1、 A Managers Guide toReducing Human ErrorsImproving Human Performance in the Process IndustriesAPI PUBLICATION 770MARCH 2001A Managers Guide toReducing Human ErrorsImproving Human Performancein the Process IndustriesPrepared under contract byD. K. Lorenzo, P.E.,EQE, International Inc.February 2001200
2、1 American Petroleum Institute, Inc.iiiNOTICEThis Guide was prepared by EQE International, Inc. (EQE), an ABS Group Company, as anaccount of work sponsored by the Chemical Manufacturers Association (now the American ChemistryCouncil) and the American Petroleum Institute (API). Neither EQE, the Ameri
3、can Chemistry Council,API, nor any of their employees, subcontractors, consultants, or other assigns make any warranty, expressor implied, or assume any liability or responsibility for any use, or the results of such use, of anyinformation, product, or process disclosed in this Guide, or represent t
4、hat its use would not infringe uponprivately owned rights.All rights reserved. No part of this work may be reproduced, stored in a retrieval system, or transmittedby any means, electronic, mechanical, photocopyi8ng, recording, or otherwise withoutprior written permission from the publisher. Contact
5、the publisher, API Publishing Services,1220 L Street, N.W., Washington, D.C. 20005.2001 American Petroleum Institute, Inc.vACKNOWLEDGMENTSThe following people are recognized for their contributions of time and expertise during this study and inthe preparation of this report:API Staff ContactWilliam
6、J. Erny, Regulatory and Scientific Affairs DepartmentDon K. Lorenzo, EQE International, author of the report, appreciates the support given to thisproject by the American Petroleum Institute and the American Chemistry Council, which published thefirst edition of this Guide. The author also gratefull
7、y acknowledges the contributions of Dr. A. D. Swainwho reviewed the first edition and originally developed many of the concepts, principles, and techniquesdescribed herein. In the first edition, the author quoted extensively from several of Dr. Swains works:Design Techniques for Improving Human Perf
8、ormance in Production (Reference 3), Handbook of HumanReliability Analysis with Emphasis on Nuclear Power Plant Applications (Reference 7), ComparativeEvaluation of Methods for Human Reliability Analysis (Reference 10), and Human Reliability inChemical Processes Training Course Notes (Reference 15).
9、 We are also indebted to the reviewers ofthis Guide at EQE International, Inc.: L. N. Vanden Heuvel, J. S. Arendt, L. K. Adair, and P. M. Hafford.And we want to thank S. C. Barnwell, A. L. Nicely, and S. B. Ross for their skill and craftsmanship inpreparing this document.viTABLE OF CONTENTSSection P
10、ageNOTICE. iiiACKNOWLEDGMENTS vPREFACE ixEXECUTIVE SUMMARY. xi1. INTRODUCTION . 11.1 Importance of Improving Human Performance 11.2 Objectives and Organization of This Guide 22. UNDERSTANDING HUMAN ERROR 52.1 Definition of Human Error 52.2 Theory of Human Error 62.3 Performance Shaping Factors . 83.
11、 STRATEGIES FOR IMPROVING HUMAN PERFORMANCE 133.1 Examples of Error-likely Situations . 133.2 General Approaches to Improving Human Performance . 254. MANAGEMENT USE OF HRA . 294.1 Definition of HRA . 294.2 Chartering the Analysis 304.3 Selecting and Applying HRA Techniques 324.4 Understanding the L
12、imitations 365. CONCLUSIONS . 37GLOSSARY 39REFERENCES 45BIBLIOGRAPHY 46viiTABLE OF CONTENTS (cont.)APPENDIX 1 Self-evaluation Questionnaire for Managers Considering Ways toImprove Human Performance 57APPENDIX 2 Self-evaluation Survey 65APPENDIX 3 Example HRA Problem Using the THERP Technique . 79LIS
13、T OF TABLESTable Page1 Opportunities for Human Error. 22 Internal PSFs 93 External PSFs . 94 Stressor PSFs 105 Elements of the Work-situation Approach. 136 HRA Motivations 297 Examples of Typical HRA Objectives. 318 Major Limitations of HRA. 369 Estimated Decreases in HEPs Resulting from Improvement
14、s in the Work Situation . 3810 Events Included in the HRA Event Tree . 8411 HRA Results. 84LIST OF FIGURESFigure Page1 Simple Model of Human Behavior as a System Component . 62 Random Error . 73 Systematic Error 74 Sporadic Error. 85 Operator as Essential Element of Overall Process System 8viiiLIST
15、OF FIGURES (cont.)6 Relationship of Stress and Performance 117 Exit Sign. 168 Vigilance Effectiveness . 239 Effects of Practice on Skills 2810 Elements of an HRA Charter 3011 Overview of HRA Methods . 3312 HRA Event Tree of Hypothetical Calibration Tasks . 3513 Typical Operator Action Tree. 3514 Pro
16、pane Condenser Schematic . 8115 HRA Event Tree for Improper Condenser Isolation 83ixPREFACEHuman errors have either directly caused or significantly contributed to many major accidents inthe process industries. The American Chemistry Council, American Petroleum Institute, and theirmember companies r
17、ecognize the importance of reducing human errors to enhance the safety,productivity, and quality of their manufacturing processes. But to improve human performance, managersneed specific advice on what can be done to help prevent mistakes and to reduce the likelihood that suchmistakes will lead to p
