The name Reliability Centered Maintenance lends itself to a process that is used to develop proactive maintenance for an asset, but RCM can also be used to formulate scores of solutions that reach far beyond maintenance. These solutions can offer tremendous benefit to an organization. Nevertheless, when applying RCM, many organizations focus only on the development of a proactive maintenance program, which doesn’t take full advantage of RCM’s powerful principles. This book sets forth the principles of RCM in a straightforward manner so that those interested in applying RCM can be aware of not only how uncomplicated the application of RCM can be, but also how powerful it is.
1.2 Elements that Influence a System
It is especially important to look beyond proactive maintenance because there are so many elements that influence a system, as depicted in Figure 1.1.
Figure 1.1 Examples of elements that influence a system
It doesn’t matter what the equipment is. Many factors have a direct effect on equipment performance: the scheduled maintenance that is applied, the operating procedures that are performed, the technical publications that are referenced, the training programs that are attended, the design features that are in service, the spare parts (or lack thereof) that are relied upon, how often an asset is operated, where equipment is required to function, and the emergency procedures that are in place. If these strategies are well developed, the equipment (and thus the organization) benefit. If any of these strategies are ill-conceived or inappropriate, the process by which the equipment plays a part suffers.
1.3 The Essence of RCM: Managing the Consequences of Failure
It is often wrongly believed that equipment custodians are in the business of preventing failure. Although it is possible to develop strategies that do prevent some failures (see Chapter 9), it is nearly impossible to prevent all failures. For example, is it possible to prevent all failures associated with an electric motor? How about an automobile starter, avionics equipment, or a turbine engine? Certainly not. Thus, other strategies are often put in place in order to manage otherwise unpreventable failures when they occur.
For example, organizations rely heavily on operating procedures, emergency procedures, training programs, and redundancy in the design of equipment, as depicted in Figure 1.1. There are three fully redundant hydraulic systems on most commercial aircraft because it is understood that all causes of failure for a hydraulic system cannot be prevented. If one of the three systems fails, two fully redundant systems are available to provide the required hydraulic power for safe flight. Because all failures cannot be prevented, responsible custodians must put other solutions in place to properly deal with failure when it occurs. In other words, responsible custodians are in the business of managing the consequences of failure—not necessarily preventing them.
Myriad issues, such as incomplete operating procedures or poor equipment design, can negatively affect equipment performance. For that reason, it is incredibly important that these issues are identified and included in an RCM analysis. Including them allows the matter to be analyzed using RCM principles so that a technically appropriate and effective solution can be formulated.
One of the major products of an RCM analysis is the development of a scheduled maintenance program. However, as depicted in Figure 1.2, RCM can help formulate other solutions such as the development of a proactive maintenance plan, new operating procedures, updates to technical publications, modifications to training programs, equipment redesigns, supply changes, enhanced troubleshooting procedures, and revised emergency procedures.
In the context of RCM, these other solutions are referred to as default strategies, as depicted in Figure 1.3.
Figure 1.2 Examples of solutions that RCM can yield
Figure 1.3 RCM can yield a scheduled maintenance program and default strategies
In the context of RCM, together, scheduled maintenance tasks and default strategies are referred to as failure management strategies, as depicted in Figure 1.4. These solutions are designed to manage failure.
Figure 1.4 Failure management strategies
1.5 The Evolution of RCM Principles
It is important to understand the evolution of RCM in order to appreciate the majesty of its principles. RCM’s evolution is best told as a story, as it was told to me.
The story starts in the mid 1950s in the commercial airline industry where, at the time, it was believed that nearly all failures were directly related to operating age. In other words, failure was more likely to occur as operating age increased. Figure 1.5 illustrates this point.
The x-axis represents age, which can be measured in any units such as calendar time, operating hours, miles, and cycles. The y-axis represents the conditional probability of failure. The philosophy associated with the failure pattern is that, assuming an item stays in service and reaches the end of the useful life, the probability of failure greatly increases if it remains in service. In other words, as stated by United Airlines’ Stanley Nowlan and Howard Heap, it was believed that “every item on a complex piece of equipment has a ‘right age’ at which complete overhaul is necessary to ensure safety and operating reliability.” Therefore, it was believed that the sensible thing to do was to overhaul or replace components before reaching the end of the useful life with the belief that this would prevent failure.
The mindset that failure was more likely to occur as operating time increased was deeply embedded in the maintenance programs. At the time, approximately 85% of aircraft components were subject to fixed interval overhaul or replacement. The maintenance programs were very high in scheduled overhauls and scheduled replacements.
Figure 1.5 Traditional view of failure
Time marched on. By the late