Human error/factors

Woods, D.D. 2000a. Behind human error human factors research to improve patient safety. National Summit on Medical Errors and Patient Safety Research, Quality Interagency Coordination Task Force and Agency for Healthcare Research and Quality, September 11, 2000. www.apa.org/ppo/issues/shumfactors2.html. 

A fundamental concept of ICAM is acceptance of the inevitabiUty of human error. Human factors research and operational experience has shown that human error is a normal characteristic of human behaviour, and although it can be reduced, it cannot be completely eliminated (Helmieich and Merritt, 2000). An organization cannot change the human condition, but they can change the conditions imder which humans work, thereby making the system more error tolerant (Reason, 2000). 

Several nontechnical factors can significantly affect the results of a nondestmctive inspection. Many of these are classified as human factors (1,2,17). Operator experience affects the probabiUty of detection of most flaws. Typically, an inexperienced operator has more false rejects, known as Type II errors, than an experienced operator. A poor operator has few false rejects but is more likely to miss a defect in the inspection, known as a Type I error. Operator fatigue, boredom, or an unfavorable environment such as lighting, cold, or rain may further affect performance. Thus it usually is a good investment for the inspection company to assure that the operator environment is most amenable to inspection, that the equipment is suitable for the task, and that the operator is alert and well rested. 

Human factors are an extremely important part of inherently safer concepts. Processes should be designed to avoid error traps. Chapter 6 of this book presents a discussion of human factors as related to inherently safer design. 

From a human factors perspective, the chemistry of the process can be made inherently safer by selecting materials that can better tolerate human error in handling, mixing, and charging. If a concentrated reagent is used in a titration, precision in reading the burette is important. If a dilute reagent is used, less precision is needed. 

Human factors, discussed in Section 4.2, enter a fault tree in the same manner as a component failure. The failure of manual actions, that prevent or mitigate an accident, are treated the same as hardware failures. The human error failure probability is conditioned by performance sluiping factors imposed by stress, training and the environment. 

Human errors may be dependent on the specific accident sequence displayed in the event tree, and, for that reason, may be included in the event tree. This requires the human-factors specialist to consider the context of the error in terms of stress, operator training in response to the accident, di.tgnosiic paiierns, environmental, and other performance-shaping factors. 

The CPI would benefit from the application of human factors principles to improve safety, quality, and productivity. These arise from applying quality management to get at the underlying causc-.s of errors rather than after-the-fact blame or punishment. Crosby (1984) advocates error cause... 

There is increasing interest in human factors issues in the CPI. Kletz (1991), Lorenzo (1990) and Mill (1992) address human error in the CPI, Kletz (1994) addresses human factors through case studies. 

Quantitative assessment Determine probabilities of human errors Identify factors and interactions affecting human performance... 

Williams, J. C., 1989, A Data-Based Method for Assessing and Reducing Human Error to Improve Operational Performance, Proceedings of the 1988 IEEE Fourth Conference on Human Factors and Power Plants, Monterey, CA, June 5-9, pp 436-450, IEEE. 

This book has been written to show how the science of human factors can be applied at the plant level to significantly improve human performance and reduce human error, thus improving process safety. 

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 book begins with a discussion of the theories of error causation and then goes on to describe the various ways in which data can be collected, analyzed, and used to reduce the potential for error. Case studies are used to teach the methodology of error reduction in specific industry operations. Finally, the book concludes with a plan for a plant error reduction program and a discussion of how human factors principles impact on the process safety management system. 

Chapter 8, A Systematic Approach to the Management of Human Error, explains how the manager and safety professional can use human factors principles in the management of process safety. This chapter also provides a practical plan for a plant human error reduction program that will improve productivity and quality as well. 

The major benefits that arise from the application of human factors principles to process operations are improved safety and reduced down time. In addition, the elimination of error has substantial potential benefits for both quality and productivity. There is now a considerable interest in applying quality management approaches in the CPI. Many of the major quality experts em-... 

Despite the lack of interest in human factors issues in the CPI in the past, the situation is now changing. In 1985, Trevor Kletz published his landmark book on human error in the CPI An Engineer s View of Human Error (revised in 1991). Several other books by the same author e.g., Kletz (1994b) have also addressed the issue of human factors in case studies. Two other publications have also been concerned specifically with human factors in the process industry Lorenzo (1990) was commissioned by the Chemical Manufacturers Association in the USA, and Mill (1992), published by the U.K. Institution of Chemical Engineers. In 1992, CCPS and other organizations sponsored a conference on Human Factors and Human Reliability in Process Safety (CCPS, 1992c). This was further evidence of the growing interest in the topic within the CPI. 

The first component of the systems approach to error reduction is the optimization of human performance by designing the system to support human strengths and minimize the effects of human limitations. The hiunan factors engineering and ergonomics (HFE/E) approach described in Section 2.7 of Chapter 2 indicates some of the techniques available. Design data from the human factors literature for areas such as equipment, procedures, and the human-machine interface are available to support the designer in the optimization process. In addition the analytical techniques described in Chapter 4 (e.g., task analysis) can be used in the development of the design. 

The other global dimension of the systems approach is the need for the existence of policies which address human factors issues at senior levels in the company. This implies that senior management realizes that resources spent on programs to reduce error will be as cost-effective as investments in engineered safety systems. 

The second perspective to be considered in this chapter is the human factors engineering (or ergonomics) approach (HFE/E). This approach, described in Section 2.5, emphasizes the mismatch between human capabilities and system demands as being the main source of human error. From this perspective, the primary remedy is to ensure that the design of the system takes into account the physical and mental characteristics of the human. This includes consideration of factors such as ... 

Human Factors Engineering/Ergonomics approach (control of error by design, audit, and feedback of operational experience) Occupational/process safety Manual/control operations Routine operation Task analysis Job design Workplace design Interface design Physical environment evaluation Workload analysis Infrequent... 

In subsequent sections the application of PIFs to various aspects of error reduction will be described. One of the most important of these applications is the use of comprehensive lists of PIFs as a means of auditing an existing plant to identify problem areas that will give rise to increased error potential. This is one aspect of the proactive approach to error reduction that forms a major theme of this book. This application of PIFs can be used by process workers as part of a participative error reduction program. This is an important feature of the human factors assessment methodology (HFAM) approach discussed in Section 2.7. 

Inspection of the HRA event tree reveals that the dominant human error is Error A the operator failing to isolate the propane valves first. The other potential human errors are factors only if a propane isolation valve sticks open. Based on these qualitative results alone, a manager rrught decide to periodically train operators on the proper procedure for isolating a failed condenser and to ensure that operators are aware of the potential hazards. The manager might... 

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