18、rocess upsets or accidents.This Guide is intended for an audience of middle managers to senior executives who have differentlevels of knowledge about human factors engineering. It is designed to equip them with a basicunderstanding of the causes of human errors and to suggest ways for reducing human
19、 errors at individualfacilities. It also describes how to incorporate human reliability analysis (HRA) into process safetymanagement activities. To convey this information, we use the following steps: Establish a basic vocabulary (Glossary) needed to discuss human factors engineering and HRAwith exp
20、erts in the field Identify factors affecting human performance, especially those that managers can control Suggest ways to reduce human errors Describe how HRA can be incorporated in process safety management activitiesSection 1 discusses the importance of improving human performance and also discus
21、ses theobjectives of this Guide. Section 2 defines human error and discusses its most common causes. Section 3identifies many specific factors in the workplace that increase the likelihood of human errors anddiscusses ways to improve human performance.If a manager requires a numerical estimate of th
22、e probability of human error, there are several HRAtechniques available for that purpose; Section 4 describes how these techniques can be used inconjunction with quantitative risk assessment techniques. Some concluding comments are offered inSection 5. Appendices 1 and 2 contain self-evaluation ques
23、tionnaires, and Appendix 3 contains anexample HRA.We hope this Guide will help you identify ways to reduce human errors in your own facilities.However, the extent of human factors engineering knowledge that has been accumulated far exceeds whatis contained in this Guide. An extensive bibliography ha
24、s been included to help you find additionalinformation about particular topics. You are strongly encouraged to use these resources in addition to thisGuide.xiEXECUTIVE SUMMARYDuring the past 30 years, the 100 largest accidents at chemical and hydrocarbon processingfacilities have severely injured or
25、 killed hundreds of people, contaminated the environment, and causedmore than $8 billion in property damage losses.1,2 The actual cost of these accidents was much higherbecause of the associated business interruption costs, cleanup costs, legal costs, fines, losses of marketshare, and so forth. Huma
26、n error was a significant factor in almost all of these accidents. In systemswhere a high degree of hardware redundancy minimizes the consequences of single component failures,human errors may comprise over 90 percent of the system failure probability.3Any serious attempt to improve process safety m
27、ust address the fact that human errors in thedesign, construction, operation, maintenance, and management of facilities are the root causes of almostall quality deficiencies, production losses, and accidents. Too often, managers believe that workers canbe selected, trained, and motivated to properly
28、 operate any system. Therefore, they believe that humanerrors are the result of carelessness or stupidity, and that the only way they can reduce human errors is todiscipline the guilty parties when errors occur.Enlightened managers realize that careless or unfit workers account for only a small frac
29、tion of thehuman errors at their facilities; most mistakes are committed by skilled, careful, productive, well-meaningemployees. Rather than simply blaming the individual involved, these managers attempt to identify theroot causes of the error in the work situation and implement appropriate correcti
30、ve actions.Human factors engineering, or ergonomics, is the design of equipment, operations, procedures,and work environments that are compatible with the capabilities, limitations, and needs of the workers. Itis a vital complement to other engineering disciplines that primarily seek to optimize har
31、dwareperformance and/or minimize capital costs with little or no consideration of how the equipment willactually be operated and maintained. For example, a salvaged dial thermometer attached to a nozzle justbelow the third level platform might be a very inexpensive way to accurately measure temperat
32、ure in atower. But from a human factors standpoint, it is a less-than-adequate design if operators must climb upthree caged ladders and peer down through the metal grating of the platform in order to read thetemperature (which must be controlled within 5 degrees) from a dial graduated in 100-degree
33、increments.This Guide focuses on techniques that managers can use to improve human performance byidentifying and eliminating error-likely situations that may not be as obvious as the one described above.The basic strategy is to reduce the frequency of human errors by applying principles of human fac
