Slack, Chambers and Johnston, Operations Management 5 th Edition © Nigel Slack, Stuart Chambers, and Robert Johnston 2007 Chapter 19 Failure prevention and recovery Source: Eurotunnel

Slack, Chambers and Johnston, Operations Management 5 th Edition © Nigel Slack, Stuart Chambers, and Robert Johnston 2007 Failure prevention and recovery Operations strategy Design Improvement Planning and control Operations management Failure prevention and recovery Total quality management organizes process improvement Failure prevention and recovery stop processes becoming worse Operations process improvement makes processes better

Slack, Chambers and Johnston, Operations Management 5 th Edition © Nigel Slack, Stuart Chambers, and Robert Johnston 2007 Why systems fail Design failures Facilities failures Staff failures Failures inside the operation Supply failuresCustomer failures

Slack, Chambers and Johnston, Operations Management 5 th Edition © Nigel Slack, Stuart Chambers, and Robert Johnston 2007 How failure is measured Time Failure rate ‘Infant-mortality’ stage Normal-life stage Wear-out stage

Slack, Chambers and Johnston, Operations Management 5 th Edition © Nigel Slack, Stuart Chambers, and Robert Johnston 2007 Bath-tub curves for two parts of an operation Curve A represents a part with relatively predictable failure Curve B represents a part with a more random failure pattern Time Failure rate ‘Infant-mortality’ stage Normal-life stage Wear-out stage Curve B Curve A X Y

Slack, Chambers and Johnston, Operations Management 5 th Edition © Nigel Slack, Stuart Chambers, and Robert Johnston 2007 Time Failure rate 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 Chapter 19.

Slack, Chambers and Johnston, Operations Management 5 th Edition © Nigel Slack, Stuart Chambers, and Robert Johnston 2007 How failure is detected and analyzed – in-process checks – accident investigation – failure mode-and-effect analysis – fault-tree analysis Failure detection mechanisms include: Failure analysis procedures include: – point-of-departure interview – machine-diagnostic checks

Slack, Chambers and Johnston, Operations Management 5 th Edition © Nigel Slack, Stuart Chambers, and Robert Johnston 2007 The three tasks of failure prevention and recovery Failure detection and analysis Finding out what is going wrong and why Improving system reliability Stopping things going wrong Recovery Coping when things do go wrong

Slack, Chambers and Johnston, Operations Management 5 th Edition © Nigel Slack, Stuart Chambers, and Robert Johnston 2007 Severity of consequence Effect on customer Normal operation Failure Prevention Mitigation Recovery Failure management

Slack, Chambers and Johnston, Operations Management 5 th Edition © Nigel Slack, Stuart Chambers, and Robert Johnston 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)

Slack, Chambers and Johnston, Operations Management 5 th Edition © Nigel Slack, Stuart Chambers, and Robert Johnston 2007 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)

Slack, Chambers and Johnston, Operations Management 5 th Edition © Nigel Slack, Stuart Chambers, and Robert Johnston 2007 Controlled flight into terrain Flying at wrong altitude p = 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

Slack, Chambers and Johnston, Operations Management 5 th Edition © Nigel Slack, Stuart Chambers, and Robert Johnston 2007 Failure Severity of consequence Effect on customer Normal operation Probability of failure Degree of severity Likelihood of detection Risk priority number Failure modes effects analysis

Slack, Chambers and Johnston, Operations Management 5 th Edition © Nigel Slack, Stuart Chambers, and Robert Johnston 2007 Fault-tree analysis for below-temperature food being served to customers Food served to customer is below temperature Key AND node OR node Cold plate used Plate taken too early from warmer Plate warmer malfunction Oven malfunction Timing error by chef Ingredients not defrosted Plate is cold Food is cold

Slack, Chambers and Johnston, Operations Management 5 th Edition © Nigel Slack, Stuart Chambers, and Robert Johnston 2007 A mixture of maintenance approaches is often used – in a motor car, for example Use condition-based monitoring maintenance Use run-to- breakdown maintenance Use preventive maintenance

Slack, Chambers and Johnston, Operations Management 5 th Edition © Nigel Slack, Stuart Chambers, and Robert Johnston 2007 Failure curve for two machines, A and B Machine A Machine B Probability of failure Time x y

Slack, Chambers and Johnston, Operations Management 5 th Edition © Nigel Slack, Stuart Chambers, and Robert Johnston 2007 One model of the costs associated with preventive maintenance shows an optimum level of maintenance effort Costs Amount of preventive maintenance Total cost ‘Optimum’ level of preventive maintenance Cost of providing preventive maintenance Cost of breakdowns

Slack, Chambers and Johnston, Operations Management 5 th Edition © Nigel Slack, Stuart Chambers, and Robert Johnston 2007 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 Total cost Cost of breakdowns Cost of providing preventive maintenance

Slack, Chambers and Johnston, Operations Management 5 th Edition © Nigel Slack, Stuart Chambers, and Robert Johnston 2007 One part in one process can have several different failure modes, each of which requires a different approach Cutters Shredding process Failures Time Cutter ‘wear out’ failure pattern Solution Preventive maintenance before end of useful life

Slack, Chambers and Johnston, Operations Management 5 th Edition © Nigel Slack, Stuart Chambers, and Robert Johnston 2007 One part in one process can have several different failure modes, each of which requires a different approach Cutters Shredding process Failures Time Cutter ‘damage’ failure pattern Solution Preventive damage, fix stone screen

Slack, Chambers and Johnston, Operations Management 5 th Edition © Nigel Slack, Stuart Chambers, and Robert Johnston 2007 One part in one process can have several different failure modes, each of which requires a different approach Cutters Shredding process Failures Time Cutter ‘shake loose’ failure pattern Solution Ensure correct fitting through training

Slack, Chambers and Johnston, Operations Management 5 th Edition © Nigel Slack, Stuart Chambers, and Robert Johnston 2007 What’s happened What consequences Inform Contain Follow up Find root cause Engineer out Analyze failure Plan recovery The stages in failure planning DiscoverActLearnPlan

Slack, Chambers and Johnston, Operations Management 5 th Edition © Nigel Slack, Stuart Chambers, and Robert Johnston 2007 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.

Slack, Chambers and Johnston, Operations Management 5 th Edition © Nigel Slack, Stuart Chambers, and Robert Johnston 2007 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.

Slack, Chambers and Johnston, Operations Management 5 th Edition © Nigel Slack, Stuart Chambers, and Robert Johnston 2007 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.

Slack, Chambers and Johnston, Operations Management 5 th Edition © Nigel Slack, Stuart Chambers, and Robert Johnston 2007 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.

Slack, Chambers and Johnston, Operations Management 5 th Edition © Nigel Slack, Stuart Chambers, and Robert Johnston 2007 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.