Reliability Centered Maintenance: Module III Salih O. Duffuaa

1. Reliability Centered Maintenance: Module III • Salih O. Duffuaa

2. Reliability Centered Maintenance • Objective of Module • Present the steps of RCM • Demonstrate the steps clearly • At the end each participant should • Understand the basics of RCM • Initiate an RCM project • Participate effectively in teams implementing RCM.

3. Impact Of RCM On O&M Costs • 1984 RCM pilot study At FP & L’s Turkey Point Nuclear plant provided evidence that RCM could impact O & M costs • Survey conducted by Electric Power Research Institute provided more evidence that RCM has impact on Cost.

4. RCM Impact • Plant trip reduction • Documented Basis For PM • Efficient PM Planning • Decrease in corrective maintenance • More accurate spare parts identification • Increase plant availability

5. Steps of RCM • System selection and data collection • System boundary definition • System description and Functional Block Diagram

6. RCM Steps Continued • Systems function and functional failures • Failure mode and effect analysis • Logic tree analysis (LTA) • Task selection

7. Level of RCM Application • Part • Component---Assembly • System • Plant

8. System Selection and Data Collection • Basis of system selection • What data and information to collect

9. Criteria for System Selection • 1- Systems with high PM tasks • 2- Systems with high breakdown maintenance • 3- Systems with large contributions to full or partial outages.

10. Criteria for Selection • 4- Systems with high cost of CM actions • 5- Systems with high content of concern with respect to safety and environmental issues • 6- Combinations of the Above • In a Typical selection process at Florida Power & Light Fossil Power Generation 5 is used coupled with Parato chart.

11. Information Collection • System piping and information diagram • System schematic block diagram • Vendor manual • Equipment history file • System operation manual • System design specification and data description

12. Importance of system Boundary Definition • It provides knowledge of what hs or has not been included • The boundary determines what comes into and what leave the system ( in and out) • Boundary definitions must be clearly stated and documented

13. Example of system Boundary Definition • Refer To Transparencies --- Figure 5.4 • System boundary details --- Figure 5.5 and Figure 5.6

14. System Description and Functional Block Diagram • System description • Functional block diagram • In/out interfaces • System work breakdown structure • Equipment history

15. System Description • Tangible benefit of system description • Account and document baseline definition of system as existed • Ensure comprehensive understanding of the system • Aid in identifying critical parameters that contribute to degradation and loss of function

16. System Description Cont. • Elements of System Description • Functional description/ key parameters • Redundancy features • Protection features • Key instrumentation features • See figure 5.7 in transparences

17. Functional Block Diagram (FBD) • The FBD is a top-level representation of the major functions the system performs • It consists of functions no equipment appear. labeled functional subsystems • In/out interfaces shown • See figure 5.8

18. System Work Breakdown Structure (SWBS) • Carryover from Ministry of Defense Terminology • Compilation of the equipment lists in each functional subsystems shown in the fbd • Include all components within system boundary • list all instrumentation components • See figure 5.10 and 5.11 for equipment history file

19. Systems Functions and Functional Failures • List all functions • In essence every out interface should be captured into a function statement • Two additional sources for functions • Internal out interfaces between functional subsystems • Passive functions • List all functional failures

20. Correct and Not Correct Function Statements • Provide 1500 psi safety relief valves(w) • Provide for pressure relief above 1500 psi • Provide a 1500 gpm centrifugal pump on the discharge side of header 26 (w) • Maintain a flow of 1500 gpm at the outlet of header 26.

21. Correct and Not Correct Function Statements • Provide alarm to control room if block valves are < 90 percent open (w) • Provide alarm to control room if flow rate is < 90 percent of rated flow • Provide water-cooled heat exchanger for pump lube oil (w) • Maintain lube oil  130 o F.

22. Functional Failure • The focus on loss of functions not loss of equipment • Absolutely necessary to distinguish between function loss conditions • Most functions have more than one loss condition • Distinction in loss condition usually leads to different failure modes

23. Functional Failures • Function: provide for pressure relief above 1500 psi • Functional failure • (a) Pressure relief occurs above 1650 psi • (b) Pressure relief occurs prematurely ( below 1500psi)

24. Examples of Different Functional Failure • Function : Maintain a flow of 1500 gpm at the outlet of header 26 • Functional failures • (a) Flow exceeds 1500 gpm • (b) Flow is less than 1500 but greater than 1000 gpm • ( c ) Flow is less than 1000 gpm • Function ad functional failure are recorded on figure 5.12

25. Failure Mode And Effect Analysis(FMEA) • Functional failure and equipment matrix • This matrix address which system equipment could play a role in the creation of functional failures. this is done by completing the matrix in figure 5.13.

26. Failure Mode and effect Analysis (FEMA) • Record The following on figure 5.14 • Component • Failure Mode --- Figure 5.15 provides typical description for failure modes • Failure cause • Failure effect • Local • System • Plant

27. Redundancy General Rule • If redundancy prevent loss of function then a failure shielded by redundancy should be given different priority than a failure mode that can singly defeat a necessary function. • If multiple independent failure in a redundant situation is possible the we identified a design issue

28. Logic Tree analysis (LTA) • The purpose of this step is further prioritize failure modes that survive step 5. the prioritization is done qualitatively using the logic tree diagram in figure 5.16 and form 5.17

29. Task selection • In this step the appropriate maintenance task is selected to prevent the loss of function. • The task selection road map in figure 5.18 is used for this purpose with form 5.19

30. Sanity Checklist • The purpose of this check is to review critically all components failures that are treated run to failure to see if this decision is optimal. • Explain form 5.21

31. Terms On Sanity Checklist • marginal effectiveness : it is not clear that the rtf costs are significantly less than the current pm costs • High-cost failure : while there is no loss of critical function, the failure mode is likely to cause extensive damage to the component that should be avoided.

32. Terms In Sanity Checklist • Secondary damage: similar to 2, except that there is a high probability extensive damage in neighboring components. • OEM conflict : The original manufacturer recommends a PM task that is not supported by RCM. It is very sensitive of warranty conditions are involved.

33. Terms In sanity Checklist • Internal conflict : Maintenance or operation feel strongly about the PM task that is not supported by RCM. • Regulatory conflict : regulatory body established the PM, such as EPA. • Insurance conflict : similar to the above two.

34. Comparison Between RCM Findings and existing Situation • RCM-based and current tasks are identical. • Current PM tasks exist, but need to be modified to meet RCM-findings.

35. Comparison Between RCM Findings and existing Situation • RCM-based PM tasks are recommended where no current tasks exist. • Current PM tasks exist where no RCM tasks-based task recommended-candidates for deletion