GUIDELINES FOR SITING AND LAYOUT OF

FACILITIES

PUBLICATIONS AVAILABLE FROM THE CENTER FOR CHEMICAL PROCESS SAFETY

THE AMERICAN INSTITUTE OF CHEMICAL

ENGINEERS

GUIDELINES FORSITING AND LAYOUT OF

FACILITIES SECOND EDITION

CENTER FOR CHEMICAL PROCESS SAFETY OF THE

AMERICAN INSTITUTE OF CHEMICAL ENGINEERS

This edition first published 2018© 2018 the American Institute of Chemical Engineers

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, except as permitted by law. Advice on how to obtain permission to reuse material from this title is available at http://www.wiley.com/go/permissions.

The right of CCPS to be identified as the author of the editorial material in this work has been asserted in accordance with law.

John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030, USA

111 River Street, Hoboken, NJ 07030, USA

For details of our global editorial offices, customer services, and more information about Wiley products visit us at www.wiley.com.

Wiley also publishes its books in a variety of electronic formats and by print-on-demand. Some content that appears in standard print versions of this book may not be available in other formats.

While the publisher and authors have used their best efforts in preparing this work, they make no representations or warranties with respect to the accuracy or completeness of the contents of this work and specifically disclaim all warranties, including without limitation any implied warranties of merchantability or fitness for a particular purpose. No warranty may be created or extended by sales representatives, written sales materials or promotional statements for this work. The fact that an organization, website, or product is referred to in this work as a citation and/or potential source of further information does not mean that the publisher and authors endorse the information or services the organization, website, or product may provide or recommendations it may make. This work is sold with the understanding that the publisher is not engaged in rendering professional services. The advice and strategies contained herein may not be suitable for your situation. You should consult with a specialist where appropriate. Further, readers should be aware that websites listed in this work may have changed or disappeared between when this work was written and when it is read. Neither the publisher nor authors shall be liable for any loss of profit or any other commercial damages, including but not limited to special, incidental, consequential, or other damages.

Library of Congress Cataloging-in-Publication Data is available.

ISBN: 978-1-119-47463-0

Cover images: Silhouette, oil refinery ©manyx31/iStockphoto; Stainless steel ©Creativ Studio Heinemann/Getty Images, Inc.; Dow Chemical Operations, Stade, Germany/Courtesy of The Dow Chemical Company

Cover design by Wiley

Printed in the United States of America

10 9 8 7 6 5 4 3 2 1

Edition HistoryThe American Institute of Chemical Engineers (1e, 2003)

This book is one in a series of process safety guidelines and concept books published by the Center for Chemical Process Safety (CCPS). Please go to www.wiley.com/go/ccps for a full list of titles in this series.

It is sincerely hoped that the information presented in this document will lead to an even more impressive process safety record for industry; however, neither the American Institute of Chemical Engineers, its consultants, CCPS Technical Steering Committee and Subcommittee members, their employers, their employers officers and directors, nor BakerRisk® and its employees warrant or represent, expressly or by implication, the correctness or accuracy of the content of the information presented in this document. As between (1) American Institute of Chemical Engineers, its consultants, CCPS Technical Steering Committee and Subcommittee members, their employers, their employers officers and directors, and BakerRisk® and its employees, and (2) the user of this document, the user accepts any legal liability or responsibility whatsoever for the consequence of its use or misuse.

vii

CONTENTS

List of Figures.............................................................................. xiii List of Tables .............................................................................. xvii Acronyms and Abbreviations ...................................................... xix Glossary ....................................................................................... xxi Acknowledgments ................................................................... xxxiii Foreword .................................................................................. xxxv Preface .................................................................................... xxxvii

1 INTRODUCTION ......................................... 1 1.1 Objectives ............................................................. 1 1.2 A Siting and Layout Approach ............................... 3 1.3 How to Use This Guideline .................................... 4 1.4 The Protection Layers ........................................... 7 1.5 Terminology ........................................................ 12 1.6 Guideline References .......................................... 15 1.7 Separation Distances Based Primarily on Fire

Consequences ..................................................... 15

2 OVERVIEW OF BENEFITS ........................ 17 2.1 Implications of Siting and Layout ........................ 17 2.2 Management of Risks .......................................... 18 2.3 Implementing a Step-wise Approach for the

