Guidelines for Evaluating Process Plant Buildings for External Explosions, Fires, and Toxic Releases E-Book

• Herausgeber: John Wiley & Sons
• Kategorie: Fachliteratur
• Sprache: Englisch

Seitenzahl: 294

Veröffentlichungsjahr: 2012

Beschreibung

Siting of permanent and temporary buildings in process areas requires careful consideration of potential effects of explosions and fires arising from accidental release of flammable materials. This book, which updates the 1996 edition, provides a single-source reference that explains the American Petroleum Institute (API) permanent (752) and temporary (753) building recommended practices and details how to implement them. New coverage on toxicity and updated standards are also highlighted. Practical and easy-to-use, this reliable guide is a must-have for implementing safe building practices.

Leseprobe

Contents

Cover

Half Title page

Title page

Copyright page

List of Figures

List of Tables

Acknowledgments

Glossary

Chapter 1: Introduction

1.1 Objective

1.2 Building Siting Evaluation Process

1.3 Selection of Approach

1.4 Background

1.5 Phillips, Pasadena, Texas USA: Propylene HDPE Unit VCE and BLEVEs

1.6 Evolution of Design and Siting practices for buildings in Process Plants

1.7 Organization of the Book

Chapter 2: Management Overview

2.1 Process Overview

2.2 Management Responsibilities Under API RP-752 and API RP-753

Chapter 3: Determining the Scope of the Building Siting Evaluation

3.1 Introduction

3.2 Buildings Considered

3.3 Scenario Selection

Chapter 4: Building Siting Evaluation Criteria

4.1 Introduction

4.2 Occupant Vulnerability

4.3 Criteria for Existing Buildings Exposed to Explosion Hazards

4.4 Criteria for Fires

4.5 Criteria for Toxic Exposures

4.6 Criteria for Building Upgrades and New Buildings

4.7 Risk Criteria

Chapter 5: Explosion Hazards

5.1 Introduction

5.2 Select Explosion Approach

5.3 Modeling and Quantifying and Explosion Hazards

5.4 Building Response to Explosion Hazards

5.5 Occupant Vulnerability to Explosion Hazards

5.6 Actions Required at the Completion of the Evaluation

Chapter 6: Fire Hazards Assessment

6.1 Introduction

6.2 Determining if a Fire Hazard Exists

6.3 Spacing Table Approach

6.4 Performing a Consequence-Based or Risk-Based Building Siting Evaluation For Fire

6.5 Occupant Response to Fire Hazards

6.6 Defining the Fire Protection Concept

Chapter 7: Toxic Hazards Assessment

7.1 Introduction

7.2 Determining if a Toxic Hazard Exists

7.3 Building Siting Evaluation For Toxics

7.4 Defining the Toxic Protection Concept

7.5 Evacuation VS. Sheltering-In-Place

Chapter 8: Frequency and Probability Assessment

8.1 Introduction

8.2 Developing a Scenario List

8.3 Calculation of Frequency of Initiating Event or Accident

8.4 Probability and Frequency of Final Outcomes

8.5 Unit-Based Outcome Frequencies

Chapter 9: Risk Assessment

9.1 Introduction

9.2 Risk Measure Types

9.3 Calculating Risk

9.4 Interpretation and Use of Risk Measures

Chapter 10: Mitigation Plans and Ongoing Risk Management

10.1 Development of Mitigation Plans

10.2 Building Modifications

Chapter 11: Managing the Building Siting Process

11.1 Management of Change

11.2 Documentation Requirements

11.3 Documentation of Mitigation Systems Criteria and Performance

11.4 Maintaining Documentation “Evergreen”

References

Index

GUIDELINES FOR EVALUATING PROCESS PLANT BUILDINGS FOR EXTERNAL EXPLOSIONS, FIRES, AND TOXIC RELEASES

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

Copyright © 2012 by American Institute of Chemical Engineers, Inc.

Published by John Wiley & Sons, Inc., Hoboken, New Jersey. All rights reserved.Published simultaneously in Canada.

