Human Error In Maintenance Computer Science Essay

Human Error In tending Computer Science try outHuman misapprehensions maybe categorized under six groups with enjoy to engineering origination errors, assembly errors, deftness errors, inspection errors, operating errors and caution errors. alimony error is the result of the wrong pr level(p)tive or stamping ground maneuvers carried out by the foxiness or assigned military unit. Base on the frequency of tending universe get alonged the prob might of man error increases.To tame some kind-hearted errors maintain business leader is important in the design variant of a comp angiotensin converting enzyment or governance. Maintainability according to Ebleing is defined as the probability that a failed arrangement or broker bequeath be restored or repaired to a specified retard within a gun consign of eon when aid is effected in accordance with prescribed procedures. Dhillon describes maintainability as the measure taken during the development, design and inst o n the wholeing of a manu accompanimentured product that reduces the necessitate guardianship, man hours, tools, logistic cost, skill levels and facilities and ensures that the product meets required mean employ.The interactions with domain during the design, installation, production and bread and butter stages be extremely important. In some phases these interactions may vary depending on the product, scarcely be subject to deterioration delinquent to kind error.With respect to engineering products, Meister describes human error as the trouble to carry out a specified caper or forbidden action that could result in disruption of scheduled operations or damage to property and equipment.This paper looks at the human errors in maintenance practises.2.0 General Human Factors in MaintenanceFrederick Taylor was one and only(a) of the earlier pile to analyze human computes seeking to improve design and increase productivity. In maintenance, dodgings may fail for numerous r easons, one key element being human factors and errors during the design phase. According to Nertney Et al, the undermentioned be a make of different human behaviours deal have a tendency to use their hands for examining and testing raft get easily confuse with unfamiliar thingsPeople argon too impatient to take the distract amount of sentence for observing precautionsPeople grow accustom to certain warps having certain meaningsPeople sometimes overestimate short distances and underestimate horizontal or large distancesPeople may become complacent and less cargonful after successfully handling hazardous distri providedor points over a lengthened periodPeople tend to estimate speed or clearances poorlyPeople responds irrationally in emergenciesInstructions and labels ar read fallaciously or overlookedAttention is drawn to loudness, flashing lights, lurid and vivid coloursPeople have teensy enjoyledge of their physical limitationsPeople fail to recheck work for errors aft er performing a procedureThey argon reluctant to admit errors or mistakes and they do not see objects clearlyPeople get distracted by certain aspects of a product throwPeople usually expect valve handles and faucets to rotate counter-clockwise for increasing flow of a liquid steam or gasPeople carry out trade union movement (maintenance) while thinking around other thingshttp//www.iru.org/ pix chest/irupolicies/graph-etac-en_1.gifFigure2.1 Human Senses and CapabilitiesThe five human senses are touch, smell, taste, visual and hearing. In maintenance, visual, smell, touching and hearing are the more common of the human senses being utilized.2.1.1 HearingThe ability of human to hear is an important factor in maintenance work. When pattern for maintainability, excessive noise may lead to problems such as the consume for intense concentration, a reduction in workers efficiencies, disoriented of hearing, unwanted effects on the tasks being performed.2.1.2 orderSight is stimulated b y electromagnetic radiation of certain wavelengths. This is measured on the electromagnetic spectrum for visible light. The human eye is sensitive to greenish-yellow light and it sees it differently from different angles.The following are some facts about the human eyeNormally, the eye fire perceive all colours when looking straight ahead.As the viewing angle increases, colour perception decreases signifi screwtly. When there is poor lighting it may be unfeasible to de stipulationine the colour of a pocketable point of light source. The source usually appears white.When designing components, designers should account colours such that weak colour people do not get confused. An example is to use red filter with a wavelength greater than 6,500 , and try to avoid placing too emphasis on colour when critical tasks are to be performed by tired effect.2.1.3 TouchTouch complements a human ability to interpret visual and audio. Touch maybe used to relieve the eyes and ears of the load. The sense of touch has been used for centuries in technical work. For example, touch has been used for detecting surface irregularities and roughness.2.2 Ergonomic PrinciplesThe subject addresses human to system interface issues also called