Siting and LayOut of Facilities ............................ 23 2.4 Anticipating the Changing World ........................ 25 2.5 Summarizing the Business Case for Proper

Siting of a Facility ............................................... 25

VIII GUIDELINES FOR SITING AND LAYOUT

3 IDENTIFYING THE PROCESS HAZARDS AND RISKS .............................. 27 3.1 Introduction ........................................................ 27 3.2 ........................... 28 3.3 Screening for Preliminary Hazards ..................... 29 3.4 Evaluating the Risks ........................................... 40 3.5 Checklist for Identifying the Process Hazards

and Risks ............................................................ 40 3.6 Summary ............................................................. 41

4 SELECTING A FACILITY LOCATION ......... 42 4.1 Introduction ........................................................ 42 4.2 Additional Information on the Facility ................. 43 4.3 Selecting a Team to Locate the Facility .............. 43 4.4 Guidelines when Surveying Potential Facility

Locations ............................................................ 46 4.5 Determining the Location Plot Size ..................... 47 4.6 Construction and Turnaround Issues .................. 51 4.7 Maps and Information ......................................... 52 4.8 Geological Issues ................................................ 54 4.9 Weather Issues ................................................... 59 4.10 Seismic Issues ..................................................... 62 4.11 Off-site Issues ..................................................... 62 4.12 Security Issues .................................................... 65 4.13 Environmental Issues .......................................... 67 4.14 Infrastructure Issues ........................................... 74 4.15 Building and Structure Issues ............................. 74 4.16 Material Handling Issues .................................... 74 4.17 Communications Issues ....................................... 83 4.18 Engineering Design Issues .................................. 85 4.19 Utilities Issues .................................................... 88 4.20 Other Characteristics .......................................... 94 4.21 Preparing the Information when Comparing

Locations ............................................................ 96 4.22 A Siting and Layout Illustration .......................... 97 4.23 Checklist for Selecting a Facility Location ........ 105 4.24 Summary ........................................................... 106

CONTENTS IX

5 SELECTING THE PROCESS UNIT LAYOUT WITHIN A FACILITY ................. 107 5.1 Introduction ...................................................... 108 5.2 Block Layout Methodology Overview ................ 110 5.3 How the Block Layout Integrates with the

Facility Location ............................................... 118 5.4 Applying Preventive Measures when Arranging

Process Units .................................................... 118 5.5 Applying Mitigative Measures when Arranging

Process Units .................................................... 120 5.6 Construction and Turnarounds ......................... 123 5.7 The Block Layout Approach: Step 1 -

......... 128 5.8 Off-site Issues ................................................... 131 5.9 Security Issues .................................................. 134 5.10 Environmental Issues ........................................ 134 5.11 Infrastructure Issues ......................................... 134 5.12 The Block Layout Approach: Step 2 -

Evaluating the Separation Distances between Blocks ............................................................... 135

5.13 Critical and Occupied Structures ...................... 139 5.14 Material Handling ............................................. 155 5.15 Process Units .................................................... 162 5.16 Tank Farms ....................................................... 165 5.17 Other Areas ....................................................... 169 5.18 Utilities ............................................................. 174 5.19 Optimizing the Locations of the Process Units .. 182 5.20 Resolving Block Layout Optimization Issues ..... 184 5.21 Continuing the Siting and Layout Illustration ... 185 5.22 Checklist For Selecting the Layout of Process

Units within a Facility ....................................... 190 5.23 Summary ........................................................... 191

6 SELECTING THE EQUIPMENT LAYOUT WITHIN A PROCESS UNIT ....... 193 6.1 Introduction ...................................................... 193 6.2 Equipment Layout Methodology Overview ........ 194 6.3 How the Equipment Layout Integrates with the

Block Layout ..................................................... 198

X GUIDELINES FOR SITING AND LAYOUT

6.4 Applying Preventive Measures when Arranging Equipment ........................................................ 199

6.5 Applying Mitigative Measures when Arranging Equipment ........................................................ 209

6.6 Critical and Occupied Structure Design ............ 219 6.7 Equipment ........................................................ 228 6.8 Resolving Equipment Layout Optimization

