Reliability-Centered Maintenance. An introduction to by JBM
- 1. 7/26/2011 Content 1. RCM Introduction 2. Maintenance Strategy Review 3. Introduction to Functional Analysis Reliability-Centred Maintenance 4. Introduction to FMECA “An Introduction to” 5. Function selection 6. RCM Tasks evaluation 7. RCM Tasks selection Jean-Baptiste MARTIN 8. RCM Implementation 9. Feedback Risk, Safety & Reliability Consultant JBM 2 RCM Introduction RCM Introduction Logical and systematic approach to define a routine Started in 1960’s – Federal Aviation Administration maintenance program composed of cost-effective tasks (USA) concerned with high crash rate that preserve important functions 1978: “Reliability-Centred Maintenance” Report by Process to establish the safe minimum levels of United Airlines Engineers (for US Defence) maintenance Basis of Maintenance strategy Promulgated in 1980s Process to determine the maintenance requirements of any physical asset in its present operating context Used these days (slightly modified) by commercial aviation industry “Why” maintenance should be conducted on equipment instead of “What” maintenance tasks could be done JBM 3 JBM 4 1
- 2. 7/26/2011 RCM Introduction RCM Introduction First RCM approach RCM strength Frequent overhaul and parts replacement HSE levels are met or exceeded Costly and did not improved reliability Increase cost effectiveness Maximize equipment availability Why Aviation Industry ? Reduce repairing time The “Fix it when it breaks” approach was obviously not acceptable for airplanes ! Set up a new data base Availability Nowadays derivatives of RCM implemented in many other industries Maintenance Cost JBM 5 JBM 6 RCM Introduction Maintenance Strategy Review RCM weakness Functional analysis Requires significant effort and focus (labor intensive) FMECA F Needs some specific data to be available or assumed e (MTBF etc.) e Yes / No answers are required – but everything is not Significant functions selection always black / white d Where to stop ? Level of details should be defined at the b RCM task evaluation beginning a c RCM task selection k RCM implementation JBM 7 JBM 8 2
- 3. 7/26/2011 Maintenance Strategy Review Maintenance Strategy Review 1930’s 1950’s – 1980’s 2000’s Different maintenance strategies On failure Increased demand of goods Stringent economical On failure: “We need to fix it quickly !” maintenance (World war II) environment “Feeling”: “Why not maintaining it tomorrow before Downtime not an Increased automation Need to reduce operating lunch?” issue & maintenance costs Higher maintenance cost Based on experience: “If some maintenance is good, then 6 , TPM, RBI, RCM a lot more must be better !” or “We have always done it Scheduled Overhaul that way!” Planning Systems Computerisation Maintenance is a process NOT an event JBM 9 JBM 10 Maintenance Strategies Review Maintenance Strategy Review Need for MSR Dangers of MSR Safety, cost-effective & Fall into the technology technical viability trap Produce an optimised Use inappropriate maintenance programme technology Document all information Fail to set Functional analysis used in making decisions objectives/success Identifies important criteria monitoring parameters Fail to address cultural Allows for feedback & issues continuous improvement Fail to gain management support JBM 11 JBM 12 3
- 4. 7/26/2011 Introduction to Functional Analysis Introduction to Functional Analysis Integrated Definition (IDEF0) Integrated Definition (IDEF0) Function: an activity, process, or transformation identified by a verb or verb phrase that describes what must be Control accomplished. Input: data or consumables that trigger the activity Control: commands which guide or Control Input Function Output influence the activity Input Function Mechanism JBM 13 JBM 14 Introduction to Functional Analysis Introduction to Functional Analysis Integrated Definition (IDEF0) Mechanism: means, tools or people used to accomplish the activity (allocation of activities) Outputs: data or products that are produced by the activity Function Output Mechanism JBM 15 JBM 16 4
- 5. 7/26/2011 Maintenance Strategy Review Introduction to FMECA Failure Modes, Effects and Criticality Analysis Extension of FMEA Identification of all possible failures within a system, the possible effects of these failures and any potential consequences FMECA Ranking of these potential problems in terms of “Criticality” JBM 17 JBM 18 Introduction to FMECA What is the function? Two categories of functions Primary Functions: usually fairly easy to recognise. They are the main reasons why assets have been acquired Secondary Functions: less obvious than the primary, even though their failure can sometimes have more serious consequences (Environmental, Safety, Control / Comfort, Appearance, Protection, Economy etc.) Function description: “To be capable of”, “To provide” What is the function ? Example: Pump Primary function: To pump oil from well to refinery Secondary function: To contain the fluid JBM 19 JBM 20 5
