DESIGN SOLUTIONSFOR PROCESS EQUIPMENT FAILURES

Transcription

1 GUIDELINES FOR DESIGN SOLUTIONSFOR PROCESS EQUIPMENT FAILURES CENTER FOR CHEMICAL PROCESS SAFETY of the AMERICAN INSTITUTE OF CHEMICAL ENGINEERS 345 East 47th Street New York, New York 10017

2 Copyright 1998 American Institute of Chemical Engineers 345 East 47th Street New York, New York All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise without the prior permission of the copyright owner. Library of Congress Cataloging-in Publication Data Guidelines for design solutions for process equipment failures, p. cm. Includes bibliography and index. ISBN X 1. Chemical plants Safety measures. 2. Petroleum refineries safety measures. 3. Hazardous materials safety measures. I. American Institute of Chemical Engineers. Center for Chemical Process Safety. II. Title: Design solutions for process equipment failures. TP155.5.G /.280^-dc21 CIP This book is available at a special discount when ordered in bulk quantities. For information, contact the Center for Chemical Process Safety at the address shown above. It is sincerely hoped that the information presented in this volume will lead to an even more impressive safety record for the entire industry; however, the American Institute of Chemical Engineers, its consultants, CCPS Subcommittee members, their employers' officers and directors and Arthur D. Little Corporation disclaim making or giving any warranties or representations, express or implied, including with respect to fitness, intended purpose, use or merchantability and/or correctness or accuracy of the content of the information presented in this document. As between (1) American Institute of Chemical Engineers, its consultants, CCPS Subcommittee members, their employers, their employers' officers and directors, and Arthur D. Little Corporation and (2) the user of this document, the user accepts any legal liability or responsibility whatsoever for the consequences of its use or misuse.

3 FOREWORD Engineers like to think of their discipline as a rigorous application of scientific and mathematical principles to the problem of creating a useful object. To a certain extent, this is an appropriate description of the tools of engineering those techniques that we use to translate a concept in the mind of the designer into a physical object. But, where does that mental image of the object to be built come from? At its heart, engineering is intuitive, and an art form. The engineer/designer's accumulated experience, and that of others, is applied to a defined problem. By intuitive and creative problem solving processes the engineer develops and refines a conceptual design, and uses the mathematical and scientific tools of engineering to translate a mental concept into reality. The selection of the design basis for a process safety system is a problem like any other engineering problem. There is no equation or formula, no scientific principle, which will define the "best" design. Yes, there are scientific and mathematical tools which will help convert a design concept into something which can actually be constructed. But there is no general answer to the question cc What is the best design?" Each system must be considered on its own, with a thorough evaluation of all of the details of its environment and required functions, to determine what the optimal design will be. The number of potential solutions to any engineering problem is large. For each specific problem, there will be some solutions which meet the overall objectives better than others. How can we best find the optimal solution? I believe that the critical first step is to consider a large number of potential solutions, thereby increasing the likelihood that the best solution will be among those identified. Where do we get those potential solutions? One important source is accumulated experience our own, and that of others who have faced similar problems in the past. This book collects much of that accumulated experience from a large number of experts in the chemical process industry for equipment in common use. Use of the tables which make up the heart of this book will allow the reader to take advantage of many years of practical experience. By considering a large number of potential solutions to the prob-

4 lem of specifying the design basis for safety systems, the design engineer is more likely to be able to identify the solution which best meets his needs. This book emphasizes a risk-based approach to the evaluation of safety system design. Potential safety systems suggested are categorized as inherently safer/passive, active, and procedural, in decreasing order of robustness and reliability. Inherently safer approaches are often preferred, but there can be no general answer to the question of which approach or specific solution is best for a particular situation. Instead, the design engineer must take a very broad and holistic approach to the complete design, accounting for the many different, and often competing, objectives which the design must accomplish. Safety, health effects, environmental impact, loss prevention, economic and business factors, product quality, technical feasibility, and many other factors must be considered. This book challenges the engineer to adopt a risk-based approach to evaluating many competing goals when deciding among a number of potential design alternatives. This book can be extremely useful in conducting process hazard analysis studies. The failure mode tables in Chapters 3-12 can be the basis for hazard identification checklists, and also offer a variety of potential solutions for identified concerns. However, the book will be even more beneficial if used by the individual engineer at the earliest stages of the design process, before any formal hazard reviews. The message of this book can be summarized very briefly: Consider a large number of design options Identify opportunities for inherent and passive safety features early Use a risk-based approach to process safety systems specification I hope that this book will find a home on the desk (not gathering dust on the bookshelf!) of every chemical process designer, particularly those involved in the earliest phases of conceptual design where the basic chemistry and unit operations are defined. It should be consulted frequently in the course of the designer's day to day work in specifying and designing process facilities. If you are a process safety professional, make sure that all of the process design engineers in your organization read and use this book. It will make your job a lot easier! Dennis C. Hendershot

