C hapter 19

1. Chapter 19 Failureprevention and recovery Source: Eurotunnel

2. Failure prevention and recovery Failure prevention and recovery Operations strategy Operations process improvement makes processes better Operations management Total quality management organizes process improvement Improvement Design Failure prevention and recovery stop processes becoming worse Planning and control

3. Failures inside the operation Supply failures Customer failures Design failures Facilities failures Staff failures Why systems fail

4. Normal-life stage Wear-out stage ‘Infant-mortality’ stage How failure is measured Failure rate Time

5. Curve A Curve B Bath-tub curves for two parts of an operation Curve A represents a part with relatively predictable failureCurve B represents a part with a more random failure pattern Normal-life stage ‘Infant-mortality’ stage Wear-out stage Failure rate X Y Time

6. Service operations, after an early stage of failure detection and improvement, may suffer from steadily rising failure rates caused by increasing complacency Early failure detection and improvement Complacency Failure rate Time Chapter 19.

7. Failure detection mechanisms include: – – in-process checks – point-of-departure interview machine-diagnostic checks Failure analysis procedures include: – accident investigation – failure mode-and-effect analysis – fault-tree analysis How failure is detected and analyzed

8. Failure detection and analysis Finding out what is going wrong and why Improving system reliability Recovery Stopping things going wrong Coping when things do go wrong The three tasks of failure prevention and recovery

9. Mitigation Recovery Prevention Severity of consequence Effect on customer Normal operation Failure Failure management

10. 3.5 inch diskette cannot be inserted unless it is orientated correctly. This is as far as a disk can be inserted upside-down. This feature, along with the fact that the diskette is not square, prohibits incorrect orientation. It is a control method. Warning lights and chimes alert the driver of potential problems. These devices employ a control method and a warning method. Poka-yoke (fail-safing)

11. Filing cabinets can fall over if too many drawers are pulled out. For some filing cabinets, opening one drawer locks all the rest, reducing the chance of the filing cabinet tipping. It is a control method. The window in the envelope is not only a labour saving device. It prevents the contents of an envelope intended for one person being inserted in an envelope address to another. It is a control method. Poka-yoke (fail-safing)

12. Controlled flight into terrain Flying at wrong altitude p = 0.001 Co-pilot fails to cross-check p = 0.01 Air traffic control fail to notice p = 0.1 Pilots ignore warning alarm p = 0.5 Cumulative probability of occurrence = one in two million Source: Empics

13. Severity of consequence Effect on customer Normal operation Failure Degree of severity Likelihood of detection Probability of failure Risk priority number Failure modes effects analysis

14. Food is cold Plate is cold Oven malfunction Plate warmer malfunction Plate taken too early from warmer Timing error by chef Ingredients not defrosted Cold plate used Fault-tree analysis for below-temperature foodbeing served to customers Food served to customer is below temperature Key AND node OR node

15. Use preventive maintenance Use run-to-breakdown maintenance Use condition-based monitoring maintenance A mixture of maintenance approaches is often used –in a motor car, for example

16. Failure curve for two machines, A and B Machine A Probability of failure Machine B y x Time

17. Total cost Cost of providing preventive maintenance Cost of breakdowns ‘Optimum’ level of preventive maintenance One model of the costs associated with preventive maintenance shows an optimum level of maintenance effort Costs Amount of preventive maintenance

18. Total cost Cost of breakdowns Cost of providing preventive maintenance If routine preventive maintenance tasks are carried out by operators and if the real cost of breakdowns is considered, the ‘optimum’ level of preventive maintenance shifts towards higher levels Costs Amount of preventive maintenance

19. Cutter ‘wear out’ failure pattern Failures Time One part in one process can have several different failure modes, each of which requires a different approach Shredding process Solution Preventive maintenance before end of useful life Cutters

20. Cutter ‘damage’ failure pattern Failures Time One part in one process can have several different failure modes, each of which requires a different approach Shredding process Cutters Solution Preventive damage, fix stone screen

21. Cutter ‘shake loose’ failure pattern Failures Time One part in one process can have several different failure modes, each of which requires a different approach Shredding process Cutters Solution Ensure correct fitting through training

22. Discover Act Learn Plan What’s happened What consequences Inform Contain Follow up Find root cause Engineer out Analyze failure Plan recovery The stages in failure planning

23. Key Terms Test Failure rate (FR) A measure of failure that is defined as the number of failures over a period of time. Bath-tub curve A curve describing the failure probability of a product, service or process that indicates relatively high probabilities of failure at the beginning and end of the life cycle. Reliability When applied to operations performance, this term can be used interchangeably with ‘dependability’. When it refers to a measure of failure, it means the ability of a system, product or service to perform as expected over time, usually expressed as the probability of its performing as expected over time.

24. Key Terms Test Mean time between failures (MTBF) Operating time divided by the number of failures; the reciprocal of failure rate. Failure analysis The use of techniques to uncover the root cause of failures; techniques may include accident investigation, complaint analysis, etc. Failure mode and effect analysis (FMEA) A technique used to identify the product, service or process features that are crucial in determining the effects of failure.

25. Key Terms Test Redundancy The extent to which a process, product or service has systems or components that are used only when other systems or components fail. Fail-safeing Building-in often simple devices that make it difficult to make the mistakes that could lead to failure; also known by the Japanese term poka-yoke. Poka-yoke Japanese term for fail-safeing.

26. Key Terms Test Maintenance The activity of caring for physical facilities so as to avoid or minimize the chance of those facilities failing. Run-to-breakdown maintenance An approach to maintenance management that repairs a machine or facility only when it breaks down. Preventive maintenance An approach to maintenance management that performs work on machines or facilities at regular intervals in an attempt to prevent them breaking down.

27. Key Terms Test Condition-based maintenance An approach to maintenance management that monitors the condition of process equipment and performs work on equipment only when it is required. Total productive maintenance (TPM) An approach to maintenance management that adopts a similar holistic approach to total quality management (TQM). Reliability-centred maintenance An approach to maintenance management that uses different types of maintenance for different parts of a process, depending on their pattern of failure.