History of RCM

2.3.1. Use of RCM in commercial aviation and by the military

The RCM method has its origins in the commercial aviation industry in the late 1960s. With the advent of wide bodied aircraft, beginning with the Boeing 747, it was financially imperative to optimize PM; that is to perform just the correct amount of PM to achieve high safety, availability and reliability.

The method was designed to make use of two concepts that were usually not adequately considered in PM programme: (1) complex equipment does not generally experience an abrupt wearout indicated by increasing failure rates; and (2) the

emphasis in PM should be on maintaining important system functions.

Out of a 1969 meeting of airline engineers representing the initial purchasers of the Boeing 747 aircraft came MSG-1, which included the basis for the maintenance programme. The airline industry subsequently developed MSG-2 and is currently using MSG-3 based on these same philosophies.

The US Department of Defense adopted the principles from MSG-2 in 1975.

It named the process RCM and directed that the method by broadly applied to military hardware. It published an RCM textbook in 1978.

In 1981, the US Naval Sea Systems Command completed its RCM handbook.

In the same year, the US Navy published a Military Standard for application of RCM to naval aircraft. By then RCM was being employed by the US Army Air Force and Navy for several classes or aircraft and ships.

2.3.2. Pilot applications of nuclear plant RCM

In 1984, the Electric Power Research Institute (EPRI), USA, and its utility advisory boards recommended that the usefulness of RCM be evaluated in trial applications to single systems at selected nuclear power plants. The first EPRI application of RCM was on the component cooling water systems of Florida Power and Light's Turkey Point Units 3 and 4. The study recommended 24 tasks that differed from the existing ones. A project team drafted changes to the plant

procedures for the time directed and condition directed preventive maintenance tasks that were identified. This package of suggested PM changes was used in the

evaluation of the plant PM programme at Turkey Point.

The application of RCM to the main feedwater system at Duke Power's McGuire station began shortly before the end of the Turkey Point pilot study. The RCM pilot study team investigated the system as it was before modifications were made in response to operational problems and corrective maintenance early in the plant's life. The RCM study verified the appropriateness of major elements of the current PM programme. It developed desirable candidate condition directed tasks as replacements for existing time directed tasks and verified the need for modifications which the plant had identified by other means.

The third pilot application was conducted on the auxiliary feedwater system (AFWS) at Southern California Edison's (SCE) San Onofre Station. Unlike the normally operating systems that had been studied in the first two applications, the standby AFWS has functional redundancy, constraints on allowable outage time, infrequent operation, and frequent testing. Also, system failures are often not

obvious until a demand for the system occurs. Therefore, this study offered a further test of the applicability of the RCM for a nuclear plant. The study recommended a net decrease in PM effort on the system with many PM tasks to be deleted, reduced in scope or changed from time directed to condition directed.

2.3.3. Large multi system nuclear plant RCM demonstrations

As the next step in developing RCM for potential wide use in the nuclear industry, EPRI selected two host utilities for large scale RCM demonstrations. One demonstration was conducted at the Ginna nuclear power station. The other

demonstration was conducted at San Onofre nuclear generating station, Units 2 and 3.

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A principal objective of these projects was to implement RCM on a large number of plant systems at each plant as part of a PM evaluation programme. The projects showed both the cost-effectiveness and the feasibility of the integration of RCM into the operating environment and organization of each power plant. They demonstrated acceptance of the RCM programme by utility personnel. These objectives were met concurrently with the utilities' own objectives, such as (1) quantifiable reductions in maintenance cost; (2) realignment of maintenance resources to improve overall plant availability and safety; (3) producing a more favourable PM-to-CM cost ratio; (4) optimization of technical specification testing requirements; and (5) providing a partial basis for plant life extension and license renewal.

Both utilities viewed their RCM projects as one element of a larger

maintenance improvement programme without clear boundaries. At Rochester Gas and Electricity Corporation's Ginna Plant, the following additional activities were underway:

restructuring of the maintenance organization;

upgrading of the work control system;

upgrading of procedures;

development of a maintenance information system;

At SCE the plant had the following additional activities underway:

PM audit task force for all systems;

of technical optimization specifications;

maintenance basis documentation.

At both utilities RCM team members participated in the total maintenance improvement effort, and RCM became the maintenance philosophy that bound these diverse activities together.

Both the Ginna and the San Onofre demonstrations began in the Spring of 1988. All of the analyses on 12 to 20 systems were complete at each plant within two years.

Significant steps in each demonstration included: (1) selection and

prioritization of systems for RCM evaluation; (2) performance of the RCM analysis steps on the selected systems; (3) evaluation of the RCM recommendations by a multi disciplinary team or task force; (4) implementation of the RCM recommendations;

(5) establishment of a system to rank and verify the RCM benefits; and (6)

establishment of procedures to update the RCM bases and recommendations with time.

Differences in the demonstrations were partly imposed by very real

differences in the two utilities and their respective plants. Ginna is run by a small utility, and is a small, single unit plant with many operating years of experience. The unit has had high availability and reliability. Its PM programme was less formal and procedural than for new plants Ginna is run by a small utility, and is a small, single unit plant with many operating years of experience. The unit has had high availability and reliability. Its PM programme was less formal and procedural than for new

plants. Its utility was interested in maintaining this good performance in the second half of the plant's license period and in laying the basis for a possible license renewal.

San Onofre is a large utility and Units 2 and 3 are large, relatively new units with scope for improvements in availability and reliability. The utility was interested in justifying optimization of their extensive PM programme and technical specification testing requirements.

The demonstration projects at San Onofre and Ginna are now complete.

Most of the objectives have been met, and the lessons learned are now available for the benefit of other utilities undertaking RCM activities.