Guidelines for Determining the Probability of Ignition of a Released Flammable Mass

Complemented by an estimating tool spreadsheet based on a fixed set of chemicals to assist in risk estimations, Probability of Ignition of a Released Flammable Mass converts a "best guess" to a calculated value based on available information and current technology. The text documents and explains the science and background of the technology-based approach. The tool, when populated with appropriate data, yields an estimate of the probability that a defined release of a flammable material will ignite if exposed to an ignition source. This information can be used to make risk assessments with a higher degree of confidence than estimates made before and it provides valuable information for use in the development of a facility's Emergency Response Plan.

Table of Contents:
FORWARD XI 1 INTRODUCTION 1 1.1 Objectives 1 1.2 Motivation for this Book 1 1.2.1 A Brief History of Fire Protection 2 1.2.2 The Development of Risk-Based Approaches to Flammables Management 3 1.2.3 Difficulties in Developing Ignition Probability Prediction Methods 4 1.2.4 Missing Variables 5 1.2.5 Summary of Industry Needs and Path Forward 5 1.2.6 Applications for This Book 6 1.2.7 Limitations in Applying the Approaches in This Book 7 1.3 Ignition Probability Overview 8 1.3.1 Theoretical Basis for Ignition 8 1.3.2 Key Ignition Factors Related to the Properties of the Fuel, and Available Surrogates that can be Used for Developing Probability of Ignition Predictions 13 1.3.3 Key Ignition Factors Related to the Release Source 19 1.3.4 Key Ignition Factors Related to the External Environment After the Release 27 1.4 Control of Ignition Sources 30 1.4.1 Ignition Source Management 30 1.4.2 Minimization of Release 33 1.5 Vapor Cloud Explosion Probability Overview 33 1.6 Detonation Overview 35 1.6.1 Detonation Using a Strong Ignition Source 35 1.6.2 Deflagration-to-Detonation Transition 35 1.6.3 Buncefield 35 1.7 Other Ignition Topics - Hydrogen 36 1.7.1 Ignition Mechanisms 36 1.7.2 Other Hydrogen Ignition Topics 37 2 ESTIMATION METHODS 39 2.1 Introduction 39 2.1.1 Event Tree 39 2.1.2 Failure Frequency Data for Use in Event Trees 41 2.1.3 Quantification of the Event Tree 41 2.2 Factors Influencing the Probability of Immediate Ignition 41 2.2.1 Temperature of Release Relative to the Autoignition Temperature 42 2.2.2 Minimum Ignition Energy (MIE) of Material Being Released 42 2.2.3 Pyrophoricity of Released Material 44 2.2.4 Pressure/Velocity of Discharge 44 2.2.5 Droplet Size 45 2.2.6 Presence of Particulates 46 2.2.7 Configuration/Orientation of Equipment Near/At the Point of Release 46 2.2.8 Temperature of Release (as it relates to its effect on MIE) 46 2.2.9 Phase of Release (API RBI) 47 2.2.10 Flash Point and Release Rate (TNO) 47 2.3 Factors Influencing the Probability of Delayed Ignition 47 2.3.1 Strength and Numbers of Ignition Sources 47 2.3.2 Duration of Exposure 51 2.3.3 Release Rate/Amount 51 2.3.4 Material Being Released 53 2.3.5 Release Phase/Flash Point/Boiling Point 53 2.3.6 Distance from Point of Release to Ignition Source 54 2.3.7 Meteorology 54 2.3.8 Events Originating Indoors 54 2.4 Factors Influencing the Probability of Explosion, Given Delayed Ignition 57 2.5 Potential Interdependence of Variables 57 2.6 Summary of Variables Used in Each Analysis Level 58 2.7 Basic (Level 1) Probability of Ignition Algorithms 59 2.7.1 Level 1 Algorithm for Probability of Immediate Ignition 59 2.7.2 Level 1 Algorithm for Probability of Delayed Ignition 60 2.8 Level 2 Probability of Ignition Algorithms 61 2.8.1 Level 2 Algorithm for Probability of Immediate Ignition 61 2.8.2 Level 2 Algorithm for Probability of Delayed Ignition 62 2.9 Advanced (Level 3) Probability of Ignition Algorithms 67 2.9.1 Level 3 Algorithm for Probability of Immediate Ignition 67 2.9.2 Level 3 Algorithm for Probability of Delayed Ignition 67 2.10 Developing Inputs When Chemical Properties Are Not Available 69 2.10.1 Estimating Input Properties of Chemicals Not in the Pick List 69 2.10.2 Estimating the Properties of Flammable Mixtures 