1. Reliability.Asset.Integrity Center Introduction to RELIABILITY and MAINTENANCE

2. Reliability.Asset.Integrity Center  To recognize the importance of reliability  To understand the basic definitions of reliability and its measures  To understand the concept of bathtub reliability curve  To understand basic methodology in reliability analysis and its relation to maintenance Session Objectives 1-2

3. Reliability.Asset.Integrity Center  Increased concern in safety and environment  Tight profit margin  Escalating operational cost  Increased system complexity  Depletion in oil and gas resources  Increased in demand  Changes in material, operating conditions, equipment ages Highly competitive business environment Pressure Safe, Reliable, and Efficient Plant OPERATIONAL ISSUES 1-3

4. Reliability.Asset.Integrity Center Why RELIABILITY? PETROCHEMICAL BUSINESS DRIVERS ► Reduce operational cost ► Healthy, Safe and environmental friendly operation ► Maximize utilization ► Meeting operation target and customer demand ► Reduce wastes, failures and downtime ► High availability ► Continuously improve plant performance RELIABILITY DIRECTLY IMPACTS ALL THESE 1-4

5. Reliability.Asset.Integrity Center Reliability and Organization’s profitability Recent incident of oil spills in the Gulf of Mexico had caused an estimated of USD 23 Billion loss to BP What causes it? Bad cement job Failure of the shoe track barrier The negative pressure test was accepted when it should not have been Failure in well control procedures Failure in blow-out preventer failures Rig’s fire and gas system failed to prevent ignition Source: BP report, www.bp.com 1-5

6. Reliability.Asset.Integrity Center System Performance Improvement (Modarres, et al (1999)) Improve System performance Prolong the life of equipment/component Estimate and reduce Failure rate Study Reliability Engineering issues Improve Maintainability Minimize Downtime Improve Reliability 1-6

7. Reliability.Asset.Integrity Center Failure Causes for Engineering Components and Systems CausesDescriptions 1. Poor design Improper design, dimensions, tolerances, stress concentration, no interchangeability of parts 2. Improper installation Improper foundation, excessive vibration, inadequate inputs (i.e voltage etc.), wrong techniques/tools 3. Incorrect production Outdated technology, wrong equipment, lack of process control and calibrated equipment, inadequate training 4. Improper maintenance Under/over maintenance, wrong tools/technique, poor spare part management, insufficient skills and training 5. Complexity More number of components, interfaces and interconnection 6. Poor operational instruction / SOP Wrong instruction, lack of clarity, difficult to understand, poor language 7. Human error Lack of understanding of process and equipment, carelessness, forgetfulness, poor judgmental skills 1-7

8. Reliability.Asset.Integrity Center “the probability that the item will perform its required function under given conditions for the time interval”  Probability – describe stochastic (random) behaviour of occurrence of failure  Required function – the designed function of the system  Given conditions – the external condition in which the system usually operates  Time interval – the design life period of the system What is RELIABILITY? 1-8

9. Reliability.Asset.Integrity Center RELIABILITY MEASURES MEAN TIME TO FAILURE (MTTF) The average time that elapses until a failure occurs. It is for non-repairable item Example: Consider 6 similar type components have failure time of 23, 34, 32, 28, 19 and 27 days respectively MTTF = (23+34+32+28+19+27) / 6 = 27.2 days 1-9

10. Reliability.Asset.Integrity Center RELIABILITY MEASURES MEAN TIME BETWEEN FAILURE (MTBF) The average time between successive failures. It is used for repairable systems when failure rate is assumed to be constant (random failure). Fail Uptime Downtime Time (days) Example: 50306046 MTBF = (50+30+60+46) / 4 = 46.5 days 1-10

11. Reliability.Asset.Integrity Center RELIABILITY MEASURES FAILURE RATE (HAZARD RATE) Failure rate (hazard rate) is the conditional probability that a component fails in a small time interval given that it has survived from time zero until the beginning of the time interval. Note : Failure rate term has been widely used to describe reliability of both non- repairable components and repairable system. The more appropriate term for non- repairable is hazard rate, and for repairable is rate of occurrence of failure (ROCOF) time survive t +  t t What is the probability of failure? 1-11