Issues ................................................................ 233 6.9 Continuing the Siting and Layout Illustration ... 234 6.10 Checklist For Selecting the Equipment Layout

within a Process Unit ........................................ 239 6.11 Summary ........................................................... 240

7 MANAGING CHANGES ............................ 241 7.1 Introduction ...................................................... 241 7.2 Addressing Surrounding Community and

Industrial Expansions ........................................ 244 7.3 A Siting and Layout Approach when Managing

Changes ............................................................ 245 7.4 Maintaining Facility Integrity during its Life

Cycle ................................................................. 246 7.5 Managing Expansions at an Existing Facility .... 250 7.6 Managing Purchases of Existing Facilities ........ 251 7.7 Monitoring changes with Periodic Reviews....... 252 7.8 Addressing Siting and Layout Issues which are

Identified During Expansions ............................ 262 7.9 Summary ........................................................... 262

CONTENTS XI

8 CASE HISTORIES .................................... 265

9 REFERENCES .......................................... 301

10 APPENDICES .......................................... 315

APPENDIX A. ADDITIONAL SITING AND LAYOUT REFERENCES ........................... 319

APPENDIX B. CCPS RECOMMENDED DISTANCE TABLES FOR SITING AND LAYOUT OF FACILITIES ......................... 335

APPENDIX C. CHECKLIST FOR IDENTIFYING THE PROCESS HAZARDS AND RISKS ............................ 338

APPENDIX D. CHECKLIST FOR SELECTING A FACILITY LOCATION ........................... 342

APPENDIX E. CHECKLIST FOR SELECTING THE PROCESS UNIT LAYOUT WITHIN A FACILITY ................. 347

APPENDIX F. CHECKLIST FOR SELECTING THE EQUIPMENT LAYOUT WITHIN A PROCESS UNIT ....... 349

INDEX...............................................................351

xiii

List of Figures

Figure 1.1. A Siting and Layout Approach ................................................ 4 s .............................................. 10

Figure 1.3. Guideline Terminology ........................................................ 14 Figure 2.1. The Effect of Time on the Options for Reducing Process

Safety Risks ............................................................................ 19 Figure 2.2. Life cycle Phases for a Facility, a Process Unit, or the

Equipment .............................................................................. 20 Figure 2.3. The Chapters Corresponding to the Steps for Siting and

Laying out of Facilities ........................................................... 24 Figure 3.1. An illustration of potential flammability limit contours for

flash fires ............................................................................... 32 Figure 3.2. An illustration of potential thermal radiation contours from

pool or jet fires ....................................................................... 34 Figure 3.3. An illustration of potential blast overpressure contours ..... 36 Figure 3.4. An illustration of potential toxic release endpoint contours

from a small leak using the ERPG guidance .......................... 37 Figure 3.5. An illustration of potential toxic release endpoint contours

from a small leak using probits .............................................. 38 Figure 4.1. Typical Land Use Guidance for the Land Surrounding a

Facility ................................................................................... 53 Figure 4.2. Characteristics Considered when Selecting a Facility

Location ................................................................................. 56 Figure 4.3. A Southeast "Prevailing Wind" Direction shown on a Wind

Rose Diagram ......................................................................... 60 Figure 4.4. Location 1 - Proposed Inland Site in Remote Area ........... 100 Figure 4.5. Location 2 - Proposed Inland Site with Nearby Development

............................................................................................. 101 Figure 5.1. Flowchart used to Determine the Process Unit Layout

Distances at a Facility .......................................................... 112 Figure 5.2. An Example of a Modeled Dispersion Profile .................... 117

XIV GUIDELINES FOR SITING AND LAYOUT

Figure 5.3. How Layout Distances are Measured at a Facility ........... 117 Figure 5.4. Blast Overpressure Contours for the Proposed Site ......... 124 Figure 5.5. Block Layout Diagram for the New Low Hazard Operation

............................................................................................. 137 Figure 5.6. Block Layout Diagram with Layout Distances for the New

Low Hazard Operation ......................................................... 139 Figure 5.7. Building Damage Levels as a Function of Pressure-Impulse

