Guidelines for Evaluating Plant Buildings for Fire Explosion and Toxic Releases

Global Congress on Process Safety - 2012

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Guidelines for Evaluating Plant Buildings for Fire, Explosion, and

Toxic Releases—2nd Edition

R. Wayne Garland,

Eastman Chemical Company; [email protected] (for correspondence)

Adrian L. Sepeda,

CCPS Staff Consultant; [email protected] (for correspondence)

Quentin A. Baker Baker Engineering and Risk Consultants, Inc.; [email protected] (for correspondence)

Raymond H. Bennett, Ph.D.

Baker Engineering and Risk Consultants, Inc.; [email protected] (for correspondence)

Michael D. Moosemiller

Baker Engineering and Risk Consultants, Inc.; [email protected] (for

correspondence)

Prepared for Presentation at

8th

Global Congress on Process Safety

Houston, TX

April 1-4, 2012

UNPUBLISHED

AIChE shall not be responsible for statements or opinions contained

in papers or printed in its publications


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Note: Do not add page numbers. Do not refer to page numbers when referencing different portions of the

paper

Guidelines for Evaluating Plant Buildings for Fire,

Explosion, and Toxic Releases—2nd Edition

R. Wayne Garland,

Eastman Chemical Company; [email protected] (for correspondence)

Adrian L. Sepeda,

CCPS Staff Consultant; [email protected] (for correspondence)

Quentin A. Baker Baker Engineering and Risk Consultants, Inc.; [email protected] (for correspondence)

Raymond H. Bennett, Ph.D.

Baker Engineering and Risk Consultants, Inc.; [email protected] (for correspondence)

Michael D. Moosemiller

Baker Engineering and Risk Consultants, Inc.; [email protected] (for

correspondence)

The Center for Chemical Process Safety (CCPS) of the American Institute of Chemical

Engineers has completed a project to update the book, “Guidelines for Evaluating Process Plant

Buildings for External Fires, Explosions, and Toxic Releases.” The first edition of the guidelines

book was published in 1996, based on the existing edition of API RP 752 at that time. This new

second edition of the Guidelines book brings it in line with state of the art by addressing the

newest version of API RP 752 [1], addressing portable buildings under API RP 753 [2], adding

sections on toxic releases, and including recent technology and management system

developments. Major changes to API RP 752 include the elimination of occupancy screening,

requirements for more extensive documentation, and the requirement to address a Maximum

Credible Event (MCE). The second edition of the book provides an up-to-date comprehensive

and valuable resource to process safety professionals needing an understanding of how to

evaluate and address building siting situations. A summary of the project objectives, status, and

changes to API RP 752 that are addressed in the second edition of the book are presented here.

INTRODUCTION AND BACKGROUND The Center for Chemical Process Safety (CCPS) of the American Institute of Chemical

Engineers has completed a project to update the first edition of the book ―Guidelines for

Evaluating Process Plant Buildings for External Fires, Explosions, and Toxic Releases.‖ The

second edition captures new requirements from the latest version of American Petroleum

Institute API RP 752 ―Management of Hazards Associated with Location of Process Plant

Buildings‖ (2009-Third Edition) and adds those of API RP 753 ―Management of Hazards

Associated with Location of Process Plant Portable Buildings‖ (First Edition, June 2007).


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Project oversight was provided by the CCPS Process Plant Building subcommittee. BakerRisk

was the contractor for development of the second edition.

The intended audience for the second edition of the book ranges from corporate level managers

to Process Safety Subject Matter Experts (SMEs) involved in building siting evaluations of

buildings intended for occupancy. We also expect the second edition of the book to be used as a

reference by regulators. The broad uses necessitated a technically neutral discussion to

alternative approaches.

The first edition of the guidelines book was published in 1996 and was based on the then current

First Edition of API RP 752, and thus it did not include a section on toxic releases. The second

edition brings it in line with state of the art by addressing the new requirements in the Third

Edition of API RP 752 and adding API RP 753 requirements, including allowing the use of

either consequence or risk-based approaches for all of the hazards addressed. It also expands

upon recent technology and management system developments.

The second edition of the book also directs EH&S site leaders involved in building siting

discussions to other CCPS books that will remain the primary technical references in such areas

as explosion modeling and risk assessment.

PROJECT OBJECTIVES AND GUIDING CONCEPTS The first edition of the book is slightly less than 200 pages. Because the new second edition of

the book has an increased scope, it is longer—approximately 300 pages. The new book

represents a significant expansion of the first edition due to the complete revamping of API RP

752, the addition of API RP 753, inclusion of toxic releases and risk, a better understanding of

expectations from regulatory agencies and end users, and other developments in the state of the

art. To the extent possible, the second edition of the book provides the owners and operators of

facilities the information required to develop a consistent philosophy for siting buildings.

