Determining a defensible preventive maintenance plan

Transcription

1 Determining a defensible preventive maintenance plan Presented by Jim Kennedy, CPEng, CFAM, CAMA Interlogis Consulting Page 1

2 1 August 2017 Interlogis Consulting Page 2 Course Agenda Day 1 Introduction Session 1 Maintenance and its management Session 2 Risk and Reliability Session 3 RCM and Condition Monitoring task period

3 1 August 2017 Interlogis Consulting Page 3 Course Purpose and Outcomes Purpose To prepare for determining an objective condition monitoring program using optimising and verifying algorithms in a defensible manner. Outcomes Define the defensible budget concept Understand and list the maintenance management objectives in Asset Intensive industries Define maintenance and identify the different types Describe the failure characteristics associated with preventive maintenance plans Explain the role and development of Preventive Maintenance Plans Explain the basic process of FME(C)A/RCM/LORA/TA Determine condition monitoring task periods Verify condition monitoring task period

4 Session 1 Maintenance and its Management Setting the scene

5 1 August 2017 Interlogis Consulting Page 5 The defensible (maintenance) budget Assures agreed and verifiable objectives of: Safety and environmental risks managed Required performance achieved at known level of assurance All done at a desired balance between the performance, the cost and the residual risk Defensible is defined as comprising solutions that are: Fact and risk based Fully traceable to system/asset output requirements Demonstrably good practice (international and national standards) Compliant with statutory and regulatory imperatives Implemented by competent (certified) staff Supported by verified technology (information and decision systems) Transparently and verifiably costed Deliverable in the agreed time frame

6 1 August 2017 Interlogis Consulting Page 6 What is Maintenance? All activities necessary to retain an item in or return it to a serviceable condition. Blanchard 1974 Nowlan and Heap 1978 IEC International Electrotechnical Vocabulary*

7 1 August 2017 Interlogis Consulting Page 7 Maintenance objectives - aerospace industry Preserve inherent levels of safety and reliability designed into equipment Restore safety and reliability to their inherent level when deterioration has occurred Obtain the information to improve all processes associated with the system lifecycle Do the above at minimum cost of ownership Adapted from Nowlan and Heap page xvi December 1978 Activity 1.3

8 1 August 2017 Interlogis Consulting Page 8 Maintenance Terminology Maintenance Objectives Preventive Maintenance Condition Monitor Hard Time Activity Functional Test Planned Corrective Maintenance Repairs (Stds) Unplanned Renewals (Cost)

9 1 August 2017 Interlogis Consulting Page 9 Technical Maintenance Plans Preventive maintenance policies developed using FMECA/RCM to achieve inherent asset reliability. TMPs were introduced in the Royal Australian Air Force in 1970s, Rail Industry in 1980s. Power Industry in 1990s. Electrical distribution in 2000s Policies cover: Which assets are to be maintained? What maintenance is to be done? When the maintenance is to be done? How the maintenance is to be done? Where the maintenance is to be done? Who is authorised to do the maintenance?

10 1 August 2017 Interlogis Consulting Page 10 Maintenance Requirements Analysis Failure Mode Effects and Criticality Analysis FMECA Reliability Centered Maintenance RCM Level of Repair Analysis - LORA Task Analysis - TA Maintenance requirements analysis process Assets Failure modes and parts Corrective LORA Repairs FMECA TA Business Functions Failure modes parts, risk and causes RCM Preventive Service Schedule TMP

11 Session 2 Risk and Reliability Doing it by the numbers

12 Communicate and Consult Monitor and Review Risk management process AS HB89 Risk assessment methods Event Tree Analysis Fault Tree Analysis Establish the Context Cause and Consequence Bow Tie Diagram Identify Risks Analyse Risks Evaluate Risks Treat Risks Failure Modes and Effects Analysis (FMEA) Fault Mode, Effects and Criticality Analysis (FMECA) Reliability Block Diagram Human Reliability Analysis Consequence/Likelihood Matrix Cost Benefit Analysis Multi Criteria Decision 1 August 2017 Interlogis Consulting Page 12

13 1 August 2017 Interlogis Consulting Page 13 FMECA a risk process Business Requirement Asset Solutions Functional Block Diagram Reliability Block Diagram Functional Performance System Functions Equipment Functions Preventive Actions Corrective Actions Operator Actions Maintainer Actions Redesign Actions Failure Modes Failure Effects Failure Probability Consequence L H Identify Mitigation RISK

14 1 August 2017 Interlogis Consulting Page 14 Reliability and the Bathtub Curve H(f) Hazard Function Wear-in Useful life Wear-out Age Reliability Definition The probability that a defined item shall operate to a defined standard for a defined period of time in a defined operating environment

15 1 August 2017 Interlogis Consulting Page 15 Hazard function in reliability The hazard function defines: Conditional probability of failure in a particular time interval which can be dependent on previous intervals i.e. the expected future (T+Δt) rate of failure of an item of equipment given that it has survived to a particular age (T) T may be measured in time or events.

