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Risk-Based Inspection Technology

Downstream Segment

API RECOMMENDED PRACTICE 581 SECOND EDITION, SEPTEMBER 2008

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Copyright © 2008 American Petroleum Institute

Foreword

This publication provides quantitative procedures to establish an inspection program using risk-based methods for pressurized fixed equipment, including pressure vessel, piping, tankage, pressure relief devices, and heat exchanger tube bundles. This document is to be used in conjunction with API 580, which provides guidance on developing a risk-based inspection program for fixed equipment in the refining and petrochemical, and chemical process plants. The intent of these publications is for API 580 to introduce the principals and present minimum general guidelines for RBI while this publication provides quantitative calculation methods to determine an inspection plan using a risk-based methodology.

The API Risk-Based Inspection (API RBI) methodology may be used to manage the overall risk of a plant by focusing inspection efforts on the process equipment with the highest risk. API RBI provides the basis for making informed decisions on inspection frequency, the extent of inspection, and the most suitable type of NDE. In most processing plants, a large percent of the total unit risk will be concentrated in a relatively small percent of the equipment items. These potential high-risk components may require greater attention, perhaps through a revised inspection plan. The cost of the increased inspection effort may sometimes be offset by reducing excessive inspection efforts in the areas identified as having lower risk.

Shall: As used in a standard, “shall” denotes a minimum requirement in order to conform to the specification.

Should: As used in a standard, “should” denotes a recommendation or that which is advised but not required in order to conform to the specification.

May: As used in a standard, “may” indicates recommendations that are optional.

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Suggested revisions are invited and should be submitted to the Standards Department, API, 1220 L Street, NW, Washington, D.C. 20005, [email protected].

API RP 581 RISK-BASED INSPECTION TECHNOLOGY

PART 1

INSPECTION PLANNING USING API RBI TECHNOLOGY

1-1


PART CONTENTS 1 SCOPE ........................................................................................................................................... 5

1.1 Purpose ................................................................................................................................. 5 1.2 Introduction ........................................................................................................................... 5 1.3 Risk Management ................................................................................................................. 5 1.4 Organization and Use ........................................................................................................... 6 1.5 Tables..................................................................................................................................... 7

2 REFERENCES ............................................................................................................................... 8 3 DEFINITIONS ................................................................................................................................. 8

3.1 Definitions ............................................................................................................................. 8 3.2 Acronyms ............................................................................................................................ 10

4 API RBI CONCEPTS ................................................................................................................... 11 4.1 Probability of Failure .......................................................................................................... 11

4.1.1 Overview ...................................................................................................................... 11 4.1.2 Generic Failure Frequency ........................................................................................ 11 4.1.3 Management Systems Factor .................................................................................... 11 4.1.4 Damage Factors .......................................................................................................... 11

4.2 Consequence of Failure ..................................................................................................... 12 4.2.1 Overview ...................................................................................................................... 12 4.2.2 Level 1 Consequence Analysis ................................................................................. 12 4.2.3 Level 2 Consequence Analysis ................................................................................. 13

4.3 Risk Analysis ...................................................................................................................... 14 4.3.1 Determination of Risk ................................................................................................. 14 4.3.2 Risk Matrix ................................................................................................................... 15

4.4 Inspection Planning Based on Risk Analysis .................................................................. 15 4.4.1 Overview ...................................................................................................................... 15 4.4.2 Risk Target .................................................................................................................. 15 4.4.3 Inspection Effectiveness – The Value of Inspection ............................................... 16 4.4.4 Inspection Effectiveness – Example ......................................................................... 17 4.4.5 Inspection Planning .................................................................................................... 17

4.5 Nomenclature ...................................................................................................................... 18 4.6 Tables................................................................................................................................... 19 4.7 Figures ................................................................................................................................. 21

5 PRESSURE VESSELS AND PIPING .......................................................................................... 26 5.1 Probability of Failure .......................................................................................................... 26 5.2 Consequence of Failure ..................................................................................................... 26 5.3 Risk Analysis ...................................................................................................................... 26 5.4 Inspection Planning Based on Risk Analysis .................................................................. 26

6 ATMOSPHERIC STORAGE TANKS ........................................................................................... 27 6.1 Probability of Failure .......................................................................................................... 27 6.2 Consequence of Failure ..................................................................................................... 27 6.3 Risk Analysis ...................................................................................................................... 27 6.4 Inspection Planning Based on Risk Analysis .................................................................. 27

7 PRESSURE RELIEF DEVICES ................................................................................................... 28 7.1 General ................................................................................................................................ 28

