Reliable Maintenance Planning, Estimating, and Scheduling. http://dx.doi.org/10.1016/B978-0-12-397042-8.00009-7Copyright © 2015 Elsevier Inc. All rights reserved.

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 reliability- centered 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 imple-mented. 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 con-sultants 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

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 require-ments 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.

147Defining 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.

148 Reliable Maintenance Planning, Estimating, and Scheduling

Figure 9.5 Functions and performance standards.

Figure 9.6 Functional failures.

149Defining Maintenance Strategies for Critical Equipment With Reliability-Centered Maintenance

Figure 9.7 Functional failures.

Figure 9.8 Failure modes.

150 Reliable Maintenance Planning, Estimating, and Scheduling

Figure 9.9 Failure effects.

151D

efining Maintenance Strategies for C

ritical Equipm

ent With R

eliability-Centered M

aintenance

System:5MW Gas Turbine

FUNCTION

To channel all thehot turbine airwithout restrictionto a fixed point10m above theroof of the turbinebuilding.

1. Unable to channel gasat all.

A. Silencermountingscorroded away.

Silencer assembly collapses and falls to bottom of stack. Backpressure causes the turbine to surge violently and shut downon high exhaust gas temperature. Downtime to replace silencerup to four weeks.

1.

Part of silencerfalls off due tofatigue.

1.

Hole in flexiblejoint fromcorrosion.

1.

Gasket inductingimproperly fitted.

2.

Hole in upperbellows due tocorrosion.

3.

Silencer materialmesh retainingcorroded away.

1.Noise level exceedsISO Rating 30 at 50m.

A.

Gas flow resticted.B.

Fails to maintain thegas.

C.

To reduce exhaustnoise to ISORating 30 at 50m.

2.

FUNCTIONAL FAILURE(Loss of Function)

FAILURE MODE(Cause of Failure)

FAILURE EFFECTWhat happens when it fails?

Sub-System:Exhaust System

EXAMPLE: FAILURE MODES AND EFFECTS ANALYSIS (FMEA)

Depending on the nature of blockage, exhaust temperaturemay rise to where it shuts down the turbine. Debris coulddamage parts of the turbine. Downtime to repair silencer up tofour weeks.

The joint is inside turbine hood, so leaking exhaust gases wouldbe extracted by the hood extraction system. Fire and gasdetection equipment inside hood is unlikely to detect anexhaust gas leak, and temperatures are unlikely to rise enoughto trigger the fire wire. A severe leak may cause gas demisterto overheat, and may melt also melt control wires near the leakwith upredictable effects. Pressure balance inside the hood aresuch that little or no gas is likely to escape from a small leak, soa small leak is unlikely to be detected by smell or hearing.Downtime to replace joint is 3 days.

Gas escapes into turbine hood and ambient temperature rises.Buliding ventilation system would expel gases through louversto atmosphere. So concentration of gases is unlikely to reachnoxious levels. A small leak at this point would be audible.Downtime to repair up to 4 days.

The upper bellows are outside the turbine building, so a leakhere discharges to the atmosphere, Ambient noise levels mayrise. Downtime to repair, a few days to several weeks.

Most of the material would be blown out, but some might fail tothe bottom of the stack and obstruct the turbine outlet causinghigh EGT and possible turbine shutdown. Noise levels wouldrise gradually. Downtime to repair about 2 weeks.

Figure 9.10 Failure modes and effects analysis (FMEA).

152 Reliable Maintenance Planning, Estimating, and Scheduling

Figure 9.11 Failure consequences.

Figure 9.12 Evaluating consequences with an RCM decision diagram.

153Defining Maintenance Strategies for Critical Equipment With Reliability-Centered Maintenance

Figure 9.13 Proactive maintenance.

Figure 9.14 The P–F Interval.

154 Reliable Maintenance Planning, Estimating, and Scheduling

Figure 9.15 Areas of the “bathtub curve ”

Figure 9.16 Common equipment failure patterns.

155Defining Maintenance Strategies for Critical Equipment With Reliability-Centered Maintenance

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.

Figure 9.17 Default actions.