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 xv

List of Tables xxi

Preface xxiii

Acknowledgements xxv

In Memoriam xxvii

Files on the Web Accompanying This Book xxix

Introduction 1

1.1 Objective 1

1.2 Scope 2

1.3 Design Codes and Regulations, and Sources of Information 3

1.4 Organization of This Book 5

1.5 General Pressure and Relief System Design Criteria 7

1.5.1 Process Hazard Analysis 8

1.5.2 Process Safety Information 9

1.5.3 Problems Inherent in Pressure Relief and Effluent Handling Systems 11

Relief Design Criteria and Strategy 13

2.1 Limitations of the Technology 14

2.2 General Pressure Relief Strategy 14

2.2.1 Mechanism of Pressure Relief 14

2.2.2 Approach to Design 15

2.2.3 Limitations of Systems Actuated by Pressure 17

2.3 Codes, Standards, and Guidelines 19

2.3.1 Scope of Principal USA Documents 19

2.3.2 General Provisions 24

2.3.3 Protection by System Design 36

2.4 Relief Device Types and Operation 40

2.4.1 General Terminology 41

2.4.2 Pressure Relief Valves 41

2.4.3 Rupture Disk Devices 54

2.4.4 Devices in Combination (Series) 63

2.4.5 Low Pressure Relief Valves & Vents 64

2.4.6 Miscellaneous Relief System Components 70

2.4.7 Selection of Pressure Relief Devices 71

2.5 Relief System Layout 75

2.5.1 General Code Requirements 75

2.5.2 Pressure Relief Valves 77

2.5.3 Rupture Disk Devices 80

2.5.4 Low-Pressure Devices 80

2.5.5 Devices in Series 81

2.5.6 Devices in Parallel 87

2.5.7 Header Systems 88

2.5.8 Mechanical Integrity 88

2.5.9 Material Selection 88

2.5.10 Drainage and Freeze-up Provisions 89

2.5.11 Noise 89

2.6 Design Flows and Code Provisions 90

2.6.1 Safety Valves 92

2.6.2 Incompressible Liquid Flow 95

2.6.3 Low Pressure Devices 95

2.6.4 Rupture Disk Devices 95

2.6.5 Devices in Combination 99

2.6.6 Miscellaneous Nonreclosing Devices 100

2.7 Scenario Selection Considerations 100

2.7.1 Events Requiring Relief Due to Overpressure 101

2.7.2 Design Scenarios 102

2.8 Fluid Properties and System Characterization 104

2.8.1 Property Data Sources/Determination/Estimation 105

2.8.2 Pure-Component Properties 105

2.8.3 Mixture Properties 106

2.8.4 Phase Behavior 106

2.8.5 Chemical Reaction 108

2.8.6 Miscellaneous Fluid Characteristics 112

2.9 Fluid Behavior in Vessel 113

2.9.1 Accounting for Chemical Reactions 113

2.9.2 Two-Phase Venting Conditions and Effects 114

2.10 Flow of Fluids through Relief Systems 116

2.10.1 Conditions for Two-Phase Flow 116

2.10.2 Nature of Compressible Flow 117

2.10.3 Stagnation Pressure and Non-recoverable Pressure Loss 121

2.10.4 Flow Rate to Effluent Handling System 121

2.11 Relief System Reliability 122

2.11.1 Relief Device Reliability 122

2.11.2 System Reliability 125

Requirements for Relief System Design 131

3.1 Introduction 131

3.1.1 Required Background 132

3.2 Vessel Venting Background 133

3.2.1 General Considerations 133

3.2.2 Schematics and Principle Variables, Properties and Parameters 135

3.2.3 Basic Mass and Energy Balances 140

3.2.4 Physical and Thermodynamic Properties 148

3.2.5 Energy Input or Output 153

3.2.6 Solution Methods Using Computer Tools 156

3.2.7 Mass and Energy Balance Simplifications 156

3.2.8 Limiting Cases 158

3.2.9 Vapor/Liquid Disengagement 160

3.3 Venting Requirements for Nonreacting Cases 171

3.3.1 Heating or Cooling of a Constant Volume Vessel 171

3.3.2 Excess Inflow/Outflow 187

3.3.3 Additional Techniques and Considerations 190

3.4 Calorimetry for Emergency Relief System Design 190

3.4.1 Executive Summary 190

3.4.2 Runaway Reaction Effects 191

3.4.3 Reaction Basics 192

3.4.4 Reaction Screening and Chemistry Identification 196

3.4.5 Measuring Reaction Rates 197

3.4.6 Experimental Test Design 222

3.4.7 Calorimetry Data Interpretation and Analysis 234

3.5 Venting Requirements for Reactive Cases 259

3.5.1 Executive Summary 259

