Human error types

In addition, other scholars classify the human error types related to the safety production. The earliest was used in the THERP method, which divided into Commission and Omission. The... 

The reactors were equipped with interlocks to prevent opening the reactor drain valve if the reactor was pressurized. The CSB theorized that the blaster operator believed he was at the correct reactor and the bottom valve on Reactor D310 was not properly functioning. The CSB established that bottom valve actuator air hoses were found disconnected. Furthermore the emergency air hose to bypass the interlock was comiected [8]. This is obvious part of a Human Error type incident. 

After you record the steps of the job, review each step to determine the hazards that exist or that might occur. There are several ways to identify job hazards evaluate the ways human error might contribute to a hazard, record the types of potential incidents and the physical agents involved, and make sure that procedures are clearly written. 

Two types of initiators are internal and external. Internal initiators result from failures within a plant or the plant s support utilities. Thus, vessel rupture, human error, cooling failure, and loss of offsite power are internal events. All others are external events earthquakes, tornados, fires (external or internal), and floods (external or internal). Event trees can be used to analyze either type of initiator. 

Core damage and containment performance was assessed for accident sequences, component failure, human error, and containment failure modes relative to the design and operational characteristics of the various reactor and containment types. The IPEs were compared to standards for quality probabilistic risk assessment. Methods, data, boundary conditions, and assumptions are considered to understand the differences and similarities observed. 

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. 

These explanations do not exhaust the possibilities with regard to underlying causes, but they do illustrate an important point the analysis of human error purely in terms of its external form is not sufficient. If the underlying causes of errors are to be addressed and suitable remedial strategies developed, then a much more comprehensive approach is required. This is also necessary from the predictive perspective. It is only by classifying errors on the basis of underlying causes that specific types of error can be predicted as a function of the specific conditions under review. 

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. 

A combination of on-the-job and off-the-job methods is usually the best solution in most types of training. The following factors should be examined in order to analyze the role of training in preventing human error. Team training will be considered in the social and organizational factors which follow in other sections. 

Task analysis is a fundamental methodology in the assessment and reduction of human error. A very wide variety of different task analysis methods exist, and it would be impracticable to describe all these techniques in this chapter. Instead, the intention is to describe representative methodologies applicable to different types of task. Techniques that have actually been applied in the CPI will be emphasized. An extended review of task analysis techniques is available in Kirwan and Ainsworth (1993). 

Predictive human error analysis can be performed manually or by means of a computer software package. Three types of analysis are possible within PHEA. 

At least three types of consequences are possible if a human error occurs in a task sequence ... 

The model of human error held by management and the plant culture constitutes the environment in which the data collection system operates. Within this environment, all data collection systems need to address the topics listed in Figure 6.1. These topics, from the types of data collected, to the feedback systems that need to be in place, will be addressed in subsequent sections of this chapter. 

The type of data collected on human error and the ways in which these data are used for accident prevention will vary depending upon the model of error and accident causation held by the management of an organization. This model will also influence the culture in the plant and the willingness of personnel to participate in data collection activities. In Chapters 1 and 2 a number of alternative viewpoints or models of human error were described. These models will now be briefly reviewed and their implications for the treatment of human error in the process industry will be discussed. 

This is a situation where a plant appears to be operating successfully, without a major human error problem. However, management are interested in assessing the systems in the plant from the point of view of minimizing the error potential. This type of exercise is particularly relevant for plants dealing with substances or processes with high hazard potential, for example, in terms of... 

NUMBER AND TYPE OF RECORDS About 1,000 miscellaneous failure rates, event rates, and probabilities. There is some treatment of human error probability... 

Some general types of Human Errors are also included. 

Appendix III contains failure rate estimates for various genetic types of mechanical and electrical equipment. Included ate listings of failure rates with range estimates for specified component failure modes, demand probabilities, and times to maintain repair. It also contains some discussion on such special topics as human errors, aircraft crash probabilities, loss of electric power, and pipe breaks. Appendix III contains a great deal of general information of use to analysts on the methodology of data assessment for PRA. 

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. 

A human error or reliability analysis (HRA) can be performed to identify points that may contribute to an accidental loss. Human errors may occur in all facets of a the hydrocarbon industry. They are generally related to the complexity of the equipment, human-equipment interfaces, hardware for emergency actions, and procedures for operations, testing and training. The probabilities of certain types of errors occurring are normally predicted as indicated in Table 29. Individual tasks can be analyzed to determine the probability of an error occurring. From these probabilities, consequences can be identified which detemline the risk of a particular error. 

Another type of logic tree, the event tree, is an inductive technique. Event Tree Analysis (ETA) also provides a structured method to aid in understanding and determining the causes of an incident.(i) While the fault tree starts at the undesired event and works backward to identify root causes, the event tree looks forward to display the progression of various combinations of equipment failures and human errors that result in the incident graphically. 

FIGURE 6-3. Method for determining the type of human error.<... 

When you find a human error event, the type of gate is not particularly important, because while several factors may have combined to cause the error, a different person may have made the same error with only one factor present. 

An error in an experimental measurement is defined as a deviation of an observed value from the true value. There are two types of errors, determinate and indeterminate. Determinate errors are those that can be controlled by the experimenter and are associated with malfunctioning equipment, improperly designed experiments, and variations in experimental conditions. These are sometimes called human errors because they can be corrected or at least partially alleviated by careful design and performance of the experiment. Indeterminate errors are those that are random and cannot be controlled by the experimenter. Specific examples of indeterminate errors are variations in radioactive counting and small differences in the successive measurements of glucose in a serum sample. 

Why do we need to perform DQA The need for DQA arises from the very existence of total error. The collection of planned data may go astray due to unforeseen field conditions, human errors or analytical deficiencies that may alter the type, quality, and quantity of the data compared to what has been planned. We use DQA as a tool that enables us to evaluate various components of total error and to establish their effect on the amount of valid and relevant data collected for each intended use. 

Though human error is usually the cause, proper method development can make a difference in reducing this type of error or variations. First, a large volume of IS, such as 200 pL should be used when it is added by a repeater pipette because small volumes (such as 50 pL or less) are more prone to imprecision than large ones. In addition, it would be extremely difficult to visually spot missed or doubled addition for an internal standard when its volume is much smaller than that of samples and/ or other reagents (e.g., buffer). Second, it would be helpful to reduce errors by adding the usually colorless IS solution first and then incurred samples, which are usually colored, such as slight yellowish for plasma samples or dark red for whole blood samples. 

Although it was implied, the investigation report did not specifically state that there was also human error on the part of the piping designer/installer that contributed to the deceptive appearance and by the people who reviewed the installation. These types of situations cannot be seen on P IDs. Piping systems and situations that appear counterintuitive can yield mistakes more easily. 

Figure 6.1 summarises the relationship between Lucas (1992) types of organisational safety culture and their predominant model of human error on one hand, and Westrum s (1988) tripartite division of organisations on the other. 

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