12. Reliability.Asset.Integrity Center RELIABILITY MEASURES FAILURE RATE (HAZARD RATE) CT’D Failure rate is an important function in Reliability study since it describes changes in the probability of failure over the lifetime of the item hence the item’s reliability performance Increasing rate = reliability deteriorates Decreasing rate = reliability improves Constant rate = reliability maintains 1-12

13. Reliability.Asset.Integrity Center Bathtub curve Bathtub curve is a conceptual model of the reliability characteristics (failure rate) of a component or system over it’s lifetime. It is divided into three regions Early failures 1 Failure rate time 2 Useful life 3 Wear out 1-13

14. Reliability.Asset.Integrity Center Bathtub curve Early failures 1 Failure rate time Infant mortality or burn-in period Failure rate is initially higher due to issues such as improper manufacturing, installation and poor materials 1-14

15. Reliability.Asset.Integrity Center Bathtub curve Failure rate time 2 Useful life Failure rate is approximately constant as the failures, assumed mostly stress-related occur at random. This flat-portion of bathtub is also referred as component’s or system’s ‘normal operating life’ where realistically many components or systems spend most of their lifetimes operating 1-15

16. Reliability.Asset.Integrity Center Bathtub curve Failure rate time 3 Wear out Increasing failure rate because of degradation phenomena due to wear out. Wear out is generally caused by fatigue, corrosion, creep, friction and other aging factors 1-16

17. Reliability.Asset.Integrity Center Equipment / system useful life phase extension (Wasson, 2006) Failure rate curve – Repairable system 1-17

18. Reliability.Asset.Integrity Center Various types of Failure rate curve 1.Traditional view (random failure then wear out) Typical equipment : Belt, chains, impellers Maintenance strategy: Preventive Maintenance 2. Bathtub curve Electro-mechanical components and motors Condition monitoring 3. Slow aging (steady increase in failure rate) Turbine, engines, compressors, piping Condition monitoring 1-18

19. Reliability.Asset.Integrity Center 4. Best New (sharp increase in failure rate, then level off) Typical equipment: Hydraulic and pneumatic equipment Maintenance strategy: Condition based maintenance 5. Random failure (failure rate is constant, no age related failure pattern) Ball and roller bearingCondition based maintenance 6. Worst New (high infant mortality, then random failure) Electronics equipment /components Condition based maintenance Various types of Failure rate curve 1-19

20. Reliability.Asset.Integrity Center  Statistical concepts play critical roles in Reliability analysis/ techniques  Applications of Reliability techniques in real-world problems generally involves three main elements:  Acquisition – effective and efficient data collection  Analysis – description and analysis of data (descriptive and inferential statistics)  Interpretation of data – use the result to solve the problem Reliability Analysis 1-20

21. Reliability.Asset.Integrity Center General Methodology for Reliability Analysis Setting Objectives Estimation of Reliability Measures Definition of system and failure Data gathering Exploratory analysis Distribution Analysis Recommendations for Operation and Maintenance improvement 1-21

22. Reliability.Asset.Integrity Center Setting Objective  Clear objective is very important factor for successful reliability study  Have clear definition of the specific purpose to be achieved at the end of the analysis  The objective of the reliability study has high influence on the approach and method of modeling and analysis used  Precise objective will set proper conditions for appropriate collection of relevant maintenance data to be used in the analysis 1-22

23. Reliability.Asset.Integrity Center System Definition Example: Gas Compression Train (adapted from OREDA (2002)) System Boundary 1-23

24. Reliability.Asset.Integrity Center  Historical Data – test and field data on the same components /equipment  Vendor data – Data from manufacturer / vendor / consultant  Test data – experimental data of the parts  Operational data – Field data collected under actual operating conditions  Handbook data – theoretical data from standard engineering handbook, Reliability database i.e. OREDA, MIL-HDBK 217F  Judgmental data – information based on expert opinion inputs  Cost data – data on sales, maintenance and operational costs Source of Data 1-24

