Reliability HotWire

Reliability HotWire

Issue 126, August 2011

Reliability Basics

Reliability Centered Maintenance (RCM) - A Cost Saving Measure

Joseph M. Michalek

"Why should I do RCM? Why should I spend the time and money to buy software, assemble teams, do research, conduct meetings and chase action plans just to develop a maintenance plan? I’ve got an operation to run and doing all that will just eat up my time! I don't have time for it. All I have to do is to see what fails and fix it!"

That statement could have easily come from a maintenance manager of any one of many manufacturing or process-oriented businesses anywhere in the world. Running an operation with equipment producing or moving product is often hectic and manned by a hands-on workforce that prefers the action of today’s operations to the monotony of a conference room where you think through possibilities of what might happen and decide what to do about it.

Well the answer is simple: it reduces the cost of running business and provides opportunities for a much more efficient operation with improved productivity. If we can understand the details of what goes wrong, how it goes wrong, how likely it is, how bad it is, and what it costs the business, we are more likely to make better decisions to prevent the causes, preemptively perform the repair and/or minimize the consequences of failure. A smooth running operation offers the opportunity for less downtime, higher availability, more productivity and more production with less resource demand. RCM analysis provides a structured framework to do just that. This article discusses the rationale for performing RCM and how it is a path to cost savings for production operations.

So let’s consider what it takes to optimize a maintenance plan using RCM. The process is straightforward and similar to a failure modes and effects analysis (FMEA). It includes:

  • Equipment selection.

  • Identification of functions.

  • Identification of functional failures.

  • Identification of potential effects.

  • Identification of failure modes/causes.

  • Determination of required maintenance tasks that address the failure modes/causes.

Very much like an FMEA, the process counts on cross-disciplined teams to ensure that the equipment and process requirements are understood, and that issues such as how the requirements are (or are not) being met are addressed. Process reliability, including process failures, process issues and equipment issues are understood. This includes not only what breaks and how often but also the root cause of the failures, for it is in addressing the root causes with a strategic maintenance plan that a breakthrough in the performance of the equipment can be achieved.

The primary focus of RCM is to achieve a high level of understanding of the failure modes/causes, the likelihood of occurrence and the related effects; then to define a maintenance plan that prevents or proactively addresses the potential causes of failure in such a way that the overall cost of doing business is reduced. The following are considerations in the cost of failure for the equipment and maintenance part of doing business:

  • Cost of downtime is the cost of the equipment not running when scheduled. This includes loss of sales, production labor hours (scheduled production labor waiting for the repair to be made), special or express shipment, unscheduled overtime and idle asset hours. Wait time includes time for a work crew to respond to the failure, time to investigate the failure and time to wait for parts and/or equipment necessary to make the repair. Loss of sales and productive labor wait time are frequently the highest costs associated with equipment failure. The actual cost will depend on product demand and could range from several hundred dollars per hour to tens of thousands of dollars per minute. The more frequent and debilitating the failure, the more cost incurred.

  • Cost of maintenance labor is the cost of fixing the equipment (Labor Rate x Repair Personnel x Total Time to Fix). This includes wait time (time for the work crew to wait for parts, equipment, other members of the work crew, etc.), time to stage the repair, time to make the repair, verification time and time to return the equipment to production status.

  • Cost of parts is the cost of the repair or replacement parts required to return the system to service. It includes the basic cost of the part, any delay due to unavailability, express shipment, cost of inventory and cost of obsolescence (if any).

With all these costs stacking up against the cost of production, it is easy to see how quickly they can get out of control and result in a significant impediment against profitability. RCM can help identify different maintenance strategies that are available to minimize the cost of keeping the equipment running, optimize throughput and equipment availability, and potentially extend the life cycle of the equipment. The maintenance strategies are described next.