- 6. 7/26/2011 What is the function? What is the function? Operational mode – Example is Airplane Performance standards Taxi Performance standards specify the boundary between Take-off satisfactory performance and failure Climb Performance standards describe the minimum acceptable performance requirement associated with functions rather Cruise than the item design capability Descent Some performance standards can be drawn directly from Approach the operating context Flare-out Roll JBM 21 JBM 22 What is the function? Introduction to FMECA “What are the items supposed to do …” Define The Primary Function “What It Is Required To Do” - Not The Design Define The Performance Standards “Quantitative rather than Qualitative” Define The Tolerances On The Performance Standard “Minimum, Maximum, Nominal Etc.” In what way can it fails? JBM 23 JBM 24 6
- 7. 7/26/2011 In what way can it fails? In what way can it fails? Functional Failure: inability of an asset to fulfil a function with an acceptable level of performance for When capability drops below desired the user performance after the asset commissioned Covers • Most common Complete loss of function Situations where the asset still functions but performs When desired user performance raises above outside acceptable limits capability after the asset commissioned Described as “Fails to be capable of …” When the asset is not capable of doing what is wanted from the beginning JBM 25 JBM 26 Introduction to FMECA What’s the failure modes ? A failure mode is any event which could cause a functional failure - past, future & currently prevented All failure modes which are reasonably likely to cause a functional failure should be identified The root cause of failure modes should be identified Black boxing is acceptable under certain circumstances What are the failure modes? JBM 27 JBM 28 7
- 8. 7/26/2011 What’s the failure modes ? Introduction to FMECA Failure detection: the means by which functional failures become evident and how their failure Evident: lights, buzzers, smoke etc. Hidden: detectable by maintenance only Example: the failure mode “fail to start” of a pump with operational mode “standby” is an example of a hidden failure. What are the effects of failure? JBM 29 JBM 30 What the effects of failure? FMECA Effect identification should describe The effects on safety or the environment The effect on production/operation (economic or service level) Potential secondary damage to other equipment Downtime or repair actions with estimated time (loss of function to the restoration of function) Does it matter? JBM 31 JBM 32 8
- 9. 7/26/2011 Does it matter? Does it matter? Severity categories (examples) Ranking of Risk Priority Number (RPN) Hidden or evident under normal conditions O = the rank of the occurrence of the failure mode Safety or environmental S = the rank of the severity of the failure mode Operational (economic or service level) D = the rank of the likelihood the failure will be detected Non-operational before the system reaches the end-user/customer Etc. The smaller the RPN the better – and – the larger the worse RPN = S x O x D JBM 33 JBM 34 Does it matter? Does it matter? Severity Ranking Example Occurrence Ranking Example JBM 35 JBM 36 9
- 10. 7/26/2011 Does it matter? Maintenance Strategy Review Detection Ranking Example Significant functions selection JBM 37 JBM 38 Functions Selection Functions Selection Function selection Significant Function (SF) – A function whose failure will result in adverse consequences with respect to safety, the environment, operations, or economics Non-significant Function (NSF) – A function whose failure will have no adverse safety, environmental, operational, or economic consequences SF Selection Logic diagram Apply to every function that has the potential of being significant First question in the logic flow that evokes a “YES” answer dictates that the function is significant JBM 39 JBM 40 10
- 11. 7/26/2011 Maintenance Strategy Review RCM decision logic RCM task evaluation √ = Optional M = Mandatory JBM 41 JBM 42 RCM task evaluation RCM task evaluation - OC Task evaluation: process used to determine which of On Condition task (predictive) several options is best suited to To detect potential failure Prevent a failure mode from occurring And then take action to prevent the functional failure or to Reduce the consequence of its failure to a level that is avoid the consequences (outside of RCM scope) acceptable Each option has unique criteria that determine if the task is appropriate for the failure mode JBM 43 JBM 44 11
- 12. 7/26/2011 RCM task evaluation - OC RCM task evaluation - SR Development of OC task Scheduled Replacement Do we have any prior warning of the failure? Removes or restores the item at a predetermined age What is this warning? regardless of whether or not failure is impending How long will it take to fail from the prior warning? SR development Is It consistent in time? Do we have a reliable age projection (Wear Out)? Will it give us enough time to respond appropriately? Will most items reach this age? Can a task interval be developed that reduces the probability of failure to an acceptable level? If YES to ALL: OC is technically feasible If YES to ALL: SR is technically feasible JBM 45 JBM 46 RCM task evaluation - SR RCM task evaluation - FF Wear out Failure Finding task Increase in the conditional probability of failure with age Objective: prevent or at least reduce the probability of the associated multiple failure Life limit Check a hidden function at regular intervals to find out Safe Life Limit (SLL) whether it has failed Economic Life Limit (ELL) Multiple failure is when the protected function fails and the protective device is also in a failed state FF task should avoid dismantling protective devices or otherwise disturbing them ELL SLL JBM 47 JBM 48 12
