Investigation and Human Error

Even with the most attention to detail and quality, profiling assays encounter unexpected differences between data obtained from the same compound. These events need careful investigation. First, check whether data originated from the same batch contamination or aggregation might be the reason behind differences in data. Importantly, different salt forms should be retested as they will have variable physicochemical properties with influence on solubility, permeability, and the like. Finally, equipment and human error have to be excluded. 

The current research adopts the Human Error Risk Management in Engineering Systems (HERMES) methodology (Cacciabue 2004a,b) that conceptualizes two main streams of study. These are a Retrospective investigation of human errors within aviation maintenance contexts, focused in this research - on helicopters, and a Prospective innovation of new tools that work to prevent errors occurring. 

RCA is a structured, disciplined approach to investigating, rectifying, and eliminating equipment failures and malfunctions. RCA procedures are designed to analyze problems to much greater depth (the roots ) than merely the mechanisms and human errors associated with a failure. The root causes lie in the domain of weaknesses in management... 

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. 

A critical assembly is a split bed on which fissionable material used to mock up up a separated reactor core that is stacked half on each half. One half is on roller guides so that the two halves may be quickly pulled apart if the neutron multiplication gets too high. Use the Preliminary Hazards Analysis method described in section 3,2.1 to identify the possible accidents that may occur and the qualitative probabilities and consequences. List the initiators in a matrix to systematically investigate the whole process. Don t forget human error. 

Typically, the first phase of a comprehensive accident investigation process will involve describing the way in which the hardware, the chemical process, individual operators and operating teams are involved in the accident process. This is the domain of the structural analysis techniques and the technical analysis of the chemical process which gave rise to the accident. Analyses of human error will primarily address the interactions between hardware systems and individuals or operating teams (the first two layers... 

Three major themes have been emphasized in this chapter. The first is that an effective data collection system is one of the most powerful tools available to minimize human error. Second, data collection systems must adequately address underlying causes. Merely tabulating accidents in terms of their surface similarities, or using inadequate causal descriptions such as "process worker failed to follow procedures" is not sufficient to develop effective remedial strategies. Finally, a successful data collection and incident investigation system requires an enlightened, systems oriented view of human error to be held by management, and participation and commitment from the workforce. 

Viewed in this context, the Three-Mile Island (TMI) accident was the coup de grace for an already foundering industry. In spite of the fact that the hydrogen gas bubble that accumulated in Reactor 2 did not explode, although some contaminated gas escaped and that the commissions who investigated the accident faulted human error rather than equipment failure, TMI caused (as the New York Times... 

The overall accuracy of the predictions, assessed as the mean-fold error of prediction of the test set was 2.03, making this approach one that would possess suitable accuracy for use in drug design and human pharmacokinetic predictions. Similar methods developed separately for acids and bases showed an improvement in accuracy. This investigation also included a prediction of unbound VD, which should represent a simpler parameter to predict since it would be based only on tissue binding and not plasma protein binding. However, it is interesting to note that this approach was less accurate for this parameter, which would be unexpected. 

During this human error era thorough investigations of a series of dramatic accidents (Bhopal, Chernobyl, Herald of Free Enterprise), shifted attention more towards the events prior to the accidents and led to the conclusion that the causes concerned more than only technical and human factors. Turner (Turner, 1978), was one of the first to look beyond technical and human factors and concentrated on the sociological and... 

Once the evidence has heen collected and a timeline or sequence diagram developed, the next phase of the investigation involves identifying the causal factors. These causal factors are the negative occurrences and actions that made a major contrihution to the incident. Causal factors involve human errors and equipment failures that led to the incident, hut can also he undesirable conditions, failed harriers (layers of protection, such as process controls or operating procedures), and energy flows. Causal factors point to the key areas that need to he examined to determine what caused that factor to exist. 

Exceeding these known limits will result in unpredictable actions usually resulting in significantly reduced performance, and a resulting increase in human error. Investigators and designers should be constantly on the alert for opportunities to make a system more reliable by considering the worker-machine interface and search for every opportunity to make the system less error-prone and more error-tolerant. 

Conforming to certain expected conventions and meeting normal patterns of actions and habits can enhance human performance. The incident investigation team should be alert for built-in design deviations from normal conventions. These deviations are often an underlying cause for human error. 

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