.0 Introduction to Reliability-centered Maintenance

1.1 What is Reliability-Centered Maintenance (RCM)? 1.1.1 Definition Reliability-Centered Maintenance, or RCM, is a logical, structured framework for determining the optimum mix of applicable and effective maintenance activities needed to sustain the desired level of operational reliability of systems and equipment while ensuring their safe and economical operation and support. Although RCM focuses on identifying preventive maintenance actions, corrective actions are identified by default. That is, when no preventive action is effective or applicable for a given item, then that item is run to failure assuming safety or a similarly critical consideration is not at issue. From that perspective, RCM identifies all maintenance. RCM is focused on optimizing readiness, availability, and sustainment through effective and economical maintenance. 1.1.2 Overview of Concept Prior to the development of the RCM methodology, it was widely believed that everything had a "right" time for some form of preventive maintenance (PM), usually replacement or overhaul. A widespread belief among many maintenance personnel was that by replacing parts of a product or overhauling the product (or reparable portions thereof), that the frequency of failures during operation could be reduced. Despite this commonly accepted view, the results seemed to tell a different story. In many instances, PM seemed to have no beneficial effects. Indeed, in many cases, PM actually made things worse by providing more opportunity for maintenance-induced failures. The RCM approach provides a logical way of determining if PM makes sense for a given item and, if so, selecting the appropriate type of PM. The approach is based on the following precepts: • The objective of maintenance is to preserve an item's function(s). RCM seeks to preserve a desired level of system or equipment functionality, not just operability for operability's sake. Redundancy improves functional reliability but increases life cycle cost in terms of procurement and support cost. • RCM focuses on the end system. The RCM process focuses throughout the life cycle on the end system, from design through retirement. It seeks to preserve end system functionality, not to prevent all failures. • Reliability is the basis for decisions. The failure characteristics of the item in question must be understood to determine the efficacy of preventive maintenance. RCM is not overly concerned with simple "failure rate"; it seeks to know the conditional probability of failure at specific ages (the probability that failure will occur in each given operating age bracket). • RCM is driven first by …