Safety Valves in Oil and Gas Plants

Karan Sotoodeh is a valve and actuator Senior Engineer at Baker Hughes in Oslo, Norway with close to two decades of experience in the oil and gas industry. He has been selected to speak at international conferences in the USA, Germany, and China on subjects including valves, piping, actuators, and material engineering. He has written 15 books and published more than 50 papers in peer-reviewed journals.

• Preface ix1 Basic Safety Valves Principles 11.1 Introduction and History 11.2 Maximum Allowable Working Pressure (MAWP) 21.3 The Importance of Safety Valves and Safety Devices 31.4 Overpressure Scenarios and Examples in the Plant 51.4.1 Closed Outlet of a Vessel 51.4.2 Unintentional Valve Opening 61.4.3 Check Valve Leakage or Failure 61.4.4 Utility Failure 61.4.5 Heat Exchanger Tube Failure 71.4.6 Transient Pressure Surges 71.4.7 Process Change/Chemical Reaction 81.4.8 Summary and Case Studies 81.5 Variations in Safety/Relief Valves 131.6 Safety Valve Parts 211.7 Safety Valve Dismantling 221.8 Basic Safety Valve Operation 231.9 Safety Valve Essential Pressure Settings 24Questions and Answers 25Further Reading 322 Design Fundamentals 332.1 Introduction 332.2 Spring Force 342.3 Back Pressure Consideration 352.3.1 Cold Differential Test Pressure 372.3.2 Superimposed and Dynamic (Buildup) Back Pressures 392.3.3 Back Pressure Handling and Safety Valve Selection 432.4 Overpressure and Blowdown 452.4.1 Safety Valve Functioning Curves 462.5 The Relationship Between the Pressure Values of Safety Valves and Pressure Vessels 492.6 Set Pressure Determination 522.7 Actual Discharge Area Calculation 552.8 Simmer 572.9 Pressure Loss in Inlet Piping 58Questions and Answers 62Further Reading 683 Safety Valves Features and Accessories 713.1 Introduction 713.2 Full Nozzle vs Seminozzle 723.2.1 Full-Nozzle Design 723.2.2 Seminozzle Design 753.3 Open vs Closed Bonnet 763.3.1 Open Bonnet Design 763.3.2 Closed Bonnet Design 773.4 Metal Seat vs Soft Seat 773.4.1 Metal Seat 773.4.2 Soft Seat 783.5 Bellows Seal 813.5.1 Bellows Effects 813.5.2 Bellows Failure Mechanisms 833.5.3 Bellows Failure (Leakage) Handling 853.5.4 Bellows Material Selection 883.5.5 Bellows Testing 893.6 Lifting Lever 923.7 Single vs Dual Trim 943.8 Wires 953.9 Test Gag 953.10 Low-Lift, High-Lift, and Full-Lift Disk 983.11 Balanced Piston 993.12 Cooling/Heating Spacer 1003.13 Limit Switch (Position Indicator) 1003.14 Pneumatic Actuator 1003.15 Stroke Sensor 1013.16 Pulsation Damper 1023.17 Drain Hole 1023.18 Teflon Lining and Coating 1023.19 Stellite Coating on Seating Surfaces 103Questions and Answers 104Further Reading 1134 Safety Valves Codes and Standards 1154.1 Introduction 1154.2 American Society of Mechanical Engineers (ASME) 1164.3 American Petroleum Institute (API) 1204.3.1 API Recommended Practice 520 Part 1: Sizing and Selection 1214.3.2 API Recommended Practice 520 Part 2: Installation 1234.3.3 API Recommended Practice 521 Pressure-Relieving and Depressuring Systems 1244.3.4 API Recommended Practice 526 Flanged Steel Relief Valves 1244.3.5 API Recommended Practice 527 Seat Tightness of Pressure-Relief Valves 1244.3.6 API 576 Inspection of Pressure-Relieving Devices 1254.4 International Organization for Standardization (ISO) 1254.5 British Standards 1274.6 Australian Standard 1284.7 Canadian Standard 1294.8 Other Standards 1294.9 National Association of Corrosion Engineers (NACE) 1294.10 Pressure Equipment Directive (PED) 1304.11 Approval Authorities 131Questions and Answers 132Further Reading 1375 Safety Valves Installation 1415.1 Introduction 1415.2 Prior to Installation 1415.3 Location and Position 1425.3.1 Distance to Pressure Source 1435.3.2 Distance to Other Equipment 1445.3.3 Inspection and Maintenance 1455.4 Piping Connection 1455.4.1 Inlet Piping 1465.4.2 Inlet Valves 1545.4.3 Outlet Piping 1605.4.4 Outlet Valves 1635.4.5 Piping Pressure Loss Calculations 166Questions and Answers 175Further Reading 1846 Safety Valve Reaction Forces 1876.1 Introduction 1876.2 Calculations 187Questions and Answers 201Further Reading 2037 Safety Valve Sizing 2057.1 Introduction 2057.2 Sizing for Gas or Vapor Relief 2117.2.1 Critical Flow 2117.2.2 Subcritical Flow 2237.3 Sizing for Steam Relief 2257.4 Sizing for Liquid Relief 2297.4.1 Sizing for Liquid Relief With Capacity Certification 2297.4.2 Sizing for Liquid Relief Without Capacity Certification 2347.5 Sizing for Two-Phase Liquid/Vapor Relief 2357.6 Sizing for Saturated Liquid and Saturated Vapor, Liquid Flashes 2387.7 Sizing for Subcooled at the Pressure-Relief Valve Inlet 2427.8 Sizing for Fire Case and Hydraulic Expansion 2447.8.1 Hydraulic Expansion (Thermal Expansion) 2467.8.2 Sizing Safety Valve for the Fire Case 247Questions and Answers 254Further Reading 256Index 259