Human errors definition

Lack of consistent human error definition. Human error is defined in many similar yet distinct manners, thus resulting to the lack of a consistent approach for identification and, consequently, taking of response measures. 

As microprocessor-based controls displaced hardwired electronic and pneumatic controls, the impac t on plant safety has definitely been positive. When automated procedures replace manual procedures for routine operations, the probability of human errors leading to hazardous situations is lowered. The enhanced capability for presenting information to the process operators in a timely manner and in the most meaningful form increases the operator s awareness of the current conditions in the process. Process operators are expected to exercise due diligence in the supervision of the process, and timely recognition of an abnormal situation reduces the likelihood that the situation will progress to the hazardous state. Figure 8-88 depicts the layers of safety protection in a typical chemical jdant. 

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. 

Each binary fork is attached to a branch of the preceding fork and is conditioned by the success or failure represented by that branch. Thus, evei7 fork, represents conditional probability. Each limb of the HRA event tree is described or labeled, in shorthand. Capital letters (A) represent I ailure lower case letters (a) represent success. The same convention applies to Greek letters, which represent non-human error events, such as equipment failures. The letters S and F are exceptions to this rule in that they represent system success and failure respectively, in practice, the limbs may be labeled with a short description of the error lo eliminate the need for a legend. The labeling format is unimportant the critical task in developing HRA event trees is the definition of the events themselves and their translation to the trees. 

A single, all-embracing definition of human error is difficult to achieve. For the engineer, the worker in a system such as a chemical process plant may be... 

The analysis of accidents and disasters in real systems makes it clear that it is not sufficient to consider error and its effects purely from the perspective of individual human failures. Major accidents are almost always the result of multiple errors or combinations of single errors with preexisting vulnerable conditions (Wagenaar et al., 1990). Another perspective from which to define errors is in terms of when in the system life cycle they occur. In the following discussion of the definitions of human error, the initial focus will be from the engineering and the accident analysis perspective. More detailed consideration of the definitions of error will be deferred to later sections in this chapter where the various error models will be described in detail (see Sections 5 and 6). 

PROBLEM DEFINITION. This is achieved through plant visits and discussions with risk analysts. In the usual application of THERP, the scenarios of interest are defined by the hardware orientated risk analyst, who would specify critical tasks (such as performing emergency actions) in scenarios such as major fires or gas releases. Thus, the analysis is usually driven by the needs of the hardware assessment to consider specific human errors in predefined, potentially high-risk scenarios. This is in contrast to the qualitative error prediction methodology described in Section 5.5, where all interactions by the operator with critical systems are considered from the point of view of their risk potential. 

Human Error Probability The probability that an error will occur during the performance of a particular job or task within a defined time period. Alternative definition The probability that the human operator will fail to provide the required system function within the required time. 

Fault tree analysis is based on a graphical, logical description of the failure mechanisms of a system. Before construction of a fault tree can begin, a specific definition of the top event is required for example the release of propylene from a refrigeration system. A detailed understanding of the operation of the system, its component parts, and the role of operators and possible human errors is required. Refer to Guidelines for Hazard Evaluation (CCPS, 1992) and Guidelines for Chemical Process Quantitative Risk Assessment (CCPS, 2000). 

Despite all safety precautions, equipment failure, human error and other external events can sometimes lead to increased pressures beyond the safe levels, resulting in a relief event. These possible events are described above, but what are the potential lines of defence and why use relief systems which go beyond the simple use of an SRV The SRV is in fact only a part of the relief system and definitely the most important one. 

In this very simple example, we can calculate the effects directly from their definitions. This procedure, however, becomes very laborious and subject to (human) error as the number of factors increases. In this section, we present an alternative procedure that can be used to calculate any effect with little difficulty, no matter what the design size is. 

Based on the above analysis, the paper give a new definition for accidents category, that is. All coal mine accidents can be divided into 4 categories, that is, accident is directly caused by human error, we called it A class accident accident is caused by human error and object misconduct, we called it B class accident accident is caused by human error and environment degradation, we called it C class accident accident is caused by human error, object misconduct, environment degradation in the same time, we called it D class accident. So, we can say, human error is the ultimate reason of all accidents, and it is the essence of coal mine accident human error model. 