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Library of Congress Cataloging-in-Publication Data:

American Institute of Chemical Engineers. Center for Chemical Process Safety.Guidelines for evaluating process plant buildings for external explosions, fires, and toxic releases. — 2nd ed. p. cm. Rev. ed. of: Guidelines for evaluating process plant buildings for external explosions and fires. © 1996. Includes index. ISBN 978-0-470-64367-9 (hardback) 1. Chemical plants—Fires and fire prevention. 2. Explosions. 3. Chemical plants—Risk assessment. 4. Hazardous wastes. I. Guidelines for evaluating process plant buildings for external explosions and fires. II. Title. TH9445.C47A46 2012 660’.2804—dc232011049805

It is sincerely hoped that the information presented in this document will lead to an even more impressive safety record for the entire industry. However, the American Institute of Chemical Engineers, its consultants, the CCPS Technical Steering Committee and Subcommittee members, their employers, their employers’ officers and directors, and Baker Engineering and Risk Consultants, Inc. and its employees do not 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 Baker Engineering and Risk Consultants, Inc. and its employees and (2) the user of this document, the user accepts any legal liability or responsibility whatsoever for the consequences of its use or misuse.

LIST OF FIGURES

Figure 1.1. Relationship between API RP-752 and API RP-753

Figure 1.2. Overall Process for a Building Siting Evaluation

Figure 1.3. Flixborough Works Prior to the Explosion

Figure 1.4. Aerial View of Damage to the Flixborough Works

Figure 1.5. Damage to the Office Block and Process Areas at the Flixborough Works

Figure 1.6. Phillips Pasadena Plant Prior to the Incident

Figure 1.7. BLEVE at the Phillips Pasadena Site

Figure 1.8. Phillips Pasadena Process Area Damage (Courtesy of FM Global)

Figure 1.9. Aerial View of the ISOM Unit after the Explosion (CSB, 2007)

Figure 1.10. Destroyed Trailers West of the Blowdown Drum (arrow in upper left of the figure)

Figure 1.11. Vessel Involved in the Hickson & Welch Incident

Figure 1.12. Damage to the Control Building from the Jet Flame at Hickson & Welch

Figure 1.13. Damage to the Control Room and Impact on the Office Block from the Jet Flame at Hickson & Welch

Figure 2.1. Potential Outcomes of a Hazardous Material Release (Pitblado, 1996)

Figure 4.1. Building Damage Curves for a High Bay Metal Structure (~40,000 sq ft) (DDESB, 2009)

Figure 4.2. Illustration of Discrete State BDL Curves

Figure 4.3. Masonry Building BDL1 (Photo Courtesy of Explosion Research Cooperative)

Figure 4.4. Pre-Engineered Metal Building BDL 1 (Photo Courtesy of Explosion Research Cooperative)

Figure 4.5. Masonry Building BDL 2A (Photo Courtesy of Explosion Research Cooperative)

Figure 4.6. Pre-Engineered Metal Building BDL 2A (Photo Courtesy of Explosion Research Cooperative)

Figure 4.7. Masonry Building BDL 2B (Photo Courtesy of Explosion Research Cooperative)

Figure 4.8. Pre-Engineered Metal Building BDL 2B (Photo Courtesy of Explosion Research Cooperative)

Figure 4.9. Masonry Building BDL 3 (Photo Courtesy of Explosion Research Cooperative)

Figure 4.10. Pre-Engineered Metal Building BDL 3 (Photo Courtesy of Explosion Research Cooperative)

Figure 4.11. Presentation of HSE Risk Tolerance Levels (HSE, 2001)

Figure 4.12. A Three-tier Framework for Risk Interpretation

Figure 4.13. Regulated Acceptability Criteria for Societal Risk (CCPS, 2009b)

Figure 5.1. Logic Diagram for Siting Buildings with Regards to Explosion Hazards

Figure 5.2. Equivalent Spring-Mass SDOF System

Figure 5.3. Alternative Resistance Functions

Figure 5.4. TDOF System with Panel Loading Beam

Figure 5.5. TDOF System with Two Beams Loading Girder

Figure 5.6. TDOF System with Beams Loading Girders at Midspan

Figure 5.7. TDOF System with Girts Causing Frame Sway

Figure 6.1. Logic Diagram for Evaluating Buildings for Fire Hazards

Figure 7.1. Logic Flowpath for Evaluating Toxic Risk to Occupied Buildings

Figure 7.2. Indoor and Outdoor Mean Concentration for a Very Leaky Building with 2.0 Air Changes per Hour During a 66 Minute Outdoor Release Event (Wilson, 1996)