71 2.11 Worked Example 73 2.11.1 Problem Statement 73 2.11.2 Level 1 Analysis 74 2.11.3 Level 2 Analysis 75 2.11.4 Level 3 Analysis 76 2.12 Application of the Models to a Study with Multiple Ignition Sources 77 3 TECHNICAL BACKGROUND AND DATA SOURCES 78 3.1 Introduction and Summary 78 3.2 Government-driven studies 82 3.2.1 Rew et al. 82 3.2.2 Bevi Risk Assessment Manual (TNO Purple Book) 91 3.2.3 HSE / Crossthwaite, et al. 95 3.2.4 HSE/Thyer 95 3.2.5 HSE/Gummer and Hawksworth - Hydrogen 97 3.2.6 Cawley/U.S. Bureau of Mines 98 3.2.7 Canvey 99 3.2.8 Witcofski (NASA) Liquid Hydrogen 100 3.3 Information Developed by Industry Groups 100 3.3.1 Cox/Lees/Ang 100 3.3.2 E&P Forum 103 3.3.3 API RBI 103 3.3.4 API RP 2216 108 3.3.5 IEEE 109 3.3.6 UK Energy Institute 110 3.4 Information Developed in Academia 113 3.4.1 Ronza, et al. 113 3.4.2 Offshore Explosions (Loughborough) 116 3.4.3 Srekl and Golob 116 3.4.4 Duarte et al. 117 3.4.5 Swain - Ignition of Hydrogen 118 3.4.6 Dryer et al. – Hydrogen and Light Hydrocarbons 118 3.4.7 Britton – Silanes and Chlorosilanes 119 3.4.8 Pesce et al. 120 3.5 Information Developed by Individual Companies 121 3.5.1 Spouge 121 3.5.2 Moosemiller 122 3.5.3 Johnson – Humans as Electrostatic Ignition Sources 123 3.5.4 Jallais – Hydrogen 125 3.5.5 Zalosh – Hydrogen 125 3.5.6 Smith - Pipelines 127 3.6 Studies Specific to Ignition of Sprays 128 3.6.1 Lee et al. 128 3.6.2 Babrauskas 130 3.7 Case Histories 131 3.7.1 Britton - External Ignition Events 131 3.7.2 Pratt - Gas Well and Pipeline Blowouts 132 3.7.3 Gummer and Hawksworth – Hydrogen Events 133 4 ADDITIONAL EXAMPLES 136 4.1 Introduction to Examples, and Potential “Lessons Learned” 136 4.1.1 “Reality” vs. Predictions 136 4.1.2 “Conservatism” – Does it Exist? 137 4.1.3 Cases where the Model may not be Appropriate or the Results Misinterpreted 138 4.1.4 Summary of Worked Examples 139 4.2 Worked Examples (based on other CCPS books) 140 4.2.1 “Vapor Cloud Explosion Hazard Assessment of a Storage Site” 140 4.2.2 “Open Field Release of Propane” 145 4.2.3 “Release from Pipeline” 149 4.3 Worked Examples (chemical and petrochemical plants) 152 4.3.1 “Ethylene Tubing Failure” 152 4.3.2 “Benzene Pipe Rupture” 154 4.3.3 “Spill from Methyl Ethyl Ketone Tank” 155 4.3.4 “Indoor Puncture of MEK Tote” 158 4.3.5 “Elevated Release” 161 4.4 Worked Examples (oil refineries) 164 4.4.1 “Gasoline Release from a Sight Glass” 164 4.4.2 “Overfilling a Gasoline Storage Tank” 168 4.4.3 “Overfilling a Propane Bullet” 170 4.4.4 “Hydrogen Release from a Sight Glass” 172 4.5 Worked Examples (Unusual Cases) 174 4.5.1 “Indoor Acid Spill - Ventilation Model” 174 4.5.2 “Release of Ammonia” 179 4.6 Worked Examples (‘Out of Scope’ Cases) 180 4.6.1 “Release of Gas from an Offshore Platform Separator” 180 4.6.2 “Dust Ignition” 183 4.7 Worked Examples of the Benefits of Plant Modifications and Design Changes 186 4.7.1 “Ignition by Hot Surfaces” 186 4.7.2 Release Prevention 189 4.7.3 Duration of Exposure 189 4.7.4 Benefit of Improved Ventilation of Indoor Releases – Continuation of “Indoor Acid Spill” Example 192 5 SOFTWARE ILLUSTRATION 194 5.1 Explanation and Instructions for Software Tool 194 5.2 Opening the Software Tool 194 5.3 General Inputs and Outputs 195 5.4 Level 1 Inputs 196 5.5 Level 2 Analyses 198 5.6 Level 3 Analyses 200 5.7 Explosion Probability 200 5.8 Illustrations of Software Use 201 5.8.1 “Vapor Cloud Explosion Hazard Assessment of a Storage Site” (example from Section 4.2.1) 201 5.8.2 “Open Field Release of Propane” (example from Section 4.2.2) 204 APPENDIX A. CHEMICAL PROPERTY DATA 207 APPENDIX B. OTHER MODELS FOR CONSIDERATION 213

About the Author :
Since 1985, the Center for Chemical Process Safety (CCPS) has been the world leader in developing and disseminating information on process safety management and technology. CCPS, an industry technology alliance of the American Institute of Chemical Engineers (AIChE), has published over 90 books in its process safety guidelines and process safety concepts series, and over 100 training modules through its Safety in Chemical Engineering Education (SACHE) series.