human engineering or engineering psychology. In addition to considering the human to system interface, ergonomics is also concerned withHuman dimensionThe working environment and its effect on humansEffects of systems on humanshttp//www.omron-ap.com/technical_guide/safety_component/safety_component_12.gifFigure3.0 Maintenance ErrorsHuman errors in maintenance occur for a number of reasons. In realise 3, a list of different reasons is shown for errors with respect to maintenance. Studies have shown a compulsive cor similitude between task performance and amount of time in a career field, ability to handle responsibility, morale and years or experience. engageers who possess these skills are ranked higher and kit and boodle are generally throu gh with(p) faster and with fewer errors.Figure Reason for Human Errors3.1 Inadequate training and ensure break awayers who are inadequately trained and lack the experience on a machine or component will most likely make errors when performing maintenance tasks. They will spend additional time trying to understand what to do rather than effective execution of the task. Errors such as correct leave out down procedures, tightening of bolts, correct alignment of components may be done wrong and adversely affecting production, increasing maintenance cost as maintenance work may need to be iterate and loafer be a safety risk to the maintenance forcefulness, operator, or the equipment.3.2 shortsightedly Written Maintenance ProceduresDue to poorly written procedures, there could be cases of components going in wrong place or new components being incorrectly installed. This as with the previous reason can cause harm to craft personnel, operator or the machine. Tasks will take longer b ecause the craft personnel following the procedure will have to spend more time figuring out what to do rather than carrying out the task in a timely and effective manner.3.3 Fatigued Maintenance forcefulnessA fatigued maintenance personnel is a receipt for disaster. The personnel will lack concentration and will miss excusable details of the work. at that place will be general tendency to rush the job in attempt to finish fast increasing the probability of errors. This may be influenced by the time of the day, stresses (physical, drug, social, personal)http//elsmar.com/Error_Proofing/img014.jpgFigure3.4 composite appoint Maintenance TaskComplex and tedious maintenance task may be subject to human errors because of the high levels of concentration required. Humans usually have a low attention span and works requiring excessive hours of concentration may have errors induced. Such jobs should be done in teams so that if one personnel makes an error it can be corrected by other me mbers on the job.3.5 Improper Work ToolsA job requiring a specific tool should not be substituted with an inferior one. An example of this is when a specified torque may be required on a bolt or methamphetamine hydrochloride requiring a torque wrench or spanner to achieve a level of precision and verity and a regular wrench or spanner is used. This may cause misalignment, et cetera.3.6 Poor Work LayoutPoor work layout is inefficient and can cause errors to be made by the maintenance personnel.3.7 Poor Work EnvironmentA poor work environment will cause discomfort to the maintenance personnel such as humidity, lighting and heat. Concentration levels will be low and there will be a rush to complete the task.3.8 Poor Equipment seeIn some equipment, components may be onerous to r all(prenominal) to perform the necessary works. Errors may be caused in the process as the tasks may not be carried out completely.3.9 Outdated Maintenance ManualsIt will be extremely rocky for maintenance personnel to follow out-dated maintenance manuals. In such an instance, the procedure will most times be incorrect inducing a number of errors in the job.3.10 Factors Contributing to Human ErrorReason and Hobbs have studied and researched the psychological and physiological factors that contribute to inescapable human error. These will includeDifferences between the capabilities of our long term memory and our conscious workspace. Attention span is limited if it is focused on one thing. Also we can only attend to a very small proportion of the total available sensory culture we receiveUnrelated matters tend to capture our attentionConcentration is hard to maintain for lengthy periods of timeThe ability to concentrate depends strongly on intrinsic capability of the current object attention universal actions are done will less attention than normalThe justifiedly balance of attention is required to correctly perform a taskThe vigilance decrement- inspectors miss speck because it may become surplus after doing it for a long periodThe level of arousal- too much or too little impairs work outputBiases in thinking and decision makingConfirmation bias where we seek education that confirms initial diagnosis of a problemEmotional decision making is when a situation is thwarting then an aggressive approach shot is inducedhttp//www.lifetime-reliability.com/images/wrongs-humans-do-to-machines.gifFigure Human Maintenance ErrorsBase on the same factors contributing to