25. Reliability.Asset.Integrity Center Main categories of data for reliability analysis :  Inventory data – information on equipment related to design, operational, functional and environmental characteristics. Can be classified under equipment identification, manufacturing and design, maintenance and test, engineering and process data  Failure–event data – detailed records on failure incidents i.e. event date; duration; modes; causes; codes; severity and effect on system; downtime date and duration  Operating time data – the time and duration for each operating state i.e. operation, standby and downtime Operational Data 1-25

26. Reliability.Asset.Integrity Center Types of Data ? ? ? Complete Data Interval Censored Left Censored Right Censored (Suspension) Exact time to failure is known Item is still running at the end of observation time Failure time is only known to be before a certain time Failure time is between interval 1-26

27. Reliability.Asset.Integrity Center 1-27 Exploratory Data Analysis Common Exploratory Tools Use statistical tools and techniques to investigate data sets in order to gain insight about the data, understand their important characteristics, identify outliers and extract important factors  Histogram  Pie chart  Pareto  Box plot  Trend chart  scattered plot 27

28. Reliability.Asset.Integrity Center 1-28 Exploratory Analysis No.SubsystemCode 1Gas TurbineGT 2Centrifugal Gas CompressorGC 3Starter SystemSTS 4GearboxGB 5Fuel SystemFS 6Vibration Monitoring SystemVMS 7Anti-surge Valve SystemAVS 8Lube Oil SystemLOS 9Process and UtilitiesPRO 10Turbine Control SystemTCS PIE CHART Train 1 Train 2 PARETO Gas compression Train (overall) Example TREND 28

29. Reliability.Asset.Integrity Center Types of Configurations Series Parallel M201 Feed gas separator T202A Feed/pure gas exchanger T202B Feed/pure gas exchanger T201A T201B T201C T201D A201 Absorber T203-A T203-B T203-C T203-D M202 Feed gas separator Example RBD for Acid Gas Removal Unit 1-29

30. Reliability.Asset.Integrity Center Series Configuration Blocks are connected in a series. It can be thought of as an “OR” relationship (i.e. The system fails if A OR B fails). It implies no redundancy in the components. If units are in series, then all units must for the system to work. If any unit in the series fails, then the system fails. The reliability of the system is given by: R s = R 1 × R 2 × … × R n R1R2R3 1-30

31. Reliability.Asset.Integrity Center Reliability Calculation for Series System Calculate system reliability given R 1 = 0.90, R 2 = 0.95 and R 3 = 0.98. R1R2R3 R S = R 1 × R 2 × R 3 = (0.90)(0.95)(0.98) = 0.8379 1-31

32. Reliability.Asset.Integrity Center Reliability Calculation for Series System What is the system reliability and failure rate? Assuming that the components are having a constant failure rate. Then, the system reliability is R1R2R3 So, the failure rate for the system is 1-32

33. Reliability.Asset.Integrity Center Exercise for Series System Consider a system with three components in series. You are required to achieve a system reliability of 0.98 over a 800-hours non-stop operation. 1.What would be the target failure rate for the system? R1R2R3 1-33

34. Reliability.Asset.Integrity Center Exercise for Series System Consider a system with three components in series. You are required to achieve a system reliability of 0.98 over a 800-hours non-stop operation. 2.What would be the system MTBF be? R1R2R3 1-34

35. Reliability.Asset.Integrity Center Exercise for Series System 3.Assuming the component failures are identically distributed, a) What should be the component failure rate? b) What would be the component MTBF? c) What should be the component reliability? R1R2R3 1-35

36. Reliability.Asset.Integrity Center Parallel Configuration A system will fails when all the units fail. It can be thought of as an “AND” relationship (i.e. the system fails if 1 and 2 and … and n fail) At least one unit must succeed for a successful mission. The reliability of the system is given by: R s = 1 – [(1-R 1 ) × (1-R 2 )× … × (1-R n )] 1 2 3 n.... 1-36

