Is your RCM is a justified financial success and can you prove it reduced failures? You need to validate your program because RCM programs are expensive and reduced costs must pay for the program. Here’s how to take objective evidence and show that reliability centered maintenance (RCM) programs reduce failures and provide cost reductions. RCM is a mostly a qualitative process to identify failure modes and institute good maintenance practices to prevent, delay, or mitigate the failure occurrence.
Management usually has trouble buying into the RCM process because it takes big up-front expenditures before you see payback. The improvements are difficult to prove before you begin the process. The living RCM program does not fit the typical “project of the month”. A few companies proceed so ponderously toward RCM; the sponsoring manager never sees a big payback in their typical 2-3 year tour of duty.
Start the RCM validation process by collecting your failure data over some reasonable time period. Plot cumulative failures on the Y-axis and cumulative time on the X-axis using log-log plots and you’ll frequently see straight trend lines. After implementation of an RCM program look for a cusp on the trend line of cumulative failures versus cumulative time to show a gradual reduction in failures as described in Figure 1 which is a Crow/AMSAA plot know as a reliability growth curve.
Where would you find failure data? Electrical generating plants carefully maintain failure data according to the North American Electric Reliability Council (NERC), Generating Availability Data System (GADS) and Data Reporting Instructions. The field of reliability is concerned with identifying, predicting, and preventing failures. The field of electrical power generation has a stated goal of generating power without failure. Look for other examples of failure data in your own maintenance records as described in Predict Future Failures From Your Maintenance Records.
Crow/AMSAA methodology is useful for mixed failure modes, which means the cause for the failures can be by many different reasons. When improvements have occurred, a cusp will appear on the trend line signifying failures are coming more slowly when the trend line has flatter slope (beta line slopes less than 1). Likewise a cusp forms if the failures are coming more quickly (deterioration to a less favorable condition with beta line slopes greater than 1).
Crow/AMSAA plots of stable processes give straight lines when plotted on log-log paper. The straight line can be regressed using simple curve fit techniques to forecast future failures. The slope (the beta value from the regression) of the Crow/AMSAA trend line is an important statistic. The Crow/AMSAA slope (beta) tells if failures are increasing (beta > 1), decreasing (beta < 1), or floundering along with no deterioration or no improvement (beta @ 1). Patrick O’Connor reports in Practical Reliability Engineering that beta slopes less than 0.4 show dedicated improvement programs (O’Connor literally reports an alpha value where a = 1- b).
If the RCM program has been successful and failures are coming more slowly you can collect/estimate the costs for implementing/sustaining the RCM program and by assuming the cost for each avoided failure, you have the savings. Download and use the Excel spreadsheet for making net present value calculations (NPV) and internal rate of return (IRR). The key for selling RCM programs is to demonstrate financial success.
Suggested reading list on the subject of
reliability centered maintenance:
Reliability-centered Maintenance, 3rd edition by John Moubray/Paul Lanthier, Industrial Press, NY, 2012
Reliability-Centered Maintenance, by Anthony M. Smith, McGraw-Hill, NY, 1993, ISBN 075067461X
Operations and Maintenance (O&M) Best Practices Guide for USA Federal Facilities, 2002
NASA Reliability Centered Maintenance Guide For Facilities and Collateral Equipment, February 2000
Reliability Centered Maintenance (RCM), US Naval Air Systems Command
Articles on Equipment Maintenance Strategies and Reliability Centered Maintenance (RCM), Sandy Dunn’s Plant Maintenance Resource Center in Australia
Where can you learn more about Crow/AMSAA plots:
1. The New Weibull Handbook by Dr. Robert B. Abernethy
2. WinSMITH Visual software by Fulton Findings for making reliability growth plots
3. Crow/AMSAA Reliability Growth Plots Problem Of The Month
4. MIL-HDBK-189 Reliability Growth Management
5. TR-652 AMSAA Reliability Growth Guide available for download from the November ‘02 Problem Of The Month
You can download a PDF copy of this Problem Of The Month by clicking here.