To maximize the value of the second edition to the target audiences, it focuses on the integration

of various activities associated with building siting utilizing API RP 752 and API RP 753.

Various analysis techniques are discussed for consequence and risk analyses. Considering that

explosion, fire and toxic hazards are addressed as well as consequences for building damage and

occupant vulnerability and risk to occupants, the scope of technical content is very broad. This

broad scope created overlap with other CCPS Guideline books, some of which are regarded as

authoritative texts on specific subjects. The CCPS subcommittee decided to avoid overlap and

potential duplication with other books by identifying other authoritative texts and referring

readers to those references. Thus, the second edition of the book does not duplicate analysis

methods that are covered in Guidelines for Vapor Cloud Explosion, Pressure Vessel Burst,

BLEVE, and Flash Fire Hazards; Guidelines for Chemical Process Quantitative Risk Analysis;

or other authoritative references such as the Design of Blast Resistant Buildings in Petrochemical

Facilities [3]. Terminology used in the second edition follows CCPS standards and is to the

extent possible consistent with other CCPS books.

The second edition includes an introduction to blast resistant design. Since publication of the

first edition the structural engineering community has developed several key references that


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make the quantitative information in the first edition obsolete. The quantitative information from

the first edition was deleted. The new edition introduces concepts and direct readers to other

current sources for technical details.

The arrangement of the second edition of the book follows the sequential work process for

completing a building siting evaluation. This may be different than the flow of information in

the 2009 version of API RP 752. However, the pertinent sections of API RP 752 are cited so that

they can be cross-referenced as necessary.

SECOND EDITION CONTENT The second edition of the book includes a management overview that addresses the overall

building siting evaluation process with particular emphasis on the management activities that are

required. A major change in API RP 752 from the previous editions is that building siting is now

identified as a process and on-going activity rather than a one-time event. Thus, there are

multiple actions that must be performed by the owner or operator management team.

Management activities include the selection of approach, selection of acceptance criteria,

documentation of the building siting process, and risk mitigation plan and schedule (required by

API RP 752). Since managers are typically not practitioners of consequence and risk analysis,

this section does not include technical details.

The majority of the second edition of the book focuses on the technical aspects of the various

consequence and risk analyses as well as the administrative aspects of managing the building

siting process. New features are described in the following sections.

Determining the Scope of Buildings to Evaluate This discussion includes the requirements for selecting the relevant buildings to be included in

the assessment. A major change to API RP 752 is that the use of occupancy screening criteria in

the previous editions is specifically prohibited. Buildings must be addressed in the siting study if

they are ―intended for occupancy,‖ a term initially introduced in API RP 753. This change is

likely to result in many owners having to address buildings that had been screened out under the

previous versions of API RP 752.

“Maximum Credible Event (MCE)”

The revised API RP 752 requires sites to determine the MCEs that affect each occupied building

when performing consequence-based analyses. The second edition of the book provides

assistance to owners in selecting appropriate scenarios for MCEs for their individual buildings

based upon their operations. The determination of the MCEs is one of the most important steps

of the consequence-based approach under API RP 752. The MCE is defined as:

A hypothetical explosion, fire, or toxic material release 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 release impacts.


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The second edition of the book provides examples of what may (or may not) constitute an MCE,

a selection of which is reproduced below.

Selected Examples of Credible and Non-Credible Situations for Building Siting Evaluations*

―Credible‖ Rupture of small bore piping

Gasket failure

Loading/unloading hose rupture

Process upsets such as overfilling a vessel or tank

May or May

Not Be

―Credible‖

Rupture of large bore piping or vessel/tank

Reaction runaway that exceeds the pressure relief system

capacity

Vehicle impact to exposed process equipment and piping

Alternate case US EPA RMP scenario

―Non-Credible‖ Events that are not physically possible (e.g., inventory of

flammable material is insufficient to generate the scenario)

Multiple domino events when each event has a low likelihood

*reproduced here from Table 3.1, second edition of the book

Building Siting Evaluation Criteria The Third Edition of API RP 752 does not provide any quantitative criteria for use in a building

siting evaluation. Each owner/operator is allowed to set the criteria based on their own risk

circumstances but must be prepared to support the basis for their selection. The second edition

of the book introduces the different types of criteria that can be selected and the advantages and

disadvantages of each. The criteria may be consequence-based, risk-based, or spacing table-

based (for fires only). Different types of criteria may be set for different types of hazards. For

example, an owner/operator may choose to evaluate bursting pressure vessel explosion exposures

on a consequence basis (since the magnitude of the explosion is limited by the bursting pressure

and volume of the vessel). The same site may choose to evaluate vapor cloud explosions on a

risk basis, since in that case the strategy may be to provide various prevention measures that

reduce the frequency of the event. It is also permitted for sites to initially evaluate a hazard on a

consequence basis and later refine the analysis using a risk-based evaluation.

