Table of Contents

Preface. Acknowledgments. Acronyms and Abbreviations. 1. Introduction. 1.1 Objective. 1.2 Scope. 1.3 Design Codes and Regulations, and Sources of Information. 1.4 Organization of This Book. 1.5 General Pressure Relief Systems Design Criteria. 1.5.1 Process Hazards Analysis. 1.5.2 Process Safety Information. 1.5.3 Problems Inherent in Pressure Relief and Effluent Handling System Design. 2. Relief Design Criteria and Strategy. 2.1 Limitations of the Technology. 2.2 General Pressure Relief Strategy. 2.2.1 Mechanism of Pressure Relief. 2.2.2 Approach to Design. 2.2.3 Limitations of Systems Actuated by Pressure. 2.2.4 Considerations of Consequences. 2.3 Codes, Standards, and Guidelines. 2.3.1 Scope of Principal USA Documents. 2.3.2 General Provisions. 2.3.3 Protection by System Design. 2.4 Relief Device Types and Operation. 2.4.1 General Terminology. 2.4.2 Pressure Relief Valves. 2.4.3 Rupture Disk Devices. 2.4.4 Devices in Combination. 2.4.5 Miscellaneous Nonreclosing Devices. 2.4.6 Miscellaneous Low-Pressure Devices. 2.4.7 Miscellaneous Relief System Components. 2.4.8 Selection of Pressure Relief Devices. 2.5 Relief System Layout. 2.5.1 General Code Requirements. 2.5.2 Pressure Relief Valves. 2.5.3 Rupture Disk Devices. 2.5.4 Low-Pressure Devices. 2.5.5 Series/Parallel Devices. 2.5.6 Header System. 2.5.7 Mechanical Integrity. 2.5.8 Material Selection. 2.5.9 Drainage and Freeze-up Provisions. 2.5.10 Noise. 2.6 Design Flows and Code Provisions. 2.6.1 Safety Valves. 2.6.2 Relief Valves. 2.6.3 Low Pressure Devices. 2.6.4 Rupture Disk Devices. 2.6.5 Devices in Combination. 2.6.6 Miscellaneous Nonreclosing Devices. 2.7 Scenario Selection Considerations. 2.7.1 Events Requiring Relief Due to Overpressure. 2.7.2 Design Scenarios. 2.8 Fluid Properties and System Characterization. 2.8.1 Data Sources/Determination/Estimation. 2.8.2 Pure-Component Properties. 2.8.3 Mixture Properties. 2.8.4 Phase Behavior. 2.8.5 Chemical Reaction. 2.8.6 Miscellaneous Fluid Characteristics. 2.9 Fluid Behavior in Vessel. 2.9.1 Accounting for Chemical Reaction. 2.9.2 Two-Phase Venting Conditions and Effects. 2.10 Flow to Fluids through Relief Systems. 2.10.1 Conditions for Two-Phase Flow. 2.10.2 Nature of Compressible Flow. 2.10.3 Stagnation Pressure and Critical Pressure Ratio. 2.10.4 Flow Rate to Effluent Handling System. 2.11 Relief System Reliability. 2.11.1 Relief Device Reliability. 2.11.2 System Reliability. Appendix 2A. International Codes and Standards. Appendix 2B. Property Mixing Rules. Appendix 2C. Code Case: Protection by System Design. 3. Relief System Design and Rating Computations. 3.1 Introduction. 3.1.1 Purpose and Scope. 3.1.2 Required Background. 3.2 Vessel Venting Background. 3.2.1 General. 3.2.2 material and Energy Balances. 3.2.3 Phase Behavior. 3.2.4 Two-Phase Venting Technology. 3.2.5 Methods of Solution. 3.3 Venting Requirements for Nonreacting Cases. 3.3.1 Thermal Expansion. 3.3.2 Fire Exposure. 3.3.3 Loss of Heating/Cooling Control. 3.3.4 Excess Inflow/Outflow. 3.3.5 Structural Failure. 3.3.6 Loss of Agitation. 3.3.7 Miscellaneous. 3.4 Vent Rate for Reacting Systems. 3.4.1 General. 3.4.2 Computer Simulations. 3.4.3 Special-Case Integral Equations. 3.5 Computational Strategy and Tools for Relief Flow. 3.5.1 Gas/Vapor Flow. 3.5.2 Two-Phase Flow. 3.5.3 Nozzle and Piping Configuration for COMFLOW and TPHEM. 3.6 Relief System Sizing and Rating. 3.6.1 Pipe Runs. 3.6.2 Safety Relief Valve Systems. 3.6.3 Liquid Relief Valve Systems. 3.6.4 Miscellaneous Low-Pressure Devices. 3.6.5 Rupture Disk Device Systems. 3.6.6 Devices in Combination. 3.6.7 Miscellaneous System Elements. 3.6.8 Header Systems. 3.7 Reaction Forces/Thrust. 3.7.1 Background Theory. 3.7.2 Selection of Design case. 3.7.3 Design Methods. Appendix 3A. Vessel Venting Technology and Data Acquisition. 3A.1 System Schematic and Principal Parameters. 3A.2 Basic Material and Energy Balances. 3A.2.1 Vent Rate Criterion. 3A.2.2 Energy and Material Balance. 3A.3 Phase Behavior. 3A.3.1 General-Case Phase Equilibrium. 3A.3.2 Component Classification. 3A.3.3 Nonequilibrium Phenomena. 3A.4 Two-Phase Venting Technology. 3A.4.1 Coupling Equation. 3A.4.2 Holdup Correlations. 3A.4.3 Tests for Two-Phase Venting. 3A.5 Pressure Rise from Thermal Expansion. 3A.6 Runaway Reaction Calorimeters. 3A.6.1 Device Characteristics. 3A.6.2 Data Interpretation. 3A.7 Relief Rate by Computer Simulation. 