maintenance errors, the following are the most common types of errorsRecognition nonstartersThese include misidentification of objects, signal and messages and non spying of problem states.Memory failuresInput failures- Insufficient attention is to the to-be-remembered item.Storage failures- remembered material suffers interferenceOutput failures- things that we know cannot be recalled at the required timeOmissions following interruptionsPremature Exists- End a job in front all tasks are completeS killed- ground SlipsUsually associated with routines and they can includeBranching errors- an error made based on a custom and not knowing when to deviate.Over shoot Errors- having an intention but forgetting to do itRule base MistakesMisapplying a Good Rule- using a right rule in a wrong situationApplying a bad rule- unwanted consequences in using a rule even though the job will be done.Knowledge Based ErrorsIt is common when someone is doing a task for the first time but not always the case.ViolationsPurposeful acts which violates procedures. These may beRoutine violations- done to avoid unnecessary effort, gets the task done quickly, to demonstrate skill or avoid what is seen as an unnecessary laborious procedure.Thrill seeking violations- often committed in order to avoid boredom or win peer praiseSituational violations- these exist because it is not realizable to get the job done if procedures are strictly adhered to.Figure Summary of main error types4.0 Mitigation/Reduction of Hum Errors in MaintenanceIt is impossible to total alleviate all human errors when it comes to maintenance, but Engineers and designers have worked together and is continuing to take place ways to reduce some human errors. However a lot of the responsibility is on the maintenance personnel to ensure that maintenance tasks are carried out effectively. This chapter looks at ways to reduce human errors in maintenance.4.1 Avoid Unnecessary Preventive MaintenanceOver maintaining equipment, not only wastes time and money but it also increases the risks of environmental incidents but also causes expensive and unnecessary failures. Reliability Centred Techniques such as Failure Mode and wee-wee Analysis, Fault Tree Analysis and others can be useful eliminating unnecessary maintenance works and optimizes and streamlines the equipment healthful maintenance.4.2 StandardizationAnkenbrandt et al noted that standardization is the attainment of practical uniformity in product design. Non-sta ndard equipment or component lessens the reliability and increases maintenance. Standardization restricts the number of components equipment will require.The advantages of standardization according to Dhillon areReduction of using the incorrect splitReduction in wiring and installation errors due to the fact of variations in characteristics of similar itemsElimination for the need for special segmentationsReduction of incidents because of the use of wrong or unclear proceduresReduction in design time, manufacturing cost, and maintenance costReduction of procurement, stocking and trainingFigure 7 shows the goals of standardization.Figure Goals for reducing errors4.3 ModularizationModularization deals with a production into physically and functionally distinct units to allow removal and reclamation. The following are guidelines for the usefulness associated with standard unitsAim to make modules and cases as uniform as possible with respect to size and shapeDivide the equipment o r item under consideration into many modular unitsAim to make each module of being inspected independentlyDesign the equipment so that a integrity person can replace a failed part with ease and also parts should be small for mobilityModule should be designed for maximum ease of operational testing when it is removed from the actual equipment or system.Consider design, modularization and material problems simultaneouslyFor ease of disconnection, design components with see levers and linkages to allow easier replacement.4.4 Simplification and availabilityDesign engineers should consider simplification in the design phase and it should be constant. Consideration should also be taken with the important functions of a system or a product into the design itself.Accessibility is the ease with which an item can be reached for repair, replacement or servicing. Poor botheribility will result in sub-standard maintenance. Accessibility is affected byThe visual needs of personnel performing maintenance task,The location of an item and its environment. outmatch to be reached to access the component or partThe types of maintenance to be performed through an access point or openingThe danger associated with use of an access openingThe clothing worn my maintenance personnelThe task required time for executionThe types of tools and accessories required to perform taskMounting of items behind the access pointWork clearance to carry out task4.5 Interchangeability and assignmentInterchangeability refers to as an intentional aspect of design, that any component can be replaced with a similar item. This is achieved through standardization. There are three basic principles for interchangeableness according to the Department