The evolution of maintenance in the last hundred years can be classified into three generations related to failure modes, failure consequences and the strategies to avoid them.
The First Generation covers the period up to World War II, during those years the industry was not too mechanized, so downtime did not consider important for the process, at the same time, most equipment was simple, over-designed and easy to repair, so prevention of equipment failure was not a priority.
|First Generation of Maintenance
The wartime increased the demand for goods while the industrial manpower dropped sharply, this led to increased mechanization. So the failures in all types of machines were more numerous and complex and the downtime came into sharper focus. With this Second Generation started the concept of equipment overhauls done at fixed intervals, so the cost of maintenance also starts to rise relative to operating cost. Also, the amount of capital tied up in fixed assets together with a sharp increase in the cost of that capital led companies to start seeking ways to maximize the life of assets.
|Second Generation of Maintenance
The Oil Crisis accelerated the process of change in the industry. During this Third Generation the effects of downtime were aggravated due to the need for reducing costs and increasing productivity. In the same way, greater automation means more failures affect our processes and could have serious safety and environmental consequences, as the cost of physical assets and energy were growing too, they must work efficiently to ensure the maximum return on the investment.
The maintenance costs also were increased, to control them new research and development were focused in decision support tools, such as hazard studies and failure modes and effects analysis, new maintenance techniques, such as condition monitoring, new design of equipment with much emphasis on reliability and maintainability, and a major shift in the organization thinking towards participation, team-working and flexibility.
|Third Generation of Maintenance
Under this background, the Federal Aviation Agency FAA started some studies focused on increasing reliability and control maintenance costs in complex systems due to the number of random failures were much higher than the number of wear-out failures.
The first solution for this problem was defined in 1978 by F.S. Nowlan and H.F. Heap, (United Airlines) in their report AD-A066579 Reliability–Centered Maintenance. The target of this report was developing a procedure to allow ensure the functions of airplanes at minimum costs. This report had a wide influence several Air Transport Association ATA, US Department of Defense and UK Ministry of the Defence publications, guides, handbook and standards;
In 1999 the Society of Automotive Engineers SAE published, and review in 2009, the standard SAE JA 1011 Evaluation Criteria for Reliability-Centered Maintenance (RCM) Processed completed in 2002 with SAE JA 1012 A Guide to the Reliability-Centered Maintenance (RCM) Standard.
The SAE JA 1011 standard defines any RCM process as that ensures the following seven questions are answered satisfactorily and in this sequence:
a. What are the functions and associated desired standards of performance of the asset in its present operating context (functions)?
b. In what ways can it fail to fulfill its functions (functional failures)?
c. What causes each functional failure (failure modes)?
d. What happens when each failure occurs (failure effects)?
e. In what way does each failure matter (failure consequences)?
f. What should be done to predict or prevent each failure (proactive tasks and task intervals)?
g. What should be done if a suitable proactive task cannot be found (default actions)?