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NATIONAL AERONAUTICS

AND SPACE ADMINISTRATION

RELIABILITY CENTERED MAINTENANCE

GUIDE FOR

FACILITIES AND COLLATERAL EQUIPMENT

February 2000 v

• Chapter 1-Background 1− Table of Contents
  • 1.1 Introduction 1−
  • 1.2 Historical Evolution of RCM 1−
  • 1.3 Purpose of This Guide...................................................................................... 1−
  • 1.4 Applicability and Use of This Guide 1−
• Chapter 2Reliability Centered Maintenance (RCM) Approach 2−
  • 2.1 Philosophy 2−
  • 2.2 RCM Analysis 2−
  • 2.3 RCM Principles 2−
  • 2.4 Failure 2−
    • 2.4.1 System and System Boundary 2−
    • 2.4.2 Function and Functional Failure........................................................ 2−
    • 2.4.3 Failure Modes................................................................................... 2−
    • 2.4.4 Reliability 2−
    • 2.4.5 Failure Characteristics....................................................................... 2−
    • 2.4.6 Preventing Failure............................................................................. 2−
  • 2.5 Failure Modes and Effects Analysis 2−
    • 2.5.1 Criticality and Probability of Occurrence 2−
    • 2.5.2 Cause of Failure................................................................................ 2−
  • 2.6 Reliability Centered Maintenance Goals 2−
  • 2.7 Program Benefits 2−
    • 2.7.1 Safety 2−
    • 2.7.2 Cost 2−
    • 2.7.3 Reliability 2−
    • 2.7.4 Scheduling........................................................................................ 2−
    • 2.7.5 Efficiency/Productivity 2−
  • 2.8 Impact of RCM on the Facilities Life Cycle 2−
• Chapter 3 RCM Program Components 3−
  • 3.1 Reactive Maintenance.................................................................................... 3B
    • 3.1.1 Reactive Maintenance Criteria 3B
  • 3.2 Preventive Maintenance (PM)........................................................................ 3B
    • 3.2.1 Preventive Maintenance Criteria 3B
    • 3.2.2 Determining PM Task and Monitoring Periodicity 3B
  • 3.3 Predictive Testing & Inspection (PT&I)......................................................... 3B
    • 3.3.1 Data Correlation 3B
  • 3.4 Proactive Maintenance................................................................................... 3B
    • 3.4.1 Specifications for New/rebuilt Equipment......................................... 3B
    • 3.4.2 Precision Rebuild and Installation 3B
    • 3.4.3 Failed-Part Analysis.......................................................................... 3B
    • 3.4.4 Root-Cause Failure Analysis (RCFA) 3B
• ii February - 3.4.5 Reliability Engineering 3B - 3.4.6 Reliability Calculations..................................................................... 3B - 3.4.7 Rebuild Certification/Verification 3B - 3.4.8 Age Exploration................................................................................ 3B - 3.4.9 Recurrence Control 3B - 3.4.10 Facilities Condition Assessment........................................................ 3B
• Chapter 4 Predictive Testing & Inspection (PT&I) Technologies 4B
  • 4.1 Introduction 4B
    • 4.1.1 Alerts and Alarms 4B
  • 4.2 Vibration Monitoring & Analysis................................................................... 4B
    • 4.2.1 Applications and Techniques 4B
    • 4.2.2 Limitations 4B
    • 4.2.3 Logistics 4B
  • 4.3 Thermography 4B
    • 4.3.1 Applications...................................................................................... 4B
    • 4.3.2 Limitations 4B
    • 4.3.3 Logistics 4B
  • 4.4 Passive (Airborne) Ultrasonics....................................................................... 4B
    • 4.4.1 Applications and Procedures............................................................. 4B
    • 4.4.2 Limitations 4B
    • 4.4.3 Logistics 4B
  • 4.5 Lubricant and Wear Particle Analysis 4B
    • 4.5.1 Purpose............................................................................................. 4B
    • 4.5.2 Standard Analytical Tests 4B
    • 4.5.3 Special Tests..................................................................................... 4B
    • 4.5.4 Application 4B
    • 4.5.5 Sampling 4B
  • 4.6 Electrical Condition Monitoring..................................................................... 4B
    • 4.6.1 Techniques........................................................................................ 4B
    • 4.6.2 Additional Techniques and Troubleshooting 4B
    • 4.6.3 Applications...................................................................................... 4B
    • 4.6.4 Logistics ............................................................................................4-
  • 4.7 Non-Destructive Testing 4B
    • 4.7.1 Techniques........................................................................................ 4B
    • 4.7.2 Location & Intervals 4B
    • 4.7.3 Applications...................................................................................... 4B
    • 4.7.4 Limitations 4B
  • 4.8 Photography....................................................................................................4-
• Chapter 5CRCM Requirements During Facilities Acquisition............................................. 5B
  • 5.1 Planning....................................................................................................... 5B
  • 5.2 Design 5B
    • 5.2.1 Maintainability and Ease of Monitoring 5B
    • 5.2.2 Technology Review 5B
  • 5.3 Construction 5B
  • 5.4 Maintenance and Operations (M&O) 5B February 2000 iii
• Chapter 6CRCM Considerations During Facilities Operation.............................................. 6B
  • 6.1 RCM Program Data 6B
  • 6.2 Maintenance Feedback................................................................................. 6B
  • 6.3 Maintenance and Operations (M&O) Considerations 6B
