Reliability Driven Maintenance--Closing the CMMS "Value Gap"? Part One: Trends and Definition
Written By: Predrag Jakovljevic
Published On: January 17 2005
The Maintenance Approach Evolution
Although enterprise asset management (EAM) and computerized maintenance management systems (CMMS) software continue to grab headlines as a realistic way to reduce expenses and increase revenues, the growing pressure for improving customer responsiveness and profits has lately pretty much changed the traditional role of asset management. Namely, the metric of plant maintenance should now be in the ability of the plant to meet the strategic goals of the company beyond customarily expected cost savings, such as improved plant output, performance predictability, product quality, customer service, safety, environmental control, etc. For one, an effective preventive maintenance program can improve equipment's required utilization and availability, enabling production schedules to be achieved, especially when an exorbitantly expensive equipment replacement is a no option during depressed economic times. Extending into the customer base, this applies as much to improved standards of customer service as it does to product quality.
The importance of ascertaining the proper maintenance work as a result of a still ongoing plant maintenance approach evolution could even be deducted from analyzing several APICS Dictionary (the 11th Edition) definitions. Namely, the 1960s and 1970s were characterized by the "Fix it when broken" approach of merely reacting to unplanned and unwanted breakdowns. Associated with breakdowns is also a bad word, downtime, which is the time when a resource is scheduled for operation but is not producing for reasons such as maintenance, repair, and overhaul (MRO), or setup. In the case of a repair, this typically consists of lost times to report or notice fault, assess fault, gain physical access to the equipment, study reference manuals (if something like that exists at all), obtain spare parts, obtain necessary tools (which also might not exist at all as a standard offering and will have to be invented or made), perform actual repair work (which is often only half of the entire downtime cycle), sign-off the work order, and accommodate certain miscellaneous time items due to the interruption.
Along similar lines of unplanned maintenance activities (given that "strategy" could hardly be an applicable word for anything that is of a reactive nature) are the following
- breakdown maintenance—a curative maintenance that occurs when equipment fails and must be repaired on an emergency or priority basis;
- corrective maintenance—the maintenance required to restore an item to a satisfactory condition;
- remedial maintenance—unscheduled maintenance performed to return a product or process to a specified performance level after a failure or malfunction.
Yet, the real total costs of reactive maintenance to breakdowns would emanate from lost production, poor product quality, lost sales, poor safety record, late deliveries, increased work in progress (WIP), shortened technical lifetime of equipment, etc.
Thus, the 1980s and 1990s have evolved into the "Fix it efficiently" approach of planned maintenance, scheduled overhauls, and utilizing CMMS for improved efficiency and control. Associated with this approach is scheduled downtime, which is a planned shutdown of equipment or a plant to perform maintenance (or to adjust to softening demand). To that end, the concept of CMMS was introduced, and these systems have since been used to bring efficiency to maintenance. For more info on the capabilities of CMMS, see CMMS: A Tutorial. A central concept of CMMS is preventive maintenance, which are the activities, including adjustments, replacements, and basic cleanliness that supposedly forestall machine breakdowns. The purpose is to ensure that production quality is maintained and that delivery schedules are met. In addition, a machine that is well cared for will presumably last longer and cause fewer problems.
This is Part One of a two-part note.
Part two will present examples and make user recommendations.
The Preventive Maintenance Approach
Using time-based approaches, CMMS modules use the above concepts of preventive maintenance as a strategy to avoid unplanned downtime, and they suggest that plants do a maintenance activity at specified intervals—regardless of whether or not they really ought to do this work. The unit of time can thereby be measured in days, weeks, or months, or in a number of work cycles of the asset. For example, a certain maintenance task is triggered every six weeks or after every one million pieces are produced.