3A.7.1 Fire Exposure. 3A.7.2 Runaway Reaction. Appendix 3B. Relief System Sizing Background. 3B.1 Scope. 3B.2 Fluid Flow fundamentals. 3B.2.1 Flow in Nozzles. 3B.2.2 Pipe and Fittings. 3B.2.3 Conditions at Maximum Flow. 3B.3 Physical Property Treatment. 3B.3.1 Input to TPHEM. 3B.3.2 Relationships for Analytical Integration. 3B.4 Computation Strategies. 3B.4.1 Numerical Integration. 3B.4.2 Analytical Integrals for Homogeneous Flow. 3B.4.3 Computer Programs. Appendix 3C. Example System Rating Simulation. 3C.1 Fire Exposure Example. 3C.2 Runaway Reaction Example. Appendix 3D. Final Device Specs Required for Purchase. 4. Selection of Equipment for Handling Emergency Relief Effluent. 4.1 General Strategy. 4.2 Basis for Selection of Equipment. 4.3 Determining What May Be Discharged to the Atmosphere Safely. 4.4 Factors that Influence Selection of Effluent Treatment Systems. 4.4.1 Physical and Chemical Properties. 4.4.2 Two-Phase Flow and Foaming. 4.4.3 Passive versus Active Systems. 4.4.4 Technology Status and Reliability. 4.4.5 Discharging to a Common collection System. 4.4.6 Plant Geography. 4.4.7 Space Availability. 4.4.8 Turndown. 4.4.9 Need for Vapor-Liquid Separation. 4.4.10 Possible Condensation and Steam-water Hammer. 4.4.11 Time Availability. 4.4.12 Capital and Continuing Costs. 4.5 Methods of Effluent Handling. 4.5.1 Containment. 4.5.2 Discharge to Atmosphere. 4.5.3 Vapor-Liquid Separators. 4.5.4 Quench Pools. 4.5.5 Scrubbers (Absorbers). 4.5.6 Flares. 5. Design Methods for Handling Effluent from Emergency Relief Systems. 5.1 Design Basis Selection. 5.2 Total Containment Systems. 5.2.1 Containment in Original Vessel. 5.2.2 Containment in External Vessel (Dump Tank or Catch Tank). 5.3 Relief Devices, Discharge Piping, and Collection Headers. 5.3.1 Limitations on Combining Multiple Relief Discharges into Common Headers. 5.3.2 Pressure Drop Guidelines. 5.3.3 Discharge Piping Design Pressure. 5.3.4 Materials of Construction. 5.3.5 Location of Relief Devices. 5.3.6 Mechanical Design. 5.3.7 Separation of Headers Based on Temperature and Pressure. 5.4 Vapor-Liquid Gravity Separators. 5.4.1 Separator Inlet Velocity Considerations. 5.4.2 Horizontal Gravity-Type Separators. 5.4.3 Vertical Gravity Separators. 5.4.4 Separator Safety Considerations and Features. 5.4.5 Separator Vessel Design and Instrumentation. 5.5 Cyclones. 5.5.1 Droplet Removal Efficiency. 5.5.2 Design Procedure. 5.5.3 Cyclone Separator Sizing Procedure. 5.6 Quench Pools. 5.6.1 Design Procedure Overview. 5.6.2 Design Parameter Interrelations. 5.6.3 Quench Pool Liquid Selection. 5.6.4 Quench Tank Operating Pressure. 5.6.5 Quench Pool Heat Balance. 5.6.6 Quench Pool Dimensions. 5.6.7 Sparger Design. 5.6.8 Handling Effluent from Multiple Relief Devices. 5.6.9 Reverse Flow Problems. 5.6.10 Steam/Water Hammer. 5.6.11 Mechanical Design Loads. 5.6.12 Quench Tank with Effluent Scrubber. 5.7 Scrubbers (Absorbers). 5.7.1 General Comments and Background. 5.7.2 Special Requirements for Emergency Scrubbers. 5.7.3 Scrubbing (Absorption) Mechanisms Considerations. 5.7.4 Scrubbers Design Methodology. 5.7.5 Mechanical Design Considerations. 5.8 Release to Atmosphere. 5.8.1 Stack Location and Elevation. 5.8.2 General Design Considerations. 5.8.3 Dispersion Criteria and Stack Diameter. 5.8.4 Noise and Velocity Limitations. 5.9 Flare Systems. 5.9.1 General Comments and Considerations. 5.9.2 EPA Requirements. 5.9.3 Elevated Flare System Design Criteria. 5.9.4 Safety, Blockage, and Freeze-Up Issues. 5.9.5 Materials of Construction. Appendix 5A. 5A.1 Examples Problem. 5A.2 Given Conditions. 5A.3 Quench Pool Design. 5A.3.1 Heat Balance. 5A.3.2 Sizing the Quench Pool Vessel. 5A.3.3 Sizing the Sparger. 5A.3.4 Size Manifold and Distributor. 5A.4 Gravity Separator Design. 5A.4.1 Piping Size. 5A.4.2 Horizontal Separator Design. 5A.4.3 Vertical Separator Design. 5A.5 Cyclone Separator Design. Summary. References. Glossary. Index.

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The CENTER FOR CHEMICAL PROCESS SAFETY (CCPS), an industry technology alliance of the American Institute of Chemical Engineers (AIChE), has been a world leader in developing and disseminatinginformation on process safety management and technology since 1985. CCPS has published over 80 books in its process safety guidelines and process safety concepts series. For more information, visit www.ccpsonline.org.