Guidelines for Pressure Relief and Effluent Handling Systems

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.

• List of Figures xvList of Tables xxiPreface xxiiiAcknowledgements xxvIn Memoriam xxviiFiles on the Web Accompanying This Book xxixIntroduction 11.1 Objective 11.2 Scope 21.3 Design Codes and Regulations, and Sources of Information 31.4 Organization of This Book 51.5 General Pressure and Relief System Design Criteria 71.5.1 Process Hazard Analysis 81.5.2 Process Safety Information 91.5.3 Problems Inherent in Pressure Relief and Effluent Handling Systems 11Relief Design Criteria and Strategy 132.1 Limitations of the Technology 142.2 General Pressure Relief Strategy 142.2.1 Mechanism of Pressure Relief 142.2.2 Approach to Design 152.2.3 Limitations of Systems Actuated by Pressure 172.3 Codes, Standards, and Guidelines 192.3.1 Scope of Principal USA Documents 192.3.2 General Provisions 242.3.3 Protection by System Design 362.4 Relief Device Types and Operation 402.4.1 General Terminology 412.4.2 Pressure Relief Valves 412.4.3 Rupture Disk Devices 542.4.4 Devices in Combination (Series) 632.4.5 Low Pressure Relief Valves & Vents 642.4.6 Miscellaneous Relief System Components 702.4.7 Selection of Pressure Relief Devices 712.5 Relief System Layout 752.5.1 General Code Requirements 752.5.2 Pressure Relief Valves 772.5.3 Rupture Disk Devices 802.5.4 Low-Pressure Devices 802.5.5 Devices in Series 812.5.6 Devices in Parallel 872.5.7 Header Systems 882.5.8 Mechanical Integrity 882.5.9 Material Selection 882.5.10 Drainage and Freeze-up Provisions 892.5.11 Noise 892.6 Design Flows and Code Provisions 902.6.1 Safety Valves 922.6.2 Incompressible Liquid Flow 952.6.3 Low Pressure Devices 952.6.4 Rupture Disk Devices 952.6.5 Devices in Combination 992.6.6 Miscellaneous Nonreclosing Devices 1002.7 Scenario Selection Considerations 1002.7.1 Events Requiring Relief Due to Overpressure 1012.7.2 Design Scenarios 1022.8 Fluid Properties and System Characterization 1042.8.1 Property Data Sources/Determination/Estimation 1052.8.2 Pure-Component Properties 1052.8.3 Mixture Properties 1062.8.4 Phase Behavior 1062.8.5 Chemical Reaction 1082.8.6 Miscellaneous Fluid Characteristics 1122.9 Fluid Behavior in Vessel 1132.9.1 Accounting for Chemical Reactions 1132.9.2 Two-Phase Venting Conditions and Effects 1142.10 Flow of Fluids through Relief Systems 1162.10.1 Conditions for Two-Phase Flow 1162.10.2 Nature of Compressible Flow 1172.10.3 Stagnation Pressure and Non-recoverable Pressure Loss 1212.10.4 Flow Rate to Effluent Handling System 1212.11 Relief System Reliability 1222.11.1 Relief Device Reliability 1222.11.2 System Reliability 125Requirements for Relief System Design 1313.1 Introduction 1313.1.1 Required Background 1323.2 Vessel Venting Background 1333.2.1 General Considerations 1333.2.2 Schematics and Principle Variables, Properties and Parameters 1353.2.3 Basic Mass and Energy Balances 1403.2.4 Physical and Thermodynamic Properties 1483.2.5 Energy Input or Output 1533.2.6 Solution Methods Using Computer Tools 1563.2.7 Mass and Energy Balance Simplifications 1563.2.8 Limiting Cases 1583.2.9 Vapor/Liquid Disengagement 1603.3 Venting Requirements for Nonreacting Cases 1713.3.1 Heating or Cooling of a Constant Volume Vessel 1713.3.2 Excess Inflow/Outflow 1873.3.3 Additional Techniques and Considerations 1903.4 Calorimetry for Emergency Relief System Design 1903.4.1 Executive Summary 1903.4.2 Runaway Reaction Effects 1913.4.3 Reaction Basics 1923.4.4 Reaction Screening and Chemistry Identification 1963.4.5 Measuring Reaction Rates 1973.4.6 Experimental Test Design 2223.4.7 Calorimetry Data Interpretation and Analysis 2343.5 Venting Requirements for Reactive Cases 