Curves .................................................................................. 144 Figure 5.8. Rail Car Fragment thrown from the Crescent City BLEVE

............................................................................................. 169 Figure 5.9. Location 3 Facility Layout for its Structures and Process

Unit Blocks ........................................................................... 189 Figure 6.1. Flowchart used to Determine Equipment Layout Distances

within a Process Unit ........................................................... 197 Figure 6.2. Computer Aided Design (CAD) Image Depicting a Proposed

Layout of Equipment within a Process Unit ......................... 202 Figure 6.3. Traditional Pump Row / Pipeway Arrangement when

Transferring Materials in Overhead Piping ......................... 203 Figure 6.4. A Safer Process Unit Pump Row / Pipeway Arrangement

when Transferring Flammable Materials in Overhead Piping ............................................................................................. 204

Figure 6.5. An Example Hazardous Area / Zone Classification Drawing using a 3D Facility Plot Plan ................................................ 207

Figure 6.6. The DuPont Brandywine Powder Mills .............................. 227 Figure 6.7. Layout of the Ethylene Unit's Process Unit Blocks for

Location 3 ............................................................................ 235 Figure 6.8. Layout of the Equipment in the Cracking Furnace Unit for

Location 3 ............................................................................ 238 Figure 7.1. A Siting and Layout Approach when Managing Changes . 242 Figure 7.2. Managing Siting and Layout Changes within the Equipment,

Process Unit, and Facility Life Cycles .................................. 248 Figure 7.3. The Separation Distances at the Existing Process Unit .... 255 Figure 7.4. The Proposed Layout for the Expansion Project at an

Existing Facility ................................................................... 256 Figure 8.1. Layout of the area surrounding the ISOM unit at Texas City

............................................................................................. 268 Figure 8.2. Image of PEPCON after Initial Explosion .......................... 271 Figure 8.3. Aerial View of the Explosion Damage in Danvers ............ 274 Figure 8.4. Area Plot Plan and Impacted Areas Surrounding the PEMEX

LPG Facility .......................................................................... 276

LIST OF FIGURES XV

Figure 8.5. Growth of the Community Surrounding the PEMEX LPG Facility ................................................................................. 278

Figure 8.6. Images after the Explosion at the Little General Store .... 280

Extractor Piping ................................................................... 283 Figure 8.8. The Pipe Bridge after the Incident at Valero ..................... 284 Figure 8.9. Range of Off-site Damage at Praxair in St. Louis ............. 286 Figure 8.10. Range of the Vapor Cloud at Amuay ............................... 289 Figure 8.11. Range of the Blast Radius at West Fertilizer Company ... 292 Figure 8.12. Image of Damage from the West Fertilizer Company

Explosion .............................................................................. 292 Figure 8.13. Damage to the Concept Sciences Inc. Facility ................ 296 Figure 8.14. T2 Laboratories, Inc., after the Explosion ....................... 298 Figure 8.15. Fragment of the T2 Laboratories 3-inch (7.6 cm) Thick

Reactor ................................................................................. 298 Figure 8.16. The Imperial Sugar Facility after the Explosions and Fires

............................................................................................. 300

xvii

List of Tables

Table 1.1. Objectives for the Guideline Chapters .................................... 5 ...... 6

Table 3.1. Elements Enabling Hazardous Consequence Events ............ 31 Table 4.1. Comparison between Potential Locations ........................... 104 Table 5.1. Factors Influencing the Process Unit Layout ...................... 109 Table 5.2. Examples of Preventive Efforts using ISD Principles .......... 119 Table 5.3. Examples of Mitigative Efforts using ISD Principles .......... 121 Table 5.4. A Summary of the Layout Distances for the New Low Hazard

Operation ............................................................................. 138 Table 5.5. Building Damage Level (BDL) Descriptions ........................ 145 Table 5.6. Structure Location Factors and Design Considerations

Addressing Vapor Cloud Explosion (VCE) Risks .................. 146 Table 5.7. Structure Location Factors and Design Considerations

Addressing Fire Risks .......................................................... 147 Table 5.8. Structure Location Factors and Design Considerations

