Trevor Kletz 
Computer Control and Human Error [PDF ebook] 

Computer Control and Human Error presents accounts of various incidents at computer-controlled plants. These incidents include equipment and software faults; treating the computer as a "black box"; misjudging the way operators respond to the computer; errors in the data entry; failure to inform operators of changes in data or programs; and unauthorized interference with peripheral equipment. The discussion then turns to the use of hazard and operability studies (Hazops) to prevent or reduce errors in computer-controlled plants. The book describes the conventional Hazop as used in the process industry and an overview of the different Chazop frameworks/guidelines suggested by engineers and researchers. It then presents new Chazop methodology which is based on incident analysis. The final chapter presents reasons for failures in computerized systems, each of which is illustrated with an example. Most of the examples did not cause an actual safety problem, simply because they occurred within systems that are not safety-related. Some of these examples appear in the literature; others are from personal experience or from private communications.