By Gary Yezefski
Preventative Maintenance (PM) plans are like getting your car oil changed. You know you should do it every 5000 miles, but owners continually push if things seem to be running okay to perhaps every 7500 miles instead. PM plans were originally developed to focus more on non-safety related components and of course are a hassle and cost money. However, you know, in the long run oil changes can save you money and are worth the effort.
PMs are justifiably conservative to provide assurance that plant safety requirements are adequately fulfilled. Time-prescriptive inspections and teardowns have been augmented by performance-based allowances and the use of predictive actions – not to mention put off due to lack of manpower and budget. These programs lack flexibility to be modified as needed to serve as a “living” plan for continual improvement in Emergency Diesel Generators (EDG) availability and reliability.
A key part of diesel generator reliability and availability improvement should be a periodic review of the recommended maintenance activities to verify that they are still applicable. This should have occurred over time; however, it is resource intensive and may not have been pursued due to limited staff availability for such an effort.
The Future of PM
The future of PM is to examine past and current findings for degradation, out of tolerance, and failure in order to determine which PMs may be justifiably modified in frequency and activity description — ultimately to save the Owner time and money.
A properly optimized plan must draw upon features of several maintenance theories. The licensee’s condition monitoring program must reflect the tradeoff of EDG reliability between preventative maintenance and EDG failure (and subsequent corrective maintenance). Therefore, it is important that the EDG maintenance program has provisions for periodically reviewing and updating the condition monitoring performed on the diesel generators.
Regular program reviews (over several years) will consider the physical inspection data obtained by the owner and will provide the basis for continued modifications of the program as needed to serve as a “living” plan for continual improvement in EDG availability and reliability.
A living program should continually measure the effectiveness of a maintenance plan. It is necessary to verify through experience or physical part inspection that data monitoring/trending results accurately reflect actual engine conditions. Once confidence is obtained that the data analysis results are representative of what is seen during actual inspections, the physical inspection requirements should be eliminated.
Proven Results: Case Study
To help you visualize the savings – let us review a PM plan conducted on emergency diesel generators (EDG) at a nuclear power plant to see how we find potential savings.
At this utility we looked at system preventative work orders over 12 to 18 years. The review focused on only those PMs with a frequency of three years and included historical performance over the last 18 years.
The results? We determined that approximately 80 percent of the 47+ PM’s per EDG (150 total) within the scope of the review were justifiably qualified to have the frequency extended. This translates to an initial savings of $225,280 and estimated future savings of $450,000 approximately every six years.
Calculate Your Savings
DP has created a formula that helps forecast savings from such a PM review. You can use it to look at potential PM optimization savings at your station. Follow these steps:
- Gather your numbers. The site determines the scope of the PM review: the number of PM’s and the specific frequency to be reviewed.
- Determine your scope. We have determined, based upon a past study experience, that 80 percent (0.8) may be representative of the number of PMs that can be extended.
Calculate your savings. Site costs for performing a PM vary. Direct costs include the worker hours that it takes to perform the physical work. Determine your work hour rate or use $100/worker-hr. The time necessary to perform each PM is typically 12-15 worker hours (determined from actual performance data recovered from completed studies), so we calculate the potential savings range with a low value and a high value.
Why double the savings? Based on past studies, we know that non-documented savings such as warehouse stock price, planner time, scheduler time, work group review and brief time, operation clearance tag application and removal time, post work supervisor review time, work package closure time, and trending review time are not included, and can more than double the savings calculated with worker hours.
Potential Savings Become Reality
Now that you’ve calculated your potential savings, it’s time to make them a reality. Share your estimate with your station team. Smarter handling of PMs can result in both short term and long-term savings and more efficient plant operations. If these savings fit within your future goals, it is time to talk with GSE DP Engineering. Learn more about our innovative – and money-saving – services here.
- SAE Technical Paper 941810, 1994
- 10CFR-50.65, Requirements for monitoring the effectiveness of maintenance at nuclear power plants
- INPO AP-913, Equipment Reliability Process Description, rev 1, November 2001
- EPRI Report 1016678, December 2008, Nuclear Maintenance Applications Center: Emergency Diesel Generator Condition-Based Maintenance