety, the environment, operational capability, and cost.
Maintenance Strategies Selection The most likely predominant failure pattern for each identified failure should be considered at the time of recommending any failure management strategy.
They are the following: Condition Based Maintenance Tasks. Such detection must occur early enough so that corrective action can be taken before the loss of function. A condition monitoring task is applied at fixed intervals to enable trending of the function loss prior to a Functional Failure. Scheduled Overhaul Tasks — Time based repair tasks must be carried out based on the useful life of the component. That is, the time at which the component failure rate ceases to be constant.
Theoretically, at the end of the useful life the component failure rate increases beyond a rate that we can tolerate. Besides the useful life of the item, the cost of the preventive repair also needs to be evaluated. This is, a comparison of the cost of the overhaul work against that of the functional failure must confirm the economic viability of the task.
Scheduled Replacement Tasks — Scheduled discard and replacement tasks are considered when it is demonstrated that replacing is more cost effective than overhauling the item.
Failure Finding Tasks — These tasks are intended to detect hidden failures associated most of the time with protective devices or redundant components. We must ensure that it is physically possible to perform the recommended failure finding task and that the suggested task frequency is acceptable to the owner of the asset.
More will be said about task frequency later in the book. Share on:. Newsletter Email address:. June 8 am - June 12 pm.
An introduction to reliability-centered maintenance
This SAE Standard for Reliability Centered Maintenance RCM is intended for use by any organization that has or makes use of physical assets or systems that it wishes to manage responsibly. RCM is a specific process used to identify the policies which must be implemented to manage the failure modes which could cause the functional failure of any physical asset in a given operating context. This document is intended to be used to evaluate any process that purports to be an RCM process, in order to determine whether it is a true RCM process. This document supports such an evaluation by specifying the minimum characteristics that a process must have in order to be an RCM process. Subscribers can view annotate, and download all of SAE's content. Revision History Related Info. Issuing Committee: G Supportability Committee.
Reliability Centered Maintenance (RCM)
The applicability of a task is determined by the characteristics of the item, and its effectiveness is defined in terms of the consequences the task is designed to prevent. In wind farm operations, Reliability-Centered Maintenance RCM is an advanced strategy used to optimize reliability, production, and asset life for wind farm owners. RCM programs have existed since the s and were originally developed and proven in the aviation industry and the principles were later adopted by the nuclear energy industry. Although there are many similarities between aviation, nuclear energy, and wind energy in terms of maintenance practices, wind seems to have been a late adopter of the cost effective strategies of RCM.