Figure 7.3. Comparison of Linear Dosage for Three Sheltering Policies (Wilson and Zelt, 1990)

Figure 8.1. Fault Tree Example

Figure 8.2. Failure Modes, Effects and Criticality Assessment Example

Figure 8.3. LOPA Example

Figure 8.4. Modifying Piping Leak Failure Rates to Account for Aging (Thomas, 1981)

Figure 8.5. Typical Variation in Wall Thickness with Pipe Diameter (ASME, 2004)

Figure 8.6. Loss Cause in the Petrochemical Industry (percentage of losses) (Marsh, 1999)

Figure 8.7. Event Tree for Calculating Loss of Containment Outcome Frequencies

Figure 8.8. Basic Quantified Event Tree Example

Figure 9.1. Example of Aggregate (Societal) Risk (F-N) Curve (CCPS, 2000)

Figure 9.2. Calculated F-N Curve from Example

Figure 10.1. Steel Posts Added to Exterior of Masonry Wall

Figure 10.2. Additional Steel Framing Inside of Upgraded Door

Figure 10.3. Steel Framing around Door to Secure to Masonry Wall

Figure 10.4. New Girts and Framing Members in Pre-Engineered Metal Building

Figure 10.5. New Roof Purlins Installed Between Existing Purlins

LIST OF TABLES

Table 1.1. Selected Accidents Involving Buildings in Process Plants

Table 3.1. Examples of Credible and Non-Credible Situations for Building Siting Evaluations

Table 4.1. Abbreviated Injury Scale (AIS) Severity Levels

Table 4.2. Typical Industry Building Damage Level Descriptions (Baker, 2002)

Table 4.3. U.S. Army COE Building Damage Levels

Table 4.4. Comparison of Industry and COE BDLs

Table 4.5. Assumed Building Construction for Default Buildings (Oswald and Baker, 2000)

Table 4.6. Occupant Vulnerabilities (%) as a Function of Building Damage Level (Oswald and Baker, 2000)

Table 4.7. Fire Presence Criteria

Table 4.8. Thermal Dose Criteria

Table 4.9. Occupant Thermal Vulnerability Criteria

Table 4.10. Common Siting Criteria Used for Toxic Hazards

Table 4.11. Toxic Vulnerability Criteria

Table 4.12. Comparison of Sample Individual Risk Criteria

Table 5.1. Recent Publications in Blast Resistant Design

Table 5.2. ASCE and COE Component Damage Definitions

Table 5.3. Window and Door Damage Levels (USACOE, 2006)

Table 5.4. Examples of Applicable TDOF Systems

Table 5.5. Examples of Non-Applicable TDOF Systems

Table 6.1. Typical Spacing Requirements for On-Site Buildings for Fire Consequences in Horizontal Distance (ft) [CCPS 2003a]

Table 6.2. Sources of Information for Protecting Buildings from Fires

Table 6.3. Risk-Based vs. Consequence-Based Fire Study Inputs

Table 6.4. Example Building Occupant Vulnerability (OV) from Radiant Heat Levels on Building Exterior from Pool and Jet Fires

Table 6.5. Example Occupant Vulnerabilities Inside Buildings for Ignition Outside Buildings

Table 6.6. Recommended Design Total Radiation (from API RP 521)

Table 6.7. Allowable Thermal Radiation Flux, Excluding Solar (from EN 1473)

Table 7.1. Risk-Based vs. Consequence-Based Toxic Study Inputs

Table 8.1. Simple Illustration of Factors Used to Determine Explosion Frequencies

Table 8.2. Some Commonly-Used Equipment Failure Rate Databases

Table 9.1. Summary of Some Major Types of Risk Measures

Table 9.2. Calculation of Individual Risk

Table 9.3. Calculation of Aggregate Risk

Table 9.4. Summary of Individual Risk Inputs

Table 9.5. Inputs for Aggregate Risk Calculation

Table 9.6. FN Curve Input Data

Table 9.7. Risk Index (Aggregate Risk) Calculation

Table 10.1. Hierarchy of Mitigation Measures (RP-API, 2009)

Table 10.2. Passive Mitigation Measures

Table 10.3. Active Mitigation Measures

Table 10.4 Procedural Mitigation Measures

Table 10.5. Examples of Situations in Which Interim Risk Management Measures May be Necessary

Table 11.1. Examples of Unintentional Risk Increases

ACKNOWLEDGMENTS

The American Institute of Chemical engineers (AIChE) and the Center for Chemical Process Safety (CCPS) express their appreciation and gratitude to all members of the Guidelines for Evaluating Process Plant Buildings for External Explosions, Fires, and Toxic Releases, Second Edition project and their CCPS member companies for their generous support and technical contributions in the preparation of this book. The AIChE and the CCPS also express their gratitude to the team and project managers from Baker Engineering and Risk Consultants who, under the direction of Mr. Quentin Baker, devoted time and expertise to ensure that this project would meet the needs of industry.