7.1.1 Overview ...................................................................................................................... 28 7.1.2 PRD Interdependence with Fixed Equipment .......................................................... 28 7.1.3 Failure Modes .............................................................................................................. 28 7.1.4 Use of Weibull Curves ................................................................................................ 29 7.1.5 PRD Testing, Inspection and Repair ......................................................................... 30 7.1.6 PRD Overhaul or Replacement Start Date ............................................................... 30 7.1.7 Risk Ranking of PRDs ................................................................................................ 30 7.1.8 Link to Fixed or Protected Equipment ...................................................................... 30

7.2 Probability of Failure .......................................................................................................... 31 7.2.1 Definition ..................................................................................................................... 31 7.2.2 Calculation of Probability of Failure to Open .......................................................... 31 7.2.3 PRD Demand Rate ...................................................................................................... 31

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7.2.4 PRD Probability of Failure on Demand ..................................................................... 32 7.2.5 Protected Equipment Failure Frequency as a Function of Overpressure ............ 39 7.2.6 Calculation Procedure ................................................................................................ 40

7.3 Probability of Leakage ....................................................................................................... 41 7.3.1 Overview ...................................................................................................................... 41 7.3.2 Calculation of Probability of Leakage ....................................................................... 41 7.3.3 Calculation Procedure ................................................................................................ 43

7.4 Consequence of PRD Failure to Open .............................................................................. 44 7.4.1 General ......................................................................................................................... 44 7.4.2 Damage State of the Protected Equipment .............................................................. 44 7.4.3 Overpressure Potential for Overpressure Demand Cases ..................................... 44 7.4.4 Multiple Relief Device Installations ........................................................................... 45 7.4.5 Calculation of Consequence of Failure to Open ..................................................... 45 7.4.6 Calculation Procedure ................................................................................................ 46

7.5 Consequence of Leakage .................................................................................................. 46 7.5.1 General ......................................................................................................................... 46 7.5.2 Estimation of PRD Leakage Rate .............................................................................. 47 7.5.3 Estimation of Leakage Duration ................................................................................ 47 7.5.4 Credit for Recovery of Leaking Fluid ........................................................................ 47 7.5.5 Cost of Lost Inventory ................................................................................................ 47 7.5.6 Environmental Costs .................................................................................................. 48 7.5.7 Costs of Shutdown to Repair PRD ............................................................................ 48 7.5.8 Cost of Lost Production ............................................................................................. 48 7.5.9 Calculation of Leakage Consequence ...................................................................... 48 7.5.10 Calculation Procedure ................................................................................................ 49

7.6 Risk Analysis ...................................................................................................................... 49 7.6.1 Risk from Failure to Open .......................................................................................... 49 7.6.2 Risk from Leakage ...................................................................................................... 50 7.6.3 Total Risk ..................................................................................................................... 50 7.6.4 Calculation Procedure ................................................................................................ 50

7.7 Inspection Planning Based on Risk Analysis .................................................................. 50 7.7.1 Risk Based Inspection Intervals ................................................................................ 50 7.7.2 Effect of PRD Inspection, Testing and Overhaul on Risk Curve ........................... 50 7.7.3 Effect of PRD Testing without Overhaul on Risk Curve ......................................... 51

7.8 Nomenclature ...................................................................................................................... 52 7.9 Tables................................................................................................................................... 55 7.10 Figures ................................................................................................................................. 70

8 HEAT EXCHANGER TUBE BUNDLES ...................................................................................... 77 8.1 General ................................................................................................................................ 77

8.1.1 Overview ...................................................................................................................... 77 8.1.2 Background ................................................................................................................. 77 8.1.3 Basis of Model ............................................................................................................. 77 8.1.4 Required and Optional Data ...................................................................................... 77

8.2 Methodology Overview ...................................................................................................... 77 8.2.1 General ......................................................................................................................... 77

8.3 Probability of Failure .......................................................................................................... 78 8.3.1 Definition of Bundle Failure ....................................................................................... 78 8.3.2 Probability of Failure Using Weibull Distribution .................................................... 78 8.3.3 Exchanger Bundle Reliability Library or Seed Database........................................ 79 8.3.4 POF using the Owner-User Supplied Weibull Parameters ..................................... 81 8.3.5 POF using the User Supplied MTTF .......................................................................... 81 8.3.6 POF calculated using Specific Bundle History ........................................................ 81

8.4 Consequence of Failure ..................................................................................................... 81 8.4.1 Calculation Method ..................................................................................................... 81 8.4.2 Example ....................................................................................................................... 82

8.5 Risk Analysis ...................................................................................................................... 82 8.5.1 General ......................................................................................................................... 82

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8.5.2 Risk Matrix ................................................................................................................... 82 8.6 Inspection Planning Based on Risk Analysis .................................................................. 83

8.6.1 Use of Risk Target in Inspection Planning ............................................................... 83 8.6.2 Example ....................................................................................................................... 83 8.6.3 Inspection Planning Without Inspection History (First Inspection Date) ............. 83 8.6.4 Inspection Planning with Inspection History ........................................................... 84 8.6.5 Effects of Bundle Life Extension Efforts .................................................................. 86 8.6.6 Future Inspection Recommendation ........................................................................ 87