37. Reliability.Asset.Integrity Center Reliability Calculation for Parallel System Calculate system reliability given R 1 = 0.90 and R 2 = 0.98. R S = 1 – [(1 – R 1 )(1-R 2 )] = 1 – [(1 – 0.90)(1 – 0.98)] = 1 – (0.10)(0.02) = 1 – 0.002 = 0.998 2 1 1-37

38. Reliability.Asset.Integrity Center Combination of Basic Configurations Any of the previous configuration types can be used simultaneously in one diagram. Consider a system having subsystems. 1 43 26 5 1-38

39. Reliability.Asset.Integrity Center Steps to calculate system reliability for combined series-parallel configuration 1.Break the system into smaller series and parallel arrangements. 2.Calculate reliability of each arrangement identified in step 1. 3.Finally, calculate R S using the reliability obtained in step 2. 1-39

40. Reliability.Asset.Integrity Center k -out-of- n Redundancy At times, a system function is such that k -out-of- n of its components need to be working for the system to function. 1 2 3 4 3/4 1 2 3 4 k/n n...... 1-40

41. Reliability.Asset.Integrity Center k -out-of- n Redundancy A node is used to signify k -out-of- n redundancy. The basic property of the node is to define the number of incoming paths that must be “Good” for the system to be “Good”. 1-41

42. Reliability.Asset.Integrity Center k -out-of- n Redundancy For n identical components (i.e. same reliability values), the system reliability is calculated as 1 2 3 4 k/n n...... Binomial distribution 1-42

43. Reliability.Asset.Integrity Center Example: k -out-of- n Redundancy A high pressure boiler is mounted with 5 identical pressure relief valves. Pressure inside the boiler is successfully controlled by any three of these valves. If the failure probability of a relief valve is 0.05, compute the reliability of pressure relief valve system. Solution: This is 3-out-of-5 system where n = 5, R = 1 – 0.05 = 0.95. 1-43

44. Reliability.Asset.Integrity Center AVAILABILITY Definition “The probability that a system or component is performing its required function at a given point in time or over a stated period of time when operated and maintained in prescribed manner” (Ebeling, 1997) 1-44

45. Reliability.Asset.Integrity Center AVAILABILITY Three Types of Availability Measures 1. Inherent, A i 2. Achieved, A a 3. Operational, A o MTBF (MTBF + MTTR) A i = MTBM (MTBM + MMT) A i = A o = Uptime (Uptime + Downtime) MTBM (MTBM + MMT + MLDT) A o = (LDT + ADT) MTBF = mean time between failure MTTR = mean time to repair MTBM = mean time between maintenance MMT = mean maintenance time MLDT = mean logistics down time LDT = logistics delay time ADT = administrative delay time Steady state availability which considers only corrective maintenance (CM) Steady state availability which include both corrective maintenance (CM) and preventive maintenance (PM) 1-45

46. Reliability.Asset.Integrity Center Operational Availability A o = UPTIME UPTIME + DOWNTIME Standby Time Operating Time Logistics Delay Time (LDT) Administrative Delay Time (ADT) Corrective Maintenance Time (CMT) Preventive Maintenance Time (PMT)  Parts availability  Waiting for items / services  locating tools  setting up test equipment  finding personnel  reviewing manuals  preparation time  Fault location time  Getting parts  Correcting fault  Test and check out  servicing  Inspection  overhaul 1-46

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48. Reliability.Asset.Integrity Center References Modarres, M., Kaminskiy, M. and Krivtsov, V. (1999) Reliability Engineering and Risk Analysis. Marcel Dekker, New York OREDA Offshore Reliability Data Handbook, 4 th Edition (2002) OREDA Participants Ebeling, C. (1997), An Introduction to Reliability and Maintainability Engineering, McGraw-Hill Companies, Inc., Boston. Wasson, C. S. 2006. System Analysis, Design, and Development. Hoboken, NJ, USA: John Wiley & Sons. 1-48