  • Preventive maintenance (PM) attempts to identify and address impending failures before they occur in order to do the repair at the least costly time of the production process. The repair may be scheduled during times when the equipment is normally not running and is available for maintenance activity, where the costs are not associated with downtime. This strategy also provides the opportunity to minimize the labor costs associated with the repair because work is scheduled and work activity can be staged in advance.

  • Predictive maintenance is an on condition activity that utilizes inspection techniques to identify failure modes or causes of failure before they occur. It allows corrective measures to be scheduled during planned downtime. There are various approaches to performing a predictive maintenance, from visual inspection to the use of very sophisticated equipment to detect evidence of impending failure, such as levels of heat, vibration, noise and wear. The techniques used will vary depending on the equipment, the failing part and equipment availability to do the inspection.

  • Inspection maintenance is a work effort that uses inspection techniques to find hidden failures. This is normally a scheduled procedure that occurs during non-production hours and drives immediate repair when a failure is detected.

  • Corrective maintenance is an approach that is frequently reserved for failure modes or causes that have a low cost of failure and/or for failures for which no predictive or preventive techniques have been identified and a run to failure maintenance strategy is taken. Corrective maintenance also applies to unanticipated failures that occur to components and systems that have preventive and predictive maintenance plans.

  • The following figure shows how ReliaSoft's RCM++ software can capture the details of the cost of failure, helping you to create a corrective maintenance strategy plan.

In addition to forecasting failures and taking preemptive repair actions outside of regular production hours, RCM++ allows you to assemble maintenance packages to reduce the cost of maintenance actions. Maintenance packaging allows the RCM team to not only forecast when and what maintenance actions need to be done, but also provides the opportunity to group activities so that multiple maintenance activities can occur together. Maintenance crews can provide maintenance services based on timing developed from life data and maintenance crew schedules, and therefore machine downtime schedules can be optimized. This can significantly reduce the cost of keeping the equipment running when needed. The screenshot below shows how maintenance packages are addressed in the RCM++ software.

Conclusion

RCM is a technique that pulls together the information necessary to understand how a piece of equipment performs and what can be done to improve uptime while minimizing cost and effort. It is clearly worth the effort for continuous operation and on-demand equipment. Its best application is when failures and failure rates are understood and a cross-disciplined team performs the analysis vigorously and develops the maintenance plans by the book.

References

Moubray, J., Reliability-Centered Maintenance, New York City, NY: Industrial Press, Inc., 1997.

Stanley Nowlan, F. and Heap, H.F., "Reliability-Centered Maintenance," issued in December, 1978.

SAE JA1012, "A Guide to the Reliability-Centered Maintenance (RCM) Standard," issued in January 2002.

Society of Automotive Engineers and National Center for Manufacturing Sciences, M-110.2, Reliability and Maintainability Guideline for Manufacturing Machinery and Equipment, August 1999.

Joseph M. Michalek

Joe Michalek is a consultant for ReliaSoft Corporation as well as an instructor in the areas of FMEA, manufacturing reliability engineering, Reliability Centered Maintenance and manufacturing management disciplines. He has 20 years experience in the manufacturing quality disciplines and 13 years experience in reliability and manufacturing reliability engineering. He has done extensive work to streamline and improve the effectiveness of PFMEA and Machinery FMEA within General Motors. In addition, his work with the key characteristic designation system (KCDS) has resulted in a global common process for the development and implementation of key characteristics and process control plans for GM. His previous assignment with General Motors was Global Manufacturing Cost Center Manager who was responsible to define, develop, and manage a global activity to act as primary interface between Manufacturing Engineering and Finance. Mr. Michalek was a co-chair in the development of the (SAE) J1739 for Design/Process/Machinery FMEA and participated in the development of the SAE M-110.2 Reliability and Maintainability Guideline for Manufacturing Machinery and Equipment. Mr. Michalek holds a B.S. in Mechanical Engineering from General Motors Institute (now Kettering University).

To learn more about the ReliaSoft's consulting services, visit: http://www.ReliaSoft.com/consulting/