Human Error In Maintenance Computer Science Essay

Human Error In keep Computer comprehension EssayHuman errors whitethornbe categorized under six groups with respect to engineering digit errors, assembly errors, installation errors, inspection errors, operating errors and livelihood errors. Maintenance error is the result of the wrong preventive or rep channel actions carried step forward by the craft or assigned personnel. Base on the frequency of tending being performed the chance of kind-hearted error ontogenys.To reduce well-nigh merciful errors principal(prenominal)tainability is important in the determination phase of a component or system. Maintainability consort to Ebleing is defined as the probability that a failed system or component will be restored or repaired to a specified condition within a plosive of epoch when fear is performed in accordance with prescribed unconscious serve ups. Dhillon describes maintainability as the measure taken during the development, initiation and installation of a man ufactured product that reduces the inevitable maintenance, man hours, pricks, logistic cost, skill levels and facilities and ensures that the product meets required intended use.The interactions with gentlemans during the mark, installation, production and maintenance phases are extremely important. In some phases these interactions may castrate depending on the product, only are caseful to deterioration cod to clement error.With respect to engineering products, Meister describes sympathetic error as the failure to read out a specified task or forbidden action that could result in disruption of scheduled operations or damage to property and equipment.This composing looks at the human errors in maintenance practises.2.0 General Human Factors in MaintenanceFrederick Taylor was one of the earlier people to studied human factors attempting to improve design and increase productivity. In maintenance, systems may fail for numerous reasons, one key element being human factors and errors during the design phase. According to Nertney Et al, the undermentioned are a list of different human behavioursPeople take a tendency to use their hands for examining and testingPeople get easily conf employ with strange thingsPeople are too impatient to take the appropriate amount of time for observing precautionsPeople become accustom to authoritative colours having certain meaningsPeople sometimes overestimate short distances and underestimate horizontal or large distancesPeople may become complacent and less careful by and by successfully handling hazardous items over a lengthy periodPeople tend to estimate speed or clearances poorlyPeople responds irrationally in emergenciesInstructions and labels are read in jogly or overlookedAttention is drawn to loudness, flashing lights, bright and vivid coloursPeople require little knowledge of their physical limitationsPeople fail to recheck work for errors after performing a procedureThey are reluctant to admit errors or mistakes and they do non see objects clearlyPeople get distracted by certain aspects of a product featurePeople usually expect valve handles and faucets to circulate counter-clockwise for increasing flow of a liquid steam or gasPeople carry out task (maintenance) while thinking about another(prenominal) thingshttp//www.iru.org/pix/irupolicies/graph-etac-en_1.gif envision2.1 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 innovation for maintainability, excessive noise may lead to problems much(prenominal) as the need for intense concentration, a reduction in workers efficiencies, lost of hearing, unwanted makes on the tasks being performed.2.1.2 SightSight is stimulated by electromagnetic radiation of certain wavelengths. This is me asured 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 foot perceive all colours when looking straight ahead.As the viewing angle increases, colour wisdom decreases signifi grasstly. When there is poor lighting it may be impossible to determine the colour of a small point of light source. The source usually appears white.When designing components, designers should consider colours much(prenominal) 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 personnel.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 in like manner 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.gif skeletal frame3.0 Maintenance ErrorsHuman errors in maintenance occur for a number of reasons. In figure 3, a list of different reasons is shown for errors with respect to maintenance. Studies pull in shown a positive correlation between task performance and amount of time in a career field, ability to handle responsibility, morale and years or experience. Workers who possess these skills are runed higher and works are generally done faster and with fewer errors.Figure Reason for Human Errors3.1 Inadequate reading and ExperienceWorkers who are inadequately trained and lack the experience on a machine or component will most likely make up errors when performing maintenance tasks. They will spend additional time trying to understand what to do rather than good execution of the task. Errors such as correct shut 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 repeated and sewer be a safety risk to the maintenance personnel, operator, or the equipment.3.2 distressingly indite 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 foregoing reason can author harm to craft personnel, operator or the machine. Tasks will take longer be character the craft personnel following the procedure will oblige to spend more tim e figuring out what to do rather than carrying out the task in a timely and effective manner.3.3 Fatigued Maintenance PersonnelA fatigued maintenance personnel is a receipt for disaster. The personnel will lack concentration and will drop off minor 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 Complex 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 precaution cut through with(predicate) and works requiring excessive hours of concentration may have errors induce. Such jobs should be done in teams so that if one personnel makes an error it can be corrected by other members on the job.3.5 unseemly 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 nut requiring a torque wrench or spanner to achieve a level of preciseness and accuracy 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 do 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 DesignIn some equipment, components may be difficult to r each(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 difficult 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 inevitable 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 stunning data we receiveUn related to 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 attentionHabitual actions are done will less attention than normalThe right balance of attention is required to correctly perform a taskThe vigilance decrement- inspectors miss fault because it may become redundant after doing it for a long periodThe level of arousal- too much or too littl e impairs work outputBiases in thinking and decision makingConfirmation bias where we desire information