2Risk management Operations strategy Operations management Design Operations improvement makes processes betterOperations managementOrganizing for improvementDesignImprovementRisk management stops processes becoming worsePlanning and control
3Key operations questions In Chapter 19 – Risk management – Slack et al. identify the following key questions:What is risk management?How can operations assess the potential causes of, and risks from failure?How can failures be prevented?How can operations mitigate the effects of failure?How can operations recover from the effects of failure?
4Failures inside the operation Why systems failDesign failuresFacilities failuresStaff failuresFailures inside the operationCustomer failuresSupply failures
5Infant-mortality stage How failure is measuredInfant-mortality stageNormal-life stageWear-out stageFailure rateTime
6Infant-mortality stage How failure is measured (Continued)Bath-tub curves for two parts of an operation. Curve A represents a part with relatively predictable failure and curve B represents a part with a more random failure pattern.Infant-mortality stageNormal-life stageWear-out stageCurve AFailure rateCurve BXTimey
7Early failure detection and improvement How failure is measured (Continued)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 improvementComplacencyFailure rateTimeChapter 19.
8The three tasks of failure prevention and recovery Failure detection and analysisFinding out what is going wrong and whyImproving system reliabilityRecoveryStopping things going wrongCoping when things do go wrong
9How failure is detected and analyzed Failure detectionFailure detection mechanisms include:in-process checks;machine-diagnostic checks;point-of-departure interviews.Failure analysisFailure analysis procedures include:accident investigation;failure mode and effect analysis;fault-tree analysis.
10Severity of consequence Failure ManagementPreventionMitigationRecoveryNormal operationFailureSeverity of consequenceEffect on customer
11Poka-Yoke (fail-safing) File cabinets can fall over if too many drawers are pulled out. For some file cabinets, opening one drawer locks all the rest, reducing the chance of the file cabinet tipping. It is a control method.The window in the envelope is not only a labour saving device. It also prevents the contents of an envelope intended for one person being inserted in an envelope addressed to another. It is a control method.
12Cumulative probability of occurrence = one in two million. Controlled flight into terrainWhat has to go wrong?Flying at wrong altitude p = 0.001Co-pilot fails to cross check p = 0.01Air traffic control fail to notice p = 0.1Pilots ignore warning alarm p = 0.5Cumulative probability of occurrence = one in two million.
13Failure modes effects analysis Normal operationFailureSeverity of consequenceEffect on customerProbability of failureDegree of severityLikelihood of detectionRisk priority number
14Fault-tree analysisRisk – below-temperature food being served to customersFood served to customer is below temperaturePlate is coldFood is coldCold plate usedPlate taken too early from warmerPlate warmer malfunctionOven malfunctionTiming error by chefIngredients not defrostedKeyAND nodeOR node
15Fault-tree analysis (Continued) Risk – filter not replaced when requiredFilter not replaced when requiredAutomatic cut-out failsInspection fails to detect blocked filterDisconnect function failureCut-out disconnectedSignal malfunctionInspection not carried outInspection sequence violatedParticle meter faultyKeyAND nodeOR node
16Maintenance modesA mixture of maintenance approaches is often used – in an automobile, for example.Engine – Use preventive maintenanceLights – Use run-to-breakdown maintenanceTyres – Use condition-based monitoring maintenance
17Probability of failure Failure curve for two machines, A and BMachine AMachine A – breakdown relatively predictable, so can judge when to time preventive maintenance.Probability of failureMachine BMachine B – breakdown relatively unpredictable, so is less easy to judge when to time preventive maintenance.Time
18Maintenance costsOne model of the costs associated with preventive maintenance shows an optimum level of maintenance effort.Total costCost of providing preventive maintenanceCost of breakdowns‘Optimum’ level of preventive maintenanceCostsAmount of preventive maintenance
19Maintenance costs (Continued) If 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 a higher level.Total costCost of breakdownsCostsCost of providing preventive maintenanceAmount of preventive maintenance
20Cutter ‘wear out’ failure pattern Reliability centred maintenanceOne part in one process can have several different failure modes, each of which requires a different approach.CuttersShredding processFailuresTimeCutter ‘wear out’ failure patternSolutionPreventive maintenance before end of useful life
21Cutter ‘damage’ failure pattern Reliability centred maintenance (Continued)One part in one process can have several different failure modes, each of which requires a different approach.CuttersShredding processSolutionPreventive damage, fix stone screenFailuresTimeCutter ‘damage’ failure pattern
22Cutter ‘shake loose’ failure pattern Reliability centred maintenance (Continued)One part in one process can have several different failure modes, each of which requires a different approach.CuttersShredding processSolutionEnsure correct fitting through trainingFailuresTimeCutter ‘shake loose’ failure pattern