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Defining Maintenance Strategies for Critical Equipment With Reliability-Centered Maintenance (RCM)
Defining Maintenance Strategies for Critical Equipment With Reliability-Centered Maintenance (RCM)
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This chapter is included to expose the planner/scheduler to the concept of reliabilitycentered maintenance (RCM). Some professionals believe that the so-called classical RCM has been made much more complicated than it needs to be. Nonetheless, RCM was first introduced in the field of commercial aviation. It made its way to the nuclear industry in the mid-1980s, then spread to other organizations. In all, it is been estimated that more than 60% of all RCM programs initiated have failed to be successfully implemented. According to Neil Bloom (2005) in his book Reliability Centered Maintenance— Implementation Made Simple, RCM became overly complicated in its transfer from the airlines and history. Also, it is his belief that the successful application of the process is inversely proportional to the complexity it has acquired. Bloom also stated that some consultants employ an elixir of obfuscation to allow them sole possession of understanding the process, and hence a continued income stream. Bloom (2005) clearly stated that RCM is not a preventive maintenance (PM) reduction program. It is a reliability program. RCM will indeed identify those unnecessary PMs that may become candidates for deletion. RCM is almost always described as a process of identifying critical components whose failure would result in an unwanted consequence to one’s facility. As a planner, your organization may have experienced some of the following reasons for lack of success or it may have a successful. You may be what is needed to get the RCM analysis on the right track. Many times, one or more of the following occurrances cause a lack of success: 1. Lost of in-house control 2. An incorrect mix of personnel performing the analysis 3. Unnecessary and costly administrative burdens 4. Fundamental RCM concepts are not understood 5. Confusion determining system functions 6. Confusion concerning system boundaries and interface 7. Divergent expectations 8. Confusion regarding convention 9. Misunderstanding hidden failures and redundancy 10. Misunderstanding run-to-failure 11. Inappropriate component classifications 12. Instruments were not included as part of the RCM analysis Reliable Maintenance Planning, Estimating, and Scheduling. http://dx.doi.org/10.1016/B978-0-12-397042-8.00009-7 Copyright © 2015 Elsevier Inc. All rights reserved.
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My goal for this chapter is for the planner/scheduler to understand item 4—the fundamental RCM concepts. Let us start with a definition and then a question. First, RCM can be defined as a process that is used to determine the maintenance requirements of any physical asset in its operating context. It provides a detailed process to answer this question: What must be done to ensure that any physical asset continues to do whatever its users want it to do in its present operating state? RCM can be defined as the seven key elements as shown in Figures 9.1–9.17.
Figure 9.1 The seven key elements of RCM.
Figure 9.2 The principles that define and characterize RCM.
Defining Maintenance Strategies for Critical Equipment With Reliability-Centered Maintenance
Figure 9.3 RCM is typically implemented in seven steps.
Figure 9.4 RCM is typically implemented in seven steps.
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Figure 9.5 Functions and performance standards.
Figure 9.6 Functional failures.
Defining Maintenance Strategies for Critical Equipment With Reliability-Centered Maintenance
Figure 9.7 Functional failures.
Figure 9.8 Failure modes.
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Figure 9.9 Failure effects.
Sub-System: EXAMPLE: FAILURE MODES AND EFFECTS ANALYSIS (FMEA) Exhaust System FUNCTIONAL FAILURE FAILURE MODE FAILURE EFFECT (Loss of Function) (Cause of Failure) What happens when it fails? 1. To channel all the A. Unable to channel gas 1. Silencer Silencer assembly collapses and falls to bottom of stack. Back at all. mountings pressure causes the turbine to surge violently and shut down hot turbine air corroded away. on high exhaust gas temperature. Downtime to replace silencer without restriction to a fixed point up to four weeks. 10m above the 1. Part of silencer Depending on the nature of blockage, exhaust temperature B. Gas flow resticted. roof of the turbine may rise to where it shuts down the turbine. Debris could falls off due to building. damage parts of the turbine. Downtime to repair silencer up to fatigue. four weeks. C. Fails to maintain the 1. Hole in flexible The joint is inside turbine hood, so leaking exhaust gases would gas. be extracted by the hood extraction system. Fire and gas joint from detection equipment inside hood is unlikely to detect an corrosion. exhaust gas leak, and temperatures are unlikely to rise enough to trigger the fire wire. A severe leak may cause gas demister to overheat, and may melt also melt control wires near the leak with upredictable effects. Pressure balance inside the hood are such that little or no gas is likely to escape from a small leak, so a small leak is unlikely to be detected by smell or hearing. Downtime to replace joint is 3 days. 2. Gasket in Gas escapes into turbine hood and ambient temperature rises. ducting Buliding ventilation system would expel gases through louvers improperly fitted. to atmosphere. So concentration of gases is unlikely to reach noxious levels. A small leak at this point would be audible. Downtime to repair up to 4 days. 3. Hole in upper bellows due to corrosion.