that confirms initial diagnosis of a problemEmotional decision making is when a situation is frustrating then an aggressive approach is generatehttp//www.lifetime-reliableness.com/images/wrongs-humans-do-to-machines.gifFigure Human Maintenance ErrorsBase on the aforementioned factors contributing to maintenance errors, the following are the most common types of errorsRecognition FailuresThese include misidentification of objects, type and messages and non detection 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 before all tasks are completeSkilled-based SlipsUsually associated with routines and they can includeBranching errors- a n 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 levelheaded Rule- using a right draw rein 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 supernumerary 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 hold out because it is not possible 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 e rrors when it comes to maintenance, but Engineers and designers have worked together and is continuing to find 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 Cause Analysis, Fault Tree Analysis and others can be useful eliminating unnecessary maintenance works and optimizes and streamlines the equipment preventive maintenance.4.2 StandardizationAnkenbrandt et al noted that standardization is the attainment of practical uniformity in product design. Non-standard equipment or component lessens the reliability and increases maintenance. Stand ardization restricts the number of components equipment will require.The advantages of standardization according to Dhillon areReduction of using the incorrect partsReduction in wiring and installation errors due to the fact of variations in characteristics of equal itemsElimination for the need for special partsReduction 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 replacement. The following are guidelines for the usefulness associated with modular unitsAim to make modules and parts as uniform as possible with respect to size and shape burst the equipment or item under consideration into many modular unitsAim to make each module of being inspected indepe ndentlyDesign the equipment so that a single 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 control levers and linkages to allow easier replacement.4.4 Simplification and approachabilityDesign 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 accessibility 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.Distance 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 IdentificationInterchangeability 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 interchangeability 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 tolerance must existStrict interchangeability could become uneconomical in items that are evaluate to operate without replacement.The following considerations are taken to achieve maxim um interchangeability of partsExistence of functional interchangeability when physical interchangeability is a design characteristicSufficient information in task instruction 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 shapeAvailability 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 aid tasks such as repair and replacement. Maintenance task becomes more difficult when parts and components are no properly identified. It usually takes longer and increases the risk of human induced errors. Ident ification 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 canvas performance demands made upon humans within a system. The aim is to achieve integration of humans and machine system components.5.0 Assessing the peril in MaintenanceRisk assessments of all human activities have great importance for the prevention of major accidents. The risk with respect to human errors when transaction with maintenance needs to be assessed and rank based on the overall rival the risk can have on the operation of the organization.The Risk Management Framework used is shown in Figure 8.0 This program 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 Potential Hazards and existing risk control or safeguards.ii. Estimate the consequences of the pot ential Hazard.iii. Estimate the frequency of each of the impact/consequence of the potential hazard.iv. Determine the Risk without considering any new risk control or safeguardsv. Determine the Risk with proposed new safeguardvi. approximate 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 scoring 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 IndustryHuman 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 a nd civil airmanship cannot afford errors.6.1 Human Maintenance Errors in actor GenerationHuman factors play an important role in power plant maintenance because improving the maintainability design of power plant facilities, systems and equipment assists to improve acquire 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 conditioningWhile maintenance activities of nuclear power plants are essential for 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 trips 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 reports 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 Kingdom has shown that between 1990 to 2000 maintenance errors per million flights has duplicate (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 configuration lacking partDefective partFunctional defects and tactical defectsFigure List of Errors in Aircraft MaintenanceFigure 10 shows the guideline covered in aviation. 2 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 James Reason based on a Boeing study which indicated the top seven causes for in-flight engine shut downs on the Boeing aircraft were as followedIncomplete 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 activated 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 exemplifications for Human ErrorsHuman error can be analysed by several 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 represent effect and to the right are all the possible causes. The cause and effect can be generated in the following travelDevelop problem statement brainstorm to identify possible causesEstablish major causes categories by stratifying into natural and process st epsConnect 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 computer programme (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 make up 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 concussion 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 reliability analysis of engineering systems and can be used to predict the probability of occurre nce of human error in maintenance. This is done through mathematical exampleling.7.4.1 Model 1This mathematical baby-sit 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 range 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 total or partially failed system is repaired and preventive maintenance is performed reg ularlyThe occurrence of maintenance error can only lead to system adulteration 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 assuri ng maintenance quality techniques is the application of reliability centred maintenance and also designing for maintainability.