It is important for owner/operators to recognize that a principle of the hazard management

process is that the criteria for building siting are defined prior to an evaluation, in order to avoid

the perception that sites are revising criteria to fit their analysis results. Therefore, the criteria

used should be well thought-out and reviewed with management before final implementation of

a program, or completion of individual studies.

Consequence Assessment The sections for explosions and fires have been extensively revised to comply with the

requirements of API RP 752. Much of the anecdotal information in the first edition of the book

has been removed and replaced with discussions of concepts and principles as well as references

to other CCPS books and professional guidance documents. The chapter on toxic hazards is

entirely new.


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The new version of API RP 752 accepts by name certain types of methodologies that are

allowed, or not allowed, for the assessment of explosion and fire consequences. Examples

include but are not limited to the following:

Fires (Acceptable Methods) – Standard industry spacing tables, Dow Fire & Explosion

Index

Vapor Cloud Explosions (Acceptable Methods) – Blast Curve Techniques (such as the

Baker-Strehlow-Tang method, TNO multi-energy method, Congested Assessment

Method (CAM) and Advanced Blast Simulation Techniques (commonly referred to as

Computational Fluid Dynamics)

Vapor Cloud Explosions (Unacceptable) – TNT Equivalency Method

The second edition of the book provides a roadmap to references for additional information on

blast prediction methods and their application.

Frequency/Probability Assessment API RP 752 allows for the use of Quantitative Risk Assessment, but has specific requirements

regarding how frequencies may be established. This section provides a link between the second

edition book and other existing CCPS books on risk analysis. Areas of special interest include

guidance on the development of frequency information, potential sources of the information, and

guidelines for determining the applicability of the data to specific processes.

Risk Assessment It will often be the case that a risk analysis will consider events that are both greater and lesser

than an MCE for a given building. Thus, some events that may be considered ―non-credible‖ for

the purposes of an MCE may be evaluated in a risk assessment by quantifying their likelihood of

occurring.

API RP 752 does not provide risk acceptance criteria and neither does the CCPS book.

However, the RP does require the evaluation of aggregate risk to all personnel within a building,

whereas previously, some owner/operators only evaluated individual risk. The second edition of

the book serves as a roadmap to assist the user in implementing risk-based strategies, and

identify other resources available to assist in the development of risk acceptance criteria and

performing risk calculations.

The second edition of the book introduces new risk measures that are designed specifically for

the purposes of building siting risk assessment, and puts them in perspective with the ‗classic‘

ways of reporting risk. The second edition of the book also defines which types of risk are in the

scope of a building siting review, and which are not.

Risk Management The Third Edition of API RP 752 recommends specific actions for owner/operators to manage

risk upon completion of a building siting evaluation. Among these requirements are:


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The active management of building occupancy (e.g., to ensure buildings not intended for

occupancy do not become occupied).

Implementation of Management of Change (MOC) procedures to ensure that the assumptions

used in the development of the building siting evaluation remain appropriate and to identify

the changes in conditions that would trigger a reassessment of the evaluation. The second

edition of the book does not specifically define MOC procedures but identifies the types of

activities the procedures need to address.

Development of mitigation plans for buildings that do not meet the owner‘s siting criteria.

The mitigation plans may address relocation of personnel, minimizing the probability of

occurrence, or strengthening of the buildings. The plans must include a schedule for the

mitigation activities.

SUMMARY

The updated API RP 752 is more prescriptive in some ways, yet provides greater evaluation

options than before. As a result, it is expected that building siting evaluation methodologies will

become more standardized (and accurate) than was required previously. In addition, it is likely

that more owner/operators will migrate to risk-based approaches in order to be able to evaluate,

and take credit for the many mitigation measures that are typically in place in chemical

processing facilities.

The updated API RP 752 also requires operators to treat building siting as an ongoing process of

continuous improvement rather than simply a one-off technical evaluation. The second edition

book will help guide owner/operators through this process. This will help ensure the long-term

safety of the occupants of process plant buildings.

LITERATURE CITED

1. API (American Petroleum Institute), Management of Hazards Associated with Location of Process Plant

Permanent Buildings, API Recommended Practice 752, 3rd Edition, Washington, D.C., December 2009.

2. API (American Petroleum Institute), Management of Hazards Associated with Location of Process Plant Portable

Buildings,” API Recommended Practice 753, First Edition, Washington, D.C., June 2007.

3. ASCE, Design of Blast Resistant Buildings in Petrochemical Facilities, Second edition, Task Committee on Blast

Resistant Design, American Society of Civil Engineering, Reston, Virginia, 2010.

Guidelines for Evaluating Plant Buildings for Fire Explosion and Toxic Releases

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