GUIDELINES FOR EVALUATING PROCESS PLANT BUILDINGS FOR EXTERNAL EXPLOSIONS, FIRES, AND TOXIC RELEASES

Second Edition

SUBCOMMITTEE MEMBERS:

Wayne Garland, Chair

Eastman Chemical Company

Glen A. Peters

Air Products and Chemicals, Inc.

Ralph Hodges

Bayer Material Science (Retired)

Kieran J. Glynn

BP

Robin Pitblado

Det Norske Veritas (USA) Inc.

Phillip N. Partridge III

Thomas C. Scherpa

DuPont

Chris Buchwald

ExxonMobil Chemical Company

Chris Gyasi

Lanxess Corporation, Orange Texas

Larry O. Bowler

SABIC

John Alderman

AON Risk Solutions

CCPS Staff Consultant:

Adrian L. Sepeda

CCPS wishes to acknowledge the many contributions of the Baker Engineering and Risk Consultants team with special recognition for outstanding and innovative contributions to the primary authors Quentin Baker, Raymond Bennett, and Michael Moosemiller, and to the technical contributions of Jatin Shah and John Woodward. Thanks also go to Moira Woodhouse for technical editing and pulling all the pieces together in the manuscript, and Joanna Sobotker for administrative support throughout the project.

Before publication, all CCPS books are subjected to a thorough peer review process. CCPS gratefully acknowledges the time and expertise these peer reviewers put into their reviews and acknowledges the thoughtful comments and suggestions. Their work and perspectives enhanced the accuracy, clarity, and value of these Guidelines.

Peer Reviewers

:

Company

:

Dale E. Dressel

Solutia

William (Skip) Early

Early Consulting, LC

Ron Pertuit, CSP

Eastman Chemical Co., Texas Operations

Don Connolley

BP

# 1

Not disclosed

# 2

Not disclosed

GLOSSARY

Accident:

An unplanned event or sequence of events that results in an undesirable consequence.

Acute:

Single, short-term exposure (less than 24 hours).

Aggregate Risk:

Societal risk for on-site workers in occupied buildings (API 752).

Blast:

A transient change in the gas density, pressure, and velocity of the air surrounding an explosion point. The initial change can be either discontinuous or gradual. A discontinuous change is referred to as a shock wave, and a gradual change is known as a pressure wave.

Blast Load:

The load applied to a structure or object from a blast wave, which is described by the combination of overpressure and either impulse or duration.

BLEVE (Boiling Liquid, Expanding Vapor Explosion):

The explosively rapid vaporization and corresponding release of energy of a liquid, flammable or otherwise, upon its sudden release from containment under greater-than-atmospheric pressure at a temperature above its atmospheric boiling point. A BLEVE is often accompanied by a fireball if the suddenly depressurized liquid is flammable and its release results from vessel failure caused by an external fire. The energy released during flashing vaporization may contribute to a shock wave.

Building:

A rigid, enclosed structure.

Building Siting Evaluation:

The procedures used to evaluate the hazards and establish the design criteria for new buildings and the suitability of existing buildings at their specific locations.

Building Geographic Risk:

The risk to a person who occupies a specific building 24 hours/day, 365 days/year.

Combustible:

Capable of burning.

Confinement:

Solid surfaces that prevent movement of unburnt gases and a flame front in one or more dimensions.

Congestion:

Obstacles in the path of the flame that generate turbulence.

Consequence:

The undesirable result of an incident, usually measured in health and safety effects, environmental impacts, loss of property, and business interruption costs. For building siting, consequence refers to building damage and occupant vulnerability from the potential effects of an explosion, fire, or toxic material release. Consequence descriptions may be qualitative or quantitative.

Consequence Based Approach:

The methodology used for building siting evaluation that is based on consideration of the impact of explosion, fire and toxic material release which does not consider the frequency of events.