of Defence (DOD)In items, components and products requiring frequent servicing, replacement of parts, each part must be interchangeable with another similar partLiberal valuation account must existStrict interchangeability could become uneconomical in items that are expected to hold out without replacement.The following considerations are taken to achieve maximum interchangeability of partsExistence of functional interchangeability when physical interchangeability is a design characteristicSufficient information in task argument and number plate identification should be available for allowing users to decide confidently whether two similar parts are interchangeableNo change in method of connecting and mounting when there are part or unit modificationsAvoid or stay away from differences in size, mounting and shapeavailableness of adapters for making physical interchangeability possible when total interchangeability is not practicalThere should be and identification system for total interchangeability of identical parts4.5.1 IdentificationIdentification is concerned with labelling or making of parts, controls and test points to facilitate tasks such as repair and replacement. Maintenance task becomes more difficult when parts and comp onents are no properly identified. It usually takes longer and increases the risk of human induced errors. Identification could be for parts or component or equipment identification.4.6 Task AnalysisThe task analysis is a formal methodology derived from systems analysis which describes and analyse performance demands made upon humans within a system. The ride is to achieve integration of humans and machine system components.5.0 Assessing the Risk in MaintenanceRisk assessments of all human activities have great importance for the prevention of major accidents. The risk with respect to human errors when traffic with maintenance needs to be assessed and rank based on the overall partake the risk can have on the operation of the organization.The Risk Management Framework used is shown in Figure 8.0 This schedule was utilized to conduct a risk assessment and evaluation before and after the risk control measures have been put in place. The main aspects of the Risk Analysis procedure arei. Identify latent Hazards and existing risk control or safeguards.ii. Estimate the consequences of the potential Hazard.iii. Estimate the frequency of each of the impact/consequence of the potential hazard.iv. discover the Risk without considering any new risk control or safeguardsv. Determine the Risk with designd new safeguardvi. Evaluate Economic impact of proposed new safeguardvii. Optimize and propose additional modification.Figure Risk Management FrameworkAs indicate in the previous chapter (3), each human error identified will have to be ranked via a metric scaling system to determine the hierarchy of the error. The impact of these errors will have to be taken into consideration with respect to the employees (operators and maintenance staff), the equipment and the environment.Figure Diagram Showing Contributors of Risk6.0 Human Errors in Maintenance in diligenceHuman error in maintenance exists in some form or the other in all industries. However, in some industries the consequences of human error from maintenance task can be catastrophic. Industries such as nuclear plants and civil aviation cannot afford errors.6.1 Human Maintenance Errors in Power multiplicationHuman factors play an important role in power plant maintenance because improving the maintainability design of power plant facilities, systems and equipment assists to improve direct and indirect plant productivity, availability and safety. According to Seminara power lost can cost between US $500,000 to 750,000 dollars a day. The following are human related deficiencies in maintenance of a power plantLimited access or inadequate clearance to perform maintenanceEquipment poorly designed to facilitate maintenance activity effectivelyEquipment Inherently unreliablePersonnel safety hazardImpaired mobility for equipment and personnelMiscellaneous- lack of standardization, high temperature environment and poor air learnWhile maintenance activities of nuclear power plants are essential fo r sustaining the safety of a power plant and maintaining the reliability of plant systems and components, they also have potential of human errors leading to unplanned reactor charges or power derate (Dhillon 2006). J. Reason classifies in chapter 3 the different characteristics of human errors that will be applicable to Power Plants. According to Kim et al, incidents fields in Korea stated that most of the human related unplanned reactor trip events during the normal power operation are associated with test and maintenance activities (63%). Plant maintenance included preventive maintenance, planned maintenance and corrective maintenance.6.2 Human Error in AviationDue to the increase in air travels, airlines spend billions of dollars in maintenance annually. A study done in the United estate has shown that between 1990 to 2000 maintenance errors per million flights has doubled (ICAO)According to the ICAO there are over 300 factors and influences that can impact