2593.5.1 Executive Summary 2593.5.2 Overview of Reactive Relief Load 2603.5.3 Analytical Methods 2673.5.4 Dynamic Computer Modeling 2793.5.5 Closing Comment 282Methods for Relief System Design 2834.1 Introduction 2834.1.1 Relief System Sizing Computational Strategy and Tools for Relief Design 2834.2 Manual and Spreadsheet Methods for Relief Valve Sizing 2854.2.1 Relief Valve Sizing Fundamental Equations 2854.2.2 Two-Phase Flow Methods 2984.2.3 Relief Valve Sizing - Discharge Coefficient 3104.2.4 Relief Valve Sizing - Choking in Nozzle and Valve Exit 3144.3 Miscellaneous 3174.3.1 Low-Pressure Devices - Liquid Flow 3174.3.2 Low-Pressure Devices - Gas Flow 3184.3.3 Low-Pressure Devices - Two-Phase Flow 3204.3.4 Low-Pressure Devices - Associated Piping 3204.4 Piping 3214.4.1 Piping - Fundamental Equations 3224.4.2 Piping - Pipe Friction Factors 3224.4.3 Incompressible (Liquid) Flow 3284.4.4 Piping Adiabatic Compressible Flow 3294.4.5 Isothermal Compressible Flow 3334.4.6Homogeneous Two-Phase Pipe Flow 3344.4.7 Piping - Separated Two-Phase Flows 3464.4.8 Slip/Holdup 3474.4.9 Piping - Temperature Effects 3484.5 Rupture Disk Device Systems 3494.5.1 Rupture Disks - Nozzle Model 3494.5.2 Rupture Disks - Pipe Model 3494.6 Multiple Devices 3504.6.1 Multiple Devices in Parallel 3504.6.2 Multiple Devices - Rupture Disk Device Upstream of a PRV 3514.6.3 Multiple Devices - Rupture Disk Device Downstream of a PRV 3514.7 Worked Example Index 352Additional Considerations for Relief System Design 3555.1 Introduction 3555.2 Reaction Forces 3565.3 Background 3575.4 Selection of Design Case 3635.5 Design Methods 3635.5.1 Steady State Exit Force from Flow Discharging to the Atmosphere 3635.5.2 Dynamic Load Factor 3675.6 Selection of Design Flow Rate and Dynamic Load Factor 3675.6.1 Rupture Disks 3685.6.2 Safety Relief Valves 3705.7 Transient Forces on Relief Device Discharge Piping 3725.7.1 Liquid Relief 3735.7.2 Gas Relief 3765.7.3 Two-Phase Flow 3845.8 Pipe Tension 3855.8.1 Safety Relief Valves 3865.8.2 Rupture Disks 3875.9 Real Gases 3905.10 Changes in Pipe Size 3905.11 Location of Anchors 3905.12 Exit Geometry 3915.13 Worked Examples 392Handling Emergency Relief Effluents 3936.1 General Strategy 3956.2 Basis for Selection of Equipment 3996.3 Determining if Direct Discharge to Atmosphere is Acceptable 4016.4 Factors That Influence Selection of Effluent Treatment Systems 4036.4.1 Physical and Chemical Properties 4036.4.2 Two-Phase Flow and Foaming 4056.4.3 Passive or Active Systems 4066.4.4 Technology Status and Reliability 4076.4.5 Discharging to a Common Collection System 4086.4.6 Plant Geography 4096.4.7 Space Availability 4096.4.8Turndown 4096.4.9 Vapor-Liquid Separation 4106.4.10 Possible Condensation and Vapor-Condensate Hammer 4106.4.11 Time Availability 4116.4.12 Capital and Continuing Costs 4116.5 Methods of Effluent Handling 4116.5.1Containment 4116.5.2 Direct Discharge to Atmosphere 4156.5.3 Vapor-Liquid Separators 4156.5.4 Quench Tanks 4236.5.5 Scrubbers (Absorbers) 4296.5.6 Flares 432Design Methods for Handling Effluent from Emergency Relief Systems 4377.1 Design Basis Selection 4387.2 Total Containment Systems 4397.2.1 Containment in Original Vessel 4397.2.2 Containment in External Vessel (Dump Tank or Catch Tank) 4407.3 Relief Devices, Discharge Piping, and Collection Headers 4427.3.1 Corrosion 4437.3.2 Brittle Metal Fracture 4447.3.3 Deposition 4447.3.4 Vibration 4447.3.5 Cleaning 4457.4 Vapor-Liquid Gravity Separators 4457.4.1 Separator Inlet Velocity Considerations 4507.4.2 Horizontal Gravity Separators 4517.4.3 Vertical Gravity Separators 4607.4.4 Separator Safety Considerations and Features 4637.4.5 Separator Vessel Design and Instrumentation 4647.5 