8.7 Bundle Inspect/Replacement Decisions using Cost Benefit Analysis ......................... 87 8.7.1 General ......................................................................................................................... 87 8.7.2 Decision to Inspect or Replace at Upcoming Shutdown ........................................ 87 8.7.3 Decision for Type of Inspection ................................................................................ 88 8.7.4 Optimal Bundle Replacement Frequency................................................................. 88

8.8 Nomenclature ...................................................................................................................... 90 8.9 Tables................................................................................................................................... 92 8.10 Figures ............................................................................................................................... 102

1-4


PART 2

DETERMINATION OF PROBABILITY OF FAILURE IN AN API RBI ASSESSMENT

2-1


PART CONTENTS 1 SCOPE ........................................................................................................................................ 2-8 2 REFERENCES ............................................................................................................................ 2-8 3 DEFINTIONS ............................................................................................................................... 2-9 4 PROBABILITY OF FAILURE CALCULATIONS ........................................................................ 2-9

4.1 Overview ............................................................................................................................. 2-9 4.2 Calculation of Probability of Failure ................................................................................ 2-9 4.3 Generic Failure Frequency ............................................................................................. 2-10 4.4 Damage Factor ................................................................................................................. 2-10

4.4.1 Overview ................................................................................................................... 2-10 4.4.2 Damage Factor Combination for Multiple Damage Mechanisms ....................... 2-11 4.4.3 Inspection Effectiveness Category ........................................................................ 2-12

4.5 Management Systems Factor ......................................................................................... 2-12 4.5.1 General ...................................................................................................................... 2-12 4.5.2 Overview ................................................................................................................... 2-12 4.5.3 Auditing Technique ................................................................................................. 2-13 4.5.4 Calculation of the Management Systems Factor .................................................. 2-13

4.6 Nomenclature ................................................................................................................... 2-14 4.7 Tables................................................................................................................................ 2-16

5 THINNING DAMAGE FACTOR ................................................................................................ 2-20 5.1 Scope ................................................................................................................................ 2-20 5.2 Screening Criteria ............................................................................................................ 2-20 5.3 Required Data .................................................................................................................. 2-20 5.4 Basic Assumptions ......................................................................................................... 2-20 5.5 Determination of the Damage Factor ............................................................................. 2-20

5.5.1 Overview ................................................................................................................... 2-20 5.5.2 Inspection Effectiveness ......................................................................................... 2-20 5.5.3 Calculation of the Damage Factor .......................................................................... 2-21

5.6 Nomenclature ................................................................................................................... 2-23 5.7 Tables................................................................................................................................ 2-24 5.8 Figures .............................................................................................................................. 2-37

6 COMPONENT LINING DAMAGE FACTOR ............................................................................. 2-38 6.1 Scope ................................................................................................................................ 2-38 6.2 Screening Criteria ............................................................................................................ 2-38 6.3 Required Data .................................................................................................................. 2-38 6.4 Basic Assumptions ......................................................................................................... 2-38 6.5 Determination of the Damage Factor ............................................................................. 2-38

6.5.1 Overview ................................................................................................................... 2-38 6.5.2 Calculation of the Damage Factor .......................................................................... 2-38

6.6 Nomenclature ................................................................................................................... 2-39 6.7 Tables................................................................................................................................ 2-40 6.8 Figures .............................................................................................................................. 2-45

7 SCC DAMAGE FACTOR – CAUSTIC CRACKING ................................................................. 2-46 7.1 Scope ................................................................................................................................ 2-46 7.2 Description of Damage .................................................................................................... 2-46 7.3 Screening Criteria ............................................................................................................ 2-46 7.4 Required Data .................................................................................................................. 2-46 7.5 Basic Assumptions ......................................................................................................... 2-46 7.6 Determination of the Damage Factor ............................................................................. 2-47


7.7 Nomenclature ................................................................................................................... 2-48 7.8 References ....................................................................................................................... 2-48 7.9 Tables................................................................................................................................ 2-49 7.10 Figures .............................................................................................................................. 2-52

2-2


8 SCC DAMAGE FACTOR – AMINE CRACKING ...................................................................... 2-55 8.1 Scope ................................................................................................................................ 2-55 8.2 Description of Damage .................................................................................................... 2-55 8.3 Screening Criteria ............................................................................................................ 2-55 8.4 Required Data .................................................................................................................. 2-56 8.5 Basic Assumptions ......................................................................................................... 2-56 8.6 Determination of the Damage Factor ............................................................................. 2-56