The upper bellows are outside the turbine building, so a leak here discharges to the atmosphere, Ambient noise levels may rise. Downtime to repair, a few days to several weeks.
2. To reduce exhaust 1. Silencer material Most of the material would be blown out, but some might fail to A. Noise level exceeds noise to ISO mesh retaining the bottom of the stack and obstruct the turbine outlet causing ISO Rating 30 at 50m. Rating 30 at 50m. corroded away. high EGT and possible turbine shutdown. Noise levels would rise gradually. Downtime to repair about 2 weeks.
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Figure 9.10 Failure modes and effects analysis (FMEA).
Defining Maintenance Strategies for Critical Equipment With Reliability-Centered Maintenance
System: 5MW Gas Turbine FUNCTION
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Figure 9.11 Failure consequences.
Figure 9.12 Evaluating consequences with an RCM decision diagram.
Defining Maintenance Strategies for Critical Equipment With Reliability-Centered Maintenance
Figure 9.13 Proactive maintenance.
Figure 9.14 The P–F Interval.
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Figure 9.15 Areas of the “bathtub curve ”
Figure 9.16 Common equipment failure patterns.
Defining Maintenance Strategies for Critical Equipment With Reliability-Centered Maintenance
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Figure 9.17 Default actions.
Further Reading Bloom, Neil B., 2005. Reliability Centered Maintenance; Implementation Made Simple. McGraw-Hill Companies Inc. Moubray, John, 1997. Reliability-centered Maintenance. Industrial Press. Smith, Anthony M., Hinchcliffe, Glenn, 2004. RCM-gateway to World Class Maintenance. Elsevier-Butterworth-Heinemann.
9
This chapter is included to expose the planner/scheduler to the concept of reliabilitycentered maintenance (RCM). Some professionals believe that the so-called classical RCM has been made much more complicated than it needs to be. Nonetheless, RCM was first introduced in the field of commercial aviation. It made its way to the nuclear industry in the mid-1980s, then spread to other organizations. In all, it is been estimated that more than 60% of all RCM programs initiated have failed to be successfully implemented. According to Neil Bloom (2005) in his book Reliability Centered Maintenance— Implementation Made Simple, RCM became overly complicated in its transfer from the airlines and history. Also, it is his belief that the successful application of the process is inversely proportional to the complexity it has acquired. Bloom also stated that some consultants employ an elixir of obfuscation to allow them sole possession of understanding the process, and hence a continued income stream. Bloom (2005) clearly stated that RCM is not a preventive maintenance (PM) reduction program. It is a reliability program. RCM will indeed identify those unnecessary PMs that may become candidates for deletion. RCM is almost always described as a process of identifying critical components whose failure would result in an unwanted consequence to one’s facility. As a planner, your organization may have experienced some of the following reasons for lack of success or it may have a successful. You may be what is needed to get the RCM analysis on the right track. Many times, one or more of the following occurrances cause a lack of success: 1. Lost of in-house control 2. An incorrect mix of personnel performing the analysis 3. Unnecessary and costly administrative burdens 4. Fundamental RCM concepts are not understood 5. Confusion determining system functions 6. Confusion concerning system boundaries and interface 7. Divergent expectations 8. Confusion regarding convention 9. Misunderstanding hidden failures and redundancy 10. Misunderstanding run-to-failure 11. Inappropriate component classifications 12. Instruments were not included as part of the RCM analysis Reliable Maintenance Planning, Estimating, and Scheduling. http://dx.doi.org/10.1016/B978-0-12-397042-8.00009-7 Copyright © 2015 Elsevier Inc. All rights reserved.
146
Reliable Maintenance Planning, Estimating, and Scheduling
My goal for this chapter is for the planner/scheduler to understand item 4—the fundamental RCM concepts. Let us start with a definition and then a question. First, RCM can be defined as a process that is used to determine the maintenance requirements of any physical asset in its operating context. It provides a detailed process to answer this question: What must be done to ensure that any physical asset continues to do whatever its users want it to do in its present operating state? RCM can be defined as the seven key elements as shown in Figures 9.1–9.17.