• Chapter 7CRCM Contract Clauses .......................................................................................7B
  • 7.1 General Contract Clauses............................................................................. 7B
    • 7.1.1 Measurements and Measurement Data 7B
    • 7.1.2 Bearing Information........................................................................ 7B
    • 7.1.3 Gearbox Information....................................................................... 7B
    • 7.1.4 Pumps............................................................................................. 7B
    • 7.1.5 Centrifugal Compressors................................................................. 7B
    • 7.1.6 Fans 7B
    • 7.1.7 Vibration Monitoring 7B
    • 7.1.8 Vibration Monitoring Locations...................................................... 7B
    • 7.1.9 Lubricant and Wear Particle Analysis 7B
    • 7.1.10 Thermography 7B
    • 7.1.11 Airborne Ultrasonics....................................................................... 7B
    • 7.1.12 Pulse Echo Ultrasonics.................................................................... 7B
    • 7.1.13 Motor Circuit Analysis (Complex Phase Impedance) 7B
    • 7.1.14 Motor Current Spectrum Analysis................................................... 7B
    • 7.1.15 Insulation Resistance 7B
    • 7.1.16 Surge Testing.................................................................................. 7B
    • 7.1.17 Start-Up Tests................................................................................. 7B
    • 7.1.18 Maintainability and Ease of Monitoring 7B
    • 7.1.19 Leveling of Equipment Upon Installation........................................ 7B
  • 7.2 Architectural/Engineering (A&E) Contracts................................................. 7B
  • 7.3 Construction Contracts................................................................................. 7B
  • 7.4 Equipment Procurement Contracts............................................................... 7B
  • 7.5 Maintenance and Operations (M&O) Contracts 7B
• Chapter 8CPT&I Criteria.................................................................................................... 8B
  • 8.1 Baselines 8B
  • 8.2 Criteria by PT&I Technology....................................................................... 8B
    • 8.2.1 Vibration Monitoring 8B
    • 8.2.2 Lubricant and Wear Particle Analysis 8B
    • 8.2.3 Thermography 8B
    • 8.2.4 Airborne Ultrasonics....................................................................... 8B
    • 8.2.5 Motor Circuit Analysis.................................................................... 8B
    • 8.2.6 Motor Current Spectrum Analysis (MCSA) 8B
    • 8.2.7 Insulation Resistance 8B
    • 8.2.8 Surge Testing.................................................................................. 8B
    • 8.2.9 Start-Up Tests................................................................................. 8B
  • iv February
• Chapter 9CChecklists for RCM Quality Assurance 9B - 9.1 Planning....................................................................................................... 9B - 9.2 Design 9B - 9.3 Construction 9B - 9.4 Equipment Procurement............................................................................... 9B - 9.5 Maintenance and Operations 9B
• Chapter 10CManagement Indicators 10B - 10.1 General 10B - 10.2 Purpose of Metrics 10B - 10.2.1 Metrics Ownership 10B - 10.2.2 Definition of Metrics 10- - 10.3 Sample Metrics 10B - 10.4 Trending Indicators.................................................................................... 10B - 10.5 Recommended Agencywide Facilities Metrics 10B - 10.6 Metric Selection......................................................................................... 10B - 10.7 Benchmark Selection 10- - 10.8 Utilization of Metrics.................................................................................. 10- - 10.9 Examples of Benchmarks............................................................................ 10- - 10.10 Planning & Scheduling Metrics................................................................... 10- - 10.11 RCM Metrics 10-
• Appendix ACGlossary AB
  • Appendix BCAbbreviations/Acronyms...............................................................................BB
  • Appendix CCBibliography .................................................................................................CB
  • Appendix DCSources of PT&I Equipment, Services, and Training DB
  • Appendix ECVibration Criteria ..........................................................................................EB
  • Appendix FCPT&I Technologies Correlation Relationships FB
  • Appendix G—Alignment Standard GB
  • Appendix H—Balance Standard HB
  • Appendix I—AC Motor Repair and Reconditioning.............................................................IB
  • Appendix J—Maintenance Procedures.................................................................................JB
  • Appendix K—SPECSINTACT Clauses with RCM Applications KB
• 2-1. Criticality/Severity Categories...................................................................2- List of Tables
• 2-2. Probability of Occurrence Categories ........................................................2-
• 2-3. Chilled Water System Analysis .................................................................2-
• 2-4. Electric Motor Component Analysis..........................................................2-
• 2-5. Cause of Motor Bearing Failure ................................................................2-
• 2-6. RCM Facility Life-Cycle Implications ......................................................2-
• 3–1. Maintenance Priority Levels......................................................................3-
• 3–2. Reactive Maintenance Priorities ................................................................3-
