Fundamentals of Reliability Centered MaintenanceRCM Marc Banghart April 5, 2011
About Me • Lead Reliability Engineer, Wyle Laboratories Jacksonville FL • Supporting several Reliability Information Analysis (RIAC) contracts • Past/Current Projects include: • AIM-120 Advanced Medium-Range Air-to-Air Missile (AMRAAM) • Lockheed Martin Remote Minehunting System • Mine Resistant Ambush Protected (MRAP) vehicles • B.S. Computer Science, M.S. Systems Engineering (SMU) • PhD Industrial and Systems Engineering (Mississippi State University) … in progress
The Purpose of 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
The Purpose of RCM • 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
B A B The Purpose of RCM RCM asks: How do I keep the tank full? Traditional maintenance asks: How do I keep the pump operating?
The Purpose of RCM • Assets that are poorly maintained cannot reach operational rates/goals • Return On Assets (ROA) will be affected by: • Product defects related to poor equipment condition • Unplanned asset downtime • Scheduled maintenance that isn’t necessary
Why Do RCM on Mature Systems? • Original Design FMECA’s: • Often used hardware vs functional approach • Hardware - manufacturing or engineering perspective (bottom’s up) • Functional – operators’ perspective (top-down) • Assumptions based on: • Similar/like systems (Little data on actual system or components) • Operating Environment vs Rarely updated except to address bad actors or major design changes
Why Do RCM on Mature Systems? (cont) • It’s Required by OSD Policy and Army Regulations: • “Army Aviation Maintenance seeks to transition from its current maintenance-intensive scheduled maintenance program and reactive unscheduled maintenance program to a predictive RCM program…” - Deputy Under Secretary of Defense for Logistics and Materiel Readiness, November 2002 • Army Regulation (AR) 750-1, Army Materiel Maintenance Policy, requires that RCM be applied to fielded weapon systems as well as systems in the procurement phase of their lifecycle
History of RCM HOW DID RCM COME ABOUT? • Early PM assumed periodic overhauls ensured reliability and safety • Commercial airlines questioned reliance on overhauls in 1960’s due to rising costs, without more reliability • FAA and airlines established “Maintenance Steering Group (MSG)” to investigate/recommend new approaches • MSG logic developed and first applied to Boeing 747
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 Overhaul interval ASSUMES THIS IS TRUE . . . Conditional Probability of Failure Time History of RCM: Overhaul Philosophy
D A 7% 14% B E 4% 2% 11% 89% 5% 68% C F Introduction To RCM: History Of RCM FAILURE CHARACTERISTICS CURVES
History of RCM: Alternatives to Overhaul-based Maintenance • Inspections (A way to address randomness) • Looking for “potential failure” condition • Leaves item in-service for most of its useful life • “Operate to Failure” • When consequences are severe - not an option • When consequences are acceptable - “operate to failure” may be best approach for cost/operations • MSG (later coined RCM) applied the most appropriate maintenance philosophy to each failure mode based on data/information
Traditional Maintenance Focuses on preserving the operation of the component Considers only scheduled maintenance on component or fix-when-failed Scheduled maintenance, if any, based on manufacturers’ or vendors’ recommendation More corrective maintenance Very reactive approach Reliability Centered Maintenance Focuses on preserving the function of the system Considers many options Fix-when-failed only when cost effective Scheduled maintenance based on the failure characteristics of the component in its operating context Less corrective maintenance Proactive approach RCM – A Better Way
The RCM Process SystemDocumentation Functional Hierarchy System/Asset Boundaries & Priorities System Analysis Resources System Analysis Resources RCM System Analysis RCM System Analysis Package Analysis Results Implement Packaged Results
Aircraft Engine Landing Gear Airframe Compressor Doors Subsystem #1 Diffuser Nose Gear Subsystem #2 Etc…….. Braking System Subsystem #3 System Development – Example: Aircraft
The RCM Process: System Analysis • Heart of RCM process is RCM system analysis • 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)?
The RCM Process: System Analysis • The seven SAE questions (cont) • 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)?
The RCM Process: 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
FMEA 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
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
Functional Failures • 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
Failure Modes • The physical cause of the functional failure • All reasonably likely failure modes listed • Types of failure modes: • Deterioration • Design problem • Over stress
Failure Effects • 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)
RCM Process: RCM Task Evaluation • 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
Servicing: The replenishment of consumable materials that are depleted during normal operations. RCM PM Tasks
Lubrication: The scheduled lubrication of a component (usually based on the manufacture’s recommendations) where the item’s design requires a non-permanentlubricant for proper operation RCM PM Tasks
On-Condition Periodic or continuous inspection designed to detect a potential failure condition prior to functional failure. RCM PM Tasks
Hard Time Task: Scheduled removal of an item or a restorative action at some specified age limit to prevent its functional failure. RCM PM Tasks
RCM Other Actions • Usually a one time action, other than PM, that effectively reduces consequences of failure or resolves problems identified during the conduct of the analysis • Examples: • Item redesign • Change in an operational or maintenance procedure • Operating restrictions • Training • Publications • Technology insertion
The RCM Process: Package Analysis Results • Performed after all failure modes for the system completed • Recommended tasks are combined into an efficient, effective and executable maintenance program
The RCM Process: Implement Packaged Results • Tasks not implemented are of no value • Detailed implementation plan • Plant personnel must implement tasks • Detailed implementation plan makes implementation easier • System expert team develops implementation plan • They will carry it out • Plan will be workable, effective, and implemented
Safety, environmental hazards, operations, and economic impacts are put into balance RCM in a Nut Shell • In summary, RCM asks: • What does an item do? • How does it do it? • How does it fail? • What happens when it fails? • Can the failure be prevented or mitigated? • Is there value in preventing or mitigating the failure? • Does in-service data indicate changes or improvement are needed?
Questions? Thank you! Please feel free to send any questions/comments to Marc at firstname.lastname@example.org