Maintenance human error

AMMP works in two complementary folds Design and manufacturing as well as workplace and maintainers orientations. Consequently, the process is intended to effectively monitor the seen and/or inherent existence of maintenance human errors causal factors... 

Table 2. Aviation maintenance human errors CFES building scheme.

Characteristics of the maintenance human errors involved in unplanned reactor trips... 

In the classification of test and maintenance human errors associated with unplanned reactor trip events, J. Reason s error classification system for basic error types (Reason 1990) was used, except for one type problems from a work method or work object . The type problems from a work method or work object was dealt with as an isolated item because this type has its own peculiarity that is difficult to assign a single basic error type. Thus, the classification system in om study is composed of four items as follows ... 

The error classification of the test and maintenance human errors involved in unplanned reactor trips showed that planning failure contributed most high to the human-related tmplanned reactor trip events (47%), and contribution of execution failure was also considerably high (33%). In the case of the problem from a work method or work object, the contribution was low against the overall events (19%) but it shows a distinctive feature that the events are strongly related to maintenance categories. Contribution of a rule violation was low as a whole. The results are summarized in Table 1. 

Execution errors take up 3 3% of the total test and maintenance human errors, as shown in Table 1. Most of the events caused by execution errors occurred during a full-power operation (17 of the 21 events 81%), and both a corrective maintenance and a periodic preventive maintenance have the most contribution of the events. While the main concern of the events caused by planning failure is on the work plan or procedure, the interest of the events caused by an execution failure is in recurrent error manifestations, or external error modes. Thus the characteristics of the execution error in the test and maintenance activities will be described from the viewpoint of error mode (manifestation) under a condition of a task performance. 

Kim, X, Park, X, Xung, W., Kim, XT. 2009. Characteristics of test and maintenance human errors leading to unplanned reactor trips in nuclear power plants. Nuclear Engineering and Design, 239 2530-2536. 

Kim, J. Park, J. 2012. Reduction of test and maintenance human errors by analyzing task characteristics and work conditions. Progress in Nuclear Energy, 58 89-99. 

Monitoring by Electromechanical Instrumentation. According to basic engineering principles, no process can be conducted safely and effectively unless instantaneous information is available about its conditions. AH sterilizers are equipped with gauges, sensors (qv), and timers for the measurement of the various critical process parameters. More and more sterilizers are equipped with computerized control to eliminate the possibiUty of human error. However, electromechanical instmmentation is subject to random breakdowns or drifts from caUbrated settings and requires regular preventive maintenance procedures. 

Another difficulty is assessing the potential for human errors. If redundancy is accompanied with increased complexity, the resulting increased potential for human errors must be taken into consideration. Redundant systems require maintenance procedures that can correct problems in one part of the system while the remainder of the system is in full operation. When conducting maintenance in such situations, the consequences of human errors can be rather unpleasant. 

The possibility of a human error in the maintenance of the process controls having consequences for the safety interlock system is eliminated. 

For many years the usual procedure in plant design was to identify the hazards, by one of the systematic techniques described later or by waiting until an accident occurred, and then add on protec tive equipment to control future accidents or protect people from their consequences. This protective equipment is often complex and expensive and requires regular testing and maintenance. It often interferes with the smooth operation of the plant and is sometimes bypassed. Gradually the industry came to resize that, whenever possible, one should design user-friendly plants which can withstand human error and equipment failure without serious effects on safety (and output and emciency). When we handle flammable, explosive, toxic, or corrosive materials we can tolerate only very low failure rates, of people and equipment—rates which it may be impossible or impracticable to achieve consistently for long periods of time. 

At one time most accidents were said to be due to human error, and in a sense they all are. If someone—designer, manager, operator, or maintenance worker—had done something differently, the accident would not have occurred. However, to see how managers and supervisors can prevent them, we have to look more closely at what is meant by human error-. 

To be able to systematically identify opportunities for reducing human error, it is useful to ask the question, What is human error One definition is that human error is an inappropriate or undesirable human decision or behavior that reduces, or has the potential for reducing safety or system performance (Rasmusssen 1979). There is a tendency to view errors as operator errors. However, the error may result from inadequate management, design, or maintenance of the system. This broader view which encompasses the whole system can help provide opportunities for instituting measures to reduce the likelihood of errors. 