Deflagration:

A propagating chemical reaction of a substance in which the reaction front advances rapidly into the unreacted substance, but at less than sonic velocity in the unreacted material.

Detonation:

A propagating chemical reaction of a substance in which the reaction front advances into the unreacted substance at or greater than sonic velocity in the unreacted material.

Essential Personnel:

Personnel with specific work activities that require them to be located in buildings in or near a process area for logistical and response purposes.

Explosion:

A release of energy that causes a blast.

Flammable:

A gas that can burn with a flame if mixed with a gaseous oxidizer such as air or chlorine and then ignited. The term flammable gas includes vapors from flammable or combustible liquids above their flash points.

Flame Speed:

The speed of a flame burning through a flammable mixture of gas and air measured relative to a fixed observer, that is, the sum of the burning and translational velocities of the unburned gases.

Flammable Limits

The minimum and maximum concentrations of combustible material in a homogeneous mixture with a gaseous oxidizer that will propagate a flame.

Frequency:

Number of occurrences of an event per unit of time.

F-N Curve:

A plot of cumulative frequency versus consequences (expressed as number of fatalities).

Hazard:

An inherent physical or chemical characteristic (e.g. flammability, toxicity, corrosivity, stored chemical energy, or mechanical energy) that has the potential for causing harm to people, property, or the environment.

HVAC:

Heating, Ventilating and Air Conditioning.

Impulse:

A measure that can be used to define the ability of a blast wave to do damage. It is calculated by the integration of the pressure-time curve.

Incident:

An unplanned event with the potential for undesirable consequences.

Individual Risk:

The risk to a person in the vicinity of a hazard. This includes the nature of the injury to the individual, the likelihood of the injury occurring, and the time period over which the injury might occur.

LFL (Lower Flammability Limit):

The concentration of a combustible material in air below which ignition will not occur. It is often referred to as the Lower Explosive Limit (LEL). Mixtures below this limit are said to be “too lean.”

Lookup Table Approach:

See “Spacing Table Approach”

MCE (Maximum Credible Event):

A hypothetical explosion, fire or toxic event that has the potential maximum consequence to the occupants of the building 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.

MOC (Management of Change):

A system to identify, review and approve all modifications to equipment, procedures, raw materials and processing conditions other than replacement in kind,” prior to implementation. [Management of Change is an element of the U.S. Occupational Health and Safety Administration (OSHA)’s Process Safety Management (PSM) regulation.]

Occupant Vulnerability:

Proportion of building occupants that could potentially suffer an injury or fatality if a postulated event were to occur. The level of injury is defined according to the technical basis of the occupant vulnerability model being used.

On-site Personnel:

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

Overpressure:

Any pressure above atmospheric caused by a blast.

Permanent Building:

Rigid structures intended for permanent use in fixed locations.

Portable Building:

Rigid structure that can be easily moved to another location within the facility.

Probability:

The expression for the likelihood of occurrence of an event or an event sequence during an interval of time. By definition, probability must be expressed as a number ranging from 0 to 1.

Process Area:

An area containing equipment (e.g. pipes, pumps, valves, vessels, reactors, and supporting structures) intended to process or store materials with the potential for explosion, fire, or toxic material release.

Probit:

A random variable with a mean of 5 and a variance of 1, which is used in various effect models.

PSM (Process Safety Management):

A program or activity involving the application of management principles and analytical techniques to ensure the safety of chemical process facilities. Sometimes called process hazard management. Each principle is often termed an “element” or “component” of process safety. [This can also refer to the U.S. Occupational Health and Safety Administration (OSHA)’s Process Safety Management (PSM) regulation 29 CFR 1910.119.]

Qualitative:

Based primarily on description and comparison using historical experience and engineering judgment, with little quantification of the hazards, consequences, likelihood, or level of risk.

QRA (Quantitative Risk Assessment):

The systematic development of numerical estimates of the expected frequency and/or consequence of potential accidents associated with a facility or operation based on engineering evaluation and mathematical techniques.

Reflected Pressure:

Impulse or pressure experienced by an object facing a blast.

Risk Based Approach:

A quantitative risk assessment methodology used for building siting evaluation that takes into consideration numerical values for both the consequences and frequencies of explosion, fire, or toxic material release.