9 SCC DAMAGE FACTOR – SULFIDE STRESS CRACKING .................................................. 2-61 9.1 Scope ................................................................................................................................ 2-61 9.2 Description of Damage .................................................................................................... 2-61 9.3 Screening Criteria ............................................................................................................ 2-61 9.4 Required Data .................................................................................................................. 2-61 9.5 Basic Assumptions ......................................................................................................... 2-61 9.6 Determination of the Damage Factor ............................................................................. 2-62



10 SCC DAMAGE FACTOR – HIC/SOHIC-H2S ............................................................................ 2-68 10.1 Scope ................................................................................................................................ 2-68 10.2 Description of Damage .................................................................................................... 2-68 10.3 Screening Criteria ............................................................................................................ 2-69 10.4 Required Data .................................................................................................................. 2-69 10.5 Basic Assumptions ......................................................................................................... 2-69 10.6 Determination of the Damage Factor ............................................................................. 2-69



11 SCC DAMAGE FACTOR – CARBONATE CRACKING .......................................................... 2-75 11.1 Scope ................................................................................................................................ 2-75 11.2 Description of Damage .................................................................................................... 2-75 11.3 Screening Criteria ............................................................................................................ 2-75 11.4 Required Data .................................................................................................................. 2-75 11.5 Basic Assumptions ......................................................................................................... 2-76 11.6 Determination of the Damage Factor ............................................................................. 2-76



2-3


12 SCC DAMAGE FACTOR – PTA CRACKING .......................................................................... 2-81 12.1 Scope ................................................................................................................................ 2-81 12.2 Description of Damage .................................................................................................... 2-81 12.3 Screening Criteria ............................................................................................................ 2-81 12.4 Required Data .................................................................................................................. 2-81 12.5 Basic Assumptions ......................................................................................................... 2-81 12.6 Determination of the Damage Factor ............................................................................. 2-82



13 SCC DAMAGE FACTOR – CLSCC ......................................................................................... 2-88 13.1 Scope ................................................................................................................................ 2-88 13.2 Description of Damage .................................................................................................... 2-88 13.3 Screening Criteria ............................................................................................................ 2-88 13.4 Required Data .................................................................................................................. 2-88 13.5 Basic Assumptions ......................................................................................................... 2-89 13.6 Determination of the Damage Factor ............................................................................. 2-89



14 SCC DAMAGE FACTOR – HSC-HF ........................................................................................ 2-95 14.1 Scope ................................................................................................................................ 2-95 14.2 Description of Damage .................................................................................................... 2-95 14.3 Screening Criteria ............................................................................................................ 2-95 14.4 Required Data .................................................................................................................. 2-95 14.5 Basic Assumptions ......................................................................................................... 2-95 14.6 Determination of the Damage Factor ............................................................................. 2-96


14.7 Nomenclature ................................................................................................................... 2-97 14.8 References ....................................................................................................................... 2-97 14.9 Tables................................................................................................................................ 2-98 14.10 Figures ............................................................................................................................ 2-100

15 SCC DAMAGE FACTOR – HIC/SOHIC-HF ........................................................................... 2-101

15.1 Scope .............................................................................................................................. 2-101 15.2 Description of Damage .................................................................................................. 2-101 15.3 Screening Criteria .......................................................................................................... 2-101 15.4 Required Data ................................................................................................................ 2-101 15.5 Basic Assumptions ....................................................................................................... 2-101 15.6 Determination of the Damage Factor ........................................................................... 2-102

15.6.1 Overview ................................................................................................................. 2-102 15.6.2 Inspection Effectiveness ....................................................................................... 2-102 15.6.3 Calculation of the Damage Factor ........................................................................ 2-102

2-4


15.7 Nomenclature ................................................................................................................. 2-103 15.8 References ..................................................................................................................... 2-103 15.9 Tables.............................................................................................................................. 2-104 15.10 Figures ............................................................................................................................ 2-107

16 EXTERNAL CORROSION DAMAGE FACTOR – FERRITIC COMPONENT ....................... 2-108 16.1 Scope .............................................................................................................................. 2-108 16.2 Description of Damage .................................................................................................. 2-108 16.3 Screening Criteria .......................................................................................................... 2-108 16.4 Required Data ................................................................................................................ 2-108 16.5 Basic Assumption ......................................................................................................... 2-108 16.6 Determination of the Damage Factor ........................................................................... 2-108


16.7 Nomenclature ................................................................................................................. 2-110 16.8 Tables.............................................................................................................................. 2-111 16.9 Figures ............................................................................................................................ 2-113

17 CUI DAMAGE FACTOR – FERRITIC COMPONENT ............................................................ 2-114 17.1 Scope .............................................................................................................................. 2-114 17.2 Description of Damage .................................................................................................. 2-114 17.3 Screening Criteria .......................................................................................................... 2-114 17.4 Required Data ................................................................................................................ 2-115 17.5 Basic Assumption ......................................................................................................... 2-115 17.6 Determination of the Damage Factor ........................................................................... 2-115