Addressing Toxic Release Risks ........................................... 149 Table 5.9. Potential Equipment Affected During a Loss of Utilities ..... 175 Table 5.10. A Summary of the Layout Distances between Facility

Structures in the Process Unit Block Layout for Location 3 190 Table 6.1. A Summary of the Equipment Layout Distances for the

Cracking Furnace in Location 3 ........................................... 239 Table 7.1. Siting and Layout Issues Addressed in the Expansion Project

Example ............................................................................... 257 Table 7.2. Comparison between t Existing Layout and Proposed Layout

Distances for Expansion Project Example ........................... 261 Table 8.1. An Overview of the Siting and Layout Case Histories ........ 266 Table 10.1. Framework for the questions in checklists in Appendices C -

D ........................................................................................... 317

xix

Acronyms and Abbreviations

AIChE American Institute of Chemical Engineers AIHA American Institute of Industrial Hygienists ALARA As Low As Reasonably Available ALARP As Low As Reasonably Practicable AOTC Associated Overseas Countries and Territories API American Petroleum Institute ARS Alternative Release Scenario ASME American Society of Mechanical Engineers ATEX European Directives 1999/92/EC and 2014/34/EU BPCS Basic Process Control System BPV Bursting Pressure Vessel BSI British Standards Institution BST Baker-Strehlow-Tang blast model CCPS Center for Chemical Process Safety CFD Computational Fluid Dynamics CFR United States Code of Federal Regulations COMAH United Kingdom HSE Control of Major Accident

Hazards CSB United States Chemical Safety Board DHA Dust Hazards Analysis DHS United States Department of Homeland Security DIN Deutsches Institut für Normung DOT United States Department of Transportation EN European Union Standards EPA United States Environmental Protection Agency ERPG Emergency Response Planning Guidelines (AIHA) EU European Union GB China standards annotation HAC Hazardous Area Classification (electrical) IChemE Institution of Chemical Engineers ISD Inherently Safer Design ISO International Organization for Standardization ITPM Inspection, Testing, and Preventative Maintenance

program

XX GUIDELINES FOR SITING AND LAYOUT

LEL Lower Explosivity Limit LFG Liquefied Flammable Gas LFL Lower Flammability Limit LNG Liquefied Natural Gas LPG Liquefied Petroleum Gas MEC Minimum Explosible Concentration (i.e., combustible

dusts) MCE Maximum Credible Event NFPA National Fire Protection Agency OSHA United States Occupational Safety and Health

Administration PED Pressure Equipment Directive POTW Publically Owned Treatment Works PSM Process Safety Management PSS Process Safety System RBI Risk Based Inspection program RBPS Risk Based Process Safety RCM Reliability Centered Maintenance RCRA Resource Conservation and Recovery Act (United

States EPA) RMP Risk Management Program (United States EPA) RP Recommended Practice (i.e., API guidance) UK United Kingdom UK HSE United Kingdom Health and Safety Executive US United States VCE Vapor Cloud Explosion WCS Worst Case Scenario

xxi

Glossary

This Glossary contains the terms specific to this Guideline and process safety related terms from the CCPS Process Safety Glossary. The specific CCPS process safety related terms in this Guideline are current at the time of publication; please access the CCPS website for potential updates to the CCPS Glossary.

Term Definition Access Ways Travel ways that provide occasional access

to equipment or congested areas of a facility for maintenance, security, and firefighting vehicles. Also known as tertiary roadways.

Alternative Release Scenario (ARS)

The basis for an off-site consequence analysis required by the United States EPA Risk Management Program (RMP) Rule. This release scenario has less adverse consequences, but is more likely than the Worst Case Scenario. See Maximum Credible Event (MCE) and Worst Case Scenario (WCS).

As Low As Reasonably Practicable (ALARP)

The concept that efforts to reduce risk should be continued until the incremental sacrifice (cost, time, effort, or other expenditure of resources) is grossly disproportionate to the incremental risk reduction achieved. The term as low as reasonably achievable (ALARA) is often used synonymously.

Barrier See Safeguard.

XXII GUIDELINES FOR SITING AND LAYOUT

Term Definition Boilover A violent expulsion of contents caused by a

heat wave from the surface burning at the top of the tank reaching the water layer at the bottom of the tank.