Risk Based Inspection:

A risk assessment and management process that is focused on loss of containment of pressurized equipment in processing facilities, due to material deterioration. These risks are managed primarily through equipment inspection.

Scenario:

An unplanned event or incident sequence that results in a loss event and its associated impacts, including the success or failure of safeguards involved in the incident sequence.

Semi-quantitative:

Risk analysis methodology that includes some degree of quantification of consequence, likelihood, and/or risk level.

Shelter-in-Place:

A process for taking immediate shelter in a location readily accessible to the affected individual by sealing a single area (an example being a room) from outside contaminants and shutting off all HVAC systems.

Side-on Pressure:

The impulse or pressure experienced by an object as a blast wave passes by it.

Spacing Table Approach:

The use of established tables to determine minimum separation distances between equipment and buildings intended for occupancy. Industry groups, insurance associations, regulators and owner/operator companies have developed experience-based spacing tables for minimum building spacing for fire.

Toxic Material:

An airborne agent that could result in acute adverse human health effects.

Vapor Cloud Explosion:

The explosion resulting from the ignition of a cloud of flammable vapor, gas, or mist in which flame speeds accelerate to sufficiently high velocities to produce significant overpressure.

CHAPTER 1

INTRODUCTION

Catastrophic accidents in the chemical process industries, while uncommon, may affect buildings in or near processing facilities. The likelihood of serious events involving hazardous materials can and has been effectively reduced through the application of process safety management. Specifically, the CCPS Guidelines for Technical Management of Chemical Process Safety (CCPS, 1989a) states:

As the chemical process industries have developed more sophisticated ways to improve process safety, we have seen the introduction of safety management systems to augment process safety engineering activities.

Management systems for chemical process safety are comprehensive sets of policies, procedures, and practices designed to ensure that barriers to major incidents are in place, in use, and effective. The management systems serve to integrate process safety concepts into ongoing activities of everyone involved in operations — from the chemical process operator to the chief executive officer.

These process safety management systems help ensure that facilities are designed, constructed, operated, and maintained with appropriate controls in place to prevent serious accidents. Despite these precautions, buildings close to process plants have presented serious risks to the people who work in them. This observation is prompted by the fact that some buildings that were not designed and constructed to be blast resistant have suffered heavy damage, and in some instances have collapsed when subjected to blast loads from accidental explosions. Serious injury or fatality to the occupants resulted from the building damage. Experience indicates that personnel located outdoors and away from such buildings, if subjected to the same blast, may have a lower likelihood of serious injury or fatality. Building occupants have also been exposed to toxic vapors that enter through forced or natural convection ventilation, and thermal hazards that result from fires near buildings.

Industry associations and insurers have proposed building design and siting guidelines as a means of improving personnel safety. The resulting standards, however, are not universally applicable to all industry sectors and do not ensure consistent levels of safety. Consequently, the chemical processing industries recognizes the need for guidance on a uniform approach to the design and siting of buildings intended for occupancy. The chemical process industries also recognizes that this guidance needs to be practical and consistently applicable across the spectrum of interested industries, and take into account the specific operations and conditions existing at any particular site.

The purpose of this book, Guidelines for Evaluating Process Plant Buildings for External Explosions, Fires and Toxic Releases, Second Edition is to provide guidance to building siting evaluations. The first edition of this book was written in conjunction with the first edition of American Petroleum Institute (API) Recommended Practice (RP) 752, “Management of Hazards Associated with Location of Process Plant Permanent Buildings,” issued in 1995. API developed a recommended practice specific to siting of portable buildings in 2007. The new recommended practice was designated API RP-753 and named “Management of Hazards Associated with Location of Process Plant Portable Buildings” (API, 2007). API completed a major revision of API RP-752 in December 2009 (API, 2009). Development of API RP-753 and revision of API RP-752 prompted updating of this book. This book has an expanded role in providing the guidance for all phases of the building siting evaluation process.

API RP-752 was first published in 1995 and provided a three-stage framework for conducting a building siting evaluation. API RP-752 also included examples of numerical occupancy level criteria that could be used to screen buildings from siting evaluation, and some simplified consequence and risk analysis data. The 2009 edition transformed API RP-752 into a management process for siting evaluations, and removed most technical content. Portable buildings were removed from the scope of API RP-752 when API RP-753 was issued, and the scope of API RP-752 was clarified to encompass new and existing rigid structures intended to be permanently placed in fixed locations. Tents, fabric enclosures, and other soft-sided structures are therefore outside the scope of API RP-752.