18 EXTERNAL CLSCC DAMAGE FACTOR – AUSTENITIC COMPONENT ............................ 2-125 18.1 Scope .............................................................................................................................. 2-125 18.2 Description of Damage .................................................................................................. 2-125 18.3 Screening Criteria .......................................................................................................... 2-125 18.4 Required Data ................................................................................................................ 2-125 18.5 Basic Assumption ......................................................................................................... 2-125 18.6 Determination of the Damage Factor ........................................................................... 2-125



19 EXTERNAL CUI CLSCC DAMAGE FACTOR – AUSTENITIC COMPONENT ..................... 2-130 19.1 Scope .............................................................................................................................. 2-130 19.2 Description of Damage .................................................................................................. 2-130 19.3 Screening Criteria .......................................................................................................... 2-130 19.4 Required Data ................................................................................................................ 2-130 19.5 Basic Assumption ......................................................................................................... 2-130 19.6 Determination of the Damage Factor ........................................................................... 2-130



2-5


20 HTHA DAMAGE FACTOR ...................................................................................................... 2-137 20.1 Scope .............................................................................................................................. 2-137 20.2 Description of Damage .................................................................................................. 2-137 20.3 Screening Criteria .......................................................................................................... 2-137 20.4 Required Data ................................................................................................................ 2-137 20.5 Basic Assumption ......................................................................................................... 2-138 20.6 Determination of the Damage Factor ........................................................................... 2-138



21 BRITTLE FACTURE DAMAGE FACTOR .............................................................................. 2-144 21.1 Scope .............................................................................................................................. 2-144 21.2 Description of Damage .................................................................................................. 2-144 21.3 Screening Criteria .......................................................................................................... 2-144 21.4 Required Data ................................................................................................................ 2-144 21.5 Basic Assumption ......................................................................................................... 2-144 21.6 Determination of the Damage Factor ........................................................................... 2-145



22 TEMPER EMBRITTLEMENT DAMAGE FACTOR ................................................................ 2-157 22.1 Scope .............................................................................................................................. 2-157 22.2 Description of Damage .................................................................................................. 2-157 22.3 Screening Criteria .......................................................................................................... 2-157 22.4 Required Data ................................................................................................................ 2-157 22.5 Basic Assumption ......................................................................................................... 2-157 22.6 Determination of the Damage Factor ........................................................................... 2-158



23 885 EMBRITTLEMENT DAMAGE FACTOR .......................................................................... 2-162 23.1 Scope .............................................................................................................................. 2-162 23.2 Description of Damage .................................................................................................. 2-162 23.3 Screening Criteria .......................................................................................................... 2-162 23.4 Required Data ................................................................................................................ 2-162 23.5 Basic Assumption ......................................................................................................... 2-162 23.6 Determination of the Damage Factor ........................................................................... 2-163



2-6


24 SIGMA PHASE EMBRITTLEMENT DAMAGE FACTOR ...................................................... 2-166 24.1 Scope .............................................................................................................................. 2-166 24.2 Description of Damage .................................................................................................. 2-166 24.3 Screening Criteria .......................................................................................................... 2-167 24.4 Required Data ................................................................................................................ 2-167 24.5 Basic Assumption ......................................................................................................... 2-167 24.6 Determination of the Damage Factor ........................................................................... 2-167



25 PIPING MECHANICAL FATIGUE DAMAGE FACTOR ......................................................... 2-172 25.1 Scope .............................................................................................................................. 2-172 25.2 Description of Damage .................................................................................................. 2-172 25.3 Screening Criteria .......................................................................................................... 2-172 25.4 Required Data ................................................................................................................ 2-172 25.5 Basic Assumption ......................................................................................................... 2-172 25.6 Determination of the Damage Factor ........................................................................... 2-173



2-7


3-1

API RP 581 PART 3

CONSEQUENCE ANALYSIS IN AN API RBI ASSESSMENT


3-2

PART CONTENTS 1 SCOPE ........................................................................................................................................ 3-6 2 REFERENCES ............................................................................................................................ 3-6 3 DEFINITIONS.............................................................................................................................. 3-7 4 GENERAL ................................................................................................................................. 3-10

4.1 Overview........................................................................................................................... 3-10 4.1.1 Consequence Categories........................................................................................ 3-10 4.1.2 Collateral Damage.................................................................................................... 3-10

4.2 Overview of Consequence Analyses in API RBI .......................................................... 3-10 4.2.1 Level 1 Consequence Analysis .............................................................................. 3-10 4.2.2 Level 2 Consequence Analysis .............................................................................. 3-11

