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Reliability Centered Maintenance Analysis
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  1. Systems Reliability, Supportability and Availability Analysis Reliability Centered Maintenance Analysis

  2. Cost of Maintenance and Repair Obtained from the RCM Guide, NASA September 2008

  3. What is RCM? The purpose of RCM • Identify policies that preserve the function of an asset in its operating context… • Preserve the function…not just maintain the equipment RCM ensures that: • The right maintenance is performed • At the right time • By the right people • In the right way • With the right training and tools

  4. What is RCM? (continued) RCM considers: • Scheduled maintenance based on failure characteristics in operating context • Design Changes • Training improvements • Operational changes • One time changes • Run to failure when cost effective and no safety/environment concerns RCM = less corrective maintenance RCM = more proactive approach

  5. Functional Perspective How do I keep the pump operating? How do I keep the tank full? B Water Pumping System Example Purpose: Ensure proper fluid level in tank B, by pumping fluid from tank A A • Traditional Maintenance Approach: • Focused on the pump • Vibration Analysis etc. • Minimize failures of the pump, • and determine maintenance strategy

  6. Why Functional? Traditional approach focused on keeping the pump operational Can other failures, besides pump failure cause the loss of system function? • Reservoir failure • Hoses and fittings failure What if the pump reliability cannot be improved, or maintenance cannot be optimized? Alternate methods to ensure the system function is preserved: • Pump redundancy (back-up pump) • Gravity assisted flow • Increased storage level in tank B (… buying time …)

  7. Where did RCM come from? Early PM assumed periodic overhauls ensured reliability and safety • Especially prevalent in airline industry • Based on the assumption that all equipment follow “bathtub curve” Commercial airlines questioned reliance on overhauls in 1960’s due to rising costs, without more reliability • Spurred by FAA assumption that new Boeing 747 PM program would be three times larger than Boeing 707 (three times more passengers) • Study launched to validate component failure characteristics

  8. D A 7% 14% B E 4% 2% 11% 89% 5% 68% C F Airline Findings FAILURE CHARACTERISTICS CURVES

  9. Overhaul interval Time More about an Overhaul Philosophy What the airlines discovered • Statistical analysis often showed no change in safety or reliability when overhaul limits changed…sometimes worsened • Overhaul limits were usually not analytically based • Overhauls generate high repair costs for little or no benefits Facts about overhauls • Many failure modes do not support overhaul philosophy - have no “wear out” characteristic • Considerable component life sacrificed • Overhauls introduce infant mortality failures Conditional Probability of Failure

  10. Post Study Study spurred development of conditioning monitoring techniques FAA and airlines established “Maintenance Steering Group (MSG)” to investigate/recommend new approaches • Initial Boeing 747 Customer Airlines and FAA • Boeing manufacturing and support engineers RCM developed and diverged into several “tracks” MSG (later coined RCM) applied the most appropriate maintenance philosophy to each failure mode based on data/information • Inspections • Operate to Failure

  11. RCM Tracks MSG-2 1970 MSG-3 1980 MSG-3R1 1988 On-going Updates Early PM MSG-1 1968 Space Shuttle RCM 1980 NASA Facility & GSE RCM 1988 Nolan Heap RCM 1978 Mil-Hdk-266 1981 Mil-Std-2173 1986 NAVAIR 403 Manual 1996 Commercial 1983 RCM II Moubray 1992 RCM Mac Smith 1993 SAE Standards 1999 Hybrid RCM 90’s

  12. What makes a process RCM? The seven SAE questions: • What are the functions and associated desired standards of performance of the assets in the present operation context (functions)? • In what ways can it fail to fulfill its functions (functional failures)? • What causes each functional failure (failure modes)? • What happens when each failure occurs (failure effects)? • In what way does each functional failure matter (failure consequences)? • What should be done to predict or prevent each failure (proactive tasks and task intervals)? • What should be done if a suitable proactive task cannot be found (default actions)?

  13. Standards and References DoD Policy: • “RCM shall be used as a logical decision process for determining optimum failure management strategies, including maintenance approaches, and establishing the need for both reactive and proactive maintenance tasks.” AFI 21-118 AR 750-1 MCO 4000.57A MIL-STD-3037 NAVAIR 00-25-403 SAE JA 1011/1012 DoD Manual 4151.22-M

  14. RCM in DoD

  15. RCM Process Flow (Navair) PLANNING AND PREPARATION • Identify Team and responsibilities • Identify analysis items • Prioritize Items • Identify and document Review Process • 5. Orientation/Training • 6. Ground Rules and Assumptions ANALYSIS • Equipment Kick-off Meeting • Initial Data Gathering • Hardware Partition • Function • Functional Failure • Failure Mode • Failure Effects • Failure Consequences • Task Evaluation • Task Selection FMECA SAE JA-1011 IMPLEMENT RESULTS • Package Maintenance Task • Implement Other Actions SUSTAIN • Emergent Issues • Age Exploration • Hardware Changes • Trend/degrader analysis • Document Reviews


  17. Planning and Preparation Identifies and resolves issues that must be addressed prior to beginning an analysis. Answers: • Who • What • In what order • How • With what resources • When Culminates in Project Plan

  18. Project Plan RCM Projects should document the results of the planning and preparation steps into an RCM Program Plan • Scope and size of plan is dependent on project • Ensures consistency of analysis process • Establishes priorities and schedule • Documents contributions of team members and concurrence by management • Can be used for funding justification and to gain management support