  • Rotors (ISO 1940/1-1986).........................................................................3- 3–3. Balance Quality Grades for Various Groups of Representative Rigid
• 3–4. Recommended Coupled Alignment Tolerances (General Motors, 1993)....3-
• 3–5. Alignment Related Tolerances (General Motors, 1993).............................3-
• 3–6. Limitations on Rolling Bearing Misalignment (Harris,1984) .....................3-
• 3–7. Equipment Condition Classification Based on PT&I Data.........................3-
• 4–1. Estimated Steam Loss ...............................................................................4-
• 4–2. Recommended Maximum Inspection Intervals (API 570) .........................4-
• 6–1. Maintenance Training .............................................................................6-
• 7–1. Motor Balance Specifications..................................................................7-
• 7–2. Motor Vibration Criteria .........................................................................7-
• 7–3. Pump Vibration Limits............................................................................7-
• 7–4. Belt-Driven Fan Vibration Limits............................................................7-
• 7–5. ISO 3945 Vibration Severity Table. ........................................................7-
• 7–6. Vibration Acceptance Classes .................................................................7-
• 7–7. Machine Classifications ..........................................................................7-
• 7–8. Lubricant Tests .......................................................................................7-
  • for Various Hydraulic Systems................................................................7- 7–9. Sperry Vickers Table of Suggested Acceptable Contamination Levels
• 7–10. Typical Properties of Transformer Oils ...................................................7-
• 7–11. RCM Clauses for A&E Contracts............................................................7-
• 7–12. RCM Clauses for Construction Contracts................................................7-
• 7–13. RCM Clauses for Equipment Procurement Contracts ..............................7-
• 7–14. RCM Clauses for M&O Contracts...........................................................7-
• 8–1. Actions Required Based on Temperature Rise Under Load .....................8-
• 8–2. Temperature Limits for Selected Components.........................................8-
• 9–1. RCM Quality Assurance Planning Considerations...................................9-
• 9–2. RCM Quality Assurance Design Considerations......................................9-
• 9–3. RCM Quality Assurance Construction Considerations.............................9-
• 9–4. RCM Quality Assurance Equipment Procurement Considerations...........9-
• 9–5. RCM Quality Assurance Maintenance and Operations Considerations ....9-
• 10–1. Financial Benchmarks 10-
• 10–2. Organizational Benchmarks 10-
• 10–3. Work Practices Benchmarks.................................................................. 10-
• 10 – 3. Work Practices Data (Cont.).................................................................. 10-
• 1-1. Components of an RCM Program................................................................1- List of Figures
• 1-2. Bearing Life Scatter ....................................................................................1-
• 1-3. RCM Strategy and Process..........................................................................1-
• 2-1. RCM Analysis Considerations ....................................................................2-
• 2-2. Maintenance Analysis Process .................................................................2-
  • vi February
• 2-3. Reliability Centered Maintenance (RCM) Decision Logic Tree.................2-
• 2-4. Conditional Probability of Failure Curves .................................................2-
• 2-5. Preventing Failure.....................................................................................2-
• 2-6. FMEA Worksheet .....................................................................................2-
• 2-7. Stages of Life-Cycle Cost Commitment ....................................................2-
• 3-1. Sample System..........................................................................................3-
• 3-2. Effects of Misalignment on Roller Bearings ..............................................3-
• 3-3. Determining Network Reliability ..............................................................3-
• 3-4. Failure Analysis Form...............................................................................3-
• 3-5. Mean and Standard Deviation ...................................................................3-
• 3-6. Office Assessment Form ...........................................................................3-
• 4-1. PT&I Applications ....................................................................................4-
• 4-2. Sound Disc Diagram .................................................................................4-
• 4-3. Lubrication Analysis Chart .......................................................................4-
• 4-4. Power Factor Current/Voltage Relationship ..............................................4-
• 4-5. NDT Technique Selection Process ............................................................4-
• 4-6. Shielded Radiography Enclosure...............................................................4-
• 4-7. Magnetic Particle Testing..........................................................................4-
• 4-8. Inspection Program Development .............................................................4-
• 6-1. Design Improvements through Maintenance Feedback............................6-
• 7-1. Transducer Response ..............................................................................7-
• 8-1. Wear Particle Size and Equipment Condition ..........................................8-