4.3 Consequence Analysis for Storage Tank Bottoms and Shell Courses ..................... 3-11 4.4 Consequence Analysis Calculation Procedure............................................................ 3-11 4.5 Area and Financial Based Consequence Analyses ..................................................... 3-11 4.6 Use of Atmospheric Dispersion Modeling .................................................................... 3-12 4.7 Tables................................................................................................................................ 3-13 4.8 Figures.............................................................................................................................. 3-15

5 CONSEQUENCE ANALYSIS – LEVEL 1 ................................................................................ 3-16 5.1 Determine the Representative Fluid and Associated Properties ............................... 3-16

5.1.1 Representative Fluids.............................................................................................. 3-16 5.1.2 Fluid Properties........................................................................................................ 3-16 5.1.3 Choice of Representative Fluids for Acids and Caustic Fluids .......................... 3-16 5.1.4 Estimation of Ideal Gas Specific Heat Capacity Ratio ......................................... 3-16 5.1.5 Flammable Fluid Types ........................................................................................... 3-17 5.1.6 Release Phase.......................................................................................................... 3-17 5.1.7 Calculation Procedure............................................................................................. 3-17

5.2 Release Hole Size Selection ........................................................................................... 3-18 5.2.1 General...................................................................................................................... 3-18 5.2.2 Calculation Procedure............................................................................................. 3-18

5.3 Release Rate Calculation................................................................................................ 3-18 5.3.1 Overview ................................................................................................................... 3-18 5.3.2 Liquid Release Rate Calculation ............................................................................ 3-19 5.3.3 Vapor Release Rate Equations............................................................................... 3-19 5.3.4 Calculation Procedure............................................................................................. 3-20

5.4 Estimate the Fluid Inventory Available for Release ..................................................... 3-20 5.4.1 Overview ................................................................................................................... 3-20 5.4.2 Maximum Mass Available for Release (Available Mass)...................................... 3-20 5.4.3 Calculation Procedure............................................................................................. 3-21

5.5 Determine the Release Type (Continuous or Instantaneous)..................................... 3-21 5.5.1 Release Type – Instantaneous or Continuous...................................................... 3-21 5.5.2 Calculation Procedure............................................................................................. 3-22

5.6 Estimate the Impact of Detection and Isolation Systems on Release Magnitude .... 3-22 5.6.1 Overview ................................................................................................................... 3-22 5.6.2 Assessing Detection and Isolation Systems ........................................................ 3-22 5.6.3 Impact on Release Magnitude ................................................................................ 3-22 5.6.4 Impact on Release Duration ................................................................................... 3-22 5.6.5 Releases to the Environment ................................................................................. 3-23 5.6.6 Calculation Procedure............................................................................................. 3-23

5.7 Determine the Release Rate and Mass for Consequence Analysis ........................... 3-23 5.7.1 Continuous Release Rate ....................................................................................... 3-23 5.7.2 Instantaneous Release Mass.................................................................................. 3-23 5.7.3 Calculation Procedure............................................................................................. 3-24

5.8 Determine Flammable and Explosive Consequences ................................................. 3-24 5.8.1 Overview ................................................................................................................... 3-24 5.8.2 Consequence Area Equations................................................................................ 3-24 5.8.3 Limit Liquid Release Consequence Area to 929 m2 [10,000 ft2] .......................... 3-25 5.8.4 Adjustment of Consequence Areas to Account for Mitigation Systems ........... 3-26


3-3

5.8.5 Adjustment of Consequence Areas for Energy Efficiencies............................... 3-26 5.8.6 Blending of Results Based on Release Type........................................................ 3-26 5.8.7 Blending of Results Based on AIT ......................................................................... 3-27 5.8.8 Determination of Final Flammable Consequence Areas ..................................... 3-27 5.8.9 Calculation Procedure............................................................................................. 3-28

5.9 Determine Toxic Consequences .................................................................................... 3-33 5.9.1 General...................................................................................................................... 3-33 5.9.2 Common Refining Toxic Materials......................................................................... 3-33 5.9.3 Common Chemical Industry Toxic Materials........................................................ 3-33 5.9.4 Representative Fluids for Toxic Mixtures ............................................................. 3-33 5.9.5 Determination of the Toxic Release Rate and Mass ............................................ 3-33 5.9.6 Estimation of Toxic Consequence Area for HF Acid and H2S............................. 3-34 5.9.7 Estimation of Toxic Consequence Area for Ammonia and Chlorine ................. 3-34 5.9.8 Estimation of Toxic Consequence Area for Additional Common Chemicals.... 3-35 5.9.9 Material Concentration Cut-Off .............................................................................. 3-35 5.9.10 Release Duration...................................................................................................... 3-35 5.9.11 Toxic Outcome Probabilities .................................................................................. 3-36 5.9.12 Consequences of Releases Containing Multiple Toxic Chemicals .................... 3-36 5.9.13 Effects of Mitigation Measures on Toxic Releases .............................................. 3-36 5.9.14 Determination of Final Toxic Consequence Areas............................................... 3-36 5.9.15 Calculation Procedure............................................................................................. 3-37