the performance of maintenance personnel. Some of the human errors that are impacted by maintenance are listed in chapter 3 and range from time pressure, inadequate training to outdated maintenance manuals.There are many categories of human errors with respect to aviation maintenance and inspection. Some of the major ones encountered according to Latorella et al areIncorrect assembly sequenceProcedural defectsWrong partIncorrect configurationMissing partDefective partFunctional defects and tactical defectsFigure List of Errors in Aircraft MaintenanceFigure 10 shows the guideline covered in aviation. Two important guidelines concerning design areSeek relevant information on human error occurrence during the maintenance phase as inputs in the design phaseEnsure that manufacturers give attention to maintenance related human factors during design phaseAccording to throng Reason based on a Boeing study which indicated the top seven causes for in-flight engine shut downs on the Boeing aircraft were as foll owedIncomplete Installation (33%)Damaged on installation (14.5%)Improper Installation (11%)Equipment not installed or missing (11%)Foreign Object Damage (6.5%)Improper fault isolation, inspection and test (6%)Equipment not unrestrained or deactivated (4%)From the statistics presented only one cause was unrelated to maintenance activities. Maintenance activities were responsible for approximately 80% of in-flight engine shut downs.7.0 Prediction Models for Human ErrorsHuman error can be analysed by some(prenominal) methods developed over the years. Some of the following methods are relied on heavily in the aviation industry.7.1 Cause and Effect DiagramsThis is a useful tool to determine root causes of specified problem in relation to maintenance errors. Related and relevant ideas are generated. The extreme right of the diagram patch up effect and to the right are all the possible causes. The cause and effect can be generated in the following moveDevelop problem statementBrainsto rm to identify possible causesEstablish major causes categories by stratifying into inwrought and process stepsConnect diagram to all the causes by following the appropriate process steps and filled in the effectsRefine cause categories by asking What cause this and Why does this condition exists?7.2 Error Cause Removal Program (ECRP)This was developed to reduce the occurrence of human error to a tolerable level in production operation. It focuses on preventive measures rather than remedial ones. It is composed of a team of workers with each team having its own coordinator with the necessary skills. Each team member presents a report and the coordinator discusses these reports in a periodic meeting and recommendations are made to management.7.3 Fault Tree AnalysisThe fault tree analysis (FTA) is used to perform reliability and safety analyses of engineering system and can be use to perform analysis of human error in maintenance.7.4 Markov AnalysisThis method is used to perform reli ability analysis of engineering systems and can be used to predict the probability of occurrence of human error in maintenance. This is done through mathematical modelling.7.4.1 Model 1This mathematical model indicates a system that can fail due to maintenance error or other failures. See figure 11. Numerals in box, circle and diamonds represents system states. The following assumptions are made for this model.The system can fail due to maintenance error or failure other than maintenance errorThe failed system is repaired and maintenance is performed periodicallyFail system repair rates are constantThe repaired system is as good as newFigure Markov Model 1 Diagram7.4.2 Model IIThis mathematical model represent a system that can only fail due to non maintenance related failures but its performance is degraded by the occurrence of maintenance error. See figure 12. The numeral in circle, box and diamonds represents system states. The following assumptions are made for this modelThe tot al or partially failed system is repaired and preventive maintenance is performed regularlyThe occurrence of maintenance error can only lead to system degradation but not failureThe system can fail from its degradation mode due to failures other than maintenance errorsThe system is repaired at constant rates from its failed and degradation statesMaintenance error and non maintenance error failure rates are constantThe repaired system is good as newFigure Markov Model 28.0 ConclusionThis report gives a comprehensive analysis of human errors in maintenance. Human errors are inevitable and there are numerous factors that can influence these errors. The first step is to identify the different human errors that may be encountered in an industry, conduct an assessment on the errors and take necessary steps to reduce these errors. The traditional approach of dealing with human error, that is counselling and or re writing procedures may not be effective in dealing with the errors identified in this report. A more holistic approach for managing maintenance error and assuring maintenance quality techniques is the application of reliability centred maintenance and also designing for maintainability.