34、torsengineering to the equipment that must be operated and maintained, to the work tasks that must beperformed, and to the work environment. In order for this approach to be successful, it is essential thatthe workers themselves be involved in the design process. From a management standpoint, it wou
35、ld notbe cost-effective to ignore the workers knowledge, which is a valuable resource that already exists withinevery company. The earlier that workers and human factors specialists are involved in the design process,the more successful and efficient this strategy will be.xiiBecause some human error
36、s will inevitably occur, this Guide also discusses methods that managerscan use to reduce the probability that undesirable consequences will result from them. This can beaccomplished by designing ways to detect human errors or mitigate their effects. Involving the workersin this activity will also h
37、elp ensure its success.One of the tools that managers can use to improve human performance is human reliability analysis(HRA). Like other risk assessment tools (e.g., fault tree analysis), HRA can provide both qualitative andquantitative information. The qualitative results identify the critical act
38、ions that a worker mustaccomplish to successfully perform a task, identify erroneous (unwanted) actions that can degrade thesystem, identify error-likely situations, and identify any factors that would mitigate errors in theperformance of any action. The quantitative results are numerical estimates
39、of the probability that a taskwill be performed incorrectly or that unwanted actions will be performed. As mentioned in the AmericanChemistry Councils and Center for Chemical Process Safetys Evaluating Process Safety in theChemical Industry: Users Guide to Quantitative Risk Analysis,4 these results
40、are a necessary input tocomprehensive quantitative risk assessments of process units or facilities. However, managers shouldrealize that the qualitative results of an HRA are as valuable as any quantitative estimates of human errorprobabilities.Anticipating and controlling the potentially adverse im
41、pacts of human actions or human/systeminteractions are integral parts of process safety management. Therefore, many process safetymanagement activities are directed toward improving human performance. For example, maintainingcurrent plant procedures will help ensure that workers have correct instruc
42、tions for the tasks they mustperform. Increasing training will help ensure that workers can diagnose process upsets and respondcorrectly to emergency situations. Scrutinizing designs before they are installed will help eliminate designerrors and identify ways to reduce the likelihood of human errors
43、 that could adversely affect quality,productivity, or safety.Ultimately, the term “human error” should connote no more sense of blame or emotion than theterm “hardware failure.” Rather than seeking to blame or punish a worker when an incident occurs,managers should look for the root causes in the wo
44、rk situation. Only if managers recognize andaccept their responsibility to identify and eliminate error-likely situations in the workplace will there bea significant reduction in the frequency and severity of human errors. Directly involving the workersin these efforts is the best way to achieve you
45、r goals. Human factors engineering is an important toolthat managers can use in their quest for an ever safer and more productive organization.1Section 1INTRODUCTION1.1 IMPORTANCE OF IMPROVING HUMAN PERFORMANCEWhat caused the last process upset at your facility? The last quality problem? The lastuns
46、cheduled unit outage? The last accident? Chances are you blamed human error as either the directcause (e.g., an operator opening the wrong valve) or as a significantly contributing cause (e.g., an operatorfailing to start the spare pump quickly enough) of the process upset. And now that the guilty i
47、ndividual(s)has been counseled, disciplined, or fired, you feel sure that a similar mistake will never happen again.During the past five years, about 30 major accidents at chemical and hydrocarbon processingfacilities have severely injured hundreds of people, contaminated the environment, and caused
48、 more than$2 billion in property damage losses.1,2 The actual cost of these accidents was much higher because of theassociated business interruption costs, cleanup costs, legal costs, fines, losses of market share, and soforth. Human error was a significant factor in almost all of these accidents. T
49、he total cost (includingforced outages and off-specification products, as well as accidents) of human errors in the processindustries is incalculable.Historically, managers have found human errors to be significant factors in almost every qualityproblem, production outage, or accident at their facilities. One study5 of 190 accidents in chemicalfacilities found that the top four causes were insufficient knowledge (34 percent), design errors (32percent), procedure errors (24 percent), and operator errors (16 percent).* A study6 of accidents inpetrochemical and refining units ide