5.10 Determine Non-Flammable Non-Toxic Consequences................................................ 3-37 5.10.1 General...................................................................................................................... 3-37 5.10.2 Consequences of Steam Leaks.............................................................................. 3-37 5.10.3 Consequences of Acid and Caustic Leaks ........................................................... 3-38 5.10.4 Blending of Results Based on Release Type........................................................ 3-38 5.10.5 Determination of Final Non-Flammable, Non-Toxic Consequence Areas ......... 3-39 5.10.6 Calculation Procedure............................................................................................. 3-39

5.11 Determine the Component Damage and Personnel Injury Consequence Areas...... 3-39 5.11.1 Overview ................................................................................................................... 3-39 5.11.2 Final Component Damage Consequence Area..................................................... 3-40 5.11.3 Final Personnel Injury Consequence Area ........................................................... 3-40 5.11.4 Final Consequence Area......................................................................................... 3-40 5.11.5 Calculation Procedure............................................................................................. 3-40

5.12 Determine the Financial Consequences ....................................................................... 3-40 5.12.1 Overview ................................................................................................................... 3-40 5.12.2 Component Damage Cost....................................................................................... 3-41 5.12.3 Damage Costs to Surrounding Equipment in Affected Area .............................. 3-42 5.12.4 Business Interruption Costs................................................................................... 3-42 5.12.5 Potential Injury Costs.............................................................................................. 3-43 5.12.6 Environmental Cleanup Costs................................................................................ 3-43 5.12.7 Calculation Procedure............................................................................................. 3-44

5.13 Nomenclature................................................................................................................... 3-46 5.14 Tables................................................................................................................................ 3-50 5.15 Figures.............................................................................................................................. 3-76

6 CONSEQUENCE ANALYSIS – LEVEL 2 ................................................................................ 3-78 6.1 Determine the Fluid Composition and Associated Properties ................................... 3-78

6.1.1 General...................................................................................................................... 3-78 6.1.2 Required Properties at Storage Conditions.......................................................... 3-78 6.1.3 Required Properties at Flashed Conditions.......................................................... 3-79 6.1.4 Calculation Procedure............................................................................................. 3-79

6.2 Release Hole Size Selection ........................................................................................... 3-80 6.2.1 General...................................................................................................................... 3-80 6.2.2 Calculation Procedure............................................................................................. 3-80

6.3 Release Rate Calculation................................................................................................ 3-80 6.3.1 Source Term Modeling ............................................................................................ 3-80 6.3.2 Determining the Release Phase ............................................................................. 3-80


3-4

6.3.3 Vapor Release Source............................................................................................. 3-81 6.3.4 Two-Phase Release Source .................................................................................... 3-81 6.3.5 Liquid Release Source ............................................................................................ 3-81 6.3.6 Calculation Procedure............................................................................................. 3-81

6.4 Estimate the Fluid Inventory Available for Release ..................................................... 3-82 6.4.1 General...................................................................................................................... 3-82 6.4.2 Calculation Procedure............................................................................................. 3-82

6.5 Determine Release Type ................................................................................................. 3-82 6.5.1 General...................................................................................................................... 3-82 6.5.2 Calculation Procedure............................................................................................. 3-82

6.6 Estimate the Impact of Detection and Isolation Systems on Release Magnitude .... 3-82 6.6.1 General...................................................................................................................... 3-82 6.6.2 Calculation Procedure............................................................................................. 3-82

6.7 Determine the Release Rate and Mass for Consequence Analysis ........................... 3-82 6.7.1 General...................................................................................................................... 3-82 6.7.2 Aerosol and Rainout Modeling............................................................................... 3-82 6.7.3 Calculation of Jet Release Rate and Pool Release Rate...................................... 3-83 6.7.4 Vapor Sources from Boiling or Non-Boiling Pools .............................................. 3-83 6.7.5 Cloud Dispersion Modeling .................................................................................... 3-84 6.7.6 Calculation Procedure............................................................................................. 3-84

6.8 Determine Flammable and Explosive Consequences ................................................. 3-85 6.8.1 Event Tree Calculations .......................................................................................... 3-85 6.8.2 Pool Fires.................................................................................................................. 3-90 6.8.3 Jet Fires .................................................................................................................... 3-93 6.8.4 Fireballs .................................................................................................................... 3-94 6.8.5 Vapor Cloud Explosions (VCEs) ............................................................................ 3-96 6.8.6 Flash Fires ................................................................................................................ 3-99 6.8.7 Determination of Flammable Consequence for Each Release Case (Hole Size)3-99 6.8.8 Determination of Final Flammable Consequence Areas ..................................... 3-99 6.8.9 Calculation Procedure........................................................................................... 3-100