16 1 August 2017 Interlogis Consulting Page 16 Weibull Family of Curves MTBF Probability Density Function Reliability Function Hazard Function Raw failure data set Likelihood of surviving to time t Likelihood of failure having survived to time t

17 1 August 2017 Interlogis Consulting Page 17 Relating characteristic to task type % 1968 Nowlan and Heap AD AO pdf 68 88% time Source NASA

18 1 August 2017 Interlogis Consulting Page 18 RCM and technology impact % Nowlan and Heap AD AO66579 % % % 77% 71% Reliability Centered Maintenance Source NASA

19 1 August 2017 Interlogis Consulting Page 19 Probability density function (Constant failure rate) Number of failures of survivors in a discrete time period pdf f(t)= l e -lt ie if 100 items at start and failure rate of 10% then 0 = = 90 ( /10 = 90) 2 = 81 (90-9/10 = 81) 3 = 73 (81-81/10 = 73) 4 = 66 (73-73/10 = 66) time

20 1 August 2017 Interlogis Consulting Page 20 Random failure pattern - Condition monitor Each Item achieves maximum life but at the cost of many Condition Monitoring tests Resistance to failure 100% pdf Resistance to failure 0% Time time 100% Degrading Asset Condition Conditional Defect Point 0% Time

21 1 August 2017 Interlogis Consulting Page 21 Random failure pattern Number of survivors at t = MTBF

22 1 August 2017 Interlogis Consulting Page 22 RCM 7 Questions and 4 Answers 1. Which assets are important to the business? 2. What are its functions? 3. How does it fail to perform that function? 4. What causes it to fail? 5. What happens when it fails? 6. How can that failure be managed? 7. What can be done if the failure cannot be managed?

23 1 August 2017 Interlogis Consulting Page 23 RCM - The four risk based solutions Examine condition to detect potential failures (Condition Monitor) Restore or discard before a maximum age (Hard Time) Check to find failures that are not evident (Failure Finding) Apply default tasks of run to failure or redesign

24 1 August 2017 Interlogis Consulting Page 24 Knowledge outcomes of MRA The analysis achieves a detailed listing of: what functions and equipment comprise the rail system solution what equipment related failure modes adversely impact function what are the risks associated with those failure modes what preventive tasks (controls) will reduce failure risk what corrective tasks are available to recover from failures what quality elements are necessary to assure task effectiveness what hazards are Inherent in the tasks what controls are necessary to manage those hazards

25 Session 3 CM Determination and verification What is my inspection period?

26 1 August 2017 Interlogis Consulting Page 26 Seven Step Analysis Process 1. Breakdown the asset into systems and items of equipment. 2. Prioritise the assets for analysis according to risk exposure from failure. 3. Collect system information and define each failure problem to be addressed. 4. Establish possible preventive maintenance strategies for dealing with each failure cause based on its consequence. 5. Evaluate the validity of each particular preventive maintenance policy (task and frequency). 6. Determine what to do if there are no applicable and effective maintenance policies. 7. Package the valid preventive maintenance policies into cost effective schedules.

27 1 August 2017 Interlogis Consulting Page 27 Preventive maintenance task options Is a condition monitoring task applicable and effective Is a scheduled restoration task applicable and effective Is a scheduled discard task applicable and effective Is a failure finding task applicable and effective Condition monitoring is intended to identify the potential for item failure with sufficient warning to allow maintenance prior to failure. The MIL-STD-2173 algorithm determines the optimum number of examinations across the CF interval. CSIRO Maths Division - validation paper (Mar 2001) Additional consideration should be given to critical operating equipment that is not readily removed from service for maintenance (requirement for warning time) Redesign or Run to failure

28 1 August 2017 Interlogis Consulting Page 28 Matching condition to task period Resistance to failure You cannot stop the failure but! You can change the consequence 19 Conditional Failures 100% Degrading Asset Condition Conditional Defect Point Standards Decision Functional Failure Point 20 Items 0% Time 1 Functional Failure Task Period < Warning period and Task Effectiveness of 0.95 Warning Period

29 CM Task Optimisation formula MIL-STD-2173AS n = ln -MTBF T * C i (Cnpm Cpf)*ln(1- ) ln(1-1 August 2017 Interlogis Consulting Page 29

30 1 August 2017 Interlogis Consulting Page 30 Impact of task effectiveness How many times do I need to do a 50% effective task to achieve a 95% outcome