Cyclone Separators 4657.5.1 Droplet Removal Efficiency 4677.5.2 Design Procedure 4697.5.3 Cyclone Separator Sizing Procedure 4707.5.4 Alternate Cyclone Separator Design Procedure 4727.5.5 Cyclone Reaction Force 4757.6 Quench Pools 4767.6.1 Design Procedure Overview 4777.6.2 Design Parameter Interrelations 4827.6.3 Quench Pool Liquid Selection 4837.6.4 Quench Tank Operating Pressure 4847.6.5 Quench Pool Heat Balance 4857.6.6 Quench Pool Dimensions 4937.6.7 Sparger Design 4997.6.8 Handling Effluent from Multiple Relief Devices 5097.6.9 Reverse Flow Problems 5097.6.10 Vapor-Condensate Hammer 5107.6.11 Mechanical Design Loads 5107.6.12 Worked Example Index for Discharge Handling System Design 511Acronyms and Abbreviations 513Glossary 517Nomenclature 529Appendix A: SuperChems™ for DIERS Lite – Description and Instructions 541A.1 Scope 541A.2 Software Functions 543A.2.1 Source Term Flow Calculation 543A.2.2 Emergency Relief Requirement Calculations 544A.2.3 Physical Properties 545A.2.4 Piping Isometrics 546A.2.5 Specifying Vessel Designs 546A.3 Installing and Running SuperChems™ 547Appendix B: CCFlow, TPHEM and COMFLOW Description and Instructions 549B.1 Scope 549B.1.1 Uncertainties 550B.2 CCFlow Calculation Options 550B.2.1 Opening and Running CCFlow 552B.2.2 File Operations 552B.2.3 Help Files 554B.2.4 Other Operations 555B.2.5 CCFlow Input Menu Errata 556B.3 TPHEM Calculation Options 556B.3.1 Running TPHEM with File Input 560B.4 COMFLOW Calculation Options 562B.4.1 Running COMFLOW 563Appendix C: SuperChems™ for DIERS – Description and Instructions 565C.1 Scope 565C.2 Software Functions 567C.2.1 Main Menu Tabs 567C.2.2 Define Tab 568C.2.3 Dynamic Flow Simulation 570C.2.4 Steady-State Flow Calculations 571C.2.5 Properties Tab 572C.2.6 VLE Tab 574C.3 Installing and Running SuperChems™ 576Appendix D: Venting Requirements 577D.1 Worked Examples – Emergency Venting 579D.1.1 External Fire – Vapor Venting 580D.1.2 Tube Rupture 590D.1.3 Literature Examples for Non-Reactive Cases 596D.2 Venting Requirements for Reactive Cases 597D.3 Relief Valve Sizing Examples 599D.3.1 Incompressible Liquid Flow (with Viscosity Correction) 601D.3.2 Real Gas Flow 603D.3.3 Supercritical Fluid Flow 607D.3.4 Non-Flashing (Frozen) Choked Flow 609D.3.5 Non-Flashing (Frozen) Non-choked Flow 611D.3.6 Equilibrium Flow of Single-Component Fluid 614D.3.7 Non-Equilibrium Flow of Single-Component Fluid 616D.3.8 Multicomponent Fluid Flow 618D.3.9 Equilibrium Flow of One-Component Fluid (Low Subcooled Liquid Flow) 621D.3.10 Equilibrium Flow of Single-Component Fluid (Highly Subcooled Liquid Flow) 626D.3.11 Single-Component Vapor Flow with Retrograde Condensation 630D.4 Piping Flow Examples 634D.4.1 Two-Phase Gas-Liquid Flow with Conventional Multiple Chokes 635D.4.2 Real Gas Flow with Multiple Chokes 650D.4.3 Flow of High Viscosity Liquid 654D.5 Reaction Forces 658D.5.1 PRV with Viscous Liquid Flow – Steady Forces 658D.5.2 PRV with Real Gas Flow – Steady Forces 661D.5.3 RD with Liquid Flow – Steady and Transient Forces 664D.5.4 RD with Air Flow – Steady and Transient Forces 667D.5.5 PRV with Steam Flow – Steady and Transient Forces 670D.5.6 PRV with Two-Phase Flow – Steady and Transient Forces and Piping Design Pressure 673D.5.7 PRV with Two-Phase Flow – Steady and Transient Forces and Piping Design Pressure 675D.5.8 RD with Two-Phase Flow – Steady and Transient Forces and Piping Design Pressure 678Appendix E: Worked Examples – Effluent Handling 681E.1 Phase Separator and Quench Tank Design Examples 681E.1.1 Example Problem Statement 682E.1.2 Given Conditions 683E.1.3 Quench Pool Design 692E.1.4 Gravity Separator Design 706E.1.5 Cyclone Separator Design 710E.1.6 Summary 715References 717Index 743