CMMS software also characteristically recommends what should be done to the asset based upon the recommendation of the equipment manufacturer (e.g., the suggested activities at a certain maintenance time interval or at certain milestones), although the manufacturer cannot always know the real conditions under which its equipment is going to operate within various working environments. Preventive maintenance has nonetheless proven that it can lower unplanned downtime. But, applying the principles of lean manufacturing tells us that any unnecessary maintenance is a waste. That is to say, just like inventory one does not need at a certain time is considered a waste, maintenance tasks done before then they are truly required also constitute a waste.
When preventive maintenance tells us it is the time to perform a maintenance routine, the $64,000 question is, could we have waited or eliminated this routine without a negative impact on the asset's ability to meet the business objectives? We cannot know what would have happened for sure after the preventive maintenance routine was performed. Yet, since the preventive maintenance trigger points are set to minimize or eliminate unplanned downtime, they are conservative by nature, which means that the majority of preventive maintenance efforts happen "too soon", creating an unnecessary excess maintenance expense and downtime, or simply a maintenance waste. Therefore, preventive maintenance may collide with the lean principles. For more related information, see Lean Asset Management—Is Preventive Maintenance Anti-Lean?
Moreover, various studies have proven that less than 20 percent of all failures are time-based. Indeed, failure analysis reveals how assets fail and why, and the reason for failure is most often not time-related, since for most assets there are numerous ways how they can fail, one being the "abuse" of the equipment even if unintentional (i.e., not knowing the ideal working regimen for the asset). These studies also find that a large percent of the scheduled maintenance work done was not thus required—it was consequently the wrong work, which has only resulted with unneeded downtime (i.e., losses).
Thus, the pressure for customer responsiveness and profits has yet again changed the role of asset management in the 2000s. As mentioned earlier on, the metric of plant maintenance should now be in the ability of the plant to meet the strategic goals of the company beyond mere cost savings, such as improved plant output, predictability, quality, customer service, safety, environmental control, etc. Asset-intensive industries are realizing they need more than their traditional CMMS concepts in order to gain a competitive advantage. To be fair, CMMS (and EAM of late) products have helped many companies to work efficiently, but if one is not doing the right work, it is of little avail. The thought-leading approach nowadays is to "work effectively" by embracing the benefits of concepts like reliability assessment, business risk prioritization, reliability centered maintenance (RCM), condition monitoring, and so on.
A focus on reliability driven maintenance might improve equipment reliability and close the value gap of maintenance effectiveness versus maintenance efficiency. In other words, today's leading organizations are working more effectively by doing only the right, absolutely necessary work, given the above indications that often more than half of the typically performed tasks during time-based scheduled maintenance are not really needed.
Reliability Driven Maintenance
Conversely, reliability driven maintenance (RDM) focuses rather on understanding the "asset health" to determine what maintenance work should occur and when something should be done. It enables preemptive intervention before failure occurs, whereby failure would mean that equipment is not delivering required performance regardless of whether it is actually broken down or not. To reduce waste, assets must perform as expected and when expected. This means that failure must be redefined to mean an asset is unable to meet business objectives, such as running at the expected rate, producing product within the expected quality standards, and being ready when it is needed for production. If an asset does not meet these objectives, it has failed. Reliability eliminates waste, since machines that are reliable produce less scrap and rather a product that is within specification, thus eliminating the cause of defect correction, whereby equipment is ready to run as soon as the demand is presented.
Intricate work identification methodologies like reliability centered maintenance (RCM) and failure modes and effects analysis (FMEA) are the foundation of reliability driven maintenance, enabling users to understand when and why assets fail, and determining the warning signs that failure is about to occur and what can be done to prevent the failure.
Zooming on the concept of RCM, which has been explored since the 1960s, it is one increasingly used methodology nowadays for understanding an asset's potential for failure. It is a process for defining possibly a cost-effective schedule for each asset necessary to maintain reliable performance. In order to establish this schedule, reasonable expectations of performance, limitations, and priorities must be established for the physical asset. Instead of focusing on preventing an asset from failing at all costs, RCM concentrates on ensuring its continued reliability by shifting the maintenance paradigm from one of prevention to one of prediction, so that appropriate action can be taken early on.