  19. Project Plan Elements RCM Program Plan Elements: • Team and Responsibilities • Analysis scope • Review and approval process • Training Requirements • Ground Rules and Assumptions • Sustaining task procedures • Hazard Risk Matrix • Metrics and Reporting requirements • Funding requirements • Plan of action and milestones • Contractor support requirements • Deliverables

  20. Ground Rules and Assumptions A compilation of information required by RCM analysts to perform analysis Items included: • Description of operating environment • Standard operating procedures • Data sources • Failure mode sources • Analytical methods • Cost-benefit analysis methods • Default Values • Acceptable probability of failure • Labor rates • Equipment usage rates

  21. 5 Minute BREAK

  22. Analysis PHASE

  23. Remember the Process…. Analysis Steps: • Equipment Kick-off Meeting • Initial Data gathering • Hardware Partitioning • FMECA • Failure Consequences • Task Evaluation • Task Selection Not discussed further Decision Logic

  24. Hardware Partitioning A logical hierarchical division of an asset into progressively lower levels to show relationships among systems, subsystems, components, etc. • Also called EQUIPMENT HIERARCHY or HARDWARE BREAKDOWN Partition may use any logical system: • CMMS • Work Unit Code • Maintenance/Operators manuals • OEM Parts breakdown • Physical boundaries

  25. HW Partitioning Considerations/Suggestions Must be a physical partition: • Each item should only be in one branch of the hierarchy • Consider how failure data is recorded • Partition one level below where the analysis will be performed • Manuals may provide logical divisions of equipment Boundaries should be clearly identified: • List specific valves, terminal blocks, etc. that end one system and begin another • Boundaries should take into consideration functions of equipment Be prepared to adjust boundaries: • During an analysis, better partitioning may become evident, especially when defining functions


  27. Partitioning Example: Power Plant POWER PLANT UNIT 2 N02 UNIT 1 N01 UNIT 3 N03 WASTE SYSTEM N02N BOILER N02B FUEL N02F FLY ASH N02NA BED ASH N02NB


  29. Class Exercise Perform an End Item Hardware partition for your vehicle GR&A: • No specific make/model • Use the following template 1st Level: End Item (Vehicle) 2nd Level: Major Systems 3rd Level: Major Components Use 5 minutes, group setting

  30. Class Exercise Solution

  31. Failure Mode, Effects and Criticality Analysis Process used to determine the functions, functional failures, and failure modes of equipment; and the associated effects, severity, and frequency of each failure mode Steps involve identifying... • Functions • Functional Failures • Failure Modes • Failure Effects • Severity of Failure effects • Frequency of occurrence FMEA “C” in FMECA

  32. Developing a FMECA Failure Modes, Effects, and Criticality Analysis Identifies: • Item – A description • Functions – What you want it to do • Functional Failures – How it fails to do it • Failure Modes – Why it fails to do it • Failure Effects – What happens • Severity of Failure – How bad it is • Failure Frequency – How often it happens • Criticality – Severity + Frequency

  33. FMECA Philosophy Function based on use not design capability Design capability > use to allow for degradation Functional failure may be actual or defined Failure modes- physical failure Failure effects- what happens when failure occurs • At the incident • To the system • To the asset

  34. Developing Functions Primary function: • The purpose for which the system or asset is acquired. Secondary functions • Other functions that the system or asset may perform. • Appearance • Containment • Control/ comfort • Environmental/ economy/ efficiency • Protective • Transmission • Safety/ structure/ superfluous

  35. FMEA to FMECA: Criticality Analysis Criticality assessment qualitative or quantitative Failure Mode Criticality, Cm : where

  36. Criticality Calculation Example

  37. Class Exercise Develop five functions the system for the hardware partition you developed earlier.

  38. Class Exercise Solution

  39. The ways in which a function fails May be more than one functional failure for a function Can be defined as a point short of actual failure Functional Failures

  40. The physical cause of the functional failure All reasonably likely failure modes listed Types of failure modes: Deterioration Design problem Over stress Failure Modes

  41. Describe what happens when a failure occurs Start at failure mode- Local Effect What happens at the component that fails Describe effect on system or sub-system The idea is to keep asking “what happens next” until the effect on the asset is reached Do not describe consequences (i.e. environmental, safety, economics) Failure Effects

  42. FMEA Example 1 Source NASA RCM Guide

  43. FMEA Example 2 Source NASA RCM Guide

  44. Class Exercise Develop two functional failures Develop three failure modes for one of the functional failures For each failure mode identify: • Local failure effects • System effects • End item effects

  45. Class Exercise Solution

  46. 5 Minute BREAK

  47. Remember the Process…. Analysis Steps: • Equipment Kick-off Meeting • Initial Data gathering • Hardware Partitioning • FMECA • Failure Consequences • Task Evaluation • Task Selection Decision Logic

  48. Decision Logic Process used to determine what action should be taken to eliminate or lessen the consequences that result from the occurrence of a failure mode

  49. Each Failure Mode reviewed to determine appropriate failure management strategy: Consequence Categorization (Hidden or Evident, Safety/Environmental or Economic/Operational impacts) PM Task selection (or No PM) Servicing Lubrication On Condition Hard Time Failure Finding Age Exploration Other Action RCM Process: RCM Task Evaluation

  50. Servicing: The replenishment of consumable materials that are depleted during normal operations. RCM PM Tasks