- 13. 7/26/2011 RCM task evaluation - FF RCM task evaluation - OFM Failure Finding Interval On Failure Maintenance task valid only if: MTBF of protective device A suitable proactive or failure-finding task cannot be Desired availability of the device found for a hidden failure, and the associated multiple failure does not have safety or environmental consequences Availability (%) 99.99 99.95 99.90 99.50 99.00 98.00 95.00 A cost-effective proactive task cannot be found for evident Interval (% of 0.02 0.10 0.20 1 2 4 10 failures which have operational or non-operational MTBF) consequences JBM 49 JBM 50 RCM task evaluation - RD Maintenance Strategy Review Re-Design definition A change in the physical configuration of an asset or system A change to a process or operating procedure A change to the capability of a person, usually by training RCM task selection Re-Design if only The multiple failure could affect safety or the environment If the multiple failure does not affect safety or the environment but RD economically justified JBM 51 JBM 52 13
- 14. 7/26/2011 RCM Task selection RCM Task selection Three types of outputs depending on the option Cost Perform PM tasks (OC, FF, SR) Cost of options are typically compared by normalizing Allow the failure mode to occur, then take corrective them to a common unit such as cost per unit operating action (OFM) hour, cost per hour, or cost per cycle Take some other action, such as redesigning the item Operational consequences (RD) If the operational impact is considered more important, BEST solution: comparing each of the available options the more expensive task should be chosen with the others How to define which one is the BEST ? JBM 53 JBM 54 Maintenance Strategy Review RCM implementation Build RCM Team RCM Facilitator Production Maintainers HSE RCM implementation Ensure RCM methodology is followed Keep the review at the right level Document all the RCM information Chair and manage the meetings / workshops (ensure time aspects and involvement of all members etc.) JBM 55 JBM 56 14
- 15. 7/26/2011 RCM implementation RCM implementation Make documents available Align tasks for effective resources and production use Plant overall plot plan ; layouts Process flow Diagram Schedule routine maintenance Operating & Maintenance manuals Incorporate into SAP Existing maintenance strategy Maintenance history record Define context : objectives Process / product affected Applicable HSE regulations Process availability requirements Business risk & reliability DownTime economics JBM 57 JBM 58 RCM implementation RCM implementation Alternative to detailed RCM (medium criticality Alternative to detailed RCM (Low criticality functions): functions): Generic RCM MS Review Define equipment type (pump, filter etc.) Analyse vendors recommendations Define failure modes from previous experience Define failure modes from previous experience Define failure consequences Define failure consequences Compare existing vendor tasks with failure modes Define failure characteristics Determine if task is Determine task or strategy most applicable (R) retained Apply task routines to medium criticality equipment (U) updated generically (C) changed or Ensure consequences are still applicable (D) deleted JBM 59 JBM 60 15
- 16. 7/26/2011 Maintenance Strategy Review Feedback RCM analysis will never be perfect because Numerous decisions have to be made on the basis of incomplete or non-existent hard data The assets, and the processes of which they form part, Feedback will be subject to continuous change The perspectives, attitudes and priorities of people will be changing continuously Technological advancements may affect / invalidate analysis decisions JBM 61 JBM 62 Feedback Conclusion The RCM should be periodically reviewed RCM Is an effective mean of improving production availability Collect data on the effectiveness of the maintenance and reducing maintenance cost program through in-service equipment performance But has some weaknesses … To investigate and correct maintenance related problems A strong RCM team is needed To identify hardware design and manufacturing Management willingness and support is required deficiencies Close cooperation between maintenance and production To document specific resource savings that are achieved through the RCM process Basics equipment information required as a starting point Compare cost, manpower, and readiness levels achieved by previous maintenance approach to the revised RCM strategy Let’s implement RCM on a pilot system ! JBM 63 JBM 64 16