APICS Dictionary defines predictive maintenance as a type of preventive maintenance based on nondestructive testing and statistical analysis, used to predict when required maintenance should be scheduled. Predictive maintenance typically leverages indirect maintenance activities (e.g., condition monitoring), whereas preventive maintenance tends to focus on direct activities (e.g., cleaning, lubrication, replacement, repairs, etc.).
The RCM concept is based upon determining how assets fail, why each failure type occurs, and the symptoms that indicate potential failure. Understanding failures can also reveal the right work to be performed based upon the specific symptoms. By monitoring the asset with this view, users can detect the symptoms of failure and react to these symptoms (e.g., a low pressure of the pump) with the right work (e.g., check either for a blockage, damaged impeller, or leaking seal). The result, as found in the airline industry, are assets that are far less likely to fail and that require far lower maintenance expenditures.
Furthermore, creating a RCM environment is not a one-time process. Rather, it is a continuous, evolving, and ever improving process of analysis. Still, desired RCM functionality should entail the ability to
- Select critical equipment;
- Analyze failure patterns;
- Determine consequences of failure analysis;
- Perform selection of preventive action;
- Perform detailed analysis of the cost of prevention (calculated based on the costs of the service, including labor and materials, over the same period of time as the mean time between failures [MTBF]) versus the cost of failure (calculated based on the downtime-related costs multiplied by the downtime plus any additional repair cost);
- Do activation of approved action; and
- Perform automatic analysis of work order feedback.
From this thorough analysis, necessary maintenance task are then defined, with joint responsibility of maintenance and operations departments. Operationally, users start to monitor the health of the asset through sensors and process control tools (e.g., distributed control systems [DCS], programmable logic controllers [PLC], data historians, supervisory control and data acquisition (SCADA) systems, etc.), inspections (e.g., visual inspections, maintenance rounds, operator rounds, etc.), predictive tools (e.g., lubrication analysis, vibration analysis, infrared thermography, motor circuit analysis, non-destructive testing, etc.) and then compare current asset health to both history and a set of rules defined for the asset based on the RCM failure analysis of results. Asset health (not time) then determines the "when" and the "what" of maintenance (i.e., recommended tasks). This, in turn, elevates the strategic significance of maintenance by linking it to business goals, and enterprises using reliability driven maintenance strategies state that the approach gives them a better answer for both the when and what issues of maintenance.
The market has consequently begun to see the rise of software vendors with extensive maintenance management expertise who are offering both services and software products which make a proactive, condition-based approach to maintenance practical and a necessity today. Some of them, Intentia and IFS were depicted in more detail in EAM Versus CMMS: What's Right for Your Company?
These reliability centered products and services are not a replacement for existing CMMS/EAM implementations. Namely, while traditional CMMS is the way to insure an efficient maintenance operation, RDM is a necessary upfront step to recommend the when and what of maintenance, which is then executed by CMMS. In other words, within such a combination of CMMS and RDM, CMMS addresses the efficiency of maintenance and RCM the effectiveness of maintenance.
This concludes Part One of a two-part note.
Part two will present examples and make user recommendations.
About the Authors
Olin Thompson is a principal of Process ERP Partners. He has over twenty-five years experience as an executive in the software industry. Thompson has been called "the Father of Process ERP." He is a frequent author and an award-winning speaker on topics of gaining value from ERP, SCP, e-commerce and the impact of technology on industry.
|Predrag Jakovljevic is a research director with Technology Evaluation Centers, Inc. (TEC), with a focus on the enterprise applications market. He has over fifteen years of manufacturing industry experience, including several years as a power user of IT/ERP, as well as being a consultant/implementer and market analyst. He holds a bachelor's degree in mechanical engineering from the University of Belgrade, Yugoslavia, and he has also been certified in production and inventory management (CPIM) and in integrated resources management (CIRM) by APICS.