API RP 752 (API, 2009) and RP 753 (API, 2007) have a set of guiding principles for building siting evaluations. API RP 752 guiding principles are shown below. API RP 753 has a similar set, but modified to be more suitable to portable buildings. The API RP-752 guiding principles are:

Locate personnel away from process areas consistent with safe and effective operations;

Minimize the use of buildings intended for occupancy in close proximity to process areas;

Manage the occupancy of buildings in close proximity to process areas;

Design, construct, install, modify, and maintain buildings intended for occupancy to protect occupants against explosion, fire and toxic material releases;

Manage the use of buildings intended for occupancy as an integral part of the design, construction, maintenance, and operation of a facility.

Figure 1.1 depicts the relationship between API RP-752 and API RP-753. Blast resistant modular buildings (BRM) can potentially fall within the scope of either API RP-752 or API RP-753 depending on the intended use of the BRM. BRMs that are intended for permanent installation in a fixed location fall within the scope of API RP-752, whereas all temporary applications fall within the scope of API RP-753, This book addresses both permanent and temporary buildings and provides analysis methods that support both of the API recommended practices.

Figure 1.1. Relationship between API RP-752 and API RP-753

API RP-753 includes restrictions on personnel who can be located in portable buildings in certain circumstances. Only essential personnel are allowed in selected portable buildings close to and within process units (API RP-753 Zone 1) when the building has been subjected to a detailed analysis for the hazards at the building location. No such personnel restrictions are included in API RP-752 for permanent buildings; instead, all buildings intended for occupancy undergo a detailed analysis for explosion hazards.

It is not the role of this book to create any additional building siting requirements beyond those defined in API RP-752 and API RP-753. The reader should review both recommended practices before reading this book. Guidance on all aspects of the building siting evaluation process can be found in this book. This book serves as a roadmap to references including CCPS documents.

A wide variety of technical and process safety management issues are referenced throughout this book. Detailed coverage of these issues is outside the scope of this book, however, and readers are referred to other CCPS books for more information. These include, in particular:

Guidelines for Technical Management of Chemical Process Safety (CCPS, 1989a)

Guidelines for Hazard Evaluation Procedures, Third Edition, with worked examples (CCPS, 2008b)

Guidelines for Chemical Process Quantitative Risk Analysis (CCPS, 2000)

Guidelines for Vapor Cloud Explosion, Pressure Vessel Burst, BLEVE and Flash Fire Hazards (CCPS, 2010)

Guidelines for Use of Vapor Cloud Dispersion Models (CCPS, 1987)

Guidelines for Vapor Release Mitigation (CCPS, 1988)

Guidelines for Facility Siting and Layout (CCPS 2003a)

Guidelines for Developing Quantitative Safety Risk Criteria (CCPS 2009b)

Guidelines for Fire Protection in Chemical, Petrochemical, and Hydrocarbon Processing Facilities (CCPS, 2003b).

Guidelines for Risk Based Process Safety (CCPS, 2007)

Additionally, the following references also provide guidance:

U.S. Army, “Structures to Resist the Effects of Accidental Explosions” (U.S. Army, 1991)

American Society of Civil Engineers,

Design of Blast Resistant Buildings in Petrochemical Facilities

(ASCE, 2010)

American Society of Civil Engineers,

Structural Design for Physical Security

(ASCE, 1999)

“Single Degree of Freedom Structural Response Limits for Antiterrorism Design,” (U.S. Army COE, 2006)

1.1 OBJECTIVE

The objective of these guidelines is to provide a practical approach to implementing a building siting evaluation for process plant buildings in accordance with API RP-752 and RP-753. Note that API RP-752 and RP753 provide the process by which building siting evaluations are conducted for permanent and portable buildings, respectively. However, these recommended practices do not provide the technical methods needed to conduct a building siting evaluation.

API RP-752 now requires a building siting evaluation of all permanent buildings intended for occupancy that are located on sites covered by the OSHA PSM regulation (29 CFR 1910.119). The analysis methods described in this book are not limited to U.S. OSHA PSM covered facilities and can be used for any buildings an owner/operator wishes to evaluate; in fact, other countries may have regulatory requirements that differ from the U.S. This book is applicable to onshore facilities and does not address circumstances that exist in offshore installations. API RP-753 has similar requirements for detailed analysis of portable buildings unless a portable building is sited beyond a distance determined by a conservative simplified analysis method for vapor cloud explosions (VCE). Even the API RP-753 simplified method requires site-specific data in terms of process unit congested volume to calculate the siting distance.