1-2 February 2000

From approximately 1960 until the late 1980s, Preventive Maintenance (PM) was the most advanced technique used by progressive facilities maintenance organizations. PM is based on two principles - 1) a strong correlation exists between equipment age and failure rate, and 2) individual component and equipment probability of failure can be determined statistically, and therefore, parts can be replaced or rebuilt prior to failure.

PM assumes that failure probabilities can be determined statistically for individual machines and components and parts or adjustments can be replaced or performed in time to preclude failure. For example, a common practice in the past was to replace or renew bearings after some number of operating hours based on the assumption that bearing failure rate increases with time in service. This has proven to be ineffective.

Figure 1–2 shows the failure distribution of a group of thirty identical 6309 deep groove ball bearings installed on bearing life test machines and run to failure. The wide variation in bearing life is obvious and precludes the use of any effective time-based maintenance strategy^2. The X- axis is the individual bearing being tested while the Y-axis is the number of revolutions achieved prior to fatigue failure of the individual bearing. It should be noted that the bearings are tested at above-design loads to accelerate the failure rate. This is the standard procedure used to test bearings in order to determine the expected life of a bearing.

In all the studies, it was noted that a difference existed between the perceived and the intrinsic design life for the majority of equipment and components. In fact, it was discovered that in many cases equipment bearing life greatly exceeded the perceived or stated design life. For example, SKF Industries proposed changes in the method for evaluating bearing life - from the original method (empirical) proposed by Lundberg and Palmgren^3 to one where "bearings exhibit a minimum fatigue life; that is, 'crib deaths' due to rolling contact fatigue are non-existent when the aforementioned operating conditions (properly lubricated, mounted, operated and protected from dirt and moisture) are achieved."^4 This lack of a predefined fatigue life for bearings greatly impacts the concept of a predetermined design life for rotating equipment where rolling element bearings are used and provides the basis for extending the time between overhauls and equipment replacement.

This process, known as Age Exploration (AE), was used by the U.S. Submarine Force in the early 1970's to extend the time between periodic overhauls and to replace time based tasks with condition based tasks. While the initial program was limited to Fleet Ballistic Missile (FBM) submarines, it was continuously expanded until it included all submarines, aircraft carriers, other major combatants, and ships of the Military Sealift Command (MSC). Furthermore, the Navy has invoked the requirements of RCM and condition monitoring as part of new ship design specifications.