Human errors Number of errors Maintenance reports, control room Inv. vrindjc test procedure. . i>(vi.un g procedures... 

In addition to these formal studies of human error in the CPI, almost all the major accident investigations in recent years, for example, Texas City, Piper Alpha, Phillips 66, Feyzin, Mexico City, have shown human error as a significant causal factors in design, operations, maintenance or the management of the process. Figures 4.4-1 and 4.4-2 show the effects of human error on nuclear plant operation. 

Systematic consideration of human error is neglected because of the belief that computerization of processes will make the human unnecessary. Experience shows numerous accidents in computer controlled plants. Human involvement in critical areas of maintenance and plant modification, continues even in the most automated processes. 

Many leaks have been discussed under other headings, including leaks that occurred during maintenance (Chapter 1), as the result of human error (Chapter 3), or as the result of overfilling storage tanks (Section 5.1). Other leaks have occurred as the result of pipe or vessel failures (Chapter 9), while leaks of liquefied flammable gas are discussed in Chapter 8 and leaks from pumps and relief valves in Chapter 10. 

The application of the science of human factors to eliminating error in all aspects of process design, management, operation, and maintenance is the focus of this work. Human error has been a major cause of almost all of the catastrophic accidents that have occurred in the chemical process industries (CPI). If one adopts the broad view of human error as being the result of a mismatch between human capabilities and process demands, then clearly management s role is critical in the following areas ... 

The incident report stated that the cause of the accident was human error. Although maintenance procedures were available, they had not been used. The... 

An opportimity for error recovery would have been to implement a checking stage by a supervisor or independent worker, since this was a critical maintenance operation. However, this had not been done. Another aspect of the unforgiving environment was the vulnerability of the system to a single human error. The fact that the critical water jacket flow was dependent upon a single pump was a poor design that would have been detected if a hazard identification technique such as a hazard and operability study (HAZOP) had been used to assess the design. 

Plants are particularly vulnerable to human error during shutdowns for repair and maintenance. Tfiis is partly due to the higher level of direct human involvement with the plant, when errors are likely if procedures and supervisory systems are poor. Errors also occur during high stress situations such as emergency shutdowns. Workers need to be trained in how to handle these situations so that less stress is experienced (see Chapter 3). 

Analysis of accidents and major losses in the CPI indicates that they rarely arise from a single human error or component failure. Often there is a combination of some triggering event (hardware or human) together with preexisting conditions such as design errors, maintenance failures or hardware deficiencies. 

In the case of a latent human error the consequences of the error may only become apparent after a period of time when the condition caused by the error combines with other errors or particular operational conditions. Two types of latent error can be distinguished. One category originates at the operational level and leads to some required system function being degraded or unavailable. Maintenance and inspection operations are a frequent source of this type of latent failure. 

HFAM has 20 groups of factors instead of the 10 general failure types of the TRIPOD approach. The reason for this is that all of the 10 TRIPOD GFTs would be applied in all situations, even though the actual questions that make up the factors may vary. In the case of HFAM, it would be rare to apply all of the factors unless an entire plant was being evaluated. HFAM uses a screening process to first identify the major areas vulnerable to human error. The generic factors and appropriate job specific factors are then applied to these areas. For example, control room questions would not be applied to maintenance jobs. 

Human error tmalysis (HEA) is a systematic evaluation of the factors tliat influence tlie performance of human operators, maintenance staff, teclmicians, and otlier persomiel in tlie plant. HEA involves the evaluation of one of several types of task analysis, which is a metliod for describing tlie physical and enviromiiental characteristics of a task along witli tlie skills, knowledge, and capabilities required of tliose who perform the task. Tliis type of analysis can identify error-likely situations tliat can cause or lead to an accident. 

Automated data acquisition The object of using microprocessor-based systems is to remove any potential for human error, reduce manpower and to automate as much as possible the acquisition of vibration, process and other data that will provide a viable predictive maintenance database. Therefore the system must be able to automatically select and set monitoring parameters without user input. The ideal system would limit user input to a single operation. However this is not totally possible with today s technology. 

Human error is frequently used to describe a cause of losses. Almost all accidents, except those caused by natural hazards, can be attributed to human error. For instance, mechanical failures could all be due to human error as a result of improper maintenance or inspection. The... 

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