Brownfield An industrial or commercial property that is abandoned or underused and is being considered as a location for a new facility or for redevelopment.

Buffer Zone Additional undeveloped land surrounding the facility, often purchased to provide additional distance between the hazards and the surrounding community, which helps reduce the likelihood or severity of potential off-site impact, or helps reduce the likelihood of future community growth next to the facility.

Building A rigid, enclosed structure.

Chambering Enclosing a hazardous process unit within a building such that toxic materials are confined during a loss of containment (risk is unacceptable if the toxic material escapes).

Combustible Material

Materials that cause fires.

Combustible dust

A finely divided combustible particulate solid that presents a flash fire hazard or explosion hazard when suspended in air or the process-specific oxidizing medium over a range of concentrations [NFPA 652, NFPA 654].

Complex A collection of facilities that may or may not be owned by the same company, but are located within the contiguous boundaries of a specific geographic location, such as an industrial or chemical park. A facility within a complex may feed or take raw materials from another facility in the complex or may be totally independent of its industrial neighbors.

GLOSSARY XXIII

Term Definition Confinement Obstacles such as walls and ceilings of a

building, vessel, pipe, etc. that serve to limit the expansion of a dispersing burning vapor cloud.

Congestion Obstacles in the path of the flame that generate turbulence and compression.

Containment A system characteristic which prevents reactants or products from being exchanged between the chemical system and its environment.

Critical Equipment

Equipment, instrumentation, controls, or systems whose malfunction or failure would likely result in a catastrophic release of highly hazardous chemicals, or whose proper operation is required to mitigate the consequences of such release.

Critical Infrastructure

Systems and assets, whether physical or virtual, so vital that the loss, interruption, incapacity, or destruction of which (1) would have a negative or debilitating effect on the security, economic security, public health, or safety of a nation, region, or any local government, or (2) cause national or regional catastrophic effects.

Domino Effect The triggering of secondary events, such as toxic releases, by a primary event, such as an explosion, such that the result is an increase in consequences or area of an effect zone. Generally only considered when a significant escalation of the original incident results.

Emergency Planning Response Guidelines (ERPG)

A system of guidelines for airborne concentrations of toxic materials prepared by the AIHA. For example, ERPG-2 is the maximum airborne concentration below which it is believed nearly all individuals could be exposed for up to one hour without experiencing or developing irreversible or other serious health effects or symptoms that could impair an individual's ability to take protective action.

XXIV GUIDELINES FOR SITING AND LAYOUT

Term Definition Equipment A piece of hardware which can be defined in

terms of mechanical, electrical or instrumentation components contained within its boundaries.

Facility Sometimes also called a plant. The physical location where a management system activity is performed. In early life cycle stages, a facility may be the company's central research laboratory, pilot plant, or the engineering offices of a technology vendor. In later stages, the facility may be a typical chemical plant, storage terminal, distribution center, or corporate office. In the context of this document, a facility is a portion of or a complete plant, unit, site, complex or offshore platform or any combination thereof.

Fixed facility A portion of or a complete plant, unit, site, complex or any combination thereof that is generally not moveable. In contrast, mobile facilities, such as ships (e.g., transport vessels, floating platform storage and offloading vessels, drilling platforms), trucks, and trains, are designed to be movable.

Flammable Material

Materials that cause fires.

Grassroots Totally new facility that may be built upon a greenfield or brownfield location.

Greenfield Undeveloped property that has not been used before for either commercial or industrial purposes and is being considered as a location for a new facility.

GLOSSARY XXV

Term Definition Hazard An inherent chemical or physical

characteristic that has the potential for causing damage to people, property, or the environment. (Note: This guideline refers to

their toxicity, flammability, and reactivity, and physical hazards, such as extreme processing conditions such as high pressures and temperatures.)

Hazardous Area Classification (HAC)

Locations which are classified depending on the properties of the flammable gas, flammable liquid produced vapor, combustible liquid produced vapors, combustible dusts, or fibers/flyings that may be present, and the likelihood that a flammable or combustible concentration or quantity is present [adapted from Article 500 of NFPA 70, National Electrical Code]. See Zone.