It should not be inferred from the above that all interval based maintenance should be replaced by condition based maintenance. In fact, interval based maintenance is often appropriate for

(^2) Eschmann, et al, Ball and Roller Bearings: Theory, Design, & Application, John Wiley & Sons, 1985 (^3) G. Lundberg and A. Palmgren, Dynamic Capacity of Roller Bearings, Acra Polytech, Mechanical Engineering

Series 1, R.S.A.E.E., No. 3, 7, 1947. (^4) Tedric A. Harris, Roller Bearing Analysis, Second Edition, John Wiley and Sons, New York, 1984

February 2000 1-

those instances where an abrasive, erosive, or corrosive wear takes place, material properties change due to fatigue, embrittlement, etc. and/or a clear correlation between age and functional reliability exists.

Development of new technologies during the 1990's, including affordable microprocessors and increased computer literacy in the work force, has made it possible to determine the actual condition of equipment and not have to rely upon estimates of when the equipment might fail based on age. These new cost effective technologies and the lack of correlation between age and failure in many equipment items have increased the emphasis on condition monitoring. Condition monitoring, commonly called Predictive Testing and Inspection (PT&I) within the NASA facilities maintenance environment, has resulted in a need to review existing Preventive (PM) and Programmed (PGM) Maintenance efforts and ensure that the most effective approach is being used. RCM provides the structure for developing that approach.

Closely aligned with determining what maintenance approach to use are the subjects of who should do the work and what parts and material will be needed to ensure that the work is done in the most cost efficient manner.

Most recently, RCM has taken on a prominent role in NASA's facility and equipment maintenance and operations program. RCM principles have been integrated into the SPECSINTACT (See Appendix K, Clauses with RCM Applications) wherein designs now have requirements for designing to maintainability. PT&I is used within the construction contractor's quality control program before and during commissioning to ensure that there are no latent manufacturing and installation defects at the time of equipment acceptance. PT&I and proactive

analyses are used as tools by NASA Quality Assurance Evaluators (QAEs) to monitor the contractor's compliance with the specific requirements of performance based contracts. RCM is

1 5 10 15 20 25 30 Bearing Number

Thirty Identical 6309 Deep Groove Ball Bearings Run to Fatigue Failure Under Test Load Conditions

From: Ball and Roller Theory, Design, & Application. Eschmann, et al John Wiley & Sons, 1985

Figure 1-2: Bearing Life Scatter

February 2000 1-

Management Handbook^5. Proactive techniques such as machinery alignment and balance criteria, Age Exploration, and Facility Condition Assessment (FCA) are also addressed.

(^5) NASA NPG 8831.2, Facilities Maintenance Management Handbook

Figure 1-3. RCM Strategy and Process

RCM Strategy

RCM Process

Spare Parts and Materials Determine material inventory level.

Establish material holding location.

Outcomes

Condition-Based actions including Overhaul and Repair. Run-to-Failure of non-safety related, low-cost, non-critical, easy to repair items.

Time- or Cycle-Based actions including Inspection, Calibration, and Condition Monitoring.

Proactive

Feedback to designers to improve the inherent reliability, maintainability and supportability.

Develop standards to select, install, and test systems and equipment.

Perform other activities to understand the cause of failure in order to eliminate it.

Maintenance Performance Optimization Determine who will perform the maintenance and repair actions.

1-6 February 2000

Intentionally Left Blank

2-8 February 2000

• What are the likely consequences of these functional failures?
• What can be done to reduce the probability of the failure, identify the onset of failure, or reduce the consequences of the failure?

Figures 2-1 and 2-2 illustrate the RCM approach and the interactive streamlined process.

Figure 2-1. RCM Analysis Considerations

Identify System and Boundary

Identify Sub-systems and Components

Examine Function

Define Failure and Failure Modes

Identify Consequences of Failure

· Primary or support? · Continuous or intermittent? · Active or Passive?

· System Input · System Output · Resources · Constraints

Failure · Hidden Failure · Potential Failure

Environmental, Health, and Safety Operational/Mission · Availability · Quantity · Quality Cost

To what level?