3.5.2 Overview of Reactive Relief Load 260

3.5.3 Analytical Methods 267

3.5.4 Dynamic Computer Modeling 279

3.5.5 Closing Comment 282

Methods for Relief System Design 283

4.1 Introduction 283

4.1.1 Relief System Sizing Computational Strategy and Tools for Relief Design 283

4.2 Manual and Spreadsheet Methods for Relief Valve Sizing 285

4.2.1 Relief Valve Sizing Fundamental Equations 285

4.2.2 Two-Phase Flow Methods 298

4.2.3 Relief Valve Sizing - Discharge Coefficient 310

4.2.4 Relief Valve Sizing - Choking in Nozzle and Valve Exit 314

4.3 Miscellaneous 317

4.3.1 Low-Pressure Devices - Liquid Flow 317

4.3.2 Low-Pressure Devices - Gas Flow 318

4.3.3 Low-Pressure Devices - Two-Phase Flow 320

4.3.4 Low-Pressure Devices - Associated Piping 320

4.4 Piping 321

4.4.1 Piping - Fundamental Equations 322

4.4.2 Piping - Pipe Friction Factors 322

4.4.3 Incompressible (Liquid) Flow 328

4.4.4 Piping Adiabatic Compressible Flow 329

4.4.5 Isothermal Compressible Flow 333

4.4.6Homogeneous Two-Phase Pipe Flow 334

4.4.7 Piping - Separated Two-Phase Flows 346

4.4.8 Slip/Holdup 347

4.4.9 Piping - Temperature Effects 348

4.5 Rupture Disk Device Systems 349

4.5.1 Rupture Disks - Nozzle Model 349

4.5.2 Rupture Disks - Pipe Model 349

4.6 Multiple Devices 350

4.6.1 Multiple Devices in Parallel 350

4.6.2 Multiple Devices - Rupture Disk Device Upstream of a PRV 351

4.6.3 Multiple Devices - Rupture Disk Device Downstream of a PRV 351

4.7 Worked Example Index 352

Additional Considerations for Relief System Design 355

5.1 Introduction 355

5.2 Reaction Forces 356

5.3 Background 357

5.4 Selection of Design Case 363

5.5 Design Methods 363

5.5.1 Steady State Exit Force from Flow Discharging to the Atmosphere 363

5.5.2 Dynamic Load Factor 367

5.6 Selection of Design Flow Rate and Dynamic Load Factor 367

5.6.1 Rupture Disks 368

5.6.2 Safety Relief Valves 370

5.7 Transient Forces on Relief Device Discharge Piping 372

5.7.1 Liquid Relief 373

5.7.2 Gas Relief 376

5.7.3 Two-Phase Flow 384

5.8 Pipe Tension 385

5.8.1 Safety Relief Valves 386

5.8.2 Rupture Disks 387

5.9 Real Gases 390

5.10 Changes in Pipe Size 390

5.11 Location of Anchors 390

5.12 Exit Geometry 391

5.13 Worked Examples 392

Handling Emergency Relief Effluents 393

6.1 General Strategy 395

6.2 Basis for Selection of Equipment 399

6.3 Determining if Direct Discharge to Atmosphere is Acceptable 401

6.4 Factors That Influence Selection of Effluent Treatment Systems 403

6.4.1 Physical and Chemical Properties 403

6.4.2 Two-Phase Flow and Foaming 405

6.4.3 Passive or Active Systems 406

6.4.4 Technology Status and Reliability 407

6.4.5 Discharging to a Common Collection System 408

6.4.6 Plant Geography 409

6.4.7 Space Availability 409

6.4.8Turndown 409

6.4.9 Vapor-Liquid Separation 410

6.4.10 Possible Condensation and Vapor-Condensate Hammer 410

6.4.11 Time Availability 411

6.4.12 Capital and Continuing Costs 411

6.5 Methods of Effluent Handling 411

6.5.1Containment 411

6.5.2 Direct Discharge to Atmosphere 415

6.5.3 Vapor-Liquid Separators 415

6.5.4 Quench Tanks 423

6.5.5 Scrubbers (Absorbers) 429

6.5.6 Flares 432

Design Methods for Handling Effluent from Emergency Relief Systems 437

7.1 Design Basis Selection 438

7.2 Total Containment Systems 439

7.2.1 Containment in Original Vessel 439

7.2.2 Containment in External Vessel (Dump Tank or Catch Tank) 440

7.3 Relief Devices, Discharge Piping, and Collection Headers 442

7.3.1 Corrosion 443

7.3.2 Brittle Metal Fracture 444

7.3.3 Deposition 444

7.3.4 Vibration 444

7.3.5 Cleaning 445

7.4 Vapor-Liquid Gravity Separators 445

7.4.1 Separator Inlet Velocity Considerations 450

7.4.2 Horizontal Gravity Separators 451

7.4.3 Vertical Gravity Separators 460

7.4.4 Separator Safety Considerations and Features 463

7.4.5 Separator Vessel Design and Instrumentation 464

7.5 Cyclone Separators 465