Hazardous Process Area or Unit

An area containing equipment (e.g., pipes, pumps, valves, vessels, reactors, and supporting structures) intended to process or store materials. Hazardous process areas/units have the potential for explosion, fire, or toxic material releases.

Hazard Zone For an incident that produces an outcome such as toxic release, the hazard zone is the area over which the airborne concentration equals or exceeds some level of concern. For a flammable release, the area of effect is based on a specified level of thermal radiation. For a release that results in explosion, this is the area defined by specified overpressure levels.

Infrastructure The basic facilities, services, and installations needed for the functioning of a site such as transportation and communications systems, water and power lines, and public institutions including emergency response organizations.

XXVI GUIDELINES FOR SITING AND LAYOUT

Term Definition Inherently Safer A condition in which the hazards associated

with the materials and operations used in the process have been reduced or eliminated, and this reduction or elimination is permanent and inseparable from the process.

Knock-on Effect See Domino Effect.

Layer of Protection

A concept whereby a device, system, or human action is provided to reduce the likelihood and/or severity of a specific loss event.

Layout The relative location of equipment or buildings within a given site.

Life Cycle The stages that a physical process or a management system goes through as it proceeds from birth to death. These stages include conception, design, deployment, acquisition, operation, maintenance, decommissioning, and disposal. (Note: This guideline refers to these stages as eight distinct phases: design, fabricate, install, commission, operate, maintain, change, and decommission.)

Lower Explosivity Limit (LEL)

See Lower Flammability Limit (LFL). (Note: This guideline refers to LFL, only.)

Lower Flammability Limit (LFL)

That concentration of a combustible material in air below which ignition will not occur. It is often, interchangeably called Lower Explosive Limit (LEL) and for dusts, the Minimum Explosible Concentration (MEC).

GLOSSARY XXVII

Term Definition Maximum Credible Event (MCE)

A hypothetical explosion, fire, or toxic material release event that has the potential maximum consequence to the occupants under consideration from among the major scenarios evaluated. The major scenarios are realistic and have a reasonable probability of occurrence considering the chemicals, inventories, equipment and piping design, operating conditions, fuel reactivity, process unit geometry, industry incident history, and other factors. Each building may have its own set of MCEs for potential explosion, fire, or toxic material release impacts [API RP 752]. See Worst Case Scenario (WCS) or Alternative Release Scenario (ARS).

Mitigative Safeguard

A safeguard that is designed to reduce the severity of a loss event. Mitigative safeguards can be divided into detection safeguards and correction safeguards. See Safeguard.

Off-Site Outside of the facility's property line - represents the adjacent area external to the

-

if any, on industrial neighbors, the surrounding community or environment.

On-site Inside the facility's property line - the processes and support operations within the

ndary or property limits (this

is not owned by the company).

On-Site Personnel

Employees, contractors, visitors, service providers, and others present at the facility.

Permanent Building

Rigid structures intended for permanent use in fixed locations.

Piperack, Pipeway, Pipeband

A structure that supports pipes, power leads, and instrument cable trays.

Plant See Facility.

XXVIII GUIDELINES FOR SITING AND LAYOUT

Term Definition Pool Fire The combustion of material evaporating

from a layer of liquid at the base of the fire.

Portable Building

Rigid structure that can be easily moved to another location within the facility. Portable buildings include temporary buildings or trailers used to house people or store equipment.

Preventive Safeguard

A safeguard that prevents the occurrence of a particular loss event, given that an initiating cause has occurred; i.e., a safeguard that intervenes between an initiating cause and a loss event in an incident sequence. See Safeguard.

Probit A random variable with a mean of 5 and a variance of 1, which is used in various effect models. Probit-based models derived from experimental dose-response data, are often used to estimate the health effect that might result based upon the intensity and duration of an exposure to a harmful substance or condition (e.g., exposure to a toxic atmosphere, or a thermal radiation exposure).

Process Safety Hazard

See Hazard.

Process Section (or Train) within a process unit containing

combination of processing equipment that is focused on a single operation.

Property Line The perimeter of a facility surrounded by the community, other industrial facilities, or undeveloped land owned by someone external to the company. Sometimes called a property boundary.