Note: A copy of the Nowlan and Heap is included at the end of this post.
The purpose of RCM is to provice a process to develop the right maintenance at the right time for the right reasons.
The origination of RCM was the December, 1978 document and report developed by United Airlines under the Office of Assistant Secretary of Defense contract MDA 903-75-C-0349 by F. Stanley Nowlan and Howard F. Heap. The purpose was to advance the work performed on aircraft maintenance under FAA maintenance development programs MSG-1 (Boeing 747) and MSG-2 (Douglass aircraft) based upon the discovery that the primary cause of defect issues was time-based and intrusive maintenance. The first use of the term RCM was advanced in what is now referred to as the ‘Nowlan and Heap,’ which was the extension of a Dept of Defense program initiated in 1974, which was associated with the 3M (Materials, Maintenance and Management) programand not initially referred to as RCM.
The Department of Defense was looing for a robust method of addressing the development of maintenance programs. The authors and United team were part of the MSG-1 and MSG-2 programs which focused on periodical maintenance for aircraft. In the development of the military program they named named Reliability-Centered Maintenance, which we now refer to as Classical RCM, that addressed areas that fit non-aircraft issue such as task intervals, hidden function failures, and structural maintenance. These were addressed in the 1978 report.
By 1985, the MIL-P-24534A (MIL-P) ‘Military Specification: Planned Maintenance System, Development of Maintenance Requirement Cards, Maintenance Index Pages and Associated Documentation,’ had been developed and became the standard for the NAVSEA method. For a majority of shipboard systems this met the goal of improved equipment readiness and optimized maintenance for Naval systems. For electronics and aircraft, the development of the NAVAIR processes were expanded from Classical RCM which primarily impacted the frequency of maintenance tasks and the robustness of the evaluation. The other component that both the NAVSEA and NAVAIR systems added to the process was the ‘Backfit RCM,’ referred to as the Maintenance Effectiveness Review. This provided a feedback loop to review maintenance tasks and determine if they met requirements or should be altered.
Nowlan and Heap defined RCM as: “A logical discipline for developing a scheduled maintenance program that wil realize the inherent reliability levels of complex equipment at minimum costs.” The MIL-P expanded the definition as: “A method for determining preventive maintenance requirements based on the analysis of the likely functional failures of hardware having a significant impact on safety, operations and support functions.”
In effect, RCM is a process to provide evidence of the need for maintenance to meet the operating context of an asset.
I have noted that the end-goals of classical RCM processes have been misconstrued through semantics and not practice. This has primarily been due to the number of consulting organizations that either demonize the process in favor of their own methods, or to introduce their ‘new and improved RCM,’ which is rarely RCM at all and, in many cases, has become bastardized to the point of not resembling any of the concepts or processes behind RCM.
Classical RCM is a process that results in a series of options for maintenance tasks while providing logical and evidence-based reasons for each, as well as documentation:
- Preventive Tasks:
- Condition-Based Tasks: detection of a condition initiates maintenance such as static pressure across an air filter;
- Time-Directed Tasks: such as periodic tests and inspections;
- Failure Finding: normally a test on a safety device to ensure it functions at the time of testing;
- Servicing: such as replenishing fluids and other consumables;
- Lubrication: determined as a required function.
- Alterative Maintenance: it can be determined that a reliability issue or maintenance can be engineered or modified out to improve reliability.
- Corrective Maintenance: planned repairs or not everything has to be maintained and, yes, can run to failure.
One of the important parts of RCM is to partition systems into digestable parts and to determine the needed inputs and outputs of the partitioned system. This means to determine the function of the selected system and associated sub-components. The next part is the FMEA (Failure Modes and Effects Analysis) that is used to evaluate the various methods that would cause the system not to meet its intended functions. This is performed through an RCM Logic Tree, which evaluates by safety, mission, regulatory and all other reasons.
There are seven steps to the process once an asset has been defined through partitioning:
- What are the functions and associated desired standards of performance of the asset in its present operating context (functions);
- In what ways can it fail to fulfill its functions (functional failure);
- What can cause each functional failure (failure modes);
- What happens when each failure occurs (failure effects);
- In what way does each failure matter (consequences);
- What should be done to predict or prevent each failure; and,
- What should be done if a suitable proactive task cannot be found (default action).
When possible during the process failure data can be provided, sometimes it is not possible. When local history is not available data can be used based upon the general, or advanced, failure rates of components, such as the IEEE Gold Book and other studies.
One of the problems that had occurred once the military process started moving into the civilian side in the late 1990s was consulting firms and consultants that would latch their practices to the term. This has resulted in a lot of confusion and disillusionment. Proper RCM requires the inclusion of all aspects and stakeholders surrounding an asset from maintenance to operations, supervision to practitioners, even the CMMS folks to ensure that scheduling of tasks is possible, and others. Templated ‘RCM’ and programs that do not involved the stakeholders are NOT RCM. They are markeing and sales tools for consultants to provide something that is claimed, plain and simple. Worse are those that suggest that a facilitator should not, or does not need to, understand the systems being analyzed.
One of the huge benefits of an actual RCM program is the study of your systems in their own operating context and not in generic context, or whatever some charlatan has determiend based upon a book or two. False RCM practices occur because someoone has sold management on a ‘cheaper’ method that uses fewer resources (or none) to acomplish, or can be accomplished, through a software database has resulted in serious instances including death. Personally, I see a lot of this as scam artists at work.
RCM is a process-based tool that requires resources and information to accomplish a goal (effective maintenance) understanding that the number one cause of equipment failure can be the maintenance, or lack of, as the primary cause of failure. There are no short cuts in using this highly effective tool.
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