Figure 9.1 The seven key elements of RCM.
Figure 9.2 The principles that define and characterize RCM.
Defining Maintenance Strategies for Critical Equipment With Reliability-Centered Maintenance
Figure 9.3 RCM is typically implemented in seven steps.
Figure 9.4 RCM is typically implemented in seven steps.
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Reliable Maintenance Planning, Estimating, and Scheduling
Figure 9.5 Functions and performance standards.
Figure 9.6 Functional failures.
Defining Maintenance Strategies for Critical Equipment With Reliability-Centered Maintenance
Figure 9.7 Functional failures.
Figure 9.8 Failure modes.
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Reliable Maintenance Planning, Estimating, and Scheduling
Figure 9.9 Failure effects.
Sub-System: EXAMPLE: FAILURE MODES AND EFFECTS ANALYSIS (FMEA) Exhaust System FUNCTIONAL FAILURE FAILURE MODE FAILURE EFFECT (Loss of Function) (Cause of Failure) What happens when it fails? 1. To channel all the A. Unable to channel gas 1. Silencer Silencer assembly collapses and falls to bottom of stack. Back at all. mountings pressure causes the turbine to surge violently and shut down hot turbine air corroded away. on high exhaust gas temperature. Downtime to replace silencer without restriction to a fixed point up to four weeks. 10m above the 1. Part of silencer Depending on the nature of blockage, exhaust temperature B. Gas flow resticted. roof of the turbine may rise to where it shuts down the turbine. Debris could falls off due to building. damage parts of the turbine. Downtime to repair silencer up to fatigue. four weeks. C. Fails to maintain the 1. Hole in flexible The joint is inside turbine hood, so leaking exhaust gases would gas. be extracted by the hood extraction system. Fire and gas joint from detection equipment inside hood is unlikely to detect an corrosion. exhaust gas leak, and temperatures are unlikely to rise enough to trigger the fire wire. A severe leak may cause gas demister to overheat, and may melt also melt control wires near the leak with upredictable effects. Pressure balance inside the hood are such that little or no gas is likely to escape from a small leak, so a small leak is unlikely to be detected by smell or hearing. Downtime to replace joint is 3 days. 2. Gasket in Gas escapes into turbine hood and ambient temperature rises. ducting Buliding ventilation system would expel gases through louvers improperly fitted. to atmosphere. So concentration of gases is unlikely to reach noxious levels. A small leak at this point would be audible. Downtime to repair up to 4 days. 3. Hole in upper bellows due to corrosion.
The upper bellows are outside the turbine building, so a leak here discharges to the atmosphere, Ambient noise levels may rise. Downtime to repair, a few days to several weeks.
2. To reduce exhaust 1. Silencer material Most of the material would be blown out, but some might fail to A. Noise level exceeds noise to ISO mesh retaining the bottom of the stack and obstruct the turbine outlet causing ISO Rating 30 at 50m. Rating 30 at 50m. corroded away. high EGT and possible turbine shutdown. Noise levels would rise gradually. Downtime to repair about 2 weeks.
151
Figure 9.10 Failure modes and effects analysis (FMEA).
Defining Maintenance Strategies for Critical Equipment With Reliability-Centered Maintenance
System: 5MW Gas Turbine FUNCTION
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Reliable Maintenance Planning, Estimating, and Scheduling
Figure 9.11 Failure consequences.
Figure 9.12 Evaluating consequences with an RCM decision diagram.
Defining Maintenance Strategies for Critical Equipment With Reliability-Centered Maintenance
Figure 9.13 Proactive maintenance.
Figure 9.14 The P–F Interval.
153
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Figure 9.15 Areas of the “bathtub curve ”
Figure 9.16 Common equipment failure patterns.
Defining Maintenance Strategies for Critical Equipment With Reliability-Centered Maintenance
155
Figure 9.17 Default actions.
Further Reading Bloom, Neil B., 2005. Reliability Centered Maintenance; Implementation Made Simple. McGraw-Hill Companies Inc. Moubray, John, 1997. Reliability-centered Maintenance. Industrial Press. Smith, Anthony M., Hinchcliffe, Glenn, 2004. RCM-gateway to World Class Maintenance. Elsevier-Butterworth-Heinemann.