The purpose of this book is to provide the methods to address the explosion, fire and toxic impacts to process plant buildings and occupants occurring as a result of hazards associated with operations external to the building.

Discussion of the following hazards is beyond the scope of this book:

natural hazards;

terrorist attack;

fire and toxic impacts to off-site personnel and on-site personnel in open areas or within non-building structures; and

secondary or “knock-on” effects that develop relatively slowly, allowing sufficient time for personnel to evacuate buildings.

1.2 BUILDING SITING EVALUATION PROCESS

This book is organized around the overall building siting evaluation process in API RP-752 as depicted in Figure 1.2. Readers are encouraged to read this entire guideline before starting or revising a building siting evaluation. Chapter numbers that provide guidance for each step are shown in parentheses.

Figure 1.2. Overall Process for a Building Siting Evaluation

1.3 SELECTION OF APPROACH

The building siting process begins with selection of the approach that will be followed. The approach may be consequence-based or risk-based as explained in Chapter 2, Section 2.1.3. A consequence-based methodology does not include consideration of the frequency with which an explosion, fire or toxic scenario may occur; rather, the analysis is limited to computation of the damage or injury that may result from the postulated scenario. Risk-based analysis considers a range of scenarios and incorporates the frequency associated with each scenario. The risk to occupants of buildings is the sum of the risk posed by all of the scenarios impacting the building.

1.4 BACKGROUND

Prior accidents have prompted improvements to the approach to address risks to process plant buildings and their occupants. Table 1.1 provides a selected list of serious incidents involving buildings in process plants. A significant percentage of the fatalities occurred in buildings for the incidents shown in Table 1.1.

Table 1.1. Selected Accidents Involving Buildings in Process Plants

However, as indicated by the accidents in Denver, Colorado, and Linden, New Jersey, proper design and siting of occupied buildings can substantially reduce the risks of fatality.

For accidents affecting process plant buildings, the potential for serious or fatal injury to building occupants is the foremost concern. Additionally, in cases where buildings house critical controls or equipment, proper design and siting may also help reduce indirect safety impacts (e.g., due to loss of process control or emergency response capability), as well as business interruption costs and property loss from such events.

The following case histories further illustrate the risks to building occupants in structures not designed to be blast resistant and the ramifications of these incidents on changes to regulations and industry standards.

1.4.1 Flixborough, UK: Vapor Cloud Explosion in Chemical Plant

On June 1, 1974, a cyclohexane vapor cloud was released after the rupture of a pipe bypassing a reactor. HSE described the vapor cloud explosion that occurred in the reactor section of the caprolactam plant of the Nypro Limited, Flixborough Works (HSE, 1975). The Flixborough Works is situated on the east bank of the River Trent (Figure 1.3). The nearest villages are Flixborough (800 meters or one-half mile away), Amcotts (800 meters or one-half mile away), and Scunthorpe (4.9 km or approximately three miles away).

Figure 1.3. Flixborough Works Prior to the Explosion

The cyclohexane oxidation plant contained a series of six reactors. The reactors were fed by a mixture of fresh cyclohexane and recycled material. The reactors were connected by a pipe system, and the liquid reactant mixture flowed from one reactor into the other by gravity. Reactors were designed to operate at a pressure of approximately 9 bar (130 psi) and a temperature of 155°C (311°F). In March 1974, one of the reactors began to leak cyclohexane, and it was, therefore, decided to remove the reactor and install a bypass. A 0.51 m (20 in) diameter bypass pipe was designed and installed by plant personnel to connect the two flanges of the reactors. Bellows originally present between the reactors were left in place. Because reactor flanges were at different heights, the pipe had a dog-leg shape.

On May 29, 1974, the bottom isolating valve on a sight glass on one of the vessels began to leak, and a decision was made to repair it. On June 1, 1974, startup of the process following repair began. As a result of poor design, the bellows in the bypass failed and a release of an estimated 33,000 kg (73,000 lb) of cyclohexane occurred, most of which formed a flammable cloud of vapor and mist (HSE, 1975).