6.9 Determine Toxic Consequences .................................................................................. 3-105 6.9.1 General.................................................................................................................... 3-105 6.9.2 Toxic Impact Criteria Used in Level 2 .................................................................. 3-106 6.9.3 Release Duration.................................................................................................... 3-107 6.9.4 Toxic Event Probabilities ...................................................................................... 3-107 6.9.5 Consequences of Releases Containing Multiple Toxic Chemicals .................. 3-107 6.9.6 Toxic Consequence Area...................................................................................... 3-107 6.9.7 Determination of Final Toxic Consequence Areas............................................. 3-108 6.9.8 Calculation Procedure........................................................................................... 3-108

6.10 Determine Non-Flammable Non-Toxic Consequences.............................................. 3-109 6.10.1 General.................................................................................................................... 3-109 6.10.2 Physical Explosions .............................................................................................. 3-109 6.10.3 BLEVEs ................................................................................................................... 3-110 6.10.4 Steam Leaks and Chemical Spills........................................................................ 3-110 6.10.5 Determination of Final Non-Flammable, Non-Toxic Consequence Areas ....... 3-110 6.10.6 Calculation Procedure........................................................................................... 3-111

6.11 Determine the Component Damage and Personnel Injury Consequence Areas.... 3-113 6.11.1 Overview ................................................................................................................. 3-113 6.11.2 Final Component Damage Consequence Area................................................... 3-113 6.11.3 Final Personnel Injury Consequence Area ......................................................... 3-113 6.11.4 Final Consequence Area....................................................................................... 3-113 6.11.5 Calculation Procedure........................................................................................... 3-114

6.12 Determine the Financial Consequence ....................................................................... 3-114 6.12.1 General.................................................................................................................... 3-114 6.12.2 Calculation Procedure........................................................................................... 3-114

6.13 Nomenclature................................................................................................................. 3-115 6.14 Tables.............................................................................................................................. 3-122


3-5

6.15 Figures............................................................................................................................ 3-125 7 CONSEQUENCE ANALYSIS – ATMOSPHERIC STORAGE TANKS.................................. 3-133

7.1 Determine the Representative Fluid and Associated Properties ............................. 3-133 7.1.1 Representative Fluids............................................................................................ 3-133 7.1.2 Liquid Density and Dynamic Viscosity................................................................ 3-133 7.1.3 Hydraulic Conductivity.......................................................................................... 3-133 7.1.4 Fluid Seepage Velocity.......................................................................................... 3-133 7.1.5 Calculation Procedure........................................................................................... 3-133

7.2 Release Hole Size Selection ......................................................................................... 3-134 7.2.1 Overview ................................................................................................................. 3-134 7.2.2 Calculation Procedure........................................................................................... 3-134

7.3 Release Rate Calculation.............................................................................................. 3-134 7.3.1 Overview ................................................................................................................. 3-134 7.3.2 Tank Shell Course.................................................................................................. 3-134 7.3.3 Tank Bottom........................................................................................................... 3-135 7.3.4 Calculation Procedure – Tank Shell Course ....................................................... 3-135 7.3.5 Calculation Procedure – Tank Bottom................................................................. 3-135

7.4 Estimate the Inventory Volume Available for Release............................................... 3-136 7.4.1 Overview ................................................................................................................. 3-136 7.4.2 Calculation Procedure – Tank Shell Course ....................................................... 3-136 7.4.3 Calculation Procedure – Tank Floor .................................................................... 3-136

7.5 Determine the Type of Release .................................................................................... 3-137 7.6 Estimate the Impact of Detection and Isolation Systems on Release Magnitude .. 3-137 7.7 Determine the Release Rate and Volume for the Consequence Analysis............... 3-137

7.7.1 Overview ................................................................................................................. 3-137 7.7.2 Calculation Procedure – Tank Shell Course ....................................................... 3-137 7.7.3 Calculation Procedure – Tank Bottom................................................................. 3-138

7.8 Determine Flammable and Explosive Consequences ............................................... 3-138 7.9 Determine Toxic Consequences .................................................................................. 3-138 7.10 Determine Non-Flammable Non-toxic Consequences............................................... 3-138 7.11 Determine Component damage and Personnel Injury Consequences.................... 3-139 7.12 Determine the Financial Consequences ..................................................................... 3-139

7.12.1 Overview ................................................................................................................. 3-139 7.12.2 Calculation Procedure – Tank Shell Course ....................................................... 3-139 7.12.3 Calculation procedures – Tank Bottom............................................................... 3-141

7.13 Nomenclature................................................................................................................. 3-143 7.14 Tables.............................................................................................................................. 3-146 7.15 Figures............................................................................................................................ 3-151

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