7.5.1 Droplet Removal Efficiency 467

7.5.2 Design Procedure 469

7.5.3 Cyclone Separator Sizing Procedure 470

7.5.4 Alternate Cyclone Separator Design Procedure 472

7.5.5 Cyclone Reaction Force 475

7.6 Quench Pools 476

7.6.1 Design Procedure Overview 477

7.6.2 Design Parameter Interrelations 482

7.6.3 Quench Pool Liquid Selection 483

7.6.4 Quench Tank Operating Pressure 484

7.6.5 Quench Pool Heat Balance 485

7.6.6 Quench Pool Dimensions 493

7.6.7 Sparger Design 499

7.6.8 Handling Effluent from Multiple Relief Devices 509

7.6.9 Reverse Flow Problems 509

7.6.10 Vapor-Condensate Hammer 510

7.6.11 Mechanical Design Loads 510

7.6.12 Worked Example Index for Discharge Handling System Design 511

Acronyms and Abbreviations 513

Glossary 517

Nomenclature 529

Appendix A: SuperChems™ for DIERS Lite – Description and Instructions 541

A.1 Scope 541

A.2 Software Functions 543

A.2.1 Source Term Flow Calculation 543

A.2.2 Emergency Relief Requirement Calculations 544

A.2.3 Physical Properties 545

A.2.4 Piping Isometrics 546

A.2.5 Specifying Vessel Designs 546

A.3 Installing and Running SuperChems™ 547

Appendix B: CCFlow, TPHEM and COMFLOW Description and Instructions 549

B.1 Scope 549

B.1.1 Uncertainties 550

B.2 CCFlow Calculation Options 550

B.2.1 Opening and Running CCFlow 552

B.2.2 File Operations 552

B.2.3 Help Files 554

B.2.4 Other Operations 555

B.2.5 CCFlow Input Menu Errata 556

B.3 TPHEM Calculation Options 556

B.3.1 Running TPHEM with File Input 560

B.4 COMFLOW Calculation Options 562

B.4.1 Running COMFLOW 563

Appendix C: SuperChems™ for DIERS – Description and Instructions 565

C.1 Scope 565

C.2 Software Functions 567

C.2.1 Main Menu Tabs 567

C.2.2 Define Tab 568

C.2.3 Dynamic Flow Simulation 570

C.2.4 Steady-State Flow Calculations 571

C.2.5 Properties Tab 572

C.2.6 VLE Tab 574

C.3 Installing and Running SuperChems™ 576

Appendix D: Venting Requirements 577

D.1 Worked Examples – Emergency Venting 579

D.1.1 External Fire – Vapor Venting 580

D.1.2 Tube Rupture 590

D.1.3 Literature Examples for Non-Reactive Cases 596

D.2 Venting Requirements for Reactive Cases 597

D.3 Relief Valve Sizing Examples 599

D.3.1 Incompressible Liquid Flow (with Viscosity Correction) 601

D.3.2 Real Gas Flow 603

D.3.3 Supercritical Fluid Flow 607

D.3.4 Non-Flashing (Frozen) Choked Flow 609

D.3.5 Non-Flashing (Frozen) Non-choked Flow 611

D.3.6 Equilibrium Flow of Single-Component Fluid 614

D.3.7 Non-Equilibrium Flow of Single-Component Fluid 616

D.3.8 Multicomponent Fluid Flow 618

D.3.9 Equilibrium Flow of One-Component Fluid (Low Subcooled Liquid Flow) 621

D.3.10 Equilibrium Flow of Single-Component Fluid (Highly Subcooled Liquid Flow) 626

D.3.11 Single-Component Vapor Flow with Retrograde Condensation 630

D.4 Piping Flow Examples 634

D.4.1 Two-Phase Gas-Liquid Flow with Conventional Multiple Chokes 635

D.4.2 Real Gas Flow with Multiple Chokes 650

D.4.3 Flow of High Viscosity Liquid 654

D.5 Reaction Forces 658

D.5.1 PRV with Viscous Liquid Flow – Steady Forces 658

D.5.2 PRV with Real Gas Flow – Steady Forces 661

D.5.3 RD with Liquid Flow – Steady and Transient Forces 664

D.5.4 RD with Air Flow – Steady and Transient Forces 667

D.5.5 PRV with Steam Flow – Steady and Transient Forces 670

D.5.6 PRV with Two-Phase Flow – Steady and Transient Forces and Piping Design Pressure 673

D.5.7 PRV with Two-Phase Flow – Steady and Transient Forces and Piping Design Pressure 675

D.5.8 RD with Two-Phase Flow – Steady and Transient Forces and Piping Design Pressure 678

Appendix E: Worked Examples – Effluent Handling 681

E.1 Phase Separator and Quench Tank Design Examples 681

E.1.1 Example Problem Statement 682

E.1.2 Given Conditions 683

E.1.3 Quench Pool Design 692

E.1.4 Gravity Separator Design 706

E.1.5 Cyclone Separator Design 710

E.1.6 Summary 715

References 717

Index 743