The existing EDF maintenance programme takes into account the feedback experiences from its standardized units.
The motivations of EDF to evaluate the benefits of the RCM approach are the following:
PM/CM ratio improvement;
systematic and structured process;
cost optimization;
qualitative and quantitative use of maintenance history;
visibility and traceability of actions and decisions.
To evaluate the benefits of the RCM approach, as described in Section 3.1, the CVCS was selected as a pilot study for the following reason:
The CVCS is operating continuously.
The CVCS is safety and availability related.
The CVCS has a large number of various equipment including valves, pumps, heat exchanges, and sensors.
Several parts of the CVCS analysis will be used again for other systems.
The pilot study of the CVCS started at the beginning of 1990. The CVCS was decomposed into eight subsystems:
volume control tank;
the charging pump;
the charging line;
injection of the Seal no. 1 of the primary pumps;
let down line (demineralization excluded);
outlet water from Seal no. 2 of the primary pumps;
water supply for the RHR.
For each subsystem, the functions important for safety, production and maintenance were identified, taking into account in particular the results of the probabilistic safety analysis of the 900 MW units.
By using FMEA, the critical functional failure list was completed by July 1990. The final list ranked by the experts from the generation division will be completed by the end of 1990.
The functional partitioning of the critical items of equipment will be
completed by the end of 1990 after their validation. Taking into account the various feedback experience (event database, reliability database, Blayais unit maintenance history, and special reports), it was possible to identify the equipment failure rate, the component failure rate, the modes and the causes of the failures of the component and the degradation modes.
This task requires the manual screening of several hundred documents related to the maintenance history. The analysis of the significant failures of each critical equipment item is done by FMECA pump gear reducer.
The maintenance task selection, using logic tree analysis will be completed also by the end of 1990. Figure 6-1 provides a draft of a maintenance task selection sheet for a CVCS pump gear reducer.
The final study for the CVCS was completed during 1991.
A detailed project organization was set to perform the study and is described in Fig. 6-2.
Once the final maintenance tasks provided by the RCM have been validated by experts and compared with the existing maintenance programme, the final decision will be taken by mid-1991 on whether to undertake the analysis of other systems.
An implementation of living programme would induce modifications of the national maintenance programme and, as appropriate, restructuring of the
maintenance history inside the plant information management system to measure the effectiveness of the RCM. In addition, according to the EDF experience, the benefits of RCM would be tangible only after a three year period of experimentation at the plant.
MAINTENANCE TASK SELECTION SHEET Equipment : CVCS Pump Gear reducer
Lubrication applicable effective and economical ?
Y effective and economical ?
Y Cause : Wearing of ball bearing
Yes : Bearing lubrication
Yes : Vibration measurement with a data collector
Yes : Visual inspection
No
Yes : Vibration measurement with a data collector Selected task
Bear lubrication and vibration measurement
Interval
Fig. 6-1. Draft of a maintenance task selection sheet.
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SYSTEM ANALYSIS Safety, reliability analyst
System engineer
RCM STEERING COMMITEE - Maintenance Department manager
(Nuclear and fossil generation Division) - Managers of 3 specialized departments
(R & D Division)
RCM Project Manager
EQUIPMENT ANALYSIS AND TASK SELECTION
Equipment analyst
Equipment experts Pump Valve I&C
FEED BACK ANALYSIS Statistician and analyst
Mechanical engineer
Fig. 6-2. RCM project organization.
6.2. APPLICATIONS OF RCM BY SEVERAL UTILITIES IN THE USA
Immediately following the publication of the RCM pilot study reports for the single system applications of RCM at Turkey Point Station, the McGuire Station and San Onofre Nuclear Generating Station, several utilities in the USA undertook pilot studies of their own.
At the time of this writing, approximately 12 nuclear plants have performed pilot studies on one or several plant systems for the purpose of evaluating the RCM method or for the purpose of addressing a specific maintenance concern for those systems. These applications are generally useful RCM studies, but they do not indicate the commitment on the part of these utilities to an RCM programme or to an RCM philosophy of maintenance.
Some of the utilities in this category are now developing more extensive RCM programmes as a result of their limited studies.
In addition, approximately six nuclear plants are committed to performing RCM analyses on a large number of plant systems. These systems were selected on the basis of their importance to plant operations and safety. The number of systems varies from 8 to more than 20. Each of these plants has implemented or plans to implement the RCM recommendations. Several of these plants have definite plans for an RCM living programme. These plants can be considered to have an RCM programme in place.
Two of the plants in this category are the EPRI demonstration plants - Ginna and San Onofre. Their RCM programmes are clearly documented in their respective EPRI published reports.
Most recently, several utilities have chosen to institute full plant PM
Programme Improvement Projects (PMPIP) with RCM as an important element of the PM evaluations. These projects differ in principle from the RCM programme described, because they encompass all significant plant systems and major
components.
In most cases, the projects take a hierarchical approach to PM evaluation.
That is, detailed RCM analysis is planned for the most significant systems (typically 20 to 30), a reduced scope RCM evaluation is planned for less significant systems, and a traditional PM evaluation using only RCM insights is planned for the least functionally significant systems or component types. These RCM based projects point to an RCM based maintenance philosophy that will influence all activities in the maintenance programme.
Indications are that PMPIP projects are under consideration by a growing number of utilities in the USA at this time.
6.3. THE RCM PROGRAMME OF EPRI
The leadership role played by EPRI has already been referred to in the discussion of the three pilot studies and the two large scale demonstration projects.
In addition, EPRI has sponsored the EPRI RCM Users Group (ERUG), an informal group of EPRI utility members who regularly meet for the duration of the large scale demonstration projects to exchange information on RCM technology and to help steer the research efforts of EPRI in the RCM area. This organization was influential in the transfer of RCM technology to a large group of utilities.
In response to the needs of the ERUG members, EPRI has produced several other RCM related products and activities. A database of information from utility sponsored RCM system studies has been assembled by EPRI for use by other utilities to assist in their own RCM studies or to glean RCM insights for limited scope studies.
EPRI has also developed a software specification for a microcomputer workstation to assist utilities in performing RCM analysis workshops, at which about 100 utility personnel have received training in the RCM analysis method.
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7. STATUS OF RCM TECHNOLOGY