5 PREFACE The Center for Chemical Process Safety (CCPS) was established in 1985 by the American Institute of Chemical Engineers (AIChE) for the express purpose of assisting the Chemical and Hydrocarbon Process Industries in avoiding or mitigating catastrophic chemical accidents. To achieve this goal, CCPS has focused its work on four areas: establishing and publishing the latest scientific and engineering practices (not standards) for prevention and mitigation of incidents involving toxic and/or reactive materials, encouraging the use of such information by dissemination through publications, seminars, symposia and continuing education programs for engineers, advancing the state-of-the-art in engineering practices and technical management through research in prevention and mitigation of catastrophic events, and developing and encouraging the use of undergraduate education curricula which will improve the safety knowledge and consciousness of engineers. This book, Guidelines for Design Solutions for Process EquipmentFailures ^ is the result of a project begun in 1994 in which a group of volunteer professionals representing major chemical, pharmaceutical and hydrocarbon processing companies, worked with Arthur D. Little Inc., the contractor, to produce a book that attempts to describe the ways that major processing equipment can fail and be the cause of a catastrophic accident. The book then identifies the available design solutions that might avoid or mitigate the failure in a series of options ranging from inherently safer/passive solutions to active and procedural solutions. The book is concerned with engineering design that reduces risk due to process hazards only. It does not focus on operations, maintenance, transportation or personnel safety issues, although improved process safety can benefit each area. Detailed engineering designs are outside the scope of the

6 work, but the authors have provided an extensive guide to the literature to assist the designer who wishes to go beyond safety design philosophy to the specifics of a particular safety system design. By capturing industry experience in how major processing equipment can fail, the book provides a very useful tool for the selection of process safety systems which should be of service to process design engineers as well as members of process hazards analysis teams. The inherently safer solutions that are suggested may, in some cases, come as a surprise to the process and design engineer in that they may in fact be the most cost effective solution as well, if a true life cycle analysis is made of the cost of maintaining add-on safety systems or the resulting cost of operator failure to carry out procedural controls is considered. In other cases the procedural solution may be the best choice because it involves operators so that they may better understand and therefore better control the process as opposed to the replacement of operator intelligence with process interlocks. The book offers engineers inherently safer/passive, active and procedural design solutions but, ultimately engineers must make the case for the solutions that best satisfy their company's requirements for a balance between risk reduction and cost. This book has been organized into three major sections: First, a technique is provided for making risk-based design decisions. Second, a description of potential failure scenarios is presented for ten major processing equipment categories along with the potential design solutions that are available to the engineer. Third, the book contains two worked examples that illustrate how the risk-based decision technique can be applied to two process plant systems. The major equipment categories that are covered are; Vessels, Reactors, Mass Transfer Equipment, Heat Transfer Equipment, Dryers, Fluid Transfer Equipment, Solid-Fluid Separators, Solids Handling and Processing Equipment, Fired Equipment, and Piping and Piping Components. The potential equipment failure scenarios and design solutions for each equipment category are provided in tabular form in each equipment chapter. To facilitate use of this information, particularly in hazard identification studies such as HAZOPs, these tables have been provided in electronic format on a 3.5" diskette as Microsoft Word files. It is hoped that this will encourage the expansion of these tables based on the users experience.

7 ACKNOWLEDGMENTS The Center for Chemical Process Safety (CCPS) and those involved in its operation, wish to thank its many sponsors whose funding made this project possible, the members of its Technical Steering Committee who conceived of and supported this Guidelines project and the members of its Engineering Practices Subcommittee for their dedicated efforts, technical contributions, and enthusiasm. The subcommittee played a major role in the writing of the book by suggesting examples, by offering failure scenarios for the major equipment covered in the book and by suggesting possible design solutions. It is their collective industrial experience captured in this book that makes the book especially valuable to the process and design engineer. The members of the subcommittee wish to thank their employers for providing time and support to participate in this project. The members of the Engineering Practices Subcommittee were: Robert H. WaIz (Chairman), Laurence G. Britton, Stephen E. Cloutier, Glenn R. Davis, Kenneth W. Linder, Peter N. Lodal, Joseph B. Mettalia, Jr., John A. Noronha, Carl A. Schiappa, ABB Lummus Global Inc. Union Carbide Corp. UOP DuPont Industrial Risk Insurers Eastman Chemical Co. CCPS Staff Eastman Kodak Co. Dow Chemical USA Technical contributors and reviewers were: Steven R. Bruce, EQE International Myron Casada, JBF Associates Inc. William F. Early, Early Consulting, L. C. Rudolph C. Frey, The M. W. Kellogg Company

8 John A. Hoffmeister, Lockheed Martin Energy Systems T. Janicik, MallinckrodtInc. Robert W. Johnson, EaUeIIe Joseph Keel, The Eechtel Corporation D. Harper Meek, ^LRCO Chemical Company Mark A. Moderski, Stone & Webster Engineering Corporation Harvey Rosenhouse, FMC Corporation Stanley J. Schecter, Consultant Adrian L. Sepeda, Occidental Chemical Corporation Anthony A. Thompson, Monsanto Company Lester H. Wittenberg, CCPS The Engineering Practices Subcommittee is particularly indebted to its chairman, Bob WaIz, for his leadership, and to Peter Lodal of Eastman Chemical Company and Joe Keel of The Bechtel Corporation for their dedicated efforts in preparing the VCM/HC1 fractionation worked example in the book. Dennis C. Hendershot of the Rohm and Haas Company wrote the foreword to the book and is appreciated for his ongoing interest in this project and his able assistance and review of the work as it was being produced. Sanjeev Mohindra, P. J. Bellomo and R. Peter Stickles directed the project at Arthur D. Little, Inc. and were the authors of the risk-based design technique described in Chapter 2. Stanley S. Grossel, consultant and former chairman of the Engineering Practices Subcommittee, was the author of Chapter 4 (Reactors), Chapter 7 (Dryers), Chapter 9 (Solid-Fluid Separators), Chapter 10 (Solids Handling and Processing Equipment) and the Batch Reactor worked example.