The concept of the "well designed system" was also presented in Chapter 3. A simplistic definition of such a system would be one where aU the techniques and measures presented in our functional safety standards to prevent systematic failures are followed. These techniques and measures are planned to significantly reduce the chance of a systematic fault to a tolerable level. Therefore, systematic failure rates caused by human error including failures due to installation errors, failures due to calibration errors and failures due to choosing equipment not suited for purpose are not included in the calculation. 

Different types of outliers need to be treated in different ways. Outliers that have occurred as a result of human error may be detected by consistency checks (or integrity constraints). If outliers are a result of human ignorance, this may be handled by including information on changing definitions as metadata, which should be consulted when outlier tests are being carried out. Outliers of distribution are usually detected by outlier tests which are based on the deviation between the candidate observation and the average of all the data values. 

Literature has many theories and concepts discussing human reliability and associated human error causal factors that always trigger incidents and accidents within safety-critical systems. The main - by definition - characteristics of such safety occurrences are their randonmess, rare predictability, sophisticated, yet vague sequence of propagation. Such characteristics can basically allow for the retrospective analysis of these occurrences and their causes at various sectors and levels within industry such that re-occurrence margins are reduced if not totally eliminated. The major drawback of such reactive treatment... 

Human error and human factors are often used interchangeably, thus creating confusion and compromising the quality of human reUabilily assessments. Therefore, defining human factors and human error is necessary to establish a basis for the discussion in the current paper. A definition of human factors, modified slightly from the UK s Health and Safety Executive (Health and Safety Executive 1999), is as follows (DiMattia 2005) ... 

Various studies have reported the occurrence of human errors in the area of laboratory testing [2,23]. For example, as per New York State laboratory regulators there were around 66% testing errors in the laboratories offering drug-screening services [23,26]. This shows that there is a definite need to improve the laboratory testing system to reduce the occurrence of human errors. 

It seems that every author on human error has his or her own definition, and they vary somewhat. Some are obscure and esoteric. Nevertheless, the many definitions... 

Trevor Kletz, in An Engineer s View Of Human Error, gives a definition that relates more precisely to the places in which people work ... 

Kletz s definition of human error fits well with this author s studies of accident reports. For simplicity and to have a terse definition of human error that relates directly to the occupational setting in which exposures to injuries and illnesses occur, I present this definition ... 

Task analysis and talk-through Performance objectives definition Performance situation specification Modelling of human performance Identification of potential human errors... 

HAZOP study for procedure This is normally a detailed method and should be properly defined. This study is usually carried out by a well-balanced team from different disciplines. The information required includes but is not limited to procedure definitions, up-to-date P IDs, and other relevant drawings and documents. Also the aim of the study (depth of study and major area of interest such as HSE, accident, etc.) needs to be well defined before starting a step-by-step procedure. Each stage/step and action is examined with the guide word to identify meaningful deviation for analysis for hazard identification. In the case of a HAZOP study for procedure, human error is an important factor. 

Three nonsafety tools are used in safety analysis failure modes, effects, and criticality analysis (FMECA) human factors analysis and software analysis. Because these techniques are extremely helpful in finding eqnipment failures, human errors, and software mistakes, safety engineers have coupled them to their safety analyses. It is definitely worthwhile to understand how these tools can benefit you. 

Hollnagel (1993) labeled errors as erroneous actions and defined an error as an action which fails to produce the expected result and which therefore leads to an unwanted consequence. Probably the most widely recognized definition of human error was offered by Reason (1990, p. 9), who formally defined human error as a generic term to encompass all those occasions in which a planned sequence of mental or physical activities fails to achieve its intended outcome, and when these failures cannot be attributed to the intervention of some chance agency. ... 

Paragraph 7.3.2.5 Definition stage Human error to be considered... 

The quote by Charles Perrow is from his seminal book Normal Accidents, published in 1984 (New York Basic Books). The many scientific and practical issues with human error have been discussed in Hollnagel, E. (1998), Cognitive Reliability and Error Analysis Method, Oxford Elsevier Science Ltd. The definition of just culture can be found at the skybrary (http //www.skybrary. aero), an excellent source of aviation safety knowledge that is also of considerable general interest. 

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