• Inconsequential

February 2000 2-

2.3 RCM Principles

The primary RCM principles are:

a. RCM is Function Oriented —It seeks to preserve system or equipment function, not just operability for operability's sake. Redundancy of function, through multiple equipment, improves functional reliability, but increases life cycle cost in terms of procurement and operating costs.

b. RCM is System Focused —It is more concerned with maintaining system function than individual component function.

c. RCM is Reliability Centered —It treats failure statistics in an actuarial manner. The relationship between operating age and the failures experienced is important. RCM is not overly concerned with simple failure rate; it seeks to know the conditional probability of failure at specific ages (the probability that failure will occur in each given operating age bracket).

d. RCM Acknowledges Design Limitations —Its objective is to maintain the inherent reliability of the equipment design, recognizing that changes in inherent reliability are the province of design rather than maintenance. Maintenance can, at best, only achieve and maintain the level of reliability for equipment, which is provided for by design. However, RCM recognizes that maintenance feedback can improve on the original design. In addition, RCM recognizes that a difference often exists between the perceived design life and the intrinsic or actual design life, and addresses this through the Age Exploration (AE) process.

e. RCM is Driven by Safety and Economics —Safety must be ensured at any cost; thereafter, cost-effectiveness becomes the criterion.

f. RCM Defines Failure as Any Unsatisfactory Condition —Therefore, failure may be either a loss of function (operation ceases) or a loss of acceptable quality (operation continues).

g. RCM Uses a Logic Tree to Screen Maintenance Tasks —This provides a consistent approach to the maintenance of all kinds of equipment.

h. RCM Tasks Must Be Applicable —The tasks must address the failure mode and consider the failure mode characteristics.

i. RCM Tasks Must Be Effective —The tasks must reduce the probability of failure and be cost effective.

February 2000 2-

k. RCM is a Living System —It gathers data from the results achieved and feeds this data back to improve design and future maintenance. This feedback is an important part of the Proactive Maintenance element of the RCM program.

Note that the maintenance analysis process, as illustrated in Figure 2-2, has only four possible outcomes:

• Perform Interval (Time- or Cycle-)-Based actions
• Perform Condition-Based actions
• Perform no action and choose to repair following failure
• Or determine that no maintenance action will reduce the probability of failure AND that failure is not the chosen outcome (Redesign or Redundancy).

These approaches will be discussed further in Chapter 3.

A formal RCM analysis of each system, subsystem, and component is normally performed on new, unique, high-cost systems such as aircraft and spacecraft systems and structures. This approach is rarely needed for most facilities and collateral equipment items because their construction and failure modes are well understood. Regardless of the technique used to determine the maintenance approach, the approach must be reassessed and validated. Figure 2- depicts an iterative RCM process that can be used for a majority of NASA facilities and collateral equipment.

2.4 Failure

Failure is the cessation of proper function or performance. RCM examines failure at several levels: the system level, sub-system level, component level, and sometimes even the parts level. The goal of an effective maintenance organization is to provide the required system performance at the lowest cost. This means that the maintenance approach must be based upon a clear understanding of failure at each of the system levels. System components can be degraded or even failed and still not cause a system failure (A simple example is the failed headlamp on an automobile. That failed component has little effect on the overall system performance). Conversely, several degraded components may combine to cause the system to have failed even though no individual component has itself failed.

2.4.1 System and System Boundary

A system is any user-defined group of components, equipment, or facilities that support an operational requirement. These operational requirements are defined by mission criticality or by environmental, health, safety, regulatory, quality, or other NASA-defined requirements. Most systems can be divided into unique sub-systems along user-defined boundaries. The boundaries are selected as a method of dividing a system into subsystems when its complexity makes an analysis by other means difficult.

2-12 February 2000

NO YES

NO YES

NO YES

NO YES

NO YES

NO YES

YES NO

Will failure of the facility or equipment items have a direct and adverse effect on safety or critical mission operations?

Redesign

Is the item Expendable?

Can redesign solve the problem permanently and cost effectively?

Is there a PT&I technology (e.g., vibration testing or thermography) that will monitor condition and give sufficient warning (alert/alarm) of an impending failure?

Is PT&I cost and priority- justified?

Ia there an effective PM task that will minimize functional failures?

Accept risk Install redundant unit(s)

Define PM task and schedule

Define PT&I task and schedule

Is establishing redundancy cost- and Priority-justified?

Figure 2-3. Reliability Centered Maintenance (RCM) Decision Logic Tree