31 Examples of human error/violation rates - Reason Task Error Scenario 1 Unfamiliar activity Performed at speed No idea of consequence 1 2 Violation Type 1 Compliance unimportant Easy to violate Low likelihood of detection 1 3 Task Error Scenario 2 Routine Highly practiced Rapid delivery 1 50 Violation Type 2 Compliance important (legal) Low chance of detection 1 30 Low skill Task Error Scenario 3 Very familiar Well designed Highly practiced routine Violation Type 3 Culturally unacceptable Low likelihood of detection Low likelihood penalty Trained and motivated deliverer Time available to correct errors 1 August 2017 Interlogis Consulting Page 31

32 1 August 2017 Interlogis Consulting Page 32 Sample CM Assessments Cost of Function $140,000 $120,000 $100,000 $80,000 $60,000 $40,000 $20,000 Variables 0 Cost of examination $40 MTBF mths 60 Task effectiveness % 95% Cost of Failure (Cond) $1,500 Cost of Failure (Funct) $50,000 Population 100 Warning period mths 12 Cost of Examination/year Optumim Number of exams 2.20 Cost of Optimum Conditional Period failures/year Mths 5.46 Cost of Functional Failures/year Days 166 Total cost Cost of Examination/year 1 Cost Cost of Examinations/Yr of Conditional failures/year 1 $8,797 Cost Cost of Conditinal of Functional Failures/yr Failures/year 1 $29,959 Cost Total of Functional cost 1 Failures/Yr $1,507 Total Cost/Year $40,262 $ Examination Period Mths Number of Functional Failures/Yr 0.03 Number of Conditional Failures/Yr Failures/Yr Activity 1.1

33 1 August 2017 Interlogis Consulting Page 33 Planned maintenance opportunities Resistance to failure 380 Conditional Failures (95%) Degrading Asset Condition Conditional Defect Point 12 Conditional Failures (3%) 20 Items 20x20 Items 8 Items 0% Time Warning Period 1.6 x Task period = Warning period

34 1 August 2017 Interlogis Consulting Page 34 Caveats and assumptions The warning period (T) is consistent If highly variable, constant auto monitoring and shutdown Success probability is consistent over T Conservative assumption as success improves closer to failure Warning period (T) is less than MTBF/5 If T becomes larger then process approaches wear out Success probability is less than 1 Examples of extremes (70% to 99%) Candidate arrivals across T are random Fewer candidates as failure approached Resistance to failure Degrading Asset Condition Conditional Defect Point 380 Conditional Failures (95%) 12 Conditional Failures (3%) 20 Items 20x20 Items 8 Items 0% Time Warning Period 1.6 x Task period = Warning period

35 1 August 2017 Interlogis Consulting Page 35 Condition Monitoring methods matrix Source NASA RCM Guide

36 1 August 2017 Interlogis Consulting Page 36 Selecting condition monitoring process Pole mounted substations what is most cost effective approach. Hands on examination Use of thermography

37 1 August 2017 Interlogis Consulting Page 37 Condition Monitoring Verifying your task estimate Figure 1 CF Verification Graph CM Optimisation Graph (CF interval Vs Exam success) (annual exam cost Vs task interval) Activity 1.2

38 Session 4 Failure Finding What is may failure finding period?

39 1 August 2017 Interlogis Consulting Page 39 Failure finding task frequency Is a condition monitoring task applicable and effective Model Is a scheduled restoration task applicable and effective Is a scheduled discard task applicable and effective Primary Item Protective Item Adverse Event LOC Possible Outcomes Is a failure finding task applicable and effective Cost Profile $ Maintenance Cost Total Cost of Task Freq Cost of Failures Redesign or Run to failure Optimum Task Frequency

40 1 August 2017 Interlogis Consulting Page 40 Functional check sample outcome Method 1 MTBFF mths 120 = 1 in 1,861 per year Q MTBFF 120 UAo LOCE Prob Test Mths 4 Additional 0 Protection

41 1 August 2017 Interlogis Consulting Page 41 Failure Finding model Method 2 System Primary Fix Timeline Time between failures Protective Fail Fix Fail Failed Failed Check Period X+1 Check Period X+2 Check Period X+3 Check Task Check Task Task Effectiveness Check Task Multiple Failure

42 FET Failure finding model Method 2 Primary Item Low Impact - high probability Possible Protective Item and LOCE (Energy) or Outcomes Mid Impact - mid probability High Impact - low probability 1 August 2017 Interlogis Consulting Page 42

43 1 August 2017 Interlogis Consulting Page 43 Sample outcome Method 2 Fault - Event Tree Primary MTBF (mths) 120 Protective MTBF (mths) 120 Number of Protective Elements/Primary 1 Cost of Functional Test $200 Cost of Primary System Repair $2,000 Cost of Protective Element Repair $1,000 Probabilistic Cost of a Functional Failure $200,000 Population of Primary Elements 50

44 Thank you for your interest